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ARTIFICIAL INSEMINATION IN PIGS- TECHNOLOGY TO BOOST PORK PRODUCTION

ARTIFICIAL INSEMINATION IN PIGS- TECHNOLOGY TO BOOST PORK PRODUCTION

M.Karunakaran, U.Ratnakaran, E.B.Chakurkar, P.K.Naik, N.P.Singh

ICAR RESEARCH COMPLEX FOR GOA

OLD GOA, GOA- 403 402

INTRODUCTION

Artificial insemination is a technique in which semen with live sperms is collected from the male and introduced into female reproductive tract at proper time with the help of instruments under hygienic conditions that results in the formation of a normal offspring. All over the world, AI has helped to improve the reproduction and genetic use of farm animals.

HISTORY OF AI

AI in domestic animals has been practiced as early as 1322 AD. In the 14th century, an Arab chief collected semen with cotton plug and inserted to other mare’s vagina where conception was achieved. In 1780, the first scientific research in artificial insemination of domestic animals was performed on dogs by Spallanzani. His experiments proved that the fertilizing power reside in the spermatozoa and not in the liquid contents of semen. The AI of swine was initiated by Ivanow in Russia in the early 1900s (Ivanow, 1907; Ivanoff, 1922).

During the past decades, there was an increase on the usage of AI by swine producers. The main purpose is mainly to use genetically superior boars so that the producers gain a lot of benefit through insemination, but for a successful insemination to occur the AI schedule should be optimized. For a successful production, the AI program should require skilled management, especially in the detection of proper estrus in sows, proper handling of semen and follow proper insemination procedure and finally result in high conception rate and litter size. AI in pigs poses special problems chiefly due to the anatomy of the reproductive tract and the polycotous nature of litter bearing.

During natural mating, the boar ejaculates 50-70 billion spermatozoa in the cervical canal, which later passes into the uterine body and horns. Only those sperms that reach the fertilization site are capable of overcoming the female hostile environment. A large amount of seminal plasma (250- 400ml) is also added to the semen volume that helps in the distention of body and horns. The glans penis of the boar enters the cervix during mating. A pressure is applied on the glans as it enters the cervical canal to facilitate ejaculation.

 The purpose of insemination is to establish an adequate functional sperm reservoir in the oviduct to fertilize all the ovulated oocytes. The insemination procedure deposits the semen dose within the posterior portion of the cervical canal by a catheter that engages the folds of the cervix. Over the past decade, new insemination procedures based on the deposition site of the insemination dose have been developed. The new protocols for semen deposition includes in the uterine body (postcervical insemination or intrauterine insemination), or deep in the uterine horn (deep intrauterine insemination), or in the oviduct (laparoscopic intra-oviductal insemination).

 Advantages of AI

Several breeds of boars possessing superior quality semen are available at various AI centres. The genetic influence of good boars can be spread more widely. AI is a safe and an inexpensive method of introducing new genes into pig herds. AI overcomes size differences between boars and sows. The maintenance cost of boars can be saved. Early detection of inferior males can be ensured by semen evaluation. The semen of a desired size can be used even after the death of that particular sire. It is helpful to inseminate the animals that refuse to stands or accept the male at the time of oestrum. It helps in maintaining the accurate breeding and farrowing records. Old, heavy and injured sires can be used.

Disadvantages of AI

Requires well-trained operations and special equipment. Necessitates the knowledge of the structure and function of reproduction on the part of operator.Improper cleaning of instruments and in sanitary conditions may lead to lower fertility. Requires more time than natural services. The great variability in duration of the oestrum (from 12 to more than 96 hours) and the time of ovulation among the swine females. AI carried out at improper time or done incorrectly. Maintaining the doses at temperature from 15°C to 18°C. The reduced survival of the sperms in the female genital organs. Reduced farrowing rate (50%) with frozen semen. Lower than average results with chilled semen stored longer than 72 hours.

