Artificial insemination is the most widely used reproductive technology in the livestock industry. Its adoption in poultry species has increased in popularity, especially in the western countries for research and commercial purposes. In Kenya, this technique is mostly used by poultry research and breeding centres. However, there are scenarios in which commercial poultry farmers may benefit from artificial insemination in poultry:
· In broilers, the males have extreme body conformation, broad bodies and short legs, which hinder natural mating. Also, as the selection for faster growth rates in broilers is intensified, fertility in males is likely to decline due to the negative relationship between growth and fertility. Application of AI in such scenarios is cost effective in broiler breeding management.
· AI allows for incompatible individuals to mate; incompatibility arises when males are heavier than females and under natural mating this may result to injury of the females.
· AI allows for better use of the cage feeding system in hatchery operations, especially when dealing with large number of females that are required to lay fertilized eggs.
· AI allows for one male of high genetic merit for a particular trait of interest to serve more females therefore, increases the number of offspring per cock compared to natural mating which is limited to a mating ratio of 1male:10 females.
Artificial insemination in chicken requires one to understand the basic anatomy and physiology of the hen’s and the cock’s reproductive tract. In addition to this one must be technically competent with the semen collection and deposition procedures in order to achieve effectiveness in producing fertilized eggs.
Semen collection procedures
Prior to semen collection, cocks need to be trained and this is achieved through abdominal and back massage for about a minute for 3 days, consecutively. The abdominal massage method is the most commonly used since it is non-invasive and has minimal stress on the cock. The procedure involves restraining the male, followed by gentle but rapid stroking of the abdomen and back region (testes are located in this region) towards the tail. This stimulates the copulatory organ causing it to protrude. At this point, the handler quickly pushes the tail forward with one hand and, at the same time, using the thumb and forefinger of the same hand to gently squeeze the region surrounding the sides of the cloaca to “milk” semen from the ducts of the copulatory organ. Semen may then be collected in a small tube or any cup-like container. This procedure is repeated twice, once a day; an additional round may cause damage to the testes and cloacal region.
The volume of semen that can be collected from a single cock ranges from about 0.7 to 1.0 ml, with a spermatozoon concentration of 3 to 4 billion/ml. However, the quantity of semen depends on genetics and environmental factors such as age, bodyweight, season and nutrition. The degree to which the male will respond to the abdominal massage technique and the pressure applied on the ejaculatory ducts will also influence the quantity of semen produced. Chicken semen begins to lose fertilizing ability when stored for more than 1 hour; therefore it must be deposited in the hen within the 1 hour of collection. In the case of short-term storage and transportation of the semen, it is necessary to use liquid cold (4⁰c) storage to maintain spermatozoa viability for up to 24 hours.
Semen deposition procedure
Vaginal insemination is commonly used for semen deposition as there are less risks of injury the hen. Preliminary stroking and massaging of the back and abdomen is required to stimulate the hen. This is followed by applying pressure to the left side of the hen’s abdomen around the vent causing evertion of the cloaca hence protrusion of the vaginal orifice. An inseminator containing the semen is inserted 2.5 cm deep into this opening for semen to be deposited. As the semen is expelled by the inseminator, pressure around the vent is released, so that the oviduct can return to its normal position and draw the semen inwards to the utero-vaginal junction. Inseminators such as straws, syringes or plastic tubes may be used. During insemination, the volume of semen required per hen is about 0.1ml which contains about 100 to 200 million sperms. Timing of the insemination should be considered. It is best to inseminate hens in the late afternoon (2:00pm and 4:00pm), since in the morning hours hens may have an egg in the oviduct, making it difficult for the sperm to swim up to the ovary. A significant feature of the reproductive physiology of the hen is her ability to store fertile spermatozoa for up to 14 days in the sperm storage tubules located at the utero-vaginal junction. The tubules release the semen, slowly over time, which swim to the fertilization site and therefore allows for hens to be inseminated consecutively for two days for the first time, and thereafter at regular intervals of 14 days. Twenty-four hours after insemination, egg-breakout analysis is carried out to determine egg fertility.
Currently, the Smallholder Indigenous Chicken Improvement Program (InCIP) – research unit at Egerton University offers training to interested farmers on the artificial insemination in poultry. The training does not require any background on poultry science, just an individual’s interest. This is because the training covers the fundamentals of the reproductive anatomy and physiology of the male and female, at a theoretical and practical level. Thereafter, the trainees are taken through a practical lesson on semen collection and deposition techniques, and egg fertility analysis. The training takes a period of two weeks and the expectation at the end of it is that individuals have the capacity to carry out semen collection from males (abdominal massage, semen milking and semen handling), semen deposition in females (cloacal evertion, semen deposition) and differentiate fertile eggs from infertile eggs.
Story by Sophie miyumo (research assistant at InCIP-research unit, Egerton University)