Re-Thinking Red Clover: Supplementing Red Clover Hay Promotes Weight Gain and Feed Efficiency in Ram Lambs
Jennifer Weinert-Nelson, Ph.D., United States Department of Agriculture, Agricultural Research Service, Forage-Animal Production Research Unit, Lexington, KY
Donald G. Ely, Ph.D., University of Kentucky, Department of Animal and Food Sciences, Lexington, KY
Brittany Harlow, Ph.D., United States Department of Agriculture, Agricultural Research Service, Forage-Animal Production Research Unit, Lexington, KY
Legumes such as alfalfa and red clover (RC) have been traditionally utilized as forage feedstuffs in small ruminant diets to meet animal needs for fiber, protein, and micronutrients (vitamins and minerals). In addition to serving as a source of these required nutrients, legumes also contain phytochemicals including polyphenolic isoflavones. One of the isoflavones produced by legumes, biochanin A, has well-documented impacts on rumen fermentation and health of ruminant animals. For example, biochanin A has been shown to alleviate heat stress and symptoms of fescue toxicosis in both cattle and goats. Biochanin A also inhibits protein-wasting bacteria and enhances fiber utilization in the rumen, and more efficient use of dietary protein and fiber promotes weight gain in beef cattle supplemented with biochanin A.
Isoflavone profiles and concentrations differ amongst legume species, with greater concentrations of biochanin A in RC than alfalfa or white clover. Supplementing cattle with RC hay as a source of biochanin A produces similar growth performance benefits compared with a purified supplement. Additionally, the growth-promoting effects of RC hay can be achieved at relatively low levels of supplementation, with improvements in ADG in cattle fed RC hay at as little as 15% of the total diet.
Feed efficiency is a major factor impacting profitability of ruminant production systems, with feed costs representing a substantial proportion of total production costs. Identifying nutritional and feeding management practices that promote feed efficiency by increasing gain and/or decreasing feed intake are essential for economic sustainability. Initial research on the benefits of biochanin A and red clover supplementation for growth performance were conducted in cattle. Therefore, a recent study conducted at the University of Kentucky Sheep Unit by sheep nutritionist Dr. Don Ely (UK, Animal and Food Sciences Department) in collaboration with the USDA-Agricultural Research Service Forage-Animal Production Research Unit (FAPRU; https://www.ars.usda.gov/midwest-area/lexington-ky/fapru/) aimed to determine whether this nutritional strategy would offer similar benefits for small ruminant production systems.
Twenty-four Polypay ram lambs (initial age: 114 days; initial weight: 84 lb) were fed one of three high-concentrate finishing diets in which RC hay was included at three levels: 1.) 15.0% orchardgrass hay, 0.0% RC hay (15.0-OG), 2.) 7.5% OG hay, 7.5% RC hay (7.5-OG-RC), or 3.) 0.0% OG hay, 15.0% RC hay (15.0-RC). All diets were formulated at an 85:15 concentrate:roughage ratio, ground into a total mixed ration, and provided to lambs ad libitum. The concentrate component (85% of the total diet) included corn and corn-based dried distillers’ grains with solubles (DDGS) for all diets. Diets were formulated to meet nutritional requirements for growth, with crude protein balanced across the three diets by adjusting the proportion of corn and DDGS in the concentrate component. Diet composition is shown in Table 1.
Ram lamb growth performance was monitored over a 56-day finishing period to determine total gain (TG), average daily gain (ADG), total feed intake (TFI), daily feed intake (DFI), and the feed conversion ratio (FCR), Rumen fluid was also collected to evaluate impacts of red clover supplementation on the rumen microbiota and fermentation.
Results and Discussion
Incorporation of relatively small amounts of RC hay into high-concentrate finishing diets resulted in marked improvements in ram lamb performance. Growth and rumen microbiological effects of red clover were consistent regardless of supplementation level (7.5% or 15.0%). The impact of RC hay supplementation on lamb growth, feed intake, and feed efficiency over the 56-day finishing period is shown Table 2. Regardless of supplementation level, inclusion of RC hay tended to improve weight gain, while also lowering feed intake. Lambs fed the 7.5-OG-RC and 15.0-RC diet gained 0.91 lb per day, respectively, whereas lambs receiving the 15.0-OG diet gained 0.79 lb per day. Conversely, lambs fed the 15.0-OG diet consumed 4.34 lb feed per day, but lambs supplemented with RC hay consumed 3.90 lb (7.5-OG-RC) to 3.96 lb (15.0-RC) per day. This concurrent increase in weight gain and reduction in feed intake led to lower FCR and greater feed efficiency in ram lambs supplemented with RC hay. Ram lambs fed diets including RC hay required 25% less feed to produce each pound of gain.
