title: Assessment of expected breeding values for fertility traits of Murrah buffaloes under subtropical climate.
abstract: OBJECTIVE
  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.
  
  
  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 (h(2)) 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Dairy Cattle Breeding Division, National Dairy Research Institute, Karnal, Haryana, India.
authors.forename: Soumya
authors.initials: S
authors.lastname: Dash
authors.affiliation: Dairy Cattle Breeding Division, National Dairy Research Institute, Karnal, Haryana, India.
authors.forename: A K
authors.initials: AK
authors.lastname: Chakravarty
authors.affiliation: Dairy Cattle Breeding Division, National Dairy Research Institute, Karnal, Haryana, India.
authors.forename: Avtar
authors.initials: A
authors.lastname: Singh
authors.affiliation: Dairy Cattle Breeding Division, National Dairy Research Institute, Karnal, Haryana, India.
authors.forename: Pushp Raj
authors.initials: PR
authors.lastname: Shivahre
authors.affiliation: Dairy Cattle Breeding Division, National Dairy Research Institute, Karnal, Haryana, India.
authors.forename: Arpan
authors.initials: A
authors.lastname: Upadhyay
authors.affiliation: Division of Animal Genetics, Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India.
authors.forename: Vaishali
authors.initials: V
authors.lastname: Sah
authors.affiliation: Dairy Cattle Breeding Division, National Dairy Research Institute, Karnal, Haryana, India.
authors.forename: K Mahesh
authors.initials: KM
authors.lastname: Singh
keywords: critical heat stress zone; expected breeding value; murrah buffaloes; temperature humidity index