Methods in semen collection

a)Artificial vagina: It consists of a hard tubular casing with a rubber lining filled with warm water. b) Electro-ejaculation: A method where an electrical current is applied to the pelvic nerves and muscles via a rectal probe, which is attached to an external power source. c) Gloved Hand technique – most common method used to collect semen. To ensure high sperm cell oncentration and semen volume, do not collect boars more than three times a week.

Boar semen

The boar matures between 6 and 8 months, and donates semen. The volume is about 200 to 500 ml. The ejaculations are in 3 sets. The first and third do not contain spermatozoa but the second is rich in sperms. In 1969, McDonald reported that, the boar's ejaculate is delivered in three portions. The pre-sperm portion is a sticky, strongly coherent, mucus substance, the second fraction contains the spermatozoa and the post-sperm fraction is a viscous, gel-containing portion. The gel constitutes 20 -25% of the total volume of the ejaculate.

Boars are trained to mount live or dummy females and ejaculate. In case the boar shows no interest, the dummy can be smeared with the urine of oestrus female which will enhance the libido and lead to quicker ejaculations. The average duration of ejaculation is 10 minutes but varies considerably between boars. The semen from one ejaculate can be used to inseminate 15 to 25 sows.

Evaluating boar semen

Volume;  Semen volume varies between 100 and 500 mL and can be measured with a graduated measuring cylinder.

Motility

Subjective assessment of sperm cell motility is the best way of estimating semen quality. Using the low power lens (10X) of a microscope, examine semen on a warm slide (30 to 35°C) immediately after collection. Good quality semen shows a typical 'wave' motion and individual spermatozoa movement. A poor sample shows weak motility and 'clumping' of spermatozoa. Motility depends on how much of each fraction is collected. If the collection is mainly sperm-rich fraction, there is higher motility and wave motion than when accessory fluids dilute the semen. If total abnormalities are less than 25%, semen quality is satisfactory.

Storage of semen

If the semen is to be stored, it should be diluted or extended immediately following collection. Before mixing, both the diluents and semen should be bought to same temperature (32 to 35°C)  in a warm water bath. To avoid diluent shock, gently add the diluent to the semen, not the semen to the diluents and later agitate slowly for proper mixing of both solutions. The diluted semen can further be evaluated and stored at 15-18°C.

ESTRUS DETECTION IN SOW

Heat detection is the most important and time consuming part of an A.I. breeding program. Heat detection is a matter of observing changes in appearance and/or behavior that occur when an animal comes into heat The goal of heat detection is to determine when the sow or gilt reaches standing heat. Standing heat is the period when a female stands still and rigid when weight is applied on her loin. For a successful insemination, detection of standing heat is the most important criteria. Gilts should be bred 12 hours after standing heat is detected, and again 12 hours later. Sows should be bred 18-24 hours after detection of standing heat, and again 12 hours later.

 Behavioral changes observed during estrum

Sows and gilts that are coming into heat may chant, growl or make other unusual noises and attempt to ride other sows. Sows in heat show increased interest in boars placed in an adjacent pen. As a sow or gilt begins to show increased activity, her vulva often reddens and swells and  begin to subside 12 to 36 hours before the animal reaches standing heat. When a female is in standing heat, the clitoris is engorged with blood, causing it to protrude outward and have a bright red color. Females often have an increased discharge of mucous from the vulva as they approach standing heat. At first the mucous is clear, slick and slimy, but usually becomes cloudy and sticky during standing heat. Straw or bedding stuck to the vulva is another sign that the animal is discharging sticky mucous. A female in standing heat will stand still and rigid, and may push back by arching her back slightly when weight is applied to the loin. This is an instinctive response that braces her to support the weight of the boar. Ear popping is a sure sign that the animal is in standing heat.

Insemination Technique

The insemination procedure consists of the conventional method of insemination, post-cervical insemination or intrauterine insemination), deep in the uterine horn (deep intrauterine insemination) and in the oviduct (laparoscopic intra-oviductal insemination).

