Effects of a glucogenic diet on reproductive performances and foetal growth in dairy ewes

BACKGROUND-AIM Nutritional challenges during the periconceptional period and gestation can affect fetal growth and future development of the offspring. The aim of the experiment was to test, in dairy ewes, the effects of two different nutritional plans (high and low starch) fed from weaning to parturition on pregnancy rates, foetal development and morphometric parameters of lambs at birth. METHODS From 30 days of age until parturition, 118 Sarda ewes were randomly allocated to two different nutritional plans: the high starch group (HS; n= 56) and the low starch group (LS; n=62) were fed respectively diets consisting in 25% and 9% of starch and sugars on total dry matter. In the LS diet, part of the starch was substituted with beet pulp. At the onset of puberty, ewes were submitted to oestrus synchronisation and allowed to mate with rams of proven fertility wearing a marking harness. Non return to oestrus rates were recorded. Pregnancy diagnosis was confirmed by transabdominal scan (MylabTM One, Esaote, Italy) at 25 days post mating. Ultrasound scanning was repeated at 30 days for the measurement of crown rump length (CRL) and assessment of twinning rates, and at 48, 68, and 88 days for the measurement of biparietal diameter (BPD) of foetuses. At birth, liveweights and withers heights were recorded. Data were analysed by x2 test or t-test using StataIC 11 (StataCorp LP, USA). RESULTS Non return to oestrus and pregnancy rates did not differ between groups (HS 66.1% vs LS 56.4%; P>0.05) and no effect of nutrition was observed for twinning rates (HS 37.8% vs LS 25.7%; P>0.05). In HS ewes, CRL of foetuses was higher compared to LS ones (2.16 cm ± 0.03 vs 2.05 cm ± 0.04; P<0.05) but BPD recorded up to 88 days post mating did not differ between groups (P>0.05). At birth, no effect of the diet was reported on lambs liveweight (HS 3.72 Kg ± 0.57 vs LS 3.67 Kg ± 0.56; P>0.05) and withers height (HS 36.6 cm ± 1.5 vs LS 36.2 cm ± 1.63; P>0.05). CONCLUSIONS The glucogenic diet fed from weaning to parturition did not have any remarkable effect on reproductive performances, foetal growth, and morphometric parameters at birth. Further investigations are needed to assess if exposing the foetus to these maternal nutritional challenges in a specific gestational window may have consequences on its development and growth.