Abstract：
The preweaning period for a dairy calf is characterized by high morbidity and mortality rates, leading to financial losses for producers. Identifying strategies to improve the health and welfare of calves while reducing antimicrobial use continues to be crucial to the success of the dairy industry. The objective of this study was to determine the effects of feeding colostrum replacer (CR) to dairy heifer calves beyond d 1 of life on growth, serum IgG, the incidence of diarrhea and bovine respiratory disease (BRD), and the risk of mortality in the preweaning period. At birth, Holstein heifer calves (n = 200; 50/treatment) weighing 40.7 ± 0.35 kg (mean ± SE) were fed 3.2 L of CR (205 g IgG/feeding) at 0 h and 12 h of life. Calves were then randomly assigned to 1 of 4 treatments: 450 g of milk replacer (MR) from d 2 to 14 (control, CON), 380 g of CR + 225 g of MR from d 2 to 3, then 450 g of MR from d 4 to 14 (transition, TRAN), 45 g of CR + 450 g of MR from d 2 to 14 (extended, EXT); or 380 g of CR + 225 g of MR from d 2 to 3, then 45 g of CR + 450 g of MR from d 4 to 14 (transition + extended, TRAN+EXT). Each treatment was reconstituted to 3 L and fed twice daily. All CR treatments were fed using bovine-derived CR containing 27% IgG. From d 15 to 41, all calves were fed 600 g of MR reconstituted to 4 L twice daily. Body weight was recorded at birth and every 7 d until study completion on d 49. Blood samples were taken daily until d 7 to evaluate serum IgG and then every 7 d until d 49. A health assessment was performed daily to evaluate calves for BRD and diarrhea. Data were analyzed using mixed linear regression, mixed logistic regression, and survival analysis models in SAS 9.4. Serum IgG concentrations were not affected by treatment for the study period. The EXT and TRAN+EXT groups had greater average daily gain (ADG) from d 7 to 14 (0.14 kg/d) and the TRAN group had greater ADG from d 14 to 21 (0.11 kg/d), compared with CON. There was no association of treatment with the odds or the duration of a diarrhea bout. However, provision of CR to the TRAN and EXT calves was associated with a reduced hazard of diarrhea compared with CON calves. Furthermore, TRAN and EXT calves have a lower hazard of mortality compared with CON calves, with TRAN and EXT calves had a 2.8- and 3.8-times lower hazard of mortality, respectively. Our findings suggest that the supplementation of CR to dairy calves positively affects ADG, and reduces the hazard of diarrhea and mortality during the preweaning period. Future research should look to further refine the supplementation strategy of CR to calves and explore the mechanism of action.
摘要：
乳牛断奶前期的特点是发病率和死亡率高，导致生产者的经济损失。确定改善小牛健康和福利的策略，同时减少抗菌药物的使用仍然是乳制品行业成功的关键。这项研究的目的是确定饲喂初乳替代品（CR）对超过生命d1的乳牛小牛对生长的影响，血清IgG,腹泻和牛呼吸道疾病（BRD）的发病率，以及断奶前死亡的风险。出生时,体重40.7±0.35kg（平均值±SE）的荷斯坦小母牛（n=200；50/处理）在生命的0h和12h分别饲喂3.2LCR（205gIgG/饲喂）。然后将小牛随机分配到4种治疗方法中的1种：从第2天到第14天450克牛奶替代品（MR）（对照，CON),从d2到3的380gCR+225gMR，然后从d4到14的450gMR(过渡，TRAN),从第2天开始到第14天的45克CR+450克MR(扩展，EXT）；或从d2到3的380克CR+225克MR，然后从d4到14的45克CR+450克MR（过渡+扩展，TRAN+EXT)。将每种处理重建为3L并每天喂食两次。所有CR处理使用含有27%IgG的牛来源的CR饲喂。从第15天到第41天，每天两次饲喂所有小牛600g重组为4L的MR。出生时和每7天记录体重，直到第49天研究完成。每天采集血样，直到第7天，以评估血清IgG，然后每7天，直到第49天。每天进行健康评估以评估小牛的BRD和腹泻。数据采用混合线性回归分析，混合logistic回归，和SAS9.4中的生存分析模型。血清IgG浓度不受研究期间治疗的影响。EXT和TRAN+EXT组的平均日增重（ADG）从第7天到第14天（0.14kg/d）较大，TRAN组的ADG从第14天到第21天（0.11kg/d）较大，与CON相比。治疗与腹泻发作的几率或持续时间无关。然而,与CON小牛相比,向TRAN和EXT小牛提供CR与腹泻风险降低相关.此外，与CON小牛相比，TRAN和EXT小牛的死亡率较低，TRAN和EXT小牛的死亡率低2.8和3.8倍，分别。我们的研究结果表明，补充CR对奶牛的ADG有积极的影响，并减少断奶前腹泻的危害和死亡率。未来的研究应进一步完善小牛补充CR的策略，并探讨其作用机制。
