Effect of Excessive Environmental Heat Load on Digestibility, Energy Balance, and Urea Recycling in the Mediterranean (Member) Goat

Abstract

This study investigates the energy and nitrogen economy of the Mediterranean goat across diverse environmental conditions, emphasizing the influence of heat stress and shelter on animal productivity. Environmental factors such as water availability, food quality, and heat stress affect the animal's capacity to convert indigestible plant components into digestible food and sustain energy balance. In particular, heat stress causes a significant decrease in the goat's food by 27.49% and by 34.85% in alfalfa hay and wheat straw respectively, leading to a loss of body mass, even when offered high-quality food such as alfalfa hay. However, when sheltered from direct sunlight, the goat can maintain an energy balance on any diet, a significant decrease in body mass was recorded, with a reduction of 10.59% for alfalfa hay and 17.79 ± 3.0% for wheat straw. Heat stress also impairs the goat's ability to maintain a balanced nitrogen economy, reducing nitrogen loss through excretion during heat load conditions and high-protein food digestion. The study found that the average urea recycling rate in goats kept in a shelter was 36%, which was significantly higher than the rate observed in goats exposed to heat stress, which was only 19.6%. Moreover, the amount of recycled urea was also higher in the shelter at 91% compared to 69.9% in the reflected heat stress recorded when the goats were maintained on a diet of wheat straw. As the goat cannot reduce its metabolic rate, a negative energy balance occurs, resulting in body mass loss. The quality of food and heat stress are critical determinants of the goat's food consumption, with high heat load reducing appetite. This study concludes that sheltered conditions, providing protection from direct sunlight, are necessary to sustain productivity and maintain a stable body mass on any diet. Furthermore, maintaining a balanced nitrogen balance can be challenging for animals consuming low-protein food, particularly under suboptimal feeding conditions. The study's findings have implications for the broader issue of global warming, as rising temperatures could increase heat stress and reduce food consumption and productivity in animals, with potentially negative consequences for agriculture and food security. Therefore, protecting animals from heat stress through adequate shelter and management practices is essential to mitigate the negative impacts of global warming on animal productivity, Animal husbandry, and human livelihoods.