290 Effects of Grazing Diverse Combinations of Sainfoin, Birdsfoot Trefoil, and Alfalfa on Beef Cow Performance and Environmental Impacts

Document Type

Article

Journal/Book Title/Conference

Journal of Animal Science

Volume

95

Issue

suppl_4

Publisher

American Society of Animal Science

Publication Date

8-1-2017

First Page

143

Last Page

144

Abstract

Diverse combinations of forages with different nutrient profiles and plant secondary compounds may improve the efficiency of nutrient utilization by livestock. We tested the effects of grazing increasingly diverse combinations of the tannin-containing legumes sainfoin (SAIN) and birdsfoot trefoil (BFT) and the saponin-containing legume alfalfa (ALF) on cattle performance, digestible DM (DDM), blood urea nitrogen (BUN), and methane emissions. Twenty-one pairs of heifers grazed 3 replications of 7 treatments (single species, choice of all possible 2-way combinations, or a 3-way choice) in a completely randomized block design. Animals grazed during 2 periods of 28 d each, and composited forage and fecal samples were collected during 5 consecutive days at the end of each period to estimate apparent digestibility, using ADL as an internal marker. Methane emissions from ALF and SAIN were assessed using the sulfur hexafluoride technique during each 5-d collection period. Data were analyzed as a repeated measures design with cows (random effect) nested within treatments and period and day as the repeated measures. Average daily gain for the 3-way choice was 26 and 30% greater than for the 2-way choices and monocultures, respectively (P < 0.05). Gains of animals grazing tannin-containing legumes were 34 (BFT) and 17% (SAIN) greater than for those grazing ALF (Table 290). Methane emissions per unit of gain were greater for ALF than for SAIN, and DDM peaked for the ALF–SAIN combination and for the 3-way choice. Cattle grazing tannin-containing legumes as monocultures or in combinations showed lower BUN values than animals under ALF monocultures or legume combinations that had ALF, suggesting a shift in the site of N excretion from urine to feces. In conclusion, diverse combinations of legumes have the potential to enhance livestock performance over less diverse arrays of forages. Tannin-containing legumes in monocultures or in combinations may contribute to reducing methane emissions and urinary nitrogen excretion in grazing cattle.

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