| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
ANIMAL NUTRITION |
,2
,
* Departament de Ciencia Animal i dels Aliments,
and
Departament de Biologia Cellular, Fisiologia i Immunologia, and
Animal Nutrition, Management and Welfare Research Group, Universitat Autònoma de Barcelona, 08193-Bellaterra, Spain
 |
Abstract |
|---|
 Top Abstract INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Key Words: feeding frequency • growing cattle • high-concentrate diet
|
INTRODUCTION |
|---|
|
TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
), time of daily feed delivery (Schwartzkopf-Genswein et al., 2004), limit-feeding of animals (Murphy et al., 1994), and frequency of feeding (Soto-Navarro et al., 2000).
Increasing feeding frequency results not only in a more constant but also in a lower postprandial decrease of ruminal pH (Kaufmann, 1976). Feeding ruminants more than once daily might decrease the risk of acidosis by minimizing starch intake per meal and result in more stable ruminal conditions. Sutton et al. (1986) and Yang and Varga (1989) reported in dairy cows that increasing feeding frequency of concentrate increases minimum ruminal pH, but decreases mean ruminal pH. However, the most important effect of increasing feeding frequency on ruminal pH is that it reduces pH fluctuations (Sutton et al., 1986; Yang and Varga, 1989; French and Kennelly, 1990). In steers fed a high concentrate diet, Soto-Navarro et al. (2000) found that there was a tendency for pH to be lower in steers fed once daily compared with those fed twice daily. Feeding twice daily also decreased ruminal VFA concentration and increased the acetate:propionate ratio, which might affect the efficiency of energy utilization by limit-fed cattle, and thus performance (Soto-Navarro et al., 2000).
The effects of feeding frequency on animal behavior and feeding behavior have been studied in dairy cows (Phillips and Rind, 2001; DeVries et al., 2005), but there is no information on beef cattle fed high-concentrate diets. It could be hypothesized that with more frequent feeding, intake would be more evenly spread throughout the day, moderating pH fluctuations and modifying feeding behavior.
We therefore designed an experiment to ascertain how increasing feeding frequency could affect intake, ruminal fermentation, and animal and feeding behavior in heifers fed a high-concentrate diet.
|
MATERIALS AND METHODS |
|---|
|
TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
The research protocol was approved by the Institutional Animal Care and Use Committee of the Universitat Autònoma de Barcelona.
Four Holstein heifers (average initial BW of 385 ± 6.2 kg) fitted with 1-cm i.d., permanent ruminal plastic trocars (Divasa farmavic S. A., Vic, Spain) were used. Body weight was recorded before feeding on 2 consecutive days at the beginning and the conclusion of the experiment. Heifers were randomly assigned to 1 of 4 experimental treatments in a 4 x 4 Latin square design. The four 2-wk periods consisted of 1 wk of adaptation and 1 wk of sampling and data collection. Treatments consisted of different feeding frequencies: a) distribution of feed once daily at 0800 (T1); b) distribution of feed twice daily, at 0800 and 2000 (T2); c) distribution of feed 3 times daily, at 0800, 1400, and 2000 (T3); and d) distribution of feed 4 times daily, at 0800, 1200, 1600, and 2000 (T4). Within each treatment, the amount of feed offered was the same at each feeding time. Heifers were individually housed in tie-stalls on rubber comfort mats on the Experimental Farm of the Universitat Autònoma de Barcelona. Surgery was performed several months before the beginning of the experiment, following standard surgical procedures (Balch and Cowie, 1962), and was conducted under local anesthesia with full aseptic precautions.
Feed Intake and Water Consumption
Heifers were offered ad libitum access to concentrate and barley straw. To ascertain the initial ad libitum intake, DMI was measured 2 wk before the beginning of the experiment in all heifers by offering the feed once daily at 0800. The concentrate was formulated according to the NRC (1996) guidelines. Ingredients and chemical composition of the concentrate are shown in Table 1. All ingredients of the concentrate were ground through a 3-mm screen and mixed. Barley straw was coarsely chopped to approximately 7 cm in length and contained 89.5% DM, 93.4% OM, 3.6% CP, 80.6% NDF, and 50.6% ADF (DM basis). Feeders were cleaned, and orts were collected at 0700 each morning. Each feedbunk was separated into 2 parts, 1 for the concentrate and the other for the barley straw, which was offered only once daily together with the first concentrate offering. Orts, which were collected on all days, were weighed before feeding, and the diet offered was 120% of the previous day’s intake. To register water intake, individual drinking cups with direct-reading flow meters were used (B98.32.50, Invensys model 510 C, Tashia SL, Artesa de Segre, Spain), which allowed a minimum water measurement of 20 mL.
|
The length of all inactive intervals (min) in which feeding did not occur were counted over 5 d per heifer and period and were used to calculate the meal criterion through a modification of the mixed distribution methodology described by Yeates et al. (2001), using gamma distributions to improve the fit of the data. Meal criterion was defined as the minimum time required to consider 2 periods of eating activity as separate events. All minute-by-minute eating observations, separated from no-eating observations shorter than or equal to the meal criterion, were grouped into meals. Meals smaller than 50 g of feed consumed were not considered an individual meal. Meal frequency (meals/d) was the number of intervals for which eating activity was registered and exceeded the meal criterion. Meal length (min/meal) was calculated as the time from the first eating observation until the time of the last eating observation within a meal, prior to an inactive interval that exceeded the meal criterion. Total daily meal time was simply the sum of each meal length (min/d). Meals were further characterized by DM ingested (meal size; g of DM/meal), and rate of DM ingested per meal (eating rate; g of DM/ min) calculated as the ratio of amount of feed ingested and the corresponding meal length. Calculations were required to take into account changes in feed moisture during the day because of heifers drooling. Estimates of DM content in the feed remaining were made assuming linear changes between DM content of feed offered and that of the refusals (Dado and Allen, 1994). Regardless of the meal time, daily patterns of DMI were analyzed based on the amount of DM eaten throughout the day between each 2-h interval after feeding; that is, intervals 1 to 12. To analyze daily meal size and length patterns, meals were assigned to a given after-feeding interval, depending on its starting time.
Animal Behavior
To register animal behavior throughout the day, a video-camera recording device was installed in the barn. The device consisted of a digital, black and white camera (model LTC 0500/50, Philips, Eindhoven, the Netherlands), with and iris vari-focal lenses (model LTC 3274/40, Philips) that was connected to a time-lapse recorder (model RT 2
/00T, Philips). Animal behavior was video-recorded for 24 h during d 8, 10, and 12 of each sampling period, and the posture and behavior of each heifer was recorded at 5-min intervals. The behavioral categories used were eating, ruminating, drinking, and nonchewing behaviors. An observation was defined as eating when the heifer was eating from the feed bunk with its muzzle in the feed bunk or chewing or swallowing food with its head over the bunk. Ruminating included the regurgitation, mastication, and swallowing of the bolus. An observation was recorded as drinking when the heifer was with its muzzle in the water bowl or swallowing the water. Nonchewing behaviors included the following: resting, when no chewing behavior and no apparent activity were being performed; self-grooming, defined as nonstereotyped licking of its own body or scratching with a hind limb or against the fixtures; social behavior, registered when a heifer was licking or nosing a neighboring heifer with the muzzle or butting; oral behavior, which included the act of licking or biting the fixtures; and observational behavior, which was when the heifer was alert, listening, and looking toward any sounds or movements.
Data for each activity is presented as the percentage of total daily observations obtained by summing the number of times the activity was observed and divided by the total number of observations during the day, with 288 observations per day or 864 observations per heifer and period. To analyze behavioral patterns, the day was subdivided in 12 intervals of 2 h, each starting at the time of feeding (intervals 1 through 12). The percentage of observations made for each activity was calculated by summing the number of times the activity was observed and dividing by the total number of observations during the interval, with 24 observations per interval or 72 observations per interval and period.
Ruminal Fermentation
On d 11 of each period, ruminal samples (0.20 L) were taken with an electric vacuum pump from several locations in the rumen, immediately before feeding (0 h) and at 4, 8, 12, 16, 20, and 24 h after feeding. The ruminal fluid was squeezed through 4 layers of cheesecloth, and the pH was immediately measured with a glass electrode, pH meter (model 507, Crisson Instruments SA, Barcelona, Spain). Two subsamples were taken. First, a 4-mL sample of filtered fluid was acidified with 4 mL of 0.2 N HCl and frozen at –20°C. Samples were later thawed, centrifuged at 25,000 x g for 20 min, and the supernatant was analyzed for NH3-N (Chaney and Marbach, 1962) by spectrophotometry (model Libra S21, Biochrom Ltd., Cambridge, UK). Second, 4 mL of filtered ruminal fluid were added to 1 mL of a solution made up in distilled water, with 1% (wt/ wt) mercuric chloride to impede microbial growth, 2% (vol/vol) orthophosphoric acid, and 0.2% (wt/wt) 4-methylvaleric as an internal standard, and frozen at –20°C (Jouany, 1982).
