2004

Contents

Boar Nutrition for Optimum Sperm Production

Limitations to Improvements in AI Efficiency

The Real Impact of Boars in Breeding Programs

Practicalities and Pitfalls of Semen Evaluation

Boar Nutrition for Optimum Sperm Production

By Mark E. Wilson and Kevin J. Rozeboom, Minitube of America, Inc and Thomas D. Crenshaw, University of Wisconsin

Introduction
Natural service boars and boars who’s semen is collected for artificial insemination make up a relatively small portion of the pig population. This may partially explain the limited amount of data on the nutritional requirements and feeding practices of adult boars.

Several research and literature reviews have been done, Kemp and den Hartog (1989), Colenbrander and Kemp (1990), Close and Roberts (1993), Brown (1994), Patience et al., (1995), Close and Cole (2000), Wilson (2000) and Kemp and Soede (2001).

Boars received little attention in a review by NRC (1998) where it was estimated that a boar requires a 2 kg feed intake per day of a 13% CP diet (lysine 0.6% and total sulfur amino acids 0.42%) containing 13.66 MJ DE/kg.

Many commercial boar studs in the US and Canada feed diets formulated above these requirements. Because the cost of feed is considered low in relation to other production costs and the potential exists for improvements in semen quantity and/or quality with higher nutritional levels, most boar diets are likely to be over fortified. Determining the specific dietary needs of the boar may not be as critical as determining potential positive and negative effects of specific dietary factors on sperm production.

When evaluating nutritional effects on boars, one should consider the following categories: libido, quality and quantity of sperm, fertility of the spermatozoa, welfare, and environmental impacts. In addition, formulation and ease of implementation of the boar diet should be considered.

Factors, which can impact research results, are age of the boar, genetics, environment, and collection frequency. All these factors must be considered when evaluating results from research trials.

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Limitations to Improvements in AI Efficiency

By Mark E. Wilson, Kevin J. Rozeboom, Brad R. Lindsey, Steve L. Terlouw and Kilby L. Willenburg, Minitube of America.

Introduction
Limitations to the improvement of artificial insemination in swine should not be correlated to the lack of technology. In fact, the amount of technology waiting to find its way into swine production is almost overwhelming. The limitation is not technology, but rather implementation. How do we make these new technologies work on the farm?

Far too often when new technologies are implemented they are taken out of the context for which they were intended. For example, transcervical insemination was developed for use with sexed semen, delivery of frozen semen and potentially for non-surgical embryo transfer. However, the implementation of this technique in the industry was to reduce the cost of semen by splitting semen doses. This increased the variation in reproductive performance and therefore actually reduced interest in this technology.

An associated problem is placing too much confidence in new equipment or techniques, while forgetting or abandoning basic principles of swine reproductive management. We must be aware of these pitfalls.

Several important points must be discussed when adopting new technology. First, what is the biological limitation of the technology being implemented? For example, if one has a 90%+ farrowing rate and a total born of 12+ pigs per litter how much can we expect technology to deliver. Once performance optimums are achieved, technology benefits the operation by reducing costs, reducing labour or improving the use of genetically superior animals.

If some such value cannot be captured, it is difficult to convince managers or employees to make the change. Secondly, the errors made in trying to adapt new technologies are numerous. Problems with adoption of new technologies involve:

• Lack of training and information
• Lack of focus on the details
• Lack of success and fear of failure
• Increased costs and/or labour so production reverts back to no change at all.

Rozeboom (2000) wrote a review on the constraints of new reproductive technologies that are emerging in the swine industry. The focus of this paper will be on issues that cause constraints on implementation of new technology.

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Practicalities and Pitfalls of Semen Evaluation

By Robert V. Knox, University of Illinois

Introduction
Current artificial insemination (AI) protocols use 2.5-3.0 billion sperm cells per insemination dose. However, despite this number of cells, there are many factors that can influence fertility with AI.

These factors can include undefined fertility factors associated with the boar, the volume inseminated, the interval from insemination to ovulation, sperm motility, the percent abnormal sperm, contaminants within the dose, and even the amount of sperm cell agglutination.

