Fasting heat production of Saanen and Anglo Nubian goats measured using open-circuit facemask respirometry

Relationship between thermal environment, thermoregulatory responses and energy metabolism in goats: A comprehensive review

Knowledge on heat stress of animals is key to developing management strategies to mitigate its effects on livestock production. Efficiency and profitability of production systems will certainly be challenged by the forecasted global temperature increase of 1.5 °C between 2030 and 2050. Goats are a resilient animal model, much less affected by climatic variations than average livestock. However, this statement is only true to a certain threshold, which, if exceeded, may affect energy metabolism of goats thus affecting respiratory frequency, heart pulse, evaporative thermolysis and rectal temperature, also altering on hormonal profile of animals, leading to behavioural changes such as altering feed and water intake and sheltering in the quest for homeothermic status. Dairy goat breeds, such as Saanen, are more sensitive to heat stress. Adaptations in nutritional and environmental management, as well as selecting better adapted breeds are strategic practices targeting the mitigation of effects of thermal stress of goats in farming systems. However, studies on effects of ambient temperature on energy and basal metabolisms of goats are scarce. This review aims to elucidate energetic and basal metabolism responses of goats under heat stress targeting the development of management strategies to mitigate heat stress in the farming systems and the conservation of genetic resources, adaptability, phenotypic plasticity, and basal heat production in different breeds.

Applying the California net energy system to growing goats

The aim of this review is to describe the main findings of studies carried out during the last decades applying the California net energy system (CNES) in goats. This review also highlights the strengths and pitfalls while using CNES in studies with goats, as well as provides future perspectives on energy requirements of goats. The nonlinear relationship between heat production and metabolizable energy intake was used to estimate net energy requirements for maintenance (NE_m). Our studies showed that NE_m of intact and castrated male Saanen goats were approximately 15% greater than female Saanen goats. Similarly, NE_m of meat goats (i.e., >50% Boer) was 8.5% greater than NE_m of dairy and indigenous goats. The first partial derivative of allometric equations using empty body weight (EBW) as independent variable and body energy as dependent variable was used to estimate net energy requirements for gain (NE_g). In this matter, female Saanen goats had greater NE_g than males; also, castrated males had greater NE_g than intact males. This means that females have more body fat than males when evaluated at a given EBW or that degree of maturity affects NE_g. Our preliminary results showed that indigenous goats had NE_g 14% and 27.5% greater than meat and dairy goats, respectively. Sex and genotype also affect the efficiency of energy use for growth. The present study suggests that losses in urine and methane in goats are lower than previously reported for bovine and sheep, resulting in greater metabolizable energy:digestible energy ratio (i.e., 0.87 to 0.90). It was demonstrated that the CNES successfully works for goats and that the use of comparative slaughter technique enhances the understanding of energy partition in this species, allowing the development of models applied specifically to goat. However, these models require their evaluation in real-world conditions, permitting continuous adjustments.