The simplest and probably the most effective way of getting maiden heifers in calf is to use stock bulls. No tail paint, no observations and provided all are well grown and that the bulls’ and heifers’ fertility is good, there will be a high in-calf rate after 10 weeks of mating, with 95% to 100% in calf, all going well.
What are the downsides of this? Firstly, daughters of stock bulls make bad cows. Compared with a proven AI bull, the reliability of a stock bull is low – about 30%. This means there is a 70% chance that his daughters will not produce what they are supposed to in terms of milk solids and fertility performance.
This is on top of the fact that, to begin with, stock bulls tend to have lower EBIs than AI bulls. As one of my farmer friends once said: “If a stock bull was that good, he’d be an AI bull.” Many people buying stock realise this and pay a premium price for AI-bred stock.
The other big problem with using bulls, especially young bulls, is that they have no calving proof, so there is a big risk that they could be hard-calving. This not only causes big problems at calving time, but it also makes it more difficult to get those cows that had the hard calving back in calf again. This risk is exacerbated by using bulls on maiden heifers.
Another issue with just using bulls to get heifers in-calf is the spreadout nature of the subsequent calving pattern.
While a high proportion of heifers will go in calf, calving tends to be more evenly spread out over a six- to 10-week period when compared with, say, an AI plus synchrony programme that condenses the majority of calvings into the first three weeks.
A shorter calving spread is better as it increases the six-week calving rate, thereby increasing milk production and allowing more time between calving and the next mating, which increases the chance of that heifer going in calf early in the next breeding season.
So, what can be done to use more AI in maiden heifers without drastically increasing the workload at this already busy time?
Andre Van Barneveld, breeding adviser for LIC
Ireland, explains his thoughts on breeding
maiden heifers.
Three weeks of AI
Andre said that there are three real options available for farmers looking to use more AI on maiden heifers.
The first is to carry out AI to observed heats for the first three weeks and then let out bulls to mop up repeats.
He said that this method can be very successful but it requires operator skill to identify which heifers are bulling and to AI them at the appropriate time.
Of course, heat-detection aids such as scratch cards, kamars and tail paint will assist in this but, nevertheless, a high level of skill and stockmanship is required for successful results.
“The best results using this method are where the heifers are kept on the milking platform and are regularly monitored, several times a day, and preferably by the same person,” says Andre.
He added that if managed correctly, close to 100% submission rate should be achieved and conception rates of 75% can be expected.
Synchrony using
prostaglandin
Monitoring heifers several times a day for three weeks takes considerable time. A widely used method of condensing the time spent observing heats is to use an injection of prostaglandin hormone (PG) to bring heifers into heat.
For PG to work, there must be a functional corpus luteum present on one of the ovaries. The corpus luteum is what is left of the follicle from the last cycle and is present from days six to 16 of the animal’s cycle. So, at any one time, provided that they are cycling, only about two-thirds of maiden heifers will respond to PG.
Some farmers will PG all their heifers and then AI to observe heats, which normally occurs 36 to 72 hours after the PG injection. Andre said that more heifers can be artificially inseminated where they are observed for seven to 10 days (without any PG) and then PG given to the heifers that have not been observed.
These are inseminated after they come into heat. Bulls are then introduced.
The advantages of this are that the observation period is reduced from 21 days to between 10 and 14 days and while submission rates will be high, the conception rate might be slightly lower than if no PG was used.
Nevertheless, this is a widely used method of artificially inseminating heifers. However, for it to be successful, heifers must be cycling. The best measure of this is weight; otherwise, the PG will be wasted. It costs about €6.40 per animal for the PG.
Synchrony using
progesterone
Another type of synchrony programme is to use progesterone. By using a CIDR or a PRID-based synchrony programme (CIDR and PRID are slow-release progesterone devices that are placed in the animal’s vagina), the mating period is condensed into an even shorter period as effectively all the heifers can be inseminated at the one time, which is ideal for heifers that are kept on an outside block. However, the downside of this is that it costs more per heifer.
