Impact of social disorganization on behavior, milk yield, and body weight of dairy cows

To measure the effect of intergroup transfer, four cows were added to a group of 20 cows at 28-day intervals in five trials. The two groups of cows were housed in adjoining lots and fed identical rations from opposite sides of a feed bunk which provided .9 m linear feeding space per cow. Means of the number of agonistic encounters per transferred cow were 9.4, 4.4, 4.3, 3.8, 3.3, and 2.6 during the 1-h period immediately following the first feeding on days 1, 2, 7, 14, 21, and 28. The average dominance values of the transferred cows during the 28 days (.19, .14, and .32) showed no perceptible trend, and mean body weight (567, 569, and 571 kg) was not limited. On day 1 the mean 4% fat-corrected milk yield of the transferred cows decreased .51 kg or 3%, and nontransferred cows increased .01 kg. The decrease in milk yield of the transferred cows was not associated with number of agonistic encounters per se. After day 1 regrouping had no effect on milk yield.