# Relationship Between Breed, GH and CAST Genotypes, and FA Composition in the Ovine Intramuscular Fat of Musculus Semimembranosus

## TL;DR

This study found that purebred Lithuanian Black-Headed lambs have healthier fat and better growth when specific genetic variants are present.

## Contribution

The study identifies optimal genetic combinations (BB GH and MN CAST genotypes) for improved lamb growth and healthier fat composition.

## Key findings

- Lithuanian Black-Headed lambs had healthier meat with more omega-3 and less saturated fat.
- Lambs with BB GH genotype showed highest growth rates and healthiest fat profiles.
- Crossbreeding with Ile de France, Suffolk, or Texel reduced meat quality and growth benefits.

## Abstract

This study examined how different sheep breeds and genetic variants affect the fatty acid composition of lamb and animal growth performance. Lithuanian Black-Headed lambs had healthier meat, containing more beneficial fatty acids (omega-3 and polyunsaturated fatty acids) and less saturated fat compared to crossbreds. Lambs with the MN genotype of the CAST gene grew better and had healthier fat profiles than lambs with the MM genotype. The BB genotype of the GH gene resulted in the highest growth rates. However, lambs with the AA genotype had the healthiest fat profile, with lower levels of saturated fat and higher levels of polyunsaturated fat. Crossbreeding strategies and genetic selection could be used to make lamb grow faster and produce healthier meat.

The aim of the study to evaluate relationship between breed, GH and CAST genotypes, and FA composition in the ovine intramuscular fat of musculus
Semimembranosus. To fulfil this aim, 175 blood samples were drawn by jugular vein puncture from Lithuanian Black-Headed (N43), Lithuanian Black-Headed *Ile de France (N43), Lithuanian Black-Headed *Suffolk (N44), and Lithuanian Black-Headed *Texel (N45) lambs. The lambs were weighed weekly, and the growth rate was calculated using birth weight and month weight values. Genomic DNA was extracted from blood samples taken into EDTA containing tubes, using a “GeneJET Genomic DNA Purification Kit” (Thermo Scientific, Waltham, MA, USA). The method of polymerase chain reaction and restriction length polymorphism were used to genotype growth hormone (GH) and (CAST) gene polymorphisms. Meat samples of four lamb breeds were taken for analysis (200–250 g from musculus
Semimembranosus were taken 48 h after carcass meat cooling). The fatty acid methyl esters (FAMEs) were analyzed using a gas chromatography mass spectrometry (GC/MS) instrumental technique. All data were evaluated statistically. Studies have shown that purebred Lithuanian Black-Headed lambs are born with a higher weight, so it is not advisable to mix them with Ile de France, Suffolk, or Texel breeds. Also, our research shows that the most beneficial breed are lambs that have the BB genotype of the GH gene and the MN genotype of the CAST gene, as these lambs are born with the greatest weight and gain. The meat of Lithuanian Black-Headed lambs showed the lowest content of SFA and the largest content of PUFA. The ratio ω-6/ω-3 FA varied from 2.71 (Lithuanian Black-Headed * Suffolk) to 4.52 (Lithuanian Black-Headed). Based on the research, it can be concluded that the purebred Lithuanian Black-Headed lambs had higher birth weight, therefore it is not appropriate to mix them with Ile de France, Suffolk, or Texel breeds.