57
Calf growth and feed intake associations with milk yield
This study’s objective was to understand the association between heifers’ growth and feed intake traits with cow milk yield. Data from 197 Holstein calves from six trials of varying lengths conducted at Pennsylvania State University between 2003 and 2010. Calf hip height, starter feed intake, and BW were measured for periods that ranged from 4 to 8 weeks. Calves were split into high, medium, and low ranking groups according to their hip height, starter feed intake, BW, and growth rate. Heifer calf data was merged with lactation milk yield data. A total of 134,469 daily milk records were evaluated using mixed model methodology. The model fitted age at calving group, treatment within trial, parity, lactation number, and calf groups as fixed effects and cow and calendar week by year as random effects. During lactation weeks 1 to 5, cows from the intermediate weight calf classification produced 5.0 ± 2.34 kg and 5.6 ± 2.16 kg more milk than cows from the light (P = 0.03) or heavy (P = 0.009) weight calf classifications, respectively. During lactation weeks 6 to 10, cows from the intermediate weight calf group produced 4.6 ± 1.99 kg and 3.8 ± 2.14 kg more milk than cows from the heavy (P = 0.02) and light (P = 0.07) weight calf classifications, respectively. Cows from the low hip height calf group tended to produce 4.2 ± 2.22 kg and 6.0 ± 2.10 kg milk less when compared to cows from the high (P = 0.06) and intermediate (P = 0.004) hip height calf groups in weeks 1 to 5 of lactations, respectively. Additionally, during lactation weeks 6 to 10, cows from the low hip height calf classification produced 4.2 ± 2.07 kg milk less than cows from the high hip height calf classification (P = 0.04). However, for lactation weeks 10 to 20, there were no milk yield differences (P > 0.10) for cows when classified for calf hip height and body weight. No significant milk yield differences were observed for starter feed intake and growth rate among cows from the different hip height and body weight groupings (P> 0.10). Results suggest that calf hip height and rearing body weights could be used as indicators for milk yield later in life.
Keywords:
Body Weight, Hip Height, Milk Yield