Effects of salinomycin on ruminal characteristics and performance of grazing beef steers.
Grazing trials were conducted for 2 yr using weanling Brahman crossbred beef steers to evaluate graded levels of salinomycin (0, 50, 100 or 150 mg. head-1.d-1) for 161 d and to evaluate salinomycin in a free-choice mineral supplement (99 d). The 40 and 48 steers in trials 1 and 2 had average initial weights of 198 and 285 kg, respectively. In trial 1, steers were group-fed to consume either 0, 50, 100 or 150 mg of salinomycin.head-1.d-1 in .9 kg ground corn while grazing bermudagrass pastures. Both linear (P less than .01) and quadratic (P less than .05) effects were observed for steer performance as salinomycin level increased from 0 to 150 mg.head-1.d-1. Linear increases (P less than .01) in ruminal NH3-N (mg/100 ml) and in the molar proportion of propionate and decreases (P less than .01) in butyrate and acetate/propionate were detected. In trial 2, mineral supplements with and without salinomycin were fed free-choice to steers on bermudagrass pasture. The mean salinomycin intake of 38 mg.head-1.d-1 was lower than anticipated as a result of the instability of salinomycin in the mineral supplement and the slightly lower intake (65 g/d) than anticipated (75 g/d). Performance of steers was not influenced by salinomycin supplementation in trial 2. The ionophore salinomycin at intakes over 50 mg.head-1.d-1 appears to increase the performance of steers grazing bermudagrass pasture.
Bagley
C P
CP
Louisiana State University Agricultural Center, Baton Rouge 70893.
Feazel
J I
JI
Morrison
D G
DG
Lucas
D M
DM
D000821:Animal Feed; D000818:Animals; D001835:Body Weight / Q000187:drug effects*; D002417:Cattle / Q000254:growth & development*; D005503:Food Additives; D007476:Ionophores / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D011714:Pyrans / Q000008:administration & dosage / Q000494:pharmacology; D012417:Rumen / Q000187:drug effects*; D000095662:Polyether Polyketides
D005503:Food Additives; D007476:Ionophores; D011714:Pyrans; C010327:salinomycin; D000095662:Polyether Polyketides