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Effect of the number of concentrate feeding places per pen on performance, behavior, and welfare indicators of Friesian calves during the first month after arrival at the feedlot¹

L. A. González^*,,2, A. Ferret^*,,3, X. Manteca^*,, J. L. Ruíz-de-la-Torre^*,, S. Calsamiglia^*,, M. Devant^, and A. Bach^,,

^* Departament de Ciència Animal i dels Aliments, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain; and Unitat de Remugants-IRTA, 08140 Caldes de Montbui, and and ICREA, Barcelona, Spain; and Animal Nutrition, Management, and Welfare Research Group, Barcelona, Spain

	Abstract

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Seventy-two Friesian calves (BW = 102.0 ± 1.8 kg) were bought from a commercial calf farm and distributed to a factorial arrangement of treatments in a complete block design with 3 treatments and 3 blocks of similar fasted BW to study the effect of increasing the number of feeding places per pen on performance, behavior, and welfare indicators during the 4 wk after arrival. Treatments consisted of 1 (T1), 2 (T2), or 4 (T4) concentrate feeding places/pen (8 calves/pen). Concentrate and straw were fed at 0830 in individual feeders, and animals were allowed to consume on an ad libitum basis. Dry matter intake and ADG were recorded weekly, and blood samples were taken on d 0 (before transport), 7, 14, 21, and 28. Time spent in maintenance activities, number of displacements between calves, and the angular dominance value (ADV) were registered at wk 1 and 3 after arrival. Increasing the number of feeding places per pen resulted in a quadratic response of concentrate and total DMI, ADG, and BW during the 28-d period, with T1 showing the lowest values. Straw intake and the within-pen SD of ADG tended to decrease linearly (P = 0.10) as the number of feeding places per pen increased. During the 4-wk receiving period, and particularly on d 7 after arrival, serum NEFA responded quadratically, with T1 and T2 calves showing the greatest values. With increasing number of concentrate feeders, the average time spent lying increased (P = 0.001), standing time decreased linearly (P = 0.001), and the diurnal feeding pattern changed (concentrate eating time increased but straw eating time decreased during peak feeding times, P < 0.05). The number of displacements from the concentrate feeders responded quadratically (P < 0.001) with increasing number of feeding places per pen, with T4 calves showing the lowest levels of aggression. In T1 calves, increasing ADV resulted in a linear decrease (P = 0.03) of ADG at wk 1 with a quadratic effect at wk 3 (P < 0.01). In T2 calves, increasing ADV resulted in a linear decrease (P = 0.04) of ADG at wk 1 but a linear increase (P = 0.02) at wk 3. No effect of social rank on ADG was observed in T4 calves (P > 0.20). Increasing social pressure at the concentrate feeders beyond the threshold of 4 heifers per feeder had a negative effect on performance. Within-pen variability in performance increased linearly as a consequence of greater effects of social dominance. Physiological indicators of welfare were not consistently affected by treatments.

Key Words: behavior • calf • feeding place • performance • welfare

	INTRODUCTION

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Calves start the intensive fattening period after weaning at different ages and with different physical, behavioral, and physiological conditions depending on the production system of origin. At the time of weaning, marketing, and reallocation to new facilities, calves are exposed to stress, which may be detrimental for animal welfare (Gonyou, 1986; Grandin, 1997) and negatively affect performance and immune response (Galyean et al., 1999). The quantity and quality of resources should be optimized to reduce stress and facilitate adaptation. Many studies have investigated effects of nutrition during the arrival period, as reviewed by Galyean et al. (1999). Nevertheless, the effect of factors related to behavior, social stress, or the design of facilities has not received considerable attention during this critical period. Social stress is mainly a consequence of the rupture of social bonds, mixing of animals, and establishment of a new social hierarchy. This process is an important consideration for management (Kondo et al., 1984), and an inadequate design of facilities may negatively affect adaptation of stressed calves. Accordingly, sufficient availability of feeding space may provide uniform opportunities of access to feed among calves facing this process. Gonyou and Stricklin (1981) stated that growth of beef cattle was negatively affected during the initial 2 wk while adapting to limited feeding space. The reduction of feeding space has increased aggression (Huzzey et al., 2006), which may result from the individual’s pressure in a group to earn a social rank that allows them priority to access resources (Syme, 1974). The aim of the current study was to investigate effects of increased social pressure caused by a reduced number of concentrate feeding places on performance, behavior, and welfare indicators of newly received feedlot calves.

	MATERIALS AND METHODS

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Animals, Treatments, and Facilities

All animal care protocols were approved by the Institut de Recerca i Tecnologia Agroalimentaries Animal Care and Use Committee.

Seventy-two female Friesian calves (104.3 ± 1.1 d of age, 102.0 ± 1.8 kg of fasted BW) were purchased after weaning from a commercial farm and transported to the IRTA-PRAT Experimental Farm (Barcelona, Spain) at 1500. A factorial arrangement of treatments in a randomized complete block design with 3 treatments and 3 BW blocks was used. Calves were first distributed into 3 blocks of homogeneous 24-h fasted BW. They were then assigned to subgroups of 3 calves with similar BW, and each calf was randomly assigned to 1 of the 3 treatment pens (8 calves/pen) within a BW. Treatments consisted of 1 (T1), 2 (T2), or 4 (T4) feeding places/pen. Thus, the number of heifers per concentrate feeder was 8, 4, and 2 for T1, T2, and T4, respectively.

