| Phillip Lancaster, MS, PhD Ruminant nutritionist Beef Cattle Institute Kansas State University palancaster@vet.k-state.edu |
Knowledge of feed intake and growth are important information to estimate cattle body weight and make marketing decisions. Extensive research has evaluated the nutrient intake and growth of cattle post-weaning with the result of accurate nutrition models to predict feed intake and growth of cattle. However, cow-calf producers are hindered in their marketing decisions by the lack of knowledge of calf growth.
Nursing calves consume nutrients from primarily 2 sources: milk and forage. Sometimes creep feed can also be offered. Milk and forage have drastically different nutrient profiles: milk contains ~ 5 Mcal of metabolizable energy and 28% protein on dry basis and forage contains ~ 2 Mcal of metabolizable energy and 10% protein on dry basis. The nutrient requirements and intake of nursing calves is dynamic over the preweaning period (Figure 1) as the amount of nutrients consumed from milk and forage changes over time, the nutritive value of forage changes over time, and the nutrient requirements of the calf are changing over time.
Researchers at Kansas State University are working to develop a nutrition model to predict growth of nursing beef calves. The model estimates nutrient intake from milk based on the peak lactation of the dam, nutrient intake from forage based on forage digestibility and calf body weight, and nutrient requirements of the calf based on calf body weight. The model appears to accurately estimate calf forage intake and body weight in beef calves (Figure 2 and 3).
The period from 4 to 7 months of age (Figure 1) is often referred to as the nutrient gap where nutrient intake from milk in declining and nutrient intake from forage is increasing but the quality of forage is declining such that forage alone does not meet the nutrient requirements for adequate calf growth. Creep feeding can be used to fill this nutrient gap, but the profitability of creep feeding depends on the conversion of creep feed into additional calf body weight. The quality of forage affects the amount of additional weight calves will gain. Accurate estimates of milk and forage intake can allow one to better make decisions on whether creep feeding would be economically viable. Additionally, a prediction of what calves would weigh at weaning can support better marketing decisions. Thus availability of nutrition models to predict nursing calf nutrient intake and growth could be valuable tools for cow-calf operations and the nutritionists and veterinarians that consult with them.
