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Managing Dietary Phosphorus for Livestock and Poultry

Phytate Phosphorus

Phosphorus is required in the diet of animals, but if overfed or wasted, can contaminate the environment and water supplies. Cereal grains fed to livestock contain phytate-bound phosphorus. Phytate-bound phosphorous is digestible by ruminant animals such as cows, sheep, and goats, but it cannot be digested by single-stomached animals, such as pigs and chickens. Phytate consists of a carbon ring structure with balanced phosphate groups surrounding the ring. Since horses are a hind gut fermenter, they are able to process the phosphorus much like ruminant animals.

Since phytate-bound phosphorous is unavailable to pigs, chickens, and other single stomached animals, phosphorous from other sources is supplemented to meet the needs of the animal. The extra phytate-bound phosphorus will be unavailable and excreted in the manure.

Reducing the proportion of cereal grains in the diet will usually reduce the amount of phosphorus fed. However, for pigs and chickens, and there are few economic alternatives to cereal grains. Plant breeders are working to develop feed grains lower in phytate content and higher in available phosphorus.

Phytase in the Feed

An enzyme called phytase can be included with the diet. Phytase will break down phytate and release digestible phosphorus. Mixing phytase (commercially available) in the diet will reduce the phosphorus required in supplements.

Interactions Between Nutrients

Another factor affecting phosphorus availability is the presence of other nutrients in the diet. Overfeeding calcium can limit the availability of phosphorus. Calcium and other nutrients should be fed in balance so as not to disrupt the availability of phosphorus.

Calcium:Phosphorus Ratio for Horses

Horses are a bit unique; they require calcium and phosphorus to be in a specific ratio in the diet. Young growing horses, as well as lactating mares, should receive a Ca:P ratio of 2:1, while mature horses not reproducing can get by with a 1:1 ratio. Calcium should never be fed at a level lower than phosphorus because phosphorus will tend to interfere with calcium absorption into bone. Horses at maintenance require .17% phosphorus in the diet and .24% Ca. The highest levels of phosphorus are needed in reproducing mares (.34%). Typical horse diets approach 2 to 3 times the required level of phosphorus, which can be detrimental to the environment. This high phosphorus level is partially due to the estimated Ca:P ratio in alfalfa hay being 6:1. Many horse owners try to counteract this by adding more phosphorus to the diets. Many equine supplements already contain more phosphorus than is necessary. There are also phosphorus concerns for ruminant animals such as cows, sheep, goats, and etc.

Ruminants and Phosphorus

Ruminant animals have a phytate enzyme produced naturally within the rumen that breaks down phytate-bound phosphorus and makes it available to the animal. According to the National Research Council, a lactating dairy cow requires between .35 and .40% phosphorus in the diet. Previous dairy feeding practices included as high as .55% or .60% phosphorus in the diet. This would mean an excess of 25 to 30 pounds fed to a cow in a normal lactation. If you multiply this over a dairy herd with 100 cows, then nearly 3,000 pounds extra phosphorous would be fed over the course of a year. Some dairy farmers think that phosphorus is a mineral required for proper reproductive function. While phosphorous is indeed important for normal bodily functions and is important for reproduction just as all nutrients are important for reproduction, there is no special link between phosphorus and reproduction in a cow. Most dairy farmers have already reduced phosphorus in their diets to levels given by the National Research Council.

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Managing Dietary Nitrogen for Livestock and Poultry

Diets should be managed to reduce nitrogen (N) losses. Protein is the chief N source in the diet, and N is the nutrient we are most concerned with. If a growing pig requires 22% protein in the diet and is fed 25% protein, then the excess (containing N) is going to be lost. Some N is going to be lost in the feces, and some that is absorbed is going to be lost as urea in the urine. Conversely, if a pig requires 22% protein, and is only fed 18% protein, then that animal’s production will be limited to the 18% level. In this case other nutrients in the diet will be in excess and cannot be utilized efficiently. Nitrogen feeding strategies are different for all livestock species.

