Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2011
Publication Date: 12/1/2011
Citation: Macadam, J.W., Ward, R.E., Griggs, T.C., Minn, B.R., Aiken, G.E. 2011. Case study: average daily gain and blood fatty acid composition of cattle grazing the non-bloating legumes birdsfoot trefoil and cicer milkvetch in the mountain west. Professional Animal Scientist. 27:574-583. Interpretive Summary: Birdsfoot trefoil is a forage legume that is productive and persistent under irrigation in the northern Mountain West U.S.A. Like alfalfa and clovers, birdsfoot trefoil is high in protein, but also is high in tannins. Tannins have demonstrated to reduce ammonia production in the rumen and nitrogen excretion in the urine to mitigate the adverse environmental effects of ammonia emissions and nitrogen in runoff water. The forage quality of birdsfoot trefoil also is high. A grazing experiment, conducted by Utah State University, determined higher average daily gain by steers grazing birdsfoot trefoil with medium tannin concentrations (‘Oberhaunstadter’) than those grazing ‘Monarch’ cicer milkvetch, and a tendency for higher average daily gain with medium versus low tannin birdsfoot trefoil (‘Norcen’). Blood omega-6 to omega-3 fatty acid ratios were greater in steers grazing pastures of both cultivars of birdsfoot trefoil than those grazing cicer milkvetch, which indicated that higher quality beef could be produced by grazing birdsfoot trefoil. Therefore, irrigated birdsfoot trefoil has potential as a high-quality forage in the western U.S.A. that has environmental benefits and can increase omega-6 fatty acids in carcasses.
Technical Abstract: Birdsfoot trefoil (BFT) is a forage legume that is productive and persistent under irrigation in the northern Mountain West U.S.A. The type and concentration of condensed tannins in BFT are beneficial for livestock production. We hypothesized that cattle grazing monoculture BFT would have high ADG based on studies with sheep in New Zealand and cattle in Missouri. Our objective was to compare ADG on 2 BFT varieties with ADG on cicer milkvetch (CMV), a legume that does not contain tannins. Fall-born cattle fed from weaning on a 40:60 maize silage:alfalfa hay diet grazed monoculture legume pastures for two 30-day periods beginning 3 June 2008, and for 2 periods of 45 and 32 days beginning 3 June 2009. Treatments were low-tannin (‘Norcen’) BFT, medium-tannin (‘Oberhaunstadter’) BFT, or non-tannin ‘Monarch’ CMV, all similar in forage nutritive value to alfalfa. Liveweight gain in 2008 averaged 1.42, 1.35, and 1.65 kg/d on CMV, low- and medium-tannin BFT, respectively, and in 2009, 1.04, 1.26, and 1.50 kg/d on these legume pastures. Cattle omega-6 to omega-3 blood fatty acid ratio was higher on BFT than CMV pastures but lower than on silage-hay diets. Irrigated birdsfoot trefoil with medium concentrations of tannins has potential in the northern Mountain West to provide high-quality forage to growing cattle.