Abstract #333

# 333
Early lactation meal size, but not meal frequency, is positively associated with whole-lactation milk production and retention in the dairy herd.
A. J. Carpenter1, M. Wood1, B. J. Bradford*1, 1Kansas State University, Manhattan, KS.

The importance of feed intake for a successful transition to lactation in dairy cattle is frequently cited, but little is known about whether feeding patterns predict key lactation outcomes. To explore this, data from 185 cows in 4 transition studies (10 treatments) were collated for meta-analysis. Cows were housed in tie stalls for > 20 d postpartum, with continuous monitoring of feed bunk weight to determine size and duration of each meal. Unique meals were ≥ 0.2 kg DM and were separated by ≥ 12 min. Additional data collected included treatment, parity, month of calving, year of calving, time to removal from herd (only if before subsequent calving), and 305-d mature equivalent milk yield (305MEM, kg). Associations with 305MEM were assessed in mixed models with predictors tested as linear and quadratic effects, and with treatment(study) as a random effect; model selection was by minimum Bayesian Information Criterion. A similar approach was used to model risk of removal from the herd in a proportional hazards model. DMI through 20 d in milk was positively associated with 305MEM (P < 0.001), but only accounted for 10% of variation, and DMI through 20 DIM was not associated with the risk of removal from the herd. Postpartum meal length (ML) and size (MS) explained 20% and 18% of the variation in 305MEM, respectively (both P < 0.001). Backward stepwise regression generated the following model (all factors P < 0.05, model r2 = 0.53): 305MEM = 12508 + 1.71 × MilkPTA + 229 × MS – 43.5 × (MS − 5.46)2, where MS is expressed in kg DM. In contrast to these findings, meal frequency was negatively associated with 305MEM (P = 0.02, r2 = 0.03). Survival analysis revealed significant associations with 305MEM, year, parity, and ML; a 1-min increase in mean ML was associated with an 11% decrease in risk of removal from the herd (risk ratio 95% CI: 0.82–0.97; P < 0.01). Meal frequency and MS were not associated with altered risk of removal. Increased 305MEM and longer retention in the herd were associated with longer, but not more frequent, meals in the first 20 d of lactation.

Key Words: transition cow, feeding behavior, appetite