The literature is very sparse regarding research on the thermal equilibrium in Guzerat cattle (Bos indicus) under field conditions. Some factors can modify the physiological response of Guzerat cattle, such as the reactivity of these animals to handling. Thus, the development of a methodology to condition and select Guzerat cattle to acclimate them to the routine collection of data without altering their physiological response was the objective of the preliminary experiment. Furthermore, the animals selected were used in the main experiment to determine their thermal equilibrium according to the thermal environment. For this proposal, the metabolic heat production and heat exchange between the animal and the environment were measured simultaneously in the field with an indirect calorimetry system coupled to a facial mask. The results of the preliminary experiment showed that the respiratory rate could demonstrate that conditioning efficiently reduced the reactivity of the animals to experimental handling. Furthermore, the respiratory rate can be used to select animals with less reactivity. The results of the main experiment demonstrate that the skin, hair-coat surface and expired air temperature depend on the air temperature, whereas the rectal temperature depends on the time of day; consequently, the sensible heat flow was substantially reduced from 70 to 20Wm(-2) when the air temperature increased from 24 to 34°C. However, the respiratory latent heat flow increased from 10 to 15Wm(-2) with the same temperature increase. Furthermore, the metabolic heat production remained stable, independent of the variation of the air temperature; however, it was higher in males than in females (by approximately 25%). This fact can be explained by the variation of the ventilation rate, which had a mean value of 1.6 and 2.2Ls(-1) for females and males, respectively.

Manejo racional eleva o bem-estar de bovinos Guzerá e melhora a eficiência do trabalho de vacinação Rational management raises the Guzerat cattle welfare and improves the efficiency of vaccination work

The goal of this study was evaluate diets (50 or 80% of concentrate) and body biotypes (late or early) on performance, behavior, carcass condition, meat quality, and feed cost estimates in feedlot finishing Guzera beef cattle. Use of concentrates in the diet may improve performance and carcass fat scores in ruminant animals, but Guzera beef cattle may be more efficient in forage conversion, which directly influences the economic viability of the production system. We evaluated 32 non-castrated male Guzera beef cattle at 32±2 months of age. The experimental design was completely randomized with four treatments and six replicates in a 2 × 2 factorial design (2 diets × 2 body biotypes). Initial and final body weights were 459.4±31.2 kg and 566.7±40.8 kg, respectively. There was no change (P > 0.05) in dry matter intake, feed conversion, or daily weight gain when the concentrate in the diet was increased to 80%. Animals fed a diet with 80% of concentrate spent less time (P < 0.05) ruminating (17.8±6.3 vs. 6.3±2.7% of the assessed time). Body biotype did not alter the variables. The rise from 50 to 80% in the proportion of dietary concentrate increased carcass fat, with positive returns in the production process, even given the reduction in rumination, which can lead to poor welfare of animals consuming 80% of dietary concentrate. Body biotype did not affect the variables studied, but it is worth emphasizing that the age at slaughter of these animals probably influenced this result. Thus, selection of the best diet should be based on feeding cost, and in accordance with the cost estimated in this study, the diet with 80% of concentrate is the most suitable for feedlot finished Guzera beef cattle. ou tardio) sobre o desempenho, comportamento, carcaça, qualidade de carne e estimativas de custos com alimento na terminação de bovinos de corte da raça Guzerá confinados. Aumentar os níveis de concentrado na dieta pode melhorar o desempenho e a gordura na carcaça em animais ruminantes, porém animais de corte da raça Guzerá podem ser mais eficientes na conversão de forragem, o que influenciaria diretamente a viabilidade econômica do sistema de produção. Foram utilizados 32 bovinos de corte da raça Guzerá, machos não castrados com 32±2 meses de idade. O delineamento experimental foi inteiramente casualizado com 4 tratamentos e 6 repetições, em esquema fatorial 2x2 (2 dietas x 2 biótipos corporais). O peso corporal inicial e final foi de 459,4±31,2 kg e 566,7±40,8 kg, respectivamente. Não houve alteração (P > 0,05) no consumo de matéria seca, conversão alimentar e ganho de peso diário pelo aumento de 80% de concentrado na dieta. Animais alimentados com 80% de concentrado na dieta passou um tempo menor (P < 0,05) em ruminação (17,8±6,3 vs 6,3±2,7% do tempo avaliado). O biótipo corporal não modificou (P > 0,05) as variáveis estudadas. O aumento de 50 para 80% na proporção de concentrado na dieta aumenta a gordura na carcaça, com retorno positivo no processo de produção, mesmo com uma redução de ruminação, o que pode leva...