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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Dairy Forage Research » Research » Publications at this Location » Publication #308991

Research Project: Forage Characteristics that Alter Feed Utilization, Manure Characteristics and Environmental Impacts of Dairy Production

Location: Dairy Forage Research

Title: Performance, digestion, nitrogen balance, and emission of manure ammonia, enteric methane, and carbon dioxide in lactating cows fed diets with varying alfalfa silage-to-corn silage ratios

item ARNDT, C - University Of Wisconsin
item Powell, Joseph
item AGUERRE, MJ - University Of Wisconsin
item WATTIAUX, MA - University Of Wisconsin

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/6/2014
Publication Date: 1/5/2015
Publication URL:
Citation: Arndt, C., Powell, J.M., Aguerre, M., Wattiaux, M. 2015. Performance, digestion, nitrogen balance, and emission of manure ammonia, enteric methane, and carbon dioxide in lactating cows fed diets with varying alfalfa silage-to-corn silage ratios. Journal of Dairy Science. 98(1):418-430.

Interpretive Summary: Alfalfa silage and corn silage are typical feedstuffs on U.S. dairy farms. However, the ratio in which they are fed varies greatly. This experiment compared impacts of the alfalfa silage to corn silage ratio on milk production and quality, the efficiency of feed protein conversion into milk protein, and gaseous emissions from dairy barns. Dietary treatments did not affect dry matter intake, dry matter digestibility, milk production, or milk production per unit of dry matter intake. The excretion of nitrogen in total manure, feces and urine was less as more corn silage and less alfalfa silage was fed. Emissions of ammonia and methane per pound of fat- and protein-corrected milk remained unaffected by diet. This information can be used to formulate diets that maximize milk production and feed nitrogen use, and minimize nitrogen excretion and the environmental impacts of milk production.

Technical Abstract: Two trials were conducted simultaneously to study the effect of alfalfa silage (AS) to corn silage (CS) ratio in the diet of lactating dairy cows on performance, digestibility, ruminal parameters, nitrogen (N) balance, manure production and composition, and gaseous emissions [carbon dioxide (CO2), methane (CH4), and ammonia-N (NH3-N)]. In trial 1 all measurements, except gas emissions, were conducted on 8 rumen-cannulated cows in replicated 4 x 4 Latin squares. In trial 2, performance and emissions were measured on 16 cows randomly assigned to one of four air-flow controlled chambers in a 4 x 4 Latin square. Dietary treatments were fed as total mixed rations with forage to concentrate ratio of 55:45 [dietary dry matter (DM) basis] and AS:CS ratios of 20:80, 40:60, 60:40, and 80:20 (forage DM basis). Gas measurements were conducted the last 3 days of each 21-d replicate period. Dietary treatments did not affect DM intake, DM digestibility, and milk/DM intake. However, animal responses were quadratic for fat-and-protein corrected milk, fat, and protein production, which reached predicted maxima for AS:CS ratio treatments 50:50, 49:51, and 34:66. Nitrogen use efficiency (milk N/N intake) decreased from 31 to 24 g/100g as AS:CS ratio increased from 20:80 to 80:20. Dietary treatments tended to have a quadratic effect on NH3-N emissions but did not alter NH3-N/milk-N. Treatments impacted CH4 and CO2 emission per unit of neutral detergent fiber (NDF) intake. Ruminal acetate to propionate ratio and total tract NDF digestibility increased linearly with increasing AS:CS ratio. Although NDF digestion increased linearly between 2.54 to 3.59 kg/d, CH4/digested NDF decreased linearly from 270 to 190 g/kg as AS:CS ratio changed from 20:80 to 80:20. These two antagonistic digestive processes likely contributed to the observed increase in CH4 emissions, which may have been influenced also by increasing starch with increasing CS in the diet as reflected by the increased ruminal propionate molar proportion. Overall, production performances were greatest for the intermediate AS:CS ratio, but daily excretion of urine, manure, fecal N, urinary urea N, and urinary N decreased as more CS was fed. The proportion of AS and CS in the diet did not significantly impact CH4/fat-and-protein corrected milk.