Calving and Calf Management
The aim of successful calf rearing is to produce a healthy calf which is capable of optimum performance throughout its life from birth through to finishing, reports Bernadette Earley, Animal & Grassland Research and Innovation Centre, Teagasc.
Vitamin E is a naturally occurring fat soluble vitamin that was discovered in 1922. The term vitamin E encompasses several closely related compounds; the tocopherols and tocotrienols. Because of its chemical structure, vitamin E acts as a naturally occurring antioxidant and inhibits the spontaneous oxidation of highly unsaturated substances.
Raising dairy heifers from birth to calving comprises the second largest expense of milk production on the dairy farm—while deriving no revenue until the onset of lactation (Heinrichs, 1993). Therefore, many of the experiments involving dairy heifers have focused on ways to minimize costs associated with the growth period or to hasten onset of the productive period. Reducing the length of the growing period by decreasing the age at first calving below 22-24 months could overcome this lag between expenditure and revenue generation and reduce costs associated with the nonproductive period. This could be accomplished by increasing prepubertal average daily gain (ADG; Hoffman, 1997), which would subsequently result in a lower age at first breeding and presumably a lower age at first calving. Although this strategy would ultimately accelerate the return on investment, high rates of prepubertal ADG have a negative impact on mammary development (Radcliff et al., 1997; Sejrsen et al., 1982) and first lactation milk yield (Lammers et al., 1999; Radcliff et al., 2000; Van Amburgh et al., 1998). A summary of recent literature on the association between prepubertal ADG and first lactation milk production showed total first lactation milk and protein yield were maximized when prepubertal ADG was around 800 g/d for Holstein heifers (Zanton and Heinrichs, 2005).