Andre recommends the following CIDR programme:
Day one: Insert CIDRs 10 days prior to mating date.Day seven: Prostaglandin injection.Day eight: Remove CIDR at 9am.Day 10: AI all heifers from 12pm to 4pm.These next steps are optional, but will increase the proportion in calf to AI:
Day 22: CIDRs back in (this is 12 days after the first AI mating).Day 29: CIDRs back out and dispose, apply heat detection aids/tail-paint all heifers.Day 31: Mate on observation. Expect around 25% returns to mate.This programme will cost about €21 per heifer. Andre says reinserting the CIDRs is optional if you want to maximise the chances of the heifer going in calf to AI, but he says the CIDRs should only be reused for this purpose and not used in other animals.
Teagasc researcher Stephen Butler recommends using a slightly different protocol for fixed-time AI. He recommends farmers use one of two protocols:
Insert progesterone device: Five days later, give an injection of PG and remove the progesterone device. Seventy-two hours later, give an injection of GnRH and AI.Insert progesterone device and give injection of GnRH: Five days later, remove the progesterone device and give an injection of PG. Twenty-four hours later, give a second injection of PG. Forty-eight hours later, give an injection of GnRH and AI.Stephen says that the second protocol gives better conception rates, but requires two additional injections, plus the hassle of having to bring in the heifers another time.
GnRH is a hormone that times the release of an egg, making fixed time AI more successful but, again, this comes at an increased cost. Each shot of GnRH costs about €5.90.
However, Stephen does not recommend doing fixed-time AI without using GnRH as the timing of a heat (and hence ovulation) is too variable for a single-timed AI protocol. Bulls are then introduced after each protocol to pick up repeats. The method you choose depends on your own preference and what suits your system.
From a cost and efficiency perspective, artifically inseminating for seven days and using a PG hormone for those not served is probably the best option for most farmers.
The final point is that if you are going to the effort of using AI on heifers, you should only use the top EBI proven bulls. No genomic or test bulls should ever be used on heifers.
Breeding heifers to AI improves your herd and increases the value of replacements. Some farmers will artificially inseminate for three weeks and then let out stock bulls. Seven days of AI and PG for the remainder gives good results. CIDR programme increases cost but reduces the time spent observing.
The simplest and probably the most effective way of getting maiden heifers in calf is to use stock bulls. No tail paint, no observations and provided all are well grown and that the bulls’ and heifers’ fertility is good, there will be a high in-calf rate after 10 weeks of mating, with 95% to 100% in calf, all going well.
What are the downsides of this? Firstly, daughters of stock bulls make bad cows. Compared with a proven AI bull, the reliability of a stock bull is low – about 30%. This means there is a 70% chance that his daughters will not produce what they are supposed to in terms of milk solids and fertility performance.
This is on top of the fact that, to begin with, stock bulls tend to have lower EBIs than AI bulls. As one of my farmer friends once said: “If a stock bull was that good, he’d be an AI bull.” Many people buying stock realise this and pay a premium price for AI-bred stock.
The other big problem with using bulls, especially young bulls, is that they have no calving proof, so there is a big risk that they could be hard-calving. This not only causes big problems at calving time, but it also makes it more difficult to get those cows that had the hard calving back in calf again. This risk is exacerbated by using bulls on maiden heifers.
Another issue with just using bulls to get heifers in-calf is the spreadout nature of the subsequent calving pattern.
While a high proportion of heifers will go in calf, calving tends to be more evenly spread out over a six- to 10-week period when compared with, say, an AI plus synchrony programme that condenses the majority of calvings into the first three weeks.
A shorter calving spread is better as it increases the six-week calving rate, thereby increasing milk production and allowing more time between calving and the next mating, which increases the chance of that heifer going in calf early in the next breeding season.
So, what can be done to use more AI in maiden heifers without drastically increasing the workload at this already busy time?
Andre Van Barneveld, breeding adviser for LIC
Ireland, explains his thoughts on breeding
maiden heifers.
Three weeks of AI
Andre said that there are three real options available for farmers looking to use more AI on maiden heifers.
The first is to carry out AI to observed heats for the first three weeks and then let out bulls to mop up repeats.
He said that this method can be very successful but it requires operator skill to identify which heifers are bulling and to AI them at the appropriate time.
