Between 8% and 18% of bulls on farms are either infertile or sub-fertile, and where a bull is solely relied on to get cows in calf, these problem animals can have a significant negative impact on margins within a farm business.
It is perhaps the area of greatest vulnerability on a suckler farm given that the output from a herd of cows is reliant on perhaps one or two animals.
According to Brian Kennedy, the company veterinarian at AI Services, it often takes up to three months for a farmer to realise there is an issue with a bull, and by this stage the damage has been done. That is particularly the case with a sub-fertile animal that has put some cows in-calf, but not them all.
Speaking at a recent CAFRE Business Development Group (BDG) event on the farm of Declan Rafferty, Pomeroy, Brian advised farmers to keep records and watch carefully all bulls turned out to cows, even those that have performed well in the previous year.
“Write down the first few cows in heat and watch for them coming back three weeks later – if a lot of cows are in heat again, get the bull tested. An infertile or sub-fertile bull is a proper sickener,” he said.
The bull must be able to follow and mount cows, so it is important he is sound on his feet.
Lameness (even a relatively mild case) can have a negative impact on the quality of the sperm produced, potentially leaving the animal infertile. In addition, back stress can cause pain when mounting cows, so it might be necessary to take the bull away for a week to 10 days to allow him to rest.
Avoid
When buying a bull, avoid an animal with either sickle hocks or posty (straight) legs as “they never last” said Brian.
He also maintained that the best way to routinely trim a bulls’ feet is to use a roll-over crush.
Watch out when buying a bull
Brian Kennedy is a fan of buying bulls in private sales from pedigree breeders, describing it as a “win” for both parties as the bull does not need to be fed heavily before a sale.
Assuming an 800kg bull can eat up to 2% of its bodyweight in concentrate feed, some animals could be consuming as much as 16kg of feed ahead of an auction. “Pedigree breeders have to feed heavily – you won’t bid unless it is stuffed to the gills,” said Brian.
He warned this level of feeding brings with it the risk of sub-clinical acidosis where excessive amounts of rapidly fermentable carbohydrates leads to periods of low pH in the rumen. “Any dairy farmer will tell you, an animal with sub clinical acidosis will have soft feet and bad joints,” he said.
He maintained that overfat bulls aren’t as interested in working and tend to fall off cows as they are “not as sharp on their feet”.
A fat bull will also have lower sperm quality. Sperm develops in the testes which are outside the main body cavity in the scrotum. For normal sperm formation, the testes should be 2-6°C below core body temperature, and this is regulated by muscle in the wall of the scrotum. In an overfat bull, fat deposits in the neck of the scrotum interfere with this process, leading to lower fertility.
Straight to field
When a bull is bought at a pedigree sale, Brian said the animal “should not be fired straight out to the field” and it was important to gradually take the bull down from its pre-sale feeding regime over the course of two to three weeks.
In some fairly rare cases, where the bull is not managed correctly, he said it can lead to progressive testicular atrophy, brought on by the trauma of effectively being starved. Where this occurs, the testicles are permanently shrunk. “It can turn into a real row between the buyer and seller,” said Brian.
Warning
His only warning when considering a private sale is to check for the size of the scrotum (see Table 1). In pedigree sales, animals must pass a pre-sale inspection, so potentially there is a temptation to try to pass off an animal privately that wouldn’t meet the minimum requirement.
Brian told farmers not to think just because they have a small number of cows to serve, that a bull with a small scrotum will do the job. “If the bull isn’t the required size you tend to find the semen is useless,” he said.
Ideally, the larger the scrotum the better. “A bull with high values will also produce more fertile progeny. Bulls with big testicles will pass those traits on to females – your heifers and cows will be more fruitful and fertile all their lives,” he said.
EBVs
He is also an advocate of purchasing performance recorded bulls, pointing out that AI Services would not consider buying a bull without Estimated Breeding Values (EBV’s) and with those figures being in the “right ballpark” for various key traits.