Each pen had a concrete floor and was 12.6 m long and 3.84 m wide (48.4 m²/pen), which resulted in a space availability of 6.05 m²/calf. Each pen had an 11.1-m², concrete-roofed resting area bedded with wood shavings at one end and a 7.7-m² feeding area with a 2.5-m ceiling at the other end. Feeders were manufactured in steel bodies that were 1 m long, 0.40 m deep (elevated at 0.15 m from the floor), and 1.29 m tall, with a capacity of 200 L. The front of each steel body contained 1 or 2 feeding places with feed barriers (Figure 1). Therefore, only 1 feeder with 1 feeding place was set in each T1 pen, 1 feeder with 2 feeding places was set in T2 pens, and 2 feeders with 2 feeding places each were set in the T4 pens. The distance between the center points of 2 consecutive feeding places was 0.45 m. The front of the feeders had an opening for the calf’s neck, with a throat height of 0.50 m, and was 0.15 m wide, which allowed only one calf to eat from each feeding place at any one time. The concentrate feeders were allocated in the front of the 3.84-m wide feeding area, and one straw feeder was placed at each side of the concentrate feeders. Thus, the linear space available in the straw feeders was 0.34 m/calf in each T1 and T2 pen and 0.20 m/calf in the T4 pens. Concrete feeders (0.5 m at throat height) were beneath the straw feeders (1-m throat height) to avoid straw losses. One water bowl was placed at each corner of the feeding area.

View larger version (42K): [in this window] [in a new window]   Figure 1. Design and measures of the concentrate feeder used in the experiment. One steel body was placed in pens with 2 concentrate feeding places and 2 identical bodies were set in each pen with 4 concentrate feeding places. A similar feeder was placed in pens with 1 concentrate feeding place, which had the same dimensions but contained only one opening for the calves’ heads.

Intake and Performance

All animals received a commercial concentrate (Table 1), formulated according to the NRC (1996) recommendations, and barley straw (90.7% DM, 6.72% ash, 73.45% NDF, 43.77% ADF, 8.69% ADL, 4.84% CP, on a DM basis). Feeding management allowed ad libitum consumption of both components, which were offered once a day at 0830. Fresh water was available at all times. One composited sample of the offered concentrate and straw was taken weekly for DM determination and chemical analysis. Another sample of refusals from each pen was taken at d 7, 14, 21, and 28 for DM determination. Straw and concentrate intake was calculated for each week by weighing the amount of feed offered each day and subtracting the amount refused at the end of the week. All calves were weighed after withdrawal of refusals on d 1 (after distribution), 7, 14, 21, and 28 at 0830 for the weekly calculation of ADG and G:F. To assess the variability of growth between calves sharing the same pen, the within-pen SD was calculated at each time point and analyzed statistically.

Two whole blood samples from each calf were taken at 0830 by jugular venipuncture before transportation to the experimental farm (d 0), and then on d 7, 14, 21, and 28. Serum was separated within 4 h (3,000 x g, 20 min, 4°C) from a blood sample (10-mL Vacutainer with no additives, BD Becton Dickinson UK Limited, Oxford, UK) and stored at –20°C until analyses of haptoglobin, β-hydroxy butyrate (β-HBT), and NEFA. A second un-clotted blood sample (5-mL Vacutainer with EDTA, BD Becton Dickinson UK Limited) was immediately stored at 4°C until differential cell counts were determined. Fecal samples were taken from the rectum of each calf at the same time as bleeding and kept on ice until frozen within 3 h at –20°C for later analyses of glucocorticoid metabolites (GM) to assess the stress level of calves.

Maintenance Behavior

Behavior of animals was recorded for 24 h on d 2, 3, and 4 (wk 1), and d 16 and 17 (wk 3). Videos were processed by continuous recording of the activities performed by all animals. Recorded activities (time spent eating concentrate and straw, drinking, lying, and standing) were registered simultaneously with their beginning and ending times (to the nearest second), and the animal’s identification. Several digital photographs of each calf were taken from different angles during the experiment to identify them on video by the distribution of the white and black patches on their bodies. Eating was defined as when the animal had its head into the feeder and was engaged in chewing. Eating rate of concentrate and straw were calculated as the mean daily DMI of the pen divided by the corresponding mean total time spent eating by all animals in the pen. Drinking was recorded when the animal had its mouth in the water bowl. Lying was recorded as soon as the animal was not standing on its 4 legs, independently of any activity the animal might perform. Time spent standing was calculated as the total duration of the observation period minus the time spent eating concentrate or straw, drinking, and lying. The effect of the number of feeding places per pen on feeding patterns throughout the day was analyzed by dividing the day into twenty-four 1-h intervals.

