On the boar, some factors influence reproductive performance which is involved in the success of the pig farm.

The reproductive rate of breeding animals is a key in a pig farm. The purpose of these is to produce many litters, in the best health conditions and with excellent productive parameters.

Currently, pig farming is one of the most important animal production systems in the world. Countries such as the United States, China, Brazil, and Mexico are among the main producers. In Latin America, swine production is one of the most important agricultural sectors. Thus, it is necessary to know the factors that affect the performance of the boar and influence the pig farm.

What characterizes the breeding pig?

Pigs are known for being prolific animals whose litters range from 10 to 18 piglets per farrowing. To achieve this, several conditions and factors are required to improve the reproductive performance of the boar and the sow. Among these factors are some linked to the genetics of the animals, others related to on-farm management, and finally environmental factors. If these requirements are met under the best production and health standards, the results will be optimal.

Pig puberty is not synonymous with sexual maturity. Therefore, a boar can be considered sexually mature when it has a sperm count of 50×106 spermatozoa. Of these sperm cells, at least 10% must be motile. Puberty begins with hormonal stimuli in the hypothalamus and pituitary gland. These brain structures will stimulate the activation of the cells of the reproductive system and thus the production of high concentrations of steroids.

Management of the boar affects performance

Among the factors involved in the reproductive performance of the boar are those related to management. In this category, there are processes related to the age at which the boar is initiated as a breeder. Housing conditions, photoperiod, or contact with females which also have an impact.

Age of reproductive initiation

Puberty in the boar begins between the 20th and 24th week of life (5 to 6 months). At this stage, the testicular tissue begins to undergo changes that favor its onset as a breeder. On the one hand, the seminiferous tubules increase their diameter and length. In addition, spermatozoa begin to be produced in their first stages. At puberty, the semen is not yet of good quality because the sperm are immature. On the other hand, the volume of ejaculate is still low, and the concentration is lower than that of a mature male. Thus, it is accepted that a boar starts breeding optimally at 28 to 30 weeks of age.

Housing

It is recommended to rise pigs in groups as this stimulates early sexual behavior and favors the onset of puberty. When boars are housed individually, these factors are prolonged and reproductive age is delayed. In addition, some distance contact with females is desirable to stimulate sexual behavior. It has been found that limiting social contact in pigs hinders future processes such as mating or decreased libido.

Photoperiod

Photoperiod has an influence on multiple organ systems, including the reproductive system of males and females. Thus, it has been found that pigs exposed during rearing to more hours of light (more than 15 hours of light/day) reach puberty and the onset of reproductive life more quickly. This significantly improves the reproductive performance of the pigs.

Nutrition

It has been found that there is a direct relationship between nutrition and the reproductive performance of the boar. Diets supplemented with vitamins, antioxidants and fatty acids develop higher fertility in some cases. In deficient diets, it has been noted that testicular development is delayed, which affects the pubertal stage.

In addition, it is important to maintain the intestinal welfare of the animals. In this sense, intestinal conditioners pronutrients are indicated to promote the regeneration of enterocytes. This effect on the digestive system improves nutrient absorption and optimizes digestive processes. In addition, these products allow the replacement of antibiotic growth promoters. These pronutrients in the diet improve animal welfare by providing better nutrition, avoiding the use of drugs and have a positive impact by improving the reproductive physiology of the boar.

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Factors affecting boar semen

Semen is the fluid produced by the reproductive system of pigs that contains sperm. It is the component necessary to impregnate sows and several factors can affect its performance.

The boar is recognized as one of the animals that produce the greatest volume of semen, between 100 and 300 mL per ejaculate.

Age of collection

Semen quality is related to the age of the boar. Thus, when semen is collected during puberty, it will have a low pregnancy rate. On the other hand, if semen is collected from pigs that have reached sexual maturity, between 10 and 30 months, good quality semen will be obtained. When pigs are 35 months old, semen quality may begin to decline. It is recommended to have 50% of pigs between 12 and 24 months (optimum performance), a maximum of 25% of males older than 30 months (longevity), and 25% of males younger than 12 months (replacement).

Frequency of collection

Ejaculate frequency has a direct impact on semen quality. It is recognized that when ejaculate collection is frequent and regular, semen quality decreases. Mainly, there is a decrease in the concentration of spermatozoa. The number of reproductive cells begins to decrease as collections are made continuously. A prudent resting time should be given for cellular and reproductive organ recovery. However, semen used from frequent collections or consecutive mating does not generate decreases in litter size.

