April 2007

AI and its Influence on Production Efficiency

Christianne E. Glossop - Malmesbury, Wiltshire, England

Introduction

AI in pigs is by no means a new technique. Methods for semen collection and processing, and for sow insemination had been devised during the 1930's on the State Farms in Russia (Milovanov, 1934) although there was little commercial application of this system in the years that followed. In 1956 AI was re-introduced to the pig industry by Chris Polge (1956) who highlighted the benefits of a process which facilitated more widespread use of an individual superior boar than would be possible through natural service; a system which offered all producers, regardless of herd size, access to the best boars available. At that early stage, advantages offered by AI included livestock improvement, disease control, facilitation of cross-breeding programmes, convenience and economics (Reed, 1969).

The pig industry then followed a laborious and sometimes painful period learning curve as a system was developed which could ensure consistently high levels of fertility at all levels of production. Behind these efforts was the driving force of enhanced efficiency and product quality so essential to the ongoing development and success of the industry. By the 1980 s a workable system was in place; although further improvements were still required, AI could be applied to all levels of production, including the commercial herd (Reed, 1982).

The Application of AI

AI is now used world-wide, although the level of usage, and the systems adopted vary between countries according to such factors as the structure of the industry, herd size, distribution systems and climate (Glossop, 1991). In many European countries there is a well-established network of commercial AI studs offering a semen delivery service to producers, while working in close collaboration with the Breeding Companies. The use of on-farm AI is also developing as producers recognise the economic benefits of producing semen within the herd. Some larger integrated companies are choosing to establish dedicated AI studs, operated for their own exclusive use. This facilitates quality control and biosecurity measures far in excess of the more simple on-farm AI operations, and has much to offer a dynamic pig industry (Almond et al, 1994).

AI now forms an integral part of the service routine in herds at all levels of the breeding pyramid from the nucleus herd to the commercial operation. It is used on herds of all sizes and management systems, facilitating cost savings, improved performance and enhanced product quality, and better control over this most significant component of the herd. It is now exploited in a significant way as a means of widespread dissemination of superior genetics at a reduced risk to health, and as a valuable aid to service management. It has been incorporated into the weekly service management routine on units of all sizes, and types, from the small pedigree herd to the large-scale operation with in-house multiplication and on commercial units producing slaughter pigs. Let us consider the different levels of application of AI in some detail:

The Genetic Nucleus

Breeding companies the world over are making good use of AI within their nucleus activities - the heart of genetic improvement. At this level, AI facilitates widespread use of individual boars or groups of boars enabling comparison and strategic use across a number of different populations, and allowing greater accuracy of testing and selection programmes. Through AI different nucleus populations within one world-wide breeding operation may be linked on a regular basis, ensuring achievement of common goals and standards of genetic improvement and introduction of new lines rapidly and efficiently, whilst in no way compromising biosecurity of individual herds within the international pyramid structure.

Multiplication Level

AI minimises genetic lag between nucleus and multiplication levels of production, ensuring that genetic progress is passed on to the customer as rapidly as possible. As the larger pig production operations move increasingly towards within-herd multiplication, the economic significance of AI increases.

Commercial Herds

AI offers major benefits to the commercial producer in terms of enhanced production efficiency and optimised product quality. It is now essential for a breeding company to offer parent boar genetics in the form required by the customer - whether that be natural service boars, AI boars for in-house use, or semen. The trend towards the establishment of in-house AI studs or even dedicated boar studs by the larger integrated producers presents the breeding company with new challenges and responsibilities. Improved porcine DNA must be delivered and serviced by its supplier, and that is now including the provision of training, and advice in all aspects of the AI process.

The Benefits of AI

The main benefits of AI application are cost savings, enhanced performance and improved product quality. The successful pig producer of tomorrow is one who can produce high quality pig meat at the lowest possible price; anything which contributes towards this goal has a place in an efficient operation. The fixed cost of producing a dose of semen represents a significant proportion of the total expense; efforts are now concentrating on minimising production costs per unit dose, by increasing both the size and output of the AI stud. Stud size is growing, and the producer is the beneficiary. Commercial AI is now priced competitively against natural service, with the added bonus of quality assurance and superior genetics.

