IGF1 and IGF2 gene polymorphisms are associated with the feed efficiency of fattened lambs in Latvian sheep breads

I. Trapina¹*, S. Plavina¹, N. Krasņevska¹, J. Paramonovs¹, D. Kairisa² and N. Paramonova¹

¹Genomics and Bioinformatics, Institute of Biology of the University of Latvia, Jelgava str. 3, LV-1004, Riga, Latvia
²Institute of Agrobiotechnology, Faculty of Agriculture, Latvian University of Life Sciences and Technologies, Liela Street 2, LV-3001, Jelgava, Latvia
*Correspondence: ilva.trapina@lu.lv

Abstract:

Feed efficiency is an economically important indicator in sheep farming. The most effective technology for selecting the best feed-efficient lambs for breeding is marker association selection of genetic variations in the sheep genome as potential biomarkers. In tissue growth and differentiation, insulin-like growth factors (IGFs) play a major role: IGF1 mediates the effects of growth hormone, and IGF2 is a growth regulator, regulating skeletal muscle growth. The study aims to find possible molecular markers for feed efficiency indicators in IGF1 and IGF2 genes for Latvian sheep breeds. The exonic regions of the IGF1 and IGF2 genes were sequenced for the first time in the genomic DNA of 76 controlled, intensively fattened lambs, to search for possible genetic biomarkers. Seven polymorphic loci in the IGF1 gene and sixteen in the IGF2 gene were detected. Statistically significant associations of the IGF1 SNP rs600896367 were found with residual indicators: Residual feed intake, Residual weight gain (RWG), and Residual intake and body weight gain (RIG), and with feed efficiency and feed conversion ratio in the overall group of samples. Additionally, IGF2 SNPs New_7 and rs429576107 exhibited associations with RWG and RIG specifically in the Latvian dark-head sheep group. On average, effect of the IGF1 SNP on associated feed efficiency residuals is 3.9%, with the most pronounced impact observed in RFI. In contrast, the influence of IGF2 SNPs is comparatively lower. Our results indicate that rs600896367 and New7/rs429576107 are potential molecular markers for marker-assisted selection in sheep breeding for residual feed efficiency indicators.

Key words:

breeding, fattening, feed efficiency, insulin-like growth factor, Latvian sheep, polymorphisms

Feed efficiency indicators and hormones related to nutrient metabolism in intensive fattened lambs of sire rams of different sheep breeds in Latvia

I. Trapina¹*, D. Kairisa² and N. Paramonova¹

¹University of Latvia, Institute of Biology, Laboratory of Genomics and Bioinformatics, Jelgava street 3, LV-1004 Riga, Latvia
²Latvian University of Life Sciences and Technologies, Faculty of Agriculture, Institute of Agrobiotechnology, Liela street 2, LV-3001 Jelgava, Latvia
*Correspondence: ilva.trapina@lu.lv

Abstract:

The feed efficiency increase of each sheep indicates its profitability. Production costs and the environmental impact of animal husbandry are reduced as feed efficiency improves. The gastrointestinal tract is a source of hormones and is important in regulating feed intake and nutrient utilization. The study analyses the relationship between feed efficiency indicators and hormone levels in Latvian sheep breeds. After control fattening, blood samples were taken from 76 lambs, representatives of six Latvian breeds, for seven hormonal analyzes and seven feed efficiency indicators. Feed efficiency, Feed conversion ratio (FCR), Relative growth rate, Kleiber ratio (KR), Residual feed intake (RFI), Residual weight gain, and Residual intake were calculated from daily weight gain and amount of dry matter. Interbreed differences and relationships between indicators/hormones were identified. The best scores of feed efficiency were found for the lamb rams of the Dorper breed; the Latvian black-head was the second according to these indicators. The mean FRC for lambs was determined to be 5.13 ± 0.13 kg with a range of
2.98–10.15 kg; the mean KR was 18.11 ± 0.39 with a range of 8.78–26.88; the mean RFI was in the range of -0.51 to 0.42 kg. A statistically significant difference was found between the breeds for all feed efficiency indicators. Biochemical parameters (IGF-1, insulin, and glucose) were found to be in correlation with feed efficiency indicators. Our results show that Latvian sheep breeds differ in fattening performance. To improve breeds without crossing them, subsequent genetic analysis of breed differences is necessary.

Key words: