Nitrogen excretion and greenhouse gas emissions from manure of tropical cattle supplemented with either leguminous forage or concentrates
Naomi Chepsuge1, Sonja Leitner2, James Ondiek3, Daniel Korir4, C. Arndt5
1Egerton University, Animal Science, Kenya
Protein supplementation is a feeding strategy widely adopted by Kenyan dairy farmers to improve milk productivity. It not only reduces enteric methane (CH4) emission intensities but also increases nitrogen (N) excretion and manure greenhouse gas (GHG) emissions. There’s need therefore, to account for manure emissions when evaluating its mitigation potential. In Kenya, commercial concentrates and leguminous forages are the commonly used protein sources, but little is known on their impacts on manure GHG emissions. The present study compared urine and faecal N, manure composition and manure CH4 and nitrous oxide (N2O) emissions from incubated manure collected from lactating cows fed on a basal diet of Brachiaria hay (control) and supplemented with either Desmodium intortum (tanninferous leguminous forage) or dairy cubes (concentrate). Manure was prepared per animal per dietary treatment based on the excretion ratio and incubated in 1 L mason jars at 200 C for 84 days. Dairy cube and Desmodium supplemented diets increased (P<.0001) total N excreted by 39 and 19% compared with the control diet (128 ± 6.93 and 96.6 ± 3.03 Vs 78.6 ± 1.69 g day-1). Desmodium supplemented diet decreased urinary N by 23%, while dairy cube supplemented diet increased by 12 % compared with the control diet, P <.0001 (35.3 ± 0.88 and 52.1 ± 0.67 Vs 45.7 ± 1.45 % of total N). During incubation higher N losses (P= 0.0005) were observed in manure from cows fed dairy cube supplemented diet compared with Desmodium (19.6 ± 2.52 Vs 7.27 ± 1 53 %). There was no dietary effect on the cumulative manure CH4 (P=0.0909) and N2O emissions (P=0.1890).
Keywords: Condensed tannins, Desmodium intortum, laboratory manure incubation, manure greenhouse gas emissions, protein supplementation
Contact Address: Naomi Chepsuge, Egerton University, Animal Science, 536-20115, Njoro, Kenya, e-mail: naomilagtgmail.com