The effect of dietary ionophores on feedlot performance of lambs

Abstract

________________________________________________________________________________ AbstractThis study was conducted to evaluate the effect of different rumen fermentation modifiers (ionophores) in feedlot finisher diets on the production performance of S.A. Mutton Merino lambs. Monensin (16.4 mg/kg), lasalocid (33.0 mg/kg) or salinomycin (17.5 mg/kg) was incorporated into a commercial high-protein (398 g CP/kg DM) concentrate. Treatment diets consisted of maize meal (650 g/kg), lucerne hay (150 g/kg) and a protein concentrate (200 g/kg; containing an ionophore or not) to supply isonitrogenous (177 g CP/kg DM) total mixed diets during the experimental period. Sixty lambs (29.7 ± 2.5 kg) were randomly allocated to the treatment groups (n = 15/treatment) and each treatment was further subdivided into five replicates (n = 3/replicate). Individual body weight and average feed intake per replicate were recorded weekly and used to calculate the feed conversion ratio (FCR) and average daily gain (ADG). Ionophore treatment had no effect on any of the feedlot performance parameters measured (feed intake: 1379, 1434, 1534 and 1559 g DM/day; ADG: 298, 314, 340 and 329 g/day; FCR: 4.66, 4.58, 4.51 and 4.74 g DM intake/kg live weight gained for the Control, Monensin, Lasalocid and Salinomycin treatments, respectively. The results suggest the efficiency of the different rumen fermentation modifiers to be similar and financial implications and/or animal preference would influence their usage in sheep diets. ________________________________________________________________________________

Ionophores: Their Effects on Ruminal Fermentation, Animal Performance and Carcass Characteristics and Meat Quality

“…Carcass qualities were not affected by monensin, but the dressing percentage and boneless meat were higher in lambs fed a diet containing lasalocid (Heydari et al, 2008). Price et al (2009) reported that dietary treatment with ionophores had no effect on lamb performance. However, the shortage of literature concerning the impact of nutritional ionophore addition on animal performance and meat quality characteristics of intensively fed lambs or goats must be addressed.…”