Effects of dietary quebracho tannin on nutrient utilisation and tissue metabolism in sheep and rats

✍ Scribed by Dawson, Janet M; Buttery, Peter J; Jenkins, David; Wood, Christopher D; Gill, Margaret

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 110 KB
• Volume: 79
• Category: Article
• ISSN: 0022-5142
• DOI: 10.1002/(sici)1097-0010(199908)79:11<1423::aid-jsfa383>3.0.co;2-8

✦ Synopsis

The effect of feeding quebracho tannin, a mixture of condensed tannins, on dietary nutrient utilisation and nitrogen (N) retention and its effects on the gastrointestinal (GI) tract was investigated in sheep and rats. Sheep (n = 24) were fed on a pelleted diet of dried grass alone (controls) or containing quebracho tannin at 50 g kg À1 diet dry matter (DM) (tannin-fed animals) at a level suf®cient to achieve a daily liveweight gain (DLWG) of 100 g day À1 . Complete collections of faeces and urine were made for two seven-day periods after two and six weeks of feeding these diets (n = 6 per group). Apparent digestibilities of dry matter, N and neutral detergent ®bre (NDF) were signi®cantly (P 0.001) reduced in tannin-fed animals at both measurement periods. No evidence was obtained to suggest that rumen micro-organisms can adapt to the presence of dietary tannins with prolonged feeding. Tannin-fed animals excreted signi®cantly (P 0.01) more N in faeces and less in urine than controls suggesting an alteration in N metabolism. Histological examination of samples of the GI tract obtained from pairs of sheep slaughtered after two, ®ve and seven weeks of feeding the diets indicated ulceration and an increase in mucosal histiocytes, particularly in the jejunum and ileum of most tannin-fed animals. In a subsequent experiment, rats were fed ad libitum a ground chow containing either cellulose or quebracho tannin at 40 g kg À1 DM. Tannin-fed rats had signi®cantly (P `0.05) reduced feed intakes, DLWG, N retention and body fat deposition compared to controls. Protein synthesis rates in the duodenal mucosa were not increased in tannin-fed rats suggesting that enterocyte proliferation was not stimulated in this region of the GI tract.

These studies indicate that feeding quebracho tannin to ruminants has both ruminal and post-ruminal effects that, together, result in reduced nutrient utilisation and impaired animal performance.