Abstract
The effect of certain factors such as sex of calf, status of buffalo, season of calving, parity and sire on lactation length and total lactation yield was studied in 391 Nili-Ravi buffaloes. The average lactation length was $301.73{\pm}1.87$ (mean $\pm$ SE) days with a range of 181 to 505 days whereas the average lactation yield was $2031.08{\pm}19.16kg$ and ranged from 1023 to 6535 kg for 984 lactations. The differences in the means of lactation length and lactation yield due to the sex of calf were significant (p<0.05). The status of buffaloes had a significant (p<0.05) effect on lactation length but its effect on lactation yield was non-significant. The season of calving had no effect on lactation length but it influenced the lactation yield significantly. The milk yield was highest ($2150.81{\pm}43.52kg$) in buffaloes which calved in spring and lowest ($1959.92{\pm}30.83kg$) in autumn. The effect of parity on both traits under study was significant (p<0.01). The maximum and minimum lactation lengths of $309.82{\pm}3.96$ and $284.16{\pm}7.17$ days were observed in the first and sixth lactations, respectively. The milk yield was maximum ($2150.38{\pm}58.79kg$) in the seventh lactation and minimum (1818.31 60.04 kg) in the sixth lactation. The influence of sire was significant on lactation length (p<0.05) and milk yield (p<0.01).