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ANIMAL PRODUCTION |
* University of Florida–IFAS, Range Cattle Research and Education Center, Ona, 33865-9706; and
USDA-ARS, Subtropical Agricultural Research Station, Brooksville, FL 34601-4672
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Abstract |
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 Top Abstract INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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Key Words: acute phase protein • preconditioning • steer • stress • transportation • weaning
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INTRODUCTION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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). Although Florida is the leading state in the United States for the number of large cow-calf operations (>2,500 cows; USDA, National Agricultural Statistics Service, 2002), there is no commercial feedlot industry; therefore, nearly all market steers are shipped outside the state for further growing and finishing. Stressors associated with weaning and shipping are key factors affecting subsequent calf health and performance. Multiple research efforts have focused on management of these stressed calves and on systems that will decrease morbidity and improve performance (Duff and Galyean, 2007). Previous research efforts focused on early-weaning calves at 70 to 90 d of age have reported improved feedlot performance (Peterson et al., 1987; Myers et al., 1999; Arthington et al., 2005). This response appears to be related, at least in part, to reduced plasma concentrations of acute phase proteins, such as ceruloplasmin, haptoglobin, and fibrinogen, in early-weaned calves (Arthington et al., 2005). In addition to early weaning, other preweaning management options exist, such as weaning calves on the ranch for a period of time before transport (30 to 45 d) or creep feeding calves before weaning. Although results have been variable (Pritchard and Mendez, 1990), these systems may provide further value to both the producer and buyer (Dhuyvetter et al., 2005; King et al., 2006). The objective of the present study was to evaluate the effects of 4 preweaning management systems on plasma acute phase protein concentrations and the performance of weaned, transported steers during a 30-d feedlot receiving period. |
MATERIALS AND METHODS |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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This study was conducted at the University of Florida, Range Cattle Research and Education Center (RCREC), Ona, and the USDA-ARS Subtropical Agricultural Research Station (STARS), Brooksville, FL. Animals were cared for by acceptable practices as outlined in the Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching (FASS, 1999).
This study was conducted over 2 consecutive years (2004 and 2005) with 96 Angus-sired steer calves derived from multiparous Brahman x British cows (64 and 32 in yr 1 and 2, respectively). Steers were randomly allocated to 1 of 4 weaning treatments, which were imposed on all calves at the ranch of birth (RCREC) before transport to the receiving feedlot (STARS). Weaning treatments consisted of 1) early weaning, 2) creep feeding, 3) preweaning, or 4) control (24 steers/treatment; 16 and 8 for yr 1 and 2, respectively). Early-weaned steers were weaned in January at approximately 70 to 90 d of age and grazed on annual ryegrass (Lolium multiflorum) pastures during the winter months and perennial grass pastures during the summer months [bermudagrass (Cynodon dactylon) in yr 1 and a combination of bahiagrass (Paspalum notatum) and stargrass (Cynodon spp.) in yr 2]. Early-weaned steers were provided supplemental concentrate (1% BW; Table 1) daily from the time of weaning until shipping. Creep-fed steers were provided free-choice access to the same concentrate supplement (Table 1). Preweaned steers were separated from their dam before shipping and also provided access to the same concentrate supplement (Table 1). Creep feeding and preweaning were initiated 45 and 53 d before shipping in yr 1 and 2, respectively. All steers were provided free-choice access to a complete salt-based trace mineral supplement, which contained 12.0% Ca, 9.0% P, 9.0% Na, 0.30% Zn, 0.15% Cu, 0.05% Mn, 0.02% I, 0.005% Co, and 0.004% Se.
