Abstract
Simple SummaryIn the current study the impact of cold temperatures (CT; −3 to 6 °C) on milk production and metabolism was evaluated in dairy goats. Compared to goats in thermoneutral conditions (TN; 15 to 20 °C), CT goats produced lower amounts of milk, but their milk contained more fat and protein. Consequently, the yield of energy-corrected milk did not vary between TN and CT goats. Additionally, feed intake did not vary between treatments. The CT goats mobilized body fat reserves to spare glucose and cover the increased needs for heat production under low temperatures. In conclusion, CT goats produced lower milk yield, but their milk contained greater fat and protein compared to TN goats. Furthermore, cold temperatures induced metabolic changes that included body fat mobilization without changes in blood insulin values.Low winter temperatures in some regions have a negative impact on animal performance, behavior, and welfare. The objective of this study was to evaluate some physiological, metabolic, and lactational responses of dairy goats exposed to cold temperatures for 3 weeks. Eight Murciano-Granadina dairy goats (41.8 kg body weight, 70 days in milk, and 2.13 kg/day milk) were used from mid-January to mid-March. Goats were divided into 2 balanced groups and used in a crossover design with 2 treatments in 2 periods (21 days each, 14 days adaptation and 7 days for measurements). After the first period, goats were switched to the opposite treatment. The treatments included 2 different controlled climatic conditions with different temperature-humidity index (THI) values. The treatments were: thermoneutral conditions (TN; 15 to 20 °C, 45% humidity, THI = 58 to 65), and cold temperature (CT; −3 to 6 °C, 63% humidity, THI = 33 to 46). Goats were fed ad libitum a total mixed ration (70% forage and 30% concentrate) and water was freely available. Goats were milked at 0800 and 1700 h. Dry matter intake, water consumption, rectal temperature, and respiratory rate were recorded daily (days 15 to 21). Body weight was recorded at the start and end of each period. Milk samples for composition were collected on 2 consecutive days (days 20 and 21). Insulin, glucose, non-esterified fatty acids (NEFA), ß-hydroxybutyrate (BHB), cholesterol, and triglycerides were measured in blood on d 21. Compared to TN goats, CT goats had similar feed intake, but lower water consumption (−22 ± 3%), respiratory rate (−5 ± 0.8 breaths/min), and rectal temperature (−0.71 ± 0.26 °C). Milk yield decreased by 13 ± 3% in CT goats, but their milk contained more fat (+13 ± 4%) and protein (+14 ± 5%), and consequently the energy-corrected milk did not vary between TN and CT goats. The CT goats lost 0.64 kg of body weight, whereas TN goats gained 2.54 kg in 21 days. Blood insulin and cholesterol levels were not affected by CT. However, values of blood glucose, NEFA, hematocrit, and hemoglobin increased or tended to increase by CT, whereas BHB and triglycerides decreased. Overall, CT goats produced less but concentrated milk compared to TN goats. Despite similar feed intake and blood insulin levels CT goats had increased blood glucose and NEFA levels. The tendency of increased blood NEFA indicates that CT goats mobilized body fat reserves to cover the extra energy needed for heat production under cold conditions.
Highlights
Exposure to hot or cold environments negatively affects production, reproduction, welfare, and health of ruminants [1,2]
At 5:00 p.m., when the ambient temperature reached its highest level for cold temperature (CT) (6 ◦ C), the rectal temperature was similar for both thermoneutral conditions (TN) and CT goats
Rectal temperatures increased from 8:00 a.m. to 5:00 p.m. by 0.88 ◦ C in CT goats in accordance with the increment in the ambient temperature throughout the day
Summary
Exposure to hot or cold environments negatively affects production, reproduction, welfare, and health of ruminants [1,2]. Some regions in the world experience high ambient temperatures during the summer and very low temperatures during the winter. This wide difference in temperatures between seasons represents a challenge for animals in these regions to cope with conditions in the summer and winter [2]. Ruminants can cope with cold temperatures by physiological and behavioral changes that allow them to maintain their energy homeostasis [3]. Energy requirements for maintenance have been reported to increase by 20% under cold temperatures and can double if the animal is wet and exposed to the wind [4]. The increment in maintenance requirements results in fewer available nutrients for production, and, decreased performance and production efficiency
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