Guidelines for Developing Dairy Rations

Charles C. Stallings
Extension Dairy Scientist, Nutritionist
Virginia Tech
8/99

Shortages of forage resources due to less than optimal growing conditions can result in the need for the development of dairy rations. The followings guidelines should be of help with their development.

Forage dry matter (DM) consumption for lactating dairy cows usually will range from 1.5% to 2.5% of the cows body weight. On rations with low-quality (high-fiber) forages, high-producing cows will usually average forage DM intake of 1.5% to 2.0%. Lower producers may average 2.0% to 2.5%. With low-quality forages, high-producing cows need more supplementation, which leaves less room for forage in the overall ration. If hay and silage are fed, it is usually best to limit hay to 10 lbs./cow/day or less and silage can be fed as needed. If feeding a total mixed ration it is advisable to incorporate hay into the mix by chopping before mixing. Some mixers will chop long hay as they mix. Below is an example of how to figure the forage dry matter from silage if 5 lbs. of hay dry matter is fed.

Example: 1300 lbs. body weight * 2% (or .02) = 26 lbs. DM
or
1300 lbs. body weight * 1.5% (.015) = 19.5 lbs. DM

5 lbs. hay DM fed; 26 - 5 = 21 lbs. DM from silage or 60 lbs. of wet silage (35% DM) or 19.5 – 5 = 14.5 lbs. DM or 41 lbs. of wet silage

Therefore, to get adequate forage dry matter intake with 5 lbs. of hay dry matter (5.5 lbs. as fed), we would need at least 41 lbs. and up to 60 lbs. of corn silage. Do a feed inventory to see if you have adequate supplies. Calculations would need to be adjusted if silage dry matter is drastically different than 35%.

Feeds that can contribute to the forage requirement other than pastures, silages, hays, or green chop are cottonseed hulls, whole cottonseeds, and brewers grains. These feeds should be limited to10% to 15% of the ration dry matter. In all cases, DM intake of at least 1.2% to 1.5% of body weight should be maintained from forages (pastures, coarse cut silages or green chop, or hay). This is to ensure adequate cud chewing and rumination. Adding .3 to .5 lb./cow/day sodium bicarbonate might be of benefit when forage consumption is marginal. Also rations should contain at least 18% acid detergent fiber and 28% neutral detergent fiber in the DM. Silages should be chopped 3/8- to 3/4-inch or longer to stimulate rumination.

High-energy feeds are needed to supplement high-fiber, low-quality forages. Feeds such as hominy, corn, barley, milo, or oilseeds complement low energy feeds. Oilseeds or fats can be used to increase energy in rations, but should be limited so that no more than 1 lb. to 1.5 lbs. of fat is added. In some cases feeding more starch is not advisable, and using soybean hulls to replace some corn or barley is recommended. Soybean hulls are a readily digestible fiber source but contain no starch. Excess starch can cause a drop in rumen pH and acidosis. The following are some recommended limitations on certain feeds in rations for lactating dairy cows. Remember these are maximums and not necessarily optimal amounts..

% concentrate lbs./cow/day
Urea 1.5 0.5
Fish meal 3 1
Tallow 4 1
Soybean hulls 20 5
Wheat middlings 20 5
Cottonseed hulls 20 5
Cottonseeds and soybeans, whole --- 7
Brewers grains, dry 25 7
Distillers grains, dry 25 7
Corn gluten feed 30 10
Brewers grains, wet --- 30

This might be the year to consider having a spring crop for silage of either rye or barley. Rye will be available earlier and can be grazed, but making quality silage can be difficult because of our normally wet springs. A better alternative might be barley harvested at soft dough stage and direct cut for silage. Wheat can be used for silage, but it is usually later at harvest. Barley and wheat silage that is direct cut at soft dough stage will yield more than rye and will be more like corn silage when used in rations.

Buying hay might be an option this year. I have received inquires about the value of hay. If you compare energy and protein in hay to the cost of the same coming from corn and soybean meal, it seems that hay is overpriced. Alfalfa hay is bringing $150/ton or more. However, if roughage is needed, it may be worth paying these higher prices. Remember, corn and soybeans have been low in price recently. Some good-quality roughage might increase milk production and should be considered more than just an energy and protein source. The Virginia Department of Agriculture (VDACS) has a Web site that lists hay sellers from surrounding states. Let me know if you need the address.

Recent rains have probably reduced the levels of nitrates in feeds. However, if plants are drought stressed around harvest it might be a good idea to check for nitrates. The Virginia Tech Forage Testing Lab can run a nitrate test. Dairy Guideline 404-163 gives levels of nitrates in feed and water that are considered a problem. Ensiling will normally reduce levels by 50% or more. Ensile at least 3 weeks before feeding if possible. Raising the cutter bar during harvest may reduce levels because much of the nitrates are in the stalk. If levels are still elevated after ensiling, amounts may have to be limited in rations. Forages most likely to be a problem are plants in the sorghum family and corn for silage. Corn for grain is not a problem because nitrates are in the stalk not the ear.

Aflatoxins could be a concern. Dr. Dennis Blodgett of our College of Veterinary Medicine says that the critical time for aflatoxin formation is at time of silking. Dry years are the worst for aflatoxin contamination in corn. He recommends checking the silage, not just the ear, when looking for presence of aflatoxin. Rations should contain less than 20 parts per billion. Levels of 30 parts per billion can cause residues in milk. It is possible to feed bentonite or activated charcoal to bind toxins in the gut to prevent absorption. However, this may not prevent detection of residues in milk if high levels are in the feed. Removing or diluting the source may be necessary.

We hope the rains will continue and the crops will keep growing. Every year is different, and each presents a new set of circumstances. This year is certainly no exception. Please let us know if we can be of assistance.