Growth weight of females calves holstein submitted to two methods of feeding and weaning

Abstract

The growth in weight and weaning’s systems were studied in females calves Holstein variety black and white descendants of bulls which came from Canada and the United States belonging to a private ranch in Campinas, São Paulo State — Brazil. After describing the feeding and management adopted there a comparative study was made as to the growth of purebred and crossbred animals from birth to 135 days of age for the former and, until six months for the latter. The results' were submitted to a statistical analysis — t test — showing that the differences obtained were significant with exception on the birth weight the means of which were 38.09 +-0.78 kg for females calves purebred and of 37.08 +-0.53 kg for crossbred animals. Discussions were set up on the data presented by different authors and those found in this paper. Absolute growth rates were computed, having been emphasized the gains observed in both groups' studied — purebreds and crossbreds — in weaning age in relation to whole milk and skim milk. It was seen that from 60 to 105 days of age, the purebred calves were fed 400 kg of skim milk increasing 32.32 kg average weight. On the other hand, the crossbred animals, already weaned at that time, gained 26.99 kg, or better, 5.33 kg less. The difference in weight between the two groups was considered too small to justify the excess feeding of skim milk. The possible influence of the bulls on the weight of the crossbred group was studied as well, having the results been submitted to the statistical analysis. The differences were significant from birth to 105 days of age. However, due to no significant results found for the two latest ages — 120 and 135 days — it was made possible to identify the bulls, responsible for those differences in the previous ages through the t test computation. The established differences were explained using the “ instantaneous” (true) relative growth rate (kg% = 1Nw2 – 1Nw1/t2-t1 x 100)of BRODY (1945) that is, k. t2 - t l is the difference between the natural logarithms of weights W2 and W l, divided by the time interval (15 days). It was found that the “D ” and “ E” bulls lost uniformity in gains during the two latest age periods (120 and 135 days old). Two graphs show the differences found in the growth curves when plotted on the absolute and logarithm scales (weights). Before such data, it does not seem advisable to wean six month old calves, a practice very common in dairy farming in São Paulo State (Brazil). A safe method is to feed the calves 150 kg of whole milk during the first two months (90 kg during the first and 60 kg during the second) and 300 kg of the skim milk (60 kg in the first and 240 kg in the second) along with dry starters and a good legume hay.