This article gives you a basic knowledge of what is meant by artificial insemination (AI) and its advantages and disadvantages. Some methods of semen collection from male animals for insemination into the female animals will also be discussed.
Artificial Insemination (AI)
Is the possible impregnation of a female by artificial introduction of semen taken from a male. It is also defined as the process whereby semen collected from the male is artificially introduced into the female reproductive tract for the purposes of conception.
Advantages of Artificial Insemination (AI)
Eliminates time and space constraints or are taken off.
It is a very powerful tool for genetic development i.e. sex limitation on the part of the male is removed i.e. the best species of male is used for artificial insemination.
There is no physical contact between male and females animals.
It helps to control venerable disease spread in the animals, e.g. Brucellosis, etc. In artificial insemination, there is no physical contact between the male and female.
It is more economical than in natural mating. The storage and preservation of semen is cheaper than keeping a bull alive. Greater economic value from a high quality bull by selling the semen.
It helps in keeping accurate record of the female oestrous, thus breeding time can be determined. In artificial insemination, the bull to be used, the period of heat, time of breeding and time of parturition are all well recorded.
It increases safety in the farm. The danger of keeping a bull is eliminated.
Disadvantages of Artificial Insemination (AI)
Conception rates are lower in artificial insemination than for natural mating.
There is the need for accurate determination of oestrous and involves costs because it requires refrigeration facilities, with either liquid N2 or solid CO2 (dry ice).
Liquid N2 – at −196°c Dry Ice – at −78°c
Liquid N2 evaporates, so one has to keep topping up. Where Liquid N2 is not readily available, forget about deep freezing.
It requires good communication facilities to facilitate ease of contacting artificial insemination centres to inseminate animals.
Artificial insemination comes into serious conflicts. Social norms and the production system does not permit easily, the introduction of exotic breeds.
Processes Involved In Artificial Insemination
Conduct breeding program to determine the best males.
Have a lot of artificial insemination centres nationally.
Semen Collection
The five methods can be used to collect semen in most farm animals include;
The Artificial Vagina (AV) method.
The Dummy method
The electro ejaculator method
The Rectal massage method
The recovery method
The Artificial Vagina (AV) Method: The artificial vagina collection results in the best quality semen, therefore, of the five methods of collection, AV is the best. The AV is a special device that mimics the natural vagina. It consists of a hose opened at both ends.
It has an inner lining held to both ends by rubber band. Water is introduced through the valve, and blown hot air. The valve is later closed or tightened and petroleum jelly rubbed to facilitate easy penetration of the male sex organ (mimic secretion of the natural vagina)
To collect semen, a teaser female or animal is tied to the collecting crate and the male whose semen is to be collected introduced.
The male is allowed at least two false mounting before collection of the semen, by diverting his penis into the AV. The males have to be trained for collection of their semen through AV. Examples of collection from various species is given in table1.
The Dummy Method: This involves the design of a figure made in form of the animal, usually in pigs and a collecting tube inserted.
The male whose semen is to be collected is trained to mount the dummy, ejaculate and the semen drained and collected in the collection tube. Semen collection using this method in the boar is by the gloved- hand technique.
The technician wears a rubber glove on one hand with which the screw like end of the boar penis is held firmly after mounting the dummy, to mimic the locking-in of the penis in the cervix.
The boar semen is released in distinct fractions sequentially as per- sperm, sperm rich and post sperm portions, which can be collected in 3 different collection flasks. Ejaculation in the boar lasts from 10 to 30 minutes.
Electro-ejaculation (EE): This method involves electrical probe. The electrical probe is inserted in the male’s rectum after evacuating any feaces.
The probe is used to deliver intermittent voltage surges from a battery pack for electrical stimulation of the nerves around the accessory sex glands, leading to involuntary ejaculation. The semen from EE is usually more dilute and poorer in quality than those from AV and dummy.
The male animal has to be well restrained during EE to contain any violent reaction arising from the electric shocks. Also, EE is said to shorten the life span of the males on which they are used.
The Rectal Massage Method: This involves insertion of hand by a person through the rectum, usually of a bull, when feaces have been evacuated. The region of the accessory sex glands is massaged to stimulate ejaculation, and the semen flows out through the sheath of the penis.
