Genetic Parameters and Animal Model Evaluation of First Lactation 305-d Milk Yield and Energy Traits in Karan Fries Cattle

Milk as a wholesome food is a source of income for most of the farmers and useful in mitigating the nutritional insecurity of our country. The energy value of milk depends on milk constituents like fat, protein, lactose etc. Milk provides only 3 percent of dietary energy supply; 6-7 percent of dietary protein supply and 6-8 percent of dietary fat supply in Asia and Africa, compared with 11-14 percent in Europe, Ocenia and America (FAOSTAT, 2012).  All India Livestock Census (2012), exotic/crossbred milch cattle increased from 14.4 million to 19.42 million, giving rise to an increase of 34.78% (Anonymous, 2012). The present level of Holstein inheritance in ‘Karan Fries’ is 62.5%-75% (Gurnani et al., 1986). The estimates of genetic parameters are helpful in determining the method of selection, to predict direct and correlated response to selection, choosing a breeding system to be adopted for future improvement as well as in the estimation of genetic gains. The genetic correlations give the information how genes affecting one trait also affect the other traits. The effectiveness of sire evaluation is the backbone of any breed improvement programme as the contribution of sire path is higher than the dam path for the overall genetic improvement for a trait. In case of males, very intense selection can be practised, as few males are required for breeding purpose. So, one of the main criteria of enhancing the genetic potential of animals in a herd is to use proven sires to transmit superior genetic potential for higher milk production. Milk production per cow has considerably improved in the last decades, but the increase in milk yield has been associated with a higher incidence of health and fertility problems worldwide (Pryce et al., 1997).  There is a general compliance that energy balance should be incorporated into future breeding programs, but direct measurements are expensive and complex to be implemented in practice (Hüttmann et al., 2009).The estimation of genetic parameters of energy corrected milk (ECM) has rarely been investigated until now. Therefore, the prime objective was to study the genetic parameters of ECM and comparison of ranks of sires. It is envisaged that this information will be useful for the genetic evaluation of Karan Fries bulls in India.

Description of the study area
 
Karnal is situated at an altitude of 235 to 252 meters (748 feet) above the mean sea level at 29.68°N latitude and 76.98°E longitude in eastern zone of Haryana which comes under the Trans-Gangetic plain agro climatic zone of India. The climate that prevails is subtropical in nature. The temperature in summer months (April to June) ranges between 24°C-44°C. Karnal experiences moderate rainfall in the months of July and lasts till September. Winters are extremely cold. The temperature ranges from 4°C to 32°C in winter months (October, November, December and January).
 
Standardization and normalisation of data
 
The records of Karan-Fries cows of known pedigree and with normal lactation were included in the present study. The normal lactation was considered as a period of milk production by a cow for at least 100 days, the milk production in lactation was recorded a minimum of 500 kg and the cows calved and dried under normal physiological conditions. Out of 402 Karan-Fries cows, information of 51 cows were not considered for this study due to various reasons like abortion, still birth and other reproductive problems.
 
Data source
 
Data on records of 351 Karan-Fries cows, spread over a period of 12 years maintained at ICAR-National Dairy Research Institute, Karnal were analyzed for first lactation milk yield and energy traits viz; First lactation 305-day milk yield (305MY- kg), Fat based energy corrected milk yield (FBECMY-kcal), Fat, protein based energy corrected milk yield (FPECMY-kcal) and Fat, protein and lactose based energy corrected milk yield (FPLECMY-kcal). The study was classified into three periods viz; 1(2007-2010), 2(2011-2014) and 3(2015-2018). Each year was sub-classified into four seasons, depending on prevalent meteorological factors, feed and fodder availability as recorded in CSSRI, Karnal (Singh, 1983). Age at first calving of Karan-Fries cows was classified into three age groups using mean and one standard deviation after normalizing the distribution of AFC in the population as 1{≤ 877 (65)}; 2{878-1200 (237)} and 3{≥ 1201 (49)}. 
 
Statistical models of analysis
 
The univariate animal model was fitted to estimate variance components and heritabilities independently for the four traits. Bivariate or pairwise animal models were used to estimate genetic and phenotypic correlations between the traits. Animal model by WOMBAT software (Meyer, 2007) was used for sire evaluation. The season and period of calving, age group were used as fixed effects, and sires were considered as random effect.
       
First lactation energy corrected milk of Karan-Fries cows was estimated by using standard practices as suggested by Overmann and Sanmann (1926) as follows:
 
Fat based energy per kg (cal) (FBE/kg) = Average Test Day fat Percentage (ATDFP) × 9.23) × 1000/103
 
Fat, Protein based energy per kg (cal) (FPBE/kg) = Average Test Day fat Percentage (ATDFP) × 9.23) + Average Test Day Protein Percentage(ATDPP) × 5.71) ×1000/103
 
Fat, Protein, Lactose based energy per kg (cal) (FPLBE/kg) = Average Test Day fat Percentage (ATDFP) × 9.23) + Average Test Day Protein Percentage (ATDPP) × 5.71) + Average Test Day Lactose Percentage (ATDLP) × 3.95) ×1000/103
 
Fat Based Energy corrected milk yield (kcal) (FBECMY) = Fat based energy (FBE/kg) × (305MY)
 
Fat Protein based energy corrected milk yield (kcal) (FPECMY) = Fat protein based energy (FPBE/kg) × (305MY)
 
Fat Protein Lactose based energy corrected milk yield (kcal) (FPLECMY) = Fat protein lactose based energy (FPLBE/kg) × (305MY)
 
Where, the values 9.23, 5.71, 3.95 are calories of heat evolved by the complete combustion of one gram butter fat, one gram protein and one gram lactose, respectively.

It is recommended that in the light of the nutritional security of the country, genetic evaluation of  Karan-Fries bulls should be done based on fat based energy corrected milk yield or fat protein lactose based energy corrected milk yield, as it accounts for both milk production and constituent traits.

The authors are indebted to the Director and Vice Chancellor, ICAR-NDRI, Karnal, Haryana for providing the infrastructure facilities. The first author is also thankful to NDRI for providing financial assistance for the successful completion of the project.