Is Supplemental Feeding Feasible

Source: Saskatchewan Agriculture and Food

Large numbers of steers are being placed on grass this spring and summer before they are moved to feedlots for finishing. Some of the questions that usually get asked are: what rate of gain can be expected from such cattle? Will providing supplemental feed result in greater gains than grazing the forages alone?

Saskatchewan Agriculture and Food Livestock Development Specialist Bill Kowalenko has these answers:

“Two factors come into play when considering the rate of gain in cattle. First, livestock producers should be aware of the nutrient requirements for any given class of cattle at their stage of growth and development. The other important factor is to know the nutritional value of the forage at any given stage of growth. The rate of gain of the cattle can be predicted pretty accurately if one knows the nutritional content of the forage and the cattle’s requirements.”

Forage quality is highest in the plants’ early growth stage when energy, protein, and digestibility will be higher, and the fibre content will be lower.

“As plants mature, the protein and energy drop off and the digestibility also decreases, due to the increased fibre content. For example, crested wheatgrass at the early vegetative stage will have energy of 75 per cent total digestible nutrients (TDN) and a crude protein content of 21.5 per cent. At full bloom, the same grass will have an energy value of 61 per cent TDN and crude protein of 9.8 per cent. As the grass continues to mature, both the energy and protein will continue to drop. Smooth brome at the early vegetative stage has an energy of 73 per cent TDN and crude protein of 21.3 per cent, while at the mature stage of growth the energy will be 53 per cent TDN and crude protein of 6.0 per cent.”

Similarly, cattle require higher energy and protein levels in their daily diet when they are younger—and at lighter weights—than when they are older and at heavier weights.

“For example, steers weighing 400 lb. consuming forage with crude protein in the range of 13 per cent would be expected to gain 2.0 lb./day. If the crude protein in the forage being grazed was in the 8.0 per cent range, the expected gain by the same steer would be only 0.5 lb./day.”

Proper nutrition dictates that an animal’s growth or production can be no greater than that allowed by the most limiting of the essential nutrients, explains Kowalenko.

“If a nutrient is included in an animal’s diet at a level that does not meet its requirements, the ability of the animal to use the other nutrients is governed by the level of that limiting nutrient. The two most important nutrients required by growing cattle are energy and protein.

“To expect cattle in the 400 to 600 lb weight range to grow at 2.0 to 2.5 lb./day on a grass-based forage, one would need to maintain the forage in the early vegetative phase to provide the energy and protein that would support that level of performance. If a legume was included as part of the forage supply, gains of 2.5 lb./day or greater may be expected.”

Supplementing standing forage is advantageous where it can correct a nutritional deficiency that interferes with forage utilization by the animal.

“Protein supplementation is effective where forages contain less protein than the animals require. Even though there may be adequate amounts of energy in a forage supply, if the protein is deficient for the grazing animal’s diet, there will be a reduction in forage intake.

Correcting for low protein content in the diet will result in an increase in forage intake, digestibility and animal gain.

“A report by the Oklahoma Co-operative Extension Service, titled How to Estimate the Value of Supplementing Grazing Stocker Cattle, shows that ‘when forage is slightly deficient in protein, you can expect about 0.4 pounds of added weight gain from the first pound of high protein supplement fed. When protein is adequate, you can expect about 0.09 pound of added weight gain from each pound of supplemental energy feed added.”

“In their example, they indicate if you correct a minor protein deficiency, one pound of a protein supplement such as cottonseed meal (38 per cent crude protein) should increase gain about 0.4 pound per day,” explains Kowalenko. “If the protein level in the diet (forage or forage plus supplement) is adequate, the addition of one pound of corn will likely increase gain by 0.09 pound per day. Adding energy to the daily diet of grazing cattle will result in their substituting the supplement for the forage they consume.

“The nutritional quality of the forage, and the size and age of the cattle grazing it, will determine the level of performance that one can expect to achieve in grazing the forage resource,” Kowalenko concludes.

For more information, contact:

W. S. (Bill) Kowalenko
Livestock Development Specialist
SaskatchewanAgriculture and Food
(306) 867-5559