Sheep Nutrition: The Lasting Influence of Early High-Starch Diet $^*$

The aim of the study was to determine long-term effects of a hay- or concentrate-based diet in sheep. Twenty-four lambs (12 male/12 female; 7–14 days of age) were randomly divided into two groups, i.e. control (C) and high-starch (HS), and kept in four group pens (2 pens/treatment). HS group were fed ad libitum concentrate mixture, while C group meadow hay with up to 150 g/day/animal of concentrate mixture. Both treatments were fed milk replacer (MR) for 6 weeks and experimental solid feeds for 4 additional weeks after weaning (stage 1). From week 11 onwards, both groups were transitioned to a forage-based diet which was continued for 5 months (males) and 7 months (females; stage 2). Thereafter, animals were placed in individual pens for measuring voluntary dry matter (DM) intake, digesta retention, and DM digestibility (stage 3), and subsequently challenged with a high-starch diet (stage 4). Body weight (BW) did not differ between treatments (P=0.16) but was numerically greater for HS group during the weaning transition (group × time interaction; P<0.01). Plasma glucose was higher for HS in month 1 and 2, plasma cholesterol and serum non-esterified fatty acids (NEFA) lower for HS in month 2, and serum NEFA was higher for HS in month 4 of the study (group × time interaction; P<0.01). Furthermore, plasma glucose and cholesterol and serum NEFA were lower for HS in month 6 of the study (group × time interaction; P<0.01). In stage 1, C spent more time eating solid feed and ruminating, and HS walking, standing, licking salt lick and performing abnormal behaviors (P<0.01). In stage 2, C spent more time standing and HS walking, ruminating and licking salt lick (P≤0.03). DM intake and BW did not differ between treatments in stage 3 (P≥0.35). Fluid and small particle retention time in the reticulorumen of ewes tended to (P≤0.10) and large was longer for C (P=0.04). In stage 4, rumen pH of males was lower for HS (P<0.01). Whereas feeding a high-starch diet early in life had no long-term effects on DM intake or BW, it did have long-term impacts on blood parameters, selected behaviors, rumination, and digesta retention. Furthermore, the diet provided early in life influenced the ruminal response to a high-starch diet later in life. However, not all observed differences between C and HS were consistent between ewes and rams.