Veterinary and Animal Science 6 (2018) 41–49
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Veterinary and Animal Science
journal homepage: www.elsevier.com/locate/vas
Age-related changes in the gross anatomy of the reproductive organs, and T
associated steroid hormone profiles in male and female guinea fowls
(Numida meleagris)
Ibn Iddriss Abdul-Rahmana,⁎, Ian Jeffcoateb, Frederick Yeboah Obesec
a Department of Veterinary Science, Faculty of Agriculture, University for Development Studies, P. O. Box TL 1882, Nyankpala Campus, Tamale, Ghana
b Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Bearsden Road, Glasgow,
Scotland G61 1QH, UK
c Department of Animal Science, School of Agriculture, University of Ghana, P. O. Box LG 226, Legon, Ghana
A B S T R A C T
Owing to the paucity of information on the reproductive biology of guinea fowls, a study involving a total of 132 birds was conducted, and this documented the
developmental changes in the gross anatomy of the reproductive organs of males and females from hatching until 32 weeks of age (WOA), and associated steroid
hormone changes. Testicular anatomical biometric traits increased significantly (p<0.0001) from 8 WOA, and stabilised between 16 and 20 WOA, while peripheral
testosterone concentration peaked at 20 WOA. Correlations among all testicular biometric characteristics were strong and positive (p<0.0001). Similarly peripheral
testosterone concentrations strongly (p<0.01) and positively correlated with all the testicular anatomical biometric traits. In the female guinea fowl, the ovary and
oviduct were discernible and measurable at hatching. Significant (p<0.0001) increases were seen in ovarian and relative ovarian weights, and oviducal weights and
lengths between 24 and 28 WOA. Plasma 17β-oestradiol decreased gradually to a very minimum at 16 WOA, and then began to increase gradually until 28 WOA
when it plateaued. Peripheral progesterone concentrations on the other hand increased gradually from 4 WOA and peaked at 12 WOA, and then fluctuated con-
siderably thereafter. Correlations among ovarian/oviducal anatomical parameters were strong (p<0.0001) and positive. Similarly, peripheral oestradiol con-
centrations strongly (p<0.0001) and positively correlated with all ovarian/oviducal anatomical parameters. Testicular anatomical biometric traits stabilised be-
tween 16 and 20 WOA, coinciding with peak peripheral testosterone concentrations, while ovarian/oviducal parameters recorded huge increases between 24 and 28
WOA, and may be under the influence of oestradiol.
1. Introduction of sexual maturity in the White Leghorn. It has also been shown that the
weight of the testes of the fowl varies according to breed (Kumaran &
The male bird possesses paired reproductive tracts lying along the Turner, 1949a, 1949b).
dorsal body wall (Kirby & Froman, 2000). Each tract consists of a testis, Age-related differences in testis size may result from younger birds
weighing between 0.32 and 2.0 g, and 14 and 60 g in guinea secreting less gonadotropins than older birds (Ketterson & Nolan, 1992;
(Awotwi, 1975) and domestic (Lake, 1971) cocks, respectively, de- Silverin, Kikuchi, & Ishii, 1997), but whether testicular sensitivity to
pending on the breed, an epididymis, and a highly convoluted deferent these hormones is also age-dependent is unknown. Age-dependent
duct running alongside the ureter (Lake, 1971). In terms of testicular differences in mean and maximal testis size may account for lower
mass, Awotwi (1975) identified 4 phases of testicular growth in the plasma testosterone in younger adult males compared with older males
local guinea fowls (Numida meleagris) These include periods of rapid (Deviche & Sharp, 2001; Deviche, Wingfield, & Sharp, 2000; Sorenson,
growth, spanning between 8 to 16 WOA; slow growth (20–28 WOA); Nolan, Brown, Derrickson, & Monfort, 1997). Testes in testosterone-
rapid growth (28–32 WOA); and finally, almost static growth after 32 treated hypophysectomized immature quail remain undeveloped, but
WOA. Brillard's (1986) report on the guinea fowl, however, demon- increase in size when birds also receive luteinizing hormone (LH) and,
strated only 2 phases: initial phase of rapid growth (8–20 WOA) and especially, follicle stimulating hormone (FSH) (Brown & Follett, 1977).
one of static growth after 20 WOA. Bennet (1947) found a definite This observation provides no evidence for a role for testosterone in
relationship between testes size and age of White Leghorns up to the 6th regulating testicular development. However, a role for testosterone in
month of age (sexual maturity). This suggests factors other than age adult testicular function is suggested by the finding in mature hypo-
may play a role in the determination of gonad size after the attainment physectomized quail that administration of large doses of testosterone,
⁎ Corresponding author.
E-mail address: Ibniddriss@uds.edu.gh (I.I. Abdul-Rahman).
https://doi.org/10.1016/j.vas.2018.07.003
Received 12 July 2017; Received in revised form 22 July 2018; Accepted 26 July 2018
Available online 27 July 2018
2451-943X/ © 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license 
(http://creativecommons.org/licenses/BY-NC-ND/4.0/).
I.I. Abdul-Rahman et al. Veterinary and Animal Science 6 (2018) 41–49
while insufficient to maintain spermatogenesis, retards testicular re- 2.2. Animals and management
gression resulting from the surgery (Brown & Follett, 1977).
