Declining reproductive efficiency in the country's dairy herds is being caused by a combination of genetic, physiological and management factors, says an American scientist, Matthew Lucy.
Herd improvement records from the US showed reproductive decline in dairy cows began there in the mid-1980s, and similar problems were studied in Ireland, Britain,
and Australia.
Most farmers tended to automatically link the continuing decline in fertility to increases in milk production, but many other equally important factors might be involved, said Dr Lucy.
A molecular endocrinologist at the University of Missouri, Dr Lucy has been researching the molecular biology of reproductive processes that control the oestrous cycle in cattle.
Much of his research has focused on the role that growth hormones and their "receptors" play in the uterus.
But Dr Lucy has also studied the insulin-like growth factors (IGFs) and the IGF binding proteins released in response to growth hormones to stimulate the ovary and uterus.
His theory was that if IGFs control reproduction, it might be possible to increase embryo survival and litter size in farm animals by varying the energy content of cows' diets.
The efficiency of reproduction could be boosted by managing nutrition to control IGF secretion.
- NZPA
