Nutritional Strategies for Replacement Dairy Heifers: Using High Concentrate Rations to Improve feed Efficiency and Reduce Manure Production

Raising dairy heifers from birth to calving has been found to comprise the second largest expense on the dairy farm towards the production of milk, while deriving no revenue until the onset of lactation (Heinrichs, 1993). Therefore, many experiments involving dairy heifers have focused on ways to minimize the costs associated with the growth period or decreasing the unproductive period of the animal’s life. Reducing the length of the growing period by decreasing age at first calving below recommendations (22 to 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 return-oninvestment, it has been demonstrated that increased prepubertal ADG has a negative impact on mammary development (Radcliff et al., 1997; Sejrsen et al., 1982) and first lactation milk yield (Lammers et al., 1998; Radcliff et al., 2000; Van Amburgh et al., 1998). In summarizing recent literature on the association between prepubertal ADG and first lactation milk production, total first lactation milk and protein yields were maximized when prepubertal ADG was around 800 g/d for Holstein heifers (Zanton and Heinrichs, 2005a). Many researchers, however, are looking for ways to allow for greater ADG while maintaining optimal levels of mammary development and milk production. To date many of the approaches have shown little progress, conflicting results, or impracticable recommendations to enable a producer to overcome the problems associated with accelerated prepubertal growth.