Social Behavior

Displacements among calves from concentrate feeders, straw feeders, and water bowls were the events recorded. Displacements were counted at the time of occurrence, and the animal’s identification, the type of event, and the activity being performed when the event occurred were recorded. A displacement occurred when one of the animals ("actor") displaced a pen mate ("reactor") that was eating or drinking and caused the reactor to completely remove its head from the container and quit the activity being performed. Displacements were further subdivided into displacements with nonphysical and physical contact. However, displacements with nonphysical contact constituted less than 6% of the total number of displacements and were not considered separately in any further analysis. Winner-loser relationships were not recorded when eating or drinking was not being performed by one of the animals involved and when the aggression did not result in the physical withdrawal of the individual from the container. These unsuccessful displacements were not considered because at some times it was not known whether a calf immediately behind or beside the calf occupying the feeder was attempting to displace it, or instead was waiting for the feeder to be free. In addition, waiting calves changed positions quickly, and displacements among them very often occurred even without the calf occupying the feeder being displaced, especially in T1 pens. Finally, there was no clear cut-off point with regard to length of time waiting, time between 2 successive attempts, or how far the waiting calf moved from the feeder and then returned to be able to count it as a new failed or lost displacement. Hierarchy matrices were constructed (28 total cells or possible pairs) for each pen in each week. Dominance order was assessed by calculating the angular dominance value (ADV) as the arcsine square root transformation of the average proportion of times that the individual displaced to each pen mate (Beilharz and Zeeb, 1982):

where x is the number of times that calf i displaced calf j; y is the number of times that calf i was displaced by calf j; and N is the number of calves that showed interactions with i. Therefore, the smaller the ADV, the lower the animal’s social rank.

Chemical Analyses

Dry matter content of offered feed and refusals was determined by drying samples for 24 h at 103°C in a forced-air oven according to the AOAC (1990). A composite sample of offered concentrate and straw were collected for each 2-wk period, mixed, and dried in a forced-air oven at 65°C for 48 h for later chemical analysis. Feeds were ground in a hammer mill through a 1-mm screen and retained for analysis of DM (24 h at 103°C) and ash (4 h at 550°C). Organic matter was calculated as the difference between DM (AOAC, 1990; ID 950.01) and ash content (AOAC, 1990; ID 950.05). Nitrogen content was determined by the Kjeldahl procedure (AOAC, 1990; ID 976.05). Ether extract was performed according to the AOAC (1990; ID 920.39). The NDF and ADF contents were determined sequentially, following the procedure of Van Soest et al. (1991) using a thermostable -amylase (Alpha-amylase FAA Ancon, Macedon, NY) and sodium sulphite.

Fecal GM determinations were performed in the Clinical Biochemistry Service of the Veterinary Faculty of the Universitat Autònoma de Barcelona, using the commercially available ¹²⁵I RIA kit (Rats and Mice Corticosterone kit, ICN Pharmaceuticals, Orangeburg, NY), as described by Morrow et al. (2002). Fecal samples were first lyophilized, then were extracted with methanol, and finally were diluted 1:10 with the assay buffer of the kit. The intra- and interassay CV of the RIA were 12.2 and 15.6%, respectively. The estimated detection limit of GM in feces was 5.7 ng/g of DM. Haptoglobin was determined by the hemoglobin binding method with the use of a commercial haptoglobin assay (intra-and interassay CV of 1.4 and 6.9%, respectively; Assay Phase Range, Tridelta Development Limited, Maynooth, Ireland); D-3-Hydroxybutyrate was determined by a kinetic enzymatic method (both intra- and in-terassay CV of 3.7%; Ranbut D-3-Hydroxybutyrate, Randox Laboratories Ltd., Crumlin, UK) and NEFA by the colorimetric enzymatic test ACS-ACOD method (both intra- and interassay CV of 2.7%; NEFA C, Wako Chemicals, Neuss, Germany). Differential cell counts were carried out using an automated electronic cell counter (ADVIA 120, Bayer, New York, NY).

Statistical Analyses

All individual data were averaged to give pen means at each sampling point over time, except for the regressions on ADV. The pen was the experimental unit for all statistical analyses (n = 3 pens/treatment). All variables expressed in percentages were previously transformed by the square root arcsine. Total white blood cells (WBC) count, fecal GM concentration, and haptoglobin concentration were logarithmically transformed to normalize the distribution. Statistical analyses of normally distributed variables were conducted by a mixed-effects regression model for a randomized complete block design with repeated measures using PROC MIXED (SAS Inst. Inc., Cary, NC). The model contained the fixed linear and quadratic effects of the number of feeding places per pen (treatment), block, and treatment x week, and block x week interactions. The random effects were modeled through the correlations among the repeated measure of time (day, week, or time interval) subjected to the pen, and through the random effect of pen. To analyze the eating patterns within the day and among weeks, double-repeated measures were considered. Thus, the time interval of the day was subjected to the week nested within pen. In the case of a significant treatment x time interaction, the null hypothesis tested was that the linear and quadratic coefficients of regression of the number of feeding places per pen were equal to zero. The same effects were used in a Poisson regression model to analyze the number of displacements per pen and day using the GLIMMIX procedure of SAS. To assess linear and quadratic relationships between ADV and ADG, the correlations were modeled at 3 levels of random effects. The 3 levels were individual animal nested within the pen, repeated measures over time, and pen (with all animals within a pen being correlated). This model contained the fixed categorical effects of treatment, week, and block plus the linear and quadratic effect of ADV and the appropriate 2- and 3-way interactions. The choice of the best covariance structure was based on fit statistics (Littell et al., 1998). Significance was declared at P 0.05, and tendencies were discussed at P 0.10, unless otherwise noted.

