Influence of Forage Diversity on Feeding Behavior and Diet Digestibility in Lambs

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Journal of Animal Science






American Society of Animal Science

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Diverse combinations of forages with different nutrient profiles and classes of plant secondary compounds (PSC; tannins, saponins) may improve intake and nutrient utilization by herbivores. We tested the effects of increasingly diverse combinations of PSC-containing legumes on intake and diet digestibility in lambs. Freshly-cut birdsfoot trefoil (TRE), sainfoin (SAN), and alfalfa (ALF) at the early flowering stage were offered in ad libitum amounts to forty-two lambs in individual pens assigned to 7 treatments (n = 6): single species, a choice of all possible 2-way combinations, or a 3-way choice of the legumes. Composited forage and fecal samples and acid detergent lignin were used to determine in vivo DMD. The change in concentration of BUN from the beginning to the end of the study (24 d) (ΔBUN) was also assessed. Dry matter intake (DMI) and digestible DMI (DDMI) were analyzed as repeated measures designs with lambs (random effect) nested within treatments. A complete random design was used for the remaining variables with treatment as a fixed factor. Lambs preferred ALF > SAN > TRE in 70:30 and 50:35:15 ratios for 2- and 3-way combinations, respectively (P < 0.05). Average DMI and DDMI were 10% greater for 2- and 3-way choices than for single species (Table 1). Digestibility values of tannin-containing legumes (SAN and TRE) and their combination were greater than those recorded for the saponin-containing legume (ALF) or ALF/TRE (Table 1). Feeding SAN in a single diet or in combination had lower ΔBUN and greater fecal N/N consumed ratio (Table 1) than ALF, TRE, or ALF/TRE, suggesting a shift in the site of N excretion from urine to feces. Combinations of PSC-containing legumes have the potential to enhance intake and digestibility while shifting N loses to feces relative to some legume monocultures.