Many dairy farmers aspire to having a tight autumn calving herd but for most in reality calving starts in the autumn and often extends for perhaps 4, 6 or even 8 months.
“Achieving and indeed maintaining a tight calving pattern in higher yielding herds can be difficult,” says Dr David Mackey, CAFRE Dairying Adviser, who manages Business Development Groups (BDGs) in the North West. Given the implications of higher input prices this year, dairy farmers will need to focus even more than ever on the cost of production this summer. This may involve considering culling cows through the summer to remove ‘passengers’ caused by infertility, chronic lameness or mastitis.
David adds that attendees at a recent BDG meeting held on the farm of Robert Alcorn and his father Harold at Drumsurn, outside Limavady, were impressed with the high level of cow performance and the excellent 376-day calving interval being achieved. In 2021 the dairy herd averaged 265 cows with milk sales of 9,300 litres per cow at 4.25% butterfat and 3.42% protein.
Cows are managed in two groups and milked three times a day through the winter with a low yielding group comprising mostly heifers along with low yielding cows and a high yielding group. After a period of lead feeding, cows are fed to yield in the parlour. Throughout 2021 they were fed an average of 3.4 tonnes of meal per cow equating to 1,724 litres of milk from forage with a milk solids yield of 715 kg/cow.
David explains that breeding commences on 15 December each year and cows start calving in the latter half of September. While the herd calving pattern has always been fairly tight, as seen in Chart 1, the Alcorn’s have made a determined effort to maintain this and tighten it further as the herd has grown. The steepness of the line in Chart 1 demonstrates how the calving pattern has tightened in recent years. By the end of September last year 76 out of 274 cows had calved, representing almost 30% of the herd. By the end of October, six weeks after commencement of calving, 175 cows (65% of the herd) had calved with 95% calved by the end of December and all calved by the end of February. According to this year’s scan results, 224 cows and heifers are due to calve by 31 October this year representing a further tightening in the calving pattern.
“The exceptional fertility of this high yielding autumn-calving herd is down to a combination of factors rather than any one factor in particular” says David. Due to the seasonal nature of the herd, heifers calve at the beginning of the calving season at 24 months of age. After calving, all cows get a pre-breeding scan by the vet from around 32 days to ensure that they are correct for breeding, with problem cows getting a follow-up check at around 70 days. Early identification and treatment of problem cows is key as Robert and Harold prefer to serve cows at a natural heat without too much hormonal intervention.
As Robert says: “We always aim to get more cows in calf early each year and we worked even harder in the first 6 weeks of the breeding season this year.”
To aid heat detection this year, Robert walked the cows for about half an hour each day to pick up cows suitable for insemination. This heat detection is backed up by using cow pedometers linked to their Pearson milking parlour. During this time 101 of the 128 eligible cows were served giving a submission rate of almost 80% and of these 61 became pregnant to first service which is a conception rate of 60%. The heifers are fitted with SCR SenseHub collars that relay heat activity information to the parlour computer and an app on Robert’s phone. All heifer inseminations are based entirely on the activity collars.
The herd is fully milk recorded but not pedigree registered. Cows arescored by Genus and their Genetic Mating Service (GMS) is used to pair cows with the most appropriate bull, with sires selected on Profitable Lifetime Index (£PLI), and where possible a Predicted Transmitting Ability (PTA) for milk of 500 or more, positive fat and protein %, fertility score of greater than 10 and negative SCC. The lowest yielding 20% of cows are bred to beef semen with four AI Holstein bulls used to serve the rest. Last winter these bulls were Appear, Gander, Captain and Charl, with the bulls with the higher PTAs for milk generally used on the lower yielding cows. Sexed semen is used on cows for the first four weeks of the breeding season and heifers for the first six weeks, with beef semen being used thereafter.
All services are conducted by DIY-AI meaning that there is a recorded date and sire for every service – there are no bulls on the farm. Fertility and health information is recorded on the UniformAgri software package linked to the parlour. This is used to monitor progress and generate reports for heat detection and scanning.
With rising input costs, David Mackey concludes that: “This year more than ever, pregnancy scanning of dairy cows is important to identify the passengers early so that choices can be made to either rebreed or cull early.”
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