Factors affecting the lactation curve in crossbred cows in tropical regions

Barrios, U.A.; Rincon, E.; Ventura, M.; Huerta, N.; Fondevila, M.; Surra, J.C.E.

Revista de la Facultad de Agronomia, Universidad del Zulia 13(6): 741-749

1996


Accession: 003138038

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Abstract
The evolution of the lactation curve in a tropical environment was studied using lactation data from 730 cows of 6 different crossbreeds (Holstein, Brown Swiss and Brahman; 1/2 or 5/8 crosses), from the "La Esperanza" farm of the University of Zulia (Venezuela). The farm is situated in an area with an average annual temperature of 28 degrees C and 1100 mm rainfall. Monthly milk yields for each lactation were used to estimate parameters 'a' (initial yield), 'b' (yield prior to lactation peak), and 'c' (yield following lactation peak) using the model: Y = atbExp-ct by non-linear regression. The effect of breed, management, calving season, and lactation number on curve parameters were studied. Breed affected parameter 'a' significantly (P<0.001) giving higher values for Holstein cows (average values of 10.83 and 10.36 for 5/8 and 1/2, respectively). Parameters 'a', 'b' and 'c' increased significantly (P<0.001, P<0.01 and P<0.001, respectively) with lactation number. Season of calving exerted no effect on milk yield.