Samples for VFA analyses were thawed, centrifuged at 15,000 x g for 20 min, and diluted 1:1 (vol/vol) in distilled water for subsequent analysis using a GLC provided with an autosampler (model 6890, Hewlett Packard, Palo Alto, CA). A capillary column treated with polyethylene glycol as the stationary phase was used (BP21, SGE, Europe Ltd., UK). The injector and flame ionization detector were at 275°C, split injection was used (split ratio of 25:1), and 1 µL was injected. The column oven temperature was held at 85°C for 1 min, increased at 4°C/min to 148°C, increased again at 35 °C/min to 220°C, and finally held at 220°C for 4 min. The total run time was 22.81 min, and the carrier gas used was He. The column flow was 1.2 L/min, and the average speed was 31 cm/s.
Ruminal fluid pH, NH3-N, and VFA measures after feeding were averaged across time by calculating the area under the ruminal data vs. time curve and dividing by the total time (Pitt and Pell, 1997). Area under the pH curve and time during which pH was below 5.8 were calculated, assuming that the change in pH between 2 measures was linear.
Chemical Analyses
Concentrate and barley straw refusals for each heifer were removed before feeding, weighed, and subsampled to be later analyzed for DM content in order to record daily feed DMI. Dry matter content of feed offered and refusals was determined by drying the samples for 24 h at 103°C in a forced-air oven according to the AOAC (1990; ID 950.01). Feed offered and refusal subsamples were collected daily for 7 consecutive days, composited for each heifer and period, mixed, and dried in a forced-air oven at 65°C for 48 h for later chemical analysis. Feeds and refusals were ground in a hammer mill through a 1-mm screen (P. PRAT SA, Sabadell, Spain) and retained for analysis of DM and ash (AOAC 1990; ID 942.05). Nitrogen content was determined by the Kjeldahl procedure (AOAC, 1990; ID 976.05). Organic matter was calculated as the difference between DM and ash content. Neutral detergent fiber and ADF were determined by the procedure of Van Soest et al. (1991), using a thermostable 
-amylase and sodium sulfite. Dry matter intake was calculated as the difference between DM offered and refused.
Statistical Analyses
The individual animal fed a given treatment diet at each period was considered the experimental unit in all of the analyses, which were performed by mixed model ANOVA using the MIXED procedure (SAS Inst. Inc., Cary, NC). All variables were averaged to generate period means for each heifer and treatment for statistical analysis. The model contained the fixed effect of feeding frequency, and period and heifer as random effects (Tempelman, 2004). Orthogonal contrasts were used to assess linear, quadratic, and cubic relationships between feeding frequency and the dependent variable. Whenever available, repeated measures were used. This model contained the fixed effect of either sampling time or after-feeding interval as the repeated measure, subjected to animal x period nested within a treatment diet, the fixed effect of treatment, and their interaction. In order to perform the regression analysis in the repeated measures model, an intercept and linear, quadratic, and cubic coefficients of regression of treatments were obtained for each sampling time from the SOLUTION statement of SAS. To attain this, the model included the fixed effects of sampling time as a class variable and the interaction between sampling time and the feeding frequency. Thus, intercepts and coefficients of regression were particular to each sampling time and tested for their level of significance. The choice of the best covariance structure was based on biological meaning and fit statistics, where the model that minimized the Akaike information criteria corrected or Schwarz’s Bayesian information criteria was preferable (Littell et al., 1998; Wang and Goonewardene, 2004). For most of the ruminal variables with repeated measures, the heterogeneous Toeplitz covariance structure provided the best fit because it yielded a cyclic (circadian) correlation matrix, where the 0-h sampling time was more correlated to 24 h than to any other sampling time. It also allowed different variances among the repeated measures. Significance was declared at P < 0.05, and tendencies are discussed at P < 0.10.
