Where a high proportion of grain is fed and the roughage is of good quality, there is often adequate protein in the ration. If not, the addition of 1% urea will effectively boost the protein level and aid digestion. Rations for young cattle might be low in protein. If so, you can add a high-protein meal such as sunflower meal, linseed meal or cottonseed meal. Because young cattle require a high proportion of their protein intake from true proteins, these protein meals must be used in preference to urea to raise the protein level of the ration. As cattle slow their growth and become more finished, intake capacity often eases slightly. Weight gain may also ease as more of the energy consumed is converted into fat (higher energy content) rather than muscle. The preferred minimum entry weight for feedlot cattle is 250 kg (liveweight). Cattle can go on to the feedlot at lighter weights, but their protein requirements are so high that the ration becomes expensive and the time on feed is extended to achieve a marketable (although often not profitable) weight. Other componentsOther components of the feedlot ration include minerals, vitamins, salt, non-protein nitrogen and rumen modifiers.
Cattle need minerals to maintain good health. The most important are phosphorus and calcium. Grain is high in phosphorus and low in calcium, so with a high-grain ration, add calcium as ground limestone at a rate of about 1% (10 kg limestone/tonne) of the ration. This amount can be halved when lucerne hay is used as the roughage component. Extra phosphorus is sometimes added to weaner rations, usually at the rate of 0.1% (1 kg/tonne). Sulfur is often added to rations that include urea, while zinc and cobalt often improve the action of rumen micro-organisms. Other minerals could be needed, but deficiencies are unlikely to occur in short feeding periods (less than 100 days). Salt is added at the rate of 0.2% (2 kg/tonne) of the ration to supply the recommended daily allowance for sodium of 0.08% (0.8 kg/tonne). Non-protein nitrogen (NPN)Urea is cheap and physically easy to feed. However, it is toxic in excess, and inexperienced operators should not attempt to use more than 1% in their ration. See ‘Urea poisoning’ in Cattle health in feedlots. Feed at 1% by weight of the total ration. Because urea can be toxic if fed to excess, take care that this amount does not exceed 2% and that it is thoroughly mixed in the ration. Introduce it gradually, starting with 0.5% by weight (5 kg/tonne) of the total ration for the first 5 days.
WARNING: If urea is added to the feed in a powder form and trough cleaning is inadequate, urea may settle to the bottom of the feed bunk. If the trough is not emptied for several days and cattle then eat it out, there is a danger of individual animals eating excessive quantities of urea. This can be lethal. Always use prilled and not granulated urea. Vitamin A and E supplementation will be necessary for animals on feed for greater than 60 days. The supplementation may be required even earlier if animals entering the feedlot have been on dry feed or in drought conditions. Premixes should contain the recommended daily allowance of vitamin A as retinol (1000 µg/kg) or its precursor, ß carotene (4500 g/kg). Stored grains contain approximately one-third of vitamin E requirements for growth. Therefore vitamin E should be added at a minimum of 20 mg/kg. Thiamine (vitamin B1) may be necessary to prevent polioencephalomalacia (brain swelling). Consult your veterinarian. Cobalt deficiency can lead to B12 deficiency. Cobalt should be incorporated in the vitamin/mineral premix if feed is grown in a cobalt-deficient area. Animals with a diagnosed deficiency can be treated with vitamin B12. Achieving even distribution of vitamins by directly adding vitamin requirements to the ration is very difficult, because of the very small quantities involved. Commercial premixes that contain the desired variety and proportion of vitamins are available and make an even distribution more achievable. Guides to nutrient drenches and injections and to vitamin and mineral premixes were published in ALFA Lotfeeding in June 1997. Various substances can be added to the ration to improve feed conversion efficiency or daily weight gain. As a general recommendation, make sure that adequate animal performance is obtained from the basic ration before including additives; they can mask feed or management problems which could otherwise be more readily noticed and rectified. A ‘feed additive’ is generally defined as a feed ingredient of a non-nutritive nature that will stimulate growth or other types of performance, improve the efficiency of feed use, or benefit in some way the health or metabolism of the animal. Rumen modifiers and in-feed antimicrobialsCertain antimicrobial agents have been used as feed additives. These are not HGPs. Antimicrobials are used in feedlots to improve animal performance in terms of growth rate or feed conversion efficiency or both. Table 7. In-feed antimicrobial products currently registered for beef cattle and commercially available in Australia (November 1997). These are not HGPs.
