A better characterisation of a forage must go beyond the traditional criteria (percentage of dry matter, protein, fiber, starch, minerals), and allow for an accurate estimation of the way ruminants are likely to optimise the forage. In addition to the net energy calculations and the amount of digestible protein in the intestine, the following criteria must be considered:
- Knowledge of the voluntary intake of forage is essential as it directly impacts nutritional intakes. One extra kg of DM ingested corresponds to an additional supply of 1.55Mcal NEL / animal/day kg DM. This is more or less equal to the amount of energy necessary for producing 2 kg of milk.
- Starch degradability in the rumen (soluble, slowly degradable or bypass): When it comes to predicting the extent of acidogenic risks raised by forage ingestion, starch content is often the main benchmark. However, practical observations have clearly shown significant differences in acidosis risks for forages of similar starch content. Since acidogenic risks are linked to the soluble starch content of forages, these discrepancies mainly relate to the way starch is degraded in the rumen.
- DM rapidly degraded in the rumen (within four hours): This criterion allows one to evaluate the extent of likely SARA (sub-acute ruminal acidosis) risk in forage. Consideration of this parameter when designing a ration will lead to striking the right balance between the amount of fermentable energy required for production ends and SARA risk prevention.
- Fibre digestibility: Ruminants are able to easily digest the fibres contained in their forages. Fibres largely contribute to the net energy intake. The ruminant’s digestion process highly depends on the composition of these fibres.
- Fractions of fat content (digestible in the rumen and bypass): Fat is a very concentrated source of energy. Fat is also useful for increasing the total energy intake of animals endowed with strong genetic merit (strong production potential). However, special attention ought to be paid to fat fractions that are too promptly digested in the rumen. These may have a significant impact on the rumen ecosystem and therefore,on the efficiency of fermentation.
Evaluating the different nutrients contained in forages allows an accurate assessment of their values. These values also highly depend on crop/culture conditions and conservation. To ensure optimal quality of forage, various levers and guidelines can be implemented: These relate to harvest stages, hashing methods, silo conceptions etc. The TECHNA Group can also provide NIR calibrations designed to estimate the values of a wide range of forage. Should you want to know more, please do not hesitate to contact our experts!