Variables expressed as percentages were statistically analyzed after square root-arcsine transformation but are presented as back-transformed least squares means (Mitlöhner et al., 2001). These data were analyzed with the MIXED procedure of SAS for repeated measures. Because equally spaced intervals within the day were used, the heterogeneous autoregressive covariance structure generally resulted in the best fit of the data.
|
RESULTS |
|---|
|
TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Intake and Water Consumption
Feeding frequency did not affect DMI (P >0.10; Table 2). The average concentrate, barley straw, and total intake were 8.8 ± 0.61, 0.97 ± 0.19, and 9.8 ± 0.73 kg of DM/d, respectively. The mean proportion of concentrate and barley straw consumed were 91.3 and 9.7%, respectively, and were not affected (P > 0.10) by feeding frequency. Water consumption tended to increase linearly as feeding frequency increased (P = 0.08).
|
The average ruminal pH was not affected by feeding frequency (P > 0.10; Table 3), but pH patterns showed a significant (P < 0.01) quadratic effect of treatment x time after feeding interaction. Ruminal pH at 12 h after feeding was greatest in T2 and lowest in T1 (Figure 1). Lowest pH was not affected by feeding frequency (P > 0.10), but greatest pH tended to increase linearly (P = 0.08) as feeding frequency increased. The number of hours at pH below 5.8 or area under this pH curve was not affected by feeding frequency (P > 0.10).
|
|
Total VFA concentration and VFA proportions were not affected by feeding frequency (P >0.10; Table 3
), except the valerate proportion, which decreased linearly (P = 0.05) as feeding frequency increased. Mean values for total VFA concentration, and the proportions of acetate, propionate, and butyrate were 109.2 mM, 56.8 mol/100 mol, 25.1 mol/100 mol, and 12.4 mol/100 mol, respectively. The concentration of ammonia-N was affected cubically (P = 0.02) by feeding frequency (greatest for T3 = 9.3 mg of N/100 mL; lowest for T2 = 7.2 mg of N/100 mL).
Animal Behavior and Feeding Behavior
Feeding frequency had no effect on daily percentages of behavioral activities, except for observational behavior where there was a linear decrease as feeding frequency increased (P = 0.02; Table 4). In general, heifers spent 9.9% of the day eating (4.3 and 5.6% for concentrate and barley straw, respectively); 1.8% drinking, 24.1% ruminating, 13.0% doing other activities (self-grooming, social behavior, licking, and observing), and the rest of the day (51.2%) resting or in nonchewing activities. There was no treatment x time of day interaction effect on eating time, but ruminating time tended to be affected quadratically (P = 0.06). Increasing feeding frequency produced a quadratic response in ruminating activity at interval 6 when T2 showed the greatest value, and at interval 7 when T2 showed the lowest ruminating activity (Figure 2).
|
|
). However, total daily meal time was not affected, with an average of 324 ± 27 min. Mean meal frequency and meal size were not affected by feeding frequency, whereas meal length and eating rate showed a cubic tendency (P = 0.10 and P = 0.06, respectively).
|
), the cubic effect of treatments x interval of day interaction was significant (P = 0.04), indicating that treatments affected the feed intake differently at some interval of the day. In this way, feeding frequency reduced linearly (P < 0.01) the amount of feed eaten during the first 2 h after the first morning feeding (interval 1), in which T1 tended (P < 0.10) to have greater DMI than T4 (2.45 vs. 1.69 kg of DM, respectively). In contrast, feed intake of interval 12, before the first morning feeding, increased linearly (P < 0.05), though only slightly from 84 to 174 g of DM from T1 to T4, respectively. Additionally, treatments tended to affect cubically the DMI during interval 2 (P = 0.06). A cubic effect of treatments was also observed at interval 4 (P < 0.05) where T3 had the greatest intake and T2 the lowest (P < 0.10) because this interval included the second feeding in T3. A quadratic effect of treatments was observed at interval 7 (P < 0.05) because T2 increased the intake due to the second feeding, 12 h after the first morning feeding. At this interval, the feed intakes of T2 and T1 were 1.95 and 0.71 kg of DM, respectively.
|
), the quadratic (P < 0.05) and cubic (P < 0.001) effects of treatments x interval interactions were significant. A quadratic effect of treatment was observed at interval 5 (P < 0.001) and a tendency at intervals 3 and 6 (P 
0.09). However, the treatment effect was cubic at intervals 4 and 7 (P 0.05), but it also tended to be cubic at intervals 5 and 6 (P = 0.07). At intervals 4 and 5, T2 had the smallest meal size and the biggest at interval 6, reflecting the animals’ adaptation to treatments.
|
), the cubic effect of treatments x interval interaction was significant (P < 0.001). Increasing the frequency of feeding affected cubically the meal length at intervals 1, 4, and 6 (P < 0.05), and a tendency was also observed at interval 7 (P < 0.10). Meal length in T2 at interval 1 and 4 was the shortest, and longest at interval 6.