| Active ingredient | Trade name | Manufacturer/distributor | Withholding
period |
| Oleandomycin | Keymix Calf Weanaid (calves only) | International Animal Health | Nil |
| Avoparcin | Avotan | Cyanamid Websters | Nil |
| Flavophospholipol | Flavomycin | Hoechst Animal Health | Nil |
| Lasalocid | Bovatec, various premixes | Roche Products P/L | Nil |
| Monensin | Rumensin, various premixes | Elanco Animal Health | Nil |
| Narasin | Naravin | Elanco Animal Health | Nil |
| Virginiamycin | Eskalin products | Pfizer Animal Health | Nil |
| Salinomycin | Posistac | Pfizer Animal Health | Nil |
The use of antimicrobial feed additive growth promoters, notably the ionophores (e.g. lasalocid, monensin, salinomycin), has resulted in liveweight gains of about 5% and improvement in feed conversion efficiency of 3–4%. Research organisations and industry are investigating other substances for use as growth promotants in beef cattle. New products may become available following clearance and registration. Sodium bentonite has been used successfully in the past. It acts as a buffer against grain sickness (acidosis) particularly during the build-up phase, when it should be fed at 2% of the ration. However, in the late 1990s, a number of commercial alternatives have become available, including virginiamycin.
Virginiamycin (Eskalin®) When added to the feed, this product can prevent the build-up of lactic acid in the rumen and hence grain poisoning. It has been found to reduce grain poisoning when mixed effectively into the ration. This is a new product, which has only recently become commercially available in Australia. Initial observations reinforce the need for thorough mixing. Virginiamycin is an antimicrobial and it is important that the manufacturer’s recommendations are strictly followed.
Proprietary mineral and vitamin premixes or concentratesIn the past many small feedlotters have sourced a variety of micro-ingredients and mixed them into a premix or concentrate, which is added to the ration at a rate of 1.5–4%. Today there are many proprietary premixes, concentrates or preparations available in a variety of forms, including pellets and molasses-based mixes and suspensions. Besides saving trouble, a commercial premix or concentrate may be a more reliable preparation to ensure each animal receives its daily requirements. A vitamin–mineral premix for domestic trade cattle should cover all but the most extreme situations. It should supply the following to the diet:
| Calcium | 4.0 g/kg |
| Potassium | 1.2 g/kg |
| Sodium | 0.8 g/kg |
| Sulfur | 0.8 g/kg |
| Copper | 4.7 mg/kg |
| Cobalt | 0.08 mg/kg |
| Selenium | 0.03 mg/kg |
| Zinc | 10 mg/kg |
| Vitamin A | 1000–1500 µg/kg |
| Vitamin E | 20–50 mg/kg |
Conversion factors
| Vitamin A | 1 mg = 3.3 IU |
| Vitamin E | 1 mg = 1.5 IU |
There are a large number of commercial preparations available, at varying prices (e.g. Rumevite®, Feedlot 80®, Eskape®, Beef Power®). Before selecting a premix, work out what ingredients you need for your operation and make sure they’re available. What other ingredients are included? Do you need them? Proprietary premixes generally incorporate salt, calcium, phosphorus, sulfur, cobalt, copper and magnesium, and may also contain urea, rumen modifiers, sodium bentonite and assorted vitamins. Check whether virginiamycin or other rumen modifiers are included.
This document forms part of the publication Opportunity lotfeeding of beef cattle, a NSW Agriculture Feedlot Services publication, which is available for sale in print form from NSW Agriculture.
The information contained in this web page is based on knowledge and understanding at the time of writing (6 January 2000). However, because of advances in knowledge, users are reminded of the need to ensure that information upon which they rely is up to date and to check currency of the information with the appropriate officer of New South Wales Department of Agriculture or the user’s independent adviser. © NSW Agriculture 2002 |