Effect of change in body condition, breed and parity on the performance of dairy cows

This study was carried in the central area of El Salvador with the aim of knowing the behavior of the body condition, the blood urea and cholesterol and to determine the relationship among the postpartum body condition loss, genetics and parity in reproductive parameters of dairy cows. For this 40 Holstein and 40 crossbred (Holstein/Brown swiss/zebu) prepartum cows were used. Body Condition Score was measured and milk and blood samples was taken every two weeks since 45 days prepartum to 56 days postpartum, information was obtained from the number of births and reproductive events. Milk progesterone were determined using solid phase radioimmunoassay and the serum urea nitrogen and cholesterol was measured by espectofotometry. The pospartum body condition loss was higher in Holstein cows (0.93 +/- 0.49) than in crossbred cows (0.65 +/- 0.51). The length of anestrus was higher in Holstein cows (63.8 +/- seven days) than in crossbred cows (37.24 +/- six days) p <0.05, and in cows with greater loss of body condition > 1 (63.67 +/- 36 days) than in cows less lost 0.5-1 (46.4 +/- 24.42 days), <0.5 (36.7 +/- 15.7 days) p <0.05. The effect of BCS, genetics or parity in the services per conception or in the open days was not significant. It is concluded that the genetic Holstein and loss of body condition relate negatively with the length of anestrus.