An image analysis of the horn structures was performed using Sedecal radiology equipment, collecting the images in a Fujifilm digital chassis (CR). X-rays were initially taken in 12 animals in both horns, observing a manifest symmetry between the two horns in the bony part, for which it was decided to perform the following determinations, only in the right horns.

Since one of the determining aspects of the mechanical resistance of the horn is the degree of calcification of the bony structures that support it, it is considered necessary to evaluate the bone density of the cornual processes of the frontal bone, in order to verify the existence or not of influence of the sheathing at this level. A Hologic QDR- 1000/W densitometry equipment was used; measurements were taken of both the proximal half of the horn (base) and the distal half (tip). To determine the two study regions, the midpoint of the horn located by laser was used as a reference (Figure 3).

Figure 3

From that moment on, a series of radiological beams are performed to obtain values of Bone Mineral Content (BMC gr), and bone area studied (cm2), from which the densitometer software calculates the Bone Mineral Density (BMD gr/cm2).

For this study a 3 Tesla closed magnetic resonance equipment was used, with superconductive magnet, General Electric Medical System brand; after two preliminary tests with a wrist antenna and a head antenna, it was decided to carry out the studies with a Cardio-array antenna (Figure 4), of the same brand. The images were processed using the OsiriX program, which allows precise measurements to be made on the images.

Figure 4

The horns were placed on two pads to center them in the magnet, in a position that would correspond to the supine decubitus position of the animal; but slightly more rotated to take advantage of the area of greater magnetic intensity.

The study technique consisted of a locator in 3 planes, with a second locator also in three complementary planes; oblique coronal slices were made on these, looking for the plane that covered the greatest length of the horn and covering the rest of the anatomy with the rest of the slices (Figure 5). These slices were 5 mm thick and 0.5 mm apart, which translates into a distance of 5.5 mm between slices. These images were acquired in T2 FRFSE and in T1SE.

Figure 5

Axial slices were programmed on the previous images, perpendicular to the previous ones with 6 mm of thickness and 14 mm between slices (Figure 6); which gives us a distance between slices of 20 mm, which will facilitate the comparison of results with the rest of the techniques. These images were also obtained in T2FRFSE and T1SE.

Figure 6

The orientation of these axial series means that, as the slices are parallel to each other, the first two and the last two are very oblique, giving us an elliptical image of the bone section, the rest of the slices being reasonably perpendicular to the horn axis.

All the data were processed using the SPSS program, performing a one-way analysis of variance (ANOVA), considering group 0 as the unsheathed animals and group 1 as the sheathed ones.

By means of radiography it is possible to distinguish perfectly different parts of the horn and therefore its internal structure. No serious alterations of the internal structure of the horns were found, nor were they compatible with chronic pathological processes in the bony area of any of the horns studied. However, some alterations were observed in the area of the horn massif, such as breaks or splinters, as can be seen in the upper left part of Figure 7, but in both animals of the sheathed and un- sheathed group.

Figure 7

The one-way ANOVA performed between groups according to this variable, gave significant differences between groups in the values referred to the distal half of the horn called tip, as can be seen in Table 1.

Table 1

	Mean Gr 0	Mean Gr 1	St Dev.. 0	St Dev. 1	df	df	DM	F	p
Tip Area	67.677	56.964	11.648	11.613	1	47	135.311	10.282	0.002
Tip BMC	120.931	97.057	26.256	24.867	1	47	657.656	10.507	0.002
Tip BMD	1.777	1.687	0.170	0.121	1	47	0.023	4.358	0.042
Base area	129.756	123.395	18.680	20.360	1	47	378.255	1.297	0.261
Base BMC	300.275	293.270	54.570	51.385	1	47	2827.126	0.210	0.649
Base BMD	2.309	2.378	0.193	0.162	1	47	0.032	1.777	0.189
Total BMC	421.207	390.326	70.647	70.330	1	47	4971.029	2.325	0.134
Total Area	197.433	180.359	25.750	29.710	1	47	761.176	4.643	0.036

The proximal area of the horn showed no differences between the two study groups, and a correlation matrix was then performed between the values obtained by densitometry and the external biometric variables, the results of which are shown in Table 2.

