Comparison of ruminal and abomasal administration of feed on the growth and body composition of lambs

Abstract

The effect of preventing the ruminal fermentation of feed on the perfornlance of growing lambs was investigated by infusing a similar quantity of liquid diet into either the rumen or abomasum of two groups of eight lambs initially weighing 17.5 kg. Each lamb was offered a gross energy intake of 1.11 MJ/day per kg 0 . 73; 62 % being derived from the liquid diet and the remaining 38 % from a pelleted lucerne hay consumed per 0s. Six lambs were slaughtered at the beginning of the experiment to provide an estimate of initial body composition, and the eight lambs from each treatment were slaughtered from 30 to 82 days after commencement of infusions. Separate analyses were made on the blood, commercial carcase, viscera, head plus hooves, skin, and wool. A 3-week digestibility trial was conducted with four lambs from each treatment. Daily gains in body weight, wool growth rate, and the retention of nitrogen and energy were all about twice as great (P < 0.001) in the lambs receiving the abomasal infusions. Abomasal infusion resulted in 24% of dietary nitrogen and 31 % of dietary energy being retained, compared with 12% and 14%, respectively, when the diet entered the rumen. Significantly more of the retained nitrogen and energy was stored in the commercial carcase and less in the wool when the diet was infused into the abomasum. In so far as differences in the mean final weight of lambs given the two treatments made interpretation of body composition results difficult, it appeared that the chemical composition of the whole lamb was not markedly affected by the site of dietary infusion when comparisons were made between animals of the same weight. However, lambs receiving the ruminal infusion contained significantly more protein in the visceral component and had a heavier liver and rumen-reticulum than lambs of similar weight receiving abomasal infusions. The digestibility of all dietary components analysed was significantly less in lambs given the ruminal infusion.