Dietary non-forage fiber sources and starch levels: Effects on growth, meat fatty acid composition, and rumen bacterial community of fattening lambs

Abstract

Our objective was to investigate the interactions between non-forage fiber sources (NFFS) and starch levels (SL) on growth performance, meat fatty acid composition, and ruminal bacterial community of fattening lambs. Two hundred forty healthy three-month-old Hu sheep male lambs (30.28 ± 0.324 kg of body weight) were used in a 2 × 2 factorial experimental design. The experimental factors were NFFS (beet pulp, soybean hull) and SL (HS, high starch = 28.4 %; RS, reduced starch = 16 %). The experimental treatments were as follows: (1) 15 % (as fed basis) Beet pulp in HS level (BP+HS), (2) 15 % Beet pulp in RS level (BP+RS), (3) 15 % Soybean hull in HS level (SH+HS) (4) 15 % Soybean hull in RS level (SH+RS). The trial period lasted 63 days. The final weight, average daily gain (ADG), dry matter intake (DMI), and the proportion of rumen isobutyrate in BP were lower (P < 0.05) than those in SH, while the proportion of butyrate and valerate in BP was higher (P < 0.05). The proportion of propionate and valerate in HS was higher (P < 0.05) than that in RS, while the proportion of acetate, isobutyrate and acetate/propionate was lower (P < 0.05). Additionally, the proportions of certain saturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty acids in muscle, and ruminal bacterial composition and diversity, were independently influenced by both NFFS and SL. In summary, the absence of interactions between dietary NFFS and SL on the majority of measured variables indicates that the effects of NFFS and starch are independent or interactive.