	RESULTS

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Two calves died on d 1 of the experiment, one of which was in the T1 group and the other in the T4. In order to balance the experiment, one calf from each treatment in the low BW block was immediately replaced. During the first week of arrival, one heifer from T4 suffered a leg injury and was treated with the recommended antibiotics and analgesics. Its blood haptoglobin level was greatly increased at the d 7 sample, and it was not considered until it returned to normal levels at d 14.

Intake and Performance

Concentrate and total DMI responded quadratically as the number of feeding places per pen increased (P 0.01; Table 2) with a threshold value of 2 feeding places per pen (T2), above which no positive effect was observed. However, straw DMI showed a tendency for a linear decrease as the number of feeding places increased (P = 0.10). Concentrate, straw, and total DMI were lowest at wk 1 (P < 0.05) and increased over time, but the proportion of straw eaten was greatest during wk 1 (P < 0.01; data not shown). A week x treatment interaction was observed for concentrate DMI (P < 0.001) and for the proportion of straw consumed (P = 0.01). Increasing the number of feeding places per pen increased linearly the concentrate DMI during the first week after arrival (P < 0.05; Figure 2a). However, the effect was quadratic during wk 2, 3, and 4 with the lowest concentrate intake for T1 calves (P < 0.05). Straw DMI decreased linearly during wk 2 and 3 as the number of feeding places per pen increased (P < 0.05), but no treatment effect was observed during wk 1 (data not shown).

View larger version (11K): [in this window] [in a new window]   Figure 2. (a) Concentrate DMI, and (b) ADG of calves throughout the 4-wk receiving period in pens with 1 (T1), 2 (T2), or 4 (T4) concentrate feeding places (8 calves/pen). L,QWithin a week, linear (L) or quadratic (Q) coefficients of regression of the number of feeding places was significant (P < 0.05).

Physiology

Fecal GM concentration was not affected (P 0.54) by the number of feeding places per pen (Table 3). Increasing the number of feeding places per pen resulted in a linear decrease in serum haptoglobin concentration (P = 0.02), but NEFA levels were affected quadratically with the lowest values in T4 calves (P = 0.04; Table 3). Treatments did not affect mean β-HBT or leukocytes. However, hematocrit percentage followed a quadratic tendency with high percentages in T1 and T2 (P = 0.08). A day after arrival x treatment interaction was detected (P < 0.05) for NEFA and β-HBT. Nonesterified fatty acids increased quadratically on d 7 and 21 with T1 and T2 calves showing the greatest levels (P < 0.05), but the effect was linear on d 14 (Figure 3; P < 0.05). A quadratic effect on β-HBT was observed on d 7 when T1 calves had the greatest concentration (P < 0.05; data not shown).

View larger version (12K): [in this window] [in a new window]   Figure 3. Serum concentration of NEFA of calves in pens with 1 (T1), 2 (T2), or 4 (T4) concentrate feeding places (8 calves/pen) on d 0 (before transport), 7, 14, 21, and 28 after arrival at the feedlot. L,QWithin a sampling day, linear (L) or quadratic (Q) coefficients of regression of the number of feeding places was significant (P < 0.05).

Maintenance Behavior

As the number of feeding places per pen increased, the time spent using the concentrate feeders increased quadratically, reflecting the greater concentrate intake in T2 and T4 (P = 0.03). The treatment x week interaction (P < 0.01) indicated that the quadratic coefficient of regression of the number of feeding places was significant in wk 3 only (P = 0.005; data not shown). However, time spent at the concentrate feeders increased linearly at wk 1 (P < 0.05), reflecting the increase in concentrate DMI and ADG as the number of feeding places per pen increased. The intrapen SD of the time spent using the concentrate feeders and at the straw feeders decreased linearly as the number of feeding places per pen increased (P = 0.05; Table 4). In agreement with the linear decrease in straw intake, time spent at the straw feeders decreased linearly as number of feeding places increased (P = 0.02). A treatment x week interaction was not observed in time spent in the straw feeders (P > 0.10). Daily patterns of time spent eating concentrate for wk 1 and 3 are shown in Figures 4a and 4b, respectively (treatment x week x hour, P < 0.05), whereas the mean pattern of time at the straw feeders is shown in Figure 4c because they did not differ between weeks (treatment x week x hour, P > 0.10; treatment x hour, P < 0.05). There were 2 major periods of concentrate feeder use, one after sunrise and another around sunset, and one minor period at midnight. In general, as the number of feeding places per pen increased, the time spent using the concentrate feeders increased at peak times during both weeks. However, quadratic effects of treatments were observed before and after the morning eating period during wk 3, when T2 calves spent more time eating concentrate. Contrarily, the time spent at the straw feeders decreased during and between both major periods of eating as the number of concentrate feeding places per pen increased. In contrast to the concentrate eating pattern, a minor period of time eating straw at midnight was not observed. Time spent drinking was not affected by treatments (Table 4). Total time spent lying increased linearly (P = 0.001), whereas that spent in other standing activities decreased linearly when increasing the number of concentrate feeding places (P = 0.001; Table 4). Regardless of treatment, eating rate of concentrate and straw increased from wk 1 to 3, as well as the time spent eating barley straw (P < 0.05; data not shown). Lying time was lesser in wk 3 compared with wk 1 (P < 0.05), but no difference in standing time was observed among weeks (data not shown).

