Growth and metabolic characteristics of Suffolk and Gulf Coast Native yearling ewes supplemented with chromium tripicolinate

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An experiment was conducted to investigate differences in production and physiological criteria in yearling ewe lambs from two distinct breeds fed a concentrate-base diet (13.5% CP) supplemented with 0 (BAS) or 370 ppb (CRP) chromium tripicolinate. The breeds used were Suffolk (SFK, n = 8, BW 58.9 ± 1 kg), representing a breed selected for meat production, and Gulf Coast Native sheep (GCN, n = 8, BW 44.9 ± 1 kg), representing a breed selected for adaptability and wool production. Lambs were fed the BAS diet for 10 days. On day 0 of the experimental period, the lambs were stratified by BW within breed and randomly assigned to the experimental diets. On days 0, 11 and 22, after 18 h of feed deprivation, lambs were bled via jugular venipuncture and weighed. Moreover, on day 22, lambs were catheterized and an i.v. glucose tolerance 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 change) of these measurements for days 11 and 22 compared with day 0. Growth rate, feed intake and glucose and insulin kinetics in response to an IVGTT were not affected (P > 0.10) by CRP. Relative to BAS, CRP decreased plasma NEFA concentration (P < 0.04) and percent change (P < 0.015), and insulin (P < 0.09) and thyroxine (T4; P < 0.05) percent change. When comparing breed effects, SFK exhibited higher (P < 0.0001) daily 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 T4 (P < 0.05), and lower IGF-I (P < 0.04) and urea N (P < 0.07). In response to the IVGTT, SFK exhibited faster plasma glucose and insulin clearance rates (P < 0.06) and had reduced area under the response curves (P < 0.07) compared with GCN. Diet or breed did not affect (P > 0.10) plasma glucose, albumin, triacylglycerol or cortisol concentrations. CRP reduced plasma NEFA, but did not affect glucose kinetics. There were major differences in physiological measurements between the two distinct breeds of sheep that could explain the differences observed in performance. © 1998 Elsevier Science B.V.

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Small Ruminant Research

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