Conventional AI

 It was the first to be developed and is the most straight forward in application.

Around, 2.5– 3.5 billion spermatozoa are inseminated in 80– 100 mL of extender via a simple catheter located at the distal cervix.

 METHOD

The sow or gilt should be in standing heat. Clean the vulva with a damp cloth or paper towel so as to prevent contaminants being pushed into the reproductive tract when the insemination rod is inserted. The insemination rods come in a variety of shapes and sizes. The two most common styles are rods with counterclockwise threads on the tip, and foam tipped rods. When using threaded rods, lubricate the tip with semen or a little KY Jelly before gently inserting it into the vulva. Angle the rod tip upward (toward the backbone) to avoid the opening to the bladder. Push the rod gently and continue to twist counterclockwise until the tip is locked into the cervix. When the tip is locked, the rod will spring back into place when you pull gently on it. Foam tipped rods do not need to be rotated. Gently push on the rod until you feel the foam tip catch in the folds of the cervix.

 Post-cervical or intrauterine insemination

The aim of this insemination procedure is the deposition of the spermatozoa in the uterine body. The main obstacle to the post-cervical insemination is the cervical canal, characterized by the presence of the cervical folds. The majority of the devices are assisted by a commercial AI spirette used to produce a cervical lock. The devices, usually 15–20 cm longer than a conventional catheter, and these are inserted through the lumen of the spirette, and then extend through the cervical canal forward to the uterine body. Most commonly 1000 million spermatozoa in a volume of 30 mL are inseminated. The main advantage cited is decreased backflow loss and it was recently reported that the percentage of backflow volume was nearly two-thirds of the inseminated volume. Careful attention should be paid to proper insemination technology to minimise the incidence of cervical and uterine damage, since the semi-rigid extended catheters can damage reproductive tissues.

 Low-dose insemination: deep intrauterine insemination

The objective of deep intrauterine insemination (DUI) is the deposition of the spermatozoa into the far depths of the uterine horns. The main obstacle to DUI of sows is the complex anatomy of their genital tract, not only by the presence of the cervical folds (the same as for post-cervical insemination), but also by the length and coiled nature of the uterine horns. The new, specially designed device has a working length of 1.80 m, 4 mm outer diameter, and 1.80 mm diameter of the inner tubing. Deep uterine catheterization is performed after the insertion of a commercial AI spirette (to produce a cervical lock). The catheter is then inserted through the spirette, moved through the cervical canal, and propelled forward along the uterine body and uterine horn. The DUI procedure has been successfully used with concentration of spermatozoa 150–600 million in liquid diluted, and 1000 million frozen–thawed samples.

 Very low-dose insemination: intra-oviductal insemination

The development of techniques to inseminate into the oviduct is believed to be able to maximally reduce the number of spermatozoa required. Laparoscopy is a less invasive technique than laparotomy for depositing semen directly into the uterus or oviduct. In sows, depositing spermatozoa by laparoscopy in the uterine horn, close to the uterotubal junction, achieves high (92.3%) fertilization rates with only 10–20 million spermatozoa per horn. Intra-oviductal insemination does introduce a high number of spermatozoa into the oviduct (0.3–0.6 million spermatozoa. The incidence of polyspermic penetration is very low when 0.3 or 0.5 million spermatozoa are inseminated.T herefore laparoscopic insemination has a highpotential effectiveness for obtaining pregnancies with a very low number of spermatozoa. All of these insemination procedures should be useful tools for the pig industry.

 Conclusion

Whether using semen collected on-farm or buying it from an AI centre, successful insemination hinges on:

  • detecting oestrus in the sow
  • correctly timing the insemination
  • using the right technique
  • correct storage and handling of semen
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Please note that this is the opinion of the author and is Not Certified by ICAR or any of its authorised agents.