The normal, functional gonad of the hen is the left ovary. It is an A total of 132 local guinea fowls (Numida meleagris), of the pearl
irregularly shaped, pinkish organ which is situated on the left side of variety, were used for the study. Birds were brooded for 6 WOA (Teye &
the abdominal cavity close to the median line (Deol, 1955). A right Gyawu, 2002), and then transferred to a deep litter house until the end
ovary is present as a rudiment at hatching, but this decreases in size and of the experiment. They were individually identified using tags placed
persists throughout life only as an inconspicuous vestige through their inner wings to prevent detection by other birds and thus
(Hodges, 1974). In the guinea fowl, Awotwi (1975) reported a steady avoid pecking. Keets were brooded at 35 °C from hatching until three
increase in ovarian weight from 0.04 g at 4 WOA to 30.5 g at sexual (WOA), and then at 32 °C until six WOA (Teye & Gyawu, 2002). Birds
maturity (36 WOA); this regressed to 2.7 g in non-breeding-hens were then maintained at ambient temperatures of between 22 °C and
(Abdul-Rahman, Obese, Robinson, Awumbila, & Jeffcoate, 2016a). The 35 °C until the end of the experiment. Feed and water were supplied ad
reports of Romanoff and Romanoff (1949) indicated that at day old, the libitum. Day old keets were fed ground maize in flat feeders followed by
ovary of a chick weighed 0.03 g. This increased to 0.32 g, 2.66 g, 6.55 g a starter ration from day 2 until 6 WOA. This was followed by a grower
and 38.0 g at 3, 4, 5 months and after pullet had laid the first egg, ration from 6 WOA until 21 WOA and then a layer feed until the end of
respectively. Chaikoff, Lorenz, and Entenman (1941) observed that this the experiment. The starter (22% crude protein and 3000 Kcal ME/kg
steady increase in ovarian weight decreased to about 5 g after the hen diet), grower (14% crude protein and 2800 Kcal ME/kg diet), and
had ceased laying. Similar observation was made by Hafez and breeder (17.5% crude protein and 2800 Kcal ME/kg diet) rations were
Kamar (1955) in Fayomi chicks; these authors, however, noted that the obtained from a commercial feed supplier (Agricare Ghana Limited,
developmental changes in this organ were more marked just prior to Kumasi, Ghana).
sexual maturity than at any other time. Information on lighting requirements of the local guinea fowls from
The increase in progesterone concentrations 6–4 h before ovulation hatching are unavailable, and those used for chicken, are usually em-
(Bacon et al., 2002; Etches, 1990) is predominantly the result of in- ployed. In this case, however, the “golden rule” to follow in designing
creased secretion by the largest preovulatory follicle (Etches, 1990). lighting programmes for pullets (Thiele, 2009) was followed. All birds
Similarly, preovulatory follicle secretion of oestradiol increases in each received 24 h light from day old until one-WOA, and this was reduced
of the four largest follicles 6–3 h prior to ovulation and is greatest in the to 16 h until birds were 3 WOA. These longer light periods during the
third- and fourth-largest follicles. Overall, however, the majority of first 3 weeks of life were to ensure maximum feed consumption, enough
oestrogen produced by the ovary originates from prehierarchal follicles to ensure maximum growth, initially. This was gradually reduced to a
(Johnson, 2000). Oestrogens, together with progesterone, are required minimum of 13 h, marking the phase of constant light, since no increase
for priming of the hypothalamus and pituitary in order that proges- in day length is recommended until the phase of planned light stimu-
terone can induce LH release (Wilson & Sharp, 1976). lation is reached (Thiele, 2009). The phase of planned light stimulation
Several studies have documented age-related variation in testis size, was identified by the onset of lay in two female birds at 21 WOA. This
with older adults generally having larger testes than younger adults could not be planned earlier because laying age in these birds vary
(Deviche et al., 2000; Graves, 2004; Hill, 1994; Laskemoen, Fossoy, considerably (Awotwi, 1987). At this age, lights were gradually ad-
Rudolfsen, & Lifjeld, 2008; Morton, Peterson, Burns, & Allan, 1990; justed to 14 h using incandescent bulbs (10 lx) to adjust the day length
Selander & Hauser, 1965). A preliminary study by Awotwi (1975) re- by 2 h during the dark period.
ported age related changes in testicular and ovarian mass in the guinea
fowl, these were not detailed, and involved small sample size 2.3. Experimental procedure
(Awotwi, 1975). Steroid hormone synthesis in these birds during sexual
development has also not been reported. Besides, there is a general All procedures used followed approved guidelines for ethical
paucity of information on the reproductive system of guinea fowls. The treatment of experimental animals.
objective of the present study, therefore, was to document the devel- A total of 112 (56 per sex) guinea fowls (14 per age group; 7 per sex)
opmental changes in gross anatomy of the reproductive organs of male were bled at 4, 8, 12, 16, 20, 24, 28, and 32 WOA. Two ml of blood was
and female guinea fowls from hatching until adulthood (32 WOA), and collected into EDTA vacutainer tubes from the wing vein, and spun at
associated steroid hormone changes. 7100 g for 3min at room temperature (18–25 °C). Plasma was then
pipetted into a 1.5 ml microcentrifuge tube and stored at –20 °C until
subsequently analysed for testosterone in males, and oestardiol and
2. Materials and methods progesterone in females.
Prior to bleeding, however, 10 birds at each age (5 per sex) were
2.1. Experimental site weighed, and then following bleeding, were sacrificed by cervical dis-
location. Their testes/ovaries and reproductive tracts were completely
The study was conducted at the Poultry Unit of the Department of freed from the adjoining ligaments and fascia, weighed and measure-
Animal Science, University for Development Studies, Nyanpkala, ments taken.
