HOW MUCH FEED DO I NEED? by Mike Mehren Ph.D.

Next we need to calculate the amount of feed dry matter. A dry matter figure is a routine part of a feed test. For this example, we will use 30% dry matter for the silage and 90% dry matter for the hay. So, 1014 tons x 30% dry matter = 304 tons of silage dry matter and 485 tons of hay x 90% = 437 tons of hay dry matter.

Next step is to calculate head days. This is the number of head times the length of time that they will be fed. For this example we have 500 calves that we estimate we will have to feed for 100 days. So, 500 x 100 = 50,000 head days.

We then estimate how much each animal will eat daily. These calves weigh 500 lb. when we begin feeding. Our goal is for them to gain 2.0 lb/day, so in 100 days they should weigh 700 lb. Their average weight would be 500 lb + 700 lb =1200 lb divide by 2 = 600 lb. We use 3% of their average body weight to estimate daily dry matter intake. 600 lb x 3% = 18 lb. of dry matter. To determine the amount of feed dry matter we need, we multiply 18 lb x 50000 head days. This equals 900,000 lb or 450 tons (900000 divide by 2000).

Normally, we’d like to feed this year’s crop this year, rather than carry a bunch of feed over until the following year. One way to do that is to make the ration up by using the amount of each feed. For our example this would be:

1014 tons of silage-- 68%	68 lb x 30% dry	20%
485 tons of hay-- 32%	32 lb x 90% dry	29%

1499 tons total 100%	100 lb	49% ---ration % dry matter.

If we feed the calves 18 lb of dry matter from a ration that is 49% dry matter we wind up feeding about 36 lb/head/day x 50,000 head days = 1800000 lb of feed. We have 1499 tons of feed or 2,998,000 lbs. For feeding the calves, we will only use 60% of our feed. In this example we could feed more calves, or use the feed for cows or other stock.

If we attack this problem from another angle where we need to buy feed, we could determine how much we need to buy. For instance, our ration is 20% corn and 80% hay. We estimate that we may need feed for the last 30 days, because our crops were short this year. By the time the animals need feed, they will weigh about 750 lb. There are 100 head on hand. We estimate that they will eat 3% of their bodyweight daily, which
is 22.5 lb dry matter or 25 lb as fed. Head days are 100 x 30 = 3000. So 3000 head days x 25 lb/day = 75,000 lbs. of feed. The ration is 20% corn, so 20% of 75,000 = 15,000 lb (7.5 tons) of corn and 60,000 lb (30 tons) of hay will need to be purchased.

One question that frequently comes up is the value of straw versus alfalfa hay. Straw may be selling for $65.00/ton and alfalfa that we purchased cost $120/ton. If you run the values per unit of protein and per unit of TDN, the straw is not a good buy for protein.

Cost/ton	Nutrient Content	Cost/Unit of Protein	Cost/Unit of TDN
Straw $65	Protein 6 TDN 44*	10.8	1.5
Hay $120	Protein 18 TDN 60	6.7	2.0

• this shows the problem with TDN versus Metabolizable Energy or Net Energy, which are the expression of calories that nutritionists use. TDN overestimates the energy value of roughages, especially straws.

However, during early pregnancy, we can save money by feeding a mixture of straw and hay versus feeding hay alone

Feed	lbs/cow/day	Cost/cow/day
Hay (@$120/ton)	25	$1.50
Straw (@$65/ton)	19	$.62
Hay	6	$.36
Total		$.98

Then 60 days before calving, we can still feed straw, but feed less because the fetus is growing rapidly, which requires more energy and protein.

Feed	lbs/cow/day	Cost/cow/day
Hay	30	$1.80
Straw	15	$.49
Hay	15	$.90
Total		$1.39

Then, after the cows calve we would still feed straw, but much less.

Feed	lbs/cow/day	Cost/cow/day
Hay	35	$2.10
Straw	8 (22%)	$.26
Hay	27 (78%)	$1.62
Total	35	$1.88

Using straw as shown above is for cows in moderate body condition. If you need to put flesh on cows, or feed 2nd or 3rd calf heifers, then you would start early in the fall and feed the ‘after calving’ mix.

Using grass, grain, or pea hay would be handled differently depending on the nutrient content of that particular hay (hint...use the feed lab!). You may not need to feed any alfalfa at all, or the amount may be quite a bit less. Remember: grass seed straw is not the same as grass hay!

A case could also be made for feeding whole corn, since its cost is not too much more than alfalfa. Corn has twice the energy of hay. So, in some instances 3 or 4 lb of corn could replace 6-8 lb of hay.

Although not mentioned in this article, a vitamin-mineral supplement would be an important part in all the rations mentioned. If things such as vitamin A, copper or selenium are deficient, the animals will not perform as expected. There may be breeding problems, retained placenta, scours, or white muscle disease.

Let’s run a quick comparison of the amount of vitamin-mineral supplement needed as opposed to a protein supplement.

Supplement Type	Amount Daily	Amount fed	Cost/ton	Cost Total over 120 days
Vitamin Mineral	2 oz	15 lb (120x2oz)	$600	$4.50/hd
Protein	1 lb	120 lb (120x1lb)	$300	$18.00/hd

Choosing the right supplement can have a tremendous impact on cost and amount bought. If you need a protein supplement, no mineral product will replace it. However in the examples shown above, no added protein is necessary and the added cost is substantial.

Plugging your figures into my examples will allow you to run the numbers and estimate how much feed your herd will need, so that you can plan ahead for the fall and winter ahead.

Michael J. Mehren is a livestock nutritionist from Hermiston Oregon whose hunting budget has been severely restricted by his wife. He may be contacted in his laboratory at mehrens@eotnet.net.