Temperature

Temperature is a factor that affects the entire pig farm in general, from piglets to finishing pigs, sows, and boars. Heat can generate systemic stress, and this affects semen quality. At the microscopic level, abnormalities such as a proximal cytoplasmic droplet, midpiece defects, tail defects, and abnormal heads can be observed. On the other hand, sperm motility is also reduced, and ejaculate volume is lower. This impact of heat has an effect days after the stressful event but can persist for weeks. The testicles are covered by the scrotum and there are vascular cooling systems that try to counteract the heat stress.

Semen Diluent

Boar semen is diluted with special products to increase the amount of material available for sow insemination. Therefore, the choice of a good diluent is key to maintaining high-quality semen.

Thus, products such as Biopex Porcino I.A., developed by Biovet S.A., which is a boar semen extender, make it possible to increase the volume of material available for artificial insemination without affecting semen quality and to preserve the semen in optimal conditions until the moment of service. It is a long-lasting diluent, which preserves the fertilizing capacity of the sperm for seven days.

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Diseases affecting the boar

There are some diseases mainly of infectious origin that directly affect the reproductive performance of the boar. To control these infectious diseases, it is recommended to administer products that stimulate immunity in animals. Immunity stimulants of natural origin, such as Alquernat Inmuplus, stimulate specific and non-specific immunity in young and adult animals. On the other hand, they also improve the response to vaccination and complement drug therapy. If boars have a strong immune system, they will be able to resist infectious pathogens more efficiently.

PRRS

Porcine Reproductive and Respiratory Syndrome is caused by an arterivirus. Affected boars have decreased libido and semen quality is reduced. In addition, they may show signs similar to sows.

Blue eye disease

It is a disease caused by a Paramyxovirus that has mainly nervous and ocular lesions. However, it causes orchitis and loss of fertility in infected boars. It can cause farrowing on the pig farm.

Swine Erysipelas

It is a pathology caused by Erysipelothrix rhusiopathiae. Boars that are not vaccinated against this bacteria are susceptible to developing the disease. In males, it causes fever and affects semen quality, as a consequence, it negatively impacts on reproductive parameters.

Clostridiosis

Clostridioses are bacterial diseases caused by the genus Clostridium sp. These infections have a great impact on pig farms in all age groups. Boars can suffer severe alterations of the digestive system that in the medium term affect their reproductive physiology.

Brucellosis

It is a disease caused by the bacterium Brucella suis that causes inflammation of the testicles (orchitis). This pathology ends up causing damage to the testicles, which affects semen production and induces testicular degeneration. On the other hand, it can infect females and cause abortions and infertility in the whole pig farm. It is transmitted by the venereal route (mating or artificial insemination). In addition, it is zoonotic and difficult to eradicate.

Mycoplasma

Swine mycoplasmosis is caused by Mycoplasma hyopneumoniae which is considered a primary agent in the respiratory tract. Thus, it weakens the immunity of pigs and predisposes them to severe systemic infections with other pathogens.

Genitourinary infections

Numerous microorganisms that cause infection of the urinary system or at the systemic level can initiate testicular infection. Some pathogens involved are Corynebacterium, E. coli, Streptococcus, Staphylococcus, as well as Leptospirosis, Aujeszky’s disease.

Mycotoxicosis

Intoxications with Zearalenone, a mycotoxin produced by the fungus Fusarium spp. have been found to cause decreased testicular size, decreased libido, and preputial edema in young boars. These problems caused by mycotoxins can be prevented by administering compounds based on Silicoglycidol (Alquerfeed Antitox). This compound is based on a optimized molecule that binds mycotoxins, preventing them from being absorbed in the digestive tract. In addition, this mycotoxin binder does not generate residues and has no withdrawal time, nor does it bind to other important molecules such as vitamins, amino acids or drugs.

Conclusions

Multiple factors influence the reproductive performance of the boar. There are unique anatomical and physiological characteristics of the boar that favor this species to be prolific. It is necessary to consider the period of puberty and sexual maturity as stages with different characteristics.

Some management factors that affect reproductive behavior include the age of onset of breeding for each boar, as well as housing conditions, photoperiod, and nutrition.

On the other hand, some factors directly affect the boar semen used to impregnate cows. Among these is the age of the collection, the frequency of collection, and the temperature at which the sows are kept.

Finally, the multiple diseases that can affect the boar, especially those that have pathological effects on the reproductive system, must be recognized.

REFERENCES

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