Feeding animals high rates of forage is an opportunity that many farms should consider. Those diets aim to take advantage of the cow’s biological ability to convert ingested fibre into high value products such as milk or meat. Both the quality and quantity of supplied forage are closely related to milk production, production costs and farms profits. In some herds, the process required to implement the model may take years because of the changes to be carried out in the productive structure of the farm. This approach may not apply to all farms, but the concept should be taken into account and considered by producers and technicians working as consultants for farmers.
In just two years we will implement a change from a quota system (we are the so called quota generation), with a significant part of income coming in the form of direct payments, to a model with no quota and with support coming from so called greening (maintenance of permanent grasslands, crop rotation, etc. and linked to the use of the territorial background).
Milk production in the EU changed during the period from 2006 to 2010. Those areas with a dairy tradition (Germany, French Brittany, the Netherlands, Ireland, Denmark…) continued growing at a rate of 2% yearly. Galicia emerged as one of the regions with the highest growth rate in recent years. Conversely, in Southern Europe, production declined. Such diverging trends have to do with both the future perspectives of farms as well as with the regional strategic policies that have been implemented. And a good example of this is Ireland, where after the abolishment of quotas, their goal is increasing their production to 50% until 2020, following their production model, which is predominantly pasture based.
Experts agree that the Atlantic coastal regions in Europe have the ability to increase their production by 5% annually from 2015. The key factors for this growth have to do with farm structure, their territorial organization and, above all, with the availability of forage production areas. All of these growth hypotheses are closely related to the evolution of milk prices.
In parallel, we are also witnessing a high volatility of raw materials for the food industry that has to do with competition for grain and protein concentrate sources, and the food requirements of an ever-growing world population. This has a strong effect on production costs, especially in those farms that are highly dependent on concentrates.
This is the reason why one of the keys to competitiveness in farms devoted to cattle is a higher dependence on fibres (forage) produced at the farm itself. In fact, this is the trend that has been emerging in recent years around the world, even in the United States. Larry Chase, from Cornell University, points out the fact that American Northeastern and Midwestern areas, that is, those that produce high yield good quality forage, are becoming more and more important within the US milk industry because of their competitive advantage. According to this researcher, the reasons why forage is becoming a more frequent ingredient of American diets is the improvement of silage work, the better knowledge and implementation of forage digestibility (dFND) and the increase of dFND in corn silage.
But how much forage can we include in our diets? We could, of course, work with no supplements. But experience teaches us that such rations do not maximize productivity nor efficiency or profitability. The trouble is that milk production implies high energy requirements, and filling the rumen with high fibre content limits the cow’s ability to reach their genetic potential for milk production.
Mertens described the way cows control their intake. For highly productive rations (low fibre content) cows adjust their intake in order to meet their energy requirements on the basis of their milk production genetic potential. For low productivity rations (high fibre content), cows eat their diet till they reach the filling limit and milk production is limited to the energy intake. In other words, the forage intake in high productivity cows is limited by the volume of fibre reaching the rumen. This is the reason why rations containing 100% forage do not yield high production rates.
The amount of forage that may be included in a ration can be estimated on the basis of its contents of Neutral Detergent Fibre (NDF) and digestibility (dNDF). Mertens (1988, 1997 and 2010) related total NDF intake to the cow’s liveweight. According to this author, intake should range between 1.1 and 1.2% of the cow’s liveweight, 75% of the total NDF coming from forage. However, some trials show that forage intake may go beyond 1.3% liveweight. This researcher took this even further and recently developed the NDF Intake System. This is an NDF based predictive model of intake that describes the mechanisms of its regulation in order to find out the top forage inclusion rate for diets, taking their quality into account as well as the herds productive potential.
All this research effort is a sign of the significance that forage acquired in recent times. Take as an illustration the pyramid shape graph that goes with the text and shows the relative importance of forage: in 1995, Lundquist thought that its role is that of effective fibre contribution, and 20 years later, Paulson states that it plays a predominant role.
Traditionally, in order to decide upon the inclusion of forage in diets we used to work on the basis of the forage/concentrate ratio. This ratio ranges between 40:60 and 60:40. But, would it be possible to achieve high production rates with diets where forage accounts for a higher percentage? And if so, what would the requirements be in order to implement such approaches in our farms?
The reserarchers’ answer is positive but… under specific terms. Both theoretically and in commercial herds, it is possible to find farms that are working with 75% forage rates (with an intake that is 1.3-1.4% cow’s liveweight) with high levels of milk production.
