| Resumo: |
Abstract The effects of physiological and management factors on the milk composition of Rambouillet ewes under confined management at the Sheep Unit, Agronomy Faculty, Universidad Autónoma de San Luis Potosí, México, were evaluated. Two treatments were randomly assigned to 45 single and twin-rearing ewes, 2-5 years old: 6 and 8 weeks of lactation, which were the dates when the lambs were weaned. Milk samples were taken during lactation (weeks 1, 3, 6, 8, and 12), and chemically analyzed using standard laboratory procedures for protein, fat, total solids, ash and lactose percentages. Statistical analysis was performed utilizing a model that included the fixed effects of lambing number (LN: 1-3+), birth type (BT: single, twins), lamb sex (LS: ram lambs, ewe lambs, utilizing a separate model), weaning date (WD: 6 weeks, 8 weeks), and first order interactions. Overall means for milk protein, fat, total solids, ash, and lactose were 5.2±0.5%, 5.6±2.1%, 16.7±2.1%, 0.91±0.06%, and 4.5±0.4%. Consistent significant (p≤0.01) effects of LN, BT, and WD were observed for protein, fat and total solids. An LS effect (p≤0.05) was found only on lactose. Significant (p≤0.01) LN×WD and BT×WD interactions showed an influence on milk fat and total solids.
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