Red clover improves the energy to protein balance of lucerne-grass herbage
Citation
Godin, X., Tremblay, G. F., Seguin, P., Bittman, S., Hunt, D., Hakl, J., Bélanger, G., Thivierge, M. N., Bertrand, A., Thériault, M., & Claessens, A. (2021) Red clover improves the energy to protein balance of lucerne-grass herbage. Joint XXIV International Grassland Congress and XI International Rangeland Congress, Nairobi, 2021/10/23 - 2021/10/29. [Poster]
Plain language summary
The balance between nitrogen (protein) and energy (carbohydrate) in dairy cow rations allows more efficient use of nitrogen by rumen microorganisms, and thus lessen N losses into the environment. In alfalfa, a major component of rations, this balance is not optimal due to its high protein content, particularly in the form of non-protein nitrogen and rapidly degradable proteins in the rumen. Red clover is richer in soluble sugars and contains polyphenol oxidase which reduces the degradability of its protein compared to alfalfa. The objective of this study was to evaluate the benefits of adding red clover to alfalfa-based mixtures to improve energy-protein balance. Forage plots have been established at several sites in Canada. The treatments consisted of different proportions of alfalfa: red clover, with or without grasses. Our results confirmed that the addition of red clover to alfalfa mixtures increases the energy content of the forages and reduces protein degradability. Adding red clover is therefore an effective way to improve the energy-protein balance of alfalfa-based mixtures. Further work is required to determine whether this improvement could translate into improved nitrogen use efficiency in ruminants.
Abstract
Low ratio of readily fermentable carbohydrate to soluble protein concentrations in lucerne (Medicago sativa L.) leads to inefficient use of herbage N by ruminants. To improve the energy to protein balance in lucerne-grass herbage, four proportions of lucerne:red clover (Trifolium pratense L.) were compared in mixtures with and without grasses: timothy (Phleum pratense L.) and tall fescue (Schedonorus arundinaceus Schreb. Dumort.) in Quebec (QC, Canada). In the first post-seeding year, red clover proportion averaged (across grasses and four harvests) 0, 37, 59, and 74% in herbage mixtures. Increasing the proportion of red clover caused a slight but significant decrease in herbage total nitrogen (TN) concentration (32 to 31 g kg-1 DM) but substantial decreases in non-protein N (PA), rapidly (PB1) and moderately (PB2) degraded protein fractions, and a significant increase in the slowly degraded protein fractions (PB3+PC) (157 to 308 g kg-1 TN). With the inclusion of 74% of red clover, the ratio of soluble sugar to crude protein (CP) in herbage increased from 0.25 to 0.36 because of the increase in the soluble sugar concentration (48 to 66 g kg-1 DM). The inclusion of red clover in mixture with lucerne improved the energy to CP balance compared to lucerne alone, and caused a linear increase in the herbage in vitro neutral detergent fiber digestibility from 568 to 639 g kg-1 aNDF with similar herbage dry matter yield (10.3 Mg ha-1).