Effect of milking frequency and genotype on milk partitioning and milk quality

Abstract

30 dairy goats of three Canary breeds (Majorera, Tinerfeña and Palmera) in middle lactation period were milked to evaluate udder compartments (cisternal and alveolar), milk yield and milk composition of each milk fraction. Left mammary gland were milked once daily (X1) and right mammary gland twice daily (X2) at 10 and 14 hours intervals during 3 weeks. Before milking goats an intravenous injection of an inhibitor of oxytocin (Atosiban®) was administered to evaluate the cisternal milk yield. After cisternal milk removal, goats were intravenously injected with 2 IU of oxytocin, and then milked again in order to collect the milk contained in the alveoli. No significant differences were found in the percentage of cisternal and alveolar milk on total milk produced in X1 and X2. Nevertheless, the Majorera breed had higher average yields of cisternal milk (54.79 ml/h and 58.57 ml/h for X1 and X2, respectively), than Tinerfeña breed (50.63 ml/h and 57.88 ml/h for X1 and X2, respectively) and Palmera breed (42.22 ml/h and 52.73 ml/h for X1 and X2, respectively), and consequently those goats had a 13.55% and 20.58% more cisternal area than Tinerfeña and Palmera breed, respectively. Cisternal milk of X1 goats contained similar percentages of fat (3.70 vs 3.65%), protein (3.65% vs 3.56%), lactose (4.83% vs 4.85%), total solids (12.90% vs 12.76%) and solids non fat (9.19% vs 9.10%) than cisternal milk of X2 goats. However, alveolar milk of X1 goats contained higher percentages of fat (6.31% vs 5.43%) and total solids (15.27% vs 14.42%) than alveolar milk of X2 goats. Although, there were breed by frequency interactions in the cisternal milk yields (P= 0.032), no interactions for the parameters of cisternal milk composition were found. In the alveolar milk, breed by frequency interactions were not found in the milk yield (P= 0.793) and milk composition. In sum, the milking frequency did not affect the percentage of cisternal and alveolar milk in Canary breed goats. Furthermore, the milking frequency has not negative effects on composition of cisternal and alveolar milk.