Dietary forage to concentrate ratio and sunflower oil supplement alter rumen fermentation, ruminal methane emissions, and nutrient utilization in lactating cows1

Abstract

The effects of supplementing high- or low-concentrate diets with sunflower oil (SO) on rumen fermentation, nutrient utilization, and ruminal methane (CH4) emissions in lactating cows were examined. Four multiparous Nordic Red dairy cows fitted with rumen cannulae were used in a 4 × 4 Latin square with a 2 × 2 factorial arrangement of treatments and 35-d periods. Experimental treatments comprised iso-nitrogenous total mixed rations based on grass silage with forage to concentrate ratio of 65:35 or 35:65 supplemented with 0 or 50 g/kg diet DM of SO. Apparent ruminal OM and starch digestibility was greater (P < 0.05) with high- than low-concentrate diets but was unaffected by SO. Inclusion of SO in high-concentrate diet decreased (P ≤ 0.05) apparent total tract OM, fiber, and GE, and apparent ruminal fiber digestibility. High-concentrate diets and SO shifted (P < 0.05) fiber digestion from rumen to the hindgut. High-concentrate diet resulted in a lower rumen pH and elevated total rumen VFA concentration compared with low-concentrate diet, whereas SO increased rumen pH and decreased rumen VFA concentration when included in high-, but not low-concentrate diet (P < 0.05 for interaction). High-concentrate diet reduced rumen ammonia-N (P < 0.01) and molar proportion of acetate to propionate (P < 0.01), and decreased (P < 0.05) ruminal CH4 emissions when expressed as g/d or g/kg OM digested in the rumen. With both low- and high-concentrate diets, SO reduced (P < 0.05) daily emissions of CH4 as g/d or g/kg OM digested in the rumen, but SO reduced CH4 emissions expressed as g/kg OM intake, OM digested in total digestive tract, energy-corrected milk or % of GE intake only with low-concentrate diet (P ≤ 0.05 for interaction). In conclusion, replacing grass silage with concentrates led to a reduction in daily ruminal CH4 emissions that were accompanied by a shift in rumen fermentation toward the synthesis of propionate, and decreases in rumen pH and fiber digestion. Sunflower oil was effective in reducing daily CH4 emissions in lactating cows which was accompanied by a noticeable lower feed intake with high- but not low-concentrate diet. Overall the effects of SO and greater proportion of concentrates in the diet on daily CH4 emissions were additive but the additivity declined or vanished when different indices of CH4 emission intensity were considered. Consequently, SO was more effective in reducing CH4 emissions when low-concentrate diet was fed.

Intake, digestibility, growth performance, and enteric methane emission of Brazilian semiarid non-descript breed goats fed diets with different forage to concentrate ratios

“…The decrease in NDF digestibility could be related to increased content of soluble nutrients as the forage:concentrate ratio decreased, which could reduce rumen pH and increase digesta passage rate, reducing fiber digestibility. Similar results were obtained by Ma et al (2014) and Bayat et al (2017) in sheep and cow, respectively.…”

Effect of dietary fat supplementation on methane emissions from dairy cows fed wheat or corn

“…For example, Chung et al (2011) reported that when Holstein cows were fed a diet based on whole-crop barley silage supplemented with 150 g/kg of DM of a high-fat linseed, MY was reduced by 33%, but there was no effect on MY when a high-fat linseed supplement was fed with a diet based on chopped grass hay. Similar results have been reported from an experiment by Bayat et al (2017), where sunflower oil fed at a rate of 50 g/kg DM to Nordic red dairy cows was more effective in reducing MY when concentrate constituted a low (35% of DM) proportion of the basal diet than when concentrate constituted a high (65% of DM) proportion. Our results indicate that the type of grain in the basal diet of dairy cows does not affect the methane mitigating effect of dietary fat.…”

“…The net effect would be increased methane production (Alstrup et al, 2015). In this context, studies by Moate et al (2017) and Bayat et al (2017), which reported lower MY than those observed in this study, used cows in peak lactation (71 and 89 DIM, respectively) compared with our study that used cows in late lactation (207 DIM).…”

Review: Strategies for enteric methane mitigation in cattle fed tropical forages

“…In their comprehensive review, Grainger and Beauchemin (2011) suggested that the mitigation potential of fats is 1 g CH 4 /kg DM intake for each 10 g fat/kg DM in the ration and this has shown persistent results, although no effect of the chain length of the fatty acids on the magnitude of mitigation has been detected. Feeding sunflower oil can effectively reduce enteric methane emissions of dairy cows (Bayat et al, 2017). Similar effects of vegetable oils on reducing methane emissions have been reported under in vitro conditions (Vargas et al, 2020).…”