Precision livestock production (PLP) is the augmentation of precision agriculture (PA) concepts to include all components of agroecosystems, particularly animals and plant-animal interactions. Soil, plants and soil-plant interactions are the subjects of PA or site-specific farming, where the main principle is to exploit natural spatial heterogeneity to increase efficiency and reduce environmental impacts. For the most part, PA has been studied and developed for intensive cropping systems with little attention devoted to pastoral and agropastoral systems. PLP focuses on the […]

The objective of this study was to evaluate alternatives for modeling the age of dam at calving (AOD) effect on the weaning weight of Charolais-Zebu crossbred calves. Data from 56,965 calves were analyzed, using statistical models considering the fixed effects of the contemporary groups, sire and dam genetic groups, and AOD. The AOD effect was fitted to models using annual age classes, and ordinary quadratic to quintic-ordered polynomials (OP) or segmented polynomials (SP) with two, three, four, six and twelve […]

The objective of this study was to evaluate the relation between the physical and morphological characteristics of semen from Bos taurus taurus and Bos taurus indicus cattle, the age of the bull and semen collection periods. Observations were made on 42 bulls with ages ranging from 12 to 174 months in five classes: subspecies Bos taurus taurus – 12 to 36 months; 37 to 60 months, 61 to 84 months, 85 to 108 months and 109 to 138 months and […]

The objective of this study was to evaluate the effect of the European and Zebu age of the bull and semen collection periods on the physical and morphological characteristics of the semen produced by animals in an artificial insemination station, from 1993 to 1999. The semen production data were grouped in five age classes: 12 to 36 months, 37 to 60 months, 61 to 84 months, 85 to 108 months and 109 to 142 months; and in four collection periods: […]

The objective of the present study was to determine the possible use of heifer pregnancy at 16 months (HP16) as a selection criterion and its possible genetic associations with weaning weight (WW) and average daily gain from weaning to yearling (ADGWY). Covariance components were estimated by uni and bivariate animal models assuming a linear model for weaning weight and average daily gain from weaning to yearling and a nonlinear for HP16. Variance components and breeding values were estimated using Bayesian […]

The aim of this experiment was to evaluate the effect of the duration of progestagen (P4) exposure and sexual maturity of prepubertal and pubertal heifers submitted to timed artificial insemination (TAI). A hundred and fourteen 16- month old Bradford heifers were classified, according treatment and sexual maturity, in 4 groups: PPLPG (prepubertal long exposure to P4, n=21), PPSPG (prepubertal short exposure to P4, n=19), PLPG (pubertal long exposure to P4, n=34) and PSPG (pubertal short exposure to P4, n=40). On […]

A simulation study was carried out to apply and compare an alternative mating strategy for increasing the probability of producing outstanding animals and reducing progeny variability, with other conventional strategies. Fifty populations were simulated, each containing 4,800 dams, 160 sires and 4,800 calves. For each dam and sire, a random variable from a normal distribution was generated, mimicking an index composed by several expected progeny differences (EPD). The mating strategies considered were: (1) random mating (RM); (2) positive assortative mating […]

The objectives of this study were to estimate the genetic parameters of the following categorical traits: musculature, physical structure, racial breed aspects, conformation, navel, pigmentation and sacrum, and predict breeding values, using bayesian statistics under threshold animal models, considering different ages of cattle of the Nelore breed. The information concerning visual scores were obtained from 2000 to 2005 from cattle of the Nelore breed from thirteen participant farms of the Brazilian Nelore Program. In the two-trait analyses, 500,000 rounds up […]

Yields of B. decumbens cultivar Basilisk and B. brizantha cultivars Marandu and Xaraés were evaluated under different shade levels. A completely randomized block split plot design was used, with the shade levels as plots (0, 50, 70%), and the species and cultivars as split-plots. Seeds were germinated on trays and three seedlings were transplanted to each pot. Four harvests were made on each split-plot. Prior to each harvest, plant height, number of live tiller per pot and the leaf area […]

Nitrogen (N) at 100, 200, 300, and 400 kg ha-1 was applied to Tanzania grass swards to evaluate the animal response and relationships between sward characteristics and the performance of young Nellore bulls (Bos indicus) under continuous stocking. A completely randomized experimental design was used with two replications between 11 November 2001 and 15 April 2002 when the sward heights were maintained at 60 cm by using different stocking rates. The average daily gain (ADG) (0.73 kg d-1) was not […]