Estimating Effects of Herd Characteristics on Milk Production in Minnesota Dairy Farms

Abstract

The objectives of this study were to estimate influence of genetic and environmental measures on herd milk production and to determine the relationship between these effects. Genetic evaluations were assessed by weighted herd PTA dollars. Environmental factors were categorized by nutrition, reproduction, and lactational health. Variables selected to represent these categories were, respectively, grain and forage DMI, days open, and percentage of herd scoring less than five on linear SCC test. A total of 3967 Holstein herds on Minnesota DHIA in December 1989 that had been on DHIA for at least 1 yr and had complete data for all selected variables were used to explain rolling herd 4% FCM. Results indicated that expected difference among herds attributable to any individual herd characteristic was dependent on levels of other herd characteristics. Both largest and smallest expected differences in herd FCM were associated with high levels of grain feeding. Largest FCM difference due to days open occurred with low genetics and lactational health. Greatest FCM differences due to genetics occurred with high days open in healthy herds. Greatest FCM differences between herds due to mastitis were with long days open and high genetics. At $.30/kg of FCM and selected management levels, ranges for the effect of a decrease in days open by 1 were –.57 to $1.05 per cow, an increase by 1 PTA dollar from 2.28 to $4.17 per cow, 1 kg increase in grain DMI .13 to $.17 per cow, and a decrease by 1 in percentage of cows infected with mastitis 6.72 to $8.97 per cow. © 1991, American Dairy Science Association. All rights reserved.