ABSTRACT The effect of a dose of GnRH administration at sponge insertion on pregnancy rate and litter size in ewes was investigated. A total of 162 pluriparous, non-lactating Huyang ewes (3–4 years old, 40–50 kg body weight, 120–150 days postpartum) were randomly and equally assigned to three groups (n = 54 each): control, G25, and G50. Estrus was synchronized using an intravaginal sponge impregnated with flurogestone acetate for 12 days, followed by an injection of 330 IU of equine chorionic […]

ABSTRACT This study examined the effect of different supplementation strategies for ewes in the last third of gestation, kept on a deferred Brachiaria brizantha cv. Marandu pasture, on their performance and the growth curve of their lambs. A total of 54 ewes, of no defined breed, with an average weight of 41.10±3.10 kg, were used in a completely randomized design, divided into three groups (18 ewes per treatment). In total, 61 lambs were born, 28 females and 33 males, with […]

ABSTRACT The objective of the present research was to determine the effect of long synchronization protocols based on reused progesterone devices (controlled internal drug release [CIDR]) associated with different doses of equine chorionic gonadotropin (eCG) on reproductive variables in crossbred sheep (Suffolk × Kathadin × Dorset). The CIDR were used for eleven days in a previous study in sheep from the same herd and were washed and disinfected before reusing. Sixty-four sheep, in the reproductive season, were randomly assigned to […]

ABSTRACT This study aimed to estimate heritability, genetic, and residual correlations between reproductive traits such as age at first calving, calving interval, dry period, and first service period and linear type traits measured in Holstein cows born between the years 1990 and 2008 in Brazil. The (co)variance components were estimated by restricted maximum likelihood, using the MTDFREML software. The heritability for reproductive traits and linear-type traits ranged from 0.02 to 0.03 and from 0.07 to 0.40, respectively. Estimates of genetic […]

It was evaluated, during a period of one year, the reproductive performance of 94 Bos taurus x Bos indicus crossbred dairy cows submitted to an assisted reproduction program. A timed artificial insemination (TAI) protocol was carried out by using an intra-vaginal progesterone device containing progesterone and through injections with Prostaglandin F2α and estradiol cypionate. By using ultrasound, from 7 to 14 days after inseminations or controlled mattings, detection of corpus luteum in the ovaries was done to determine ovulation rate […]

The aim of this study was to evaluate the influence of some environmental effects on the litter size, using 526 records of kidding of dairy crossbreed goats. The statistical analyses were carried out through generalized linear models, using a binomial distribution function and the logistic link function. The probabilities of occurrence of multiple kidding were calculated by a model that included the effects of year and month of mating, order of kidding, age at first kidding, weight at mating, milk […]

Genetic diversity among breeds of cattle allows producers to select animals for specific environments or market conditions. Reproductive efficiency is a multi-component trait that is largely influenced by environmental influences such as health and nutritional status; however, there are clearly genetic components to reproductive efficiency, and breed differences in a number of indicator traits associated with fertility and cow productivity have been identified. Historical indicators of fertility include scrotal circumference, age at puberty, and postpartum interval. Both age at puberty […]

The objective of this study was to estimate genetic and phenotypic parameters for reproductive traits of Nelore cows raised in the North and Northeast regions of Brazil. The traits studied were age at first calving (AFC), calving interval (CI), post-partum interval (PPI), number of services per conception (NSC) and gestation length (GL). The statistical analyses were done using the SAS program (Statistical Analysis System) and variance components were estimated by Restricted Maximum Likelihood method using the MTDFREML software. Means and […]

Reproduction efficiency of Holstein x Gir crossbred animals in Brazilian dairy farms were evaluated using data provided by the Brazilian Association of Girolando. A total of 2,600 records of age at first calving (IPP) and 3,763 records of calving intervals (IDP) were analyzed using the SAS® GLM procedure. Estimates of genetics effects: additive difference between Holstein and Gir breeds, dominance and additive x additive epistatic effects were obtained by regression models including genetic groups to model the performance of crossbred […]

The accumulated productivity (ACP) is an index that takes into account the total weight of calves weaned per cow (in kg), total time required for producing the calves and age at first calving. A study was conducted to estimate the components of genetic and residual variance and estimate the heritability of ACP index. Data set consisted of 2,816 observations of Nelore cows raised in different farms of the Brazilian North and Northeast. These farms participate in the Genetic Improvement Program […]