Influence of Processed Corn Grain in Diets of Dairy Cows on Digestion of Nutrients and Milk Composition

Abstract

Five primiparous Holstein cows (55 d in milk) that were fitted with ruminal and duodenal cannulas were used in a 4 x 5 incomplete Latin square to determine the effects of blends of steam-flaked and dry-rolled corn on site and extent of nutrient digestion and milk yield and composition. Diets were fed as total mixed rations and consisted of 45% forage and 55% concentrate; each diet contained 27% corn grain. Dietary treatments were composed of blends of dry-rolled and steam-flaked corn in ratios of 100:0, 67:33, 33:67, and 0:100. Intake of dry matter; digestibilities of dry matter, organic matter, acid detergent fiber, cellulose, neutral detergent fiber, fatty acids, and N; and microbial efficiency were unaffected by diet. Ruminal, postruminal, and total tract digestion of starch increased linearly, and starch passage to the duodenum decreased linearly, as the proportion of dry-rolled corn in the diet decreased. Ruminal propionate and valerate increased linearly, and acetate, butyrate, isovalerate, and the acetate to propionate ratio decreased linearly, as proportions of dry-rolled corn in the diet decreased; however, no changes in total volatile fatty acid concentrations in ruminal fluid were observed. Ruminal fluid pH was similar across diets. A decrease in dry-rolled corn decreased ruminal ammonia N and plasma urea N linearly. Milk yield and composition, as well as milk N fractions, were similar across diets. Although changes in fatty acid composition of milk fat were small, linear decreases in percentages of trans-C16:1 and cis-9- and cis-10-C18:1, as well as a linear increase in the percentage of C18:2 occurred as the proportion of dry-rolled corn in the diet decreased. An increased proportion of dry-rolled corn in the diet decreased digestion of starch in the rumen, and patterns of volatile fatty acid concentrations shifted accordingly. However, no effects on lactational parameters were observed.

Comparison of Two Products of Direct-Fed Microbial Supplementation on the Nutrient Utilization and Ruminal Fermentation in Sheep

“…A decrease in NH 3 concentration is attributed to ruminal microbial proliferation, due to the increase of microbial use of available NH 3 for microbial N synthesis (Crocker et al, 1998). Some of the DFM e.g.…”

Impacts of feeding lipid supplements high in palmitic acid or stearic acid on performance of lactating dairy cows

“…The P in feed was determined according to a Technicon autoanalyzer method N-4C (Kraml 1966). Total FA content and composition of lipid supplements, diets, and feces were determined according to the procedures of Joy et al (1997), as modified by Crocker et al (1998). Ammonia-N and FA in rumen fluid were determined by the methods of Joy et al (1997).…”

“…Thus diets were similar in chemical composition (Table 3), except for the FA composition (Table 4). Chromic oxide was added to each TMR during mixing at 1 g/kg (as fed basis) of the TMR, as an external indigestibility marker to determine whole-tract apparent digestibility based on the method reported by Crocker et al (1998).…”

Assessment of the mobile bag method for estimation of in vivo starch digestibility

“…The proportion of starch that escapes rumen degradation ranges from 50 to 650 g/kg of starch intake (Huntington, 1997;Crocker et al, 1998). Technological treatments (grinding, cracking, steam flaking, pelleting, extrusion, expander processing and chemical treatment) can have a significant effect on ruminal starch degradability, resulting in significant amounts of starch escaping the rumen and entering the small intestine (Tothi et al, 2003;Larsen et al, 2009).…”