Diet energy levels and temperature affect the size of the fat milk globule in dairy goats

Abstract

The study aimed to verify the effect of diet and environmental temperature on traits of milk fat globules (MFG) of goats. The experiment was conducted in climatic chambers, where we housed 12 Alpine goats with a mean age of 4.02±1.78 years, live weight of 41.8±4.59 kg, and average milk production of 2.16±0.59 kg. The animals were subjected to two different controlled temperatures, T1 = 26 ℃ (thermoneutral) and T2 = 34 ℃ (stress), and diets with different energy levels (low, medium, and high). A milk sample of each animal was collected at 6.00 h, coinciding with milking. The effect of temperature and diet was verified on MFG. The highest MFG was observed at 26 ℃ and medium energy diet. The MFG reached lower values with the diet of medium energy and high temperature (34 ℃). On average, 35% of MFG is smaller than 2 μm, 50% is medium in size (2-5 μm), and 15% is large (>5 μm), with a maximum size of 9.57 μm. The higher prevalence of medium-sized MFG is indicative of excellent milk digestibility. The increase in dietary energy levels promoted both the fat and diameter of fat globules. The higher fat and the larger globules would positively affect the cheese-making aptitude and make it suitable for production of hard cheeses. The increase in dietary energy levels for goats promotes an increase in the diameter of fat globules and milk fat (%), essential traits to the cheese industry.