Die verwantskap tussen ooglidpigment, haarkleur en kleurpatroon asook die oorerflikheid van ooglidpigment by Simmentalerbeeste
Potgieter, Cornelius Johannes
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The Relationships investigated with eyelid pigmentation were, the characteristics of coat colour and colour pattern. These two were the only significant characteristics which had a significant correlation with eyelid pigmentaiton. The correlation was found to be statistically highly significant because of the huge random test. (P<0.01). Eyelid pigmentation was strongly emphasised because there is a strong correlation between the occurance of eye diseases and eye cancer in animals with no pigment in their eyelids. Although pervious researchers claimed that pigment did not play the leading role in combatting eye cancer, there was however sufficient proof in later studies to confirm the correlation between the lack of eyelid pigmentation and the occurence of eye diseases (opthalmia) and eye cancer. Simmentaler breeders are all committed to select against cattle which do not have adequate pigment in their eyelids. Although farmers have selected cattle according to these preferences for many years there are still too few cattle with pigment round their eyes. The possibility could well be a personal preference to certain characteristics in breeding programmes which act negatively to the selection progress for the character eyelid pigmentation. In this study enough evidence was found to point out the negative correlation between dark hair colour and eye pigment. By this it was found that cream to light brown coloured animals had more pigment in the eyelids. Breeders on the other hand had a preference for dark coloured coat types. The ratio in the data clearly proved this preference: 93.2% darkbrown as to 6.8% light coloured. Selection response could therefore be negatively influenced in the selection for eyelid pigmentation. Colour pattern was positively related to the presence of pigment in the eyelid. Animals totally covered with the dark colour, with few white areas, proved to have mor pigmented eyelids. Animals having single spots of dark colour on a big white background had far less eye pigmentation than the above mentioned. Breeders also preferred animals which were covered with a dark colour pattern. Only 1.8% of the animals selected, fell into this class. The heredity of the characteristic eyelid pigment was calcluated to be h2-0,3088. Selection on own phenotype could thus be practiced as the easiest method to improve pigment in the eyelid. Observational differences would therefore maily be responsible for differences in breeding value. Therefore it could be concluded to recommend that the best selection gain for eyelid pigmentation could be found to be in animals of the lighter coat colour (cream) and a total coloured coat would give the best response according to the results of this study.