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New Mexico State University2, Las Cruces 88003
Abstract
Two trials were conducted to evaluate effects of dietary potassium (K) concentration and lasalocid (L) in lamb finishing diets. Treatments were arranged in a 2 x 2 factorial and consisted of a 65% concentrate diet with 1.1% K (C), .9% K + 21.3 mg L/kg (CL), 2.1% K (P) and 2.5% K + 20 mg L/kg (PL). In trial 1, 64 fine-wool lambs (initial wt 35.3 kg) were randomly assigned to the four treatments (two pens of four wethers and four ewes/treatment) for a 56-d feeding trial. Average daily gain was not affected by K, but was increased (P<.10) by L (.23 vs .26 kg/d). Lasalocid tended (P<.20) to improve feed:gain ratio (5.6 vs 6.3). A K x L interaction (P<.06) was noted for feed intake, with values of 1.37, 1.45, 1.49 and 1.51 kg·head–1·d–1 for the C, CL, P and PL groups, respectively. In trial 2, 16 wether lambs (four/treatment fed at 2% of body weight) were used in a site and extent of digestion and nitrogen (N) balance trial, using the same four diets as in trial 1. Site of digestion was estimated from abomasal samples taken at slaughter, with indigestible acid detergent fiber as a marker. Total tract organic matter digestibility was increased (P<.05) with added K (80.1 vs 76.4%) and L (80 vs 76.4%). Ruminal starch digestibility was not affected by added K, but was decreased (P<.10) by added L (71.8 vs 88.2%). A K x L interaction (P<.05) was observed for ruminal neutral detergent fiber (NDF) digestibility. Neutral detergent fiber digestibility in the C and CL diet was similar (48.0 vs 51.5%), while NDF digestion in the PL diet was greater (P<.10) than for the P diet (59.9 vs 37.3%). Nitrogen digestibility and N balance were similar among treatments. Ruminal ammonia concentration in samples taken at slaughter was not affected by treatments. Interactions (P<.05) of K x L occurred for molar proportions of ruminal acetate and propionate and for serum urea nitrogen (BUN). The CL diet had lower acetate and higher propionate (P<.05) than the C diet, but acetate and propionate levels were similar in the P and PL diets. The CL diet resulted in lower (P<.10) BUN than the C diet, but the PL diet resulted in higher (P<.10) BUN than the P diet. Potassium levels up to 2.5% of dietary dry matter do not have major effects on feedlot performance of lambs, but may alter digestion and fermentation patterns.
1 Journal article 1204 of the New Mexico Agr. Exp. Sta., Las Cruces.
2 Dept. of Anim. and Range Sci.
This article has been cited by other articles:
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  C.-M. J. Yang, C-T. Chang, S.-C. Huang, and T. Chang Effect of Lasalocid on Growth, Blood Gases, and Nutrient Utilization in Dairy Goats Fed a High Forage, Low Protein Diet J Dairy Sci, December 1, 2003; 86(12): 3967 - 3971. [Abstract] [Full Text] [PDF]
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