Abstract
ABSTRACT Novel study on identification of critical heat stress zone (CHSZ) taking 20 years data was carried out in Indian buffaloes considering the effect of temperature humidity index-THI on milk production and composition traits. More than 3 lakh daily milk yield records (DMY); 9864 records each of monthly test day fat% (MTDF%) and SNF% (MTDSNF%) and meteorological data were collected from ICAR-NDRI and ICAR-CSSRI, Karnal, respectively. THI model [THI = (0.55× Tdb + 0.2× Tdp) × 1.8 + 32 + 17.5] by National Research Council in 1971 was used for computing THI. The year was classified into: Heat Stress Zone (HSZ) and Non-Heat Stress Zone (NHSZ) based on the trends of rising THI and declining milk production and composition traits. For DMY, NHSZ was 1st October to 9th April and HSZ was 10th April-30th September. For composition traits, October-March was NHSZ and April-September the HSZ. Within the HSZ regression analysis was conducted to find the zone where maximum drop in traits occur per unit rise in THI. A maximum decline in DMY 92.20 gram was observed during 15th August-14th September; identified as CHSZ for DMY. Similarly, maximum drop in MTDF% (b = −0.052) and MTDSNF% (b = −0.0114) observed during July-August, considered as CHSZ.
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