As herd animals, cows are highly susceptible to social interactions and hierarchical order. Negative interactions may elicit behavioral changes, which if severe and prolonged, could impair immune status and lead to an elevated incidence of health disorders. "Before calving, cows should ultimately be provided with an environment that is free of stress, encourages natural behaviors and optimizes feed and water intake," noted Ricardo Chebel, University of Florida, at the Tri-State Dairy Nutrition Conference.
To optimize nutritional management, cows are often regrouped based on their stage of lactation or gestation. Oftentimes, far-off dry cows join their close-up counterparts on a weekly basis, leading to a disruption of social interaction in the days before parturition.
A study conducted by the University of Minnesota research group compared the effects of an all-in-all-out (AIAO) grouping scheme versus a weekly introduction of animals.
For the AIAO, groups of 44 cows were moved into a pen where they remained for five weeks; cows that did not calve in this window were moved into a new pen. For the control, approximately 10 cows were introduced weekly.
A greater number of displacements were observed where cows were moved weekly. However, minimal changes in feeding time were observed. Despite these slight behavioral modifications, no changes in immune and metabolic parameters were observed. Consequently, no differences in disease incidence and yield of energy corrected milk were seen.
There were 18 AIAO cows that did not calve within the window. Compared to their nonregrouped AIAO counterparts, those that moved to a second pen had greater milk yields, greater yields of fat and protein, and greater yields of energy corrected milk.
A second study evaluated prepartum-stocking density. Jerseys were housed to attain a headlock stocking density of 80 or 100 percent. Elevated densities resulted in greater average daily displacements from the feedbunk, but had minimal effects on lying and feeding times.
Immune function was not compromised at the higher stocking density. Furthermore, there was no effect of stocking density on the incidence of metabolic disorders, culling during the first 60 days in milk and the yield of energy corrected milk.
Parity makes a difference, too. When housed with mature cows, prepartum heifers are more likely to express submissive behaviors. These heifers often have a reduced feed intake and resting time prepartum and reduced milk yield compared to heifers housed alone.
Therefore, it is recommended to house first-calf heifers separately from at least 21 days before to 21 days after calving. If this isn't possible, both pre- and postcalving pens should have a stocking density below 80 percent.
The author, Amanda Smith, was an associate editor and is an animal science graduate of Cornell University. Smith covers feeding, milk quality and heads up the World Dairy Expo Supplement. She grew up on a Medina, N.Y., dairy, and interned at a 1,700-cow western New York dairy, a large New York calf and heifer farm, and studied in New Zealand for one semester.
