LEVELS OF PLASMA TESTOSTERONE IN GANDERS AS RELATED TO EGG FERTILIZATION RATE

Lazar, V. P. Jelinek, J. Picha, Drahomira Pichova: Levels oj Plasma Testosterone in Ganders as related to Egg Fertilization Rate. Acta vet. Brno 53, 1984: 151-158. Testosterone levels in the blood plasma were studied in four strains of ganders of the parent combination of the I vagees hybrid in the course of the autumn reproduction period (2nd laying cycle). Testosterone was determined by radioimmunoassay using 1251 testosterone as a radioactive ligand. The average concentration of testosterone ranged between 2.93 and 14 81 nmol. 1-1 with a high variability in the individual samplings. In the period of intensive egg laying the relationship was investigated between the level of testosterone in the plasma and fertilization rate of the egg set. In the group of ganders under study, correlation coefficient r = 0.790+ was found. Various levels and tighmesses of the relationship between testosterone level and egg fertilization rate (r = 0.859++; r = 0.594; r = 0.687+) were recorded in the individual strains. Geese, testosterone, RIA method, Jertility rate oj eggs. The introduction of a two-cycle egg laying in one year prolonged the egg laying period and thus also increased the number of hatching eggs. However, in large breeds, egg laying and fertilization rate are not always in accordance. It is a very important problem which, according to some authors (e. g. Ballay 1975), follows from the fact that the egg laying period in geese was prolonged but that ganders did not adapt enough to this change. That is why methods are searched to evaluate the fertility of ganders. One of these methods is the evaluation of testosterone concentrations in blood which widens the present knowledge and enables to judge the endocrine functions of the gonads contributing to a deeper knowledge of regulatory mechanisms in gander reproduction. There are not many literary data about testosterone levels in geese. Dittami (1981) studied the behaviour of wild geese in relation to the hormone level in blood (inc!. testosterone). Kosutzky et a!. (1982b) investigated the dynamics of average levels of testosterone in blood plasma during the period from November till September. During this period the testosterone levels had a bi-phasic character with values ranging from 0.82 to 9.59 nmol . 1-1• The authors did not prove any relationship between the development of the penis and testosterone levels in blood plasma. In their previous study, the present authors (Lazar et a!. 1981) observed an increase in the testosterone level in blood plasma of ganders during rearing (1217 days of age) ranging from 1.504 to 28.793 nmol.I-1. The observed results about the testosterone levels in blood plasma of ganders and their biphasic culmination are essentially in accordance with other literary data (Kosutzky et al. 1982b). J allageas and Assenmacher (1974) found that in the blood plasma of ganders during the year there was a spring peak of testosterone (March and April) and another one in August and September. Tanabe et al. (1981) proved changes in the testosterone levels in cockerels of the age of 28 to 1141 days as well. The first peak oftestosterone concentration appeared at the age of 207 days (3.62 mg/ml), then the levels ranged between 1 and 3 mg/ml. Lofts (1975) stated that the sec-

The introduction of a two-cycle egg laying in one year prolonged the egg laying period and thus also increased the number of hatching eggs.However, in large breeds, egg laying and fertilization rate are not always in accordance.It is a very important problem which, according to some authors (e. g.Ballay 1975), follows from the fact that the egg laying period in geese was prolonged but that ganders did not adapt enough to this change.That is why methods are searched to evaluate the fertility of ganders.One of these methods is the evaluation of testosterone concentrations in blood which widens the present knowledge and enables to judge the endocrine functions of the gonads contributing to a deeper knowledge of regulatory mechanisms in gander reproduction.
There are not many literary data about testosterone levels in geese.Dittami (1981) studied the behaviour of wild geese in relation to the hormone level in blood (inc!. testosterone).Kosutzky et a!. (1982b) investigated the dynamics of average levels of testosterone in blood plasma during the period from November till September.During this period the testosterone levels had a bi--phasic character with values ranging from 0.82 to 9.59 nmol .1-1 • The authors did not prove any relationship between the development of the penis and testosterone levels in blood plasma.In their previous study, the present authors (Lazar et a!. 1981) observed an increase in the testosterone level in blood plasma of ganders during rearing (1-217 days of age) ranging from 1.504 to 28.793 nmol.I-1.
The observed results about the testosterone levels in blood plasma of ganders and their biphasic culmination are essentially in accordance with other literary data (Kosutzky et al. 1982b). J allageas andAssenmacher (1974) found that in the blood plasma of ganders during the year there was a spring peak of testosterone (March and April) and another one in August and September.Tanabe et al. (1981) proved changes in the testosterone levels in cockerels of the age of 28 to 1141 days as well.The first peak oftestosterone concentration appeared at the age of 207 days (3.62 mg/ml), then the levels ranged between 1 and 3 mg/ml.Lofts (1975) stated that the sec-retion rhythm of testosterone was probably genetically conditioned in the majority of avian species.Zeman (1981) reported that the changes in testosterone levels in poultry males preceeded in time the changes of the semen quality.

