Curva de lactação e produção de leite de vacas da raça Holandesa de pequeno, médio e grande porte

Abstract

The objective of this study was to evaluate the effect of the body size composite on lactation curve (peak and persistency) and milk production in Holstein cows of first, second and third lactations. A total of 133 cows were used, selected from a herd of 280 cows, classified as small, medium and large based on the body size composite (stature x 10 + strength x 5 + depth x 3 + rump width x 2)/ 20. Data were collected from January 2007 to October 2009 in a commercial herd with intensive system of milk production, located in Salto Jacuí, Rio Grande do Sul, Brazil. Grazing oat and ryegrass, were used to feed the cows from May to October, and Tifton 85 and sorghum from November to April. Each animal received daily food supplement, with 20 kg of corn silage, and 12, 10.5 and 7.5 kg of concentrate (20% crude protein), for lots that produced 37 or more, 22 to 36, and 12 to 21 liters of milk daily per cow, respectively. All cows were subjected to the same conditions of facilities management being used and were milked three times daily. The experimental design was completely randomized with three treatments (body size). There was no interaction between body size composite and yield lactation. Peak milk production was later during the first lactation, but no significant differences were observed between the cows size. High persistency was more in second and third lactation, with increased milk production levels. Means for 305-days milk production in the lactation were 8,992.56; 9,472.33 and 10,015.50 liters for small, medium and large cows, respectively. On the basis of the total lactations, cows of medium size were more efficient than the other cow sizes, for this intensive production system.