Author
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Klotz, James |
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HEITMANN, RICHARD - UNIV. OF TENNESSEE |
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Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/1/2006 Publication Date: 3/1/2007 Citation: Klotz, J.L., Heitmann, R.N. 2007. Changes in net portal nutrient flux in response to weaning transition and ionohore supplementation in dairy calves. Journal of Dairy Science. 90:1326-1339. Interpretive Summary: In response to dietary changes associated with weaning, the alimentary tract of the calf undergoes pronounced anatomic, morphologic, and metabolic transformations. Further characterization of the developmental changes that occur was done using pre- and post-weaning measures of net metabolite and hormone flux across the gut and liver tissue beds. This study quantitatively demonstrated changes in metabolism that occur during the transition from preruminant to ruminant and how these changes are influenced by supplementation of an ionophore. These data contribute to an improved understanding of gut development, which benefits replacement heifer programs. Technical Abstract: Dairy calf weaning is associated with ketone concentrations that exceed concentrations occurring in adults and present a potential energy loss that may be mitigated by ionophore supplementation. To assess effects of weaning and ionophore supplementation on net nutrient flux across portal-drained viscera (PDV) tissues in dairy calves, glucose, acetoacetate (ACAC), '-hydroxybutyrate (BHBA), non-esterified fatty acids (NEFA), volatile fatty acids (VFA), lactate, pyruvate, insulin (INS), and glucagon concentrations and PDV flux rates were determined on d 35, 56, 84, and 112 of age in Jersey bull calves (n = 19). Calves were randomly assigned at birth to either a commercial pelleted starter without (CON) or with lasalocid (TRT; 83 mg/kg DM). Calves were fed milk replacer only from d 3 to d 34 (d 3 to 20 = 454 g/d; d 21 to 34 = 568 g/d), after blood sampling on d 35, calves received replacer (d 35 to 41 = 454 g/d; d 42 to 48 = 227 g/d) and free access to CON or TRT starter, and from d 49 to 112 received ad libitum CON or TRT. Calves were fitted with catheters in portal vein and mesenteric vein and artery between d 21 and 28. Blood flow was measured by continuous infusion of para-aminohippurate into the mesenteric vein. Six serial samples were taken at 30-min intervals simultaneously from the arterial and portal vein catheters. Portal blood flow increased with age, but did not differ between CON and TRT. Glucose was released pre-weaning and extracted post-weaning by PDV, but not affected by ionophore. The net portal flux of NEFA was not different from zero during any of the four sample ages. Fluxes of ACAC and BHBA in CON and TRT went from no measurable flux pre-weaning to a post-weaning PDV release that peaked at d 84, but d 84 release of ACAC and BHBA were lower in TRT (P < 0.05). Net portal flux of VFA increased with age and both butyrate and propionate PDV release were lower at d 84 in TRT than CON (P < 0.05). However, TRT calves had a greater PDV release of lactate on d 84 partially compensating for lower release of propionate (P < 0.05). Glucagon was greater in CON than TRT at d 84 and could be a response to the elevated ketogenesis in CON calves observed during this period. Substantial changes in metabolic profile and net nutrient flux of transition calves in response to weaning and ionophore supplementation were demonstrated. Inclusion of an ionophore appears to moderate alimentary output at a post-weaning period (d 84) where ketone concentrations have potential to exceed whole animal capacity for utilization. |
