Follicles development in quails

Lately, quail growing has awaken a great interest amongst producers, companies and researchers, due to the fact that it requires less labor and investment than other livestock activities, as well as because of the productive qualities of quails. During the last decade, the nutritional habits of the population have changed. Restaurants and "churrasquerias" (Brazilian typical restaurants serving a variety of meats), have reported an increase in the consumption of quail eggs. According to the data registered by the Brazilian Institute of Geography and Statistics (IBGE), (2009), during years 2006 and 2007 a 25.8% variation in the production of quail eggs was given, going from 123.7 to 131.0 million dozens of eggs. In 2008, 157.8 million dozens were produced, with an increase of 20.4% with regards to 2007. The increase in productivity may be attributed to the use of new technologies pertaining to this activity and to both,  the better use of the infrastructure and the expertise of the industry in layers, regarding production and marketing.
At present, quails are grown in captivity, being the result of several crossings performed in Japan and in China, from the Coturnix coturnix, wild species of a European origin. In Brazil, these animals were brought into the country by Italian and Japanese immigrants during the decade of the 1950´s. Since then, their production has been consolidated, creating an alternative source of food intake for farm birds.
Quails present very similar physiologic characteristics to those of hens, hence that, in general, they are subjected to the same management practices with good results. In layers, the artificial light function in the lightening programs, in order to increase the photoperiod, stimulating egg production, considering that birds respond to the light stimulus is well known.
One of its main advantages is the high sexual precocity, starting laying at a much earlier stage. This is to say, egg production starts at a shorter period of time, guarantying a financial return for the producer. In birds, the reproductive organs in females are the ovary and the oviduct, as their primary function the production of a feasible progeny by means of fertile eggs (Gilbert, 1967). These organs are only developed in the left side of adult birds (King, 1986).
Eggs are one of the most complete food intakes for human beings, due to the fact that their composition includes proteins of an excellent biologic value, including most of the essential amino acids, vitamins and fatty acids (Austic and Nesheim, 1990).
In order to start laying, quails should have a total development of their gonads reaching sexual maturity. It is known that their reproduction age starts at day 42, even though this time has not been correctly defined. The objective of this work is that of analyzing the ovarian development, the presence of follicles and the size of the oviduct, in order to reach the egg production stage.

The work took place at the biochemistry laboratory of the Federal University of Santa María, CESNORS campus, located in the city of Palmeira das Missões, RS, Brazil, at South latitude of 27° 53' 58" and a West longitude of 53° 26' 45", at an altitude of 634 m over sea level.

One hundred quails were killed by cervical dislocation, during a 20 days period, five birds per day, until 100 analyses were obtained. During this period, quails were subjected to artificial light by means of two incandescent lamps of 150 watts each.

Birds were randomly selected for the daily slaughter and were evaluated regarding weight, size of the oviduct, presence or absence of the recruited follicle and number of follicles. The analysis of such factors was done as follows: individual slaughter, weight, photography with weight included, incision with surgical scissors, location and measurement of the oviduct, visual analysis of the presence or absence of the recruited follicle and number of visible follicles at mere sight, photography of the size and visual analysis.

Results obtained, indicate that during days 16 to 28 of age, quails presented no presence of preovulatory follicles in these quails. On day 29, a follicle development was observed in one of the five killed birds. This quail weighted 70.53 g, an oviduct length of 3.1 cm. At day 30th, the appearance of preovulatory follicles was observed, but at days 31 and 32, the presence of follicles was only observed in 20% of the evaluated quails. At day 33 of the analysis, the presence of 80% of the preovulatory follicles, in the total amount of the killed quails, with a mean weight of 86.78 g and an oviduct length of 2.9 cm, was detected. It was also observed that in birds follicle development, the size of the ovary was on more than 1 cm, while in quails without such a development, the size of the ovary was of less than 1 cm. Literature indicates that sexual maturity of quails happens between days 35 and 42. This is contrary to what we observed, because we detected such development at 29 days old, as indicated in Table 1, where we also present the means of all the quails during the days of the analysis.

Table 1. Different ages in which quails were observed

When comparing the data of the birds in which preovulatory follicles were found, with the general mean of the day, we can stress that data were only relevant during the final days of the evaluation, when a higher number of birds with preovulatory follicles were observed, even at day 35 with only 20%.

Table 2. Different ages in which quails were observed, including birds with development of the reproductive tract.

With these data, we can say that it would be mistaken to speak of 35 days, because before that day, we already saw an accentuated development in some of the evaluated birds, reaching an index of 80% of preovulatory follicles present. Hence, we can question the maturity phase under a constant photoperiod.

Another curious data is that at day 33, one of the quails, with a weight of 43.45 g presented preovulatory follicles, even with a considered low weight for the presence of follicles, but which was anyhow observed. This allows the idea that body weight does not interfere with sexual maturity of quails, but that the photoperiod does, even though it is true that body weight collaborates and is an important factor for layers, except for the fact that, in this instance, it did not interfere with the sexual maturity of birds, creating doubts regarding the individual performance of each bird.

Based on the results obtained, we conclude that, gonad development happens because of age and is not interfered by weight. The first follicles appeared at day 29. At day 33, more than the 80% of the evaluated birds presented development. Nonetheless, more detailed studies regarding the performance of each bird should be carried out, since each one responds in a different manner to the environment.

Austic RE & Nesheim MC. 1990. Poultry production. 13 ed. London: Lea Febiger.

Gilbert AB. 1967. Formation of the egg in the domestic chicken. pp. 111-180. In: Advances in Reproductive Physiology, vol 2. Mclaren A (ed.), Logos Press, London.

King AS. 1986. Aparelho urogenital das aves. pp.1813-1828. In: Sisson and Grossman's Anatomia dos Animais Domésticos, vol 2. Getty R (ed.) Interamericana, Rio de Janeiro.