No abstract

Determining what and how much each environmental factor affects pregnancy is crucial to the sustainability and management of beef cow herds. The study evaluated through logistic regression the effect of environmental variables on the increase or reduction in the pregnancy rate of beef cows. The average pregnancy rate in the cows was 73 %, with an average age for the herd of 3.7 years. An increase in age of one year represented a 30 % increase in pregnancy, while a reduction of one year reduced the odds of pregnancy in the cows by 23 %. During the lactation period, an extra seven days' lactation reduced the odds of pregnancy by 12 %. For every seven days that weaning was brought forward, the cows' pregnancy odds increased by 14 %. An increase of 0.1 kg in average daily gain represented an increase of 17 % and 15 % in the odds of pregnancy during the first 60 days post-partum and 60 days to the end of the reproductive period. On the other hand, the loss of 0.1 kg in average daily gain resulted in a 14 % and 13 % reduction in the cows' pregnancy odds, respectively. Factors such as age, the precocity of calving in the calving season, the time the calf remains with the cow and better performance in cows between calving and the end of the mating are strategies that increase the chances of pregnancy in beef cows.

Aspects related to good handling practices have significant impacts on animal behaviour with positive effects on the productivity and profitability of production systems. This study investigated the impact of good handling practices on the modification of stress indicators and the behaviour of beef cattle. Thirty-six male castrated bovines at the growth stage were evaluated for 490 days and submitted to two different production systems in Southern Brazil: good handling practices (GHP) and a traditional handling system of beef-cattle farming (THS). Body weight, reactivity indicators (flight distance and composite behaviour score), and blood indicators of stress (glucose and cortisol) were measured. An analysis of variance was carried out with measurements repeated over time, and Pearson's correlation applied between the variables mentioned above. No differences were found (P>0.05) for body weight in any of the evaluations, with initial weights of 196.2 and 196.3 kg and final weights of 431.0 and 413.8 kg for the GHP and THS steers, respectively. The GHP determined better values for the stress and behavioural indicators compared to THS (P<0.05). The flight distance of the GHP animals decreased from 11.33 to 5.22 metres from the first to the last evaluation, while in the THS animals the values were 10.17 and 11.89 metres, respectively. The behaviour composite score differed in the evaluations at 372 and 490 days, with values of 1.77 and 1.47 for GHP animals and values of 2.92 and 2.83 points for THS animals, respectively. Glucose and cortisol levels decreased with the advancing evaluations in GHP animals, with values from 94.80 to 74.22 mg/dL and from 6.08 to 3.68 µg/dL, respectively. In THS animals, glucose and cortisol levels were similar in the initial and final evaluations, with values of 89.30 and 91.28 mg/dL and 5.34 and 5.80 µg/dL, respectively. Regardless of the handling, the final body weight of the animals correlated negatively with the reactivity indicators and physiological stress indicators. The reactivity of the cattle is influenced by the quality of the human-animal interaction but has no effect on the performance of animals raised on pasture. Good handling practices reduce the reactivity and stress indicators of cattle.

The aim was to identify the predominant variables in the differentiation of meat quality of cattle submitted to surgical castration, immunocastration, or noncastration and fi nished in a tropical pasture. Thirty-nine crossbred cattle were used and distributed in three treatments: i) surgical castration; ii) immunocastration; and iii) non-castration, with an initial mean age of 14.06±0.72 months and a mean weight of 284.10±31.40 kg. We used the principal component analysis to differentiate the qualitative meat characteristics between the treatments. Based on that analysis, we found that the fi rst three principal components explained 71.44% of the total variation in the meat quality data, which ensures that the variation found is associated with the effect of the treatments. The characteristics correlated with the fi rst three principal components and responsible for the discrimination between sexual conditions were subcutaneous fat thickness, instrumental meat color, cooking loss and shear force. These characteristics were similar among castrated animals, regardless of the methods.Therefore, immunological castration preserves the attributes of the meat and prevents possible damage to the physical and mental integrity of the animals. Finally, principal component analysis is an important methodology in the objective investigation of beef meat attributes.

O objetivo deste estudo foi avaliar os componentes não carcaça de novilhas terminadas em pastagem de Tifton 85, suplementadas com três diferentes fontes energéticas. Foram utilizadas 30 novilhas, Charolês x Nelore, com idade e peso médio inicial de 26 meses e 274,5 kg. O delineamento foi o inteiramente casualizado, sendo as fontes energéticas utilizadas: grão de milho, grão de aveia branca ou grão de cevada, o nível de suplementação foi de 1% PV, com 10 repetições por estratégia de suplementação empregada. Os pesos de abate (PA), de corpo vazio (PCVZ) e a relação PCVZ/PA foram similares entre estratégias de suplementação. O peso total de órgãos relativos a 100 kg de PCVZ, foi superior para os animais suplementados com milho, 3,43% PCVZ. O peso relativo de rúmen-retículo foi superior para as fêmeas que receberam cevada, 1,72% PCVZ, porém o peso do trato gastrointestinal não diferiu entre as fontes energéticas utilizadas. O peso dos componentes periféricos e o total de gorduras não foram alteradas pelas diferentes fontes energéticas utilizadas. A suplementação com grão de aveia branca reduz o rendimento de órgãos internos e o rendimento de partes do trato gastrintestinal, em relação ao grão de milho e à cevada, respectivamente.