The Cattle Health and Welfare Group report (CHAWG, 2018) indicates a steady rise in the calving interval for the national herd from the year 2000 and then a fall from over 430 days to 405 days. Considerable anxiety was generated a decade or so ago over the possibility that cattle fertility was becoming a blight on the industry.
Pan Livestock Services Ltd monitored 500 milk-recorded herds (National Milk Records) for the past 13 years and showed that the calving interval has continued to reduce. In 2022, the top performing quartile of herds showed a 29-day improvement over the bottom quartile (412 days/384 days).
The lay of the land
Looking at the range of key performance indicators in the Pan study (Pan Livestock, n/a), it is interesting to see how the different parameters have changed over time. There are clearly aspects of fertility where veterinary surgeons are able to engage well with dairy clients to improve performance.
However, a paragraph in the report highlights some of the difficulties and realities for farmers and vets: “The combination of parameters relating to production, fertility and health emphasizes the dynamic nature of dairy production and the need for high standards across all areas of herd management. Many herds are excellent in one area of production, fertility or health but seldom in all.”
Discussions with cattle vets indicate that, nowadays, recording the calving interval is not a reliable indicator of herd performance
Discussions with cattle vets indicate that, nowadays, recording the calving interval is not a reliable indicator of herd performance. Instead, many herds are choosing to cull healthy performing cows in favour of introducing heifers. Thus, knowledge of the aims of the herd manager is key to understanding herd performance.
Individual herd assessment reports for clients build on herd analysis, and nowadays, vets have the ability to highlight reports with advisory comments where changes, for better or worse, are being demonstrated. A copy of a note from Andy Biggs (Tiverton) to a client shows yellow arrows, circles and short comments with indications for further discussion. These appear easy to follow, and many practices are considering how best to use data and sort appropriate guidance for farmers.
A comment from James Hanks that “we don’t need the computer to tell the farmer what to do” relates to the role of the vet to interpret data rather than the farmer being bombarded with information which can be easily misinterpreted. A further comment is that, as an industry, we must “avoid data simply being used to keep the milk buyer off the farmer’s back”.
Pregnancy and standing cow data
The National Disease Information Service (NADIS) has an animal health skills section that clearly indicates how to proceed with cow pregnancy. Insemination needs to take place before the cow releases the egg, and the sperm needs to be in the oviduct before the egg gets there. Therefore, insemination needs to occur during mid-oestrus. Ovulation occurs 24 to 32 hours after standing heat.
There is a warning that over the years, the intensity of standing heat has reduced from 70 percent of cows “standing” to 50 percent today. The duration of standing oestrus has also reduced from 15 to 5 hours. The Federation of UK Milk Marketing Boards (1984) indicated that there were 50,000 milk producers and an average herd size of 64 cows in 1984. Today, there are some 7,500 milk producers and an average herd size of 170 cows (Dairy UK).
It is not surprising that watching a herd of cows to note animals in standing heat has proved difficult, and heat detection has needed a considerable boost in technology. Chris Hudson highlights that “improvements in sensor tech continue to be a big driver for change”.
The Agricultural and Horticultural Development Board (AHDB) has established a strategic dairy farm network where herds are highlighted, and the farmers involved discuss aspects of herd management and performance. The costs of production across the network are indicated as 24 to 34ppl. Clearly, there are huge differences in the way herds are assessed, and the casual uptake of figures can be misleading.
One of the important criteria for understanding fertility performance is whether the farmer is managing the herd for block calving or all-year-round calving. The attraction of block calving, with major attention to serving cows and calving over a six-week period, is to strike a better work–life balance for the farmer.
One of the important criteria for understanding fertility performance is whether the farmer is managing the herd for block calving or all-year-round calving
It involves intense activity for the farmer at calving, with a carefully managed period of artificial insemination, proven semen quality, sexed semen and then 300 days of milk production, with great attention to energy levels during the dry period prior to the block of calving.
Performance levels of all fertility criteria are very different between all-year and block calving. Farmers Weekly indicates a conception rate variation of 35 to 60 percent and a pregnancy rate of 25 to 55 percent (Watts, 2018).
Annual fertility review
It is clear that successful fertility in the modern UK dairy herd is not being achieved by following a national plan. Thus, veterinary consultants are engaging in an annual fertility review. The idea is to use data to indicate what did and did not go well last year to set a management programme for the following year.
There is pressure from milk buyers to run a “clean” herd, and the use of prostaglandin and gonadotrophin-releasing hormone for planned breeding requires a careful forward plan. The National Bovine Data Centre includes genetic advances and the selection of bulls with better calving intervals, improved heat detection and genotyping of young stock in a list of current developments that are leading to better decision making at farm level.
In the 2022 review of milk recorded herds, James Hanks (Pan Livestock) indicates that one in four herds has more than 252 cows and one in four has fewer than 123 cows (Hanks and Kossaibati, 2023). The median age of cows at exit from the herd is six years, and the median productive life is 1,359 days, 152 days shorter than in 2010. The median conception rate is 38 percent, with a range from 32 to 45 percent; median heat detection is 41 percent, with one in four farms detecting less than 32 percent of service returns. The percentage of cows conceived by day 100 is 39 percent, 13 percent higher than in 2010.
The improvements recorded in somatic cell counts, fertility and productivity are considerable, but are not resulting in longer productive lives
The improvements recorded in somatic cell counts, fertility and productivity are considerable, but are not resulting in longer productive lives. Detailed analysis of individual herds is available from the NMR data but James cautions that the analysis should be considered to be a document that stimulates discussion between a veterinary advisor and a farmer.
The introduction of the profitable lifetime and fertility indexes may need to be carefully considered if the trend for a greater introduction of heifers, while maintaining overall herd size, continues. Economic changes are just one of the aspects that alters the interpretation of national data, as a performance guide, for the individual farmer and their veterinary surgeon.