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). Steers were also provided free-choice access to long-stem bermudagrass hay and the same free-choice, salt-based trace mineral supplement provided before d 0 (described above). Daily intake of concentrate and hay were determined by subtracting the DM of the daily refusal from the DM of the daily offer of both hay and concentrate. Feed DM was achieved by drying daily samples in a forced-air oven at 55°C for 48 h. Daily samples of hay and concentrate were pooled by week and submitted to a commercial laboratory for nutrient analysis (Dairy One Laboratory, Ithaca, NY; Table 1). Steer BW was determined before shipping (d 0), on arrival (d 1), and at the conclusion of the study (d 29; following a 16-h removal from concentrate and hay). Individual steer ADG during the receiving period was determined by the difference between the final shrunk BW and initial arrival BW (d 1). Transport BW shrink was measured as the percentage change from the BW before shipping (d 0) and the BW at arrival (d 1). For acute phase protein analyses, blood samples from each steer were collected from the jugular vein into heparin-coated evacuated tubes (Vacutainer, Becton Dickinson Inc., Franklin Lakes, NJ) at d 0, 1, 4, 8, 15, 22, and 29. Tubes were immediately placed on ice until transfer to 4°C, at which they were stored for 24 h before centrifugation at 2,000 x g for 20 min. Samples were stored frozen at –20°C until later analysis.
Assessment of Calf Temperament
The impact of weaning management treatment on measures of steer disposition was assessed on d 0 before loading steers onto the transport trailer. Measures included 3 methods of temperament assessment, including chute exit velocity and a subjective temperament score assigned to each calf in the chute (chute score) and in a pen (pen score). Exit velocity was achieved by determining the speed of the calf exiting the squeeze chute by measuring rate of travel over a 1.6-m distance with an infrared sensor (FarmTek Inc., North Wylie, TX). Chute score was assessed by a single technician based on a 5-point scale (adapted from Voisinet et al., 1997), where 1 = calm, no movement, 2 = restless shifting, 3 = constant shifting with occasional shaking of the chute, 4 = continuous movement and shaking of the chute, and 5 = violent and continuous struggling. For pen score assessment, steers exited the chute and entered a pen (10 x 15 m) containing a single technician and no other cattle. Once the steer entered the pen and noticed the technician standing inside the pen near the perimeter fence, the technician moved 3 steps directly toward the steer and assessed his response on a 5-point scale, where 1 = unalarmed and unexcited, walking slowly away from the technician, 2 = slightly alarmed, moving moderately quickly away from the technician, 3 = moderately alarmed and excited, moving away from the technician quickly, 4 = very alarmed and excited by the presence of the technician, moving very quickly and with head held high, or 5 = very excited and aggressive toward the technician in a manner that requires evasive action to avoid contact between the technician and steer.
Acute Phase Protein Analysis
Plasma concentrations of haptoglobin and ceruloplasmin were assayed. Plasma haptoglobin concentrations were determined in duplicate samples by measuring haptoglobin-hemoglobin complexing by the estimation of differences in peroxidase activity (Makimura and Suzuki, 1982). Results are expressed as arbitrary units resulting from the absorption reading at 450 nm x 100. For samples with an absorption reading of 
0.010, the intraassay coefficient of variation (CV) of duplicate samples was controlled to values of 20%, and for samples with an absorption reading of 
0.010, the intraassay CV of duplicate samples was controlled to values of 10%. Plasma ceruloplasmin oxidase activity was measured in duplicate samples by using the colorimetric procedures described by Demetriou et al. (1974). The intraassay CV of duplicate samples was controlled to values of 10%. Ceruloplasmin concentrations were expressed as mg/dL as described by King (1965). Interassay variation of both acute phase protein assays were controlled by CV limits of 10% as a result of a control sample analyzed in duplicate within each individual assay run. When the interassay CV exceeded 10%, all samples contained in the individual run with the control sample exceeding the average by the most were reanalyzed. This step was repeated until the results of standard pools for all runs resulted in a CV of 10%.
