ALFALFA: RUMEN HEALTH AND FEED EFFICIENCY

Alfalfa is a widely used ingredient in animal nutrition, due to its excellent nutritional values per se. Harvested at proper time, it is an excellent source of highly digestible protein, as well as vitamins and minerals.

This post however, is focused on Alfalfa as a source of physically effective Neutral Detergent Fiber (peNDF). An essential nutrient in ruminant diets, whose role in rumen health as well as in the digestion of other nutrients, has been widely assessed by a large number of scientific works.

Most of the ingredients from plants (cereal grains, oleaginous seeds, forages, etc.), used in livestock diets, content a varying amount of NDF, which is directly related to their fiber content.

However, not all of NDF has the capacity of promoting ruminal contractions, ruminal net formation, salivation and hence stimulating an appropiate ruminal pH. It will depend on their physic and chemical characteristics. This NDF that can promote these activities, previously named, is considered as physically effective NDF.

Actually, there are different methods and systems which try to estimate the effectiveness of NDF from different ingredients. Among these, the most remarkable are the recommendations made from NRC (2001), Michigan University and Cornell University. As for this last reference, Cornell University has developed the Cornell Net Carbohydrate and Protein System. This system assigns different values to the effectiveness of NDF from non forages, as well as modifies the effective values of NDF from forages, depending on their processing and particle size.

Many previous scientific studies have been performed in order to assess the role of peNDF in ruminant diets with a common factor. They all used Alfalfa as the main source of peNDF, trying to evaluate how their presentation (Alfalfa silo vs Alfalfa hay) and particle size (long stem, chopped or ground) affected its effectiveness.

Nowadays, researches continue in order to quantify the peNDF requirements of ruminants (depending on the species, type and level of production), as well as to assign proper values of peNDF to different ingredients.

But… Why is so important peNDF in Ruminant diets?

One of the main reasons for making up diets with an adequate level of peNDF is to prevent subacute ruminal acidosis (SARA). Ruminant fed diets high in cereal grains, are exposed to suffer a chronically low ruminal pH because of the accumulation of acids (mainly Volatile fatty acids - VFA and lactic acid) from ruminal fermentation of daily intake.

This situation isn’t desirable at all, firstly because it decreases the digestion of certain nutrients from diet which potentially leads to a yield decrease.

Secondly, if this situation persists and due to rumen wall isn’t cover with mucous unlike monogastric, acids will cause ulcerations and scars. This situation can be approached by Fusobacterium necrophorum, present in rumen fluid, to migrate from the ruminal ulcers to the liver via the portal blood. This bacterium produces toxins, which cause liver abscesses and a variety of dysfunctions.

How can peNDF prevent digestion disorders?

As for this, SARA can be prevented with an adequate amount of peNDF in daily diet. It will help to the ruminal health, acting in different ways:

-The presence of peNDF promotes ruminal contractions which help washing out VFA from rumen to abomasum, where they are absorbed more efficiently, avoiding their accumulation, hence contributing to increase pH value in the rumen.

-Promoting chewing activity and saliva production. Saliva is the main source of bicarbonate to the rumen as well as it serves to dilute acids, produced in rumen fermentation. Bicarbonate acts as a buffer against the action of acids and serves to raise pH value in the rumen.

How can peNDF enhance the utilization of nutrients from diet?

Another important action of peNDF into the rumen is to contribute in the formation of ruminal mat. One of the main functions of ruminal mat is to promote particle retention. Some authors have described ruminal mat as a very effective filter for undigested small feed particles. Ruminal mat acts decreasing the escape of these potentially degradable feed particles from the rumen, thus enhancing fiber degradation and feed utilization.

Furthermore, adding to this latter effect, the effect of promoting ruminal contractions previously named. It has been described that an adecuate level of peNDF together with a suitable particle size lead to a higher microbial protein synthesis into the rumen and a greater flow of microbial nitrogen to the duodenum.

To summarize, with the inclusion of appropriate amounts of Alfalfa or other high quality forages in ruminant diets, we are not only covering their nutritional requirements, but also due to their peNDF content, we are enhancing rumen health and feed efficiency.

REFERENCES

James B. Russell. 2002. Rumen Microbiology and its Role in Ruminant Nutrition.

Alex Bach, Sergio Calsamiglia. 2002. Manual de Racionamiento para el Vacuno Lechero. Editorial Servet.

W. Z. Yang, K. A. Beauchemin, and L.M. Rode. 2002. Effects of Particle Size of Alfalfa-Based Dairy Cow Diets on Site and Extent of Digestion. J. Dairy Sci. 85:1958-1968

K. A. Beachemin, B. I. Farr, L. M. Rode and G. B. Schaalje. Effectos of Alfalfa Silage Chop Length and Supplementary Long Hay Chewing and Milk Production of Dairy Cows. J. Dairy Sci. Vol 77. No 5. 1994

Q. Zebeli, J.R. Aschenbach, M. Tafaj, J. Boguhn, B. N. Ametaj, and W. Drochner. Role of physically effective fiber and estimation of dietary fiber adequacy in high-producing dairy cattle. J. Dairy Sci. 95:1041-1056

Your comments and suggestions are welcome.