Temperamento, comportamento ao parto e desempenho de bovinos de corte de diferentes genótipos

Abstract

The objective of this study was to investigate the effect of crossbreeding on temperament, behaviour and performance at calving from extensively raised beef cattle. The study was conducted in two activities: the first involved purebreeds and crossbred at weaning and yearling. To assess the temperament we used flight speed - FS. The animals evaluated was born from Aberdeen Angus (AN), Hereford (HH) and Nellore (NE) cows, crossed with bulls AN, HH, NE and Caracu (CR). The temperament was measured at two times (weaning and yearling) as well live weight. Was no difference between FS and genotypes (p <0.05). There was no difference between the weights at weaning and yearling according temperament. Females were more reactive than males without, however, vary for weaning or yearling weight variables. There was a positive correlation between weaning and yearling weights and measurements between temperament, showing that heavier at weaning animals are heavier yearling, and that animals with weaning more reactive temperament tend to keep this trait (p <0.05). Animals of different temperaments can have the same performance. The second activity aimed to evaluate the behaviour at calving from cows and calves of different genotypes by focal sampling and record the following variables: month and year of birth, body condition of the cow, cow category (primiparous or multiparous), sex and weight of calf at birth, latency to the first contact between cow and calf at birth (in seconds), number of attempts the calf to stand up, latency to stand up (in minutes), latency time to suck (in minutes) and number of times the cow avoid the suck. The evaluated cows were grouped into four genetic groups: Pure British Group - Hereford (HHHH) and Aberdeen Angus cows (ANAN); British with Heterosis group - Aberdeen Angus x Hereford cows - HHAN; crossbred group - cows Aberdeen Angus x Nelore (ANNE) and Hereford x Nelore (HHNE); Adapted x British Group - Aberdeen Angus x cows Caracu (ANCR) and Hereford x Caracu (HHCR). All cows were randomly mated to Brangus bulls (BN) and Braford (BO). To evaluate the performance of cows and calves were considered milk yields of cows, measured at three time points (beginning, middle and end of lactation) and weaning weight of calves, as well as the calculation of average daily gain (ADG) between birth and weaning. Among the variables of behaviour, cows that calved early had higher latency to the first contact with the calf and avoid morer times the first suck. Among the performance variables, differences among genetic groups for weight adjusted at 205 days, average daily gain and milk production, and adapted x British crossbred cows and cows had higher milk production and weaned heavier calves, and these showed higher growth rate (ADG). There was a positive correlation between the variables birth weight, body condition at calving, average daily gain, and weight adjusted at 205 days and milk production. Behavioural variables such as latency to stand up and latency to suckle also positively correlated. There was a negative correlation between body condition and latency time to suck, demonstrating that the nutritional status of the cow at calving affects behaviour. The behaviour at calving follows a standard for genotypes studied, and performance of calves until weaning is mainly influenced by milk production.