Section 14 — Animal Genetics and Breeding 



sented about one-fifth of the observed change. 

 Other less critical results also lead to the same 

 general conclusion. 



14.53. Longevity in Sardinian Sheep. Pietro Dassat 

 and Domenico Bernoco (Turin, Italy). 



The objective of this research was to study 

 the longevity of Sardinian sheep and to in- 

 vestigate the relationship between longevity and 

 age at first lambing. The analyses were made 

 using milk records collected in the Sardinian 

 flock at Barumini (Cagliari) during the period 

 of 15 years beginning in 1943. 



The data comprised 2670 lactations of 678 

 ewes disposed of; their average age was 4.8 

 years. This represents an average productive 

 life of 3.3 years and a replacement rate of about 

 30 per cent. 



Of the 678 ewes of the sample 505 (74 per cent) 

 first lambed at one year and the rest not until 

 two years of age. The age at disposal of the 

 former group was 4.7 years and for the rest 

 5.1 years, with a average productive life of 3.4 

 and 3 years respectively. 



In estimating the average productive life in 

 terms of times lambed, results showed 2.48 lac- 

 tations for the whole sample: 2.55 lactations 

 for the ewes first lambed at one year compared to 

 2.27 lactations for the animals first lambed at 

 two years. The difference is statistically sig- 

 nificant (P <0.01) indicating that early lambing 

 increases the length of the productive life even if 

 it reduces longevity. 



The present note describes the histologic 

 changes of the thyroid gland in five ophthalmic 

 lambs as compared to one normal lamb. 



The current methods of fixing, of inclusion and 

 of staining of the samples were used in this 

 experiment: 



The prepared samples were examined at the 

 following magnification. 



The form of the follicles in the ophthalmic 

 lambs was between oval and round, with an 

 irregular cornered outline. 



The mean height of the follicular epithelial 

 cells was 8.84 u. 



The mean frequency of the various epithelial 

 cells was of 52.08 per cent cylindrical cells, 

 46.42 per cent cubic cells, 1.25 per cent flat cells. 

 Resorption vacuols existed in almost all the 

 follicles of the thyroid gland. In many follicles 

 the resorption of the acidophil colloid was 

 almost total. 



In the normal lamb the proportion of the 

 epithelial cells was different: 42.00 per cent 

 cylindrical cells, 54.00 per cent cubic cells and 

 4.00 per cent flat cells. The mean height of the 

 epithelial cells was 8.07 u. 



In the ophthalmic lamb, the thyroid gland was 

 in a state of hyperfunction. The weight of the 

 lambs decreased with the increase in intensity 

 of the disorders (symptoms). 



14.55. (F). Science and Sheep-breeding. H. N. Tur- 

 ner (Glebe, Australia). 



The data will be pusblished in full on the 

 Italian magazine La Nuova Veterinaria. 



14.54. Contributions to the Histologic Study of the 

 Thyroid Gland in Tzigaia Lambs with Here- 

 ditary Ophthalmy. N. Teodoreanu and Lucia 

 Gurau (Bucarest, Rumania). 



Previous studies (Gh. Radu et «/., 1947; 

 N. Teodoreanu et ai, 1952; and N. Teodoreanu, 

 1958) have stated the occurrence of hereditary 

 semilethal ophthalmy for the first time in 

 lambs of the black-headed Tzigaia breed, at the 

 Slobozia experimental research station. The 

 disease appears between the 2nd and the 60th 

 day of life, ending with the death of the lambs 

 at the age of 2-3 months. 



The film deals briefly with current methods of 

 sheep selection, wool classing and wool buying 

 for Merinos in Australia, all of which rely 

 heavily on hand-and-eye methods of appraisal. 

 The theory behind the use of measurement, the 

 estimation of repeatability and heritability and 

 their application are then demonstrated, and 

 current C.S.I.R.O. selection experiments are 

 described and filmed, including methods of 

 wool-sampling and detailed measurement. In 

 these experiments, wool weight has been raised 

 by 1 lb per head; the absence of any important 

 correlated change is discussed. 



The film then moves to a commercial shed and 

 shows how simply fleece-weighing can be 

 introduced in practice. 



The film was made for general use to demon- 

 strate the experimental work which lies behind 

 a widespread extension campaign in Australia 

 for the introduction of objective methods in sheep 

 selection. 



269 



