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Subject: Agricultural Statistics and Informatics × Author: Anita, S × End date: 1999 × Type: Thesis ×
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    ThesisItemOpen Access
    Comparative study of lactation curves in goats
    (Department of Agricultural Statistics, College of Horticulture, Vellanikkara, 1991) Anita, S; KAU; George, K C
    Based on the weekly milk yield data of 20 weeks duration over different parities of the seven yenetic groups viz. Alpine Malabari, Malabari, Saanen Malabari, F2A , F2S, F3A and F3S maintained at the KAU, Goat Farm during the period 1976-'87, the following objectives were investigated. 1. To fit various lactation curve models in different breeds of goats and to select the most suitable one 2. To suggest a procedure for predicting complete lactation yield using various part lactation yields, 3. To study the effect of genetic and non-genetic factors on milk production traits. 4. To compare the persistency of milk yield among the selected breeds. On the basis of the criterions I, r and s eleven types of fitted lactation curves were compared. Among the curves compared the quadratic-cum-log and linear hyperbolic functions were selected as the best two curves for the genetic groups,Alpine Malabari, Malabari, F2A, F2S, F^A while for genetic groups Saanen Malabari and F^S the linear hyperbolic and quadratic log scale functions were the best two selected curves. As the linear hyperbolic function was found to be suited for all breeds under study it was selected as the best fitted curve for goats. Taking various cumulative part records of 4, 8 and12 weeks the linear hyperbolic function was then fitted to the parity-wise and pooled data of the seven genetic groups. It revealed that efficiency of over 98 per cent was achieved for all the part records though the efficiency increases with each added part record and hence this function could be selected as a prediction equation for the prediction of total yield from part record. Based on the ANOVA obtained by a two way classified non orthogonal data analysis the breed, order of lactation and their interaction were found to have significant influence on average yield. Among the breeds Saanen Malabari and among the parities fourth parity were found to be significantly different from the others and have the highest average weekly yield. Among the four methods used for comparing the seven genetic groups by calculating the persistency index, three methods (except method II) gave Saanen Malabari as the highest persistent one. By method II the highest index was attained by F^S followed by Saanen Malabari. Since Saanen Malabari gave the highest yield for pooled and individual parity data it was selected as the most persistent and high yielding breed.