title: Prediction of enteric methane output from milk fatty acid concentrations and rumen fermentation parameters in dairy cows fed sunflower, flax, or canola seeds.
abstract: Milk fatty acid (FA) composition has been suggested as a means of predicting enteric methane (CH₄) output in lactating dairy cattle because of the common biochemical pathways among CH₄, acetate, and butyrate in the rumen. Sixteen lactating Holstein cows were used in a Latin square design with four 28-d periods. All diets contained steam-rolled barley, a pelleted supplement, barley silage [45% of dietary dry matter (DM)] and 3.3% added fat (DM basis) from 1 of 4 sources: calcium salts of long-chain FA (palm oil; control) or crushed oilseeds from sunflower, flax, or canola. The objectives of this study were to (1) compare the effect of diets on milk FA profile; (2) model CH₄ production from milk FA composition, intake, and rumen fermentation variables; and (3) test the applicability of CH(4) prediction equations reported in previous studies. Methane (g/d) was measured in chambers (2 animals/chamber) on 3 consecutive days (d 21-23). The test variables included total DM intake (DMI, kg/d; d 21-23), forage DMI (kg/d; d 21-23), milk yield (kg/d; d 21-23), milk components (d 18-21), milk FA composition (% total FA methyl esters; d 18-21), rumen volatile FA (mol/100 mol; d 19-21), and protozoal counts (d 19-21), and were averaged by chamber and period to determine relationships between CH₄ and the test variables. Milk trans(t)10-, t11-18:1, and cis(c)9t11-18:2 were greater for sunflower seeds compared with the other diets. Forage DMI (correlation coefficient, r=0.52; n=32), DMI (r=0.52; n=32), and rumen acetate + butyrate:propionate (r=0.72; n=16) were positively related to CH₄ (g/d), whereas rumen propionate (r=0.63; n=16), milk c9-17:1 (r=0.64; n=32), and c11-18:1 (r=0.64; n=32) were negatively related to CH₄. The best regression equation (coefficient of determination=0.90; n=16) was CH₄ (g/d)=-910.8 (±156.7) × milk c9-17:1 + 331.2 (±88.8) × milk 16:0 iso + 0.0001 (±0.00) × total entodiniomorphs + 242.5 (±39.7). Removing rumen parameters from the model also resulted in a reasonably good estimate (coefficient of determination=0.83; n=32) of CH₄. Stepwise regression analysis within diets resulted in greater coefficient of determination and lower standard error values. Predictions of CH₄, using equations from previous studies for the data set from this study, resulted in a mean overestimation ranging from 19 to 61% across studies. Thus, milk FA alone may not be suitable for developing universal CH₄ prediction equations.
authors: Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, Alberta T1J 4B1, Canada.
authors: R
authors: R
authors: Mohammed
authors: S M
authors: SM
authors: McGinn
authors: K A
authors: KA
authors: Beauchemin
mesh_terms: D000821:Animal Feed; D000818:Animals; D029688:Brassica napus; D002417:Cattle; D004032:Diet / Q000662:veterinary*; D005227:Fatty Acids / Q000032:analysis*; D005260:Female; D005285:Fermentation / Q000187:drug effects* / Q000502:physiology; D019597:Flax; D006368:Helianthus; D008697:Methane / Q000096:biosynthesis*; D008892:Milk / Q000737:chemistry*; D012417:Rumen / Q000378:metabolism* / Q000502:physiology; D012639:Seeds
chemical_list: D005227:Fatty Acids; D008697:Methane