Milk

I m p a c t of Social D i s o r g a n i z a t i o n on Behavior, M i l k Y i e l d , and B o d y W e i g h t of D a i r y Cows I W. J. BRAKEL and R. A. LEIS 2 Department of Dairy Science
Ohio Agricultural Research and Development Center

Wooster 44691, and
The Ohio State University Columbus 43210

ABST RACT To measure the effect of intergroup transfer, four cows were added to a group of 20cows 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, and28. 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 withnumber of agonistic encounters per se. After day 1 regrouping had no effect on milk yield. INTRODUCTION Housing and feeding dairy cows in groups instead of individually can reduce the capital investment and improve labor efficiency. Feeding concentrates by group compared to feeding individually in the milking parlor has the additional advantage of not restricting the concentrate intake of thehigher producing cows to the quantity which can be consumed during the limited time they are in

Received September 5, 1975. I Journal Article No. 105-75, Ohio Agricultural Research and Development Center. 2Kla-Nol Acres, Box 296, Farmersville, OH 45325.

the milking parlor. The potential advantages of maintaining dairy cows in groups and the possibility of grouping them according to their milkyield become relatively greater as the number of cows per herd increases. Consequently, as herd size in the USA has increased, adoption of this system of handling dairy cows has accelerated rapidly. When cows are grouped on milk yield, intergroup transfer of cows is necessary periodically to minimize the difference in milk yield within groups, but regrouping disrupts the social order of the groupuntil the additional cows have found their positions in the dominance hierarchy. Remarks have indicated that frequently cows, when transferred to another group in the middle or latter part of the lactation, decrease drastically in milk yield as a result of social disorganization (3, 11, 15). Concern for the effect of intergroup transfer has been a deterrent to grouping cows on milk yield (3, 15).However, limited experimental and field data are available either to assess accurately the gravity of the loss or to indicate the relative importance of a reduction in nutrition and the disruption of the social order in respect to the loss in milk yield. Dominance order was reported in cattle by Woodbury (16) and referred to as hook or bunt order. The development and maintenance of a socialhierarchy in domestic animals involves the sensory organs plus a recognition and memory of individuals (14). Guhl (8) reported that former flockmates failed to recognized each other after chickens had been separated for more than 2 wk. The agonistic behavior of dairy cattle and the types of encounters which can be used to determine rank in the social order were described in detail by Schein andFohrman (12) and Guhl and Atkinson (9). In respect to the effect of intergroup transfer of cows, Schein et al. (13) reported that the addition of 35 semi-strange heifers and dry 716

INTERGROUP TRANSFER OF COWS cows to a group of 15 lactating cows caused a 5% decrease in milk yield. Arave et al. (2) also observed that persistency of milk yield declined 5% in one of their two trials when cows were...