The energy to protein balance is improved by red clover addition in alfalfa-based forage mixtures
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) The Energy to Protein Balance Is Improved By Red Clover Addition in Alfalfa-Based Forage Mixtures [Abstract]. ASA, CSSA, SSSA International Annual Meeting, Salt Lake City, UT. https://scisoc.confex.com/scisoc/2021am/meetingapp.cgi/Paper/136568
Plain language summary
A better balance between nitrogen (protein) and energy (carbohydrates) in dairy cow rations allows more an efficient use of nitrogen by rumen microorganisms, and thus lessens 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 forage 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 energy to protein balance in alfalfa (Medicago sativa L.) leads to inefficient use of forage N by ruminants. Because of its high concentration of soluble sugars and low protein degradability, the addition of red clover (Trifolium pratense L.) could improve the soluble sugar to crude protein ratio in alfalfa-based forage mixtures. Four proportions of alfalfa:red clover (100:0, 75:25, 50:50, 25:75) were sown in mixtures with either no grass, timothy (Phleum pratense L.), or tall fescue (Schedonorus arundinceus Schreb. Dumort.) at two locations (Saint-Augustin-de-Desmaures, QC; Agassiz, BC) in Canada. During the first post-seeding year, nutritive attributes of all forage samples were predicted by visible near-infrared reflectance spectroscopy, the soluble sugar to crude protein ratio was calculated, and the nutritive attributes were then weighted for yield observed at each of the four harvests as a proportion of the seasonal yield. Coefficients of determination (r2) were established between the observed proportion of red clover in the forage plots and the nutritive attribute in each alfalfa-grass forage sample. Soluble sugar concentration increased with the red clover proportion (r2 > .74) in all forage mixtures at both sites. Substantial decreases in proportion of non-protein nitrogen (r2 > .45) and rapidly degraded protein fractions (r2 > .73), along with an increase in the slowly degraded protein fractions (r2 > .81) were also observed with the increasing proportions of red clover in forage mixtures at both sites. The forage crude protein concentration decreased as the red clover proportion increased at Agassiz (r2 = .55), but the ratio of soluble sugars to crude proteins augmented with the proportion of red clover (r2 > .63) in the forage mixtures at both sites. The inclusion of red clover improved the energy to protein balance in alfalfa-based forage mixtures with or without grass harvested at two sites in Canada.