Effects of within dyad weight variation on competition, feed intake, and milk production of dairy cows sharing feeding gates
The goal of this study was to identify the effect of weight variation in cow pairs on animal performance and ingestive behavior under competitive conditions. Twenty-four primiparous and 36 multiparous lactating cows were paired (within parity) to form 30 experimental units (feeding gates). Pairs were fed 6 diets in five 6 × 6 balanced Latin squares with 21-d periods, using data from the last 5 d. Each pair had access to one gate that allowed one animal to eat at a time, and cows that filched feeds in other gate were excluded during the statistical analysis. Each dyad was categorized based on the difference in weight within dyad. Differences above average (60 kg) were categorized as High. Below average differences in size were categorized as Low. Within cow pair, individual animals were classified by size as either the larger animal in the pair (Large) or the smaller animal in the pair (Small). The effect of size (large/small) and difference (high/low) were tested. For High and Low difference pairs the number of displacement (gate exchange < 1 min) per week were 55.79 and 90.38 per week, respectively (P<0.05). An interaction between size and difference was significant for dry matter intake, feeding rate, displacements and milk yield, (P< 0.05). In High differences, small cows had greater DMI (% BW) compared to large cows (P<0.05). In Low difference pairs, size did not impact DMI. Milk yield was 4.4 ± 1.1 kg/d lower for Small cows compared to Large cows (P<0.05). For High difference pairs, Size was not associated with milk yield (P>0.05). These results suggest that in highly competitive situations, cows close in size have more aggression, poorer welfare, and milk production than animals with a greater difference in weight. This has implications for identifying animals with poor welfare in competitive environments.
Keywords: animal behavior, competition, performance