Dairy Cow Fertility Study

DairyNZ is leading a seven year programme of research with the aim of improving cow fertility and lifetime productivity. Inefficiencies in fertility and productivity are estimated to cost the dairy industry between $500m and $1 billion annually.  DairyNZ senior scientist Kevin Macdonald and Jeremy Bryant, executive manager at NZ Animal Evaluation are two of those involved in the multi-party study.

The cow fertility research programme is part of a partnership programme with matched co-funding from DairyNZ and the Ministry of Business, Innovation and Employment (MBIE).  Additional funding and resources are being provided by AgResearch, Fonterra, LIC and CRV Ambreed.  The study aims to improve dairy cow fertility by delivering cows that are genetically more fertile, as well looking at new management tools to take advantage of these better genetics.

The research involves DairyNZ along with other scientists from AgResearch’s Animal Reproduction team, science teams from University of Victoria-Wellington, University of Queensland, Cognosco (a division of Anexa Animal Health), New Zealand Animal Evaluation Ltd. and genetics research company AbacusBio.

The research programme aims to lift the six-week in-calf rate.  Cow fertility is fundamental to dairy farm productivity with the goal to get as many cows as possible in-calf in the first six weeks.

More cows in calf means more milk in the vat before Christmas, fewer replacements required, more flexibility when making culling decisions to improve herds and better returns overall for dairy farmers.

Setting up the research herd was a huge logistical exercise that involved collecting hundreds of calves from farms all over the North.

Carefully planned contract matings have produced two groups of heifers which have extreme differences in their fertility breeding values.  These heifers were born in August 2015, and they will form the ‘animal model research herd’. More than 2800 contract matings were required.

Contract cows were targeted from dairy herds in the Waikato, Bay of Plenty, Taranaki, Manawatu, and Hawkes Bay.  Calves were collected within two weeks of birth, in an effort to minimise the impact of different management conditions on-farm.

The heifers that make up the “animal model” are Friesian.  This is because the breed has the biggest diversity in the fertility trait, as well as being the largest population of any dairy breed in NZ.

All calves were reared together at a facility in the North Island.  A ‘low’ vs ‘high’ fertility herd has been established through carefully selected contract matings in spring 2014.

Breeding values for the two herds are similar for all traits except fertility.  Fertility is incorporated into Breeding Worth (BW), and so the low fertility heifers also have a lower average BW.

The animal model research herd will be used to help to answer industry questions around cow fertility, including:

• How accurate is the current fertility breeding value?
• What new traits (phenotypes) can we measure and/or use to help us predict fertility?
• What underlying physiology is driving differences in fertility?

It is anticipated that increased understanding of the fertility trait will lead to better management on-farm, as well as enhanced genetic selection.  Better fertility in the national herd will directly impact cow health and longevity, delivering high economic returns, as well as improving positive public perception of the dairy industry.

In 2016 the programme is now in its third year, with three more years to run.  By 2019 it will see the heifers through their early growing and maturation, and into their first (2017-18) and second (2018-19) lactation.

The research herd will help to unravel the underlying biology that differentiates genetically fertile cows from infertile cows.

The fertility programme’s biggest challenge is reducing the apparent 30 percent of conceptions occurring in the first 35 days after insemination that are not sustained as a pregnancy.

The programme also aims to increase the power to select for improved fertility genotypes through use of novel phenotypes (new ways to measure fertility for selection purposes), improved recording and enhanced statistical analysis models.

The animal model will be used to help to answer:

• Does the current Fertility BV capture observed differences
• What new (other) measures (phenotypes/traits) will increase genetic fertility
• What is the underlying physiology driving the difference in fertility

Each animal will be monitored and tests performed throughout growth, puberty, mating, calving and first and second lactation to determine what impact the following measures have on the heritability of the fertility breeding value.

The heifers are all fitted with activity monitor collars.   Movement information from these collars will enable DairyNZ staff to monitor the animals 24 -7.   Information gathered this way includes indicating when the animals are in heat.

Other measurements/monitoring includes –

Puberty: Heifers must reach puberty to get in calf without the need for intervention. Knowing how many of the heifers reach puberty before mating starts will affect whether these heifers calf early or much later.

Oestrus: Heifers and cows that have a strong oestrus make it easier to detect heats; if this is possible through breeding, detecting cows on heat could become easier.

Consistent reproductive cycles: Irregularities in the reproductive cycles are the result of stressors. Cows that have many more irregularities are more likely to be the animals that get in calf late in the season or end up not in calf at the end of mating.

Submission, conception, and pregnancy rates: The Fertility Breeding Value includes whether lactating cows are submitted for mating and whether they calf in the first six week of calving. We expect this to be true for heifers, with the High Fertility heifers mated and calving earlier. This result will support whether heifer data has value in breeding for fertility.

Pregnancy loss: Heifers where pregnancies are lost will reset the reproductive cycle, and will result in the animal calving later or not at all. Whether there is a difference in pregnancy loss in the High and Low Fertility heifers is what we want to find out.

Detailed measures: The future will include additional detailed measures; from the hormones through to understanding, what makes a ‘good egg’ and what makes the embryo grow are the types of measures that are on the cards. 

Results from an intensive two-year study involving nearly 1,900 dairy cows indicate that embryonic losses after the first week are much less significant.  These results contradict internationally accepted wisdom that maternal recognition of pregnancy beginning the third week is the major risk period.

In-depth analyses of industry datasets have established that about 14% of cows are prematurely removed from the national dairying herd each year due to on-farm deaths and culling for non-productive reasons.

Ultimately this programme will allow genetic selection to become more targeted, and the rate of genetic gain in the fertility trait to increase.