April 2016 Articles

Archives by Months

Growing Weaned Calves

Growing Weaned Calves Source: www.uaex.edu Growth Growing calves have the highest TDN and protein requirement, as a percentage of the diet, of any cattle in the beef herd. For this reason, growing calves should be fed separately from the rest of the herd. The nutritional requirements for the weaned calf are determined by the age of the calf and desired growth rate (average daily gain, or ADG). The desired growth rate should be determined based on the expected market or desired breeding date and cost of feed resources. Replacement heifers should be fed to achieve 65% of their mature body weight by breeding and 85% of their mature body weight by calving. Heifers should also calve in a body condition score 6. To establish a target rate of gain for breeding heifers, knowledge of age, weight and body size at weaning are essential. A gestation calendar (Julian calendar) is also helpful to calculate the number of days between dates. For example, a producer desires to start breeding replacement heifers on March 15. The heifers weigh 475 pounds at weaning on October 1 and have a frame score of 5.5, as determined from age and height at weaning. The projected mature weight using the previously described formula is 1,212 pounds, and the projected target breeding weight is 788 pounds (1,212 x 0.65). The heifers have 165 days (October 1 to March 15) to gain 313 pounds (788 - 475), which calculates to a gain of 1.9 pounds per day (313 ÷ 165). As weaned calves continue to reach a higher percentage of their mature body size, protein requirements decrease. This should be considered when developing calves over a long period. Adjusting the ration as calves grow and mature will help reduce feed costs since supplemental protein is usually more expensive than supplemental energy. Metabolic Modifiers Tabular values for growing cattle are often presented under the conditions of implanting and feeding ionophores such as Bovatec and Rumensin. These management practices elicit improvements in average daily gain and feed efficiency. If these practices are not being implemented with growing cattle, then most tabular rates of gain for a given diet composition will be over-estimated, and a diet that contains a higher percentage of crude protein and TDN may be required. Considerations for Stress Weaning, marketing and processing (branding, dehorning, castration) are stressful events in a calf’s life and negatively affect the amount of feed a calf will eat. Stress may result in a two- to four-week period before a calf completely resumes normal intake. Therefore, the reduced intake must be taken into account when developing supplements or rations for these cattle. First-Calf Heifers First-calf heifers are the second most nutritionally demanding cattle in the herd. In addition to still growing, they have undergone the stress of calving and are now producing milk. Therefore, when establishing the nutrient requirements for first-calf heifers, the information described for mature cows must be considered, plus there remains an additional requirement for growth. Mature Bulls Mature bulls have the lowest nutritional requirement of the herd; however, the maintenance requirement for bulls during a short breeding season (45 to 90 days) increases due to the additional amount of activity. Bulls must be in a good body condition going into the breeding season because oftentimes they will lose body condition during the breeding season. Most bulls will have sufficient time to regain body condition after removal from the herd. However, bulls being used in both spring and fall calving herds will generally require supplementation to regain body condition. Summary Many factors contribute to the nutritional requirements of the herd. Minor errors in identifying one of the factors would likely not influence the results of a supplemental feeding program to a large degree. However, under- or over-estimating multiple factors that describe the cow herd and stage of production may lead to inadequate performance or costly supplementation that would lead to excessive body condition gain. In addition, due to the variability in nutritional requirements by type of beef cattle (mature cow, growing heifer, first-calf heifer, etc.), cattle with similar nutrient requirements should be grouped and fed separately.