Final sperm numbers in the AI dose are critical, since the numbers of sperm can be adjusted to compensate for infertile sperm. Yet despite the numerous measures for semen quality, assessment for semen concentration is the most common test performed. This is done as insurance against, or for investigation into the causes of, poor reproduction.

There are growing industry concerns about how many sperm cells are actually provided in an AI dose. When considering the number of sperm cells required for optimal farrowing rate and litter size, numbers appear to be closely linked to interval from insemination to ovulation and also to the number of inseminations.

For example, when using a single AI of 2 billion sperm, litter size and farrowing rates are optimal with semen that was less than 36 h old, and AI was performed less than -28 h prior to ovulation (Nissen et al., 1997).

Even with multiple inseminations, Watson and Behan (2001) reported that when performing AI at 0 and 24 hours and using semen <48 hours old, 1 billion sperm cells resulted in lower farrowing rates and smaller litter sizes when compared to 2 and 3 billion sperm. Most studies indicate that 2 billion cells will not limit reproduction, but fewer cells reduces performance and higher cell numbers provide little or no advantage (Steverink et al., 1997).

This may be related to transport and reservoir establishment since these are similar with sperm in the AI dose at 50-500 million sperm/mL (range: 1-10 billion sperm, Baker et al., 1968).

Successful AI must supply enough sperm to allow establishment of a viable sperm reservoir. Adequate or even excessive numbers of sperm cells in a dose may help to keep a sperm reservoir functional for longer periods and even compensate for increased intervals from insemination to ovulation, and possibly even compensate for lower quality semen.

A good model for the effects of low numbers of viable sperm is the use of frozen sperm, since more sperm must be used (5 billion) to achieve the same reproductive rates when compared to non-frozen-thawed sperm. Additionally, insemination must occur even closer to time of ovulation (within 4 hours before ovulation, Waberski et al., 1994).

When using frozen-thawed sperm, the 5 billion sperm used are intended to compensate for loss of fertile sperm, and provide ~1.5 billion motile sperm (Hofmo and Grevle, 2000). Collectively, these studies indicate that when using conventional AI, 2 billion fertile sperm can reliably result in good fertility. However, when conditions are less than optimal, lowered sperm numbers put fertility is at risk.

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The Real Impact of Boars in Breeding Programs

By Robert V. Knox, University of Illinois

Introduction
Unquestionably, the boar has been an essential component in the success of swine production systems. This importance is independent of his role as provider of sperm for production of new offspring. What is under review in this article is the importance of the boar as it relates to his use in stimulating and eliciting the estrous response in females and his possible effect on the physiological systems of the female to improve reproductive processes. So why is it important to evaluate the role of the boar?

Part of the reason for this is that modern pig production systems can now be described as having between 500 to 1000 sows, with housing almost entirely in crates, almost completely dependent upon artificial insemination, and with the availability of limited labour.

Current production standards recommend that AI procedures should include providing boar exposure before, during and even after AI to improve the uptake, transport, and retention of semen. However, there is limited evidence to support a benefit and justification for the labour and time associated with this procedure.

Yet if providing boar exposure does have some positive impact on the efficiency of AI, perhaps ways to improve delivery of essential boar factors should be developed. Perhaps the best reason to re-evaluate the importance of the boar is that most new reproductive technologies being used such as IUI, DUI, frozen semen, long-term extended semen, and AI using only 2.5 billion sperm, rely on reduced numbers of fertile sperm.

Therefore, methods which improve sperm transport or and longevity in the tract should be evaluated. If on the other hand, the boar is not needed, then procedures for breeding in the absence of the boar should be considered.

There is clear evidence that external boar stimuli can impact puberty, detection of estrous, and return to estrous in weaned sows. What is not so evident is whether there is a physiological effect of the external boar stimuli that impacts fertility.

Internal boar stimuli, from the act of natural mating, to components of seminal fluids have been shown to influence physiology within the female. The effects of these internal boar components have been reviewed elsewhere (Soede et al., 1993; Waberski et al., 1997) and this article describes the known external effects of the boar, independent of his contribution of semen and seminal components, on measures of female reproduction.

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Source: Paper presented during the 2004 Banff Pork Seminar Procedings