PSI-20 Red clover as a functional feed: Effects on feed efficiency of finishing ram lambs

Abstract Red clover (RC) contains a secondary metabolite called biochanin A that has previously been demonstrated to increase body weight (BW) gain and feed efficiency (FE) while depressing dry matter intake (DMI) in ram lambs when incorporated at levels as low as 7.5% of a total high concentrate finishing diet. The objective of the study was to determine if decreased levels of RC hay supplementation would produce similar effects. It was hypothesized that RC supplementation at levels below 7.5% of the total diet would improve FE by decreasing DMI while subsequently increasing average daily gain (ADG). The study was repeated over 2 yr (2023 and 2024; n = 32 lambs yr-1). Individually-housed Polypay ram lambs (n = 64; age = 97.68 ± 1.15 d; initial BW = 32.21 ± 0.89 kg) were utilized in a randomized complete block design and fed one of four isocaloric and isonitrogenous diets (85:15 concentrate:roughage ratio; n = 16 rams per diet): a control diet in which the roughage component (15.0% wt/wt of total diet) consisted of orchardgrass hay, 2.5%-RC (roughage: 2.5% RC; 12.5% orchardgrass wt/wt), 5.0%-RC (roughage: 5.0% RC; 10% orchardgrass wt/wt), and 7.5%-RC (roughage: 7.5% RC; 7.5% orchardgrass wt/wt). Study years were subdivided into periods for performance comparisons (period 1 = 0-21 d, period 2 = 21-42 d, total = 0-42 d). Lamb BW and feed intake were measured weekly. Data were analyzed using PROC MIXED with repeated measures in SAS (v.9.4, SAS inst. Inc., Cary, NC). There were no differences in ADG across period 1 between treatments (P = 0.5). However, lambs fed 2.5% and 5% RC diets exhibited greater ADG when compared with lambs fed the control in period 2 (P = 0.03) and across the total study period (P = 0.09). The DMI was greatest in lambs on the control during period one (P =0.09), with no treatment effect during period 2 or across the total study period (P > 0.1). Lambs fed the 2.5% and 5% RC treatments had greater FE during period 1 (P < 0.05), while FE was greater in 2.5% and 7.5% RC treatments during period 2 compared with lambs on control (P < 0.05). Although FE was numerically greater in all RC treatments versus the control across the full study period, this difference was not significant (P = 0.19). These results suggest that supplementing red clover at levels below 7.5% can promote BW gain and FE in ram lambs fed a high-concentrate finishing diet.