Splanchnic and Mammary Nitrogen Metabolism by Dairy Cows Fed Dry-Rolled or Steam-Flaked Sorghum Grain

Abstract

Objectives were to determine net release or uptake of alpha-amino N, ammonia N, and urea N across portal-drained viscera, liver, splanchnic, and mammary tissues of lactating Holstein cows (n = 8, 86 +/- 8 d in milk) fed alfalfa hay-based total mixed rations containing 40% dry-rolled or steam-flaked sorghum grain. The total mixed rations were offered at 12-h intervals in a crossover design. Blood samples were obtained from indwelling catheters in the portal, hepatic, and mammary veins and mesenteric or costoabdominal arteries, every 2 h for each cow and diet. Steam-flaking increased in vitro rate of starch hydrolysis compared with dry-rolled sorghum (66 vs. 25%). Diet did not alter dry matter intake (18.2 +/- 0.3 kg). Daily milk yield (27.6 +/- 0.8 kg), efficiency of production, and most milk components did not differ between diets, but fat yield was reduced (0.86 vs. 0.91 kg/d) by steam-flaked sorghum, and lactose concentration was increased (4.99 vs. 4.82%). Blood flows in portal and hepatic veins did not differ between diets. Steam-flaking tended to increase urea N cycling to the gut (162 vs. 95 g/d) compared with dry-rolling of sorghum, whereas net absorption of ammonia N and alpha-amino N across portal-drained viscera were decreased. Net mammary uptake of a-amino N increased more than 20% (83 vs. 67 g/d), resulting in a higher mammary extraction ratio (15 vs. 11%) for steam-flaked versus dry-rolled sorghum. Flaking of sorghum improved the efficiency of postabsorptive N metabolism by increasing urea N cycled to the gut and alpha-amino N uptake by the mammary gland.

Effect of feeding microwave irradiated sorghum grain on nutrient utilization, rumen fermentation and serum metabolites in sheep

“…Improved starch utilization of steam processed sorghum grain by finishing cattle (Brandt Jr et al, 1992;Theurer et al, 1999) and dairy cattle (Theurer et al, 2001;Delgado-Elorduy et al, 2002;Nikkhah et al, 2004) has been also well studied and demonstrated previously.…”

Urea and short-chain fatty acids metabolism in Holstein cows fed a low-nitrogen grass-based diet

“…The butyrate fermentation following intake of grass with high sugar content might be part of the explanation for the typical decreasing milk production and milk fat production experienced when cows start to graze in the spring. In an experiment with intraruminal infusion of Figure 4 Portal-drained visceral (PDV) extraction of arterial urea-nitrogen in lactating dairy cows plotted against the arterial concentration of urea-N. Means from the following studies were used to establish the regression line (R 2 5 0.50) closed square (Reynolds et al, 2003); closed triangle up (Benson et al, 2002); closed triangle down (Blouin et al, 2002); closed diamond (Delgado-Elorduy et al, 2002a); closed hexagon (Delgado-Elorduy et al, 2002b); open square (Casse et al, 1994); open triangle down (Bach et al, 2000); open triangle up (Berthiaume et al, 2006); closed circle (Reynolds et al, 1988b); and open circle (Raggio et al, 2004). The mean PDV extraction of urea-N observed in the present study is indicated as an open diamond.…”

Evidence for the functional involvement of members of the TRP channel family in the uptake of Na+ and NH4 + by the ruminal epithelium

“…Livestock are estimated to account for almost 50 % of global ammonia emissions, cattle alone for about 30 % [8,12]. The greater part of these ammonia emissions are related to the rapid microbial degradation of dietary protein into ammonia, with the amounts absorbed exceeding 20 mol·day −1 in high yielding animals [15]. Although a variable percentage of the urea that is formed can be recycled to the gut, large quantities are renally excreted and thus lost as a source of nitrogen for microbial protein synthesis [23,52].…”