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Energy and Protein Supplementation on Early Season Pastures

Photo credit: Barry Yaremcio

Forage quality decreases with maturity. Soil fertility, temperature, moisture availability, and plant type present in the stand all influence quality. With low soil fertility and dry conditions, the amount of nutrients available to the plants is limited. This reduces plant growth and quality. Knowing what to supplement can be a challenge.


Young immature plants contain the highest quality. At the five-leaf stage, tame grasses and legumes can range from 18 to 24% protein on a dry matter basis (DM). More than adequate for a lactating cow or backgrounding calves. Stands that contain legumes have a higher protein content than straight grasses. Differences can be three to five points or higher.


Acid detergent fibre (ADF) is an indicator of maturity. It is used as part of the equation to determine energy content (TDN). Prior to heading, ADF in the plant is low. As ADF increases, energy content decreases. Pre-heading energy levels are more than sufficient to meet requirements. Fibre levels can increase by 2 to 3% per week which reduces TDN. The reduction in energy is continual as the plant matures.


Weather impacts the rate of decline for quality. In hot dry years, forages mature 2 to 3 weeks earlier than normal. Plants are shorter and have fewer and smaller leaves which reduces quality. Rapid maturity is a mechanism that plants use to set seed and finish their growth cycle. Cutting hay or scheduling grazing by calendar date is not advised in these conditions. To maintain quality, implementing a rotational grazing to keep growth in the vegetative stage.


In most situations, early season forage quantity is adequate. There is no need to provide supplemental protein and energy to cows, backgrounding, or yearling animals. Providing a creep to suckling calves should be considered because their nutrient requirements are higher than for lactating cows or backgrounders.


Taking early season forage clippings is a good way to evaluate forage quality and ensure that adequate protein and energy is available for grazing animals. Sub optimal nutrition can reduce conception rates in females and reduce growth rate in calves.


For additional information for protein and energy requirements for cattle on pasture, contact Barry at 403-741-6032 or


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