Sustainability and efficiency in dairy farming: an association between temperament, physiology, enteric methane emission and productive performance of dairy cattle of zebu origin

Abstract

The general aims of this thesis were to evaluate the implications of the temperament of crossbred dairy cattle of zebu origin on the productive performance, lactation physiology, and the development of calves during the pre-weaning phase. To this end, a systematic review (SR) and a meta-analysis (MA), and three empirical studies were carried out. The SR and MA aimed to evaluate the effects of dairy cows’ temperament on milk yield. The searches were carried out in four electronic databases (CABI Abstracts, Web of Science, PubMed, and Scopus). Among the studies that returned from the searches, only nine were qualified to enter the meta-analysis. Eight studies were evaluated qualitatively as they did not present sufficient numerical data to be included in the meta-analysis. The articles included in the qualitative analysis indicated that calmer cows produced more milk, what was not confirmed by the quantitative synthesis and MA. Study 1 was entitled ‘Are dairy cows with a more reactive temperament less efficient in energetic metabolism and do they produce more enteric methane?’ and aimed a) to evaluate the relationship between cattle temperament assessed by traditionally used tests with energetic metabolism and enteric CH4 emissions by crossbred dairy cows; b) to assess how cows' restlessness in respiration chambers affects energetic metabolism and enteric CH4 emissions. The temperament of 28 primiparous F1 Holstein-Gyr cows was evaluated during milking and in the handling corral, in addition to behavioral evaluation inside the chambers. Measurements of enteric methane emissions by cows were carried out using respiration chambers and metabolic assessments. The results showed that cows with a calmer temperament emitted less methane per liter of milk and allocated more energy to lactation. We concluded that the cows’ temperament was associated with milk production and enteric methane emissions. Study 2 ‘Isthe temperament of crossbred dairy cows related to milk cortisol and oxytocin concentrations, milk yield, and quality?’ aimed to investigate the relationships between temperament traits and concentration of milk cortisol and oxytocin, milk yield, milkability, and milk quality in Holstein-Gyr cows. The temperament of 76 crossbred cows was evaluated in the milking parlor and in the handling corral. In addition, milk collections were carried out to measure the hormones cortisol and oxytocin, and the measurement of milkability parameters. Our results indicated that cows that were more reactive in the milking parlor produced milk with a higher concentration of cortisol and oxytocin, and a lower protein and fat content, in addition to having lower milk flow and longer milking time than intermediate ones. Calm and intermediate cows during the evaluations in the handling corral produced more milk and had shorter milking time and higher average milk flow. We conclude that the behavioral reactivity of cows may be related to the intensity of their response to stress during handling. In its turn, with the study 3 ‘Does the temperament of crossbred female dairy calves affect weight gain and average daily starter feed consumption?’ we intended a) to characterize temperament traits in dairy calves of zebu origin; b) to assess the effects of temperament on weight gain and on the average daily starter feed consumption during their pre-weaning stage. Three behavioral tests (novel object, novel environment, and voluntary approach) were carried out with 60 crossbred calves (Holstein-Gyr) and the animals' average daily weight gain and starter feed consumption were measured over 63 days. The results showed that calves that were more active and interacted less with the unknown person gained more weight, indicating that there is a possible link between temperament and the performance of crossbred dairy calves. With this thesis, we hope to have generated relevant information that could be useful for production systems formed by animals of zebu origin.