Interaction of molasses and monensin in alfalfa hay- or corn silage-based diets on rumen fermentation, total tract digestibility, and milk production by Holstein cows

Abstract

Sugar supplementation can stimulate rumen microbial growth and possibly fiber digestibility; however, excess ruminal carbohydrate availability relative to rumen-degradable protein (RDP) can promote energy spilling by microbes, decrease rumen pH, or depress fiber digestibility. Both RDP supply and rumen pH might be altered by forage source and monensin. Therefore, the objective of this study was to evaluate interactions of a sugar source (molasses) with monensin and 2 forage sources on rumen fermentation, total tract digestibility, and production and fatty acid composition of milk. Seven ruminally cannulated lactating Holstein cows were used in a 5 x 7 incomplete Latin square design with five 28-d periods. Four corn silage diets consisted of 1) control (C), 2) 2.6% molasses (M), 3) 2.6% molasses plus 0.45% urea (MU), or 4) 2.6% molasses plus 0.45% urea plus monensin sodium (Rumensin, at the intermediate dosage from the label, 16 g/909 kg of dry matter; MUR). Three chopped alfalfa hay diets consisted of 1) control (C), 2) 2.6% molasses (M), or 3) 2.6% molasses plus Rumensin (MR). Urea was added to corn silage diets to provide RDP comparable to alfalfa hay diets with no urea. Corn silage C and M diets were balanced to have 16.2% crude protein; and the remaining diets, 17.2% crude protein. Dry matter intake was not affected by treatment, but there was a trend for lower milk production in alfalfa hay diets compared with corn silage diets. Despite increased total volatile fatty acid and acetate concentrations in the rumen, total tract organic matter digestibility was lower for alfalfa hay-fed cows. Rumensin did not affect volatile fatty acid concentrations but decreased milk fat from 3.22 to 2.72% in corn silage diets but less in alfalfa hay diets. Medium-chain milk fatty acids (% of total fat) were lower for alfalfa hay compared with corn silage diets, and short-chain milk fatty acids tended to decrease when Rumensin was added. In whole rumen contents, concentrations of trans-10, cis-12 C(18:2) were increased when cows were fed corn silage diets. Rumensin had no effect on conjugated linoleic acid isomers in either milk or rumen contents but tended to increase the concentration of trans-10 C(18:1) in rumen samples. Molasses with urea increased ruminal NH(3)-N and milk urea N when cows were fed corn silage diets (6.8 vs. 11.3 and 7.6 vs. 12.0 mg/dL for M vs. MU, respectively). Based on ruminal fermentation characteristics and fatty acid isomers in milk, molasses did not appear to promote ruminal acidosis or milk fat depression. However, combinations of Rumensin with corn silage-based diets already containing molasses and with a relatively high nonfiber carbohydrate:forage neutral detergent fiber ratio influenced biohydrogenation characteristics that are indicators of increased risk for milk fat depression.

Effect of Nutrition on Production, Composition, Fatty acids and Nutraceutical Properties of Milk

“…Alfalfa hay as a sole source of forage in diets may alleviate effects of dietary treatments on rumen condition and rapid fermentation by inhibiting lactic acid producing bacteria and there by sustaining stable rumen environment. Oelker et al [28] observed that any changes in rumen pH with alfalfa hay relative to corn silage based diets decreased the accumulation of biohydrogenation intermediates and thereby total CLA content in rumen of Holstein dairy cows. Rumen microbial enzymes are responsible for the isomerisation and hydrolysis of dietary lipid and the conversion of unsaturated fatty acids to various partially and fully saturated derivatives, including CLA (C18:2 cis-9, t-11) (c), trans vaccenic acid (C18:1 t-11) (VA) and stearic acid (C18:0).…”

Response of sheep fed on corn cob silage or elephant grass basal diet with or without Calliandra leaf meal supplementation

“…This pH was in the range (6.5-7.0) of ideal condition for microbial activities in the rumen for fiber and protein digestion (Wanapat & Cherdthong 2009;Calabro et al 2008). Oelker et al (2009) also reported similar ruminal pH of cows fed on corn silage or chopped alfalfa hay. Rumen ammonia (NH3-N) was significantly higher in grass basal diet than the CCS diet.…”

Replacing maize grain with dried citrus pulp in a concentrate feed for Jersey cows grazing ryegrass pasture

“…The propionate concentration was not different between the NDCP and HDCP treatments, and does not provide an explanation for the decrease in milk yield when maize was replaced with DCP. Increased levels of sugar in the diet have been shown to decrease the acetate concentration (Khalili & Huhtanen, 1991;Chamberlain et al, 1993;Broderick et al, 2008), increase butyrate concentration (Khalili & Huhtanen, 1991, Chamberlain et al, 1993 and result in no change in acetate concentration or the acetate: propionate ratio (Khalili & Huhtanen, 1991;Leiva et al, 2000;Oelker et al, 2009). In theory, the replacement of maize with DCP should lead to a change in the VFA profile of the rumen.…”