ABSTRACT The objective of the study was to characterize differences in the time to onset of puberty and reproductive variables between East Friesian and Corriedale ewe lambs in an extensive pastoral system. The study was carried out for two consecutive years, and 73 pure-breed ewe lambs were evaluated (35 East Friesian and 38 Corriedale). Plasma progesterone was determined weekly between 4.5±0.5 and 7.2±0.5 months old. The time to onset of puberty was assumed when the progesterone levels were ≥0.6 ng/mL […]

The objective of this study was to determine the main causes of failure in bull breeding using a soundness evaluation in Rio Grande do Sul State/Brazil. We evaluated 19,836 bulls from 15 different breeds with ages ranging from two to eight years. The failures of bulls in each step were analyzed by logistic regression. The binary logistic regression was applied because the response variable had only two responses: Success (1) and Failure (0). Older bulls are more likely to be […]

In this study we examined the effects of the maternal age on the fecundity (absolute and relative), egg production, and fertilization rates of Nile tilapia (Oreochromis niloticus). Females were divided into three groups: Group 1 (6 years old), Group 2 (3 years old), and Group 3 (8 months old). Males of eight months were used in all groups. Twice a week, the females’ mouths were examined, and if they had eggs, these were removed and transferred to 2-L incubators. No […]

The objective of this study was to estimate the genetic, phenotypic and environmental parameters for calving interval (CI), days open (DO), number of services per conception (NSC) and conception rate (CR) in Holstein and Jersey cattle in Antioquia (Colombia). Variance and covariance component estimates were obtained by an animal model that was solved using the derivative-free restricted maximum likelihood method. The means and standard deviations for CI, DO, NSC and CR were: 430.32±77.93 days, 127.15±76.96 days, 1.58±1.03 services per conception […]

The objective of this study was to evaluate the influence of the ovulatory follicle diameter on the reproductive performance of lactating beef cows subjected to low progesterone fixed-time artificial insemination (FTAI) protocols. Ninety-three lactating beef cows (60-80 days postpartum) at random stages of estrous cycle were given a luteolytic dose of prostaglandin F2α (500 μg cloprostenol; PGF) twice, 11 d apart. Ten days after the second PGF treatment, cows were given 1.5 mg of estradiol benzoate im and a progesterone-releasing […]

This study investigated the effect of different photoperiods (24 h of light (L):0 h of darkness (D); 20L:4D; 16L:8D; 12L:12D; and 8L:16D) on the reproduction and growth of Betta splendens. The results showed that spawning frequency was significantly higher in couples reared under 16L:8D and 12L:12D, in comparison with other treatments. The highest number of eggs per spawn was obtained under 16L:8D (544.76±375.23) and 12L:12D (471.13±261.52), and the lowest values were detected for 24L:0D (128.55±58.14) and 20L:4D (187.87±103.84). Fertility and […]

It was evaluated the bioeconomic impact of the breeding soundness evaluation on beef cattle production in southern Brazil. Two similar production systems, with and without the use of breeding soundness evaluation, were compared during 4 years in the municipality of Júlio e Castilhos. The rate of unsound bulls in the first examination was 22.8%. By performing the examination, calf production increased by 31%, 13.8 calves/bull/year and 24 kg of calves/cow/year. The benefit/cost ratio on the investment with the breeding soundness […]

The knowledge of the importance of nutrition on animal reproduction is well known for producers and researchers for a long time. However, contemporary studies have brought new perspectives and further details of this relationship, allowing fine-tuning of diets handling in order to increase production and reproduction in ruminants. Nevertheless, especially in high-producing dairy cows, there are still serious multifactorial fertility problems, with a heavy nutritional involvement. In contrast, addition of certain ingredients to the diet, such as fat rich in […]

The objective of this work was to study the relation between two reproductive potential evaluation methods – Andrologic Evaluation by Points – CAP and sexual behavior of Nelore bulls, and to verify the accuracy of these tests in predicting the reproductive potential of bulls through the gestation rate at the end of the breeding season, with average duration of ninety days. Fourteen bulls were used, all classified as able for reproduction, evaluated through andrologic examination, being submitted to CAP and […]

Records from 14,918 Nellore animals born from 1991 to 2000 in 28 herds in the South and Southeast regions of Brazil were used to estimate (co)variance components and genetic parameters for weaning weight (WW), yearling weight (YW), weights at 18 month of age (WAY) and at first calving (WFC), age at first calving (AFC) and days to first calving (DC). Multivariate animal models were fitted by REML. Estimates of heritability for WW, YW, WAY, WFC, AFC and DC were 0.26; […]