Statistical Analysis
All data were analyzed by ANOVA for a completely randomized design by using the MIXED procedure (SAS Inst. Inc., Cary, NC). Before leaving from the ranch of origin (RCREC), calves were maintained in single groups within treatment designation; therefore, treatments were replicated once (2-yr study). For analysis of preshipping ADG, temperament, and BW before shipping (d 0) and on arrival in the feedlot (d 1), the model statement contained the effect of treatment, and year(treatment) was the random variable. Pen was the experimental unit for all measurements during the feedlot receiving period, and year(pen x treatment) was the random variable. For analyses involving measurements collected over time (hay and concentrate DMI and acute phase protein concentrations), a repeated measures analysis was conducted, with the model statement containing the effects of treatment, time, and their interaction. For analyses involving shrink, ADG, overall DMI, and G:F, the model statement contained the effect of treatment. Treatment comparisons were made by using single-df orthogonal contrasts. The 3 treatment comparisons were 1) control vs. early-weaned, 2) creep-fed vs. preweaned, and 3) control vs. creep-fed and preweaned.
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RESULTS AND DISCUSSION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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Preweaning and creep feeding began at the same time, which was 45 and 52 d before shipping in yr 1 and 2, respectively. Steer BW and ADG before feedlot entry are provided in Table 2. Before shipping and while on pasture, average voluntary concentrate intake for creep-fed steers was 2.6 kg/d. Tarr et al. (1994) also reported annual variability in creep-feed intake, with an average daily intake of creep feed similar to those of the current study. The difference in BW gain of creepfed calves, beyond that realized by control calves, was 0.05 kg/d. Efficiency of this added BW gain was poor (G:F = 0.02) and was less than the values reported by Tarr et al. (1994). This difference may have been the result of the limited time of creep feeding in the current study (45 and 53 d in yr 1 and 2, respectively). Other researchers have shown that creep-feed intake and BW gain increase with advancing days of creep feeding (Faulkner et al., 1994; Tarr et al., 1994). Preweaned steers were offered the same concentrate supplement before shipping, but consumption was limited so as not to exceed 4.5 kg/steer daily. Average concentrate intake of preweaned steers was 4.1 kg/d.
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). We have previously observed annual variability in BW of early- vs. normally weaned calves at the time of shipping (Arthington and Kalmbacher, 2003). In that study and the current study, calves are weaned at the ranch of birth at 70 to 90 d of age and grazed on winter annual and summer perennial pastures. Daily concentrate supplementation is provided at 1.0% of BW. Before the time that normally weaned calves are separated from their dam, performance differences vary annually among early- and normally weaned calves, which are likely the result of the environmental impacts on available forage quality and quantity (Vendramini et al., 2006).
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0.01) for early-weaned steers compared with control steers (Table 3). Improved ADG of early-weaned vs. control steers has been shown previously. In a study imposing similar transportation methods (Arthington et al., 2005), early-weaned calves experienced a 54% greater ADG than their normally weaned contemporaries. One explanation for the greater BW gain of early-weaned steers may be attributed to differences in diet selection compared with control steers. Early-weaned steers had a greater DMI of concentrate and a lesser DMI of hay compared with control steers during the first week in the feedlot (Table 4; P 0.03). Increased dietary energy intake has been shown to improve BW gain of calves during the initial feedlot receiving period (Lofgreen et al., 1980). After the first week, there were no further DMI differences between these weaning treatments; however, average DMI for the 4-wk receiving period tended to be greater (P = 0.06) for early-weaned steers compared with control steers (Table 3).
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). Preweaned steers had a greater (P 0.03) DMI of concentrate, but not hay, compared with creep-fed steers during the first 2 wk in the feedlot (Table 4). Similarly, the average DMI of preweaned and creep-fed calves was numerically greater, albeit nonsignificant (P = 0.14), compared with control calves for the 4-wk receiving period (Table 3), which likely contributed to the greater ADG for creepfed and preweaned calves compared with control calves (Table 3). These results indicate that the preshipping management of feeder calves affects voluntary DMI of concentrate vs. hay when both are offered separately. This management procedure is a common practice among feedlots receiving stressed calves, where calves may be offered free-choice access to hay in addition to a complete mixed starter ration. In this study, calves that had been previously exposed to concentrate supplement had a greater percentage of DMI of concentrate vs. hay during the first week in the feedlot (66.4 vs. 79.0, 84.0, and 85.4% of total DMI as concentrate for control, creep-fed, early-weaned, and preweaned calves, respectively; P < 0.05 for both early-weaned vs. control steers and the average of preweaned and creepfed steers vs. control steers; SEM = 3.06).