Match cow numbers
to bull age
A young bull will have a smaller volume, and lower density of semen, so the rule of thumb is to let him out to no more cows or heifers than his age in months – for example, an 18-month old bull should be with no more than 18 cows and heifers.
“An overly keen young bull can be a problem – the bull empties himself into one cow, and then has nothing left for two days. If you can, let him mount twice and put out. With time, he will settle down,” advised Brian.
A mature bull should be able to settle in-calf up to 40 cows, although their natural instinct is to breed when they are least vulnerable to predators, so an old bull might only work at night, and you will only rarely see him actually serving cows. “Make sure the bull is not over-worked and maintain the animal in moderate condition,” suggested Brian.
Housing
At housing he said bulls should be able to see other stock as they are social animals, and should be kept in pens that are comfortable, while ensuring the animal gets some exercise.
A bull with a poor temperament should be culled, but in some cases these issues can be brought on by poor handling. A bull should be treated with respect, and handled calmly and confidently.
The right time
to breed with AI
Artificial insemination (AI) gives farmers access to superior genetics and bulls that can be used to breed replacements, and is an obvious way of avoiding issues with an infertile or sub-fertile animal.
“The right time to breed still stands – 5 to 20 hours after the first standing heat. It is still OK out to 30 hours, but the average is 15 hours,” confirmed Brian.
He said the freezing and thawing process ages sperm eight hours, which is why you have to delay breeding when compared to a bull.
Sexed semen
In the dairy world, the use of sexed semen has really taken off in the last three years, and he expects 80% of dairy semen sales to be sexed this year.
There is the potential in future that sexed semen could become more widely available to suckler herds, and when combined with synchronisation, it would allow farmers to breed an even batch of replacement heifers.
But with sexed semen of lower quality than the conventional alternative, it may be necessary to double AI. “With sexed semen, you don’t have a 15-hour window for insemination. Sexed semen is also not turning super cheap, super quickly,” suggested Brian.
Read more
When to step in to assist at calving time
Calving advice: 10 tips for calving the cow
Between 8% and 18% of bulls on farms are either infertile or sub-fertile, and where a bull is solely relied on to get cows in calf, these problem animals can have a significant negative impact on margins within a farm business.
It is perhaps the area of greatest vulnerability on a suckler farm given that the output from a herd of cows is reliant on perhaps one or two animals.
According to Brian Kennedy, the company veterinarian at AI Services, it often takes up to three months for a farmer to realise there is an issue with a bull, and by this stage the damage has been done. That is particularly the case with a sub-fertile animal that has put some cows in-calf, but not them all.
Speaking at a recent CAFRE Business Development Group (BDG) event on the farm of Declan Rafferty, Pomeroy, Brian advised farmers to keep records and watch carefully all bulls turned out to cows, even those that have performed well in the previous year.
“Write down the first few cows in heat and watch for them coming back three weeks later – if a lot of cows are in heat again, get the bull tested. An infertile or sub-fertile bull is a proper sickener,” he said.
The bull must be able to follow and mount cows, so it is important he is sound on his feet.
Lameness (even a relatively mild case) can have a negative impact on the quality of the sperm produced, potentially leaving the animal infertile. In addition, back stress can cause pain when mounting cows, so it might be necessary to take the bull away for a week to 10 days to allow him to rest.
Avoid
When buying a bull, avoid an animal with either sickle hocks or posty (straight) legs as “they never last” said Brian.
He also maintained that the best way to routinely trim a bulls’ feet is to use a roll-over crush.
Watch out when buying a bull
Brian Kennedy is a fan of buying bulls in private sales from pedigree breeders, describing it as a “win” for both parties as the bull does not need to be fed heavily before a sale.
Assuming an 800kg bull can eat up to 2% of its bodyweight in concentrate feed, some animals could be consuming as much as 16kg of feed ahead of an auction. “Pedigree breeders have to feed heavily – you won’t bid unless it is stuffed to the gills,” said Brian.
