Metabolic Challenges in Late Pregnancy in Multiparous Ewes Fed Silage or Hay

A high risk of ketosis has been observed in ewes bearing multiple foetuses and fed poor quality forages. This study investigated metabolic adaptation in the peri-parturient period in multiparous ewes fed low quality forages. Two groups of 4 ewes, 3–5 years old, bearing 2 and 3 foetuses respectively, based on ultra soundscanning, were used. Poor quality grass was harvested and conserved as either long cut silage (GS) or artificially dried, chopped hay (CH). The two forage types were fed ad libitum to the 2 groups of sheep from day 40 prepartum until parturition in a balanced block design. Fish meal, 100 g, was fed daily from day 26 prepartum. Postpartum, all ewes were fed CH ad libitum and nursed 2 of their own lambs. To ensure growth of the lambs, sheep bearing 3 foetuses and fed GS during pregnancy were fed 500 g whole barley daily postpartum. Eating and chewing activity were recorded continuously for 96 hours at day 33, 19 and 5 prepartum. Blood sampled were collected on day -44, -30, -14, -5 to +1, + 5, +13 and +26 postpartum. Faeces was sampled weekly for faecal egg counts. Dry matter intake increased significantly from 47 to 56 g per kg BW ^0.75 from pre- to post-partum, and was significantly (P < 0.05) lower the last 5 days prepartum in ewes bearing 3 compared with 2 foetuses, regardless of forage type. The estimated Net Energy intake prepartum covered only 50% of ARC energy requirements. Intake of metabolizable protein was 20% lower in sheep fed GS compared to CH. The mean body condition score (BCS) decreased from 3.0 at day 30 prepartum to 2.0 at day 8 postpartum. The mean BCS was one unit lower (P < 0.01) eight days postpartum in sheep fed GS prepartum. On average, sheep spent 6.0 hours eating and 13 hours chewing (eating + ruminating) prepartum, with the GS fed sheep bearing 3 foetuses spending an additional 1.6 hours chewing (P < 0.01). Plasma glucose concentrations averaged 2.6 mM and 3.2 mM pre- and postpartum, respectively. Sheep fed GS had 0.6 mM lower glucose concentration prepartum than sheep fed CH (P < 0.001). The average -bhydroxybutyrate and acetoacetate concentrations in the GS and CH groups were 2.9 and 0.2 mM prepartum and 1.6 and 0.1 mM postpartum, respectively. The highest -bhydroxybutyrate concentrations of 4–5 mM were observed 3–5 days prepartum in sheep bearing 3 foetuses and fed GS. NEFA concentrations increased from 0.5 mM day 40 prepartum to 1.2 mM at parturition, and declined to 0.3 mM over the next four weeks postpartum. All foetuses identified at scanning were born fully developed, despite severe under-nutrition, decreasing BCS, and blood parameters indicative of subclinical ketosis with advancing pregnancy. Lambs born as twins tended to grow faster (291 ± 49 g/d) than triplets (239 ± 54 g/d) (P < 0.16) from birth to day 22. In the peri-parturient period, the four ewes fed GS prepartum had a mean faecal egg count of 600 eggs per g of faeces, approx. 5 times higher than for ewes fed CH prepartum. In conclusion, the present study demonstrated that ewes have the capacity to sustain growth and nutrition of multiple foetuses during severe energy restriction in late pregnancy, but apparently the capacity to produce milk for the lambs after birth may be compromised.