Lactating Holstein dairy cows, fitted with appropriate blood vessel catheters, were used in two cross-over experiments to investigate effects of feeding diets with 40% steam-flaked (28 lb/bu; SF) vs dry-rolled (DR) sorghum (experiment 1; 8 cows), or 40% steam-flaked corn grain (experiment 2; 6 cows) of different flake densities, 38 lb/bu (SF38) vs 28 lb/bu (SF28), on postabsorptive nutrient fluxes. Net uptake or output of glucose, L-lactate, volatile fatty acids (VFA) and β-hydroxybutyrate (BHBA) was measured across portal-drained viscera (PDV), hepatic, splanchnic and mammary tissues. Compared to DR, feeding cows SF sorghum increased net PDV absorption of propionate by 25% (P =.08), tended to increase splanchnic output of glucose (+16%) and L-lactate (+80%; P ≤ .20), but did not alter mammary glucose or L-lactate uptake. Sorghum processing did not affect net splanchnic or mammary metabolism of acetate and butyrate. Splanchnic output of BHBA was greater (P =.08), but mammary uptake was lower (P =.09) for cows fed DR vs SF diets. For cows fed corn diets, hepatic synthesis of glucose was higher (3.0 vs 2.8 kg/d; P =.04) for SF28 vs SF38. Flake density did not affect net splanchnic or mammary metabolism of acetate. For cows fed SF38, higher (P =.03) net PDV absorption of butyrate possibly inhibited hepatic gluconeogenesis from propionate, which might explain a higher (P =.10) hepatic uptake of L-lactate. Processing of corn or sorghum did not alter estimated total net PDV absorption or total splanchnic output of energy. Net total PDV absorption of VFA tended to be greater for cows fed SF than DR (+17%; P =.17), and for SF38 than SF28 (+10%; P =.15). Total mammary uptake of energy was not different for DR vs SF, but was greater for cows fed SF28 vs SF38, due mainly to increased uptake of glucose (+25%; P < .01). In both experiments, hepatic glucose synthesis was more than adequate for milk lactose production. These changes in partitioning of nutrients and estimated energy across portal-drained viscera, liver, total splanchnic, and mammary tissues may partially explain increased milk protein synthesis (in longer term lactation studies) by dairy cows fed more extensively processed corn (SF28) and sorghum (SF) grain.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/289278 |
| Date | January 1997 |
| Creators | Sadik, Mohamad Shabir, 1959- |
| Contributors | Theurer, C. Brent |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | text, Dissertation-Reproduction (electronic) |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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