Dietary Nitrogen Management for Ruminants

Ruminants (cow, sheep, goat, etc.) have a requirement for proteins that are quickly degraded in the rumen, called degradable intake protein (DIP). They also require proteins less quickly degraded or undegradable in the rumen, undegradble intake protein (UIP). If too much UIP protein is fed, then some of that excess will probably be excreted in the feces. On the other hand, if too much degradable protein is fed, there will be too much absorption of nitrogen into the blood supply and it will be lost in the urine as urea. Most research has shown that lactating dairy cows require about 32% to 38% undegradable protein in the diet, with the remainder being made up as degradable protein.

To learn more about protein for cattle see the following Livestock and Poultry Environmental Stewardship (LPES) Curriculum lesson sections:

Dietary Nitrogen Management for Non-ruminants

With non-ruminant animals, like chickens, horses, and pigs, individual amino acids are the basis of diet protein formulation. (Protein is composed of individual nitrogen-containing amino acids). A ruminant has a microbial population that produces essential amino acids in the rumen, so there is less focus on amino acids for them. In the case of pigs, horses, and chickens each individual amino acid is important. Lysine is usually the first limiting amino acid when feeding pigs and horses, and methionine is usually first limiting with chickens. Commonly used feeds are limiting in these amino acids and must be supplemented through balancing with other ingredients or by adding commercially-available crystalline amino acids to the diet.

To learn more about protein for non-ruminants, see the following Livestock and Poultry Environmental Stewardship (LPES) Curriculum lesson sections:

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Feed Management on Small Livestock Farms

Why Is Feed Management Important?

Nitrogen and phosphorus from agriculture sources can affect water quality. These nutrients are required for plant and animal growth, but too much in agricultural runoff can result in environmental and health concerns. This fact sheet provides some guidelines to help livestock producers, especially those on small farms, reduce nitrogen and phosphorus losses by monitoring and/or changing feeding and management practices. This can result in less waste and ultimately a healthier, cleaner, and safer environment. Wasted feed and wasted nutrients also represent wasted money for the farm.

Nutrient Balance on Small Farms

Nutrient inputs on a farm consist of feed, animals, irrigation water, fertilizer, legume nitrogen, etc. Outputs are meat, milk, animals, crops, and manure. When inputs exceed outputs, losses will be present in feed or barnyard waste, in manure, and in lot runoff, etc. These losses may result in excess nutrient storage in the soil. Nutrients may leach through the soil (nitrate) into ground water or run off the soil surface (phosphorus and nitrogen) and directly transported to surface waters.

Each farm should be seen as a complete system or cycle with inputs, outputs, storage, losses, and recycling all taking place. To illustrate, a 120-cow dairy farm will require 29.2 tons of nitrogen and 2.6 tons of phosphorus per year. Outputs (meat, milk, fiber, etc.) will be 6.9 tons of nitrogen and .8 tons of phosphorus, resulting in 22.3 tons of nitrogen and 1.8 tons of phosphorus for disposal, usually through spreading on available land. Similar calculations can be made for all livestock species. See “Whole Farm Nutrient Balance“…

If nutrients are overfed, or if feeding is mismanaged on an individual farm, this will result in more nutrients to manage in manure or as spoiled feed. While these nutrients can be applied to crop or hay ground to raise feed, it is important to try and keep this recycling loop as balanced as possible to avoid build-up of excess nutrients. Proper animal feeding and management practices can ensure that feed nutrients are not wasted, not overfed, and feed efficiency will be optimized on the farm.

Feeding Management

Feeding a balanced diet, avoiding overfeeding, and providing abundant supplies of cool, clean, and pure water will help to optimize feed and nutrient use on an animal farm. One way to understand nutrient requirements is to imagine a stave barrel. Only when all staves making up the barrel are the same length will water stay in the barrel. If all staves are 3 feet long, all the water will stay in the barrel. However, if one stave is a foot and a half long, then all the water will run out of the barrel to the level of a foot and a half. (See Figure below.)

barrel

CC2.5 LPELC

That is exactly what is happening with a balanced diet. If all nutrients are in a perfect balance, then there will be no excess and no wastage. It is impossible for all nutrients to be in a perfect balance in commercial or practical diets, but we want to come close to meeting an animal’s nutrient requirements. If the diet is balanced except for one underfed nutrient, then the entire production of the animal will be limited to the level of that “limiting nutrient” and all other nutrients will be wasted.

