To realise their full growth potential, lotfed or intensively finished animals require a balanced ration that supplies all their nutritional requirements. To maximise production an understanding of ruminant livestock feed requirements and feed nutritive value is important.
The nutritional requirements of cattle, sheep and goats reflect the requirements of their rumen microbes. These microbes break feed down into volatile fatty acids which provide energy for body function and growth. They also pass into the small intestine where they are absorbed and form the main source of protein.
Good livestock production relies on a healthy and stable population of rumen microbes. Feedlot and intensive finishing nutrition is as much about feeding rumen microbes as feeding the animal.
The population of microbes in the rumen includes fungi, bacteria and protozoa. All fulfilling a different function, from using starch through to breaking down fibre. These microbes thrive in different parts of the rumen including within a fibrous mat made up of dietary roughage. This mat and the resident microbes allow other important components of a feed ration, such as grain, to be fully utilised and for good animal health to be maintained.
Feedlot and intensive finishing rations are formulated to maximise the weight gain required to meet market specification, while maintaining good animal health. This is achieved by providing a ration with the highest energy content that can be safely fed while still supporting rumen microbes that rely on roughage. The components contributing to energy can be as much as 85% of the ration, with grain being the main component.
Animals are introduced to feedlot or intensive finishing rations gradually. This is done by feeding decreasing amounts of roughage and increasing amounts of grain over the initial 15–20 days. This allows the microbe levels in the rumen to adjust gradually and minimises the risk of adverse responses, such as rumen acidosis, which can occur when ruminants are fed too much grain and too little roughage.
The fundamental components of a feedlot or intensive finishing ration are protein, energy, roughage and minerals. These are usually fed as a total mixed ration several times per day and a good supply of water is vital.
The protein in the ration is usually supplied as a protein meal and may be supplemented with non-protein nitrogen. Rather than feeding the animal, these inputs do more to feed the microbes which in turn pass from the rumen to the small intestine where they are absorbed and make up more than 70% of dietary protein.
Ration energy allows rumen microbes to grow, multiply and provide energy to the animal. Energy is typically supplied as or derived from:
- cereal grains (processed in some way to improve digestibility)
- by-products (such as citrus pulp and whole cotton seed).
Roughage or fibre is important to maintaining rumen microbial balance, especially when high-energy rations are being fed. Roughage is usually provided as hay in a total mixed ration and it’s advisable that individual particle lengths be at least 5cm long.
A range of minerals are important to maintain good rumen function and also animal health and welfare. Minerals such as calcium, phosphorus, magnesium and sulphur are included in the ration.
Rumen buffers can be added to a ration mix to improve rumen function. Sodium bicarbonate acts to neutralise acid and reduce the incidence of acidosis when feeding high grain diets. Feeding bentonite is thought to increase the flow of microbial (protozoal) protein from the rumen to the intestines, leading to increased production.
Rumen modifiers such as monensin, tylosin, virginiamycin, bambermycin and lasalocid may be included in a ration to positively influence the microbial balance in the rumen and achieve production benefits.
Hormone growth promotants (HGPs)
HGPs are based on naturally occurring male or female growth hormones. They stimulate growth and improve feed conversion in cattle to above normal production levels. These come in the form of implants which have an effective period that is usually 100 or 200 days, depending on the product used.
Once an implant has been applied, it remains with the animal permanently and can be detected beneath the skin, even after the hormone has been completely depleted. The use of HGPs must be declared on the Livestock Production Assurance National Vendor Declaration and Waybill (LPA NVD/Waybill).
Growth promotants can affect eating quality, however, these effects can be managed using various Meat Standards Australia (MSA) pathways such as ageing and tenderstretching. HGP treated cattle are eligible for MSA.
The use of HGPs in the feedlot environment will depend upon market specifications.
Nutritional deficiencies are rare where well-planned rations are fed during lot feeding and intensive finishing, particularly in short fed situations. Rations should consist of sufficient protein, energy, roughage and minerals to maintain rumen function and support livestock growth to meet market specifications.
Minerals of particular importance to livestock growth are calcium and phosphorus. Both may be supplied as individual components of a total mixed ration.
Livestock health should be monitored daily and any animal health issues thought to be linked to nutrition should be brought to the attention of the feedlot nutritionist or veterinarian.
Withholding periods and export slaughter intervals
Feedlot operators and intensive finishers must ensure that:
- all withholding periods (WHP) and export slaughter intervals (ESI) are observed for the chemical treatments they use on their livestock
- the feedstuffs they use are free from all residues.
All commodity feedstuffs bought in should be accompanied by a fully completed Commodity Vendor Declaration (CVD), Fodder Vendor Declaration or By-product Vendor Declaration.