The eating rate pattern (Figure 4c) tended to be affected cubically by the treatment x interval interaction (P = 0.07). This was the result of a cubic effect (P < 0.05) of treatments at intervals 1 (greatest for T1 and T2 and lowest for T3) and 10 (greatest for T2 and lowest for T3 and T1).
|
DISCUSSION |
|---|
|
TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
), or once daily compared with twice or 4 times daily (DeVries et al., 2005). The lack of effect of feeding frequency on DMI in the present experiment was in accordance with the lack of changes in ruminal fermentation, where no differences in total VFA concentrations or VFA proportions were observed. These findings disagree with results presented by Soto-Navarro et al. (2000), who reported that feeding steers twice daily decreased ruminal VFA concentration and increased the acetate to propionate ratio compared with feeding once daily. These authors mentioned the possible negative effect of increasing feeding frequency on the efficiency of energy utilization, which might not have happened in the present experiment, because the acetate to propionate ratio was similar among all treatments. In contrast, Klusmeyer et al. (1990) found that the acetate to propionate ratio tended to be lower when dairy cows were fed 4 rather than 2 times daily, although milk production and composition were not affected.
Feeding more than once daily might decrease the risk of acidosis (Kaufmann, 1976). However, average and lowest pH in T1 cannot be considered to be responsible for acidotic troubles in these animals consuming high-concentrate diets, confirming previous results obtained by Devant et al. (2000, 2001) and Rotger et al. (2005, 2006). In the present experiment a linear increase in pH was only found in the greatest pH, but not in average and lowest pH. In spite of these global results, the smaller range of pH values observed when heifers were fed twice daily compared with once daily indicates that it is possible to achieve more stable ruminal conditions in animals fed high-concentrate diets. In T2, the pH never fell below 6.4, and at 12 h after feeding, when the pH usually achieves the lowest pH in heifers fed once daily, rumen pH was 0.85 units greater in heifers fed twice daily compared with T1. Similar results were found in T4, in terms of average and lowest pH, but ruminal pH patterns were completely different. In contrast, there were no differences in average, lowest, and greatest pH between T1 and T3. Soto-Navarro et al. (2000) found a tendency for pH to be lower in steers fed once daily compared with those fed twice daily. In contrast, Sutton et al. (1986) and Yang and Varga (1989) reported that increasing feeding frequency in dairy cattle tended to decrease average ruminal pH, but pH fluctuation decreased. The greatest ruminal pH found in T2 at 12 h after the first feeding (interval 6) was due to the lower intakes, small meal sizes, and short meal lengths recorded in the previous intervals. The subsequent fall in the pH could be explained by the intake at interval 7, although the important ruminating activity before and after this interval might have moderated this decrease. Moreover, when daytime and nighttime ruminating activities were analyzed separately (data not shown), this activity was different in T1 (17.3 vs. 30.8%, respectively; P < 0.05) but not in T2 (21.5 vs. 28.0%, respectively; P > 0.05). No differences were found in T3 and T4 either, but in contrast no pH ruminal stability was observed. We suggest that the amount of feed eaten in these former treatments was large enough to cause a drop in rumen pH, but not large enough to maintain ruminating activity. The more stable ruminal conditions found in T2 were also confirmed with the fluctuation in ammonia-N concentration in the rumen because the mean of the differences in ammonia-N between each 2 consecutive daily sampling times was lowest in T2 (3.0, 1.6, 2.4, and 2.9 mg of N/100 mL for T1, T2, T3, and T4, respectively; data not shown).
