Variability of nutrient content in feed ingredients – What effect it has on nutrient output


Source: Ontario Ministry of Agriculture, Food and Rural Affairs

Fact Sheet written by: Ron Lackey- Feed Ingredients and By-products Specialist/OMAFRA

Environmental Importance Of Nutritional Strategies

Adopting nutritional strategies to minimize the environmental impact of livestock production will be most effective when the variation in nutrient content, as well as the biological availability of nutrients from individual feed ingredients, is taken into account. Livestock and poultry are raised because of their ability to convert mainly plant materials (grains and forages) into consumable commodities such as eggs, meat and milk. The conversion process is not, nor is it feasible or realistic to expect it to be, 100% efficient. Nutrients contained within the plant materials that are consumed, but not utilized by the animals for maintenance and production, are excreted in the manure. In order for livestock production to be not only environmentally sustainable but also economically sustainable, the livestock/feed industry must be able to recycle the flow of all feed nutrients, but particularly nitrogen (N) and phosphorus (P) from animal manure back to the soil where they can again be used for crop production. In fact, there is an expectation from the broader public than anything less than this should not be considered an acceptable farm practise. The challenge then, for the livestock producer and the animal nutritionist is to accurately determine for each feed ingredient; its nutrient content, the bioavailability of those nutrients to the animal and the factors that affect the bioavailability of the nutrients contained within individual feed ingredients. Once this information is known, the amount of supplemental nutrients can be carefully adjusted to balance the diet to optimize animal performance and potentially reduce the amount of nutrient excretion that needs to be managed for crop production.

Feed Ingredient Variability

Feed ingredients vary considerably in their nutrient content — not only across ingredients but also potentially within a single feed ingredient. For example University of Guelph research that analyzed phosphorus levels and phytate levels in a number of Ontario corn and soybean samples found significant differences. Total phosphorus content in corn ranged from a low of 0.22% to a high of 0.63%, while the phytate levels (portion of phosphorus not normally available to monogastrics) varied from 48.93%–89.5% of total phosphorus. With soybeans total phosphorus levels varied from 0.36%–0.84%, with the percent as phytate from 43.3%–70.7%.

Expedient Ingredient Analysis

Unfortunately, at the present time there are no commercially available methods to analyze for phytate levels. Near Infrared Reflectance Spectroscopy Analysis (NIRA) is being considered as the potential method to provide this analysis. It is known to be fast and economical and is presently used by some commercial feed mills to provide proximate nutrient analysis. NIRA is also presently being field tested as a potential system to provide amino acid profiles. The variation in the nutritional content of feed ingredients is both an economic and an environmental concern. Because of this variation and without a timely nutrient analysis, formulating rations to more precisely meet the animals’ maintenance and production dietary needs becomes a challenge. Generally speaking, without complete and timely ingredient analysis, feed manufacturers tend to over-formulate to account for nutrient content variability. This not only increases ration costs and but also potentially introduces excess nutrients to the environment.

Proven Nutritional Strategies

Through research, several nutritional strategies have proven to be effective in reducing the levels of P and N in livestock excretions. For example, adding phytase to monogastric rations can reduce the amount of supplemental phosphorus needed, which in turn lowers P levels in the manure. Lowering the protein levels and balancing the amino acid profile in formulated rations with synthetic amino acids can reduce N output. Phase feeding — where levels of available nutrients are adjusted frequently to more closely meet the nutritional needs of the particular animals — can reduce P and N outputs. Reducing the amounts of supplemental P fed to ruminants will lower the P output. All of the nutritional strategies mentioned here can help reduce the levels of nutrients introduced to the environment in manure. However the impact of these strategies will be greatest when they are based on an accurate and timely knowledge of available nutrients contained within the feed ingredients being used. The development of methods to provide timely and accurate analysis of phytate levels and amino acid profiles in individual feeds will help to maximize the benefits of these strategies.

Do you know about Ontario’s new Nutrient Management Act?

The provincial Nutrient Management Act (NMA) and the Regulation 267/03, as amended, regulates the storage, handling and application of nutrients that could be applied to agricultural crop land. The objective is to protect Ontario’s surface and groundwater resources

Please consult the regulation and protocols for the specific legal details. This Factsheet is not meant to provide legal advice. Consult your lawyer if you have questions about your legal obligations.

Factsheets are continually being updated so please ensure that you have the most recent version.