View larger version (14K): [in this window] [in a new window]   Figure 4. Concentrate eating pattern during the (a) first and (b) third week after arrival at the feedlot, and (c) average straw eating pattern of Holstein calves in pens with 1 (T1), 2 (T2), or 4 (T4) concentrate feeding places (8 calves/pen). L,QWithin a week, linear (L) or quadratic (Q) coefficients of regression of the number of feeding places was significant (P < 0.05). The bars along the top of each panel represent SEM.

The number and distribution of displacements among calves from feed and water containers are presented in Table 5. The number of displacements from concentrate feeders responded quadratically (P < 0.001) when increasing the number of concentrate feeding places per pen, being greatest in T2, intermediate in T1 and lowest in T4. The number of displacements from the straw feeders was not affected by treatments (P = 0.11), but the treatment x week interaction (P < 0.01) indicated a linear increase in the number of displacements per pen and day at wk 3 (P = 0.01; data not shown). The number of displacements from the water bowls showed a quadratic effect of treatment (P = 0.006), with T2 calves showing the greatest level of aggression in the bowls. The total number of displacements also followed a quadratic pattern (P = 0.03), with T2 calves showing the greatest values because of the relative weight of the displacements carried out by the calves when competing for different resources. The average number of displacements across treatments from the concentrate feeders increased from 20.3 ± 1.0 in wk 1 to 30.9 ± 3.0 in wk 3 (P < 0.05), which led to an increase in the total number of displacements from 47.6 ± 3.0 in wk 1 to 63.2 ± 4.1 in wk 3 (P < 0.05; data not shown). However, week after arrival did not affect the number of displacements from the straw feeders or from the water bowls.

	DISCUSSION

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Intake and Performance

Total DMI, ADG, and live BW responded quadratically in the overall arrival period as the number of feeding places per pen increased, with low values at the greatest level of competition. This indicates that there is a threshold value on performance at 2 concentrate feeding places below which the negative effects on performance were observed but above which no positive effects are attained. In agreement with these results, time at the concentrate feeders also showed a quadratic effect. Nevertheless, no such threshold was observed in wk 1 where the effects were linear because adaptation mechanisms were not triggered during the first week after arrival. This indicates that adaptation to the feedlot could be delayed when competition at the feeder is increased. However, T2 calves adapted to the social environment at wk 3 by spending more time at the concentrate feeders during daylight when competition was lesser (between both major peaks), and maintaining a preferred eating rate not different from T4. This modification probably allowed T2 calves to compensate intake and performance after wk 2. Although T1 and T2 calves prolonged the major peaks of eating activity, they seemed reluctant to change more drastically the concentrate eating pattern throughout the day toward nighttime when less competition was present, as observed by Gonyou and Stricklin (1981) and Olofsson (1999) in well-adapted cattle. However, despite this result and a 20% increase in the concentrate eating rate of T1 calves at wk 3 compared with the other groups, no compensation of intake was achieved. Concentrate eating rate was 46.5, 44.6, and 46.1 ± 2.36 g of DM/min in wk 1, and 65.1, 54.2, and 58.1 ± 2.95 g of DM/min in wk 3, for T1, T2, and T4, respectively (data not shown). Another adaptation to the social environment was an increase in the total time spent eating straw as the number of concentrate feeding places per pen decreased, particularly at preferred eating times (i.e., at major eating periods and in the daytime between them). This resulted in a linear increase in straw intake as the number of feeding places per pen decreased.

