Variability in behavior and production among dairy cows fed under differing levels of competition.

The objective of this study was to investigate the effects of differing levels of competition for feed access on group-housed dairy cows, and on variations in behavior and productivity between individuals within each group. Eighteen lactating Holstein cows, averaging 77 ± 20 d in milk with a production of 46 ± 7 kg/d at the start of the trial, were divided into subgroups of 3 and fed a total mixed ration 3×/d. Groups were exposed to each of 3 competition levels: high (3 cows:1 feed bin), moderate (3 cows:2 feed bins), and low (3 cows:3 feed bins). Treatments were assigned in random order according to a modified Latin-square design, and each was applied for 10 d. Using an automated feed intake system, feeding behavior data (dry matter intake, feeding time, feeding rate, and meal patterns) were recorded for each cow on d 6 to 10 of each treatment period. Additional behavioral [sorting, rumination, competitive interactions (replacements), lying time] and production (milk yield and components) data were collected. Greater competition resulted in a reduction in feeding time (low = 202.6, moderate = 194.9, high = 183.6 min/d; SE = 8.84), and an increased rate of feed intake (low = 0.16, moderate = 0.18, high = 0.20 kg of dry matter/min; SE = 0.01), especially following fresh feed delivery and milking. Dry matter intake was similar across treatments (average of 29.1 kg/d). Meal length increased under high competition (low = 37.0, moderate = 36.6, high = 47.3 min/meal; SE = 5.05) due to greater non-feeding time within meals, which was approximately twice as long under high competition (low = 10.0, moderate = 10.8, high = 20.3 min/meal; SE = 3.24). Daily lying time (low = 10.2, moderate = 10.2, high = 9.5 h/d; SE = 0.51) and milk protein yield (low = 1.41, mod = 1.42, high = 1.36 kg/d; SE = 0.05) were reduced under high competition. Analysis of individual within-group variability, calculated as the daily standard deviation of each group, averaged across 5 recording days, revealed greater variability in feeding time, feeding rate, meal length, non-feeding time within meals, milk yield, milk fat composition (%), and milk fat component yield (kg/d) under high competition. These results suggest that at elevated competition levels, cows modify their feeding behavior to consume feed in a shorter period and devote a large portion of their mealtime toward waiting to gain feed access, resulting in reduced daily lying time. Furthermore, meal patterns and milk production vary greatly within groups of cows at high levels of competition for feed access.