Calculated over the 29-d feedlot receiving period, early- weaned calves had a 42% improvement in G:F compared with control calves (Table 3). Improved feedlot performance of early-weaned calves has been reported previously (Myers et al., 1999; Arthington et al., 2005). Feed efficiency did not differ (P = 0.72) among creepfed and preweaned calves; however, the efficiency of control calves was numerically inferior to the average efficiency of creep-fed and preweaned calves (P = 0.12; Table 3).
Acute Phase Protein Concentrations and Steer Temperament
Although there was a treatment x day interaction for plasma haptoglobin concentrations (P < 0.02), there were no significant single-df treatment contrasts within sampling days (data not shown). The interaction is a result of the magnitude and time of increase in plasma haptoglobin concentrations after shipping vs. individual treatment differences within sampling days. Pooled across all treatments, haptoglobin concentrations increased by 160% from d 0 to 1 and returned to baseline values by d 8. Preweaned calves tended (P = 0.08) to have a lesser increase in plasma haptoglobin compared with creep-fed calves. Although numerically greater than control calves, early-weaned calves experienced a similar increase in plasma haptoglobin concentrations from d 0 to 1 (2.15, 2.63, 1.49, and 1.50 absorption at 450 nm for control, creep-fed, early-weaned, and preweaned calves, respectively).
There was a treatment x day interaction (P < 0.01) for plasma ceruloplasmin concentrations. Ceruloplasmin concentrations were initially less in control steers compared with early-weaned steers (P < 0.05; Figure 1). After transport, ceruloplasmin concentrations increased sharply in both groups and were greater (P < 0.05) in control steers compared with early-weaned steers on d 15 and 22, and tended to be greater (P < 0.10) on d 8 and 29 (Figure 1). Ceruloplasmin concentrations were generally greater in creep-fed vs. preweaned steers (Figure 1), with differences (P < 0.05) observed on d 29 (Figure 1).
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), which affect nutrient metabolism and animal growth (Johnson, 1997). Research has shown that early-weaned calves have a lessened acute phase protein response after transport and feedlot entry compared with control calves weaned on the day of transport (Arthington et al., 2005). The magnitude of this acute phase response is negatively correlated to calf ADG after transport (Arthington et al., 2005; Qiu et al., 2007) and positively associated with the incidence of morbidity and subsequent requirement for antimicrobial treatment (Carter et al., 2002). The first few days after feedlot entry are critical to the subsequent health and productivity of the beef calf. The acute phase protein response following transport has been characterized in this and 2 other studies (Arthington et al., 2003, 2005). In each of these efforts, no incidence of morbidity was realized, even though the acute phase protein reaction was evident in each study. Therefore, it is apparent that overtly healthy calves still undergo the acute phase reaction and produce acute phase proteins as a result of normal management procedures such as weaning and transportation. The magnitude of this response may be a key indicator of subsequent productivity in the feedlot, especially during the initial receiving period (Arthington et al., 2005; Qiu et al., 2007). In more typical production situations, feedlot managers experience some level of morbidity in newly received feeder calves. The magnitude of the acute phase reaction is greater in these cases of clinical morbidity compared with calves that did not become morbid (Carter et al., 2002). Defined calf preconditioning programs (Roeber et al., 2001) and creep feeding (Fluharty and Loerch, 1996) have both been shown to reduce the incidence of morbidity significantly in newly received feeder calves. If the calves in the current study had undergone a greater amount of stress or immunological challenge, we likely would have realized greater differences in the acute phase protein response and subsequent productivity of the preweaned and creep-fed calves compared with control calves.
