Fats and oils are the most energy dense feedstuffs. Their chemical and physical properties can enhance ration quality and improve livestock performance in the major intensive livestock industries, where their supplemental use has increased in recent years. Supplemental fats and oils are commonly used in the USA cattle feedlot industry, and their use has been commonplace in major sectors of the Australian feedlot industry since at least the early 1970s. Feedgrade fats and oils are readily available in three forms: oilseeds, commodity fats and oils, and specialty fats. The commodity fats and oils, the subject of the study, include animal fats such as tallow or yellow grease, and blends of animal and vegetable fats. These are frequently available to the Australian feedlot industry at reasonable costs varying in relation to grade and location. Australia exports in the order of 65% of its commodity fats and oils, principally as the rendered end product tallow or grease, or, in a value added form.
The intensive livestock industries consume an estimated 94,000 tonnes of which the feedlot industry uses 34,000 tonnes. The oilseeds which include oils derived from seeds, are high in fat and commonly available at a reasonable cost. The specialty fats comprise fats treated to make them more ruminally inert. The treatments are expensive, but are claimed to enable their feeding at higher levels when the opportunities for feeding the usually more reasonably costed oilseeds and commodity fats and oils have been exhausted. Commodity fats and oils are included in high concentrate feedlot finishing rations to increase dietary energy and cattle nutrient energy intake. Their inclusion enhances average daily gains, increases feed use efficiency, and improves carcase characteristics. There are also associated benefits which contribute significantly to an improved general overall operational efficiency. The effectiveness with which fats and oils are used largely relates to their quality.
Their feeding value and acceptability can be generally described in terms of the following characteristics.
Purity fat proportion and composition as it might affect nutrient energy value; ?
Stability rancidity as it might affect livestock acceptability; ?
Contaminants as they might affect animal health and meat products; and ?
Consistency delivery to delivery, as it might affect livestock acceptability.
The utilisation of supplemental fats and oils in beef cattle diets is a dynamic function of:
level of supplementation, basal dietary fat levels and sources of fats;
interaction with other ingredients and nutrients;
interaction with the climatic environment;
quality characteristics; and
acceptability and/or palatability.
Supplemental fat and oil levels in high concentrate finishing rations are typically 2.0 to 6.0% of ration dry matter (DM). The principal inclusion determinant is considered to be the total dietary fat dry matter intake (DMI), taking into account the basal dietary fat levels and acknowledging the fat levels of all ration ingredients. Research has been unable to determine maximum or optimum tolerable total dietary fat levels although levels to 8.0% DM appear satisfactory. There is a decline in the marginal feeding value of supplemental fat as inclusion rates increase.
Research has demonstrated fats and oils of animal and/or vegetable origin to be satisfactory. Supplemental fat may interact with other ration ingredients or their nutrient properties. In particular it has been concluded when total dietary fat exceeds 5.0%, dietary calcium and magnesium should be not less than 0.9% and 0.3% respectively. In addition a diminished response to ionophores is indicated when supplemental fat is fed in high concentrate diets. This suggests a cost saving opportunity by their exclusion when supplemental fat exceeds possibly 4.0% DM. The judicious use of fats and oils when animals are either heat stressed during high environmental temperatures and humidity, or are experiencing reduced DMI due to a cold stress, can contribute to maintaining higher levels of animal performance. A quality control program is necessary to monitor the product at delivery.
Close attention should be paid to the fat and oil quality characteristics, and their maintenance during storage. Antioxidants need be added to all feed fats as appropriate to stabilise their condition, minimising the possibility of oxidation rancidity developing. The storage, receival and delivery infrastructure to handle fats and oils needs to be robust, simple and adequate with prime consideration given to preserving product quality. Whilst incorporating specific design features, its manufacture and installation is basically simple. There is no restriction on the use of animal fat in Australian stockfeeds.