First of all, it is essential that both the farmer and the nutritionist understand the concept and be convinced that it is possible to implement it in their herd. Otherwise, they are doomed to fail. Once the strategic decision is made, tactical matters will have to be developed at three levels:
Working with more forage and less concentrate will imply using 15-30% more forage under normal circumstances. In order to achieve this goal we will have to set up forage options, fertilization plans and the relevant agenda to make the most out of what we have. Producing more forage will entail having a larger storage capacity. The proper structures should be made available in order to store a larger volume of preserved forage and keep its nutritional quality.
We must emphasize our commitment vis-à-vis the quality of forage. In a model of high forage content (and therefore changing from cereals and/or protein concentrates), the variations on the quality of the latter in terms of milk production are larger because concentrates do not lend themselves to too many ration adjustments. Working with low NDF levels and with high digestibility forages (dNDF) are essential goals.
According to the above mentioned, rationing should aim to:
Then, once we have built in more forage into the diet, the challenge is achieving a good use (digestibility) of ingested fibres. Rationing should take into account forage/concentrate interactions happening in the rumen in order to maximize the digestibility of forage. A well known fact is that fibre digestion is sensitive to low pH values. Therefore, any dietary change that will help maintain the rumen pH, such as supplying the right size of fibre in order to encourage mastication, build in yeasts or monitoring fermentation rates of starches, may contribute to make the most out of fibres.
See below some of the factors that improve fibre digestibility in rationing:
Generate a fibrous mantle. Fibre digestion is slower if compared to that of other dietary components. As a result, it can only be efficiently digested if it remains in the rumen for a long time. In addition to its impact on mastication, a proper particle size will also have an effect on the fibre retention time in the rumen. Though the dietary fibre content may be the right one, if the fibre is too thinly minced it will not generate a good fibrous mantle (the mantle that floats over ruminal fluid, see the Figure). Consequently, the retention time of fibrous particles will be shorter and the quality of digestion will be worse.
Control starch sources. In those diets where the use of concentrates is limited it is key to maximize the use of starches. Starch digestibility may range between 70-100% (Firkins et ál. 2001). Differences in digestibility will depend on particle size (small or large), grain processing, storage system (dry or PASTONE), humidity and fermentation time of silage, as well as the type of endosperm (amylase/amylopectin ratio).
Non-Protein Nitrogen (NPN). The main source of Nitrogen from fibre digesting bacteria is ammonia. Therefore, one of the issues in the use of fibre can be the lack of that substance in the rumen. Ammonia comes from protein breakdown in the rumen (using energy resources) or from dietary NPN (with the risk of raising ruminal ammonia concentration too much, and using energy for catabolism). Controlled release urea’s that guarantee the constant supply of ammonia in the rumen at the right proportions, have shown a positive effect on fibre digestion.
Pictures below show improved diet efficiency after stool screening, once controlled release urea (NPN) is added to the ration.
Sugar addition. Most studies show that adding sugar to the diet (up to 5% over DM) increases butirate and valerate concentration in the rumen (Heldt et ál. 1999). These volatile fatty acids (VFA) help improve the development of the ruminal epithelium thereby improving acetate and propionate transfer to the bloodstream which in turn encourages the stability of ruminal pH increasing fibre digestibility as well.
The goal is having a constant supply of a ration based on fresh, top quality and appetising ingredients throughout the entire day. This may require some adjustments in terms of the number of times food is mixed and delivered to the herd throughout the day. Special attention should be paid to the following points:
Forage Analysis. In order to maximize its use, it is essential to know the quality of the available forage. Fibre digestibility is one of the parameters that should be routinely included in the analysis. In our circumstances, silage will be the most usual approach for efficiency purposes. In addition to nutritional quality, attention should be paid to the quality of fermentation, not only in order to decrease losses during the silage process (so as to have more forage available), but to guarantee high voluntary intake.
Handling of the unifeed wagon. When increasing the percentage of forage per cow, the density of the mix is lower (kg/m3). This may limit the capacity of our wagon so, unless we have a larger one available, we will have to prepare more than one mix so as to achieve the right one. The presentation of the mix should not encourage choosing by the cattle.
Particle size and choice. The presentation of the mix should not encourage cows to choose. Choosing generates changes in ruminal pH that decrease fibre digestion ad increase the risk of occurrence of metabolic diseases (acidosis, laminitis, etc.). In diets containing a high percentage of forage, and hence apparently healthier, the risk may lie on those rations that have too large particle sizes and/or too dry forages.