No treatment effects (P > 0.10) were observed for the selected measures of steer temperament in this study (Table 5). Other researchers have reported that feeder calves with calmer temperaments have improved ADG compared with cattle with excitable temperaments (Voisinet et al., 1997). In that study, researchers noted that cattle with Brahman influence exhibited a more excitable temperament compared with those with no Brahman influence (Voisinet et al., 1997). It is reasonable to anticipate behavioral differences because of the management treatments imposed in the current study, especially given the Brahman influence of the calves; however, no differences were observed. The lack of statistical significance is attributed to the lack of experimental units contributing to this analysis, because it involved replication only over the 2 yr of the study.
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In the current study, the intake of creep feed was not substantial (2.6 kg/d). At these rates, feed costs represented an average of $37 per calf annually (average of 49 d consuming 2.6 kg/d at $0.29/kg). Compared with control calves, the added gain resulting from creep feeding was only 0.05 kg/d. This is a poor result and could potentially be lessened if the creep-feeding process had been extended for a longer period of time.
Although few, if any, value-added marketing programs target creep feeding as a management prerequisite, a period of on-ranch weaning before shipping (preweaning) is a commonly prescribed calf preconditioning procedure. Although poorly presented in the scientific literature, preweaning is believed to prepare the calf for the stressors associated with transport and feedlot entry, thereby decreasing the stress-related incidences of morbidity. Cattle derived from a defined preconditioning program have been shown to have fewer incidences of morbidity and greater ADG during the first 2 mo in the feedlot (Roeber et al., 2001). In the current study, preweaned and creep-fed calves had a greater (P = 0.02) ADG compared with control calves during a 29-d feedlot receiving period. Indeed, inherent variation found among years and locations is a major factor affecting the value of preconditioning programs involving preweaning management systems (Pritchard and Mendez, 1990). This lack of regularity among performance responses is a major consideration when deciding whether to prewean beef calves on the ranch before shipping. Risks associated with preweaning must also be weighed against any potential advantages associated with market premiums paid for the practice. In our study, the average feed inputs associated with preweaning before shipping were $58 per calf. This estimate does not include the costs associated with the risk of calf loss through death or injury after weaning, nor does it include costs associated with labor or miscellaneous expenses such as fencing and feeding equipment. To account for expenses associated with the purchase of feed, steer calves in the current study (average BW at d 0 = 273 kg) would need to receive a premium of more than $9.50/cwt (1 cwt = 45.45 kg). A comparison of calves with similar vaccination management revealed an average premium of $4.19 per cwt for calves that were preweaned for at least 45 d before shipping compared with calves shipped at the time of weaning (King et al., 2006). That study used 2,777 lot loads (approximately 22,600 kg of net weight/lot load) of cattle, representing more than 326,000 feeder calves. Under the feed cost conditions realized in the current study, their results suggest that cattle buyers are not currently willing to pay a premium for preweaned calves sufficient to account for the costs associated with the purchase of feed required for the management practice. Fifteen years before the current study was conducted, Peterson et al. (1989) reported an economic evaluation of the value of preconditioned beef calves to the cow-calf producer. In that study, a similar gap was observed between the costs associated with calf preconditioning and the price-premium received for the practice. Nevertheless, changes in the industry may be occurring because the average value of 45-d preweaned calves has increased steadily over the past 11 yr in lot-load feeder calves marketed through a livestock videotape auction service (King et al., 2006). Other factors should also be considered that may improve the economic viability of weaning calves on the ranch before shipping, including 1) regional differences in feed costs, 2) efficiency of gain and change in calf value from the time of weaning to shipping, and 3) opportunities for smaller collaborating producers to achieve truckload groups of weaned feeder calves. Additional industry evaluation is warranted to further determine the value of preshipping management systems to both the seller and buyer of the feeder calf.
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Footnotes |
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3 Present address: Land O’Lakes (Beijing), Room 705, Office Tower 1, Henderson Centre, 18 Jian Guo Men Nei Ave., Beijing 100005, China.
2 Corresponding author: jarth{at}ufl.edu
Received for publication February 18, 2008. Accepted for publication April 7, 2008.
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LITERATURE CITED |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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