Nutritional Strategies to Reduce Nutrient
Output in Beef Manure

The cattle industry has taken some blows on the environmental front; some concerns are realistic, while others are dramatized. However, any commitment to reducing nutrient losses into the environment from farms will certainly be applied to beef producing operations. Although manure nutrients have fertilizer value, the movement of nitrogen and phosphorus out of the cropping system can have environmental consequences. Nitrogen can escape below the root zone and appear as nitrate in wells while phosphorus contributes to algal blooms in surface waters. There are a number of nutritional interventions that can lower N & P levels in manure, allowing for higher animal carrying capacities on a given land base and reduced environmental risk. In several cases, these are profitable choices too!

Nitrogen Reduction

The ultimate source of nitrogen in manure is dietary nitrogen (N) or crude protein (CP). As is the case in most species, excess dietary nitrogen is the prime cause of increased beef manure nitrogen. In forage rations (backgrounding, lactation of replacement heifer rations) excess dietary CP is often caused by using feeds high in CP as a side effect of trying to achieve better forage quality. The favour that has been shown for alfalfa as opposed to grass hay and haylage is a symptom of this. More protein is not better! In fact, too much may impede reproduction. At peak productivity, a cow or backgrounded steer needs no more than 15% CP in the forage ration. The solution, do achieve high forage quality by youthful harvest, and look at net energy (NE) or total digestible nutrient (TDN) values before CP to determine what is good forage. Consider more grasses in the mix, they have all the energy and other nutrients but less nitrogen than alfalfa and other legumes.

In the feedlot, poor protein quality is often addressed by feeding more total CP. One way to ensure amino acid requirements are met without feeding CP inflated diets are rumen escape proteins (sometimes referred to as rumen UIP, RUP or 'bypass' protein). They may actually help meet protein requirements while lowering total dietary CP. At this point in time, pencilling this might be tough, but who knows what the future holds.

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Phosphorus

Excess phosphorus (P) has long been known to cause problems such as urinary calculi (waterbellies) when fed in excess. Health problems are reduced at more moderate overfeeding, but there is still a level environmental risk. It has recently become accepted that ruminants make better use of phytate phosphorus than previously accepted. A number of researchers, nutritionists and extension staff have reported that corn-based feedlot rations require no supplemental P. The most recent "Nutrients Requirements of Dairy Cattle" (Published by the National Research Council, 2001) has slashed P requirements by 25%. What's the message? Until it is known otherwise, do formulate beef rations to recommendations for P, but maybe the precautionary principle of adding extra P to ensure performance has outlived its usefulness.
In breeding animals, high P minerals (1:1 Ca to P ratio) have been a popular product for cattle producers. Assuming regular mineral supplementation is occurring, the cases where the use of a high P product should be rare, and then only in rations where the forages are clearly deficient in P for a given level of production.

Overall Nutrient Efficiency

One of the most proven ways to reduce manure nutrient output is to improve productivity. A number of ways to reduce the units of feed per unit production and therefore reduce manure nutrient output are available. One simple way is to increase growth rate to offset maintenance feed requirements in the feedlot. This is achieved by implementing better health management, planned implant programs and better-balanced rations that include ionophores. Another way is to reduce the maintenance in the cowherd. This can be done by compressing calving seasons, improving reproductive performance and reducing cow size and the associated maintenance-feeding requirement.

The future as it relates to Nutrient Management will clearly have some challenges for the Beef Industry. There are however, opportunities! Taking advantage of these will maximize usage of land and may be closely related to improved performance!

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