A study was carried out to investigate the effects of feeding low quality non-conventional feeds (NCF) containing phenols and condensed tannins on the clinical profiles of sheep. Thirty-two Omani sheep were fed one of four diets with two base roughages, urea-treated palm frond (UTPF) and Rhodesgrass hay (RGH) and two concentrates, commercial concentrate (CC) and a by-products concentrate (BC) for 120 days. Haematological, serum biochemical and urine analyses were used to assess sheep health. Non-conventional feeds (urea-treated palm frond and by-products concentrate) contained higher levels of polyphenols and condensed tannins than conventional feeds (Rhodesgrass hay and commercial cubes). Feeds based on urea-treated palm frond had lower dry matter, crude protein, acid detergent fibre, neutral detergent fibre, gross energy (P < 0.001) and ash (P < 0.05) digestibility coefficients than those based on Rhodesgrass hay. Animals fed NCF had lower feed intake (P < 0.001) and lower body gain (P < 0.001) than those fed conventional ones. They also produced larger volumes of faeces (P < 0.01) which contained higher levels of nitrogen (P < 0.001) and had lower viscosity values of intestinal content (P < 0.001). Rumen liquor of NCF-fed animals had higher pH and lower ammonia-nitrogen levels (P < 0.01). Animals fed urea-treated palm frond plus by-products concentrate had lower lymphocyte (P < 0.01), monocyte (P < 0.05) and eosinophil (P < 0.05) counts by the end of the trial than those fed Rhodesgrass hay based diets. The urea-treated palm frond and by-products concentrate fed animals had lower blood urea nitrogen (BUN) levels (P < 0.05), higher (P < 0.01) alanine aminotransferase (ALT) and lower serum iron (P < 0.001) than those fed Rhodesgrass hay based diets. There was a trend of increasing blood, leukocytes and specific gravity in the urine of NCF-fed animals. This experiment implies that feeding low quality non-conventional feeds containing antinutritional factors for relatively long periods might produce subtle negative effects on the physiology and chemistry of the digestive system and blood parameters which might negatively affect sheep health and make them more susceptible to diseases.
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