HAEMATOLOGICAL STUDIES IN ADOLESCENT BREEDING COCKS

The objective of the study was to point out several significant changes in haematological values of male poultry occurring during sexual maturation and development of spermiogenesis using chickens (Gallus gallus domesticus L.) as a model species. The investigations were carried out in a set of 50 clinically normal breeding cockerels of the paternal line RIR-05 and covered the age span of 10 through 35 weeks. Blood samples collected at 5-week intervals from vena basilica were tested for total erythrocyte count (Er), packed cell volume (PCV), haemoglobin content (Hb), mean corpuscular haemoglobin concentration (MCHC), mean corpuscular haemoglobin content (MCH), mean erythrocytic volume (MCV), and total leukocyte (Le), basophil (Ba), eosinophil (Eo), neutrophil (Ne), lymphocyte (Ly), and monocyte (Mo) counts. Changes in the erythrocytic component observed during the investigation period included highly significant (P ≤ 0.01) increases in Er from 1,793 to 3,484 T ⋅ l-1, PCV from 0.243 to 0.435 l ⋅ l-1, and Hb from 69.94 to 136.57 g ⋅ l1. No significant changes were demonstrated for MCHC, MCH, and MCV in which mean values ranged from 26.17 to 31.53 l ⋅ l-1, from 36.39 to 44.20 pg, and from 125.61 to 157.86 fl, respectively. A reverse tendency was observed in the leukocytic component. Le decreased highly significantly (P ≤ 0.01) from 20.270 to 12.788 G ⋅ l-1. For this change, highly significant decreases in Ba from 0.138 to 0.065 G . l-1, Eo from 0.0-104 to 0.063 G ⋅ l-1, and mostly Ly from 11.502 to 3.784 g ⋅ l-1 (P ≤ 0.01) and Mo from 0.104 to 0.063 G ⋅ l-1 were responsible. Ne remained fairly constant varying within a narrow range of 7.742 to 8.626 G ⋅ l-1. The paper provides new comprehensive information on haematological changes occurring during sexual maturation of male breeding chickens up to the onset of reproductive activity.

(MCHC), mean haemoglobin content (MCH), and mean erythrocytic volume (MCV), and absence of age effects on the leukocytic component, was published by . Similarly, Straková et al. (1996) reported a marked increase in Hb, Er, and PCV in maturating male breeder turkeys. An increase in PCV during this period in male turkeys was described also by Cecil and Bakst (1993).

Materials and Methods
Fifty cockerels of the paternal line RIR 05, purchased at the age of 9 weeks from INTAGRA, Îabãice, were housed in deep litter pens and fed ad libitum with feed mixtures containing 153.5 crude protein and 11.8 MJ ME from the 10 th to the 18 th week of age and 185.3 crude protein and 12.4 MJ ME from the 19 th week of age.
Ambient temperature, lighting and other environmental conditions fully met the requirements laid down in the technological instructions for breeding poultry. Mean live weights of the birds at the age of 10,15,20,25,30, and 35 weeks were 0.89, 2.01, 2.52, 3.14, 2.84, and 3.34 kg, respectively.
Haematological values were determined in the period of sexual maturation from the 10 th to the 25 th week of age and in the period of sexual maturity in the 25 th and 30 th weeks of age using the methods described by H r u Blood samples were collected by puncture of v. basilica usually around 08.00 h at 5-week intervals at the age of 10, 15, 20, 25, 30, and 35 weeks. Total erythrocyte and leukocyte counts were determined using the haemocytometric method and the Natt-Herrick diluting solution. Hb was determined photometrically at 540 nm using the Drabkin solution and PCV by the capillary micromethod of Janetzki. Complementary indexes of the erythrocytic component, including MCHC, MVH, and MCV, were derived by calculation from the Er, Hb, and PCV values. Basophilic (Ba), neutrophilic (Ne), and eosinophilic (Eo) granulocytes, monocytes (Mo), and lymphocytes (Ly) were enumerated in blood smears prepared and stained panoptically with May-Grünwald and Giemsa-Romanowski immediately after sampling.
The results were processed using Student's ttest ( V enãikov and Venãikov 1977).

