Increasing the concentration of linolenic acid in diets fed to Jersey cows in late lactation does not affect methane production

摘要

Although the inclusion of fat has reduced methaneproduction in ruminants, relatively little research hasbeen conducted comparing the effects of source andprofile of fatty acids on methane production in lactatingdairy cows. A study using 8 multiparous (325 ± 17DIM; mean ± SD) lactating Jersey cows was conductedto determine effects of feeding canola meal and lardversus extruded byproduct containing flaxseed as ahigh-C18:3 fat source on methane production and dietdigestibility in late-lactation dairy cows. A crossoverdesign with 32-d periods (28-d adaptation and 4-d collections)was used to compare 2 different fat sources.Diets contained approximately 50% forage mixture ofcorn silage, alfalfa hay, and brome hay; the concentratemixture changed between diets to include either (1) aconventional diet of corn, soybean meal, and canolameal with lard (control) or (2) a conventional diet ofcorn and soybean meal with an extruded byproductcontaining flaxseed (EXF) as the fat source. Diets werebalanced to decrease corn, lard, and canola meal andreplace them with soybean mean and EXF to increasethe concentration of C18:3 (0.14 vs. 1.20% of DM).Methane production was measured using headbox-styleindirect calorimeters. Cattle were restricted to 95% adlibitum feed intake during collections. Milk production(17.4 ± 1.04 kg/d) and dry matter intake (15.4 ± 0.71kg/d) were similar among treatments. Milk fat (5.88 ±0.25%) and protein (4.08 ± 0.14%) were not affectedby treatment. For methane production, no differencewas observed for total production (352.0 vs. 349.8 ±16.43 L/d for control vs. EXF, respectively). Methaneproduction per unit of dry matter intake was not affectedand averaged 23.1 ± 0.57 L/kg. Similarly, methaneproduction per unit of energy-corrected milk wasnot affected by fat source and averaged 15.5 ± 0.68L/kg. Heat production was similar, averaging 21.1 ±1.02 Mcal/d. Digestibility of organic matter, neutraldetergent fiber, and crude protein was not affected bydiet and averaged 69.9, 53.6, and 73.3%, respectively.Results indicated that increasing C18:3 may not affectmethane production or digestibility of the diet in lactatingdairy cows.