Materials and Methods
In the present study, four strains of the parent combination of geese of the Ivagees hybrid were used (ratio 16: 5 ~).In the course of rearing the parametres of bird density, microclimatic factors and nutritional level were observed, corresponding to requirements determined for the rearing period of geese.Egg fertilization rate was studied during hatching in BA-134 hatchers.
The experimental period lasted from August 20 till January 27, and in the period of intensive egg laying, i. e. from October 19 till December 8, the relationship was studied between the testosterone concentration in the blood plasma of ganders and the fertilization rate of geese eggs.In the period under study, 13 blood samplings were performed in each gander for determinations of basal levels of testosterone and the resulting relationship was evaluated from 8 samplings and 8 egg sets.Blood samples were taken always in the time interval between 10 and 12 hours.

Results and Discussion
The basal levels of plasma testosterone in gander during the period from August to January are given in Tab. 1.The range of mean values (5.05-14.14nmol.l-l) is higher than that given by Kosutzky et al. (1982b) during the period from November to September.The high values of the coefficient of correlation show that there are individual differences among the ganders and that the course is biphasic with regard to the time intervals investigated.In Tab. 1 and Figs.1-5, certain phases of culmination of testosterone concentrations in blood plasma are evident.In the strains of the group of ganders studied (Fig. 1) a biphasic culmination with peaks at the beginning of September and the beginning of November appeared, similarly as in the investigations of Kosutzky et al. (1982).Despite the different period of investigations and different conditions of the environment (in the present study a stimulation light regime as compared with a naturallight regime of other authors), the culmination of testosterone in blood plasma in the autumn, i. e. in August and September,is the same as observed by J alla-       geas and Assenmacher; (1974) and Kosutzky et al. (1982b).The different secretion rhythm of testosterone in the individual ganders can probably be explained by the findings of Lofts (1975).
In the graphic illustrations of the changes of testosterone concentrations in the blood plasma and of the fertilization rate of egg sets (Figs.1-5) it is evident that there is a certain relationship between these factors.This relationship is proved in the level of coefficients of correlation and regression straight lines given in Tab. 2 and Tab. 3. It is evident that the tightness of the relationship increased with the "quality of the gander", e. g. in gander 1/3004 in the period studied the average testosterone concentration was found to be 14.81 nmol.I-1 and the average fertilization rate of eggs was 85.29 % which is reflected in the value of the coefficient of correlation quoted by Zeman (1981).
Even though the present results are only of an orientation character, especially in connection with the limited number of investigations and in spite of the complexity of regulatory mechanisms on which the level of testosterone in plasma depends, it is evident that the analysis of hormonal relationships is a perspective parameter utilizable in modem poultry rearing.

Fig. 1 .
Fig. 1.Summarized values of testosterone concentration in the investigated group of ganders and egg fertilization rate.

Table 2 155
Summarized statistical characteristics and correlation analysis of testosterone concentration in the group of ganders under study (for the period from October 19 till December 8) and egg fertilization rate y' = 60.11+ 2.12 x o ... .. ...

Table 3
Summarized statistical characteristics and correlation analysis of testosterone concentration in the individual ganders (for the period October 19 till December 18) and egg fertilization rate