Results
The results of haematological examinations show significant changes occurring in the blood of breeding cocks during sexual maturation and at the onset of reproductive activity.
In the erythrocytic component, the changes included increases in total erythrocyte counts (Er), packed cell volume (PCV), and total haemoglobin content (Hb).
Er increased from the initial value of 1.793 T ⋅ l -1 at the age of 10 weeks to 3.484 T ⋅ l -1 at the age of 35 weeks. As can be seen in Table 1, all the between-week differences except that between weeks 25 and 30 were highly significant (P ≤ 0.01).
A similar tendency was observed for PCV which increased from the initial 0.243 l ⋅ l -1 in week 10 to 0.44 l ⋅ l -1 in week 30. All the between-week differences were highly significant (P ≤ 0.01).
The same, including the significance of differences, applied to Hb. Its mean values increased from the initial 69.94 g ⋅ l -1 in week 10 to 136.57 g ⋅ l -1 in week 35.
No significant changes were observed during the experimental period for MCHC, MCH, and MCV.
MCHC varied from 26.17 to 31.53 l ⋅ l -1 and similar variations were observed for MCH and MCV which fluctuated between 36.39 and 44.20 pg and 125.61 and 157.86 fl, respectively. (Table 1). Although some of the between-week differences for all the three values were significant (P ≤ 0.05) or highly significant (P ≤ 0.01), they cannot not be considered a phenomenon depending on age or sexual maturation.
Unlike Ba and Eo, Ne varied within a relatively narrow range of 7.742 to 8.626 G ⋅ l -1 . None of the between-week differences was significant ( Table 2).
The most marked changes during the period of sexual maturation were observed in Ly. The initial count of 11.502 G ⋅ l -1 (week 15) decreased to 3.784 G ⋅ l -1 (week 35). Highly significant differences were observed in weeks 20, 30, and 35 (Table 2).
Unlike other leukocyte types, Mo fluctuated atypically within the range of 0.063 to 0.104 G ⋅ l -1 . Although the differences between observed in weeks 15 and 30 were highly significant (P ≤ 0.01), they cannot be attributed to developmental changes occurring during the period of sexual maturation.

Discussion
The results of haematological studies in adolescent cocks demonstrate unambiguously that sexual maturation and the onset of reproductive activity were associated with significant physiological changes in the blood. The changes were characterised by intensive erythropoiesis apparent from increases in total erythrocyte counts, PCV, and haemoglobin content. Within the age span of 10 to 35 weeks, Er increased from 1.793 to 3.484 T ⋅ l -1 , PCV from 0.243 to 0.441 l ⋅ l -1 , and Hb from 69.94 to 136.57 g ⋅ l -1 . The continuous highly significant (P ≤ 0.01) rise of the three haematological indicators reaching almost double values at the end of the experimental period can be regarded as a phenomenon characteristic for the period of the gonadal and spermiogenetic development.
Results of haematological studies in poultry were published by several authors, such as Beuving et al. (1986), or McFarlane andCurtis (1989), but the first to describe such changes in the blood of cocks was . Although the above studies were conducted in relatively small sets of birds, their conclusions are the same as those arrived at in our investigations. In comparison with other authors, our experimental period was prolonged from the 25 th to the 35 th week of age.
Our results indicate that the changes in haematological values continue up to the age of 35 weeks, i.e. to the onset of reproductive activity associated with intensive spermiogenesis. Our data probably apply also to males of other poultry species, because similar results were published also by Straková et al. (1994) for Japanese quails and Cecil and Bakst (1993) and Straková et al. (1996) for breeding turkeys.
Unlike the absence of changes in the leukocytic component reported by , our results indicate changes in leukocyte counts occurring during the period of sexual maturation and the onset of reproductive activity. This discrepancy may have been due to differences in group sizes and the fact that in our study the age span was extended from 25 to 35 weeks and that the most marked changes in leukopoiesis were observed during the last ten weeks. Thus, for the whole experimental period Le decreased from 20.114 to 12.788 G ⋅ l -1 , the differences being highly significant (P ≤ 0.01) in weeks 20 and 30. Although Ba and Mo also decreased highly significantly (P ≤ 0.01) in weeks 20 and 30, mostly responsible for the change in Le were highly significant (P ≤ 0.01) decreases in Ly in weeks 20, 30, and 35.
Remarkably, Ne fluctuated within a relatively narrow range of 7.742 -8.626 G ⋅ l -1 throughout the experimental period.
It can be concluded that the results presented here throw light on some hitherto lesser known haematological changes occurring during the period of sexual maturation of and at the onset of reproductive activity in breeding cocks and thus extend the current knowledge of avian haematology.