Effects of physical forms of starter feed on growth, nutrient digestibility, gastrointestinal enzyme activity, and morphology of pre- and post-weaning lambs

The physical form of starter feed may affect the gastrointestinal development and the performance of ruminant. However, little information is available on how changes in the physical forms of starter feed influence the performance of lambs, especially diming the pre- and post-weaning periods. The aim of this study was to investigate the effects of different physical forms of starter feeds on growth performance, nutrient digestibility, gastrointestinal enzyme activity, and morphology of pre- and post-weaning lambs. Twenty-four 8-day-old male Hu lamb (5.04 +/- 0.75 kg BW) were randomly assigned to one of two dietary treatments: 1) a pelleted starter (PS) feed and 2) a textured starter (TS) feed, which included coarse mashed steam-flaked corn. From eight to thirty-five days of age (pre-weaning), the lambs were bottle-fed milk replacer (MR) at 2% of BW measured on day 8. All lambs were weaned at day 35 when feeding of MR was stopped. Six lambs for each treatment were euthanized at 21 or 42 days of age for sampling. The following results are obtained by variance analysis: TS lambs had a greater (P < 0.05) final BW, higher apparent digestibility of starch and ether extract, activities of a-amylase pre- or post-weaning, and higher (P < 0.05) average dry matter intake and lipase post-weaning in small intestine contents and had a trend of significantly higher average daily gain post-weaning (P = 0.07). Rumen development analysis of TS lambs showed a significantly higher (P < 0.05) relative weight of rumen post-weaning, greater papillae length, increased circular and layered muscle, increased sectional area pre- and post-weaning, and increased rumen papillae width post-weaning. Textured starter treatment increased the villus height and villus width (except jejunum pre-weaning) of the whole small intestine and villus height to crypt depth ratio of jejunum and ileum during the whole period and tended to increase the relative weight of the rumen pre-weaning (P = 0.07). The results indicated that TS feeding is more beneficial to lambs over the weaning transition than PS in promoting gastrointestinal development, intestinal enzyme activities, nutrient digestibility, and growth performance. The findings provide new insights into the selection of physical forms of starter feeds in lamb production. Further research with more animals and female lambs is needed to obtain a more complete conclusion. (C) 2020 The Authors. Published by Elsevier Inc. on behalf of The Animal Consortium.