Brady Campbell, Ohio State University sheep team

Forages in modern small ruminant production systems

By Brady Campbell, Ohio State University Extension small ruminant specialist

Because of their versatility, forages play an important role in modern small ruminant production systems as they can be grazed or harvested and stored as fermented or dry feeds for later use. Forages are unique as they contain structural carbohydrates, in the form of cellulose, that can only be digested by rumen bacteria. When compared with grain-based diets, one disadvantage that is associated with forage-based diets is the number of bacteria that are used to digest forages is much lesser than those used to digest grains (3 billion bacteria per milliliter of rumen fluid in forage-based diets vs. 8 billion bacteria per milliliter of rumen fluid in grain-based diets). Rumen bacteria provide ruminants with a large proportion of daily crude protein intake, therefore, diets that are greater in forages may result in less protein available on a per pound basis when compared with grain-based diets and thus require additional supplementation. However, this slight inefficiency should not be “the end all be all” as marginal lands not suitable row cropping or commercial development as well as environmental challenges negatively impacting row cropping systems may greatly benefit from the incorporation of forage production.

From an animal perspective, increased levels of forages in the diet result in the production of a greater proportion of acetate, a volatile fatty acid (VFA) produced and used in fatty acid synthesis. It is often recommended that ewes and does be offered high quality forages during late gestation and early lactation as this VFA is used in milk fat production, which is an important energy source for newborn lambs and kids. This is just one example on why it is so important to test your forages. 

Comparatively, diets containing greater proportions of grain during late gestation and early lactation would result in a greater proportion of propionate which supports the production of milk volume. However, during this critical period, milk volume is not needed as the small size of the newborn lamb or kid will regulate the amount of milk that is consumed. Therefore, it’s more important that colostrum and milk be energy dense because of limited intake.

Moreover, feeding or grazing forages tends to increase rumination time in our ruminant species. Rumination is an important process as it generates saliva which aids in buffering the rumen environment. This buffering function allows the rumen to function properly as rumen bacteria may perish once the pH drops and the rumen environment becomes acidic. Forages also provide roughage, which is essential to proper ruminant function and health. Neutral detergent fiber (NDF) is used to describe the bulk density or gut fill of the diet. Diets with high NDF values will limit the intake of the diet. Alternatively, diets with low NDF values will result in a high passage rate. High passage rates are also undesirable as feedstuffs requiring more digestion pass through the system too quickly, thus loosing access to nutrients in the process. Therefore, forages that provide a moderate NDF value are beneficial as this allows for a slowing in passage rate and potentially for the animal to better digest the feeds they are consuming.

From an environmental perspective, grazing allows for efficient use of land. When talking about any type of feedstuffs, those that are harvested by the animal themselves are the most cost effective as there is a decrease in labor and machinery overhead costs. Therefore, grazed forages provide for a cost-effective nutrition plan. In years past, where it became challenging to plant row crops due to excessive rainfall, forages were planted in crop ground to maintain soil activity as typical row crops could not be planted. In taking advantage of this, alternative forages may be available for harvest to be used as an alternative feedstuffs for our ruminant species. This can be critical step in securing the sustainability of a production system as producers without pasture and stored feed reserves would have to purchase additional feeds at a greater cost. 

Furthermore, forages may be able to be grown on marginal ground, which otherwise would not be used for agricultural purposes. In areas with poor soil conditions, intense slopes, and reduced rainfall, forages may be well suited in these areas. In using these areas that would have otherwise not been used for agricultural purposes, producers may be able to graze and or harvest forages to feed to small ruminants and produce a high-quality protein source.

By no means is this an exhaustive list of the importance that forages play in the production of small ruminants, but rather a discussion to get conversations started.. Until next time, happy shepherding!

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