Milk production and lactation curves in three goat breeds in the dry tropic of Mexico.

An experiment was carried out with 20 Creole goats (C), 19 Nubian (N) and 14 White Celtiberic (B), all of them with their offspring and undergoing their second parturition, in order to a) evaluate milk production per day (MP), b) evaluate the effect of environmental factors influencing MP, c) characterize their lactation curves, and d) evaluate factors influencing the lactation curve parameters. The GLM procedure of SAS was utilized to accomplish objectives a, b and d, whereas a linearized Wood model was utilized for objective c. There were significant differences in MP due to breed, stage of lactation, type of birth and breed x stage of lactation interaction. Nubian goats produced 1066.9±31.8 g/d, followed by Creole goats (856.1±28.1 g/d) and finally by B goats (745.0±35.9 g/d). An irregular pattern was found in the stage of lactation; maximum productions were observed in weeks 1 and 9. Does raising twins produced more milk (1036.2±37.9 g/d) than does raising singles (742.5±17.4 g/d). The milk production curve of N does was above the corresponding curves of Creole and B does during most of the lactation period; only in weeks 9 and 10 the milk production curve of C does was above that of N does. The shape of the lactation curve differed among breeds, a factor that is explained by the size and sign of the lactation curve parameters. The peak of MP and the day when this value was observed were 0.848 kg on day 16 for the C goats, 1.175 kg on day 3 for the N goats, and 0.806 on day 25 for the B goats. The lactation curve parameters "a" and "b" were affected by breed and type of birth. It is concluded that there are important differences in milk production and the shape of the lactation curves of these breeds, a factor that must be considered in genetic improvement programs and general management in these regions. [ABSTRACT FROM AUTHOR]