GROWTH AND METABOLIC CHARACTERISTICS OF SUFFOLK AND GULF-COAST NATIVEYEARLING EWES SUPPLEMENTED WITH CHROMIUM TRIPICOLINATE

An experiment was conducted to investigate differences in production a nd physiological criteria in yearling ewe lambs from two distinct bree ds fed a concentrate-base diet (13.5% CP) supplemented with 0 (BAS) or 370 ppb (CRP) chromium tripicolinate. The breeds used were Suffolk (S FK, n = 8, BW 58.9 +/- 1 kg), representing a breed selected for meat p roduction, and Gulf Coast Native sheep (GCN, n = 8, BW 44.9 +/- 1 kg), representing a breed selected for adaptability and wool production. L ambs were fed the BAS diet for 10 days. On day O of the experimental p eriod, the lambs were stratified by BW within breed and randomly assig ned to the experimental diets. On days 0, 11 and 22, after 18 h of fee d deprivation, lambs were bled via jugular venipuncture and weighed. M oreover, on day 22, lambs were catheterized and an i.v. glucose tolera nce test (IVGTT; 500 mg glucose kg(-1) BW) was conducted. Statistical analyses of plasma metabolite and hormone measurements were conducted on their concentrations, as well as the relative changes (percent chan ge) of these measurements for days 11 and 22 compared with day 0. Grow th rate, feed intake and glucose and insulin kinetics in response to a n IVGTT were not affected (P > 0.10) by CRP. Relative to BAS, CRP decr eased plasma NEFA concentration(P < 0.04) and percent change (P < 0.01 5), and insulin (P < 0.09) and thyroxine (T-4; P < 0.05) percent chang e. When comparing breed effects, SFK exhibited higher (P < 0.0001) dai ly feed intake (2.3 vs. 1.7 kg DM d(-1)), ADG (331 vs. 95 g d(-1)) and gain-to-feed ratio (0.15 vs. 0.06). Compared with GCN, SFK had higher plasma NEFA (P < 0.01), triiodothyronine (P < 0.07) and T-4 (P < 0.05 ), and lower IGF-I (P < 0.04) and urea N (P < 0.07). In response to th e IVGTT, SFK exhibited faster plasma glucose and insulin clearance rat es (P < 0.05) and had reduced area under the response curves (P < 0.07 ) compared with GCN, Diet or breed did not affect (P > 0.10) plasma gl ucose, albumin, triacylglycerol or cortisol concentrations. CRP reduce d plasma NEFA, but did not affect glucose kinetics. There were major d ifferences in physiological measurements between the two distinct bree ds of sheep that could explain the differences observed in performance . (C) 1998 Elsevier Science B.V.