Evaluation Of Reproductive Traits Research Articles

Evaluation of reproductive traits and the effect of nutrigenetics on bulls submitted to fetal programming

Nutritional stimuli during the gestational period in dams have long-term effects on the offspring in terms of health and production rates. This study assessed the effect of fetal programming in 126 pregnant Nellore cows on reproductive and nutrigenetic traits of the progeny during the rearing phase. For that purpose, three nutritional treatments were used in these cows during pregnancy: PP – protein-energy supplementation in the final third, FP – protein-energy supplementation during the entire pregnancy, and NP – (control) only mineral supplementation. The male progeny (64 bulls) was evaluated for scrotal circumference and seminal traits at 12, 15, and 18 months of age. In addition, we performed a genomic association (35 K SNPs) for scrotal circumference at 12 and 18 months of age. Only the total sperm defects showed significant difference between groups (P < 0.05), regardless of age, while major and minor sperm defects and vigor showed tendencies (P < 0.10). In the time analysis, only the minor sperm defects did not differ between ages, regardless of treatment (P = 0.92). We found genes that are associated with genetic variance at different ages and treatments (BTBD9, WNT2, ASZ1, WWOX and SLC26A8). Thus, prenatal protein-energy supplementation showed effects on the total of abnormal sperm cells between treatments, genotype-environment interaction, and some SNPs that explain more than 1% of the genetic variance on bulls during the rearing phase. These are evidences that different strategies of prenatal supplementation may have acted on epigenetic factors and may have caused changes in gene expression of animals. This contributes to the knowledge about mechanisms that involve fetal programming in beef cattle.

Evaluation of reproductive traits in Bos taurus and Bos indicus crossbred heifers: relationship of age at puberty to length of the postpartum interval to estrus.

Records of age at puberty (AAP) and duration of the postpartum interval to estrus (PPI) for heifers calving first at 2 yr of age were used to determine the relationship between the two reproductive traits. The study from which these records were obtained was designed in a 2 x 2 x 2 factorial arrangement of treatments. Angus x Hereford (AH; n = 148) and Brahman x Hereford (BH; n = 148) heifers were allotted within breed after weaning by weight into light (LW) and heavy (HW) weight blocks. Heifers were assigned by age to different levels of energy (low or high) in diets calculated to reach a target weight of 55% (LE) or 65% (HE) of their projected mature weight by the onset of the breeding period. Data were analyzed within breed and included only records for which both AAP and PPI were available. Pearson correlation coefficients for AAP to PPI were r = -.12 (P = .20) and r = .05 (P = .71) for AH and BH, respectively. Eliminating animals that experienced dystocia from the analyses yielded correlations of r = -.27 (P = .02) and r = .06 (P = .65) for Ah (n = 69) and BH (n = 51), respectively. When energy level, weight block, and energy level x weight block were included in the model for PPI, analyses of variance indicated that PPI among AH heifers was influenced most by the weight at which heifers began the trial after weaning (P = .01) but not by energy level (P = .23) or the interaction of energy level x weight block (P = .48).(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of reproductive traits in Bos taurus and Bos indicus crossbred heifers: effects of postweaning energy manipulation.

Reproductive traits were evaluated in Bos taurus and Bos indicus crossbred heifers that were fed different diets during the postweaning period. The study was designed in a 2 x 2 x 2 factorial arrangement of treatments. Angus x Hereford (AH; n = 148) and Brahman x Hereford (BH; n = 148) heifers were sorted after weaning by body weight into light (LW) and heavy (HW) weight blocks. Heifers in each weight block were assigned to diets calculated to reach a target weight of 55% (LE) or 65% (HE) of their projected mature weights by the start of the breeding season. Puberty was determined after a 160-d observation period and characterized by the following criteria: 1) behavioral estrus, 2) presence of a palpable corpus luteum (d 6 to 10; estrus = d 0), and 3) rise in serum progesterone above 1 ng/ml (d 6 to 10). A higher (P = .01) proportion of AH heifers than of BH heifers reached puberty by the breeding season (93% vs 67%). Interactions of breed x weight block and energy level x weight block also contributed to this difference. Weight at puberty was heavier (P = .001) among HE than among LE heifers and greater for heifers in HW than for those in LW blocks (P = .02). Differences in prebreeding weight, body condition, average daily gain, hip height, and pelvic area were influenced selectively by breed, energy level, or weight block. Pregnancy rates were higher (P = .01) among AH than among BH heifers. Incidence and severity of dystocia was influenced by the breed x energy level interaction (P = .01). Brahman x Hereford heifers had less (P = .01) dystocia than AH heifers, HE heifers had less (P less than .02) dystocia than LE heifers, and HE-AH heifers had less (P less than .01) dystocia than LE-AH contemporaries. Subsequent duration of the postpartum interval to estrus was shorter (P = .002) among AH than among BH females. Pregnancy rates at the end of the 2nd yr were higher (P = .02) among LW than among HW females and weights were heavier (P = .001) at weaning among calves weaned from BH dams.