The selection of boars for AI is of extreme importance as each AI sire has a far greater influence on the next generation than a boar used for natural service. AI boars must be selected from the best available, taking into account not only the EBV (estimated breeding value) but also paying proper attention to physical conformation. Stud boars must constantly be updated as better sires become available. AI facilitates reduction in genetic lag between nucleus and multiplication levels of production as well as ensuring the provision of top-performing boars in the commercial herd. Though this aspect has been discussed over many years it has yet to be exploited to the full.

The Options

At one end of the scale is the relatively low-key option of a modest in-house AI facility, where the boars are housed and worked in the service house, the semen being processed according to simple procedures and inseminated on the same unit within hours of collection. This system is favoured by some smaller producers, although the minimum unit size for which on-farm AI makes economic sense is probably around 400 sows. It is also used widely in countries where semen transportation is impracticable. The system has an excellent track record and has a much to offer. It is important to remember the limitations of the system however - in particular that the semen produced should be used in-house only. At the other end of the scale is the separate AI centre, established in isolation from other pigs, and supplying semen to many different units. This type of operation can justify investment in more advanced equipment and technology, and employ specially trained and experienced staff. Whichever method of AI application is adopted, planning, training and attention to detail are essential to success (Almond et al, 1994).

The Challenges Facing AI

As the role of AI continues to develop there are a number of issues which are key to its success:

Fertility

The growth in AI usage has depended upon achievement of fertility results equal to those with natural service. This is now possible provided that sufficient training is carried out and attention paid to detail in the handling, storage and insemination of the semen (Glossop, 1991). New developments in semen assessment and preservation, along with improvements in insemination timing and techniques have the potential to enhance still further fertility achieved with AI.

Quality Control

For AI to fulfil its potential, semen of a consistently high quality as expressed by fertility parameters and health, and of adequate shelf-life to simplify collection schedules and semen despatch must be produced at an economic price (Colenbrander et al, 1993). This highlights the importance of adopting a strict code of practice, detailing all the procedures involved, concentrating on quality and consistency, taking into account the importance of training and standardisation of excellent practice. The benefits of AI are achieved only where all involved are 100% committed to its application, are trained thoroughly and have a clear understanding of the processes involved. Quality control procedures and attention to detail are key to this - only in this way can the necessary controlled and orderly approach be adopted. For this reason it is recommended that a protocol encompassing all functions of the operation be established at the outset and followed strictly. This protocol will be unique to each individual AI operation, and is likely to evolve as systems are modified, but the concept of following a strict order of procedures should be maintained.

Biosecurity

In terms of health, AI is the safest practical means by which new genetic material may be introduced into a herd. Although there are a number of important pathogens which have been isolated in boar semen, AI has an excellent track record in this respect. Successful application of AI depends upon the exercise of tight health control procedures. The establishment of an in-house health policy is fundamental to the successful adoption of AI into any operation, and this must take into account all aspects of the breeding programme, incorporating official health regulations pertaining to the transportation of semen across international boundaries as appropriate (Connor et al, 1994). The protocol must be described in sufficient practical detail to ensure that it is not subject to personal interpretation, and should address the following matters:

• siting and design of the stud
• health of source herds
• pre-entry testing for all AI boars
• quarantine/acclimatisation procedures for new boars
• continual health monitoring of the stud population
• hygiene precautions within the stud

There is considerable variation in the size, design and function of AI facilities, from the most simple in-house arrangement where semen is collected, processed and inseminated all on one unit, through to the fully-licensed AI studs operating under national regulations, supplying semen to a wide range of external customers. The biosecurity implications of these two extremes of AI application are quite different, although the overriding consideration is the same - maintenance of health status while exploiting the benefits of widespread boar usage. AI customers must ensure that they are familiar with, and comfortable with the health protocol of their semen supplier. Semen quality and productivity can be affected adversely by infectious disease. This is another reason why stud health should be protected.

