CHARACTERIZATION OF THE LACTATION CURVE OF RAMBOUILLET EWES IN MEXICO

Abstract

Sheep (Ovis aries L.) in Mexico are mainly used for meat production, especially for the Mexican dish known as ‘barbacoa’. There is a growing interest in genetically improving ewe breeds with a focus on milk production for cheese, which is increasing in demand internationally. Among other things, this highlights the importance of understanding the lactation curve (LC) in ewes. The objectives of the present study were: a) to characterize the LC of Rambouillet ewes using Wood’s model (Yt = atb e-ct + εi), estimating its three parameters (a, b, c) and other measures of interest: lactation peak (LP), lactation peak day (DLP), and lactation persistency (PER); b) assess the effects of the number of lambs (NL), the type of lambing (TL), and the weaning time of the offspring (WT) on Wood’s model parameters and those of the LC; and c) estimate phenotypic correlations between Wood’s model and the LC parameters. The results showed that the LC obtained was a ‘typical’ curve with parameters a = 901.2 mL, b = 0.1206, c = -0.01299, LP = 1045.1 mL, DLP = 9.2 d, and PER = 2.1. There were significant effects (p ≤ 0.05) of WT on a and of WT and TL on PER; the highest mean of a (957.4) was obtained with weaning at eight weeks. On the other hand, the largest PER averages were found in single lambs and at six of weeks weaning. Phenotypic correlations (p ≤ 0.05) were estimated between and within Wood’s model and the LC parameters. The results of the present study support the recommendation of a milk production system for Rambouillet ewes to make cheese.