17 April 2024

Getting your cow back in calf – the key factors to consider

The Teagasc Future Beef team hosted a webinar recently, which focused on the challenge of ‘getting your cow back in calf’, Aisling Molloy summarises the key points in this article.

The average gestation length of a beef cow is 288 days. However, the average length of time before she starts cycling after calving is 55 days. If she has a typical 21-day cycle, this means that there are only two opportunities to breed her to maintain a 365-day calving interval.

The featured participants were Future Beef Programme farmers Aonghusa Fahy and John Dunne, who were joined by Prof. David Kenny, Head of the Teagasc Animal Bioscience Research Centre.

Aonghusa Fahy from Ardrahan, Co. Galway, outlined how he uses a vasectomised bull and the ‘MooHeat’ technology to help him with heat detection, particularly as he works full time off farm. This allows him to use AI to breed replacements, and he then uses a stock bull to mop up. Record keeping is crucial to him for getting cows back in calf.

John Dunne from Portarlington in Co. Offaly discussed the issues he has encountered with both infertile and sub-fertile bulls on his farm, which saw his suckler cow numbers drop from 90 to 50. He is now building the herd numbers back up by using a synchronisation protocol on his heifers and cows, and has started fertility testing stock bulls on the farm. 

Professor David Kenny has vast experience researching all areas of cow and bull fertility in the beef herd and discussed the biological reasons that can affect it, along with developments in sexed semen that is becoming more widely available as an option for beef farmers.

What affects conception rates in suckler cows?

According to Prof. David Kenny, fertility is multifactorial. It is affected by:

• Body condition score at calving
  • A cow needs to be in moderate to good condition to reduce the interval between when she calves and when she resumes cyclicity again. The more cows that are cycling earlier in the breeding season, the better the chance of conceiving in the first three weeks of breeding season.
• Stock bull
  • Assess his fertility prior to breeding season. Just because he was fertile last year, doesn’t mean he will be this year. Complete a full vet health check to include locomotion, limb quality and general health. He has a lot of work to do in the first six weeks of the breeding season and can lose up to 10% of his body weight.
• Heat detection is critical
  • Having the time and/or technology to detect heats is very important – you won’t get good results otherwise.
• Cow nutrition
  • They must be on a consistent diet and conception rates can decline by up to 50% due to fluctuations in this such as poor growth, bad weather or a grass shortage. Maintaining a steady supply of grass is key.
• Mineral deficiencies and reproductive diseases
  • These can contribute to issues but, in general, both are small factors from trial results carried out across the country.

Fertility issues

John began having breeding issues on his farm in 2018. He has had suckler cows for 35 years and always had good conception rates with stock bulls. This particular year, he purchased a stock bull and ran him with the heifers on an out farm for 12 weeks. At the end of the season when the heifers were scanned, none of these were in calf, which was a huge hit to his cow numbers.

Unfortunately, John also had a sub-fertile bull on the farm and stated that he caused more damage, as he appeared to be active and some cows were going in calf to him.  In response to all this, he increased the dairy calf enterprise on the farm to help financially, he has also made some changes in terms of his stock bull management, and by starting a synchronisation programme on the farm which is outlined below.

Stock bull management

Now when John buys a stock bull, he firstly quarantines him from the herd and gives him time to acclimatise to the farm. A health check and fertility test are carried out by his vet. The bull is turned out to grass when the weather is suitable and is left in with the cows two weeks after the synchronisation programme is complete.

A young bull will only run with 20 cows and a mature bull will run with up to 40 cows.

John has considered buying a replacement bull, but knows that he would have to be changed more regularly as his daughters would be coming along in the herd. You also have to buy a genetically superior bull which is expensive. The synchronisation programme is saving him buying an extra bull now, and also gives him access to the best genetics.

What affects a bull’s fertility?

Anything that can affect a bull’s general health can affect his fertility, according to Prof. David Kenny. Locomotion and limb health are important for him to track and mate cows. Anything that causes inflammation or a rising temperature in the body, such as a chill or infection, will also affect fertility. 

The survival and manufacture of sperm is very sensitive to heat and it takes 60 days for a new batch of sperm to reach the stage where it is capable of putting a cow in calf. If a bull is infertile it could be something that happened up to 2 months ago!

While hard to determine figures, it is estimated that 5% of bulls are fully infertile and up to 25% are sub fertile. David outlined how vigilance is absolutely critical to identify repeats and potential issues when using AI and having a stock bull.

Heat detection

A key theme of the webinar was the importance of heat detection during the breeding season. Aonghusa monitors cows and heifers regularly for signs of heat and scans 3-4 weeks pre-breeding.  He records heats in an app and it gives a notification that a cow/heifer is due on heat 19 days later.

A dairy-beef bull calf is bought in and reared on milk replacer every year on the farm. He is vasectomised in September at 250-300kg and housed with the weanlings over the first winter.

During the breeding season, Aonghusa fits a MooHeat collar on him which also helps him to identify when cows are on heat, particularly when he works full time off farm. Each cow is given a unique tag and when the bull is in contact with her during a heat, a notification text is sent to Aonghusa’s phone.

It cost approximately €1,000-1,500 for 50 tags, a collar and the annual subscription. The subscription costs €350/year thereafter. No Wi-Fi connection is needed for the technology, as it works off a GPS system. At the end of the breeding season, the bull runs with empty cows that are being fattened. He is then finished in September and not retained for the following year to avoid an issues with temperament arising.

Synchronisation

John finds it difficult to find time in the spring for heat detection due to his dairy beef and tillage enterprises, along with the spring herd calving. He started synchronising two years ago where he bought in commercial heifers and bred them to AI. Last year, he synchronised the heifers again, along with some cows. Conception rates were back last year to 50-60%, but he is back up to his target cow numbers of 85 calving this year.

From a labour perspective, he only has to get the cattle into the yard three times for their veterinary treatment and AI, and he plans the dates out in advance with his vet. It costs approximately €75/head including the AI straw, but he emphasises how good conception rates are required. At 50% conception rates it costs €150/calf on the ground, so he is aiming for 70% conception rates this year.

The recommended synchronisation programmes for heifers and cows are outlined below. Heifers should be cycling before using the protocol outlined.

Figure 1: Sychronisation protocol for heifers

Figure 2: Synchronisation protocol for beef cows

Sexed semen

With sexed semen becoming more widely available for beef farmers, Prof. David Kenny described the sexing process. The semen is passed through a laser and separates the male and female sperm based on a 3% difference in DNA content. It damages sperm and it’s more fragile as a result. It is placed in cows/heifers at a slightly later time, closer to ovulation, because it doesn’t have the same lifespan.

Synchronisation gives more control for doing timed AI, especially if relying on an AI technician. Conception rates are 10-20% lower with sexed semen versus conventional straws.

John is sticking with conventional AI straws at present and will focus on improving conception rates first. Aonghusa used it on two cows last year and one cow held in calf. He found that the timing was hard to get right if heifers/cows were bulling at night, as he didn’t know what time the standing heat was at. However, he plans to try it again this year.

Further information on using sexed semen in the beef herd can be found here

You can watch the webinar here.

For more information on the Future Beef Programme, click here.