A Summary of the Recent and Current Research that shows the Contrasting "Capacities" of the Modern Holstein-Friesian

作者：Pyman M F^*; Macmillan K L

来源：Cattle Practice, 2010, 18: 114-122.

• Holstein-Friesian
• milk production
• reproductive performance
• energy balance
• anoestrus

The use of Holstein-Friesian (HF) genetics in the last twenty years has led to a breed that is capable of much higher milk yields than other dairy breeds, loses considerable liveweight during lactation, and as a result has reduced fertility and survival, potentially suffering a greater incidence of health problems early in lactation. The capacity for high production in the HF results from the partitioning of significant amounts of ingested energy into milk production combined with the ability of high genetic merit cows to mobilise greater proportions of body reserves to meet energy gaps than cows of average genetic merit. The outcome is a loss of body condition which exacerbates the negative energy balance (NEB) of HF cows in early lactation leading to reduced fertility and increased health problems.
Reduced reproductive performance is generally expressed as postpartum anovulation associated with anoestrus and the loss of the pregnancy post conception. Although improving the energy intake of HF cows will increase milk production and the degree of NEB, the reproductive performance will not be affected.
Overcoming poor reproductive performance in the HF can be managed in low input pasture-based or confinement feeding systems by extending the lactation up to 22 months with a 24-month calving interval. The strategy potentially overcomes reproductive limitations utilising the high milk yield potential of higher genetic merit HF cows. Continuous lactation or a shortening of the dry period has also been hypothesised to be an effective means of reducing the metabolic changes that occur during the transition period. The subsequent reduction in negative energy balance and body condition loss can lead to an improvement in reproductive performance in the following lactation. A third approach has been to utilise HF genes in crossbreeding programs that have led to improved fertility and survival in crossbred cows that suffer less body condition loss, have improved feed conversion efficiency and greater profitability. The economic advantage comes from reduced replacement costs and more productive cows.

• 出版日期2010-10