Milk yield and milk composition from grazing primiparous non-dairy crossbred ewes

Abstract

Milk production and milk composition were studied in 520 primiparous Merino crossbred ewes that were the progeny of 30 sires from several maternal crossing breeds including Border Leicester, Coopworth, Finnsheep and East Friesian. The ewes were born in 3 years (1997, 1998, and 1999), with 3 sires used in every year to provide genetic links. The crossbred ewe lambs were randomly assigned to autumn or spring joining groups and mated to Poll Dorset rams to lamb at 12 or 19 months of age. Ewes were milked on 3 days during their first lactation at approximately 3, 4, and 12 weeks after lambing. On each milking day, each ewe was initially injected with oxytocin, milked out by machine, and then hand-stripped. This procedure was repeated approximately 4 h later, with the milk weight and time recorded to extrapolate to daily milk yield, and composition of the milk was determined. Daily milk yield was analysed using REML mixed models procedures and 3 measures of milk production were predicted: peak milk yield at 21 days of lactation, total milk yield from 21 to 90 days of lactation, and length of lactation (days for daily yield to decline to 600 g/day). Milk composition traits (%fat, %protein, %lactose) and proportion of machine milk yield were analysed with similar models. Sire breed, number of lambs born and suckled, season, and ewe weight gain from mid-pregnancy until lamb weaning were all significant (P < 0.01) for daily yield, which declined from 2.1 kg/day at 21 days to 0.7 kg/day at 90 days of lactation. The Finnsheep-cross ewes had lower peak milk yield (1.84 ± 0.08 v. 2.09–2.19 ± 0.1 kg/day) and lower total yield of lactation (21–90 days) than all the other breed-cross ewes (78 ± 3 v. 92–107 ± 5 kg). The East Friesian-cross ewes had significantly longer lactations (128.8 ± 10.9 days) than the Border Leicester (98.1 ± 4.4 days) and Coopworth (93.7 ± 4.2 days), with the Finnsheep-cross ewes the shortest (80.1 ± 3.1 days). The East Friesian-cross ewes had the greatest and the Finnsheep-cross ewes the least total yield of lactation (107 ± 5 and 78 ± 3 kg, respectively). There were significant differences in peak milk yield for ewes bearing and suckling single lambs, twin-born and single-raised lambs, and twin-born and raised lambs (1.86 ± 0.04, 2.03 ± 0.09, and 2.37 ± 0.07 kg/day, respectively). There was a significant decline in daily milk yield with increasing ewe weight gain from mid-pregnancy to lamb weaning (–18.1 ± 4.2 g/kg). All the components of milk composition changed from the peak of milk production at 3 weeks to the end of lactation. The East Friesian-cross ewes had significantly lower milk %fat (by approx. 1 percentage point) at both 21 days and 90 days of lactation than ewes by all other sire breeds. The 30 sire progeny mean deviations for daily milk yield ranged from –292 to +276 g/day, with considerable ranges between sires within the sire breeds. The implications for lamb production and breeding programs are discussed.

The relationship of lamb growth from birth to weaning and the milk production of their primiparous crossbred dams

“…Holst and Hall (1994) reported that milk yield measured at an average age of 4 weeks was significantly related to single lamb weights at 8 and 12 weeks and at weaning. The lamb growth rates in Period 1 from the five breed groups were similar in ranking to the ranking of the ewes for 21-day milk yield reported by Morgan et al (2006). The low growth rates of lambs from Finnsheep cross ewes in Period 1 is associated with their low milk yield.…”

“…In this experiment there was a growth rate advantage of the Border Leicester over the Finnsheep breed group in Period 1 (30 g/day), although it was negligible in Period 2 (1 g/day). The East Friesian cross ewes had similar 21-day milk yield (2.19 v. 2.16 kg/day, not significant) to the Border Leicester cross ewes (Morgan et al 2006) and their lambs had similar growth rates to those from the Border Leicester ewes (305 v. 309 g/day, not significant) in Period 1. However, in Period 2 lambs born to East Friesian cross ewes had significantly higher growth rates than all other lambs.…”

“…Daily milk production of the ewe was extrapolated from the 4-h milk test. The same operator milked all ewes on each occasion in this experiment, with further details in Morgan et al (2006). Milk composition (fat %, protein % and lactose %) was analysed at a commercial laboratory, using a Milko Scan 4000 (Foss Electric, Denmark) calibrated for sheep milk.…”

Improving the nutrition of Merino ewes during pregnancy and lactation increases weaning weight and survival of progeny but does not affect their mature size

“…Nonetheless the liveweight change of the ewe during pregnancy was the next most important influence on weaning weight and more important than changes in ewe liveweight during lactation. This lesser impact of ewe liveweight change during lactation on weaning weight was expected as ewes preferentially partition nutrients to milk production rather than body reserves during lactation (Morgan et al 2006). The prediction of growth rate and weaning weight of progeny from feed on offer during lactation and ewe liveweight profile to lambing were consistent across two seasons at each of two sites.…”

Effect of supplemental yeast culture and physiological factors on colostrum and milk composition of Pelibuey ewes

“…By contrast, Ochoa et al (2007) reported that Rambouillet ewes that gave birth to single lambs produced milk with a higher concentration of fat, protein, and total solids. Morgan et al (2006) and Afolayan et al (2009) did not find effect of litter size on milk protein, fat, and lactose content. Milk protein content was lower in Tsigai and Valachian ewes giving singles birth singles, whereas in Lacaune ewes, no difference in protein content between the ewes lambing singles or multiples was found (Oravcová et al 2007).…”