FERTILITY FROM A RESEARCH PERSPECTIVE Published June 3 2014 in The Farming Independent
An International conference on cow fertility was held in Westport, Co. Mayo two weeks ago. It brought together 480 delegates from over 35 countries and all five continents. This is the first conference focused on the importance of cow fertility on the ultimate profitability of your business.
The conference was primarily organised by Professor Michael Diskin, Teagasc and Dr. Trudee1 Fair, U.C.D. in conjunction with BSAS. It was a credit to this team to organise such an event with excellent speakers from various disciplines related to cow fertility.
There were contrasting views on the requirements for TMR diets for the transition cow (three weeks pre calving through three weeks post calving). Teagasc trials showed no benefit in TMR diets to reproductive efficiency in cows producing ~5000 litres of milk in 305 days. This contrasted with the essential requirement for TMR diets which improve DMI and lessen the NEB of fresh cows to achieve high reproductive efficiency in the high productive cows.
Consensus did pertain that any stressor in the transition period would have a significant deleterious effect on subsequent reproductive performance. This is manifested in poor repair of the womb after calving. This facilitates the establishment of uterus infections and delays the onset of normal heat cycles. Cows which have their first heat cycle after the voluntary waiting period post calving will in turn have a poor pregnancy rate to the first service. This can be overcome by synchronizing the first heat using a PRID or CIDR device to induce a heat.
However, the primary objective has to be one of avoiding stressors in the transition period causing a cascade of events resulting in impaired reproductive performance. In practice this focus on transition management has to pertain now where harvesting of grass for silage will be the primary driver of transition management outcome next year.
Avoid chopping grass too short as this will reduce the amount of physically effective fibre. If ground conditions are poor, avoid cutting grass too tight as you will increase the amount of soil contaminated grass. This will increase the amount of potassium in the silage resulting in “dark silages” which are associated with severe womb infections early post calving.
Coming back to the transition cow, it was clearly highlighted that cows restricted before calving in energy intake to their requirements had a 10-day shorter calving interval than cows allowed to over-consume energy. This reflects the importance of managing body condition score during the dry cow period. It was also shown from Canadian research work that stressors resulting in fat mobilization pre calving can trigger events leading to womb infections post calving because of immune system depression. The message emanating from the various presentations highlighted that we need a better understanding of links between metabolism and inflammatory response to it to result in prevention of reproductive disease and its’ associated costs.
Heat detection was highlighted as a major obstacle to achieving optimal reproductive performance. Data from the US showed that ~20pc of cows are planned mated using heat synchronization programmes. In high production cows managed in confinement systems, the duration and intensity of heats is reduced which has resulted in increased use of synchronization programmes to breed cows.
Dr. Donagh Berry, Teagasc suggested that the OVsynch programmes for fixed time AI were creating infertility problems for the dairy herd of the future. In my opinion, he is correct as we are selecting progeny from cows which are subfertile. In a recently published paper it was clearly shown that the calving interval was significantly increased when using fixed time AI with OVsynch programmes when compared with automated heat detection using the MooMonitor.
Sexed Semen usage has increased globally with a 90pc accuracy and a pregnancy rate of 75 to 80pc of that achieved with conventional semen. Poor results with fresh sexed semen on trials in Ireland last year were associated with agglutination of the sperm with consequent impairment of their fertility. Resolving this problem will dramatically increase the commercial application of fresh sexed semen in seasonal calving herds.
Finally, Dr. Laurence Shalloo emphasized the economic importance of achieving a high six week calving rate, which was strongly associated with survivability, calving interval and AI usage. A 10pc improvement in the six week calving rate would be worth €8,220 for a 100 cow dairy herd in a grass based system.
Dr. Dan Ryan is a cow fertility expert and can be contacted at www.cowsdna.com
Article written by Dr. Dan Ryan in The Farming Independent June 3rd 2014.