Feed represents a major cost item in any production facility. The feeding program and type of feed used must be an important consideration. Rations that are not correctly formulated will quickly impact on the feed economics of this short growing period. Average daily gain (ADG) and feed efficiency (FE) ratio are key factors in profit realization. The FE achieved in any system of production can be affected by several factors:

Nutritive value of the diet

1) Maintenance:
Both ADG and FE are dependent on nutrient consumption in excess of maintenance. The greater the supply of nutrients above maintenance, the higher the nutrient allowance for gains, which in turn decreases the amount of feed required per unit of gain.

(greater intake →greater growth rate→ dilute cost of maintenance.)

Any factor that increases an animal’s maintenance requirements decreases the proportion of feed nutrients devoted to production and FE declines. Common factors that increase maintenance requirements are:

• Heat or cold stress
• Movement (walking)
• Extended standing (no comfortable place to lie down)

2) Feed Digestibility:
The lower the digestibility of a feed, the lower the feed efficiency. Protein in heat-damaged feeds can be indigestible. Milk replacers have a much higher digestibility than starter feeds.

3) Limiting nutrients:
If a nutrient is limiting to meet requirements for specific production parameters, increasing that nutrient can improve feed efficiency. However, too high a level of that same nutrient may also reduce feed efficiency. (Energy may be required by the animal to remove that excess).

High-energy diets promote superior FE. A protein deficiency will reduce the rate of ADG and also produce gain of high fat content, both reducing FE. Sub optimal intakes of a mineral or vitamin will also affect the efficiency of the animal.
When intakes are lower, during the start of any feeding phase, the dietary protein should be high to maximize the growth potential and reduce stress.

J.Dairy Sci 67: 2957-2963 Huber et al, 1984. Holstein calves on outdoor hutches. Increased feeding of milk produces greater gains, which in meat producing animals, is important in minimizing the time to target weight.

Slaughter weight
FCE deteriorates as slaughter weight increase. This is a reflection of the high-energy requirement for fat production, which increases, as the animal gets heavier.

Breed/Sex
Genetic differences can result in significant differences in efficiency of food utilization. Bulls and steers are leaner than heifers of the same weight.

Feed efficiency values can help indicate if animals are performing reasonably with a particular ration, management, or environment, or if these can be improved.

Andre Roy MSc.
Sally Charlton BSc. (Hons)
 April 2003