Finding fertile ground for dairy cows
Since the 1990s there has been a decline in cow fertility which has in turn shortened the productive life of cows. ‘It’s now often less than 3 calvings per cow,’ says Filippo Biscarini, from the Institute of Agricultural Biology and Biotechnology of the National Council for Research (CNR-IBBA) in Milan/Lodi, Italy. Biscarini is coordinator of the recently completed four-year EU-funded FECUND project that has tried to explain why this has happened and how dairy cattle breeding and farming can reverse the decline. The decline in cow fertility, particularly in Holstein cattle, has led pregnancy rates after insemination to drop from 80 % 20 years ago to less than 40 % today. Poor fertility is now one of the main reasons for early culling. The FECUND consortium, with 13 partners from seven EU countries, sought to study this phenomenon in dairy cows by looking at the metabolic and genetic factors associated with high and low fertility potential. ‘Our starting hypotheses was that today’s high-producing cows divert most of their energy towards milk production, whilst neglecting other important physiological activities like reproduction, which has led to lower conception rates and intervals of more than 14 months between calvings,’ explains Biscarini. As well as a cow’s metabolic state, pre-determined genetic factors also play a role in its fertility. ‘To understand what is going on, we looked at two models, one based on metabolics - or energy use and input, and the second based on genetics,’ says Biscarini. FECUND focused on the early phases of reproduction from egg development to foetal implantation. They sampled from the animals reproductive organs, taken at different stages in the reproductive cycle. The consortium generated a large set of data on the animals’ genetic make-up and where and when specific genes were switched on and off, to fully understand how genetics could be influencing fertility. The biological samples came from commercial dairy cattle in different countries, from cattle with high and low estimated breeding values (the industry measure of their genetic potential for fertility), and from cows under the energy stress of early lactation as well as dry cows and younger animals before pregnancy. FECUND’s results have provided a better understanding of how lactation stress and genetics affect egg and embryo quality, for instance, how components of the fluid inside the follicles where eggs form influence the egg quality and its ability to develop. FECUND has used genetic data mined from their studies to find novel mutations related to fertility, and to predict carriers of desirable or undesired mutations, like the TUBD1 mutation, recently discovered, which is associated with embryo mortality and, consequently, reduced fertility. ‘The project has contributed with the generation of large datasets available to the community, a new toolbox and a better understanding of the problem,’ concludes Biscarini. This project and other work in the area is already paying dividends, he adds. ‘The concerted efforts from the scientific and breeding communities have been effective, and the declining trend in cow fertility has been stopped and in some cases reverted.’
Keywords
FECUND, dairy cattle, fertility, animal breeding, Holstein cattle, metabolics, milk production, estimated breeding values, TUBD1
