Abstract   

    Behaviour of lactation length in Nili-Ravi buffaloes and its relationship with other economic traits was studied using 2704 lactations of 993 buffaloes. Lactations shorter than eight weeks were not included in the data set. About 59% of the lactations had length shorter than the standard lactation of 10 months. Lactation length averaged 289.5 days for an average milk yield of 1984 kg. Lactation curves were different for first and later parities with different days in milk. Year effeced (P<0.01) lactation length while season did not. Yet, interaction of year and season was significant (P<0.01). Age at calving within parity also had an effect (P<0.01) with first parity buffaloes having the highest average (280.4+6.25 days). The trait was 25% repeatable. Phenotypic trend in the trait was positive, with least squares means for 1970-71 (227.4+14.03 days) and 1996-97 (300.9+13.86 days) being different by about 10 weeks. Further studies should be carried out to find out causes for this positive trend.

Key words: Lactation length, Nili-Ravi buffalo.