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 -1): 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 day 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.

Fructan Catabolism by Rumen Microbiota of Cattle and Sheep

“…Fermentation of the orchardgrass substrate in the current study produced metabolic products including lactate, acetate, propionate, and butyrate that were similar in concentration to previously reported values for ex vivo fermentation of tall fescue by bovine and ovine rumen bacteria [24]. In contrast to these prior studies, in which purified fructans were utilized as the fermentative substrate, the orchardgrass used in the current study was a complex substrate that provided other non-structural and structural carbohydrates as well as proteins that would have been subject to degradation by the rumen microbiota.…”

“…Sheep are commonly used as model ruminants in health, nutrition, and rumen fermentation research due to advantages related to overall animal size as well as length of production cycles. However, previous research has suggested that the rumen microbial communities of sheep and cattle may differ both in composition and function, including differences in the fermentation of non-structural carbohydrates [24,38,39]. Both sheep and cattle may be managed on high-forage diets including in pasture-based systems.…”

“…Lactate, succinate, acetate, propionate, butyrate, valerate, and isovalerate and/or methylbutyrate (IVMB) were quantified using HPLC (Summit HPLC; Dionex, Sunnyvale, CA, USA). Specifications of the HPLC system and analyses were as previously described by Weinert-Nelson et al [24].…”

“…Degradation of fructans by ruminal bacteria of cattle [18,22] and sheep [17,23] has been evaluated separately, but few comparisons have been conducted to evaluate potential differences between these species. Weinert-Nelson et al [24] did find lactate accumulation to be 40 to 70% greater when cool-season grass hay was incubated with bovine versus ovine rumen bacteria. Although neither fructanolytic bacteria and fructan fermentation were evaluated in that study, this difference was attributed to potential fermentation of fructans and other non-structural carbohydrates in the hay substrate given the minimal starch concentrations present in cool-season grasses [15,16,24].…”

“…Weinert-Nelson et al [24] did find lactate accumulation to be 40 to 70% greater when cool-season grass hay was incubated with bovine versus ovine rumen bacteria. Although neither fructanolytic bacteria and fructan fermentation were evaluated in that study, this difference was attributed to potential fermentation of fructans and other non-structural carbohydrates in the hay substrate given the minimal starch concentrations present in cool-season grasses [15,16,24]. To the authors' knowledge, only one previous study has been conducted in which ruminal fructan fermentation has been directly compared between cattle and sheep, finding differences in the rate of fructan utilization [25].…”