Using highest-index boars in AI program can boost the bottom line

PEET ON PIGS Using top 15 per cent of boars in AI program could add 
nearly $550,000 per year in profits in a 10,000-sow production system

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While artificial insemination (AI) in pigs has become almost universal in the worldwide swine industry, it has a number of disadvantages, according to Michael Dyck from the University of Alberta.

Changes to the way in which boars are used and AI techniques utilized can capture the increased genetic potential of higher-index boars and add significant dollars to the bottom line, he says.

There are three major problems associated with current AI methodology, said Dyck.

“First, the effectiveness of standard semen evaluation methods is relatively low compared to other species and poor-quality boars will affect the reproductive outcome of many females,” he said. “Employing the use of subfertile boars and low-quality ejaculates reduces production efficiency.”

As well, the use of “pooled” semen — where the semen of several boars is mixed — breaks the link between known genetic value of individual boars and the paternity of the progeny produced. Finally, the high number of sperm used, typically three billion per dose, and consequently the high numbers of boars needed for semen production, reduces the genetic impact of the best boars.

For the genetic value of the highest-index boars to be more fully utilized, then AI methods involving two billion or even one billion sperm must be used. But research shows that using one billion sperm tends to result in reduced fertility because sperm from the less fertile boars in the dose has a bigger impact than where a dose of three billion sperm is used. The current practice of using three billion sperm in a pooled semen dose provides a large safety margin because it masks the less fertile boars. Identifying the least fertile boars and culling them would allow lower numbers of sperm per dose to be used while still achieving high fertility rates. However, there is a lack of suitable methods to evaluate the fertility of individual boars.

“Conventional semen evaluations, such as concentration, morphology and motility, can establish that a boar is either subfertile or infertile, but they cannot identify the relative fertility of boars that meet accepted industry standards for sperm and ejaculate quality,” said Dyck.

“There is a long history behind the search to find a single or combination of tests that can accurately predict male fertility from a semen sample.”

Unfortunately, there appears to be no simple answer to this very complex question. As a result, there is no accepted methodology for evaluating the relative fertility of AI boars. Therefore in practice, the least fertile boars have to be identified through the measurement of standard productivity parameters such as conception rate, farrowing rate, and litter size.

The solution is to implement new AI technology, said Dyck.

“This involves a move to single-sire inseminations with the lowest possible doses of semen and the use of ejaculates from boars with high genetic value and proven fertility in a ‘low semen dose’ environment,” he said.

Dyck has developed an economic model based on a 10,000-sow production system with an internal 100-boar stud in order to calculate the benefits. Changes to the boar stud procedures and AI techniques are made in three stages.

“The first stage in the transition process is to process semen as single-sire doses of two billion sperm,” said Dyck. “A minimum of 50 single-sire matings is then used to identify the top 66 per cent of boars in the stud and then the lowest performing boars are removed, increasing the average index of the remaining boars.”

Once this stage has been implemented, it would result in an annual value of benefits and cost savings of more than $200,000. An indirect result of removing the least fertile boars is that the number of pigs weaned per sow would rise from an assumed starting figure of 24.5 to 26.5.

“The second stage involves moving to post-cervical AI, using one or 1.5 billion sperm cells per dose,” he said. “Again, 50 matings are used to identify the top 33 per cent of boars in the stud and the lower-performing boars are removed, increasing the average index. This would result in performance benefits and cost savings of over $400,000 per year.”

The third and final stage is to move to a single, fixed-time AI protocol, involving the use of a hormone treatment after weaning to synchronize ovulation. Post-cervical AI, using one to 1.5 billion sperm per dose is then used as in stage two.

“Fifty matings per boar are used to identify the top 15 per cent of boars in the stud and the remaining boars removed, leaving just 15 boars in the stud,” said Dyck. “This would increase the economic impact to nearly $550,000 per year in the 10,000-sow production system.

“The evaluation of relative fertility amongst commercial AI boars, and a move to single-sire AI programs in combination with advanced AI techniques holds significant potential economic benefits to the swine industry. Results to date suggest that the relative value of commercial progeny could be increased by between $0.80 and $1.30 per pig born and would largely reflect the genetic merit of elite boars in terms of growth performance and feed efficiency of their offspring.”

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