Tamale (Ghana). Nyanpkala lies on latitude 9° 69′N and longitude 0°
83′W. Temperatures are generally high with minimum and maximum 2.3.1. Gross anatomical and peripheral testosterone measurements in the
values of 22 °C and 35 °C recorded in March and December, respectively male
(Savannah Agricultural Research Institute, SARI, Unpublished). Rainfall Testicular length, width and height were measured using calipers
is monomial with mean annual rainfall varying from 1000 to 1500mm and recorded to the nearest 0.1 mm. Testicular volume was estimated
and peaks from August to September, with a relatively long dry season using the formula for a prolated spheroid as follows: V=4/3π (1/2 L)
extending from November to April. The area lies in the Guinea (1/2W)2 (Ramirez-Bautista & Gutierrez-Mayen, 2003) and recorded to
Savannah zone. The zone has nearly equal amounts of light and dark- the nearest 0.1 cm3. Testicular weights were taken with a Mettler
ness (12L:12D) within a 24 h period throughout the year. The guinea electronic scale and recorded to the nearest 0.1mg. Relative testes
fowl used in the present study is native to this location, and breeds weight was also calculated as the ratio of testes to body weight. Length
more intensely between April and August during rainy season, and of ductus deferens was measured as the distance from the point of at-
declines when the season is receding between August and October tachment of the ductus to the epididymal region until it entered the
(Abdul-Rahman, Robinson, Obese, Jeffcoate, & Awumbila, 2016b). connective tissue of the internal part of the cloaca on either sides of the
large intestine and ureters, using a ruler and recorded to the nearest
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I.I. Abdul-Rahman et al. Veterinary and Animal Science 6 (2018) 41–49
Fig. 1. Reproductive tracts of sexually mature (A) and 8 week old (B) male guinea fowls (in-situ), showing the left testes (LT), right testes (RT), left (arrowed) and
right (arrow head) ductus deferens.
0.1 cm. Finally, qualitative changes including change in colour of the validated for guinea fowl (Abdul-Rahman et al., 2016a). Using the
testes were observed and recorded. Total reading for a parameter per Oestradiol Maia kit (RADIM diagnostics, USA), all samples were eval-
testis was presented as average for the 2 testes (i. e left testis uated in one assay, and intraassay CV was 9.8%. The assay sensitivity
reading+ right testis reading/2). was 5.2 pg/ml. For progesterone concentrations determination, no va-
The testosterone assay had been previously validated for guinea lidation was required since it had been previously measured in the
fowl (Abdul-Rahman et al., 2016b). The assay was a RIA using tritiated guinea fowl (Onyeanusi, 2007). The Coat-A-Count® Progesterone kit
tracer (Amersham Int., Amersham, Bucks, UK) and a procedure as (Siemens Healthcare Diagnostics, USA) was used for determining pro-
originally described by Sheffield and O'Shaughnessy (1989). The tes- gesterone concentrations. The plasma progesterone concentrations in
tosterone antibody was obtained from Guildhay Antisera, Surrey, UK. all samples were determined in one assay, and the intra-assay CV was
The detection limit was 0.06 ng/ml, and intra-assay coefficient of var- 7.1%. The sensitivity of the assay was 0.08 ng/ml.
iation was 9.5%. Cross reactivity with androstenedione and androsta-
nediol were 0.3% and 3.9%, respectively. The assays were performed 2.4. Statistical analysis
after sample extraction using diethyl ether in duplicate of 50 μl ali-
quots. Peripheral testosterone concentrations in all the samples assayed Data were analysed using the SPSS software, version 20
were determined using the standard curve generated by the Assayzap (IBM, 2011). The data were evaluated for normality of variance and
software (Biosoft®, USA). All samples were evaluated for testosterone in homogeneity using the Shapiro-Wilk's W and Levene's tests, respec-
one assay. tively. Age-related changes in gross anatomy of reproductive organs of
male and female, and associated peripheral steroid hormone con-
2.3.2. Gross anatomical, peripheral progesterone and 17β-oestradiol centrations were analysed using univariate analysis for completely
measurements in the female randomised design and means separated using tukey's test. Where
Ovarian and oviduct weights were taken on a Mettler electronic variances were not homogenous, Kruskal–Wallis test was used instead
scale and recorded to the nearest 0.001 g and 0.01 g, respectively. and medians separated using Mann–Whitney U test. Data were pre-
Relative ovarian weight was calculated from the ratio of ovarian to sented either as mean ± standard error of mean or median (Inter-
body weight. Length of oviduct was also measured with a ruler/flexible quartile range). Correlations among most of the variables measured
tape and recorded to the nearest 0.1 cm. At sexual maturity, lengths and were also determined where appropriate. All comparisons were done at
widths of the various regions (identified on the basis of differences in 5% level of significance.
widths of the various regions, Romanoff & Romanoff, 1949) of the
oviduct were taken, namely, the infundibulm, magnum, isthmus, va- 3. Results
gina and uterus. Also, numbers and diameters of visible oocytes in
breeding birds were determined. Oocytes were categorised into F1 to F7 3.1. Gross anatomy of male reproductive tract and peripheral testosterone
for yellow follicles, F1 denoting the biggest yellow follicle and F7 the profiles
smallest. White follicles were also categorised into small
(<1mm–3mm), medium (>3mm–6mm) and large (>6–8mm) folli- The paired reproductive tracts of the guinea fowl consist of testes
cles (Romanoff & Romanoff, 1949). Also, qualitative changes including and highly convoluted vas deferens. After hatching, the testes and vas
change in colour and shape of the ovary were observed and recorded. deferens are not discernible until about 4 WOA. At this age, the testes
As with testosterone, 17β-oestradiol assay had also been previously are seen as thickenings on the upper parts of their respective vas
43
I.I. Abdul-Rahman et al. Veterinary and Animal Science 6 (2018) 41–49
Table 1
Developmental changes in testicular anatomical traits and peripheral testosterone concentrations in male local guinea fowls.
