Chopping and Grinding Forages and Straw

When ruminant livestock cannot consume enough dry hay or roughage to meet nutritional requirements, intake can be increased by chopping or grinding. This may be particularly important when there is an abundant supply of roughage and grain is scarce or high priced. When roughage supply is limited it may also be necessary to ensure complete consumption of coarse stems, moldy portions, etc. Grinding prevents selective consumption and helps to mix and thus dilute portions of the ration which by themselves are unpalatable or possibly toxic. Grinding does not in itself make the feed any more nutritious; in fact it reduces the digestibility of the feed slightly, but because animals can consume more, a larger proportion of the feed intake is available for production (growth), and a smaller proportion is used for maintenance. Grinding also increases the ratio of propionic acid: acetic acid in the rumen which improves feed efficiency in beef cattle but reduces butterfat content of milk.

Guidelines

Don't grind forage for any class of ruminant livestock when the animal is capable of consuming amounts adequate to meet nutritional requirements. Grinding palatable rations for beef cows results in either overfeeding (wastage of feed) or the need to limit feeding (labor is wasted and cows have unsatisfied appetites).

Grind through one-half inch screen. Courser grinding may be all right for good-quality hay when self-fed "basis". However, coarser ground material will allow other ration ingredients to settle out during handling and in self feeders, and may lead to bridging in the mixer and self feeder. Finer grinding may be better for very low quality roughage but costs are too high.

Efficient grinding requires a high capacity grinder and a tractor large enough (100 HP or more) to handle it. Power requirements increase considerably as the moisture content of the hay increases. That is why it is important to put hay and straw up in a dry condition (less than 20% moisture) and to protect it from taking on moisture. Also grinding damp hay leads to bridging and may promote heating in large self feeders it left too long before feeding. When complete rations are to be processed, use a grinder mixer. If forage is to be self-fed and supplementary feed hand fed, a tub grinder may be used. (If roughage is in the form of round bales, a tub grinder will have to be used).

When using high levels of poor-quality roughage in the diet, proper supplementation is essential to avoid impaction.

Since many livestock procedures will be using unfamiliar feeds or rations during periods of feed shortage, they should keep a close watch over animal performance and adjust rations as necessary to meet production requirements.

Table 1. Example Ration for Early Weaned Calves^a

^aFeed a good quality grass hay free-choice

Table 2. Summary of Results Using Ammoniated Wheat Straw

^a all cattle received 3.1 lbs. of a protein-energy supplement

^b all cattle received 2.1 lbs. of a protein supplement

^c all cattle received 16 lbs. of alfalfa hay 3 times per week

^d cattle on untreated received 2 lbs. daily of a protein supplement, treated received 2 lbs. daily of a grain supplement

Footnotes to Feed Composition Table

1. On wet forms of various feeds, adjust price and feeding amounts depending on moisture content which can run as high as 80%.

2. All feeds containing sugar or starch can produce rumen acidosis. Such feeds must be introduced into diets slowly -- start with less than 0.4% of body weight and increase gradually. Fine particle size (dustiness) increases potential for acidosis and decreases the maximum amount which should be fed (less than 35% of diet). Mild acidosis may only decrease fiber digestion in forage diets while severe acidosis results in diarrhea, founder and even death of the animal. Acidosis with wheat midds should only be a problem at high levels (levels greater than 1.0% of body weight).

3. Total diet fat should not exceed 5%. Feeds high in fat should be limited to amounts which keep total diet fat at 5% or less.

4. High-phosphorus, low-calcium feeds should be supplemented with enough calcium to create at least a 1.3 to 1.0 calcium to phosphorus ratio.

5. Feeds like wheat midds, soybean hulls and to a lesser extent rice bran when fed at levels up to 1% of body weight in forage diets have a feeding value nearly equal to corn, but not at higher levels. Price accordingly.

6. Roughages of low digestibility are not consumed at high enough levels to be fed as the only feed. Some high quality forage or high levels of supplementation will be needed.

7. Rice hulls are very low in feeding value, sharp edged and irritable to the digestive tract which greatly limits their use.

8. May be fed at levels above 75% of the diet but swelling and bloat may be potential problems.

9. When fed as 100% of the diet or with highly fermentable feeds, bloat may become a problem.

10. Feeding at high levels more than 120 days may result in copper toxicity. Should not be fed to sheep.