Genetic and phenotypic parameters of milk composition traits in Jamunapari goats

The fresh milk samples were collected at 15 days intervals from kidding to 90 days of lactation from 100 selected animals during the year 2009-2011 (3 years) and analyzed  fat, SNF, casein, total protein, lactose and ash content in milk of Jamunapari goats were 3.00±0.04, 9.21±0.02, 2.86±0.02, 3.22±0.02, 4.69±0.04 and 0.77±0.003 percent, respectively. There were significant effect of sire on all milk composition traits. Year of kidding significantly (P<0.01) influenced all the milk composition traits. The season of kidding had significant (P<0.01) effect on all milk composition traits. Significant (P<0.01) differences in the milk constituents viz., fat, protein, lactose and ash % except SNF and casein percentage were observed among does of different parities (ages). Sampling interval had significant (P<0.01) effect on the different milk composition traits and heritability estimates of different milk compositional traits were moderate to high and varied from 0.18 - 0.41. The phenotypic and genetic correlations of fat content with all milk constituents were low to moderate and positive except SNF and lactose, where the magnitude of estimates were negative. Similarly, the genetic and phenotypic correlations of SNF with other milk constituents showed the similar trend. The estimates of phenotypic and genetic correlations of casein with other milk constituents were positive except SNF and ranged from low to moderate and the estimates ranged from medium to moderately high (0.22 to 0.55). Positive and moderate phenotypic and genetic correlations exist between protein content and other milk constituents of Jamunapari goats. The lactose content of milk had positive genetic and phenotypic correlations with other milk constituents except fat content of milk. Similarly, the ash content of milk was positively and moderate to highly correlated with other milk constituents at genetic and phenotypic level in this study.