Red clover supplementation modifies rumen fermentation and promotes feed efficiency in ram lambs

Abstract

Red clover produces isoflavones, including biochanin A, which have been shown to have microbiological effects on the rumen while also promoting growth in beef cattle. The objective was to determine if supplementation of biochanin A via red clover hay would produce similar effects on the rumen microbiota and improve growth performance of lambs. Twenty-four individually-housed Polypay ram lambs (initial age: 114 ± 1 d; initial weight: 38.1 ± 0.59 kg) were randomly assigned to one of three experimental diets (85:15 concentrate:roughage ratio; N = 8 rams/treatment): CON-control diet in which the roughage component (15.0%, w/w, of the total diet) consisted of orchardgrass hay; 7.5-RC-red clover hay substituted for half (7.5%, w/w, of the total diet) of the roughage component; and 15-RC-the entire roughage component (15.0%, w/w, of the total diet) consisted of red clover hay. Feed intake and weight gain were measured at 14-d intervals for the duration of the 56-d trial, and rumen microbiological measures were assessed on days 0, 28, and 56. Red clover supplementation impacted growth performance of ram lambs. Average daily gains (ADG) were greater in ram lambs supplemented with red clover hay (7.5-RC and 15-RC) than for those fed the CON diet (P < 0.05). Conversely, dry matter intake (DMI) was lower in 7.5-RC and 15-RC than for CON lambs (P = 0.03). Differences in ADG and DMI resulted in greater feed efficiency in ram lambs supplemented with red clover hay (both 7.5-RC and 15-RC) compared to CON (P < 0.01). Rumen microbiota were also altered by red clover supplementation. The total viable number of hyper-ammonia-producing bacteria in 7.5-RC and 15-RC decreased over the course of the experiment and were lower than CON by day 28 (P ≤ 0.04). Amylolytic bacteria were also lower in 15-RC than in CON (P = 0.03), with a trend for lower amylolytic bacteria in 7.5-RC (P = 0.08). In contrast, there was tendency for greater cellulolytic bacteria in red clover supplemented lambs than in CON (P = 0.06). Red clover supplementation also increased fiber utilization, with greater ex vivo dry matter digestibility of hay for both 7.5-RC and 15-RC compared to CON by day 28 (P < 0.03). Results of this study indicate that low levels of red clover hay can elicit production benefits in high-concentrate lamb finishing systems through alteration of the rumen microbiota.

Keywords: biochanin A; functional feeds; hyper-ammonia-producing bacteria; isoflavones; sheep.

Figure 1.

Average daily gain (ADG) in ram lambs fed three diets with varying inclusion rates of red clover. Treatments included: CON—control diet in which the roughage component (15.0%, w/w, of the total diet) consisted of orchardgrass hay; 7.5-RC –red clover hay substituted at half (7.5%, w/w, of the total diet) of the roughage component 15-RC—the entire roughage component (15.0%, w/w, of the total diet) consisted of red clover hay. The ADG was calculated as total gain ÷56 d (full duration of the finishing period). Data are presented as least squares means ± SEM. Jitter points indicate individual animal measures. There was trend for treatment differences (P = 0.06). Means lacking a common letter are different (P ≤ 0.05).

Figure 2.

Dry matter intake (DMI) in ram lambs fed three diets with varying inclusion rates of red clover. Treatments included: CON - control diet in which the roughage component (15.0%, w/w, of the total diet) consisted of orchardgrass hay; 7.5-RC - red clover hay substituted at half (7.5%, w/w, of the total diet) of the roughage component 15-RC - the entire roughage component (15.0%, w/w, of the total diet) consisted of red clover hay. The DMI was calculated as total DMI ÷ 56 d (full duration of the finishing period). Data are presented as least squares means ± SEM. Jitter points indicate individual animal measures. There was an effect of treatment for DMI (P < 0.01). Means lacking a common letter are different (P ≤ 0.05).

Figure 3.

Feed efficiency in ram lambs fed three diets with varying inclusion rates of red clover. Treatments included: CON - control diet in which the roughage component (15.0%, w/w, of the total diet) consisted of orchardgrass hay; 7.5-RC - red clover hay substituted at half (7.5%, w/w, of the total diet) of the roughage component 15-RC - the entire roughage component (15.0%, w/w, of the total diet) consisted of red clover hay. The feed efficiency was calculated as total gain ÷ total dry matter intake (full duration of the finishing period [56 d]). Data are presented as least squares means ± SEM. Jitter points indicate individual animal measures. There was an effect of treatment for feed efficiency (P < 0.01). Means lacking a common letter are different (P ≤ 0.05).

Figure 4.

Ex vivo dry matter digestibility (EVDMD) of A) hay, B) corn, and C) dried distillers’ grains with solubles (DDGS)in ram lambs fed three diets with varying inclusion rates of red clover. Treatments included: CON - control diet in which the roughage component (15.0%, w/w, of the total diet) consisted of orchardgrass hay; 7.5-RC - red clover hay substituted at half (7.5%, w/w, of the total diet) of the roughage component 15-RC - the entire roughage component (15.0%, w/w, of the total diet) consisted of red clover hay. Data are presented as least squares means ± SEM. There was a treatment by time interaction for hay and corn (P ≤ 0.04), but not for DDGS (P = 0.15). Means lacking a common letter differ between treatments within time points (P ≤ 0.05).