Feed efficiency in cattle can make or break profitability in the feeding sector, and affects environmental implications. The costs of buying a calf and the feed needed to finish it are the two largest variable expenses facing the beef cattle feeding sector. Feed costs are higher than ever because of poor growing conditions in major grain producing countries, because of the use of feed grains in ethanol production, and because of increasing competition of land for crop production versus urban development.
Growth promotants are among the many sophisticated tools used by feedlots and other producers to raise more beef, more rapidly, using less feed, while maintaining high standards of animal health, carcass quality and food safety. Growth promotants include ionophores, growth implants, and beta-agonists. A number of products within each category are approved for use by Health Canada’s Veterinary Drug Directorate.
Ionophores are antimicrobials delivered through cattle feed that improve nutrient availability to the animal. They can improve feed efficiency and weight gain, reduce methane production, reduce the incidence of bloat and acidosis, and prevent diseases like coccidiosis.
Ionophores improve feed efficiency by acting on the rumen microbes. Most rumen microbes convert the complex fiber and starch in forage and grain into simple molecules that can be absorbed into the bloodstream to provide energy and protein to the animal. Some rumen bacteria (known as methanogens) convert the dietary fiber and starch into methane gas. Methane contains energy, but it cannot be absorbed by the animal, so it is belched out and wasted. Ionophores improve feed efficiency and weight gain by selectively inhibiting methanogenic bacteria, and allow the beneficial rumen bacteria to make more feed energy available to the animal.
Hormonal growth implants
Other growth promotants impact how nutrients are used by the animal after the nutrients have been absorbed into the bloodstream. Growth implants, delivered through a pellet under the skin in the animal’s ear, enhance the reproductive hormones that occur naturally in the animal. In steers, implants replace some of the hormones that were removed when the animal was castrated.
Implants generally encourage protein deposition and discourage fat deposition. This improves both weight gain and feed conversion. Fat deposition requires more than twice as much feed energy as protein deposition does. In addition to this, muscle tissue contains around 70% water, while fat contains less than 25% water. This means that for every ten pounds of muscle gained, about three pounds comes from dry feed and seven pounds comes from water. This ratio is reversed for fat growth (roughly seven pounds from dry feed and three pounds from water). Aggressive implant regimes may negatively impact carcass quality (maturity, marbling score, tenderness, and possibly lean color), especially if used on the wrong types of cattle.