Abstract
ObjectiveThe present study aimed to determine the impact of ewe body condition score (BCS) (over a range of 2.0 to 3.0) and nutritional treatments (consisting of differing herbage masses) during very late pregnancy and lactation and their potential interaction on the performance of twin-bearing ewes and their lambs to weaning.MethodsOn day 142 of pregnancy, twin-bearing ewes with a BCS of 2.0, 2.5, or 3.0 were allocated to a “Moderate’ or ‘Unrestricted’ nutritional treatment until day 95 of lactation (weaning). The nutritional treatments aimed to achieve average herbage masses of 1,200 to 1,300 kg dry matter (DM)/ha (Moderate) and 1,500 to 1,800 kg DM/ha (Unrestricted).ResultsThere were no three-way interactions between ewe BCS group, nutritional treatment and time for any ewe or lamb parameter. The nutritional treatments had no effect (p>0.05) on lamb birth or weaning weight. Lambs born to Moderate ewes had greater survival and total litter weight at weaning (p<0.05). Regardless of BCS group, Unrestricted treatment ewes had greater body condition and back-fat depth at weaning than Moderate treatment ewes (p<0.05). Ewes of BCS 2.0 group reared lighter lambs to weaning (p<0.05) and tended to have a lower total litter weight (p = 0.06) than BCS 3.0 group ewes.ConclusionThis study suggests farmers should aim to have all ewes with a BCS of 2.5 or 3 in late pregnancy for optimal lamb weaning performance. Furthermore, there is no benefit to lamb production of offering ewes pasture masses >1,200 kg DM/ha during very late pregnancy and lactation.
Highlights
New Zealand pastoral systems are predominantly based on perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) swards with pasture growth rates typically lowest during winter [1], coinciding with the late pregnancy period of sheep
Corner-Thomas et al [9] found lambs born to ewes offered pasture masses of 1,500 to 1,700 kg dry matter (DM)/ha from day 141 of pregnancy and throughout lactation were heavier at weaning than those born to ewes offered pasture masses of 1,200 to 1,400 kg DM/ha
During P142 to L15 pasture masses were greater for the Unrestricted treatment than the Moderate treatment (1,701±60 vs 1,168±68 kg DM/ha; p
Summary
New Zealand pastoral systems are predominantly based on perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) swards with pasture growth rates typically lowest during winter [1], coinciding with the late pregnancy period of sheep. Corner-Thomas et al [9] found lambs born to ewes offered pasture masses of 1,500 to 1,700 kg DM/ha from day 141 of pregnancy and throughout lactation were heavier at weaning than those born to ewes offered pasture masses of 1,200 to 1,400 kg DM/ha. This suggests an advantage of greater pasture masses in lactation, how-
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