Local trials have demonstrated early embryonic loss is the major cause of empty cows, being a financial drain on farming businesses, through higher replacement costs and lost production. The forecast intense El Niño may lead to higher than usual empty rates this year, if farmers do not ensure they provide sufficient high quality feed during early pregnancy.
Fertilised eggs (embryos) signal their presence by producing enough of a specific pregnancy protein (Interferon-T), 14-16 days after fertilisation. This prevents regression of the corpus luteum, formed from the ovarian follicle, as it produces the hormone progesterone necessary for maintaining pregnancy.
Early embryonic loss may be due to issues that occurred during the transition period around calving, resulting in small follicles producing small oocytes (eggs) unable to produce enough interferon-T.
Attachment of the embryo to the uterine wall occurs 19-22 days after fertilisation, followed by implantation and development of the placenta. Any stress during this stage may result in reabsorption of the embryo resulting in termination of pregnancy.
Any stress during the foetal stage of pregnancy (first 6 weeks) may result in empty cows, so it is important to ensure no major changes in feeding and management regimes during the 1st 100 days of lactation.
Nutritional stress, about now, is usually associated with inadequate availability and/or quality of pastures or crops, which is likely to be exacerbated by this year’s El Niño, due to dry conditions in the east and wet conditions in the west. This has coincided with low milk payouts, making it more difficult to justify buying in supplementary feeds to maintain nutrient intakes.
It is important to conserve as much home grown forage as possible, and use a good silage inoculant. It may still be necessary to purchase supplementary feeds, particularly during the high risk pregnancy period, otherwise there may be longer term losses associated with higher replacement costs, and loss of milk production next season, when milk prices are expected to start to recover.
Minerals and vitamins play important roles in production and fertility, so these should not be ignored when evaluating cow requirements. More care is required to ensure appropriate intakes with changes in forage quality, feeding of crops, and use of supplements, as they may not provide the optimal balance of minerals. This can be assessed through feed testing and use of a suitable feed rationing program by experienced nutritional advisers.
As featured in NZ Dairy Farmer