title: Effect of the live weight gain of steers during winter grazing on digestibility, acid-base balance, blood flow, and oxygen consumption by splanchnic tissues during adaptation and subsequent feeding of a high-grain diet.
abstract: Ten multicatherized steers were used in a completely random design to determine the effect of previous BW gain on blood flow, acid-base balance, and oxygen consumption across portal-drained viscera and liver of growing beef steers fed a high-grain diet. Treatments were high (1.31 +/- 0.09 kg/d) or low (0.68 +/- 0.07 kg/d) daily BW gain during an 82-d winter wheat pasture grazing period and a subsequent 37-d transition period. Blood flow, blood gas measurements, and oxygen consumption were determined on d 0, 14, 28, 42, and 64 of a high-grain finishing period. Compensatory growth was evident in low-gain steers; ADG (1.50 vs. 1.11 kg/d, P < 0.05) and gain efficiency (0.221 vs. 0.109 kg/kg, P < 0.01) were greater from d 14 through 28 than for high-gain steers. Arterial base tended (P < 0.12) to be greater in low-gain than in high-gain steers, whereas calculated HCO3- (mmol/L; P < 0.20) did not differ between treatments. Arterial O2 concentration was not different (P < 0.97) between treatments but increased (P < 0.001) with increasing days on feed. Portal blood flow increased with days on feed (P < 0.001) but did not differ (P < 0.34) between treatments. Hepatic blood flow scaled to metabolic BW was 19.7% greater (P < 0.02) in low-gain than in high-gain steers. Across the feeding period, O2 consumption and CO2 flux by PDV, liver, and total splanchnic tissue (TST) did not differ (P < 0.33) between treatments. However, TST O2 consumption (mmol/[h x kg BW(0.75)]) tended (P < 0.12) to be greater in low- than in high-gain steers. Compensating steers' arterial blood acid-base measurements did not change with days on feed, indicating that they were not more susceptible to metabolic acidosis than high-gain steers. However, steers that had lower BW gain before high-grain feeding exhibited increased hepatic blood flow and TST O2 consumption (metabolic BW basis) during the finishing period compared with high-gain steers. Greater hepatic blood flow and energy expenditure by TST of previously restricted steers might have facilitated compensatory growth.
authors.affiliation: Department of Animal Science, Oklahoma State University, Stillwater 74078, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Hersom
authors.forename: C R
authors.initials: CR
authors.lastname: Krehbiel
authors.forename: G W
authors.initials: GW
authors.lastname: Horn
authors.forename: J G
authors.initials: JG
authors.lastname: Kirkpatrick
mesh_terms: D000136:Acid-Base Equilibrium; D000222:Adaptation, Physiological; D000821:Animal Feed; D000818:Animals; D001784:Blood Gas Analysis / Q000662:veterinary; D002417:Cattle / Q000254:growth & development* / Q000378:metabolism; D004063:Digestion; D004435:Eating / Q000502:physiology; D002523:Edible Grain; D008099:Liver / Q000378:metabolism; D008297:Male; D010101:Oxygen Consumption; D011897:Random Allocation; D012621:Seasons; D013152:Splanchnic Circulation / Q000502:physiology; D015430:Weight Gain / Q000502:physiology*