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 weight 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 lower 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 two years (2023 and 2024; thirty-two lambs yr^-1). Sixty-four individually-housed Polypay ram lambs (age: 97.68 ± 1.15 d; initial body weight: 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 diet1): 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 one = 0-21 d, period two = 21-42 d, total = 0-42 d). Lamb weights 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 one between treatments (P = 0.5). However, lambs fed 2.5% and 5% RC diets exhibited higher ADG when compared with lambs fed the control in period two (P = 0.03) and across the total study period (P = 0.09). The DMI was highest in lambs on the control during period one (P =0.09), with no treatment effect during period two or across the total study period (P > 0.1). Lambs fed the 2.5% and 5% RC treatments had greater FE during period one (P < 0.05), while FE was greater in 2.5% and 7.5% RC treatments during period two 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 weight gain and efficiency in ram lambs fed a high-concentrate finishing diet.