Effect of tannin-containing hays on enteric methane emissions and nitrogen partitioning in beef cattle
Citation
Stewart, E.K., Beauchemin, K.A., Dai, X., MacAdam, J.W., Christensen, R.G., Villalba, J.J. (2019). Effect of tannin-containing hays on enteric methane emissions and nitrogen partitioning in beef cattle. Journal of Animal Science, [online] 97(8), 3286-3299. http://dx.doi.org/10.1093/jas/skz206
Plain language summary
One of the challenges emerging from an increasing number of livestock is the concomitant increase in the production of greenhouse gases, including methane emissions. Approximately 80% of the greenhouse gas emissions from beef production occur during the cow–calf phase. Thus, mitigation of greenhouse gas emissions
from beef production during the cow–calf phase is crucial to reducing the greenhouse gas inventories. Feeds containing natural phytocompounds such as condensed and hydrolysable tannins represent a sustainable means of reducing environmental impacts of ruminants; tannin-containing feeds reduce enteric methane emissions and urinary nitrogen excretion in some cases. It is not known whether this bioactivity is maintained when hay is produced, compared with grazing pastures. The objective of this study was to determine
whether feeding tannin-containing hays to mature beef cows and yearling heifers influences enteric
methane emissions and nitrogen excretion relative to feeding non-tannin-containing hays.The results
suggest that tannin-containing hays have the potential to reduce urinary urea nitrogen excretion and reduce enteric methane emissions from beef cattle.
Abstract
The objective of this study was to determine whether feeding tannin-containing hays to heifers and mature beef cows influences enteric methane (CH4) emissions and nitrogen (N) excretion relative to feeding traditional legume and grass hays. Fifteen mature beef cows (Exp. 1) and 9 yearling heifers (Exp. 2) were each randomly assigned to treatment groups in an incomplete bock design with 2 periods and 6 types of hays with 3 hays fed each period (n = 5 cows and 3 heifers per treatment). Groups were fed tannin-containing [birdsfoot trefoil (BFT), sainfoin (SAN), small burnet (SML)] or non-tannin-containing [alfalfa (ALF), cicer milkvetch (CMV), meadow bromegrass (MB)] hays. Each period consisted of 14 d of adjustment followed by 5 d of sample collection. Nine cows and 9 heifers were selected for the measurement of enteric CH4 emissions (sulfur hexafluoride tracer gas technique), and excretion of feces and urine, while dry matter intake (DMI) was measured for all animals. The concentration of condensed tannins in SAN and BFT was 2.5 ± 0.50% and 0.6 ± 0.09% of dry matter (DM), respectively, while SML contained hydrolyzable tannins (4.5 ± 0.55% of DM). Cows and heifers fed tannin-containing hays excreted less urinary urea N (g/d; P < 0.001) and showed lower concentrations of blood urea N (mg/dL; P < 0.001) than animals fed ALF or CMV, indicating that tannins led to a shift in route of N excretion from urine to feces. Additionally, cows fed either BFT or CMV showed the greatest percentage of retained N (P < 0.001). Enteric CH4 yield (g/kg of DMI) from heifers (P = 0.089) was greatest for MB, while daily CH4 production (g/d) from heifers (P = 0.054) was least for SML. However, digestibility of crude protein was reduced for cows (P < 0.001) and heifers (P < 0.001) consuming SML. The results suggest that tannin-containing hays have the potential to reduce urinary urea N excretion, increase N retention, and reduce enteric CH4 emissions from beef cattle. The non-bloating tannin-free legume CMV may also reduce environmental impacts relative to ALF and MB hays by reducing N excretion in urine and increasing N retention.