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RESEARCH PRODUCT

Application of the Wood model to lactation curves of Comisana sheep

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Abstract Ninety-two ewes of the Comisana breed were used in a study to verify the forecasting capacity of the mathematical model proposed by Wood for fitting sheep data, and to evaluate the effect of the environmental factors affecting the parameters of the lactation curve. The Wood model underestimated the total lactation milk production with an error margin of 12.2 ± 7.8 kg of milk corresponding to 10.9 ± 6.6%. There was a strong influence of order of lambing × lambing season interaction on the lactation parameters. The curves for the winter lambing ewes demonstrated a higher peak production than autumn lambing ewes (1728.4 vs. 1082.6 g, P ≤ 0.05 for the second lambing ewes and 1772.8 vs. 1383.7 g, P ≤ 0.01 for ≥ 3 lambing ewes); the season persistence difference was small, 4.88 vs. 5.60 for second lambing and 5.32 vs. 5.33 for ≥ 3 lambings. Simple correlations within lambing season showed negative correlation between the peak production and the persistence of lactation ( r a = −0.32 and r w = −0.15). The time at peak and the persistence were positively correlated ( r a = 0.88 and r w = 0.97). Parity was positively correlated with peak production ( r a = 0.41and r w = 0.50) and negatively correlated with the time at the peak ( r a = −0.22 and r w = −0.39) and the persistence ( r a = −0.25 and r w = −0.41). The linear regression of peak production on total production referring to the period from the 31st day post-partum to lactation end was significant. The type of lambing did not significantly influence the shape of the lactation curve although sheep lambing to twins produced more milk than those having single lambs.