Testicular Anatomical
trait
{Median (Interquartile AGE (Weeks)
range)}
4 8 12 16 20 24 28 32
Testicular weight (mg) – 5.0 38.5 94.5 192.5 170.5 367.5 351
(2.8–7.8)e (23.0–91.5)d (82.5–133.5)c (131.5–241.3)b (86.5–304.5)bc (226.1–428.6)a (246.0–408.5)a
Gonadosomatic index (x10−4) – 0.8 1.0 3.0 4.5 4.0 6.0 5.0
(GSI (0.3–1.0)c (1.0–3.0)b (3.0–4.0)a (2.8–5.5)a (3.0–8.0)a (4.0–7.0)a (4.0–7.0)a
Testicular volume (Cm3) – 0.01 0.04 0.13 0.25 0.21 0.38 0.38
(0.005–0.014)d (0.04–0.13)c (0.11–0.20)bc (0.16–0.31)ab (0.12–0.38)ab (0.23–0.49)a (0.30–0.46)a
Testicular width (mm) – 1.9 3.6 4.8 6.1 (5.3–6.9)ab 6.2 7.2 7.4
(1.6–2.1)d (3.3–4.9)c (4.7–5.7)b (4.7–7.4)ab (6.3–7.9)a (6.4–7.8)a
Testicular height (mm) – 1.3 3.0 4.0 4.9 4.4 6.0 6.0
(1.0–1.5)e (2.6–0.9)d (3.7–4.1)cd (4.1–5.5)b (3.6–6.3)bc (5.3–6.8)a (5.9–6.8)a
*Testicular length (mm) – 4.6 ± 0.6d 7.4 ± 0.5c 9.9 ± 0.5b 12.0 ± 0.6ab 11.1 ± 0.5ab 13.2 ± 0.6a 13.3 ± 0.5a
*Testosterone (ng/ml) 0.09 ± 0.04c 0.12 ± 0.04bc 0.19 ± 0.04abc 0.26 ± 0.04ab 0.28 ± 0.04a 0.16 ± 0.04abc 0.17 ± 0.037abc 0.18 ± 0.037abc
concentration
Means/Medians (Interquartile range) within a row having no superscript in common are significantly (p<0.05) different. *Mean ± SEM. –: Testis appeared just as a
thickening at this age and could not be detached for any measurement.
deferens, but cannot be detached for weighing or good histological that seen at 12 WOA and remained at that level until the end of the
section. The vas deferens can, however, be measured at this age. In this study. Correlations among all testicular biometric characteristics were
study the testes were first detached for measurement at 8 WOA. They positive and highly significant (p<0.0001). Similarly, correlations
were bean shaped and creamy in colour (Fig. 1). between all testicular anatomical characteristics, testicular weight and
Developmental changes in testicular anatomical traits and periph- peripheral testosterone concentration were positive and highly sig-
eral testosterone concentrations in male guinea fowls are presented in nificant (p<0.0001; Table 2).
Table 1. Generally, testicular weight increased significantly (Kruskal–-
Wallis test X2= 35.506, df= 6, p<0.0001) from 8 until 20 WOA, and 3.2. Gross anatomy of female reproductive tract and peripheral steroid
between 24 and 28 WOA. Similarly, gonadosomatic index, which is the hormone profiles
relative investment into testicular growth increased significantly
(Kruskal–Wallis test X2= 26.633, df= 6, p<0.0001) between 8 and The ovary and oviduct of the guinea fowl are discernible and
16 WOA, and remained constant thereafter. Testicular volume, on the
2 measurable at hatching. The ovary was visible as a whitish-creamother hand, increased significantly (Kruskal–Wallis test X =34.113, crescent-shaped organ from hatching until about 16 WOA when it was a
df= 6, p<0.0001) between 8 and 12 WOA, and was maintained until creamy L-shaped organ. The grape-like appearance began to manifest
16 WOA. From 12 WOA onward, no statistical (p>0.05) differences from 20 WOA and by 27th to 28th WOA, the ovary had completely
were noticed between any adjacent age groups, the cumulative increase assumed the ‘grape cluster’ appearance. Yellow follicles emerged after
between 12 and 20 WOA was significant (p<0.05). Similarly, 28 and 26 WOA (Fig. 3). Except for 2 birds which laid exactly at 21 WOA, all
32 week old birds had significantly higher (p<0.05) testicular volume birds laid between 27 and 28 WOA, marking the onset of sexual ma-
than 16 week old birds. Generally from 20 WOA, no significant turity in these birds.
(p>0.05) increase in testicular volume was noticed. Age-related changes in ovarian/oviducal anatomical parameters
A significant rise was noticed in testicular width (Kruskal–Wallis
2 and peripheral steroid hormone concentrations in guinea hens aretest X =33.297, df= 6, p<0.0001) from 8 until 16 WOA. Even shown in Table 3. The ovary increased significantly (Kruskal–Wallis test
though no differences (p>0.05) in width were noticed between any X2= 56.411, df= 8, p<0.0001) in weight between 1 and 4, 8–12,
adjacent age groups from 16 WOA, cumulatively, the increase between 12–16, and 16–20 WOA. This would coincide with the end of first phase
16 and 28 weeks was significant (p<0.05). Testicular height, on the of follicular growth. Ovarian weight then remained unchanged until 24
other hand, showed inconsistent growth pattern. This biometric trait
2 WOA. From this age, there was a highly significant (p<0.0001) in-increased significantly (Kruskal–Wallis test X =32.301, df= 6, crease in ovarian weight from 0.324 (0.293–0.433) g to 17.2
p<0.0001) between 8 and 12, 16 and 20 and 24 and 28 WOA. (14.8–21.2) g at sexual maturity (28 weeks). Relative ovarian weight on
Testicular length showed similar growth pattern as width. A significant the other hand showed a different pattern of growth. It decreased sig-
increase (p<0.05) was noticed in length between 8 and 16 WOA. Also, nificantly (p<0.05) between 4 and 8 WOA before returning to ap-
the cumulative increase between 16 and 28 weeks was significant proximately the 4 week level at 12 WOA, where it remained until 28
(p<0.05). WOA where a highly significant (p<0.0001) increase in relative
Unlike other traits of the male reproductive organs, initial suspen- weight was seen.
sion of growth occurred much earlier in the vas deferens. This organ As with the ovary, increases in length and weight of the oviduct
increased significantly (p<0.05) in length between 4 and 8 WOA, were also not consistent. Oviduct length increased significantly
remained unchanged thereafter (p>0.05) until puberty (12 WOA) and (Kruskal–Wallis test X2= 49.513, df= 7, p<0.0001) between 4 and 8,
increased (p <0.05) again between 12 and 16 WOA. No change was and 12 and 16 WOA, with a final increase from 9.6 (8.2–12) cm at 24
recorded in the length of the duct thereafter (Fig. 2). WOA to 45 (40.5–56) cm at 28 WOA. Similarly, oviduct weight did not
Peripheral testosterone concentration tended to increase from 4 to change significantly with age until 12 WOA, with a significant cumu-
20 WOA when it peaked. Testosterone levels at sexual maturity (16 lative increase between 8 and 16 WOA. It then increased significantly
WOA) were significantly higher (p<0.05) than the levels in 4-week old (p<0.05) between 16 and 20 WOA, and again at 28 WOA from 0.640
birds. Similarly, the peak testosterone concentrations at 20 WOA were (0.175–1.810) g to 17.4 (14.3–24.2) g.
higher (p<0.05) than the concentrations at 4 and 8 WOA. Peripheral 17β-oestradiol concentration did not change appreciably
Testosterone concentration decreased after 20 WOA to a level similar to between 4 and 20 WOA. The levels at 4 WOA, however, were higher
44
I.I. Abdul-Rahman et al. Veterinary and Animal Science 6 (2018) 41–49
Fig. 2. Age-related changes in length of ductus deferens in local guinea fowls.
(p<0.05) than those at 12, 16 and 20 WOA. Peripheral oestradiol parameters were highly significant (p<0.0001) and positive.
concentrations increased significantly (p<0.05) from 20 WOA, Peripheral progesterone concentrations, on the other hand, were in-
reaching a peak {57.1 (36.6–103.4) pg/ ml} at 28 WOA before a slight significantly (p>0.05) correlated with all the oviducal/ovarian ana-
decline at 32 WOA. Progesterone concentrations were relatively con- tomical parameters (Table 6).
stant between 4 and 12 WOA, and then tended to decrease (p>0.05)
between 12 and 16 WOA. The concentrations at 8 WOA were sig- 4. Discussion
nificantly higher (p<0.05) than those at 16 and 20 WOA. Between 16
and 20 WOA, peripheral progesterone concentration dropped sig- 4.1. Gross anatomy of male reproductive tract
nificantly (p<0.05) to minimal levels. This was followed by a sig-
nificant (p<0.05) increase between 20 and 32 WOA. As reported by other workers (Awotwi, 1975; Brillard, 1986;
The number of visible oocytes in the ovary of breeding guinea hens Brillard & de Reviers, 1981), testes of a growing guinea cock could only
ranged from 92 to 177 and averaged 127. Oocytes ranging in diameter be detached for measurements from 8 WOA. Testicular weight in-
between 3mm and below (small white follicles) were the dominant creased until 20 WOA, and remained stable thereafter. This is similar to
(107) while those ranging between over 6 and 8mm (large white fol- the reports of Brillard and de Reviers (1981) and Brillard (1986) in the
licles) were the least (Table 4). exotic breeds of guinea fowl. The authors indicated that this marked the
No adjacent pre-ovulatory follicles in the ovary differed sig- commencement of adulthood in those birds. In the local guinea fowl,
nificantly (p>0.05) in diameter. However, a significant (p<0.05) however, despite the stablisatioin of testicular weight from 20 weeks,
yolk accumulation occurred between F7 and F4, F6 and F3, F5 and F3, fully formed spermatozoa was first seen both in the tubular lumen and
F4 and F2, and, F3 and F1. Generally, significant (p<0.05) yolk de- epididymal region at 16 WOA (Abdul-Rahman, 2013), indicating earlier
positions in the pre- ovulatory follicles took 3 days up to F7 and F6, and commencement of sexual activity in these birds. Several studies also
2 days up to F5, F4 and F3 (Fig. 4). reported bigger testes in older than younger birds (Deviche et al., 2000;
Variations in the lengths and widths of the various sections of the Graves, 2004; Hill, 1994; Laskemoen et al., 2008; Morton et al., 1990).
oviduct and cloaca in sexually mature birds in breeding condition are The increase in testicular weight with increasing age may be attribu-
presented in Table 5. Generally, the various sections varied in length. table to higher secretion of gonadotropins in older than younger birds
The longest section of the oviduct was the magnum {18.5 (16–20) cm}, (Ketterson & Nolan, 1992; Silverin et al., 1997). Gonadosomatic index,
forming about 40% of the entire duct. This was closely followed by the which is the relative investment into testicular growth, stablised from
isthmus, the infundibulum and uterus, and finally the vagina, which is 16 WOA. This is possibly because this coincides with the age at sexual
the shortest. The cloaca was much shorter than any other part of the maturity and, therefore, no further investment into testicular growth is
duct. Similarly, the width of the various sections of the oviduct varied expected. Fluctuations were however seen in both parameters after
among themselves. In descending order, the infundibular lip was the stablisation, possibly because sexual maturity in those birds coincided
widest, followed by the uterus, and then the magnum and vagina with the minor breeding season.
having approximately the same width, and finally, the isthmus. The Gribbins, Rheuberta, Colliera, Siegelb, and Severc (2008) reported
cloaca was approximately of the same width as the uterus, but wider increasing testicular volume with increasing spermatogenic activity and
than the magnum, vagina and isthmus. noted that this is a very good measure of spermatogenesis in animals.
Correlations among ovarian and oviducal anatomical parameters The increases in testicular volume noted between 8 and 12 WOA in the
were strong (p<0.001) and positive. Similarly, Correlations between present study is attributable to both increased testicular parenchyma
17β-oestradiol concentration and ovarian/oviducal anatomical and commencement of spermatogenic activity since at this age, males
Table 2
Correlations between testicular biometric variables in guinea fowls.
Testicular weight Gonadosomatic index (GSI Testicular length Testicular height Testicular width Testicular Volume Length of vas
deferens
Gonadosomatic index (GSI 0.989***
Testicular length 0.921*** 0.918***
Testicular height 0.888*** 0.882*** 0.927***
Testicular width 0.906*** 0.902*** 0.940*** 0.973***
Testicular Volume 0.988*** 0.978*** 0.922*** 0.882*** 0.923***
Length of vas deferens 0.497*** 0.480*** 0.622*** 0.666*** 0.661*** 0.505***
Testosterone concentration 0.563** 0.571*** 0.524*** 0.406** 0.465*** 0.557*** 0.357**
**Correlation is significant at p<0.01; ***Correlation is significant at p<0.001 level (2-tailed).
45
I.I. Abdul-Rahman et al. Veterinary and Animal Science 6 (2018) 41–49
Fig. 3. Reproductive systems of a 4-week old (A) and sexually mature (B1, B2 and B3) female guinea fowl. In A and B1, note the ovary (OV) and oviduct (Star) in-situ.
In B2 and B3, note the ovary (A), infundibulum (B), magnum (C), isthmus (D), uterus (E), vagina (F) and cloaca (G). Note an egg in the uterus ((arrowhead).
attained puberty and primary and secondary spermatocytes as well as adulthood in male guinea cocks. This is earlier than the 20 weeks re-
round and a few elongated spermatids were visible in their tubules for ported by Awotwi (1975) and Brillard (1986). It has been reported that
the first time (Abdul-Rahman, 2013). The lack of change at 16 weeks cold temperatures can delay reproductive readiness and the onset of
and subsequent marginal and inconsistent increases noticed in testi- photo-refractoriness in male birds (Jones, 1986; Perfito et al., 2004;
cular volume was not surprising, considering the fact that sexual ma- Silverin & Viebke, 1994; Silverin et al., 2008), while warmer tem-
turity in these birds coincided with the minor breeding season and a peratures can advance testicular development (Silverin et al., 2008).
decrease in spermatogenic activity accompanied by decreased testicular Temperatures in southern Ghana are lower than those in Northern
volume could be expected during periods when the testis is quiescent Ghana (Dickson & Benneh, 1988). The study by Awotwi (1975) was
(Gribbins et al., 2008). Except testicular height which showed incon- conducted in southern Ghana while the present study was conducted in
sistent growth pattern from 8 WOA, the other biometric traits showed a northern Ghana, and the variation in onset of sexual activity between
similar pattern of increase as testicular volume. Testicular volume, the two groups of birds is, therefore, not surprising.
length, width and length of vas deferens all tended to stablise from 16 The phase of rising plasma testosterone concentrations in the local
WOA. This age could therefore be considered as the beginning of guinea fowl from 12 WOA coincided with the period of increasing
Table 3
Age-related changes in ovarian/oviducal anatomical paramaters and steroid hormone profiles in female guinea fowls.
Ovarian/oviducal Age (Weeks)
anatomical trait
{Median (Interquartile
range)}
1 4 8 12 16 20 24 28 32
Ovarian weight (g) 0.02 0.05 0.06 0.15 0.22 0.41 0.32 17.2 22.3
(0.01-0.03)f (0.03–0.06)e (0.05–0.08)e (0.08–0.16)d (0.20–0.30)e (0.25–0.66)b (0.29–0.43)b (14.80–21.20)a (13.80–23.90)a
Relative ovarian weight (x10−4) 7.0 5.0 3.0 3.0 4.0 7.0 6.0 1.5× 10−2 1.6× 10−2
(4.0–9.0)b (3.0–7.0)b (2.0–4.0)c (3.0–6.0)bc (4.0–5.0)b (3.0–8.0)b (3.0–6.0)b (1.1–1.8)a (1.3–2.1)a
Oviducal weight (g) – 0.04 0.05 0.07 0.11 0.99 0.64 17.40 23.60
(0.04–0.05)d (0.05–0.05)d (0.05–0.11)cd (0.07–0.20)c (0.23–2.0)b (0.18–0.81)b (14.30–24.20)a (18.40–26.70)a
Oviducal length (cm) – 4.5 7.4 7.3 8.2 9.5 9.6 47.0 45.0
(4.0–5.6)d (6.9–7.6)c (5.9–8.0)c (8.0–9.5)b (9.0–10.0)b (8.2–12.0)b (44.0–49.2)a (40.5–56.0)a
P. oestradiol (pg/ml) – 22.6 15.7 11.9 11.9 13.4 24.7 63.9 57.1
concentration (22.1–23.9)b (9.8–30.5)bc (10.2–15.3)c (10.7–13.6)c (12.1–16.7)c (21.5–28.2)b (46.5–113.2)a (36.6–103.4)a
P. progesterone (ng/ml) – 0.67 0.84 0.89 0.36 0.08 0.38 0.49 0.68
(0.30–1.36)abc (0.76–1.38)a (0.15–0.94)abc (0.30–0.57)c (0.08–0.08)d (0.25–0.61)bc (0.23–0.49)bc (0.56–1.02)ab
Medians (Interquartile range) within a row having no superscript in common are significantly (p<0.05) different. P: Peripheral, –: The oviduct could only be
detached for measurements from 4 weeks of age.
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I.I. Abdul-Rahman et al. Veterinary and Animal Science 6 (2018) 41–49
Table 4 Table 5
Number of visible oocytes in 10 breeding guinea hens. Dimensions of the various sections of the oviduct and cloaca in 20 breeding
local guinea hens.
Hierarchical Large white Medium white Small Total
follicles (>6mm–8mm) (>3mm–6mm) White Section of oviduct Dimension
(>8mm) (3mm
and {Median Length (cm) As Proportion of total Width (cm)
less) (Interquartile oviducal length (%)
range)}
7 5 0 82 94
3 1 13 108 125 Infundibulum 8.1 (5.4–9.0)c 17.2 5.1 (3.6–6.9)a
5 1 10 76 92 Magnum 18.5 39.4 1.7 (1.6–2.5)c
5 1 7 164 177 (16.0–20.0)a
7 1 19 68 95 Isthmus 11.0 23.4 1.2 (1.0–1.5)d
6 1 12 102 121 (9.5–12.0)b
7 2 20 115 144 Uterus 6.3 (6.0–7.5)c 13.4 3.4 (2.9–3.8)b
6 1 19 127 153 Vagina 3.1 (2.5–3.5)d 6.6 1.6 (1.0–2.7)cd
4 1 19 114 138 Total length 47.0 – –
5 0 13 114 132 Cloaca 2.0 (1.9–3.0)e – 3.0 (2.5–3.5)b
Average 5.5 1.4 13.2 107 127.1 Medians (Interquartile range) within a column having no superscript in
common are significantly (p<0.05) different.
testicular anatomical traits, and this might have occurred in response to Table 6
increasing plasma LH concentrations preceding rising testosterone le- Correlations among Ovarian/oviducal anatomical parameters, and peripheral
vels (Wilson, 1979). Chicken LH and FSH are known to promote testi- steroid hormone concentrations.
cular growth and development (Brown, Bayle, Scanes, & Follett, 1975),
Ovarian Relative Oviduct Oviduct P.
while testosterone is implicated in adult testicular function (Brown & weight ovarian length weight Oestradiol
Follett, 1977). The significant positive correlations between all the weight conc
testicular gross anatomical biometric characteristics, length of vas de-
ferens and plasma testosterone concentrations was an indication that Relative ovarian 0.990***
plasma testosterone concentrations in the local guinea fowls could be weightOviduct length 0.996*** 0.965***
highly related to the development of these structures Oviduct weight 0.970*** 0.967*** 0.961***
Testicular anatomical biometric traits stabilised between 16 and 20 P. oestradiol 0.743*** 0.765*** 0.758*** 0.701***
WOA, and this coincided with the period when peripheral testosterone conc
concentrations peaked. Testosterone may, therefore, be implicated in P. progesterone 0.033 0.038 0.022 0.063 0.328**
conc
the development of testicular anatomical structures
**Correlation significant at p<0.01 (2-tailed); ***Correlation significant at
p<0.001 (2-tailed). P: peripheral, Conc: Concentration.
4.2. Gross anatomy of female reproductive tract
in the birds used in the present study may be attributed to differences in
The anatomy of the female guinea fowl observed in the present management between the two flocks of birds. For instance, the birds
study were similar to the earlier reports of Awotwi (1975) in the same used in the present study were fed starter, grower and layer rations with
species. The ovary in the study by Awotwi (1975) assumed the grape crude protein contents of 19%, 15% and 17.5%, respectively, while
cluster appearance between 36 and 40 WOA, contrary to the much those used by Awotwi (1975) were only fed starter (17%) and layer
earlier age of 27 to 28 weeks that was observed in the present study. (15%) rations with lower crude protein contents. Management factors
The birds in the present study laid about 8 weeks earlier than those used including nutrition (Wilson & Harms, 1986; Yu, Marquardt, & Hodgson,
in the study by Awotwi (1975). Two birds even laid as early as 21 WOA, 1972) and photoperiod (Morris, 1967) could influence the onset of
15 weeks earlier than the earliest onset of lay (36 weeks) reported by puberty and sexual maturity in birds.
Awotwi (1975). The earlier onset of lay and therefore sexual maturity
Fig. 4. Variations in the size (rate of yolk deposition) of preovulatory follicles in local guinea hens. Note that difference in size between consecutive follicles
represents the rate (depth) of yolk deposition per day from one position in the hierarchy to the next. Insert: Mature ovary showing the hierarchial structure of
developing follicles from F1 to F5. Note: post-ovulatory follicle (POF), large white follicle (LWF), Small white follicle (arrow head) and stigma (arrowed).
