Nutritional status of adult ewes during early and mid-pregnancy. 1. Effects of plane of nutrition on ewe reproduction and offspring performance to weaning

Abstract

The objective of this study was to determine the effects of plane of nutrition during early and mid-pregnancy on the performance of mature ewes and their offspring. From day 0 to day 39 post mating (early pregnancy, EP), 82 multiparous ewes were fed to provide either 60% (low, L), 100% (medium, M) or 200% (high, H) of predicted metabolisable energy (ME) requirements for maintenance, following a synchronised mating. From day 40 to day 90 (mid-pregnancy, MP), ewes were provided with either 80% (M) or 140% (H) of ME requirements. After 90 days of gestation, all ewes were fed to meet requirements for late pregnancy. During EP, mean live weight (LW) and body condition score (BCS) change of ewes were 26.3, 20.8 and 16.0 kg and 20.02, 10.10 and 10.22 units in the L-, M-and H-EP treatments, respectively. During MP, mean LW and BCS change were 20.8 and 14.9 kg and 20.09 and 10.09 units in the M-and H-MP treatments, respectively (P , 0.001). Treatments had no effect (P . 0.05) on conception rate, although there tended to be an inverse relationship (P 5 0.085) between plane of nutrition in EP and plasma progesterone concentrations at day 42 of gestation. EP nutrition influenced foetal development with lambs from ewes offered diet L-EP being smaller (P , 0.01) at day 56 than M-or H-EP lambs. However, at parturition L-EP lambs were heavier (P , 0.05) and tended to have higher (P 5 0.056) immunoglobulin status 24 h after birth. Mortality rates at weaning were reduced (P , 0.05) for lambs born from ewes offered diet L-EP compared with M-or H-EP lambs. Diet M during mid-pregnancy resulted in larger (P , 0.05) foetuses at day 80 of gestation. At parturition, these lambs had longer head and crown-rump lengths than H-MP lambs (P , 0.05). Lambs born to ewes offered diet M-MP tended to progress faster to attempting to suckle than H-MP lambs (P 5 0.089). There was an interaction between plane of nutrition in early and mid-pregnancy, whereby the highest number of lambs weaned was a result of diet L-EP followed by diet M-MP. These results indicate that in adult ewes, temporary nutrient restriction during early pregnancy results in better lamb survival; and mild nutrient restriction in mid-pregnancy tends to improve neonatal behaviour and results in lambs with longer skeletal size.

The effects of allowance and frequency of allocation of deferred herbage, and grass silage feed value, when offered to ewes in mid-gestation on ewe and lamb performance and subsequent herbage yield

“…Previous studies (McCrabb et al, 1992) have shown that feeding ewes that were in good condition at the beginning of the study (day 30), above maintenance requirement, reduced placental size, which is positively correlated with lamb birth weight. However, Muñ oz et al (2008) showed that increasing feed level in mid-pregnancy from 0.8 to 1.4 maintenance did not influence birth weight. The lack of an Deferred (extended) grazing and silage for pregnant ewes effect of offering silage indoors (even at higher levels of feeding) on lamb birth weight is probably associated with diet type and feeding method.…”

Nutritional status of adult ewes during early and mid-pregnancy. 2. Effects of supplementation with selenised yeast on ewe reproduction and offspring performance to weaning

“…The effects of plane of nutrition in early and mid-pregnancy are reported in an accompanying paper (Muñ oz et al, 2008).…”

“…The ewes were randomly allocated to treatments and subsequently balanced for LW, BCS, ewe breed and sire breed. The ewes were naturally mated once following a synchronisation regime as described by Muñ oz et al (2008). Treatments were applied from day 214 to day 90 post mating and consisted of control; receiving no supplement; and Se supplement receiving 1 g of Selplex R (Alltech, Belfast, NI, UK), an organic source of Se, providing an intake of 0.5 mg Se per ewe per day.…”

“…Diets were based on grass nuts, offered at one of three levels (high, medium or low plane of nutrition), during the first 39 days of gestation and at one of two levels (medium or high) during mid-pregnancy (day 40 to day 90) as described by Muñ oz et al (2008). Selenium content of the grass-based diet was determined by atomic absorption spectrophotometry with vapour generation and reached 0.07 mg Se per kg DM.…”

“…Lambs were weighed at 24 h post partum, at 3 and 6 weeks of age, and thereafter at fortnightly intervals until weaning (16 weeks). Twenty-four hours after birth, two jugular blood samples, one heparinised and one without anticoagulant, were taken from each lamb as described by Muñ oz et al (2008) to assess immune status, serum free tri-iodothyronine (free T 3 ), serum thyroxine (T 4 ) and Se status. Immune status was estimated by zinc sulphate turbidity analyses (McEwan et al, 1970).…”