Effect of different forage species supplemented with two carbohydrate sources on short and medium chain fatty acids in sheep milk

Abstract

Sixty four Sarda dairy sheep fed with diets based on fresh forage were allocated to eight groups to evaluate the effect of corn or beet pulp based supplementation on milk fatty acid composition. Four forage species were compared: annual ryegrass (RY, Lolium rigidum Gaudin), sulla (SU, Hedysarum coronarium L.), burr medic (BM, Medicago polymorpha L.), and garland, a daisy forb, (CH, Chrysanthemum coronarium L.). The supplements were iso-nitrogenous but differed in carbohydrate composition consisting either of 60% (DM) of corn (concentrate C) or 40% sugar beet pulp (concentrate BP). The supplementation was iso-energetic (500 and 530 g/d, respectively). Overall during winter period (growing stage of the forages) SU and RY groups showed higher levels of atherogenicity index and C16:0. In winter period BP outperformed C for palmitic acid. In spring AI showed a trend similar to that of winter. Moreover C concentrate gave a better level of AI and myristic acid than BP. This study confirms that forage species and, to a lesser extent, carbohydrate source in the supplement markedly affect medium-chain FA profile and hence atherogenicity index in sheep milk.