Morfometria dos glóbulos de gordura do leite de cabras alpinas em função da temperatura ambiente e dos níveis de energia na dieta

Abstract

The objective of this study was to verify if the ambient temperature and dietary energy levels influence the morphometric characteristics of goat milk fat globules. The experiment was conducted at the Animal Bioclimatology Research Unit of the Federal University of Paraíba, Campus de Areia, State of Paraíba, Brazil. Twelve alpine brown multiparous goats with a mean age of 4.02 ± 1.78 years, live weight 41.8 ± 4.59 kg, average production of 2.16 ± 0.59 kg of milk were used. The experimental design was a 2x3 type crossover (2 temperatures and 3 diets), with the two temperatures: T1 = 26 ºC (thermoneutra) and T2 = 34 ºC (stress) and 3 levels of energy in the diet (low, medium and high ), The experiment was conducted in two 20-day periods. From the basal diet, a quantitative restriction was applied in the supply of ration for the treatment of low energy, as well as, the diet was formulated for the treatment of high energy. The data were submitted to analysis of variance (ANOVA) and the averages were compared by the Tukey test, considering significant differences, at the 5% level of probability, through PROC GLM of SAS (2003). The data were submitted to an interaction analysis (Table 3) and it was observed that there was no significant interaction (P> 0.05) for the studied variables considering temperature xdieta, in this way the effects were worked separately (Table 4 and 5). Milk production, fat, GGL amount and classification (small, medium and large) had no significant effect of temperature (P> 0.05). The diameter variable had a significant effect (P <0.05) for temperature (Table 4). Milk fat, diameter and amount of GGL as well as the percentage of small GGL were influenced by diet (P <0.05) (Table 5). Ambient temperature and dietary energy levels interfere with the fat globule diameter of goats' milk and there is a higher concentration of small globules (below 2.0μm) and is considered an important characteristic in digestibility and quality of goat's milk.