Effects of dietary starch content and rate of fermentation on methane production in lactating dairy cows

Abstract

The objective of this study was to investigate the effects of starch varying in rate of fermentation and level of inclusion in the diet in exchange for fiber on methane (CH4) production of dairy cows. Forty Holstein-Friesian lactating dairy cows of which 16 were rumen cannulated were grouped in 10 blocks of 4 cows each. Cows received diets consisting of 60% grass silage and 40% concentrate (dry matter basis). Cows within block were randomly assigned to 1 of 4 different diets composed of concentrates that varied in rate of starch fermentation [slowly (S) vs. rapidly (R) rumen fermentable; native vs. gelatinized corn grain] and level of starch (low vs. high; 270 vs. 530g/kg of concentrate dry matter). Results of rumen in situ incubations confirmed that the fractional rate of degradation of starch was higher for R than S starch. Effective rumen degradability of organic matter was higher for high than low starch and also higher for R than S starch. Increased level of starch, but not starch fermentability, decreased dry matter intake and daily CH4 production. Milk yield (mean 24.0±1.02kg/d), milk fat content (mean 5.05±0.16%), and milk protein content (mean 3.64±0.05%) did not differ between diets. Methane expressed per kilogram of fat- and protein-corrected milk, per kilogram of dry matter intake, or as a fraction of gross energy intake did not differ between diets. Methane expressed per kilogram of estimated rumen-fermentable organic matter (eRFOM) was higher for S than R starch-based diets (47.4 vs. 42.6g/kg of eRFOM) and for low than high starch-based diets (46.9 vs. 43.1g/kg of eRFOM). Apparent total-tract digestibility of neutral detergent fiber and crude protein were not affected by diets, but starch digestibility was higher for diets based on R starch (97.2%) compared with S starch (95.5%). Both total volatile fatty acid concentration (109.2 vs. 97.5mM) and propionate proportion (16.5 vs. 15.8mol/100mol) were higher for R starch- compared with S starch-based diets but unaffected by the level of starch. Total N excretion in feces plus urine and N retained were unaffected by dietary treatments, and similarly energy intake and output of energy in milk expressed per unit of metabolic body weight were not affected by treatments. In conclusion, an increased rate of starch fermentation and increased level of starch in the diet of dairy cattle reduced CH4 produced per unit of eRFOM but did not affect CH4 production per unit of feed dry matter intake or per unit of milk produced.

Relationship between in vitro and in vivo methane production measured simultaneously with different dietary starch sources and starch levels in dairy cattle

“…Different levels of starch in the concentrates were achieved by exchanging either native or gelatinized maize grain with fibrous material (beet pulp and palm kernel expeller) on a DM basis. The ingredient composition of the concentrates was reported by Hatew et al (2015). The main starch source (i.e.…”

“…Correlations were analyzed with in vivo CH 4 production expressed in ml per gram of OM consumed, ml per gram of OM digested, and ml per gram of estimated rumen-fermentable organic matter (eRFOM). Details for determination of total-tract apparent digestibility and eRFOM have been reported by Hatew et al (2015).…”

“…Cows had unrestricted access to drinking water. The 16 rumen fistulated cows were part of a larger experiment to investigate effect of starch level and starch source on CH 4 production including 24 non-fistulated animals (Hatew et al, 2015).…”

“…Diet and substrate samples were freeze-dried, ground using a Wiley mill fitted with a 1-mm sieve and analyzed for DM, ash, N, crude fat, starch, sugar, gross energy, neutral detergent fiber (aNDFom; after a pre-treatment with a heat stable amylase and expressed excluding residual ash), and acid detergent fiber (ADFom; expressed excluding residual ash) following the standard procedures previously reported (Hatew et al, 2015).…”

Starch in ruminant diets: a review

“…Pirondini et al (2015) evaluated the effect of starch (23.7 and 27.7% DM) on methane emissions in dairy cows, finding lower emissions for starch-rich diets (415 vs. 396 g/d, respectively). Finally, Hatew et al (2015) investigated the effect of starch (270 vs. 530 g/Kg concentrate DM) and fermentation rate (fast vs. slow) in dairy cows. They found no differences in methane produced per Kg of fat-corrected milk and protein, or per Kg DM consumed, or as a fraction of the gross energy consumed.…”