Table 2

	External length	Internal length	Vert D Strain	Hor D Strain	Ver D Shovel	Hor D Shovel	Vert D Tip	Hor D Tip
Tip Area	0.155	-0.007	0.350	0.482	0.301	0.581	-0.464	-0.176
Tip BMC	0.098	-0.072	0.382	0.546	0.312	0.596	-0.482	-0.142
Tip BMD	0.047	-0.112	0.368	0.465	0.259	0.466	-0.428	-0.006
Base area	0.695	0.546	0.719	0.431	0.635	0.569	-0.582	-0.326
Base BMC	0.711	0.546	0.581	0.328	0.555	0.445	-0.513	-0.192
Base BMD	0.226	0.131	-0.124	-0.106	-0.020	-0.124	-0.030	0.233
Total BMC	0.587	0.399	0.586	0.448	0.541	0.556	-0.568	-0.199
Total Area	0.596	0.422	0.685	0.508	0.603	0.651	-0.620	-0.317

The correlations marked are significant at p <0.05

It should be noted that there is no correlation of the area, mineral content or mineral density of the tip with the total length of the horn, either external or internal, but there is a correlation with the horizontal diameters of the stock and blade, being the inverse with the piton. In a first approximation we can interpret them as that the unsheathed horns have a higher density, due to a certain extent to their greater thickness. However, there is another possible explanation, which would be that the absence of protection of the sheath causes the bone to respond with greater calcification to trauma, produced continuously in fights, blows and other continuous mechanical effects; this last aspect has been proven in humans.

Finally, through magnetic resonance imaging we have clearly observed the patterns of the vascular channels and the dermis that appear as radiolucent areas; as well as the extension of the different cavities and trabecular area of the horn (Figure 9).

Figure 9

In the magnetic resonance images we have found very evident differences in structure between individuals, both in the extension of the cavity or trabecular zone, as well as in the patterns of the channels; but no evidence of pathological alterations has been discovered.

Once the images were processed, the biometric data obtained were subjected to a one-way ANOVA, considering the two groups mentioned above (Table 3).

Table 3

	Mean 0	Mean 1	St Dev. 0	St Dev.1	df		df	F	p
Total External Length	43.462	43.923	3.020	3.343		1	27	0.149	0.703
Solid Length	23.878	28.712	4.353	7.923		1	27	3.872	0.059
Trabecular Length	19.584	15.211	4.401	8.090		1	27	3.050	0.092
Total Internal Length	33.564	34.673	2.720	3.151		1	27	1.000	0.326
Total Surface Area	23.364	27.030	3.933	11.924		1	27	1.122	0.299
Solid Area	21.488	25.304	3.738	10.448		1	27	1.562	0.222
Trabecular Area	1.304	1.555	0.649	1.827		1	27	0.223	0.641
Trabecular Perimeter	4.804	4.515	1.193	2.216		1	27	0.179	0.676
Total Perimeter	17.317	18.507	1.525	3.767		1	27	1.139	0.295

I was able to verify that there were no significant differences in any of the variables considered, although the length of the solid zone without trabecular structure was close to the level of significance; being superior the part without trabecular zone in the sheathed horns.

A linear correlation matrix was performed between the biometric parameters obtained by magnetic resonance imaging and the age of the animals, without showing any significant correlation, finding within the same herd animals with very variable lengths of the trabecular zone; which has not allowed us to develop an explanation for these variations (Table 4).

Table 4

Age
Total External Length	-0.07
Solid Length	0.22
Trabecular Length	-0.24
Total Internal Length	0.18
Total Surface Area	0.82
Solid Area	0.47
Trabecular Area	0.80
Trabecular Perimeter	0.85
Total Perimeter	0.83