Comparison between two milk distribution structures in dairy goats milked at different milking frequencies

Abstract

Twenty-four dairy goats of 3 breeds (Majorera, Tinerfena, and Palmera) in mid lactation (110 +/- 7 d in milk) were milked unilaterally at 2 frequencies (once: X1 or twice daily: X2) for 6 wk to evaluate milk yield and milk composition and to compare two milk distribution structures. On the sampling days, milk volumes of each udder halves were recorded and analyzed. Milk partitioning was divided into: cisternal (CM) and alveolar milk (AM); and into: machine milk (MM), machine stripping milk (MSM), and residual milk (RM). In Majorera and Tinerfena breeds did not find significant differences in milk yield and milk composition due to milking frequency. In contrast, Palmera goats had an increase of 14% in milk yield when they were milked X2 compared with X1, but the protein content was significantly higher in the milk of X1 (3.92%) than X2 (3.72%). Furthermore, the absence of differences in protein daily yield between X1 and X2, suggested that cheese yield could not be maintained. Milking frequency did not affect CM and AM percentages in the studied breeds. Regarding breed factor, Majorera and Palmera had the highest and lowest CM percentages, respectively, both in X1 and X2. On the other hand, MM and MSM percentages did not differ due to milking frequency in Tinerfena and Palmera breeds. However, Majorera goats had significant differences in MM (77.29 vs. 71.66%) and MSM (12.67 vs. 17.41%) for X1 and X2, respectively. A breed effect was observed on MM and MSM fractions: Majorera goats had higher MM percentages, while Tinerfena and Palmera goats had higher MSM percentages. RM fraction was not affected by milking frequency or breed factors. Finally, no significant correlation coefficients were detected when comparing CM and AM with MM, MSM and RM fractions, which indicates that both milk partitioning structures did not seem to be comparable between them, at least in goat udders that have a more horizontal teat insertion. (c) 2013 Elsevier B.V. All rights reserved.