He warned this level of feeding brings with it the risk of sub-clinical acidosis where excessive amounts of rapidly fermentable carbohydrates leads to periods of low pH in the rumen. “Any dairy farmer will tell you, an animal with sub clinical acidosis will have soft feet and bad joints,” he said.
He maintained that overfat bulls aren’t as interested in working and tend to fall off cows as they are “not as sharp on their feet”.
A fat bull will also have lower sperm quality. Sperm develops in the testes which are outside the main body cavity in the scrotum. For normal sperm formation, the testes should be 2-6°C below core body temperature, and this is regulated by muscle in the wall of the scrotum. In an overfat bull, fat deposits in the neck of the scrotum interfere with this process, leading to lower fertility.
Straight to field
When a bull is bought at a pedigree sale, Brian said the animal “should not be fired straight out to the field” and it was important to gradually take the bull down from its pre-sale feeding regime over the course of two to three weeks.
In some fairly rare cases, where the bull is not managed correctly, he said it can lead to progressive testicular atrophy, brought on by the trauma of effectively being starved. Where this occurs, the testicles are permanently shrunk. “It can turn into a real row between the buyer and seller,” said Brian.
Warning
His only warning when considering a private sale is to check for the size of the scrotum (see Table 1). In pedigree sales, animals must pass a pre-sale inspection, so potentially there is a temptation to try to pass off an animal privately that wouldn’t meet the minimum requirement.
Brian told farmers not to think just because they have a small number of cows to serve, that a bull with a small scrotum will do the job. “If the bull isn’t the required size you tend to find the semen is useless,” he said.
Ideally, the larger the scrotum the better. “A bull with high values will also produce more fertile progeny. Bulls with big testicles will pass those traits on to females – your heifers and cows will be more fruitful and fertile all their lives,” he said.
EBVs
He is also an advocate of purchasing performance recorded bulls, pointing out that AI Services would not consider buying a bull without Estimated Breeding Values (EBV’s) and with those figures being in the “right ballpark” for various key traits.
Match cow numbers
to bull age
A young bull will have a smaller volume, and lower density of semen, so the rule of thumb is to let him out to no more cows or heifers than his age in months – for example, an 18-month old bull should be with no more than 18 cows and heifers.
“An overly keen young bull can be a problem – the bull empties himself into one cow, and then has nothing left for two days. If you can, let him mount twice and put out. With time, he will settle down,” advised Brian.
A mature bull should be able to settle in-calf up to 40 cows, although their natural instinct is to breed when they are least vulnerable to predators, so an old bull might only work at night, and you will only rarely see him actually serving cows. “Make sure the bull is not over-worked and maintain the animal in moderate condition,” suggested Brian.
Housing
At housing he said bulls should be able to see other stock as they are social animals, and should be kept in pens that are comfortable, while ensuring the animal gets some exercise.
A bull with a poor temperament should be culled, but in some cases these issues can be brought on by poor handling. A bull should be treated with respect, and handled calmly and confidently.
The right time
to breed with AI
Artificial insemination (AI) gives farmers access to superior genetics and bulls that can be used to breed replacements, and is an obvious way of avoiding issues with an infertile or sub-fertile animal.
“The right time to breed still stands – 5 to 20 hours after the first standing heat. It is still OK out to 30 hours, but the average is 15 hours,” confirmed Brian.
He said the freezing and thawing process ages sperm eight hours, which is why you have to delay breeding when compared to a bull.
Sexed semen
In the dairy world, the use of sexed semen has really taken off in the last three years, and he expects 80% of dairy semen sales to be sexed this year.
There is the potential in future that sexed semen could become more widely available to suckler herds, and when combined with synchronisation, it would allow farmers to breed an even batch of replacement heifers.
But with sexed semen of lower quality than the conventional alternative, it may be necessary to double AI. “With sexed semen, you don’t have a 15-hour window for insemination. Sexed semen is also not turning super cheap, super quickly,” suggested Brian.
Read more
When to step in to assist at calving time
Calving advice: 10 tips for calving the cow
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