This is a subscriber-only article
There were many factors listed by speakers at an event organised by Lakeland Dairies in Armagh last week that can affect herd fertility.
Cow health, genetics, body condition score, lameness, nutrition, heat detection, AI technique, bull fertility, record-keeping and farm building design were mentioned as factors that can affect submission rates, conception rates or both.
Improving fertility in dairy herds comes down to identifying what factors are causing problems at an individual farm level and then taking steps to address them.
Within the Dairylink Ireland programme, herd fertility has been a key focus for participating farmers. Selecting sires with high indices for fertility, managing body condition score and improving herd health are some of the steps taken by programme farmers.
But a key element comes down to making sometimes difficult decisions with cows that are slow to get back in calf, by either not breeding replacements from them or else culling them out of the system.
Condition
Speaking at last week’s event in Armagh, Dr Morgan Sheehy from Devenish Nutrition said that measuring body condition score throughout lactation and the dry period is key to evaluating the energy status of cows.
The main condition score targets are 2.75 at drying off, 3.0 at calving and 2.5 at breeding. Sheehy said that for heifers, higher targets should be used of 3.0 to 3.5 at calving and 2.75 at breeding.
He told farmers that cows in lower condition produce lower-quality eggs and overfat cows will always lose more weight in early lactation and will be harder to get in calf.
“Animals in the wrong condition do not make money on farms. They will have lower fertility and a higher replacement rate,” Sheehy said.
Managing minerals
The other part of his talk related to managing minerals in diets, which can have direct and indirect effects on fertility.
“The easiest time to sort a trace element problem is in the dry period. But remember you can have problems with excess too, so it’s not a case of ‘if one shovel is good, two is better’,” he said.
Sheehy recommended testing the mineral status of forages and water. He said that high potassium levels on many farms were leading to underlying subclinical milk fever problems and subsequent issues with retained placentas, mastitis and displaced abomasums.
Farmers were told that excess iron and molybdenum levels in diets affect a range of important minerals needed for fertility. The main one is copper, where a deficiency can lead to silent heats, irregular cycling and low conception rates.
Selecting sires on fertility index works
Presenting figures from the Greenmount dairy herd over a five-year period, Martin Mulholland from CAFRE said that the UK-based £PLI fertility index of bulls correlated to the subsequent calving interval of their daughters.
“Selecting high fertility sires does work. My message is to invest in it,” Mulholland told farmers at last week’s event.
Fertility sub index increase
He said that the overall herd £PLI at Greenmount has increased from 197 to 298 over the past five years and the fertility sub index has increased from 4.1 to 7.0 over the same period.
The autumn-calving herd has an average yield of 8,800 litres/cow and has had fertility issues in recent years.
“At the start of the breeding season, we had a calving interval of 390 days. If we get it to 385 days by the end of this season, I’d be happy with that,” he said.
Mulholland said that replacing cows that are not in calf is often the largest cost of infertility. He quoted an average dairy heifer-rearing cost of £1,500, plus around £300 lost from reduced milk yield in the first lactation. The only income to offset this £1,800 bill is the price of the cull cow.
Management strategy needed for disease prevention
An overall management programme is needed on dairy farms to prevent the range of infectious disease that affect fertility, Sarah Campbell from MSD Animal Health said at last week’s event.
Campbell told farmers to investigate the cause of abortions and scours so that adequate steps can be taken for potential treatment and future prevention.
“Aim to get a diagnosis. Don’t just say ‘it must be one of those things’,” she said.
Three common infectious diseases highlighted by Campbell that affect fertility were BVD, salmonella and leptospirosis.
She said that vaccinations should be used alongside other management tools, such as a biosecurity protocol and a quarantine period of at least four weeks for newly purchased livestock.
Campbell said that once a herd starts vaccinating for salmonella and lepto, there isn’t a stopping point, as both diseases are widespread in the national herd and environment.
She said BVD is the exception due to ongoing eradication programmes across Ireland.
However, she said farmers should keep vaccinating for a period after the last PI calf is culled, as there will be some sources of BVD from embryonic losses, abortions or transiently infected animals.
SHARING OPTIONS: