A morphometrical study on the skull of Padovana chicken

Figures & data

Figure 1. Skull of chicken with frontal bony protuberance (on the left, PCxPA) and without frontal bony protuberance (on the right, PCxB).

Figure 2. Skull of Padovana camosciata. Measurements: a = skull total length (skull length, comprehensive of the beck length); b = skull total height; c = frontal protuberance height. On the frontal protuberance little holes are indicated (arrows). The star indicates the point from which skull width was measured, from side to side, at eyes level.

Table 1. Comb, crest and frontal protuberance’s openings classification.

	0	1	2	3	4	5	6
Comb	No comb	Thickening	Just drafted red horns	Very small red horns	Small red horns	Single comb with reduced base of plant	Completely developed single comb
Crest	No crest	Not completely developed crest	Completely developed crest
Frontal protuberance’s opening size	No opening	Small opening	Medium opening	Large opening	Opening large as skull’s top

Table 2. Data on the skull morphometry of the three genetic groups.

	Genotypes^a				Probability
	B	Padovana	PCxB	RSME	B vs Padovana	Padovana vs PCxB	B vs PCxB
Skull weight, g	5.25	4.34	4.93	0.8147	.0007	.028	.308
Skull height, mm	25.00	28.6	25.1	2.1423	<.0001	<.0001	.921
Skull length, mm	77.59	72.1	75.2	3.7179	<.0001	.016	.095
Skull width, mm	28.37	26.3	26.6	1.1270	<.0001	.449	.0001
Frontal bone height, mm	5.05	13.1	5.41	1.3458	<.0001	<.0001	.485
Fbh/sw^b ratio	0.178	0.502	0.201	0.0582	<.0001	<.0001	.251

^a B = Berlanda (14 obs); Padovana = PA-Padovana argentata (14 obs), PC-Padovana camosciata (13 obs), PCxPA = Padovana camosciata x Padovana argentata (12 obs); PCxB = Padovana camosciata x Berlanda (13 obs). RSME: Root Square Mean Error (62 degrees of freedom).

^b Frontal bone height/skull width ratio.

Table 3. Sexual dimorphism (contrast estimates ± standard error) in skull characteristics of five genotypes^a.

	B	PA	PC	PCxPA	PCxB
	M vs F	M vs F	M vs F	M vs F	M vs F
Skullweight, g	1.99 ± 0.297***	1.21 ± 0.198***	1.29 ± 0.454*	0.533 ± 0.453	1.027 ± 0.670
Skullheight, mm	0.434 ± 0.173*	2.73 ± 1.48	3.61 ± 0.634***	0.426 ± 0.622	0.460 ± 0.629
Skull length, mm	6.86 ± 0.358***	8.74 ± 1.41***	5.29 ± 2.20*	2.66 ± 2.48	4.45 ± 2.62
Skull width, mm	2.93 ± 0.313***	2.17 ± 0.654**	1.44 ± 0.638*	0.817 ± 0.813	0.893 ± 0.635
Frontal bone height, mm	0.916 ± 0.134***	−1.82 ± 1.049	−0.486 ± 0.787	0.431 ± 0.570	0.971 ± 0.240**
Fbh/sw^b ratio	0.014 ± 0.004**	−0.116 ± 0.044*	−0.046 ± 0.038	0.001 ± 0.033	0.034 ± 0.012**

^a B = Berlanda (seven males, seven females), PA = Padovana argentata (seven males, seven females), PC = Padovana camosciata (seven males, six females). PCxPA = Padovana camosciata x Padovana argentata (seven males, five females), PCxB = Padovana camosciata x Berlanda (six males, seven females).

^b Frontal bone height/skull width ratio.

* p < .05.

** p < .01.

*** p < .001.

Figure 3. Skull height in PCxB (on the left), PA (in the middle), PC (on the right). Lateral view.

Figure 4. Sexual dimorphism in the Padovana varieties, lateral view. PA (above) and PC (below), male (on the left) and female (on the right).

Figure 5. Frontal bone characteristics. Frontal–dorsal view. On the left skull without bony frontal protuberance (PCxB, female) is represented; in the middle skull with bony frontal protuberance with numerous little holes (PCxPA, male); on the right a skull with numerous holes of variable dimension on frontal bony protuberance (PCxPA, male). Note in PCxB the wide slot between the frontal processes of nasal bone, due to the lack of the nasal process of premaxilla removed together with the premaxilla.

Figure 6. Padovana camosciata skulls (male), view from above. Frontal bone’s holes. In the figure skulls with holes, variables for number and dimensions, are represented. On the right only one big opening is located on the top of the skull.

Figure 7. Padovana camosciata skulls, lateral view. In the skull on the right, characterised by a single big hole on the top of the head, the total skull height appears lower than the height of the skull on the left.

Table 4. Sexual dimorphism in frontal bone openings and comb and crest of the five genotypes^a.

	B			PA			PC			PCxPA			PCxB
	Male	Female	p	Male	Female	p	Male	Female	p	Male	Female	p	Male	Female	p
Opening, n	–	–	–	1.71	2.00	ns	1.57	1.67	ns	3.28	3.80	ns	–	–	–
Openings size	–	–	–	2.00	2.43	ns	3.00	2.83	ns	1.86	2.40	ns	–	–	–
Comb	6.00	6.00	–	1.43	0	*	2.14	0	**	1.67	0	**	5.83	5.00	**
Crest	0	0	–	2.00	2.00	–	2.00	2.00	–	2.00	2.00	–	0.333	1.00	**

^a B = Berlanda (seven males, seven females), PA = Padovana argentata (seven males, seven females), PC = Padovana camosciata (seven males, six females). PCxPA = Padovana camosciata x Padovana argentata (seven males, five females), PCxB = Padovana camosciata x Berlanda (six males, seven females).

* p < .05.

** p < .01.

*** p < .001.

Table 5. Contrast estimates ± standard error for skull and head parameters for PA, PC and PCxPA chickens.

	Male			Female
	Genotype^a			Genotype^a
	PA vs PC	PCxPA vs PC	PCxPA vs PA	PA vs PC	PCxPA vs PC	PCxPA vs PA
Skull weight, g	−0.696 ± 0.493	−0.290 ± 0.493	0.406 ± 0.493	−0.613 ± 0.338	0.465 ± 0.368	1.08 ± 0.356**
Skull height, mm	−4.21 ± 1.01***	−5.17 ± 1.01***	−0.957 ± 1.01	−3.34 ± 0.589***	−1.99 ± 0.641**	1.35 ± 0.620*
Skull length, mm	−2.74 ± 1.88	−4.60 ± 1.88**	−1.86 ± 1.88	−6.19 ± 1.92**	−1.97 ± 2.13	4.22 ± 2.05
Skull width, mm	0.014 ± 0.593	0.086 ± 0.593	0.071 ± 0.593	0.719 ± 0.629	0.707 ± 0.684	1.43 ± 0.662*
Frontal bone height, mm	−1.91 ± 0.657**	1.06 ± 0.657	2.97 ± 0.657***	−0.583 ± 0.617	0.140 ± 0.647	0.723 ± 0.647
Fbh/sw^b ratio	−0.072 ± 0.029*	0.038 ± 0.029	0.110 ± 0.029***	−0.002 ± 0.030	−0.009 ± 0.031	−0.007 ± 0.031
Opening, n	0.143	1.71**	1.57*	0.333	2.13*	1.80
Openings size	−1.00*	−1.14*	−0.143	−0.405	−0.433	−0.029

^a PA = Padovana argentata, PC = Padovana camosciata, PCxPA = Padovana camosciata x Padovana argentata.

^b Frontal bone height/skull width ratio.

* p < .05.

** p < .01.

*** p < .001.

Table 6. Contrast estimates ± standard error for skull and head parameters for B, PC and PCxB chickens.

	Male			Female
	Genotype^a			Genotype^a
	B vs PC	PCxB vs B	PCxB vs PC	B vs PC	PCxB vs B	PCxB vs PC
Skull weight, g	1.04 ± 0.493*	−0.803 ± 0.513	0.241 ± 0.513	0.345 ± 0.338	0.156 ± 0.325	0.502 ± 0.338
Skull height, mm	−7.64 ± 1.01***	0.096 ± 1.05	−7.54 ± 1.05***	−4.46 ± 0.589***	0.070 ± 0.566	−4.39 ± 0.589***
Skull length, mm	3.51 ± 1.88	−3.64 ± 1.96	−0.131 ± 1.96	1.94 ± 1.86	−1.23 ± 1.70	0.709 ± 1.86
Skull width, mm	2.77 ± 0.593***	−2.79 ± 0.617***	−0.021 ± 0.617	1.27 ± 0.629*	−0.746 ± 0.604	0.524 ± 0.629
Frontal bone height, mm	−7.61 ± 0.657***	0.393 ± 0.683	−7.21 ± 0.683***	−9.01 ± 0.594***	0.337 ± 0.571	−8.67 ± 0.594***
Fbh/sw^b ratio	−0.302 ± 0.029***	0.034 ± 0.030	−0.268 ± 0.030***	−0.362 ± 0.029***	0.018 ± 0.027	−0.343 ± 0.029***

^a B = Berlanda, PC = Padovana camosciata, PCxB = Padovana camosciata x Berlanda.

^b Frontal bone height/skull width ratio.

* p < .05.

** p < .01.

*** p < .001.

Table 7. Correlations between skull and head parameters according to the genotypes^a.

	Skull height^b		Frontal bone height^b			Openings number^c		Comb^c
	Skull weight	Skull length	Skull length	Skull width	Skull height	Openings Size		Skull width	Skull height	Frontal boneHeight
B	0.775	0.678	0.938	0.929	0.746	–		–	–	–
	0.001	0.008	<0.0001	<0.0001	0.002
PA	0.519	0.544	−0.274	0.466	0.046	−0.438	PA–PC–PCxPA	0.504	0.559	−0.092
	0.057	0.054	0.365	0.108	0.881	0.118		0.023	0.010	0.700
PC	0.741	0.813	−0.394	−0.493	−0.344	−0.656
	0.004	0.001	0.206	0.087	0.250	0.015
PCxPA	0.072	−0.278	−0.520	−0.409	0.650	−0.689
	0.823	0.409	0.101	0.187	0.022	0.013
PCxB	0.560	0.623	0.594	0.266	0.442	–		–	–	–
	0.047	0.023	0.033	0.380	0.131

^a B = Berlanda, PA = Padovana argentata, PC = Padovana camosciata, PCxPA = Padovana camosciata x Padovana argentata, PCxB = Padovana camosciata.

^b Pearson correlations;.

^c Spearman correlations.

Observations number: B= 14 (males and females); PA= 13–14 (males and females); PC= 13 (males and females); PCxPA= 12 (males and females); PCxB =13 (males and females); for comb =20 (males of PA, PC and PCxPA). Italic: probability.