Factors affecting milk yield and lactation curve fitting in the creole sheep of Chiapas-Mexico

Abstract

Milk production records of black (88), white (94) and brown (61) varieties of the Creole sheep located in Chiapas, Mexico, were used to measure some environmental effects that modify milk yield for 120 days (MY) and the characterization of the lactation curve. A mixed model with repeated measures was used and Wood (WM) and multiple regression models (MR) were compared in the curve fitting. Significant differences (p < 0.05) between varieties was observed for milk yield, being the brown (13.25 ± 0.57 kg) higher than the white (11.16 ± 0.42 kg) and the black variety (10.86 ± 0.44 kg). Forty nine percent of the MY was reached during the first 40 days. Daily milk yield was 118 ± 0.74 ml, 104 ± 0.60 ml and 99 ± 0.53 ml for the brown, white and black varieties, respectively. In the curve fitting analysis, it was observed that both models are similar for the white variety (R2 = 0.3964 versus 0.3959), however for the brown variety, MR was 10% higher, and for the black one, WM was higher than to MR (R2 = 0.4019 versus 0.2701, respectively). In this study the white and brown varieties did not have a milking peak, while the black variety had a milking peak during the first week. Findings in the Creole sheep suggest that this could be a characteristic of the lactation curve in non-selected animals. © 2004 Elsevier B.V. All rights reserved.