Milk yield of a Holstein herd in the high area of venezuelan Andes

Abstract

A total of 1717 observations of milk yields was analyzed to evaluate the productive potential of a Holstein flock, located in the high area of the Venezuelan Andes at 2050 m.o.s.l., with humid forest and an annual averaged rainfall and temperature of 1800 mm and 15 ºC’s, respectively. The sample object of the study is descendent from animals imported from 1970 to 1980. AI is a common practice, only 10% of used bulls came from their own herd. During the study, animals shepherded freely in pens of one thousand m2’s of Pennisetum clandestinum, rotating into two pens daily, and while milking they were supplemented with concentrated in a ratio of 1 kg^-1 2.25 kg of milk yield, and 50 g’s of a commercial mixture of minerals per cow. The weekly daily average (PDS) of milk yield from 1998 to 2000 was analyzed by means of the "Proc Mixed" of SAS, under a statistical model that included the fixed effects of season: combination of month x year of calving; parity; week after calving at which the averaged correspond; and bull and dam as random effects. All effects were statistically significant with P<0.01. The average was 26.4 ± 0.12 for PDS and of 7948 ± 84 for extended yields at 305d. The observed values are above those reported for pure European groups in tropical environments. The estimate of h^2 was 0.35 and there was no statistically significant difference between the average breeding value of local bulls vs imported semen. The results are indicative of the necessity to evaluate and to select reproducers locally. The continuous use of imported semen can dilute the genetic progress accumulated in favor of the adaptation.