Overview of Artificial Insemination in Poultry
Artificial insemination (AI) is widely used to overcome low fertility in commercial turkeys, which results from unsuccessful mating as a consequence of large, heavily muscled birds being unable to physically complete the mating process. This is a serious and costly problem in the production of commercial turkey hatching eggs. In most commercial chicken production systems in the USA, it has not been necessary to implement AI programs because natural mating results in adequate fertility levels, but AI is routinely used in special breeding work and research. However, as managing commercial broiler breeders to maximize fertility becomes more challenging, the use of AI in commercial poultry operations outside the USA is becoming more common. Certainly, the use of AI in chickens, as in turkeys, can improve fertility; however, the cost of implementing AI on a large scale is often cost prohibitive.
Collecting semen from a chicken or turkey is done by stimulating the copulatory organ (the phallus) to protrude by massaging the abdomen and the back over the testes. This is followed quickly by pushing the tail forward with one hand and, at the same time, using the thumb and forefinger of the same hand to apply pressure in the area and to “milk” semen from the ducts of this organ. Semen flow response is quicker and easier to stimulate in chickens than in turkeys. The semen may be collected with an aspirator (turkeys) or in a small tube or any cup-like container. In turkeys, the volume averages ~0.35–0.5 mL, with a spermatozoon concentration of 6 to >8 billion/mL. In chickens, volume is 1–2 times that of turkeys, but the concentration is about one-half. Collected semen is usually pooled and diluted with an extender before use.
Chicken and turkey semen begins to lose fertilizing ability when stored >1 hr. Liquid cold (4°C) storage of turkey and chicken semen can be used to transport semen and maintain spermatozoal viability for ~6–12 hr. This short-term storage of semen is common in turkeys, while not as common in chickens. When using liquid cold storage for >1 hr, turkey semen must be diluted with a semen extender at least 1:1 and then agitated slowly (150 rpm) to facilitate oxygenation; chicken semen should be diluted and then cooled—agitation is not necessary. Chicken and turkey semen may be frozen, but reduced fertility limits usage to special breeding projects. Under experimental conditions, fertility levels of 90% have been obtained in hens inseminated at 3-day intervals with 400–500 million frozen-thawed chicken spermatozoa.
Several commercial semen extenders are available and are routinely used, particularly for turkeys. Extenders enable more precise control over inseminating dose and facilitate filling of tubes. Results may be comparable to those using undiluted semen when product directions are followed. Dilution should result in an insemination dose containing ~300 million viable spermatozoa for turkeys. However, the number of spermatozoa inseminated will range from 150–300 million viable cells depending on the age of the turkey hens inseminated. In chickens, the number of diluted semen inseminated will range from ~100–200 million sperm cells per insemination. Producers usually determine the spermatozoa concentration and dilute the semen to obtain the appropriate sperm cell concentration for either the turkey or chicken.
For insemination, when holding the hen upright, pressure is applied to the abdomen around the vent, particularly on the left side. This causes the cloaca to evert and the oviduct to protrude, so that a syringe or plastic straw can be inserted ~1 in. (2.5 cm) into the oviduct and the appropriate amount of semen delivered. As the semen is expelled by the inseminator, pressure around the vent is released, which assists the hen in retaining sperm in the vagina or oviduct. When inseminating undiluted turkey semen, the high sperm cell concentration allows for 0.025 mL (~2 billion spermatozoa) to be inseminated at regular intervals of 7–10 days, yielding optimal fertility. In chickens, because of the lower spermatozoon concentration and shorter duration of fertility, 0.05 mL of undiluted pooled semen, at intervals of 7 days, is required. The hen’s squatting behavior indicates receptivity and the time for the first insemination. For maximal fertility, inseminations may be started before the initial oviposition in turkeys, whereas this is not necessary in chickens. Fertility tends to decrease later in the season; therefore, it may be justified to inseminate more frequently or use more cells per insemination dose as hens age.