Heifers fed less frequently spent more time observing the other heifers when the latter were fed, resulting in a decreased observational behavior as feeding frequency increased. On average, heifers spent 9.9% of the day eating, and even though barley straw only accounted for around 10% of DMI, the time spent eating straw was greater than that spent eating concentrate, which shows the importance of forage in this type of diets and, consequently, in saliva production. Daily times spent eating, ruminating, and drinking were not affected by feeding frequency and were close to the values published by Rotger et al. (2006). However, although intake was not affected by feeding frequency, feeding behavior was affected. Increasing feeding frequency resulted in a quadratic tendency in the meal criterion. However, this fact did not affect daily meal time or number of meals per day. Similarly, Phillips and Rind (2001) found no effect on daily feeding time when comparing cows fed once and 4 times daily. In contrast, our findings disagree with the results reported by DeVries et al. (2005), who found that dairy cows increased their daily feeding time with increased frequency of feed delivery. These authors attributed the discrepancy between their results and those reported by Phillips and Rind (2001) to differences in experimental methodologies and experimental conditions because the latter authors based their feeding behavior data on only 1 d of observations per treatment and the considerable within-animal day-to-day variation in feeding behavior data. However, this explanation is not valid in the present experiment, where feeding data were obtained after 5 d of observations. Because daily average meal size was not affected by treatments but eating rate tended to be affected cubically, the result was a cubic tendency in meal length. However, cause and effect between both variables may be confounded.
Significant treatment x interval of day interactions were observed in feed intake and meal characteristic patterns. First, the DMI during the 2 h following the first morning feeding was linearly reduced by 31% as the frequency of feeding increased. However, this was not accomplished by decreasing the meal size but probably by decreasing the number of meals, the length, or both. As feeding frequency increased, the length and eating rate of these meals were cubically affected in the opposite way. Treatments also had a cubic effect on the amount of feed eaten during interval 4, with T3 showing the greatest intake. Because the second feeding for T3 was at the end of interval 3, the cumulative intake was observed at the following interval. However, because these meals usually started shortly before feed was offered, which shows the animal’s adaptation to the treatment, they were often assigned by their starting time to the preceding interval. This led to treatment meal characteristics being reflected during the interval in which feeding started, but the amount of feed intake is being reflected in the interval following the feed offering. This also applies to the other treatments at other intervals. Thus, the increased feed intake of T3 at interval 4 may be attributed not only to an increase in the size and length of the meals at interval 4 but also in those meals that started in the preceding interval 3, where a tendency for a cubic effect of treatments was also reported. The quadratic effect of treatments on feed intake during interval 7 is the result of the heifers’ response to the second (T2) and third (T3) feeding, and to a lesser extent to the fourth (T4). This last feeding occurred at the end of interval 6, which was accomplished by an increased meal size and length of meals starting at interval 6 or 7. The linear and cubic decrease in eating rate at interval 1 could be a result of lower appetite or simply an adaptation of feeding behavior at the start of the daily feeding cycle as feeding frequency increased. The effect on eating rate at interval 10 could indicate that normal feeding behavior in T2 was greatly disturbed. Eating rate has been designated as a good indicator of social constraints of feeding behavior (Nielsen, 1999) or even as a response to restricted feeding (Erickson et al., 2003).
In conclusion, feeding heifers fed high-concentrate diets once daily in noncompetitive social conditions did not cause ruminal acidosis, so increasing feeding frequency did not result in any significant advantage. However feeding twice daily could be a practical way to better control the daily pH fall, reducing the range of pH values. Feeding behavior could explain this differential pattern because, although heifers spent the same time on chewing activities under all treatments, more stable ruminal conditions were probably achieved feeding twice daily due to the rumination pattern. No differences were observed in this activity between daytime and nighttime when feeding twice daily.
|
Footnotes |
|---|
2 Corresponding author: Alfred.Ferret{at}uab.es
Received for publication November 8, 2006. Accepted for publication June 29, 2007.
|
LITERATURE CITED |
|---|
|
TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
This article has been cited by other articles:
|
|
 |
|
  L. A. Gonzalez, L. B. Correa, A. Ferret, X. Manteca, J. L. Ruiz-de-la-Torre, and S. Calsamiglia Intake, water consumption, ruminal fermentation, and stress response of beef heifers fed after different lengths of delays in the daily feed delivery time J Anim Sci, August 1, 2009; 87(8): 2709 - 2718. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. M. Greter, T. J. DeVries, and M. A. G. von Keyserlingk Nutrient Intake and Feeding Behavior of Growing Dairy Heifers: Effects of Dietary Dilution J Dairy Sci, July 1, 2008; 91(7): 2786 - 2795. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
