The impact of calf and youngstock development on dairy cow health, production and profitability

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Heifer calves represent the future of the dairy industry and it is imperative they are reared in a manner that maximises their full life time production in terms of yield and profitability (Brickell et al., 2009c). Dairy heifer rearing is a high cost ent erprise involving capital, land and labour. It represents one of the largest costs of milk production to the dairy farmer (Heinrichs, 1993). Consequently, evidence based heifer management is integral to the future success of Norwegian dairy farming if it is to remain profitable and sustainable. Currently, there is a paucity of data on the impact of different rearing regimes on calf and heifer development and dairy cow health, production and profitability. One of the major factors contributing to the cos t of rearing dairy heifers is age at first calving (Heinrichs, 1993). Approximately 35-40% of the Norwegian milking herd is replaced annually and replacement heifer rearing constitutes 25-30% of the running costs on a dairy farm. Historically the generic recommendation provided for Norwegian dairy farmers has been for heifers to calve aged 24 months. Recently it has been concluded that calving before 24 months maximises heifer lifetime economic performance (Ettema and Santos, 2004). Despite this the a verage age at first calving in Norway is 26 months. There are clear management benefits provided by reducing age at first calving, these include; reduced overall feed costs, lower overhead costs and reduced space requirements (Heinrichs, 1993). Age at fi rst calving can be manipulated by altering growth rates (Van Amburgh et al., 1998). One study showed that a reduction in age at first calving from 25 to 21 months would reduce heifer replacement costs by 18% (Tozer and Heinrichs, 2001). However, these c alculations did not consider changes in reproduction, lactation, and survivability of primiparous cows when calving at different ages.