This is a subscriber-only article
Having healthy cows, in good body condition during early lactation, is crucial to improving fertility in dairy herds across NI.
That was the main message from an on-farm information day on improving herd fertility organised by animal breeding company, Genus on the farm owned by Alastair Thompson, near Artigarvan in Co Tyrone last week.
The event focused on the fact that cow fertility has become a major challenge for dairy farmers, with the average Holstein cow producing a lifetime yield of 27,000 litres, from less than three lactations.
Fertility problems have ultimately led to an increase in replacement rates on farm, which is a significant cost to the farm business.
Improving cow fertility relies on a combination of factors related to farm management and herd genetics. Changes in management will bring relatively quick benefits, while changes in genetics are much more long-term.
Breeding companies such as Genus now offer a wide range of services, including breeding programmes designed to improve heat detection and conception rates to artificial insemination (AI). Where protocols are correctly followed, there are significant gains for the farmer, especially in higher-yielding herds with year-round calving profiles.
Host farm
The event last week was hosted by Alastair Thompson. He runs a 600-cow dairy unit with a year-round calving pattern on a 600ac grassland unit.
The herd milk records annually with cows yielding approximately 9,000 litres per year at 4.2% butterfat and 3.4% protein.
A total of 2.25t of concentrate is fed per cow, with just over 4,000 litres coming from forage, which is significantly higher than the NI average of 2,500 litres per cow.
Although considerable investment has been made in providing new housing facilities, cows still have access to high-quality grazing from spring through to autumn.
Cows remain housed after calving and don’t go out until settled in-calf. They are offered high-quality forages when indoors.
The farm has been using the Genus Reproductive Management System (RMS) since 2008. Before then, cow fertility had been in decline as individual cow yields increased.
Since joining RMS, there have been significant improvements in herd fertility. Cow size has also gradually reduced during this period, to produce a well-balanced durable cow suited to intensive dairying.
Breeding
Under the RMS programme, breeding technicians monitor the herd daily for cows coming into heat, and also inseminate animals when ready.
Cows are bred to a team of three to four sires, with potential sires picked twice annually. Sexed semen is being used on heifers and selected cows, with the herd being one of two trial herds in NI for a new sexed semen programme.
All breeding replacements are selected from first-calved heifers, with lower-yielding cows served to beef sires.
Measuring reproductive performance on dairy farms
According to Genus veterinary technicians, to increase herd fertility, there needs to be an increase in herd submission rates inside the first 100 days after calving.
The higher the submission rate, the more cows will be served, which will hopefully lead to more cows settled in-calf.
Many herds have conception rates of 70% to 90% to each service, but this does not automatically mean a fertile herd, especially if cows are not being served within 100 days of calving.
Therefore, Genus recommend using pregnancy rate, which is a combination of submission and conception rate, to measure herd fertility.
Where there are 100 cows eligible to become pregnant in a 21-day period (for example, at least 50 days calved), if 40 come into heat (40% submission rate) and of these, 50% conceive, then the pregnancy rate is 20%.
An in-depth analysis of UK National Milk Records (NMR) statistics, suggests that the average pregnancy rates in herds is around 15% which means only 15 out of 100 cows are successfully bred in a three-week window.
For the herds in the RMS programme in NI, this figure increases to 20%. A rate of 23% puts a farm in the top 25% of dairy herds in NI. The bottom 25% are at a rate of 17%.
Served
According to Genus, fertile cows should be returning to heat and served by 80 to 100 days post-calving to maintain as close to a 365-day calving interval as possible.
Herds should be recording how many cows are served 80 days after calving, and how many cows exceed this timeframe.
Over a longer period, structured breeding programmes, and selecting herd sires for fertility traits, should help to reduce the number of cows exceeding 80 days to first service.
RMS programmes can be set-up for individual herds based on the herd management, herd health issues, previous fertility records and desired breeding goals.
Cows that are slow to show signs of heat will be inspected internally and put on to a veterinary programme to correct any issues.
Across RMS herds, approximately 20% of cows that do not show natural heats are synchronised to ensure they are bred by 100 days post-calving.
Cows are scanned around 35 days post-service and again at 65 days.
Any cow that is still not confirmed in calf at this point is synchronised again and inseminated 10 days later.
Main management factors affecting cow fertility
The three main factors that can affect cow fertility in a housed environment are air quality, body condition and cow comfort.
With high-yielding herds tending to house cows from calving until they are settled in-calf, it is important to provide clean air in sheds.
Stale air increases the transmission of air-borne pathogens and also increases cow body temperatures during the summer months.
Sheds should have adequate outlets for air to regulate temperature, which also helps to eliminate condensation accumulating on roofing materials.
This increases the risk of respiratory issues and mastitis related to damp cubicle beds. Both problems will act to reduce fertility.
Where cows will be bred indoors during the summer, heat stress can be an issue. Air temperatures should be recorded from the middle of cow groups to get an accurate reading.
When temperatures increase beyond 310C at 50% humidity, yields will reduce by an average of three litres/cow/day.
In terms of cow comfort, cows should be lying for an average of 12 hours daily. Every additional hour of lying time can increase milk yield by one litre and vice versa.
Maintaining cow body condition during the first 100 days after calving is crucial. This begins in the dry cow period with feeding geared towards correcting any issues with poor body condition.
Cows should be grouped based on their stage of lactation so that freshly calved animals and cows at peak yield are being fed to their energy requirement.
Where cows are rapidly losing condition, unless this is quickly corrected, cows will be slower to return to heat and conception rates will be lower.
Feeding space is often overlooked in early lactation. Where cows have varying body condition, additional feed space should be provided to allow more cows to feed at the same time, especially first-calved heifers and shy feeders.
SHARING OPTIONS: