No abstract

ABSTRACT. Given the important role of leptin in metabolism, we looked for a possible association of leptin and leptin receptor polymorphisms with carcass and growth traits in Nellore cattle. We examined associations of leptin and leptin receptor SNPs with ultrasound carcass (longissimus dorsi muscle area (ribeye area), backfat thickness and rump fat thickness and growth traits (weaning weight adjusted to 210 days of age, yearling weight adjusted to 550 days of age, weight gain of weaning to yearling and scrotal circumference adjusted to 550 days of age) of 2162 Bos primigenius indicus (Nellore) animals. Allele and genotypic frequencies were calculated for each marker. Allele substitution, additive and dominance effects of the polymorphisms were also evaluated. Some alleles of the molecular markers had low frequencies, lower than 1%, in the sample analyzed, although the same polymorphisms described for B. p. taurus cattle were found. Due to very low allelic frequencies, the E2JW, A59V and UASMS2 markers were not included in the analysis, because they were almost fixed. E2FB was found to be significantly associated with weight gain, ribeye area and backfat thickness. The promoter region markers, C963T and UASMS1, were also found to be significantly associated with ribeye area. T945M was significantly associated with weight gain. We conclude that the leptin and receptor gene markers would be useful for marker-assisted selection.

Genetic parameters, genetic trends, and genetic progress of carcass traits were estimated for 12,447 Nellore individuals from different Brazilian herds. The following carcass traits were analyzed: visual body scores of conformation (CONF), precocity (PREC), and muscularity (MUSC); rump width (RW) and rump length (RL), body size (frame); and ultrasound evaluation of ribeye area (REA), backfat thickness (BFT), and rump fat thickness (RFT). Heritability estimates (± SE) for CONF, PREC, and MUSC were 0.23 ± 0.02, 0.33 ± 0.03, and 0.31 ± 0.02, respectively. The heritability estimates (± SE) for RW, RL, and frame were 0.25 ± 0.05, 0.16 ± 0.04, and 0.31 ± 0.03, respectively. Ultrasound of the REA, BFT, and RFT presented mean heritability estimates (± SE) of 0.38 ± 0.03, 0.44 ± 0.04, and 0.47 ± 0.04, respectively. The visual body score of CONF had high genetic correlations with RW, RL, and frame (0.74 ± 0.09, 0.82 ± 0.08, and 0.83 ± 0.04, respectively), indicating a high association of CONF with the measurements related to body structure. The REA had no correlation with BFT and RFT (-0.09 ± 0.04 and -0.03 ± 0.04, respectively) and showed only a moderate genetic correlation with MUSC (0.39 ± 0.05). The BFT and RFT had moderate genetic correlations with PREC (0.36 ± 0.07 and 0.29 ± 0.07, respectively) and no correlation with frame (-0.02 ± 0.03 and 0.05 ± 0.05, respectively), suggesting that selection for frame had no effect on the subcutaneous fat content of the carcass. Low genetic trends and low genetic progress were obtained for REA (0.026 cm, 0.02%), BFT (0.0031 mm, 0.05%), and RFT (0.0013 mm, 0.02%), with no significant values of genetic progress detected throughout the studied period. The CONF, PREC, and MUSC presented high genetic trends (0.030 points, 0.030 points, and 0.029 points, respectively) and high genetic progress (0.60%, 0.56%, and 0.59%, respectively), indicating a significant genetic progress for these traits throughout the evaluated period. Carcass traits evaluated by ultrasound and visual body scores are eligible for selection and can be used in genetic improvement programs in Nellore cattle; however, visual body score selection for carcass traits can result in slower genetic progress for carcass quality when compared to selection performed by ultrasound.

ABSTRACT. We analyzed single nucleotide polymorphisms in calpain, leptin, leptin receptor, and growth hormone receptor genes and their association with color, drip and cooking losses of longissimus muscle at 7, 14 and 21 days postmortem in 638 purebred Nellore bulls slaughtered between 22 and 26 months of age. Meat samples were vacuum-packed and aged at 4°C. The single nucleotide polymorphisms T945M, GHR2, E2FB, and CAPN4751 were evaluated. All genotypic classes were observed; however, the T/T genotype of T945M and E2FB was found at a low frequency. A significant association of E2FB with drip loss (a measure of water-holding capacity) was detected at seven days of meat aging. CAPN4751 had an additive effect on red and yellow color intensities. The T allele of CAPN4751

The objective of this study was to determine the effects of vacuum-cooled liquid nitrogen on the development