The linear increase in the within-pen SD in ADG and live BW suggests that no such a threshold value existed in performance variability among calves sharing the same pen, with differences between pen-mates becoming larger as competition level increased. Furthermore, the within-pen variability of BW increased over the weeks for T1 and T2 but was more stable within T4 pens (treatment x day P = 0.03; data not shown). Accordingly, the within-pen SD of BW at the start of the experiment was 5.66, 5.78, and 5.97 ± 0.15 kg per pen, whereas at the end of the adaptation period it was 12.4, 11.0, and 8.2 ± 1.9 kg/animal for T1, T2, and T4 pens, respectively (linear P = 0.007). This greater within-pen variability was due, in part, to the effects of social dominance on ADG for T1 and T2 calves. Thus, the low number of feeding places per pen reduced the group and individual growth rates in T1, whereas in T2 only some individuals’ growth rates were affected and no effects were observed in T4. Our results suggest that individual variability in production parameters can be a useful indicator of animal welfare and that an increase in variability, even if the average values remain unchanged, may indicate that some animals have difficulties in coping with their environment. In consequence, their welfare is compromised. To our knowledge, there are no studies of feeding space for calves on high-concentrate diets upon arrival at the feedlot. Results concerning DMI in experiments dealing with feeding space have generally resulted in no effects on DMI (Longenbach et al., 1999; Olofsson, 1999). Time at the feed bunk was reduced in all cited studies when feeding space was reduced, resulting in increased eating rates. Longenbach et al. (1999) increased the feed bunk length from 0.15 to 0.31 or 0.47 m in 3 groups of replacement heifers with different ages and observed a trend for increased within-pen SD in ADG and BW in the 2 older groups, particularly greater at the end of each study. However, Longenbach et al. (1999) observed decreasing number of heifers able to eat simultaneously at a given linear feed bunk allowance as the heifers’ age increased. Zinn (1989) did not observe any effect on performance when increasing the linear manger space from 0.15 to 0.60 m/animal in lightweight steers at high growth rates. However, the number of animals able to eat together was not reported, smaller groups were used (4 steers/pen), and animals were well-adapted to the environment and the competing situation. Nevertheless, feed barrier design could be one contributing factor to differences with previous studies, apart from group size, stress level, and adaptation period. For instance, Huzzey et al. (2006) reported that the negative effect of reduced feeding space on time at the feeder of dairy cows was greater when headlocks were used compared with post-and-rail. These authors stated that feeding was perhaps more comfortable when no physical barrier existed between the cows and the feed and between adjacent cows.

Physiology

The week after arrival affected all performance and hematology variables independently of treatments. The DMI and the ADG were lowest during the first week, whereas NEFA, total WBC count, and the N:L ratio were greatest on d 7. However, fecal GM concentration indicated that calves were as stressed on d 7 as on d 0 (data not shown). This would indicate that the first week after arrival at the new conditions is the most stressful time for transported calves. Stressful conditions are associated with increased energy demand and decreased appetite, which could lead to depletion of energy stores. The linear treatment effect in wk 1 on concentrate DMI, ADG, and G:F indicates that during the most stressful week there are advantages to having more feeding space available, and such a strategy could improve the animals’ adaptation to the new conditions. Nevertheless, these treatment effects in wk 1 were not accompanied by changes in blood cells profile, haptoglobin, or fecal GM concentration. However, the quadratic effect of treatments on serum NEFA showed greater values in T1 and T2 calves on d 7, and on β-HBT in T1 calves, as expected.

Release of NEFA from adipose tissue is the net result of lipolysis of adipocytes or increased energy demands, or both, whereas β-HBT is one of the ketone bodies that come from incomplete oxidation of NEFA when its hepatic oxidation limit is reached (Adewuyi et al., 2005). The hepatic oxidation of NEFA and the β-HBT use by peripheral tissues through high activity or muscular exercise seemed to reach a limit on d 7 of the current study, which led to their accumulation in blood when feeding places per pen were reduced. Catecholamines, meanwhile, are involved in the short-term emergency reaction that mobilizes resources quickly, such as NEFA (Raynaert et al., 1976), for the metabolic requirements of fight or flight, whereas corticosteroids amplify and extend the metabolic effects of catecholamines in the long-term general adaptation syndrome (Dantzer and Mormède, 1983). The high NEFA levels on d 7 for T1 and T2 calves could be the result of increased energy demands as shown by increased standing times, decreased lying time, and increased aggressive interactions. However, marked increases in NEFA levels (0.5 to 1 mM) were also observed by midterm underfeeding, but they should return to prefasting levels at 1 to 2 d after refeeding (Chilliard et al., 1998). The absence of a treatment effect on fecal GM does not concur with the increase in NEFA observed at the 2 greatest levels of social pressure at the concentrate feeders in the current study.

Haptoglobin is an acute phase protein that increases in the blood as a consequence of inflammation, tissue damage or injury, and infection. Serum haptoglobin concentration decreased linearly as the number of feeding places per pen increased, although differences were very small. Additionally, no conclusions should be drawn from this result because serum haptoglobin concentration in the current study showed an abnormal decrease on d 7 and 14 compared with d 0 (data not shown), which is opposite to expectations and other reports in beef cattle after marketing (Berry et al., 2004). However, serum haptoglobin concentration did not always increase after short transportation (Arthington et al., 2003).

The number and proportion of leukocytes in the blood represent their state of distribution in the body and the activation of the immune system in response to stress. Rats with chronic stress showed decreased lymphocyte counts triggered by high adrenal hormones such as corticosterone (Dhabhar and McEwen, 1997). Many authors have also used the immune response, such as the N:L ratio and lymphocytes, as an indicator of stress and immunosupression in calves (Hickey et al., 2003). However, neither these variables nor fecal GM were affected in the current study indicating that immune response was not compromised, at least at the group level, in agreement with Corkum et al. (1994). Only the lymphocyte count increased numerically as the number of feeding places increased, even under a greater hemo-concentration. The lack of a treatment effect on fecal GM is striking because agonistic behavior, crowding, and the mere presence of a dominant animal resulted in greater circulating corticosteroids in farm animals (Dantzer and Mormède, 1983). In dairy cattle, the concentration of corticosteroid metabolites in fecal samples reflects the amount produced at about 12 h (6 to 16 h) earlier but depends on the lower tract transit time (Morrow et al., 2002). Therefore, GM in fecal samples in the current study could reflect blood levels at about, or after, 2030 of the previous day, just after the sunset major period of eating activity, but when one of the lowest levels of competition at the feeder was observed. It is also possible that the stress level caused by the increased and short-term competition in the current study is not marked enough to be detected in fecal samples. Serum NEFA concentration was measured during the major morning period of eating (0830) and showed increases at the 2 greatest competition levels in the current study, whereas a numerical decrease in lymphocytes was also observed. Both factors were affected under short-term stress models and triggered by corticosteroids in order to improve fitness by energy mobilization (NEFA) and redistribution of leukocytes to organs where the immune function is enhanced (Raynaert et al., 1976; Dhabhar and McEwen, 1997).

