Online First Article β casein Polymorphism in Indigenous and Exotic Cattle Breeds of Pakistan Shakila Mumtaz 1 , Khalid Javed 1 , Muhammad Dawood 1 *, Muhammad Imran 2 , Asad Ali 1 and Nazia Ramzan 1 1 Department of Livestock Production, University of Veterinary and Animal Sciences, Ravi Campus Pattoki, Pakistan 2 Institute of Biochemistry and Biotechnology, University of Veterinary and Animal Sciences, Lahore, Pakistan Article Information Received 07 March 2019 Revised 21 July 2019 Accepted 15 December 2020 Available online 31 May 2021 Authors’ Contribution MD and KJ planned and supervised the study. SM and NR performed the study. AA and MI helped in data analysis. MD and SM wrote the article. AA contributed to refnement of the article. Key words DNA sequencing, Beta casein, Genetic variations, PCR-RFLP, A1 and A2 Genotype Milk composition depends largely on the breed’s genetics and ration fed. Different proteins can be found in milk. Beta-caseins are thought to be more important because some serious health-related issues in humans have been reported with the consumption of A1 milk (mutated casein variant). This study was planned to investigate the polymorphism in the beta-casein gene (CSN2) in Sahiwal (40), American Holstein Friesian (40) and the crossbred (Sahiwal × HF) (50). PCR-RFLP and conformational sequencing were performed to investigate the beta-casein polymorphism. Results of the present study showed that there was not any mutated genotype (A1A1) available in all of the three breeds. All three breeds possess dominant genotype A2A2 with genotypic frequency (0.925, 0.4, 0.64) respectively and we have also found some heterozygous genotypes A1A2 in all breeds with genotypic frequency (0.075, 0.6, 0.36) respectively. Findings of the present study revealed that A2 (the dominant allele) is present with a pretty much higher frequency (0.9625, 0.7, 0.82) in all the three studied breeds and the mutated allele A1 is present with very low allelic frequency (0.037, 0.3, 0.18). M ilk proteins constitute 3% of the total chemical components of milk. Caseins constitute 80% of total milk proteins (Ho et al., 2014). Three major types of caseins are found in milk which include alpha, beta and kappa casein. Beta-caseins are the most important proteins found in milk and share the major part about 30% of the milk protein (Ho et al., 2014; Malarmathi et al., 2014; Boro et al., 2016). There are twelve different genetic forms of beta-casein available, among those two A1 and A2 are more common and have an important role regarding milk production and the human health aspect (Farrell et al., 2004). In cattle, the dominant variant for beta-casein protein was A2 beta-casein. Many years ago, a natural mutation appeared in cows from European breeds which have resulted in another casein variant A1 beta-casein and producing A1 milk (Boro et al., 2016). Casein protein is composed of 209 amino acids and a change at 67 th amino acid (proline to histidine) can cause A2 milk to A1 milk. Proline (CCT) is responsible for A2 milk and histidine (CAT) is responsible for A1 milk (Ul-Haq et al., 2014; * Corresponding author: muhammad.dawood@uvas. edu.pk 0030-9923/2021/0001-0001 $ 9.00/0 Copyright 2021 Zoological Society of Pakistan Ho et al., 2014; Singh et al., 2015). Some other variants like B, C, D, E, F, G, H1, H2, and I are also found but are not as importance as A1 and A2 (Farrell et al., 2004). Beta-casein variants A1 is responsible for causing serious health problems for human such as ischemic heart disease, arteriosclerosis, type 1 diabetes (DM-I) and unexpected infant death syndrome (Laugesen and Elliott, 2003; Birgisdottir et al., 2006; Caroli et al., 2009; Massella et al., 2017). Currently increased consumption of dairy products has been considered to be associated with serious health risks and worst symptoms of some disorders like gastrointestinal malfunction, immunity related issues and heart diseases (Barnett et al., 2014; Ul-Haq et al., 2014). Some of these effects are linked with beta-casomorphin-7, a peptide associated with A1 milk consumption. Beta- casomorphin-7(BCM-7) adversely affects the digestibility, reduces the production of lymphocytes and ultimately affects the immunity (Trompette et al., 2003; Zoghbi et al., 2005). The present study aims at investigating the beta- casein polymorphism in indigenous cattle Sahiwal, exotic breed American Holstein Friesian (HF) and crossbred (Sahiwal × HF). This study will help in selection of superior milk and breed improvement programs. ABSTRACT Pakistan J. Zool., pp 1-4, 2021. DOI: https://dx.doi.org/10.17582/journal.pjz/20190307030303 Short Communication