The effects of diet on blood flow to the regions of the reticulo-rumen in growing lambs

Abstract

Proc. Aust. Soc. Anim. Prod. 1996 Vol. 21 THE EFFECTS OF DIET ON BLOOD FLOW TO THE REGIONS OF THE RETICULORUMEN IN GROWING LAMBS G.J. McCRABBB, B.J. HOSKINGC, E.N. PONNAMPALAMA, R. HARDINGD and A.R. EGAN * Dept of Agriculture, Faculty of Agriculture and Forestry, University of Melbourne, Vic. 3052 * CSIRO Division of Tropical Animal Production, Tropical Beef Centre, Rockhampton, Qld 4702 'Better Blend Stockfeeds, 9 Queens St, Oakey, Qld 4401 D Dept of Physiology, Monash University, Clayton, Vic. 3 168 A Capillary blood flow to the rumen of sheep is one factor involved in the uptake of nutrients from this region of the gut, and is increased after feeding (Barnes et al. 1983). The objective of this experiment was to describe the effects of both diet, and of time after feeding, on blood flow to the different regions of the reticulo-rumen (RR). Aseptic surgery was conducted on seven, 12 month-old female crossbred lambs. Lambs were anaesthetised (Pentobarbitone sodium) and polyvinylchloride catheters inserted into the left ventricle of the heart via a carotid artery, and into the descending aorta via a femoral artery. No measurements were made for at least 2 days after surgery. Sheep were fed daily at 0900 hours with ad libitum oaten chaff (C, n=3) or ad Zibitum oaten chaff plus 300 g lupin grain (S, n=4). Blood flows to the RR were measured with 15~ diameter coloured microspheres (E-Z- Trac, USA) immediately prior to feeding (0900 hours), and 1.5 hours (1030 hours), 3.0 hours (1200 hours), 4.5 hours (1350 hours) and 6.0 hours (1500 hours) after feeding. At each measurement time, approximately 8 million microspheres of a different colour were injected into the left ventricle while a reference sample was withdrawn (6 n&/minute) from the descending aorta. On the day after the experiment was completed, lambs were euthanased (Pentobarbitone sodium) and the RR dissected into its components (cranial sac, dorsal sac, ventral sac, reticulum) and weighed. To estimate blood flow, the numbers of microspheres of each colour were estimated in both reference blood samples and RR tissue following digestion in 2 M NaOH, as described by Burrell et al. (1993): Liveweight (3l.Ok4.9 vs. 27.0~2.4 kg), full-RR weight (4.2kO.4 vs. 4.6-to.3 kg) and oaten chaff intake (529253 vs. 484~242 g/day) of C lambs were not significantly different from S lambs. Blood flow (rnIYminute.100 g) to the reticulum of C lambs (65&7) was not significantly different from S lambs (76+8), and did not significantly change with time after feeding. The blood flow to the cranial sac of S lambs was higher (P~0.05) than for C lambs, whereas there was no significant difference between C and S lambs in values of blood flow to the dorsal sac and ventral sac. Blood flow increased (PcO.05) to all regions of the rumen after feeding for S lambs, but not significantly for C lambs (Table 1). Table 1. Blood flow (nWminuts.100 g) to regions of the reticula-rumen in lambs fed oaten chaff (C) or oaten chaff with 300 g lupin seed (S), before and after feeding BARNES, R.J., COMLINE, R.S. and DOBSON, A. (1983). Quart. J. Exp. Physiol. 68: 77-88. BURRBLL, J.H., LUMBERS, E.R., CRAWFORD, E.N. and STEVENS, A.D. (1993). Proc. Amt. Physiol. Pharmacol. Sot. 24: 85P. 351