Of course, heat-detection aids such as scratch cards, kamars and tail paint will assist in this but, nevertheless, a high level of skill and stockmanship is required for successful results.
“The best results using this method are where the heifers are kept on the milking platform and are regularly monitored, several times a day, and preferably by the same person,” says Andre.
He added that if managed correctly, close to 100% submission rate should be achieved and conception rates of 75% can be expected.
Synchrony using
prostaglandin
Monitoring heifers several times a day for three weeks takes considerable time. A widely used method of condensing the time spent observing heats is to use an injection of prostaglandin hormone (PG) to bring heifers into heat.
For PG to work, there must be a functional corpus luteum present on one of the ovaries. The corpus luteum is what is left of the follicle from the last cycle and is present from days six to 16 of the animal’s cycle. So, at any one time, provided that they are cycling, only about two-thirds of maiden heifers will respond to PG.
Some farmers will PG all their heifers and then AI to observe heats, which normally occurs 36 to 72 hours after the PG injection. Andre said that more heifers can be artificially inseminated where they are observed for seven to 10 days (without any PG) and then PG given to the heifers that have not been observed.
These are inseminated after they come into heat. Bulls are then introduced.
The advantages of this are that the observation period is reduced from 21 days to between 10 and 14 days and while submission rates will be high, the conception rate might be slightly lower than if no PG was used.
Nevertheless, this is a widely used method of artificially inseminating heifers. However, for it to be successful, heifers must be cycling. The best measure of this is weight; otherwise, the PG will be wasted. It costs about €6.40 per animal for the PG.
Synchrony using
progesterone
Another type of synchrony programme is to use progesterone. By using a CIDR or a PRID-based synchrony programme (CIDR and PRID are slow-release progesterone devices that are placed in the animal’s vagina), the mating period is condensed into an even shorter period as effectively all the heifers can be inseminated at the one time, which is ideal for heifers that are kept on an outside block. However, the downside of this is that it costs more per heifer.
Andre recommends the following CIDR programme:
Day one: Insert CIDRs 10 days prior to mating date.Day seven: Prostaglandin injection.Day eight: Remove CIDR at 9am.Day 10: AI all heifers from 12pm to 4pm.These next steps are optional, but will increase the proportion in calf to AI:
Day 22: CIDRs back in (this is 12 days after the first AI mating).Day 29: CIDRs back out and dispose, apply heat detection aids/tail-paint all heifers.Day 31: Mate on observation. Expect around 25% returns to mate.This programme will cost about €21 per heifer. Andre says reinserting the CIDRs is optional if you want to maximise the chances of the heifer going in calf to AI, but he says the CIDRs should only be reused for this purpose and not used in other animals.
Teagasc researcher Stephen Butler recommends using a slightly different protocol for fixed-time AI. He recommends farmers use one of two protocols:
Insert progesterone device: Five days later, give an injection of PG and remove the progesterone device. Seventy-two hours later, give an injection of GnRH and AI.Insert progesterone device and give injection of GnRH: Five days later, remove the progesterone device and give an injection of PG. Twenty-four hours later, give a second injection of PG. Forty-eight hours later, give an injection of GnRH and AI.Stephen says that the second protocol gives better conception rates, but requires two additional injections, plus the hassle of having to bring in the heifers another time.
GnRH is a hormone that times the release of an egg, making fixed time AI more successful but, again, this comes at an increased cost. Each shot of GnRH costs about €5.90.
However, Stephen does not recommend doing fixed-time AI without using GnRH as the timing of a heat (and hence ovulation) is too variable for a single-timed AI protocol. Bulls are then introduced after each protocol to pick up repeats. The method you choose depends on your own preference and what suits your system.
From a cost and efficiency perspective, artifically inseminating for seven days and using a PG hormone for those not served is probably the best option for most farmers.
The final point is that if you are going to the effort of using AI on heifers, you should only use the top EBI proven bulls. No genomic or test bulls should ever be used on heifers.
Breeding heifers to AI improves your herd and increases the value of replacements. Some farmers will artificially inseminate for three weeks and then let out stock bulls. Seven days of AI and PG for the remainder gives good results. CIDR programme increases cost but reduces the time spent observing. 
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