New Developments

Successful application of AI requires a certain level of technical expertise. The industry owes much to the pioneers of AI in the early days who contributed so much towards the development of the system which is in place today. The insemination dose and volume had to be defined, methods for the extension of semen optimised and techniques and regimes for insemination described. Let us look at some of the current technologies in some detail:

Semen Assessment

The most accurate test for the viability of an ejaculate is to introduce it into the reproductive tract of an oestrus sow to study the fertilisation rate as expressed by conception rate and litter size - this clearly is impractical. Techniques in current use in the commercial AI laboratory for assessment of semen quality rely on subjective estimations of motility, photometric measurement of sperm count and microscopical examination of sperm morphology. A number of new techniques for assessing sperm viability have been described e.g. osmotic resistance test and sephadex and glass wool filtration, penetration of salt-stores oocytes, in vitro fertilisation and computer-aided semen assessment (CASA); these require further testing in the field.

Fresh Semen Shelf-life

Semen diluents have two main functions in extending the volume of the ejaculate and preserving the viability of the spermatozoa. For all practical purposes diluents in current use preserve the life of semen up to for 5 days, although some have demonstrated interesting results with longer-term storage. The development of a longer-life diluent (up to 8 days) would render AI programmes more practical in terms of despatch and boar availability. An understanding of sperm membrane stability and the physiological requirements of these cells would provide useful information in the design of a new diluent.

Frozen Semen

The cattle AI industry relies heavily upon the use of frozen semen, whereas pig AI is based almost entirely upon fresh semen. The reason for this is the reduction in fertility with frozen pig semen experienced - porcine sperm appear to have very different characteristics when it comes to cooling and freezing. The most promising techniques available involve freezing the semen in straws or sachets, using egg yolk and glycerol as protectants against damage during the cooling, freezing and thawing processes. Such techniques require optimisation with an emphasis on incubation times, cooling and freezing rates.

Insemination Regime and Technique

AI service management of sows and gilts has been studied in some detail (Flowers and Ebenshade, 1993). The role of the boar in oestrus detection and in the stimulation of sows during AI has been emphasised. Various service regimes involving different combinations of AI and natural service (with an entire or a vasectomised boar) have been explored and are of application in different breeding situations. Consideration of the timing of events leading to successful fertilisation in the pig demonstrates the importance of ensuring that viable spermatozoa are present within the reproductive tract in advance of ovulation (Weitze et al. 1990, a and b). This may be of even more significance in the use of AI. Ova remain viable in the oviduct for around 8 hours following ovulation and exposure to sperm after this time results in reduced fertilisation rate and subsequent litter size; where the delay is too great the outcome may even be total conception failure (Hunter, 1988).

Conclusion

There are considerable benefits offered to the pig industry by successful application of AI. Full exploitation of these benefits depends upon commitment and planning. New developments in AI technologies are likely to enhance the system still further in the years ahead.

References

Almond, G.; Glossop, C.; Britt, J.; Morrow, M.; Carr, J. See; Flowers, B. (1994). The Swine AI Book. Morgan Morrow.
Colenbrander, B.; Feitsma, H.; Grooten, HJ. (1993). Journal of Reproduction and Fertility Supplement 48: 207.
Connor, J.F.; Christianson, W.T.; Glossop, C.E. (1994). Proceedings of the 13th International Pig Veterinary Society Congress, Bangkok: 367.
Flowers, W.L.; Ebenshade, K.L. (1993). Journal of Reproduction and Fertility Supplement 48: 217.
Glossop, C.E. (1991). In Practice 13: 191.
Hunter, R.H.F. (1988). Proceedings of the Pig Veterinary Society 21: 85.
Milovanov, V.K. (1934). Animal Breeding Abstracts 2: 403.
Polge, C. (1956). Veterinary Record 68: 62.
Reed, H.C.B. (1969). British Veterinary Journal 125: 272-280.
Reed, H.C.B. (1982). Control of Pig Reproduction. London: G. Butterworth Scientific. 65.
Weitze, K.F.; Lotz, J.H.; Everwand, A.; Willmen, T.; Waberski, D. (1990b). Reproduction in Domestic Animals 25: 197.
Weitze, K.F.; Rabeler, J.; Willmen, T.; Waberski, D. (1990a). Reproduction in Domestic Animals 25: 191.