Aim:The aim of the present study was to assess the influence of temperature and humidity prevalent under subtropical climate on the breeding values for fertility traits viz. service period (SP), pregnancy rate (PR) and conception rate (CR) of Murrah buffaloes in National Dairy Research Institute (NDRI) herd.Materials and Methods:Fertility data on 1379 records of 581 Murrah buffaloes spread over four lactations and climatic parameters viz. dry bulb temperature and relative humidity (RH) spanned over 20 years (1993-2012) were collected from NDRI and Central Soil and Salinity Research Institute, Karnal, India. Monthly average temperature humidity index (THI) values were estimated. Threshold THI value affecting fertility traits was identified by fixed least-squares model analysis. Three zones of non-heat stress, heat stress and critical heat stress zones were developed in a year. The genetic parameters heritability (h2) and repeatability (r) of each fertility trait were estimated. Genetic evaluation of Murrah buffaloes was performed in each zone with respect to their expected breeding values (EBV) for fertility traits.Results:Effect of THI was found significant (p<0.001) on all fertility traits with threshold THI value identified as 75. Based on THI values, a year was classified into three zones: Non heat stress zone(THI 56.71-73.21), HSZ (THI 75.39-81.60) and critical HSZ (THI 80.27-81.60). The EBVfor SP, PR, CR were estimated as 138.57 days, 0.362 and 69.02% in non-HSZ while in HSZ EBV were found as 139.62 days, 0.358 and 68.81%, respectively. EBV for SP was increased to 140.92 days and for PR and CR, it was declined to 0.357 and 68.71% in critical HSZ.Conclusion:The negative effect of THI was observed on EBV of fertility traits under the non-HSZ and critical HSZ Thus, the influence of THI should be adjusted before estimating the breeding values for fertility traits in Murrah buffaloes.

Premature disposal of female calves before reaching milch herd and undesirable disposal of lactating cows are the major constraints in achieving larger herd size. During the early lactations, younger cows are supposed to give higher milk yield and undesirable disposal of early calvers, thereby, greatly hampers profitability of a dairy farm. Knowledge of the incidence of disposal along with reasons in various age groups and at various parities is essential to identify which age group or parity is more vulnerable for disposal. Moreover, knowledge of various genetic and non-genetic factors associated with disposal of animals may also be helpful in developing breeding and management strategies to reduce the incidence of disposal. In most of the studies, it was found that major reasons of disposal of dairy cattle were mortality among female calves and involuntary culling among adult lactating cows. Maximum mortality in female calves was observed during earlier ages and pneumonia, gastro-enteritis and debility were major reasons of female calf mortality. Whereas, most of the adult cows left the herd, due to teat and udder and reproductive problems. Moreover, indigenous breeds were found to be more adapted to Indian tropical climatic conditions in comparison to crossbred and exotic cattle breeds.

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Information on culling pattern of animals helps in developing effective breeding plans for genetic improvement of the herd. Data on 292 reserved KF males out of 1740 male calves born, spread over a period of sixteen years from 1997 to 2012, were collected based on pedigree performance. The data were analysed using descriptive statistics considering the period of birth, season of birth, genetic group and age group. Study revealed increase in culling percentage with advancement in age. Culling in KF males for the different periods (1997-2000, P-1; 2001-2004, P-2; 2005-2008, P-3 and 2009-2012, P-4) were 75.93, 92.16, 64.44 and 28.26 percent, respectively. Maximum culling was observed in males born in summer season (76.12%) which could be due to inclement weather conditions exposure in young age and insufficient quality green leguminous fodder in subsequent months. Generally, upto the age of 3 years, culling in KF males were maximum in interbred and minimum in F1 but with advancing age, culling rate was found higher in F1 genetic group KF males where reproductive problems were the main causes. High culling rate in <1.5 yrs age groups was observed due to poor growth (3.42%) while in adult bulls of above 1.5yrs of age, main reasons of culling was surplus (33.22%) followed by poor semen quality (10.27%), poor libido (7.53%), and poor semen freezability (4.45%). It can be concluded that culling pattern study can help in formulation of better management strategy to reduce the problems associated with culling and better economic return for the farm.