Effect of laidlomycin propionate on site and extent of digestion in feedlot cattle. (199)

M.E. Weston, J.E. Correa, T.E. Wright


Four beef steers (300 kg) fitted with ruminal and duodenal cannulas were randomly allotted in a 4 x 4 Latin Square to determine the effects of different levels of the ionophore laidlomycin propionate (LP) on characteristics of digestion of an 82% concentrate diet. Treatments consisted of LP provided in the diet at 0, 6, 9, and 12 mg kg-1 dry matter (DM). The diet [95.3% organic matter (OM), 31.4% starch, 12.3% crude protein (CP), and 11.1% acid detergent fibre (ADF) on a DM basis] was fed at 2% of body weight (BW) in two equal meals daily (0800 and 2000 h). Chromic oxide (Cr2O3) was mixed in the diet daily (15 g) and duodenal and faecal concentrations utilised in flow and excretion calculations. Laidlomycin propionate demonstrated no response on apparent ruminal OM digestion (63.3 vs 64.3, 63.8, and 62.8%; P > 0.10), or apparent ruminal ADF digestion (33.1 vs 33.4, 31.7, and 34.9%; P > 0.10), for 0, 6, 9, and 12 mg kg-1 LP, respectively. However, apparent intestinal ADF digestion was maximized (18.2 vs 34.3%; P < 0.10) with LP at 9 mg kg-1. Passage of non-ammonia nitrogen to the duodenum (74.0 vs 72.1, 71.8, and 73.2 g day-1; P > 0.10) was unaffected by the treatment. Apparent total tract nitrogen digestion values were 63.3, 67.4, 71.4, and 68.6% for 0, 6, 9, and 12 mg kg-1 of LP, respectively, although these values were not different (P > 0.05). In conclusion, administration of LP had no effects on ruminal, duodenal flow, and total tract digestion of DM, OM, and starch.


Beef cattle; Laidlomycin propionate; Digestion

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