|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: Our objective was to determine the effect of feeding diets with different forage to concentrate ratios (F:C) on performance and methane (CH4) emission from lactating dairy cows. Eight multiparous Holstein cows (means ± standard deviation: 620 ± 38 kg of body weight (BW); 41 ± 34 days in milk (DIM)) and 8 primiparous Holstein cows (546 ± 38 kg of BW; 75 ± 40 DIM) were blocked by parity and randomly assigned to one of four life-sized emission chambers, each constructed to house four cows in a modified tie-stall barn. Also, chambers were randomly assigned to one of four dietary treatments sequences in a single 4 x 4 Latin squares design. Dietary treatments, fed as total mixed rations, included the following F:C ratio: 47:53, 54:46, 61:39 and 68:32 (diet dry matter (DM) basis). Forage consisted of alfalfa silage and corn silage in a 1:1 ratio. Methane emissions were measured during the last 4 days of each period. Air samples entering and exiting each chamber were analyzed for CH4 concentration with a photo-acoustic field gas monitor (Innova Model 1412). Increasing F:C ratio had no effect on DM intake (20.2 ± 2.1 kg/cow/d), milk yield (37.7 ± 2.8 kg/cow/d), feed efficiency (milk/DM intake, 1.91 ± 0.24), milk fat content (3.70 ± 0.21 %) and yield (1.39 ± 0.01 kg/cow/d) and milk true protein yield (1.00 ± 0.06 kg/cow/d). Relative to 47:53 F:C ratio (2.73%), milk true protein content did not change (2.71%), but decreased to 2.66% (P<0.05) and 2.61% (P<0.05) when F:C ratio was 54:46, 61:39, and 68:32, respectively. Higher forage diet tended to increase CH4 emission (26.9 g/cow/hour, P=0.06 and 32.5 g/kg DM intake, P=0.07). Also, higher forage diet increased (P<0.01) the CH4 emission per unit of milk yield. Relative to the 47:53 F:C ratio diet, CH4 emission was increased by 13% in the intermediate forage inclusion rates (15.2 vs. 17.2 g/kg milk, respectively; P<0.05), the latter value being further increased (P<0.05) to 19.2 for the diet with 68:32 F:C ratio (a 26% increase compared with 47:53 F:C). There was a linear increase in CH4 emission rate, CH4 emission per unit of DM intake and CH4 emission per unit of milk yield with increasing levels of dietary F:C ratio (all Ps were <0.02). Under the conditions of this study, feeding higher levels of forage in the diet had negligible effects on animal performance and milk composition, but increased the CH4 emission.