Genotype environment interaction on milk production traits of crossbred dairy cows under tropical climatic condition of India

Genotype environment interaction plays vital role in animal productivity. Heat stress is one of the major environmental stressor affecting milk production and measured in terms of temperature humidity index (THI). Indian milk industry largely depends on crossbred cows bearing different degree of exotic inheritance. Thus, the role of genotype (genetic group) of the crossbred cows and environment (THI) interaction plays vital role in Indian climate which is mostly tropical in nature. Therefore, study was undertaken to examine the existence of genetic group × THI in crossbred dairy cows reared at institute herd of ICAR-National Dairy Research Institute, Eastern Regional Station, Kalyani, West Bengal.

A total of 12364 records each of monthly milk yield (MMY) and average daily milk yield in a month (AMY) of crossbred cows spanned over twenty two years (1994–2015) and weather parameters(temperature and relative humidity) for the corresponding years were collected from institute records. The data were classified into 8 genetic groups according to the genetic composition and 3 THI groups (THI <72, THI 72–78 and THI above 78). The interaction model was used to study the GxE interaction study using least squares analysis.

Effect of non-genetic factors (parity, period of calving and stage of lactation) was found to be highly significant (P<0.01) and genetic group × THI was significant (P<0.05) of on both MMY and AMY Genetic group bearing 50% Jersey and 50% Red Sindhi or Tharparkar were the most heat tolerant breeds. Jersey crossbred cows were more heat tolerant than Holstein crossbred cows. Crossbred cows with 50% Jersey inheritance performed better than higher Jersey inheritance during periods of THI above 72.