Can Cicer Milkvetch Reduce Bloating While Grazing Alfalfa?

Background

Feeding cattle leguminous forages has multiple benefits to forage and animal productivity. Legumes like birdsfoot trefoil and sainfoin are high in tannins and saponins which also have the benefit of reducing enteric methane emissions compared to cattle fed grass forages. However, legumes like alfalfa and cicer milkvetch (CMV) have minimal to no tannins. making them more palatable. Which begs the question – do they have the same ability as high tannin forages to reduce enteric methane emissions compared to cattle on grass-based forage?

Alfalfa is highly productive and widely used in stored forages. However, the concerns with grazing ruminants on fresh alfalfa pasture, which can cause bloating and death, has led producers to avoid including alfalfa in their pasture stands. Excluding the legume results in approximately $20-30 million being left on the table rather than in producers pockets every year. Multiple bloat control strategies exist, the most promising being seeding a bloat free legume alongside alfalfa, though no strategy is without its set of challenges.

Cicer milk vetch is a long-lived, bloat-free leguminous forage highly preferred by animals but yields lower than alfalfa. Mixed alfalfa/CMV may be an excellent grazing management strategy that can be adapted to reduce the risk of alfalfa bloat incidence as well as enteric methane emissions without compromising forage production. Unlike sainfoin, CMV is low in tannins and is not liked by the pest rodents that are common in light textured soils in western Canada. This is an advantage as it reduces the likelihood of gopher damage in pasture and along highways. Further, it provides producers with more options to graze alfalfa with a reduced risk of bloating. A mixed stand of CMV/alfalfa may last longer and thus reduce cost of cattle feed.

The issue with current varieties of CMV are its slow establishment and incompatibility with alfalfa. A current BCRC funded project is already looking into improving CMV seed germination and compatibility with alfalfa while this project addresses the questions surrounding grazing management and GHG emissions.

Objectives

• Characterize the forage productivity, nutritive values, and associated traits of cicer milkvetch and alfalfa in monoculture and in mixture under grazing
• Evaluate animal performance and bloat incidence from beef cattle grazing cicer milkvetch/alfalfa mixture pasture
• Evaluate the performance of new experimental grazing tolerant alfalfa population under grazing
• Assess the effect of including cicer milk vetch in a pasture mix on enteric methane emissions and soil C and N
• Cost and return comparison of treatments
• Development of new cicer milkvetch populations adapted for grazing

What they will do

A three-year grazing study will be conducted at two locations: AAFC-Lethbridge Research and Development Centre (LeRDC) in Lethbridge, AB (Brown soil zone, irrigated) and the Livestock and Forage Centre of Excellence (LFCE) and cow-calf unit in Clavet, SK (Dark Brown soil zone, rainfed) in order to expand our current understanding of the impact of seeding CMV with alfalfa.

Year one will be dedicated to establishing four forage grazing systems (treatments) at the three trial locations. Treatments include – a 100% alfalfa pasture, a 100% cicer milk vetch pasture, a 50/50 cicer milkvetch/alfalfa mixture in alternate rows and a grazing tolerant experimental alfalfa variety pasture. Paddocks will be approximately 1.5-ha at the LFCE and 0.75-ha at LeRDC.  

These paddocks will then be grazed over two years by yearlings to evaluate animal performance and by cannulated steers to monitor the incidence of bloat. During grazing GHG emissions will be measured using a GreenFeed Emission Monitoring (GEM) system. Change in soil carbon and nitrogen will also be measured at the start and end of the project. Additionally, the cost and returns associated with each treatment will be evaluated based on market value for dry matter yield and animal gain. All of these measurements will serve as indicators to potentially select grazing adapted CMV by project end.

Implications

This project was built upon the success of sainfoin/alfalfa mixed pasture for reduced bloating. Developing compatible varieties of CMV could open up more options for producers to safely graze alfalfa without the fear of bloat beyond incorporating sainfoin.