Overfeeding can be harmful to animals and to the environment. Animals that become overconditioned or obese may be unproductive and at greater risk of health problems. Excess feed is often wasted and may remain in the feeding area, become contaminated, and end up in the manure pile. Water is the most abundant, cheapest, and least understood of all nutrients required for livestock production. Water is of concern whenever it is in short supply or contamination is suspected. If subfreezing temperatures turn water into a frozen nutrient, it will mean trouble for domestic livestock. Distress is often brought on by cold wet winter weather requiring an animal’s digestive system and metabolic processes to function at peak efficiency to convert feedstuffs to energy so that they can remain warm, healthy, and productive.

Conversely, in hot summer weather, water is essential to the animal as well. It serves to cool the animal and works as a solvent or buffer for chemical reactions in the body. When the weather is hot in the summer, an animals’ requirement for water will increase. A lactating dairy cow requires on the average between 15 and 35 gallons of water per day; non-lactating dairy and beef cows require about 15 gallons per day; an adult horse will consume up to 15 gallons per day, which will increase 2 to 3 times when exercising; an adult sheep between 1 ½ and 3 gallons a day; adult swine from 3 to 5 gallons per day; and adult hens about a pint.

A quick rule of thumb is that for every 2 pounds of dry feed intake, an animal should receive one gallon of water. This will vary with stress, weather conditions, heat, cold, disease, productive state, work, exercise, etc., as well as the water and salt content of the feed. Often the first sign that water consumption is inadequate is when animals stop eating. Water is essential to maintain adequate feed consumption.

How does this affect nutrient management?

If we want our animals to reach maximum levels of production, then they will only have optimum feed intake if they receive adequate amounts water. Level of salt in the water or the diet can influence water requirements as can the presence of heavy metals, nitrates, microbes, and algae. Water is not related to runoff or contamination on the farm in the same way that overfeeding or imbalanced diets are, but water influences the ability of animals to use feed. If water is inadequate or contaminated, then animals will use diets less efficiently, eat less, be less productive, and may excrete more nutrients in waste.

How Do I Feed My Livestock to Avoid Waste and Maximize Efficiency?

Check out the list of helpful feed management tips for practical ways to manage feed and nutrients. Some of the topics on the page include:

Feeding animals is both an art and a science. It is a science influenced by years of research and it is an art developed by centuries of practical experience. Healthy animals fed balanced diets and provided with abundant supplies of fresh water will be the most productive. These animals will be the most profitable to the farmer and the most efficient users of nutrients.

References

  • National Research Council. 1989, 1994, 1996, 1998, 2001. Nutrient Requirements of Horses, Poultry, Beef, Swine, and Dairy. National Academy Press, Washington, DC.
  • Ralston, S. L. 1993. Analysis of Feeds and Forages for Horses. Rutgers Cooperative Extension. NJAES. Factsheet – FS714.
  • Singer, J. W. and D. L. Lee. 1999. Feed and Forage Testing Labs. Rutgers Cooperative Extension. NJAES. Factsheet – FS935.
  • Williams, C. A. 2004. The Basics of Equine Nutrition. Rutgers Cooperative Extension. NJAES. Factsheet – FS038.©2007 Rutgers, The State University of New Jersey.All rights reserved.
  • Rutgers Cooperative Extension Fact Sheet FS 1064
  • N.J. Agricultural Experiment Station
  • Rutgers, The State University of New Jersey, New Brunswick

Cooperating Agencies

  • Rutgers, The State University of New Jersey, U.S. Department of Agriculture, and County Boards of Chosen Freeholders.
  • Rutgers Cooperative Extension, a unit of Rutgers New Jersey Agricultural Experiment Station, is an equal opportunity program provider and employer. Published: June 2007

Authors: Michael L. Westendorf and Carey A. Williams, Extension Specialists in Animal Sciences, Rutgers, The State University of New Jersey. This article was originally published as Rutgers Cooperative Extension Fact Sheet FS 1064. Updated November 25, 2008.

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Equipment and facilities for managing manure on small farms

The number of small farms is increasing in much of the country, ensuring up to date information is available is important to protect water and environmental quality. This webinar focuses on some of the farm and manure management needs of smaller farms. This presentation was originally broadcast on April 20, 2018. More… Continue reading “Equipment and facilities for managing manure on small farms”

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