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The forage challenge – higher yield and higher quality

One goal is to break the inverse link between yield and digestibility

Forage production is a vital component of Canadian agriculture, since it covers nearly half of our cultivated land. Moreover, forages make up around 60 per cent of dairy rations and 80 per cent for beef cattle.

Innovations in forage production will be essential for these sectors. The challenges and opportunities will mainly hinge on four major issues: economic and environmental sustainability, social acceptability of farming activities, climate change and world population growth.

What are the “forage solutions” to these issues?

They will have to involve the improvement of both yield and nutritive value, which represent the two mainstays of successful forage production. A consistent higher yield will improve profitability and competitiveness of dairy and beef farms, while reinforcing our capacity to feed a growing world population. At the same time, forages that are more digestible and show higher sugar content will allow us to increase their share in the ration. They also allow us to decrease our use of grain, stabilizing production costs, reducing nitrogen release to the environment and making those same grains available for human consumption.

Potential versus actual yield

A recent study showed that U.S. alfalfa yield increased by 0.25 per cent per year, compared to 1.4 per cent per year for silage corn.

A recent study showed that U.S. alfalfa yield increased by 0.25 per cent per year, compared to 1.4 per cent per year for silage corn.
photo: Tessa Nybo

Yield of perennial forage crops has not increased as fast as for many annual crops like corn and wheat. A recent study showed that U.S. alfalfa yield increased by 0.25 per cent per year, compared to 1.4 per cent per year for silage corn. The authors attribute this low yield increase to the complexity and large number of forage species, to the fact that all their above-ground biomass is harvested and to a lack of investment in breeding.

Potential yield at any location depends on conditions like solar radiation, temperature, CO2 concentration in the atmosphere as well as on the characteristics of the species. However, this yield potential is rarely achieved due to stress — cold, drought, pests, poor drainage and other reasons. Hence, we sometimes observe a big difference between the potential yield and what is actually achieved. This difference could further increase if we intensify our use of marginal land for growing forages. Improving the yield potential of our forage crops is perhaps possible, but will require major and well-targeted research. Avenues for research include improving photosynthetic efficiency, or modifying biomass distribution between above- and below-ground parts of the plant.

In the short and medium terms, reducing the difference between potential and actual yield seems a more promising approach. Very little research has been carried out to quantify this difference. A recent U.S. study suggests that the average yield of alfalfa in the field is only around 30 per cent of its potential yield. In order to decrease this difference, one must better understand the effects of different stresses on our forage species, so that we can develop cultivars and agronomic practices that will enable them to better tolerate these stresses.

Cold tolerance and digestibility

Our winter conditions are a good example of stress conditions that can cause significant yield losses of perennial forage crops, particularly in winter-sensitive species like alfalfa. Since the introduction of alfalfa in Quebec, breeder selection and sound agronomic practices have improved winter survival. One only has to think about the “Apica” alfalfa cultivar or the recommendations on harvest management in the fall. However, these improvements are not sufficient to eliminate the risk of winter damage.

Other recent studies show more promise. Using a new selection approach, Canadian breeders have shown it is possible to improve cold tolerance of alfalfa and red clover by more than 5 C. These innovations are especially valuable in the context of climate change in which we foresee an increasing risk of winter damage for alfalfa.

Is it possible to improve the nutritive value without decreasing the yield?

Digestibility of forages is one of the crucial aspects of their nutritive value. Improving digestibility is possible but is often associated with a decrease in yield or persistence. For example, shortening the interval between cuts, and harvesting at a younger stage allow improving the digestibility of forages, although at the expense of the yield. Also, alfalfa cultivars expressing better digestibility have been developed in recent years but, in most cases, these have showed lower yields or a lower persistence.

Therefore, the challenge is to increase digestibility of forages while maintaining or even increasing their yield. It is quite a task, since it requires dissociating yield and digestibility. Our research studies on timothy have shown this to be feasible if we decrease the ratio between lignin and cellulose. Similar results on alfalfa have recently been obtained by an American research team. Thus, there is hope.

Producing more forages of higher quality is vital to Canadian farmers and to our planet. However, to achieve this goal, sustained multidisciplinary research efforts are necessary.

This article appears in the 2015 Forage & Grassland Guide

Gilles Bélanger is a researcher for Agriculture and Agri-Food Canada, and recipient of the 2013 Canadian Forage and Grassland CFGA Leadership Award. This article is based on his presentation to the CFGA annual meeting in October 2014.

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