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I.I. Abdul-Rahman et al. Veterinary and Animal Science 6 (2018) 41–49
Ovarian growth during the first 24 weeks of life was slow. Even WOA), and their oviducts may still be going through a process of ma-
though significant increases were noticed at 4, 12, 16 and 24 WOA, turation to attain the full adult size.
these were very minimal. This period coincided with the period of slow The period between 24 and 28 WOA, which saw nearly 3-fold in-
growth of oocytes in guinea fowls. Oocyte diameters not exceeding crease in plasma oestradiol concentrations also saw nearly 54-fold in-
3mm (Romanoff, 1931) were recorded at the end of this phase (20 crease in ovarian weight, and coincided with the phase of rapid yolk
weeks). This explains why very slow inconsistent and minimal increases deposition. These results are not surprising considering the fact that
were noticed in ovarian growth during this period. There were large oestradiol induces the synthesis of Vitellogenin (VTG), a phosphogly-
increases in ovarian weight after 24 WOA. Such rapid increases are colipoprotein, which is a yolk protein (Shen, Steyrer, Retzek, Sanders, &
attributable to the deposition of alternate layers of white and yellow Schneider, 1993). Rapid yolk deposition, could therefore, be the reason
yolk (Bellairs, 1967) in the oocyte between 20 and 26 WOA (inter- for this huge increases in ovarian weight. Oestradiol is also known to
mediate phase of yolk deposition) and yellow yolk (Gilbert, 1971) be- enhance growth of oviduct and promote the formation of tubular se-
tween 26 and 28 WOA (rapid phase of yolk deposition). cretory glands and epithelial differentiation (Johnson, 2000). The 27-
In the birds used in the present study, the rapid yolk deposition and 5-fold increase in oviducal weight and length, respectively, during
culminated in adult ovarian weight of 17.2–22.3 g at 28–32 WOA. This this period was therefore expected. The increased oestardiol secretion
was much lower than the 30.5 to 32.1 g adult ovarian weight reported between 24 and 28 WOA in the guinea hens may be attributed to in-
by Awotwi (1975) in the local guinea fowls. This difference may be due creased secretion in each of the four largest follicles (Johnson, 2000).
to the fact that the birds used by Awotwi (1975) attained sexual ma- The significant negative and positive correlations noticed between
turity at an older age (36 to 40 weeks), and this may be responsible for ovarian/oviducal anatomical parameters and peripheral oestradiol
their higher ovarian weights. It has been reported that early maturity concentrations indicate that the development of these structures could
strains of birds enter lay with lower ovarian weights be predicted based on peripheral oestradiol concentrations in female
(Renema, Robinson, Luzi, & Feddes, 2003). Relative ovarian weight, guinea fowls.
which is an indication of investment made into ovarian growth by the Peripheral progesterone concentrations fluctuated considerably
guinea hen was relatively stable from 4 WOA and only saw huge in- during sexual development. This result is not surprising considering an
creases during the intermediate and rapid yolk deposition stages. This is earlier report that peripheral progesterone concentrations varied with
an indication that the guinea fowl maintains a constant level of in- the physiological state of the animal (Furr, 1969). For instance, while
vestment into stromal tissue from about 4 WOA until puberty. Furr (1969) reported higher values in laying birds about 12–14 h after
The number of visible oocytes noted in the ovaries of guinea fowls ovulation, Etches (1990) noted that the peak occurs 6 to 4 h before
(92–177) in the present study was much lower than the range of 434 to ovulation. Abdul-Rahman et al. (2016a) also reported a concentration
675 reported by Awotwi (1975). The difference in number is attribu- of 5.29 ng/ml about 1–2 h prior to lay and 0.57 ng/ml post-lay in the
table to the fact that the birds used in the present study were much guinea fowl. The authors indicated that this post-lay concentration was
younger (28–32 WOA) than those studied by Awotwi (1975; 36–40 similar to that found in non-breeding birds.
weeks), and since number of visible oocytes increases with age Ovarian and oviducal parameters saw 2 phases of growth, initial
(Romanoff & Romanoff, 1949), these results were not surprising. The phase of slow growth from hatching until 24 WOA, and final phase of
largest number of visible oocytes found in the domestic fowl was 3605, massive increases between 24 and 28 WOA, and this may be under the
while the least was 586 (Romanoff & Romanoff, 1949). In the local influence of oestradiol. Progesterone secretion did not seem to correlate
guinea fowls, Awotwi (1975) recorded the highest of 675 and the with the growth of female reproductive tract, and fluctuated con-
lowest of 434, possibly because these birds were not systematically siderably during sexual development.
selected for intensive egg laying, as with the 1865 study which reported
only 600 visible oocyte in the domestic fowl (cited by Romanoff & Funding
Romanoff, 1949). The huge increases noticed in the number of visible
oocytes in the domestic breeds of chicken not only gives an indication Funding for the project was partly provided by the Commonwealth
of the enormously increased reproductive potentialities of the modern Scholarship Commission in the UK, and Association of Commonwealth
hens, but also shows the effect of selective breeding of the hen, parti- Universities (CSC Ref No: 2009-378).
cularly, White Leghorn for high egg production. Indicating that the
local breeds of guinea fowl could also be intensively selected for im- Disclosure statement
proved reproductive performance.
Increases in oviducal length and weight followed a similar pattern The authors declare that there are no conflicts of interest.
to ovarian weight. The increases, though significant, indicate that in-
creased weight rates were minimal until the period between 24 and 28 Acknowledgements
weeks, corresponding partly and entirely to the periods of intermediate
and rapid yolk depositions, respectively. The oviduct was obviously The authors wish to thank Peter O'Shaughnessy and Neil Evans, all
preparing to secrete the other components of the egg following the first of the Veterinary Biosciences, University of Glasgow, for scrutiny of the
ovulation. Considering the fact that both the ovary and oviduct mature manuscript and help with radioimmunoassay.
and function in a complementary fashion, it is not surprising that the
anatomical parameters of both organs were strongly and positively References
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