Maintenance Behavior

In agreement with effects observed on DMI and ADG, time at the concentrate feeders and concentrate eating rate also showed a quadratic effect over the 4-wk arrival period. Nielsen (1999) suggested that social animals, like cattle, try to attain a preferred feed intake and a preferred feeding rate while feeding at specific times of the day. In addition, groups of calves also synchronize their behavior trying to eat and rest at the same time. This means that when social pressure at the feeder increases, animals may adapt to it by feeding at a faster rate than they prefer, eating less than they prefer, or by feeding at less preferred times of the day. In the current study, as the number of feeding places per pen decreased, so did the time spent eating concentrate at all 3 peaks of eating activity, in agreement with previous studies on dairy cows (DeVries et al., 2004; Huzzey et al., 2006). This fact is probably related to feeder occupancy but also to social avoidance because feeders of T1 pens were only occupied for 6 min/h or 60% of the total available time during the major eating periods. Calves under T2 adapted to the social environment through an increase in concentrate eating time between both major peaks of eating, but not even a greater eating rate of T1 calves in wk 3 was enough to compensate concentrate intake. Therefore, adaptation to the competing situation required more time and efforts by the calves to modify their behavior as competition level increased. Perhaps the reluctance of T1 calves to change more drastically the diurnal concentrate eating pattern together with enough availability of space in the straw feeders resulted in the increased straw intake. We hypothesize that a subordinate calf would eat straw rather than wait around the concentrate feeder while it is occupied in order to dissipate the tension and anxiety due to increased social pressure at the concentrate feeders, unlike TMR fed dairy cows when feeding space was reduced and no other feeding choice was available (Huzzey et al., 2006). When a calf was displaced from the concentrate feeder, it usually went straight to the straw feeders. These processes were reflected in linear increases in the within-pen variation of time at the concentrate and straw feeders. This variability became particularly important in T1 pens because 2 calves ate only barley straw and did not approach the concentrate feeders in wk 3 (non-eaters). In addition, the circadian rhythm of eating has also been suggested as indicators of welfare in cattle (Gonyou, 1986). From this point of view, the calves in the current study were restricted in their natural eating behavior when the number of feeding places per pen decreased, particularly at peak eating times.

Daily time spent lying decreased linearly, whereas that spent standing increased as social pressure at the concentrate feeders increased. The increase in the time spent standing was found to be the result of a greater time spent waiting for an occupied feeder when increasing competition in dairy cows (Olofsson, 1999; Huzzey et al., 2006). However, we did not record which activity was performed during standing times.

Social Behavior

The frequency of fights has been considered another behavioral indicator of social stress (Dantzer and Mormède, 1983). The observed total number of displacements per animal and day was 6.46, 8.37, and 5.95 for T1, T2, and T4 calves, respectively. These values are similar to those found by Olofsson (1999) when using 1 cow per feeding station (7.2) but lower than those reported when using 3 or 4 cows per feeding station (Olofsson, 1999; Huzzey et al., 2006). The treatment differences in the number of displacements from each resource container may be greatly influenced by the design and spatial organization of the facilities in the current study. The feeding area was at the front of each pen, with concentrate and straw feeders and water bowls being adjacent to each other. The lack of difference between T1 and T4 in the number of displacements from the concentrate feeders could have been the result of some calves in T1 pens avoiding competition for a feeding place. This may be due to the fact that the design of the feed barriers required great effort to displace a pen-mate and high aggression was suffered during displacement. For instance, the number of displacements were fewer with headlocks compared with post-and-rail (Huzzey et al., 2006). The greatest competition and level of aggression in concentrate feeders were observed at peak feeding times in the current study (data not shown), in agreement with Kondo et al. (1984). During the first days after arrival, many unsuccessful displacements were carried out, and it took some time for the calves to learn how to displace a pen-mate. Unsuccessful displacements were not recorded in the current study, but a comprehensive discussion presented by Wierenga (1990) stated that this type of feeder design may either protect a cow from butting when feeding or she may feel unsafe because of the inability to defend herself or escape. The number of displacements from the concentrate feeders was greater in wk 3 compared with wk 1 when they are expected to decrease (Kondo et al., 1984). Thus, it is also likely that calves did not reach a stable social hierarchy by wk 3, and the results of the current study may be a consequence of the process of establishing dominance relationships.

