163 *Corresponding author email: shwetagb24@gmail.com Sahiwal is considered one of the best indigenous milch breeds of cattle and utilized widely for improvement of i ndi genous stock in many tropical countries. Various approaches has been tried to increase their productive performance, selection based on molecular biomarkers is one of them. Among different molecular biomarkers, growth h ormone (GH) gene is considered one of the most significant genes that can influence lactation traits in dairy animals. Bovine GH (bGH) is a single copy gene that spans 1,800 bp, associated with chromosome region 19q26 in bovine genome (Hediger et al. r 1990), and it consists of five exons separated by introns (Cole et al. 2011). Several polymorphisms were identified in the GH gene. Leucine or valine amino acid substitutions at residue 127 in GH exist due to allelic polymorphism (Sartore and Di Stasio 2000). A polymorphic site for Msp 1 restriction endonuclease was detected by Cowan et al. (1989) and Hilbert et al. (1989) and the polymorphism being localized in intron 3 of the GH gene in position 1,547 (Zhang et al. 1993). Studies on the effect of the GH-Msp1 polymorphism on production traits in Sahiwal cattle are quite advanced, but the results obtained by various workers are not always in agreement. The aim of this study was to estimate the allelic frequencies at the GH-Msp 1 loci and to investigate the associations of t his polymorphism and first milk production traits in Sahiwal cows. Sahiwal cows (305) maintained at Livestock Research Centre of ICAR-National Dairy Research Institute (NDRI), Karnal during 1993–2016 were recruited for the present study . Sahiwal cows with a complete lactation were included the statistical analysis (180 Sahiwal cows with minimum 100 days of lactation length and 500 kg of milk yield). The cows with first lactation were used. Blood samples along with records of first lactation 305 days milk yield (FL305DMY), first lactation total milk yield (FLTMY) and first lactation length (FLL) were collected from 305 lactating Sahiwal cattle. DNA from whole blood samples was isolated as per the standard method with slight modification (John et al. 1991). For preparing the working solution of genomic DNA, the stock was diluted to100 ng/ Indian Journal of Animal Sciences 90 (4): 655–657, April 2020/Short communication https://doi.org/10.56093/ijans.v90i4.104226 Growth hormone-Msp1 loci polymorphism and its association with first lactation traits in Sahiwal cattle SHWETA SACHAN * , I D GUPTA, ARCHANA VERMA, M R VINEETH and REBEKA SINHA ICAR-National Dairy Research Institute, Karnal, Haryana 132 001 Received: 12 April 2019; Accepted: 22 August 2019 Keywords: Growth hormone, Lactation traits, Msp1, PCR-RFLP, Sahiwal cattle μL and then stored at –20°C for utilizing it as DNA template in PCR. Agarose gel electrophoresis and UV spectrophoto- meter were used to analyze the quality and quantity of DNA. The ratio between OD 260 and OD 280 was calculated for each DNA sample and sample with ratio of 1.8 was considered good and used for analysis. The GH-Msp 1 genotypes were analyzed using the PCR-RFLP method. A 328 bp fragment of intron 3′ of GH gene was amplified by PCR using primer F: 5′ -CCCACGGGCAAGAATGAGGC- 3′ and R: 5′ - TGAGG-AACTGCAGGGGCCCA-3′ (Mittra et al. 1995). The PCR protocol to amplify that fragment was denaturation at 95°C for 5 min for 1 cycle, denaturation at 94°C for 30 sec, primer annealing at 68.5°C for 30 sec, PCR products synthesis at 72°C for 30 sec and final synthesis at 72°C for 10 min for 40 cycles. Amplified DNA was digested by Msp1 enzyme at 37°C for 12 h. Reaction mixture consisted of 10 μl PCR product, 2 μl buffer, 0.3 μl (1U) Msp1 and 7.7 μl ddH 2 O. The digestion products were electrophorated by horizontal electrophoresis (90 volts, 50 min) using 2% agarose gel in 1×TBE and 1.0 μM ethidium bromide to identify polymorphism of alleles based on the length of the band. Direct counting of the bands appearing in the gel was used for determination of genotypic frequency in the population. Data for 305 day milk production in first lactation including FL305DMY, FLTMY and FLL were obtained from the record room of the Animal Genetics and Breeding Division of ICAR-NDRI, Karnal. Statistical calculations were performed using SAS procedures. The effect of GH genotypes on the first milk production traits of cows were analyzed using the GLM procedure. The significant effect of SNP variants on first production traits in Sahiwal cows was analyzed using the following model: Y ij = μ + G i + e ij where Y ij , the lactation trait of j th animal belonging to i th genotype; μ, the overall population mean; G i , the effect of i th genotype and e ij , the random error associated with Y ij observation and assumed to be normally and independently distributed with mean zero and constant variance, i.e. NID (0,σ 2 e ). The genotypic frequencies were calculated using various RFLP patterns. The allelic frequencies wer e