The quality of semen under this method is lower than the previous 3 earlier discussed, because of debris that normally follows the passing of semen though the sheath.
The Recovery Method: This involves insertion of vaginal peccaries into the vagina of the female animal on heat. The male is allowed to mount and ejaculate. The pessary inserted is withdrawn and semen squeezed out.
Semen Evaluation
Appearance – Normal appearance is creamy white. Blood stain includes injury or veneral disease.
Volume – Should fall within range for the species.
Motility – Good enough motility (70%) for storage is required. At X400mag, using a phase contrast microscope.
Concentration – Should be within range for the species, determined using;
Haemocytometer
Electronic counting e.g. coulter counter
Photo electric method
To Determine the Quality
Live/dead counts – By use of eosin/nigrosin stain. They are supravital stains. Dead cells pick up eosin whereas live ones don‟t pick eosin.
Morphology of the spermatozoa – can be determined using slide smears and immersion oil.
pH – can also be determined using a pH meter.
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Table 1: Ejaculate Characteristics of Some Farm Animals
| Farm Animals | |||
| Trait | Bull | Ram | Boar |
| Volume (ml) | 3-8 | 0.5-1.2 | 150-300 |
| Sperm Conc. ×109/ml | 0.6-2 | 2-5 | 0.2-0.3 |
| Motility % | 60-85 | 60-90 | 60-80 |
| Morphological Normal Spermatozoa | 65-95 | 80-95 | 70-90 |
| pH | 6.9 | 6.9 | 7.5 |
Semen Storage/Preservation
There are several methods available, but common ones include:
Liquid Storage – This is storage above 0°C.
Deep Frozen Storage – This is storage in about 196°C. Under this condition, they can live indefinitely.
Ambient Temperature Storage – From about 20-35°C. They survive for within 2 weeks.
Chilled Storage – Usually between 4-15°C. Under chilled condition, spermatozoa can survive for 6-7 days.
Regardless of the storage method, the basic thing is to preserve the life of the cell where the spermatozoa will stay longer or to slow their metabolic rate.
Under ambient temperature storage, provide a buffer and dilute the semen so that the waste product from semen metabolism does not accumulate fast.
Flows Dialysis Method – Fresh solution enters and the medium around the cells changes frequently. The semen and spermatozoa are inside the analysis bag, which is tied at both ends and then put inside the diluents solution. The diluents solution changed frequently at definite intervals, washing away sperm waste product and supplying fresh nutrients to the cells.
Formaldehyde renders the spermatozoa temporarily dead, but after washing, phosphate buffered saline for some time, they became motile. First juice, milk etc. are as with other diluents, but while milk preserves the cells, observing them under microscope becomes opaque and difficult because of fats.
Under this method, cells survive for 8 days. When cocked in a container or McCartney bottles fig. 1 below (semen + diluents) they survive for 4 days.
Freeze Drying – Here, the water level of the spermatozoa are reduced to make it into a powdered form, but success for fertilization is poor under this method.
Other methods include formaldehyde preservation and fruit juice, milk, etc. formaldehyde render the spermatozoa temporarily dead, but other washing, phosphate buffered saline for some time, they become motile.
First while move preserves the cells, observing them under microscope becomes opaque and difficult because of fats.
Principles of Semen Preservation
Slow down the metabolic rate – can be by reduction of temperature or use of chemical metabolic inhibitors e.g. Carbon dioxides CO2, Bicarbonates HCHO.
Eliminate injurious metabolic waste or by-products e.g. by dialysis, dilution, filtration or buffering.
Supply of energy source – e.g. fructose or glucose.
Maintenance of cell integrity to prevent cold shock especially in the case of deep freezing.
This can be by use of egg yolk (protection against cold shock)
Albumin (prevent dilution shock)
Citrate (maintains membrane integrity and also a metabolite)
Cryoprotective agents (to prevent freezing injury) e.g. Glycerol, ethylene, glycol, erythritol.
Factors Affecting Fertility During Artificial Insemination (AI)
Method of semen collection and initial semen quality.
