PHOSPHORUS FOR BEEF CATTLE by Mike Mehren Ph.D.

PHOSPHORUS FOR BEEF CATTLE
BY MIKE MEHREN

This month seems like a good time to discuss phosphorus, since it’s crucial to livestock health and production...and the cost is going through the roof! Phosphorus is a mineral that is in most feeds. Most supplements have added phosphorus because many plants growing in the Pacific Northwest are deficient in this mineral, so whether you purchase a mineral, protein supplement, creep feed, bull developer, supplement tub, liquid, or block, some amount of phosphorus has probably been added.

What we need to determine is how much is really needed. Just a few years ago, phosphorus was $300/ton; it will pass $600/ton sometime this year. To put this in perspective, if you buy a product that has 6% phosphorus and the price is $300/ton, then the phosphorus cost alone would be $86.00/ton. At $600/ton it is $172.00/ton. It is the single highest cost item in most supplements. The best way to determine if you need it is
by taking a sample of your feed and have it tested at a feed lab (sorry about that, it was too easy to slide in there). Many mineral supplements have 12% phosphorus. Even oldtimers like me can figure that would be $344/ton just for phosphorus alone.

Feed phosphate is different from fertilizer grade phosphate. The biggest difference is in the impurities that have been burned off. A mineral element of great concern is Fluorine. You and I think of fluorine as a toothpaste and water additive that helps prevent cavities. However, high levels can be trouble when fed to livestock for any great length of time. The maximum amount of fluorine in feed grade phosphate is 1 part fluorine for every hundred parts of phosphorus. This isn’t true of fertilizer grade; fluorine can be considerably higher. Fluorine toxicity takes a long time to show symptoms, so the cause may be hard to determine. Fluorine accumulates in bone tissue, joints, and teeth. Damage depends on age of the animal, amount consumed, and diet. Fluorine sources include water, forage, and feed supplements.

There are several sources of feed phosphorus: Some are listed below.

Product	Calcium	Phosphorus
	.........percent as fed......
defluorinated phosphate	31	18
mono dicalcium phosphate	18	21
Mono Ammonium Phosphate*	--	24
Monosodium Phosphate	--	26
Soft Rock Phosphate	15	9 (high in fluorine)

• since this contains ammonium, it provides non-protein nitrogen, and that must be declared on the label when used.

Phosphorus content of feed differs quite dramatically. Some typical values follow:

Product	Calcium	Phosphorus
Grain	0.03	0.30(corn,barley,oat,wheat=)
Corn Silage	0.31	0.27
Corn Stover (stalks,leaves,cob)	0.49	0.09
Alfalfa Hay	1.40	0.23
Pea Hay	1.39	0.28
Wheat Straw	0.19	0.09 (barley,oat straw =)
Spring grass	0.36	0.26
Grass Hay	0.18	0.26
Grass Seed Screenings	0.29	0.28
Grass Seed Straw	0.26	0.08
Wet Corn Distillers w/ Solubles	0.04	0.58
Grazing Triticale	0.20	0.28

These are only AVERAGE values; your feed may be quite different. By-products and hay or silage have the greatest differences. Grain does not vary much.

The National Research Council publishes a book called Nutrient Requirements of Beef Cattle. The latest edition was published in 1996. In it, they list the requirements for phosphorus. For backgrounding steers and heifers, 0.23% is the amount needed. For replacement heifers that will mature at 1400 lb, the requirement is 0.23% of ration dry matter. For high producing 1400 lb cows, the requirement is also .23%. Finishing heifers, steers and very rapid gaining bulls have the highest P requirement; 0.32% of ration dry matter. The ratio of calcium to phosphorus in the diet is also discussed. The authors note that several studies have concluded that feeding any ratio of calcium to phosphorus from 7:1 to 1:1 will result in similar performance as long as the minimum phosphorus need is met.

Since this column is directed at cow-calf, backgrounders, and stockers, let’s compare the feeds with the requirements. Those feeds in bold type and underlined would need
no supplemental phosphorus.

Let’s look at a couple of examples:

Feeding 1200 lb cows nursing young calves.	Calcium	Phosphorus
30 lb alfalfa hay feeder	1.4%	0.23%
5 lb straw	0.26%	0.08%
4oz salt/min mix	6%	6%

Provides 1.27% Ca and 0.25% Phosphorus: Ca:P ratio 5:1. There is NO NEED to provide more phosphorus just to achieve a 2:1 Ca:P ratio. You could actually feed a mineral that had slightly less P.

Feeding the same group of cows and calves Calcium Phosphorus

18 lb alfalfa hay, feeder	1.4%	0.23%
7 lb straw	0.26%	0.08%
45 lb corn cannery silage	0.34%	0.28%
4 oz salt/min mix	8 %	4%

Provides 0.83% Ca and 0.24% Phosphorus: Ca:P ratio 3.5:1. Again no need for extra
phosphorus.

Calves turned out to spring grass. Spring grass usually has enough calcium and phosphorus to support a high rate of gain. We routinely see spring and early summer gains of 3.0 lb daily without added calcium and phosphorus. This is not true during
late summer and fall.

If we pastured triticale and other grains, some will have negative calcium:phosphorus ratios (0.20 Ca; 0.26 P). Adding additional phosphorus will have a negative impact; calcium needs to be added to the mineral supplement. Feeding a mineral supplement with P can actually make the problem worse. This also occurs on some irrigated crops. Take a sample and have it tested to determine mineral content.

All of the rations shown above have adequate protein and energy. As expensive as phosphorus is, a protein supplement will be much more expensive. A very high priced
mineral at $800/ton costs $.10/head/day at 4 oz. intake. The amount of mineral consumed has a direct relationship to cost/head/day. A $1600/ton mineral that is consumed at 2 oz still costs $.10/head/day. A protein supplement costing $400/ton costs $.20/head/day at 1 lb intake. This amounts to spending $.10/head/day for a supplement that wasn’t needed
in the first place.

The bottom line in this discussion is that in order to keep cost under control, you have to know what your feed has or doesn’t have. In mineral supplements, the amount of phosphorus has a tremendous influence on the cost of the product. If it’s needed by your animals, then it will be cost effective, however if it isn’t, that is some money that you can keep. Right now the biggest crisis that I have been working on is finding enough hay or straw to feed before spring turnout. Next year’s calf crop can potentially suffer huge damages if the cows aren’t taken care after calving and before breeding. Don’t weaken now; you’re almost there!

Michael J. Mehren, Ph.D. is an old livestock nutritionist from Hermiston, Oregon who has devised equipment and a process to convert cowpies to ethanol. He anticipates windfall profits from this technology and will gladly share some of the profit with his readers. He can be contacted by Email at mehrens@eotnet.net.