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Background: 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 x THI in crossbred dairy cows reared at institute herd of ICAR-National Dairy Research Institute, Eastern Regional Station, Kalyani, West Bengal. Methods: 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. Result: 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 x 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. [ABSTRACT FROM AUTHOR]

Present study was envisaged to examine existence of genetic group x THI in crossbred cows at institute herd of ERS, ICAR-NDRI, Kalyani, West Bengal. 1041 fertility records each on service period (SP) and conception rate (CR) and weather parameters spanned over 22 years (1994-2015) were collected; arranged under three THI groups; thermal comfort (THI<72), two heat stress zones (THI 72-78) and THI>78 and six genetic groups.SP was longest (163.61 ± 6.83 days) when THI>78and lowest (149.27±6.69 days) during THI<72. CR was lowest (65.66±2.73 %) when THI>78 and highest (70.54±2.8 %) at THI<72. Genetic group x THI was non-significant on SP and CR. However, there was re-ranking of genetic groups across three THI zones. Genetic group bearing 50% Jersey + 50% Tharparkar followed by 50% Jersey + 50% Red Sindhi exhibited least increase in SP (5.09 and 6.37 days) when THI>78.Cows bearing 50% Jersey and 50% indigenous cattle inheritance followed by 50% Jersey + 50% Red Sindhi and 50% Jersey + 50% Tharparkar depicted least drop in CR at THI>78 (-2.38, -2.40 and -3.6%) in comparison to THI<72. The genetic group with>75% Jersey depicted maximum increase in SP (15.33 days) and drop in CR (-7.43%) at THI>78. [ABSTRACT FROM AUTHOR]

Optimum nutritional condition of dairy cows during the different stages of production is highly recommended. Production of high quality milk is the primary goal of every herdsman. However, improper nutrition of dairy cows leads to different unwanted ailments and disease losses. This becomes a burden for dairy owners. Most commonly, dairy cow undergoes negative energy balance (NEBL) condition due to improper dry matter intake (DMI). DMI in proper amount provides good nutrition for the dairy animals. There is a common trend of depressed DMI during the transition and the initial lactation period of high-producing animals. Following which elevated levels of non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHBA), blood urea nitrogen (BUN), undesired body condition stages, lowered production performances, poor milk quality, and inferior udder health status of dairy cows are observed. Both over-conditioned and under-conditioned bodies of the dairy animal are more at risk of NEBL thereby posing a negative impact on behavioral and production performance. This review is framed to discuss the effect of negative energy balance on the behavior and production performance of dairy cows. [ABSTRACT FROM AUTHOR]