[Effect of weight changes during the growth period on the interval between the beginning of the second mating and conception for straight breed and first cross beef cattle females]
1986
Melucci, L.M.
A total of 274 records of heifers pregnant in the first two mating seasons of their lifetime were used to estimate the effect of different growth periods on the length of the interval determined by the beginning of the second service season and the following conception (CON), under extensive management systems. The animals used were purebred Aberdeen Angus (A) and Hereford (H) and F1 dams produced by mating A females with sires from different breeds: Charolais, Fleckvieh, Limousin, Marchigiana, Chianina, Romagnola, Piamontesa, Brahman, Nelore, Holando Argentino, Criollo, Hereford and the reciprocal AH. Individual absolute and relative daily weight gains and the adjusted weights to different seasons, and different reproductive and growth periods, as well as the CON were used, and they were the 39 initial variables in the principal component analysis (PC). The first 10 PC explained 83% of the variability in growth and they showed effect (P.05) of bred type, but the multiple regression analysis of CON as a function of the 39 PC of growth indicated that the higher rate of variation in CON was explained by PC31,PC3 and PC13, where PC31 described heifers with high weight at second conception, PC3 represented the rate of fetal growth in relation to dam's size and PC13 described those heifers with above average in preweaning relative gain rate but below average in the summer at 18 month of age
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