Keragaman gen kalpastatin (CAST) dan hubungannya dengan sifat pertumbuhan dan kualitas karkas pada domba lokal

Abstract

Calpastatin (CAST) is an indigenous inhibitor of calpain that is involved in regulation of protein turn over and growth, therefore CAST gene is an excellent candidate gene for growth and carcass trait in livestock. The objectives of this research were to identify genetic polymorphisms in the part of intron 5 - exon 6 of CAST gene, to identify the association of CAST polymorphism with growth trait, and carcass characteristics as well as meat quality in the local sheep. A PCR-SSCP method was carried out to identify the genetic variation of CAST gene from 401 samples origin from three groups of local sheep ie. Fat Tail Sheep (FTS), Thin Tail Sheep (TTS) and Priangan Sheep. In total 157 heads of TTS were grouped based on CAST genotype and raised untill three months for growth trait measurement. A number of 33 heads of sheep representing of CAST genotype (CAST-11, CAST-12 and CAST-22) were used to identify carcass and meat characterization. The results shows that most population studied were polymorphic, with genotype frequencies of CAST-11, CAST-12, CAST-22, CAST-13, CAST-23, and CAST-33 were 29.7%, 38.2%, 24.2%, 2.5%, 4.5% and 0.7% respectively. CAST-1 and 2 alleles were most commonly found in all populations with total frequency 95.8%, while rare allele was CAST-3 (4.2%) and only found in thin tail population. There were no associations between CAST polymorphisms with body weight and body linear measurement, but a significant association was found between CAST variation and daily gain. The CAST-23 and CAST-33 genotype had higher daily gain when compared to other genotypes. There were no associations between CAST polymorphisms with meat tenderness, pH, water holding capacity and cooking loss, neither with carcass weight and dressing percentage. The shoulder proportion of CAST-11 genotype was larger when compared to those of CAST-12 or CAST-22 genotype, but the lean meat proportion of CAST-22 in shoulder, rack and loin was higher (P<0.05) when compared to the CAST-11 but it did not differ with CAST-12. The fat percentage of CAST-11 genotype was the highest among the genotypes. The CAST-22 genotype had higher lean meat percentage compared to the CAST-11 genotype. Its concluded that CAST genes were polymorphic and had a significant association with growth trait and carcass quality in local sheep.

Domba lokal adalah salah satu sumber daya genetik yang sangat potensial untuk dikembangkan. Hal ini disebabkan domba lokal memiliki beberapa kelebihan yakni bersifat prolifik, daya adaptasi terhadap lingkungan dan penyakit yang lebih tinggi, siklus produksi relatif lebih singkat serta relatif sedikit membutuhkan modal. Selain itu, di beberapa daerah yang padat penduduknya seperti pulau Jawa, daging domba mampu mensubstitusi sebagian daging sapi yang masih harus diimpor setiap tahun. Nilai karkas domba sangat dipengaruhi oleh total produksi daging, distribusi dan proporsi daging pada karkas. Gen kalpastatin (CAST) diketahui memiliki hubungan dengan sifat kualitas karkas dan daging pada ternak. Kalpastatin terlibat dalam beragam proses fisiologi dalam tubuh ternak seperti pengaturan turn over protein, pertumbuhan, fusi dan migrasi mioblast. Diduga keragaman gen CAST mempunyai hubungan dengan pertumbuhan dan potensial digunakan sebagai marka gen untuk sifat pertumbuhan pada ternak. Kalpastatin berperan dalam menghambat fungsi enzim kalpain yang terlibat dalam mengatur turn over protein dan pertumbuhan. Penelitian ini terbagi dalam tiga tahapan yaitu 1). Identifikasi keragaman gen CAST pada populasi domba lokal, 2). Hubungan keragaman gen CAST dengan sifat pertumbuhan pada domba lokal, 3). Hubungan keragaman gen CAST dengan kualitas daging dan karkas domba lokal. Metode PCR-SSCP digunakan pada penelitian tahap pertama untuk mengidentifikasi variasi pada gen CAST. Sebanyak 401 ekor domba lokal dari 8 sub populasi digunakan dalam penelitian ini, tiga group merupakan Domba Ekor Tipis (DET) dari Sukabumi, UP3J Jonggol dan Kissar, sedangkan sisanya antara lain domba Priangan dari Margawati dan Wanaraja serta Domba Ekor Gemuk (DEG) dari Donggala, Sumbawa dan pulau Rote. Pada tahap kedua, sebanyak 157 ekor DET yang dikelompokkan berdasarkan genotipe gen CAST dipelihara selama tiga bulan dan diukur parameter pertumbuhannya seperti bobot badan, PBB harian serta ukuran morfometriknya. Pada tahap ketiga sebanyak 33 ekor DET yang mewakili tiga genotipe CAST-11, CAST-12 dan CAST-22 diidentifikasi kualitas karkas dan dagingnya.