Species, breed and individual differences.
Conception rate for cattle is higher than for sheep and goats, and boars. Cattle ˃ Sheep and Goats ˃ Pigs
Semen preservation method.
Fresh or natural semen is better than chilled and chilled is better than frozen in terms of fertility. In terms of storage, frozen semen is better.
Processing method.
Holding time before process, the larger the holding time, before process the poorer and less fertility
Choice of diluents, some diluents are better infertility then others for a species
Dilution temperature – should beat about 30°C. Correct temperature will avoid shock or possible death leading to low fertility.
Dilution ratio, 1:4 (semen: diluents) best.
Method of dilution (mix gradually).
Diluents composition – should be such that pH is around 7; osmolarity should be about 300 milliosmol.
Cooling time to 5°C (should take 0.5-2hrs.). Outside normal range is not good for fertility.
Freezing method e.g.
Pellet freezing on dry ice.
Straw freezing in liquid nitrogen vapour.
Storage temperature – the lower the better in terms of length of time it can stay under storage, with some good fertility.
Length of storage (chilled or ambient temperature storage), the smaller the better.
Thawing temperature (should be 37°C).
Post thawing incubation period – the longer the poorer. Use immediately.
Timing of insemination.
Generally, insemination should precede ovulation by a few hours. With single insemination, inseminate 12-24 hours after oestrus detection.
For double insemination;
Ewes on heat detected in the morning, should be inseminated in the evening on same day and again on the following morning.
Ewes on heat detected in the evening, should be inseminated in the morning and evening of the following day.
Insemination dose – This varies between 5million -500milloin, but in poultry, after evaluating sperm characteristics for quality, volume (in ml) is used for AI e.g. 0.05mI, 0.1mI or 0.2mI, etc.
Skill of the technician: Some AT technicians are better shocked; thereafter their work results in more fertility than others.
Types of Diluents – There are different types of diluents for extending semen as in table 1.6. Some diluents are better in preservingthe spermatozoa than others for sheep for instance, the Cornell University extender is better.
Methods and site of insemination – in cattle, an insemination gun is preferred and the site of insemination is the uterine harm. Inseminations in the vagina, cervix or even uterus results in lesser fertility compared to that of the uterine harm deposition.
In sheep a vaginoscopeis used and semen deposited at the OS Cervix assigns a straw and syringe. For hens, the deposition is deep into the cloaca using a straw fitted to a syringe joined by a rubber band. In each case withdrawal of the straw or insemination gun should be gradual and gentle.
Composition
| Ingredients | Tris-Yolk | Cornell University Extender | Yolk Citrate | Homogenized Milk |
| Tris* (g) | 30.28 | – | – | – |
| Citric acid (g) | 16.75 | 0.87 | – | – |
| Fructose (g) | 12.50 | – | – | – |
| NaHCO3 (g) | – | 2.10 | – | – |
| KCL (g) | – | 0.40 | – | – |
| Tri-Na citrate (g) | – | 14.50 | 29.0 | – |
| Glucose (g) | – | 3.0 | – | – |
| Glysine (g) | – | 9.37 | – | – |
| Sulphanilamide (g) | – | 3.0 | – | – |
| Homogenized milk (cc)*1 (Cow or Goat) | – | – | – | 1000 |
| Distilled water (cc) | – | To 1000 | – | 1000 |
| Buffer (cc) | – | 800 | – | – |
| Egg yolk | 200 | 200 | – | – |
| Na penicillin (cu/ml) | 1000 | 1000 | 1000 | 1000 |
| Streptomycin Sulphate (mg/ml) | 1 | 1 | 1 | 1 |
| Distilled water | 1000 | 1000 | – |
Types of Diluents
Tris-yolk
Cornell University Extender
Homogenized Milk
*1 Cow or goat milk, heated to 92°C for 10 minutes and cooled to 37°C.
* Tris -2 Amino – 2- (hydroxyl methyl) propane – 1, 3 – diol.
In summary, artificial insemination (AI) has its advantages and disadvantages as well as methods of evaluating semen for AI. It is a powerful tool for genetic improvement.
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