author(s)
Mathivathani K, Radhika G and Aravindakshan TV

abstract
Goats are recognised as important components of livestock farming system and they play a very useful role in providing a steady income to the people of economically backward sections throughout the year. Goat milk is usually recommended for aged persons, infants and convalescent people due to its better digestibility, which can be attributed to smaller diameter of fat globules found in goat milk when compared to cow milk. In Kerala, two native goat breeds, Malabari and Attappady Black vary significantly in milk production. Recent advances in molecular techniques provide opportunities for genetic improvement at a faster pace. Double digest Restriction Associated DNA Sequencing (ddRADseq) is a modern approach for identification of Single Nucleotide Polymorphisms (SNP) across populations. The ddRADseq technique was performed in three pooled samples (ten each) of high and low milk producing Malabari and Attappady Black goats. By using bioinformatics tools, the SNPs were discovered and analysed. A total of 42 candidate genes affecting milk quantity and quality were selected from literature and the entire data was screened for variants in these candidate genes. Out of these candidate genes, gene Butyrophilin (BTN1A1) obtained from ddRADseq, was selected for expression study in the present study as researchers showed that BTN1A1 was significant associated with growth trait and milk yield in Saanen goats. BTN1A1 is a transmembrane glycoprotein, specifically expressed on the epithelial cells during lactation. In the current study, BTN1A1 was selected for quantitative polymerase chain reaction (qPCR). In this method, RNA was isolated from milk of late stages of lactation from six each of Malabari and Attappady Black goats using TRIzol LS reagent. All 12 samples of RNA were converted to cDNA using Verso cDNA synthesis kit. For qPCR, target gene (BTN1A1) and reference gene (β-actin) were standardized. The relative quantification of gene expression was carried out using Illumina Eco® Q-RT PCR system using SYBR green chemistry. In the current study, expression of BTN1A1 was comparatively higher in Malabari than Attappady Black goats and this difference was found to be statistically significant (p≤0.05). The relative expression of BTN1A1 was 6.74 fold higher in Malabari than Attappady Black goats.