Repeatability of growth in Retinto beef cattle

The repeatability depends on genotype and the environmental circumstances t o which the animals are subjected. Bearing in mind the special characterist ic of the husbandry of Retinto beef cattle it is desirable to obtain the es timates of 't' (repeatability) in this breed and under the adverse conditio ns in which the animals are selected. To obtain the repeatability values of the birth weight, weight at 90, 120 and 180 days, and at weaning time we h ave used three methods: intraclass correlation, regression of the second re cord on the first and correlation of the adjacent. The regression estimates are higher than those obtained through the other procedures. The differenc e between the results obtained by the method of intraclass correlation and that of regression could be reflect permanent environmental effects. We have estimated the influence on repeatability ef degree of adjacency. Th e correlation declines with increase of separation. Temporary correlated en vironmental effects may be responsible. We have calculated the correlation between the different growth variables w ithin cow' and 'between cows. Our results show that in the 'between cow' co rrelations, generally of similar magnitude to the 'within' correlations, ar e always superior, which mould indicate a greater influence of the whole ge notype plus the permanent environment, than the temporary effects. In the s ame way there is an appreciable decrease in the correlations when weight an d age are separated in time, both in 'between cow' and in 'within cows'.