The ADV x treatment x week interaction indicated that regression coefficients of ADV on ADG were different depending on when and in which treatment the dominance was measured. Indeed, the effect of dominance on ADG was negative in wk 1 and positive in wk 3 in T2 pens, negative in wk 1 and quadratic in wk 3 in T1 pens, but ADV did not have a significant effect in T4 pens. Moreover, the effect of ADV on ADG in wk 3 was greatest within T1 and decreased as competition at the concentrate feeder decreased. Although R-squares are not calculated in PROC MIXED models, we ran the same model in PROC GLM, which explained 63% of the variation. Dominance was negatively related to time at the concentrate feeders within T1 and T2 pens in wk 1 (P < 0.05; data not shown). A possible hypothesis is that high ranking animals during wk 1 spent less time at the concentrate feeder and had low ADG because they were more active chasing calves to establish dominance and had lesser concentrate intake. Greater energetic cost could also be associated with increased aggressiveness (activity) in high ranking calves. Conversely, the efforts to establish dominance in wk 1 brought benefits in wk 3 because the relationships between ADV and ADG, and ADV and time spent eating concentrate were positive (data not shown). This is in agreement with observations made by Wierenga (1990), who reported that the correlation between dominance value in dairy cows and time spent in the free stalls or in the feed bunk were larger with increasing competition. The quadratic effect of ADV on ADG within T1 calves at wk 3 of the current study is more difficult to explain because the 2 non-eater calves were responsible for this effect. These calves had a high ADV as a consequence of winning most of the few displacements they were involved in only at the straw feeders, and they had low ADG. If these calves are not considered in the analysis, the effect of ADV on ADG becomes linearly positive in T1 pens (b = 0.41; P = 0.07). Dominance was related to time spent eating concentrate in 2 different ways. The number of times a calf was displaced by another animal (Spearman Rho = –0.27, P = 0.02) and the number of times it displaced another individual (Spearman Rho = –0.25, P = 0.03) from the concentrate feeders were both negatively correlated to the time spent eating concentrate and to ADG (Rho = –0.29 and P = 0.01 vs. Rho = –0.24 and P = 0.04). This could be due to several causes. First, calves being often displaced had more interrupted eating bouts. However, Harb et al. (1985) reported that submissive cows increased their eating rate more than dominants without any negative effect on intake when competition was increased. Therefore, more research is needed to study the relationship among social rank, feed intake, and feeding behavior. New technologies such as automated feeding behavior monitoring systems could offer great possibilities. Second, the calves could also have developed fear of being aggressively displaced by dominant animals, leading to avoidance or refusal to enter the concentrate feeders. Finally, calves being often displaced had the choice to eat from the straw feeders where less competition and aggression were usually present because there was more space available, and there were no feed barriers separating 2 adjacent calves eating straw. This is consistent with the low number of displacements from the concentrate feeders observed in the T1 pens of the current study. Animals do not habituate to some aversive procedures (Grandin, 1997), and low-ranking animals keep more distance and avoid encounters with dominant pen-mates (Manson and Appleby, 1990). Stricklin and Gonyou (1981) fed groups of 15 beef cattle from a single stall or from an open trough. They did not observe any effect of treatments or dominance on final BW. However, average weight in the single stall system did not increase during the initial 2 wk of adaptation to the limited feeding space, and about 10% of the steers were difficult to get on-feed during the first month (Gonyou and Stricklin, 1981). McPhee et al. (1964) reported that low-ranking animals were interrupted more often while feeding and had shorter feeding times compared with dominant animals, but there were no relationships between social rank and final BW in long-term studies. In agreement with the current study, Harb et al. (1985) concluded that as competition level increased, so did the CV between cows in the time spent eating and in intake. Conversely, Leaver and Yarrow (1980) reported that dominant animals ate more than submissive ones. It is also likely that effects of dominance are exacerbated in the present experiment because of the stressful condition of the calves after arrival, the design of facilities, the novel environment, the lack of previous experience in competitive situations, and the low number of animals per group.

In summary, increasing the number of calves per concentrate feeder linearly decreased performance during the first week after arrival at the feedlot, as measured by feed intake and average daily gain. However, performance subsequently recovered when there were 4 rather than 8 animals per concentrate feeding place. The variability in performance within a pen was increased as competition level increased, reflecting the greater effect of dominance as social pressure at the feeder increased during hierarchy formation. Blood variables and fecal GM did not show a consistent effect on immune response and welfare. Indicators of body fat turnover were greatest when 8 and 4 calves per feeder were used. Some behavioral variables could indicate that welfare is poorer as the number of feeding places per pen decreased. The daily time spent lying decreased, time spent standing increased and an alteration of the circadian rhythm of eating was observed as the number of feeding places per pen decreased. The number of aggressive interactions indicated that the social environment was not greatly affected only at the lowest level of social pressure (2 calves per concentrate feeder).

	Footnotes

 
¹ Welfare Quality Project (FOOD-CT-2004-506508) from VI framework program of the European Union.

² MECD Studentship (FPU AP20023344) is acknowledged.

³ Corresponding author: Alfred.Ferret{at}uab.es

Received for publication June 15, 2007. Accepted for publication October 5, 2007.

	LITERATURE CITED

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 


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