|Powell, J Mark|
Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/15/2010
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: The objective of this study was to determine the effect of varying alfalfa silage (AS) to corn silage (CS) ratios in a total mixed ration on performance of lactating cows and methane (CH4) emission. Sixteen multiparous Holstein cows (mean±SD; 77±35 days in milk and 640±84 kg body weight) housed in a modified tie-stall barn with four air-flow controlled chambers designed to accommodate four cows per chamber were fed diets with 20:80 (AS20), 40:60 (AS40), 60:40 (AS60), and 80:20 (AS80) CS:AS ratio in a 55:45 forage:concentrate ratio (DM basis) diet in a balanced 4 x 4 Latin square. Methane was measured in inlet and outlet air samples with a photo-acoustic multi-gas monitor (Innova Model 1412) for about 17 h/d on three consecutive days of each period. The aNDFom content of diet DM averaged 27.1, 27.3, 27.6, and 27.8% and NFC content of diet DM averaged 46.4, 44.9, 43.5, and 42.0% for AS20, AS40, AS60, and AS80, respectively. No effect was observed for DMI (26.6±0.3 kg/d), milk yield (41.0±0.4 kg/d), feed efficiency (kg milk yield/ kg DMI; 1.56±0.02), fat content (37.8±0.58 g/kg), MUN (16.2±0.2 mg/dL), and CH4 per energy corrected milk (ECM) (17.5±0.5 g/kg). A quadratic response (P<0.05) was observed for ECM and milk fat yield, which averaged 41.2, 42.7, 42.0, and 41.2 kg/d and 1.51, 1.61, 1.57, and 1.53 kg/d for AS20, AS40, AS60 and AS80, respectively. True milk protein content and yield decreased linearly (P<0.05) from 30.3 g/kg in AS20 to 28.9 g/kg in AS80 and 12.2 g/d in AS20 to 11.7 g/d in AS80. Estimated CH4 emission averaged 711, 764, 749, and 698 g/d and estimated CH4 per DMI averaged 26.1, 27.7, 27.0, and 25.0 g/kg. A quadratic response (P<0.05) was observed for the above emission rates with the greatest response for 40AS and the lowest 80AS with a difference of 7% for CH4 g/d and 10% for CH4 per DMI between extremes. In contrast greatest ECM was observed for 40AS and lowest for 80AS with a difference of 4%. Our results suggest that large substitutions between AS and CS in the diet impact CH4 emission and cow performance quadratically. However, the ratio of AS and CS does not seem effect methane emitted per kg ECM produced.