Sustainability and efficiency in dairy farming: an association between temperament, physiology, enteric methane emission and productive performance of dairy cattle of zebu origin ; Sustentabilidade e eficiência na pecuária leiteira: uma associação entre temperamento, fisiologia, emissão de metano entérico e desempenho de bovinos leiteiros de origem zebuína

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 ...