Suchergebnisse

The aim was to estimate the genetic correlations between residual feed intake (RFI) and dry matter intake (DMI) with carcass finish (CF), rib eye area (REA), and marbling (MAR) of Nellore cattle. Data from 7,808 animals were considered. In addition, data from 2,261 females included in the complete database were also considered. Estimates of variance and covariance components, as well as heritabilities and genetic correlations were obtained by means of two-character analysis under animal model. Heritability estimates were found to be moderate for the RFI (0.22) and DMI (0.29) traits. It was observed that genetic correlation was close to zero for all traits, except between RFI and REA (-0.11). However, considering the female population, there was an increase in the estimated genetic correlation between RFI and DMI, although still a favorable genetic association of low magnitude (-0.30). There was also an increase in the genetic association of REA with RFI (-0.21). It can be concluded that the direct selection for RFI and DMI will not influence the CF, MAR, or REA of Nellore cattle. However, this selection may generate some favorable responses in MAR and REA in Nellore females.

We aimed to evaluate the effects of using a concentrated ration containing industrialised human food on the productive parameters of Nellore heifers in confinement, in addition to comparing the dry matter intake (DMI) observed with that predicted by the nutritional systems BR-Corte and NRC, in order to determine which system makes the most accurate predictions for heifers of the breed Nelore in feedlots. Twenty-four Nelore heifers, with an average age of 24 months and average body weight (BW) of 350 kg, were used over the 70 days of the experiment. They were randomly assigned to two treatments and housed in partially covered stalls equipped with an automatic Growsafe® Systems feeding system. Animals in the control group (CONT) received a concentrated ration containing ground corn, soybean meal, urea, and mineral nucleus. In the residual treatment (RES) group, heifers received concentrated feed containing products from the human diet. The difference between the treatments was the concentrated ration; in the control treatment, the energy source used was maize, whereas in the residue treatment, the energy sources were corn chips, coconut candies, and ground coffee. Corn silage was included as forage for both treatments. The forage:concentrate (F:C) ratio was 84:16. The predicted intake was estimated according to the nutritional systems NRC (2000, 2016) and BR-Corte (VALADARES FILHO et al., 2010, 2016). The average DMI observed of the heifers was 7.46 kg day-1. Heifers fed with human feed residue had a higher dry matter intake (DMI) and higher ether extract intake (EEI) than animals fed with the control feed. In addition, heifers that received human feed products showed a lower average daily weight gain (DWG) of 1.08 kg day-1 than animals fed the control treatment with an average DWG of 1.24 kg day-1. The predicted dry matter intake by NRC 2000 was an overestimate by 9.78 % and by BR-Corte 2010 was an overestimate by 5.5 %. The NRC 2016 and BR-Corte 2016 underestimated the intake of heifers by 18.9 % and 7.1 %, respectively. It was concluded that growing Nelore heifers fed with human feed products, with a F:C ratio of 84:16, present a higher DMI and lower growth performance and feed efficiency than heifers fed the control diet. The DMI predicting models for Nellore heifers proposed by BR-Corte are more adequate than the NRC models.

Studies on reproductive tract score (RTS) and antral follicle count (AFC) in Senepol cattle are limited. These traits are essential as they are linked to the reproductive ability and reproductive performance of animals. Understanding the heritability and genetic correlation of these traits is crucial for guiding selection programs and selecting animals with greater reproductive efficiency and higher production potential. Therefore, this study aimed to estimate the genetic parameters of weight, RTS, and AFC in Senepol cattle using transrectal ultrasonography. Reproductive data were collected from 850 female Senepol cattle aged 10-16 months. At the time of evaluation, the following were measured: RTS traits (scores from 1 to 5), AFC (0 to 100), and female weight (kg). Variance and covariance components, genetic heritability, and correlations were estimated by univariate and bivariate analyses using the bull model. Heritability estimates were moderate for AFC (0.52) and weight (0.46), and low for RTS (0.12). The genetic correlation between RTS and AFC was almost zero (-0.05). The estimated genetic correlation between weight and AFC was -0.41, while the correlation between weight and RTS was 0.48. Selective breeding of AFC and RTS can enhance the reproductive efficiency of the herd and result in animals with earlier pubertal age and increased fertility.