The relationship of Diacylglicerol acyltransferas (DGAT1) Gene Diversity to Friesian Holstein Dairy Cattle‘s Milk Production and Fatty Acid Profile.

Abstract

Milk fatty acid composition is influenced by genetic and environmental factors. Milk fat composition can be changed by nutrition and genetic improvement. Genetic improvement can be done through selection to genes which have associated strongly with milk production and milk fat percentage. A study of quantitative trait locus mapping (QTL) in cattle has been resulted that from the identification of polymorphism (K232A) in the gene coding for acyl CoA is diacylgliserol acyltransferase1 (DGAT1). DGAT1 is a key enzyme in the synthesis of triglycerides and has a strong effect on milk fat percentage and milk production. The effect of DGAT1 mutations in milk fat composition of dairy cattle in Indonesia has not been done. This study aims to, firstly, to identify the genetic diversity of DGAT1 gene in cattle Friesian Holstein (FH), secondly, to test the relationship between genotype diversity DGAT1 gene with milk production and milk fatty acid profile. The study consisted of two steps. The first was identification of DGAT1 gene diversity in FH dairy cows. The second was testing relationship of DGAT1 gene diversity to milk production and milk fatty acid profile. The identification of DGAT1 gene diversity used blood samples which collected from 7 populations in Central Java and West Java. There were 300 heads dairy cattles used in this research which taken from BBPTU Baturraden SP (123), BET Cipelang (32), BPPT Cikole (36), Cilumber farm (34) Pasir Kemis Farm (34). Genetic flow from the male to the lactation female viewed by using samples which derived from BIB Lembang (16) and BBIB Singosari (28). The identification of the relationship of DGAT1 gene diversity to milk production and milk fatty acid profile used milk samples which collected from BBPTU Baturaden’s Dairy Cattle (40). Milk samples were collected by a single test day in which milk production in the morning and in the afternoon is calculated. Such milk samples were collected from dairy cattle which has 1-6 lactation periods and 1-12 month lactation. The data of milk fatty acid obtained through a laboratorium test results which using Gas Chromatography method. DNA extraction has been done by using modified (Sambrook et al. 1989). Determination of the genotype of each individual was conducted with Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) approach. Gene diversity has been seen by counting the frequency of allele, genotype frequencies and heterozygosity values. The relationship between DGAT1 gene genotype variants with milk production and milk fatty acid profile was calculated based on the General Linear Model (GLM) method using SAS 9.1 software. DGAT1 gene fragment amplification was carried out by using the Polymerase Chain Reaction (PCR) method which resulted products throughout 411 bp. Genotyping DGAT1 gene fragment were resulted two genotypes KK and KA. KK genotype is shown with 411 bp fragment length and AK genotype is shown with 203, 208 and 411 bp fragment length. Frequiency of AK genotype (73%) at seven FH dairy cows population was higher than the KK genotype (27%) and AA genotype (0%). The phenomenon of the lack of AA genotype of FH cows, either at the farm or at the seeds center institution, was influenced by the source of male cattle which used in artificial insemination (AI) activity. Males cattle were used for AI in lactating females were generally derived from BIB Lembang and BBIB Singosari. Based on the analysis result, AA genotypes were not found in bulls from BIB Lembang and BBIB Singosari and A allele frequencies in bulls was low. Allele frequencies of seven cattle populations of FH resulted allele K (64%). That was higher than A allele (36%). This research resulted that gene DGAT1 on observed FH dairy cattle from seven populations had polymorphic characteristic due to there were found two types of alleles ( K allele and A allele). Observation heterozygosity values (Ho) of FH cattle population from seven different locations ranged between 0313-0938. Expected heterozygosity values (He) of FH cattle population from seven different locations ranged between 0264-0498. The highest of observation heterozygosity values (Ho) was FH dairy cattle from BET Cipelang (0.938) and the lowest was FH dairy cattle from BIB lembang (0.313). Whereas, the highest of heterozygosity values (He) was FH dairy cattle population from Cipelang and the lowest one was came from BIB Lembang (0.264). A high value of the observation heterozygosity (Ho) shows the diversity of alleles in the population. Assessment of the effect of DGAT1 gene variant genotype to average protein content of milk showed that cows with KK genotype tended to produce higher milk protein content, namely 3.12%. Such milk protein content higher than if we compared with AK genotype (3.06%), although based on statistically analysis the effect was not significsntly different (P<0.05). FH dairy cattle with KK genotype also tended to produce more milk fat (3.32%) than AA cows (3.20%). Value of protein content, fat content, specific gravity and solid non fat (SNF) in FH dairy cattle with genotype KK and AK have apropriated with SNI 01-3141-1998 standard of quality requirements of fresh milk (SNI, 1998). DGAT1 gene does not significantly affected the unsaturated fatty acids (myristoleic, palmitoleic, oleic, eurat, linolenic, and arachidonat eicosatrinoat). Nevertheles, DGAT1 gene significantly affected (P<0.05)nervonat acid (C24: 1).