Search

The relative efficiency of selection based on part lactation compared to that of total first lactation was high. When the earlier parts of the lactation were considered, single third or fifth monthly milk yield gave a selection efficiency 1 to 6% higher than that obtained from total first lactation yield. The milk yield of the first 120 days and subsequent cumulative part lactation yields up to 270 days were observed to be more efficient for indirect selection for the first lactation than direct selection on the basis of total first lactation yield. For effecting early selection the first 120 days milk production could be used to advantage. Similarly, where there are difficulties in recording the yield daily throughout the lactation, the third or fifth monthly yield recording could be resorted to for selecting efficiently and to formulate culling plans for the herd.

Information is given on crossbred calves between birth and 6 months of age belonging to 6 genetic groups--3 with 50% inheritance from Holstein, Jersey and Brown Swiss and the other 3 with 75% inheritance from 1 or 2 temperature dairy breeds. The mortality rate in 1,059 calves born was 3.87, 2.84 and 1.22% respectively under 1 month, from 1 to 3 and from 3 to 6 months of age. The mortality rate was lower in halfbreds than in crosses with 75% inheritance from temperature breeds. Season of birth, sex of the calf and birth weight did not show any significant association with mortality rate but the latter showed a definite decline with advancing age. No significant association of cause of mortality with age, genetic group and season of birth of the calves was observed. Percentage mortality was largely due to respiratory diseases in the birth to 1 minth age group while diseases affecting the digestive system resulted in more deaths in the 3 to 6 months age group.