Effects of red clover supplementation on ram lamb growth performance were most apparent in the latter half of the finishing period. Figure 1a-c shows ADG, DFI, and FCR in the first half of the finishing period (day 0 – 28) compared to day 28 – 56. There was a tendency for greater ADG in ram lambs supplemented with RC hay regardless of the time period in the trial. Differences in feed intake, however, were more pronounced during the second half of the finishing period. Daily feed intake did not differ between diets at day 28, but by day 56, DFI had increased by almost 40% in lambs fed the 15.0-OG diet. Similar increases in feed intake were not observed for lambs supplemented with RC hay. In lambs fed the 15.0-OG diet, DFI increased between day 28 and day 56. Differences in feed intake during the second half of the trial resulted in greater feed efficiency in RC-supplemented lambs than 15-OG from day 28 – 56. Ram lambs fed RC diets were 47% more efficient, requiring over 2 lb less feed to produce a pound of gain than lambs fed 15.0-OG in the latter half of the finishing period. This large improvement in feed efficiency would provide economic benefits to producers by substantially lowering the amount (and thus the cost) of feed necessary to grow lambs to market weight.
Improvements in growth performance were linked to changes in the rumen of ram lambs. Red clover supplementation led to a 10 – 100 fold reduction in hyper-ammonia-producing bacteria (HAB; Figure 2).
The role of HAB in the rumen and impacts of RC supplementation are described in Figure 3. Hyper-ammonia-producing bacteria in the rumen degrade peptides and amino acids (the building blocks of protein) and produce large quantities of ammonia. Only a small portion of this ammonia can be used by the rumen bacteria and incorporated into microbial protein, and the majority of ammonia is excreted by the animal. Ammonia losses are an inefficient use of dietary protein. Suppressing HAB results in more by-pass protein reaching the abomasum and small intestine, where it can be broken down, absorbed by the animal, and utilized for growth.
Red clover hay supplementation also increased in vitro digestibility of hay and corn (Table 3). In particular, the more efficient utilization of corn in the high-concentrate diets fed to lambs in this study likely contributed to improvements in growth performance of ram lambs supplemented with RC hay.
Given that the initial weight of lambs in this study was almost 85 lb, a reduction in feed efficiency over the course of the study was expected and was observed in lambs fed the 15.0-OG diet. In comparison, RC supplementation allowed lambs to maintain efficiency at higher body weights. More research is needed to determine impacts of red clover supplementation at lower body weights earlier in the finishing period and the potential to improve growth performance in breeds with characteristically lower feed efficiency. Additionally, prior studies of biochanin A and red clover supplementation have shown growth benefits in grazing cattle consuming forage-based diets. Future studies are required to evaluate the effects of red clover in forage-based sheep production systems, such as in lambs maintained on pasture during the finishing period. Regardless, results of this most recent UK – FAPRU study demonstrated that supplementing low levels of RC hay can be an effective nutritional strategy for improving lamb growth performance.
Red clover is rich in the bioactive isoflavone biochanin A. A recent UK – FAPRU study evaluated the impacts of biochanin A supplementation via RC hay on growth performance of ram lambs as well as the rumen microbiota and fermentation. Low levels of red clover hay inclusion (7.5% and 15.0% of the total diet) in high-concentrate finishing diets improved feed efficiency of ram lambs, promoting weight gain while decreasing feed intake. Red clover hay supplementation suppressed rumen protein-wasting peptide- and amino-acid degrading bacteria and improved digestibility of hay and corn in the rumen. Growth and microbiological effects of RC were consistent regardless of supplementation level in the diet. Results of this study indicate that low levels of RC hay can produce production benefits in ram lamb finishing systems.