Lactation curves for several US sheep breeds

Abstract

AbstractLactation curves for several dairy traits in sheep were studied. Data were collected from seven pure breeds, three synthetic breeds and twelve single breed crosses in a 5-year milking trial. Wood's lactation model (yn = anbe-cn) was used to describe the lactation curves. Actual and fitted lactation curves had the same shape within each trait except for proportion of lactose. Correlations between actual and fitted lactation curves ranged from 0·92 to 0·99 for all traits except lactose (0·24). There was no apparent explanation for the low correlation for lactose content. It was concluded that the algebraic formula can be used to obtain estimates of parameters for sheep lactation curves. However, some caution should be exercised in extending results to proportion of lactose in the milk.Crossbred groups had higher total milk production than pure and synthetic breeds. Lactation curves for crossbred ewes, grouped by breed of sire, had a similar pattern. Finnsheep and Rambouillet-sired crossbred ewes produced proportionately 0·23 more milk than ewes sired by Dorset and Lincoln rams. Breed differences in total milk production were observed among the pure breeds. The Suffolk breed was superior in milk production. All breeds, except the Romanov, followed a similar pattern for lactation curves. The Romanov breed produced milk at a relatively low but consistent level throughout the lactation trial.