Effect of metabolic imprinting and EPD for sexual precocity on puberty in crossbreed (Angus X Nellore) heifers weaned early

Abstract

The objective of experiment is to evaluate the interaction among metabolic imprinting from 3 to 7 month of age, expected progeny differences (EPD; genetic factor) and age on puberty of Crossbreed (Angus x Nellore) heifers. Will be used 66 crossbreed heifers Angus x Nellore (Bos Taurus taurus x Bos taurus indicus) weaned at three months old, coming from fixed time artificial insemination (FTAI), daughters of 5 bulls (2 positive EPD and 3 with negative EPD to sexual precocity ; estimated by scrotal circumference according to the American Angus Association). These heifers will be divided into two groups, one with high average daily gain (HG; 1000 g / animal / day; n = 33 heifers) and one with low average daily gain (LG; 500 g / animal / day; n = 33 heifers). Formed factorial in 2x2, in which the factor 1 is the EPD bull and factor 2 is GMD, thus forming four treatments: EPD positive and high average daily gain (PHG); EPD positive and low average daily gain (PLG); EPD negative and high average daily gain (NHG); EPD negative and low average daily gain (NLG). Once a week heifers will be weighed and, starting at 230 kg, underwent ultrasonography to monitor puberty. Once a month will be held blood collection for IGF-1 analysis, as well as a collection on D0 and on day that heifer is diagnosed with a corpus luteum (CL). It will be used completely randomized design, with the treatments arranged in a factorial 2 x 2 (factor 1 - EPDs of bulls for sexual precocity, factor 2 - Average daily gain). Continuous variables will be analyzed by MIXED procedure and the variables with binomial distribution will be reviewed by GLIMMIX procedure, both procedures of statistical package SAS 9.3. (AU)