Protein profile is affected by milking frequency in dairy goats

Abstract

Ten Majorera breed dairy goats during the early lactation were used to determine the protein profile in milk at three different milking frequencies. The goats were machine milked during 5 weeks using different milking frequencies, at week 1 and 5 of the experiment, goats were milked once daily, at week 2 and 4 the animals were milked twice daily and during the week 3 goats were milked 3 times a day. Every week, milk samples (50 ml) from the whole removed milk were collected from each goat after the first morning milking. The samples were aliquoted and storage at -80°C until SDS-PAGE electrophoresis protein profile analysis. After SDS-PAGE electrophoresis, the gels were scanned and band intensities measured. Particular protein profile was calculated as percentage of each protein over total protein bands intensity. Three groups of proteins were observed. Lactoferrin, Serum Albumin, IgG (heavy and light chains), Kappa Casein and Alfa Lactoglobulin decreased as milking frequency increased in a 30.4, 17.6, 30.2, 54.8, 19.7 and 16.2 %, respectively. After the milking frequency was reduced protein profile values increased at initial values. Beta Casein and Alfa s2 Casein increased as milking frequency increased in a 19.7 and 16.2 %, respectively. After the milking frequency decreased protein profile values decreased at initial values. A third group of proteins (Alfa s1 Casein and Beta Lactoglobulin) remained without changes. In a preliminary conclusion, milking frequency displays an effect on milk protein profile, these changes might be considered when a discussion about increase milking frequency will be stated.