Non-genetic parameters
Average, analysis of variance (ANOVA) of first lactation traits are presented in Tables 2 and 3.
First lactation 305 days or less milk yield in Karan Fries cattle
Average FL305MY was estimated as 3381.31± 37.29 kg with coefficient of variation as 31.16 %. The results are in agreement with
Divya (2012),
Singh (2014) and
Tripathy (2017) who observed similar estimate. However, the present estimate was lower than the report of
Kokate (2009) but was higher than the result of
Nehra, 2011. Overall least-squares mean of FL305MY was estimated as 3131.31 ± 35.26. Period of calving had significant effect (p<0.01) on FL305MY (Fig 1). Similar result was found by Tripathy, 2017. Season of calving had significant effect (p<0.05) on FL305MY (Fig 1) and was observed by
Kokate (2009),
Nehra (2011) and
Tripathy (2017).
Average test day milk yield in Karan Fries cattle
ATDMY was estimated as 12.30± 0.13 kg with coefficient of variation as 23.21 % and was almost in agreement to the value 10.94 ± 0.08 found by
Tripathy et al., (2017). Higher estimates than the present study in Holstein Friesian cattle was reported by
Rekik et al., (2009). Overall least-squares mean for ATDMY was estimated as 11.00 ± 0.10 kg. Period (p<0.01) and season (p<0.05) of calving had significant effect on ATDMY (Fig 2).
Mishra (2001) reported significant effect of period and season of calving on ATDMY in Karan Fries cattle.
Average test day fat percentage in Karan Fries cattle
ATDFP was estimated as 5.07± 0.08 % with coefficient of variation as 8.63 %. Lower estimate of Average lactational fat percentage was reported by
Mishra (2001) and
Sarkar et al., (2006) in Karan Fries and
Radhika et al., (2012) in HF crossbred cattle. Overall least-squares mean for ATDFP was estimated as 4.17 ± 0.007. Period of calving and age group had highly significant effect (p<0.01) whereas, season of calving was non-significant on ATDFP (Fig 3). Significant effect of age of calving in HF cattle was reported by
Verma et al., (2014) and season of calving in various breeds of cattle were reported by
Missanjo et al., (2010) and
Nyamushambaa et al., (2013). Average lactational fat yield in Karan Fries cattle in the present study was observed as 140.54± 4.14 kg with the coefficients of variation 29.56 % (Table 2, Fig 4).
Restriction patterns with PstI
PCR-RFLP analysis of each PCR products was carried out using
PstI, restriction enzyme reported by
Cohen-Zinder et al., (2005) for primer pairs for exon 14 of ABCG2 gene for all 189 animals included in the study. The restriction fragments were resolved in 2.5-3.0% agarose gel and visualized in gel documentation system. Restriction fragment sizes and corresponding genotypes of ABCG2 gene are given in Table 4. Genotyping was done according to the band patterns and for each allele and genotype, gene and genotypic frequencies were calculated.
PstI-RFLP for targeted region showed polymorphic pattern (Fig 5) with three genotypes; CC (268bp and 24bp), AC (292bp, 268bp and 24bp) and AA (292bp). Genotypic frequencies of AA, AC and CC were 0.83, 0.15 and 0.02 whereas the allelic frequencies for A and C allele were 0.91 and 0.19, respectively (Table 5).
Soltani-Ghombavani et al., (2016) in Iranian Holstein cattle also observed a much higher frequency of A allele compared with C allele (97% vs. 3%) of the ABCG2-Y581S locus. Development of crossbred cattle started, by crossing Tharparkar (T) as a Zebu breed and three exotic breeds, namely, Holstein Friesian (H), Brown Swiss (B) and Jersey (J) at National Dairy Research Institute, Karnal. Based on the performance of different genetic groups and adaptability the Breeding Committee of the Institute declared the crosses of Tharparkar and Holstein Friesian as Karan Fries (KF) with 50% to 75% of exotic inheritance of Holstein Friesian in 1982. Since then the KF animals are being maintained and improved at the NDRI through inter-se mating under progeny testing programme. The results observed in the present study support the findings of
Ron et al., (2006) who reported that the ABCG2C allele was present only in Bos taurus breed suggesting that ABCG2A is the ancestral allele, and the Y581S substitution occurred after the separation of Bos indicus and Bos taurus lineages.
Association of genotypes with breeding values for first lactation milk yield and milk composition traits
The association of ABCG2 gene with milk yield and composition traits are presented in Table 6. The SNP at ABCG2-Y581S locus amplified by primer 14 corresponded to three genotypes among which AA genotype had significant effect (p<0.036) on ATDFP with mean 4.42±0.03.
Yue et al., (2011) observed two novel SNPs (45599 A>C and 45610 A>G) in intron 7 of ABCG2 gene in Chinese Holstein cattle. They observed a significant (P<0.05) association between ABCG2 gene polymorphism and milk production traits.
Fontanesi et al., (2015) also observed that c.1742 A>C polymorphism in sires of Reggiana cattle breed is responsible for higher fat. The results observed in the present study support the findings of
Cohen-Zinder et al., (2005), who observed that animals having A allele have higher fat and protein yield.
Mousavizadeh et al., (2013) demonstrated that non-synonymous nucleotide substitution in exon 14, which is associated with fat percentage in Holstein cattle, was observed at only a 2% frequency. Additionally,
Tantia et al., (2006) indicated that the presence of fixed alleles of the ABCG2 gene is responsible for higher milk fat yields and higher fat percentages in Indian cattle (B. indicus). According to
Olsen et al., (2007) using physical mapping and combined linkage disequilibrium mapping, the QTL region of ABCG2 gene has been fine-mapped and it has been found that the ABCG2-Y581S is the only marker in perfect linkage disequilibrium with the QTL
(Olsen et al., 2007). The ABCG2-Y581S has been shown to be associated with milk production traits in Polish Holstein-Friesians (
Komisarek and Dorynek, 2009).
Yurchenko et al., (2018) found genomic signatures of selective sweeps near key genes related to economically important traits, such as the milk production (e.g., ABCG2), growth (e.g., XKR4), and reproduction (e.g., CSF2).