The impact of early life nutrition and housing on growth and reproduction in dairy cattle

Contentious issues in calf rearing include milk feeding practices and single versus group housing. The current study was performed on a high producing 170 Holstein cow dairy farm, to investigate the impact of nutrition and housing on growth and reproduction. Heifer calves (n = 100) were allocated in birth order to one of two commonly used management strategies. All calves received 3–4 litres of dam specific colostrum within 6 hours of birth. Group A calves were group housed from birth and fed milk replacer (MR) ad libitum via a computerised machine utilising a single teat, with weaning commencing at 63 days of age. Group R calves were initially housed in individual pens and received 2.5 litres of MR twice daily via a bucket until 21 days of age when they were group housed and fed 3 litres of MR twice daily via a group trough with weaning commencing at 56 days. From 12 weeks of age onwards, calves in both dietary groups were subject to common nutritional and husbandry protocols. All breeding of heifers was via artificial insemination with no hormonal intervention. Calves were weighed, body condition scored and morphometric measures recorded weekly up till 12 weeks of age then monthly until conception. Pre-weaning growth rates (kg/day) were significantly higher in Group A calves compared to Group R (0.89, 95% CI 0.86–0.93 vs 0.57, 95% CI 0.54–0.6 kg/day P vs 0.17, 95% CI 0.08–0.26 P 0.050) in any of the mean values of measured reproductive parameters, multivariable Cox regression suggested that there was a weak trend (P = 0.072) for Group A animals to achieve first service earlier than their Group R counterparts (62.6 weeks versus 65.3 weeks). Irrespective of dietary group, the hazard for achievement of all measured reproductive parameters, apart from time to puberty, was 20–40% less for heifers borne from multiparous dams compared to heifers from primiparous dams.

犊牛培育中的争议性问题包括哺乳方式，以及单栏与群养两种饲养模式的选择。本研究在一座高产荷斯坦（Holstein）奶牛场开展，旨在探究营养与饲养方式对后备母牛生长及繁殖性能的影响。试验选取100头后备母牛犊，按出生顺序分配至两种常用管理方案组。所有犊牛均在出生后6小时内摄入3~4升其生母源初乳。A组犊牛自出生起即采用群养模式，通过单乳头电脑饲喂机自由采食代乳粉（milk replacer, MR），于63日龄开始断奶。R组犊牛初期饲养于单栏，每日通过桶饲喂2.5升代乳粉，共2次；至21日龄时转为群养，每日通过群养料槽饲喂3升代乳粉，共2次，并于56日龄开始断奶。12周龄起，两个饲喂组的犊牛均采用统一的营养与饲养管理规程。所有后备母牛均通过人工授精（artificial insemination）进行配种，未使用任何激素干预措施。分别于12周龄前每周、12周龄后每月对犊牛进行称重、体况评分（body condition score）及体尺测量（morphometric measures），直至其妊娠。断奶前日增重（单位：千克/天）A组犊牛显著高于R组（0.89，95%置信区间0.86~0.93 vs 0.57，95%置信区间0.54~0.60；P<0.05）；而就各测定繁殖参数的平均值而言，相关指标对应值为0.17（95%置信区间0.08~0.26，P=0.050），多变量Cox回归（multivariable Cox regression）分析显示，A组后备母牛首次配种时间早于R组的趋势较弱（P=0.072），两组分别为62.6周与65.3周。无论饲喂组别如何，与初产母牛（primiparous dams）所产的后备母牛相比，经产母牛（multiparous dams）所产的后备母牛达到除初情期（puberty）时间外的所有测定繁殖指标的风险低20%~40%。