Relationship Between Days Dry, Days Open, and Milk Yield in Egyptian Buffaloes

A total of 4,355 records of normal lactations of Egyptian buffaloes kept at Mehalet Mousa Farm, belonging to the Animal Production Research Institute (APRI) (Research Center, Ministry of Agriculture, Cairo, Egypt), during the period from 1993 to 2022 were utilised in this study to estimate the relationships between dry period and days open with milk traits. The following variables were the focus of the study: total milk yield (TMY), lactation period (LP), dry period (DP), and days open (DO). The mean values of TMY, LP, DP, and DO were 1704 kg, 212 days, 221 days, and 117 days, respectively. The least squares analysis of variance demonstrated that both the sires (bulls) and the buffalo nested within sires had a significant effect on TMY, LP, DP, and DO. The year and month of parturition, as well as parity, also had a significant influence on most of the studied variables. Furthermore, the estimates of the partial linear regression coefficients of TMY and LP on DO were statistically significant (P < 0.01). However, the quadratic regression coefficients were not significant, with values of 6.71 ± 0.28 kg/d and -0.0016 ± 0.0008 kg/d2 for TMY and 1.03 d/d and -0.00004 ± 0.00005 d/d2 for LP, respectively. The findings of this study indicate that the estimates of the linear regression coefficients of TMY and LP on DP were significant (P < 0.01). However, the quadratic regression coefficients were not significant, with values of -6.89 ± 0.32 kg/d and 0.0009 ± 0.0006 kg/d² for TMY and -1.02 ± 0.02 d/d and 0.00001 ± 0.0004 d/d² for LP, respectively. The findings of this study indicated that a reduction in the dry period and the number of days open would be a favourable outcome for dairy farmers. This would assist in reducing the financial expenditure associated with the rearing of breeding cows and optimising the number of lactations per cow.