A meta-analysis of lasalocid effects on rumen measures, beef and dairy performance, and carcass traits in cattle

Abstract Text:

The objective of this study was to evaluate the effects of feeding lasalocid on rumen measures, beef and dairy performance, and carcass traits in cattle, using meta-analytic methods. Meta-regression was used to investigate sources of heterogeneity. Rumen measures were assessed using 10 studies (20 comparisons). Lasalocid increased total VFA and ammonia concentrations by 6.46 and 1.44 mM, respectively. Lasalocid increased propionate and decreased acetate and butyrate molar percentage (M%) by 4.62, 3.18, and 0.83%, respectively. Valerate M% and pH were not affected. Meta-regression found butyrate M% increased linearly with duration of lasalocid feeding (DUR; P = 0.017). When >200 mg/d was fed, propionate and valerate M% were higher and acetate M% was lower (P = 0.042, 0.017, and 0.005, respectively). Beef performance was assessed using 31 studies (67 comparisons). Lasalocid increased ADG by 40 g/d, improved feed-to-gain (F:G) by 410 g/kg, and improved feed efficiency (FE; combined measure of G:F and the inverse of F:G). Lasalocid did not affect DMI, but heterogeneity in DMI was influenced by DUR (P = 0.004) and linear effect of entry BW (P = 0.011). Heterogeneity of ADG was influenced by the linear effect of entry BW (P = 0.028) but not DUR. Combining entry BW ≤275 vs. >275 kg and DUR showed cattle entering at >275 kg fed ≤100 d had the highest ADG. The FE (P = 0.025) and F:G (P = 0.015) improved linearly with dose, and entry BW >275 kg improved F:G (P = 0.038). Fourteen studies (25 comparisons) were used to assess carcass traits. Lasalocid increased HCW by 4.73 kg, but not dressing percentage, mean fat cover, or marbling score. Heterogeneity of carcass traits was low and not affected by DUR or dose. Seven studies (11 comparisons) were used to assess dairy performance but the study power was relatively low. Lasalocid decreased DMI in TMR-fed cows by 0.89 kg/d, but had no effect on milk yield, milk components, or component yields. Dose linearly decreased DMI (P = 0.049). The DUR did not affect heterogeneity of dairy measures. This work showed lasalocid improved ADG, HCW, FE, and F:G for beef production. These findings may reflect improved energy efficiency from increased propionate and decreased acetate and butyrate M%. Large dairy studies are required for further evaluation of effects of lasalocid on dairy performance.

Keywords: feedlot, ionophore, meta-regression