Borderas T F, de Passillé A M B, Rushen J
Animal Welfare Program, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada.
J Dairy Sci. 2009 Jun;92(6):2843-52. doi: 10.3168/jds.2008-1886.
Little is known about feeding behavior in group-housed calves fed with an automated feeding system. To examine the influence of milk feeding level on feeding behavior in such a system, we fed calves either 4 L of milk replacer per d (LIM) or allowed ad libitum (AL) intake (n = 25 per treatment). In a second experiment another set of calves was fed 4 L (low milk volume, LM) or 12 L (high milk volume, HM) of whole milk (n = 14 per treatment). Results were analyzed separately using a mixed model including calf, treatment, and time as factors, and feeding behavior as variables. Milk intake by AL or HM calves increased during the first 2 wk, reaching a maximum intake that reached a plateau during the next 4 wk. Concentrate intake was negligible during the first 14 d, with LIM and LM calves increasing their consumption from d 22. Concentrate intake by AL and HM calves remained low until weaning in experiment 1 and the end of trial in experiment 2 (d 43 for both). The frequency of visits was higher in LIM and LM calves than in AL and HM calves during the first 42 d, with most visits being unrewarded (approximately 90%). This resulted in higher occupancy time of the feeder by LIM and LM calves. During weaning in experiment 1 (d 44 to 48), there was no difference in occupancy time between treatments. Calves in the AL and HM groups distributed their visits throughout the day, whereas LIM and LM calves made most visits just before the time when the next allowance of milk became available. In experiment 1, AL calves showed a greater weight gain during the first 21 d but LIM calves had greater gains between d 22 and 50. However, the overall average daily weight gain was higher for AL calves. In experiment 2, HM calves had a greater gain than LM calves for the first 4 wk of trial but there was no difference between treatments during the last 2 wk. There were no differences between treatments in the incidence of disease in either experiment. The duration of time spent lying down in experiment 2 was higher for HM calves but only when they were older (4 to 5 wk). No differences were found between treatments at 2 wk of age. In conclusion, feeding high levels of milk or replacer improved weight gain and reduced unrewarded visits to the milk feeder, improving the efficiency of use of the milk feeders. However, it reduced concentrate intake and the advantages were less obvious after 3 wk of age. No increased incidence of disease was found for high-fed calves (AL and HM groups). Lying time was also higher for high-fed calves but only at an older age (4 to 5 wk).
关于采用自动饲喂系统的群饲犊牛的采食行为，人们了解甚少。为了研究牛奶饲喂水平对这种系统中犊牛采食行为的影响，我们给犊牛每日饲喂4升代乳粉（低牛奶量组，LIM）或让其自由采食（自由采食组，AL）（每组n = 25头）。在第二个实验中，另一组犊牛分别饲喂4升（低牛奶量组，LM）或12升（高牛奶量组，HM）全脂牛奶（每组n = 14头）。使用包含犊牛、处理方式和时间作为因素以及采食行为作为变量的混合模型分别对结果进行分析。自由采食组或高牛奶量组犊牛的牛奶摄入量在前2周增加，在接下来的4周达到最大摄入量并趋于平稳。在最初14天，精料摄入量可忽略不计，低牛奶量组和低牛奶量组犊牛从第22天开始增加精料消耗。在实验1中，自由采食组和高牛奶量组犊牛直到断奶（实验2中直到试验结束，即第43天）精料摄入量一直较低。在最初42天，低牛奶量组和低牛奶量组犊牛的采食频率高于自由采食组和高牛奶量组犊牛，且大多数采食未得到食物（约90%）。这导致低牛奶量组和低牛奶量组犊牛在采食器处的停留时间更长。在实验1的断奶期（第44至48天），各处理组之间的停留时间没有差异。自由采食组和高牛奶量组的犊牛全天分散采食，而低牛奶量组和低牛奶量组的犊牛大多在下一次牛奶供应前进行采食。在实验1中，自由采食组犊牛在最初21天体重增加更多，但低牛奶量组犊牛在第22至50天体重增加更多。然而，自由采食组犊牛的总体平均日增重更高。在实验2中，高牛奶量组犊牛在试验的前4周增重高于低牛奶量组犊牛，但在最后2周各处理组之间没有差异。在两个实验中，各处理组之间的疾病发生率没有差异。在实验2中，高牛奶量组犊牛躺卧时间更长，但仅在它们年龄较大时（4至5周）。在2周龄时，各处理组之间未发现差异。总之，饲喂高水平的牛奶或代乳粉可提高体重增加，并减少对牛奶采食器的无效访问，提高牛奶采食器的使用效率。然而，这会降低精料摄入量，且在3周龄后优势不太明显。高饲喂量组犊牛（自由采食组和高牛奶量组）未发现疾病发生率增加。高饲喂量组犊牛的躺卧时间也更长，但仅在年龄较大时（4至5周）。
