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To achieve sustainable lamb production, it is crucial to determine the optimal slaughter age for maximum economic efficiency and have a comprehensive understanding of breed characteristics. This study focuses on evaluating different nonlinear models to determine the optimal slaughter age for Karacabey Merino and Kıvırcık lambs, renowned for their early development and superior meat quality, respectively. The dataset comprised age-related live weight data from 98 lambs, including 36 female and 15 male Kıvırcık lambs, as well as 33 female and 14 male Karacabey Merino lambs. Six models, namely, negative exponential, Brody, Gompertz, logistic, Bertalanffy, and Richards were utilized to analyze the data. The model parameters were estimated through an iterative process, and their goodness of fit was evaluated using various metrics. The adjusted coefficient of determination for male Kıvırcık lambs was 0.9755, while female Kıvırcık lambs exhibited a lower value of 0.8912. For Karacabey Merino lambs, males had an adjusted coefficient of determination of 0.9534, while females had a slightly lower value of 0.9044. The study concluded that the Brody model provided more accurate predictions for the growth curve of these sheep breeds compared to the other models. [ABSTRACT FROM AUTHOR]

Simple Summary: Molecular genetic approaches have been developed over the last half-century to identify genetic variation associated with economically important growth performance and carcass characteristics. In the livestock sector, identifying and localizing the genes responsible for each trait, as well as selecting beneficial alleles based on live animal experiments, meat production, and nutritional quality, have played an essential role in improving productivity. The purpose of this study is to examine the association between IGF1 5′UTR polymorphisms and various growth and carcass parameters of meat-type sheep breeds raised in Turkey. A total of eight nucleotide changes were identified that were able to characterize three IGF1 5′UTR variants, and certain variants were associated with variations in chest width and leg circumference. The P1 variants had a leaner profile and the P2 variants had a higher percentage of rack and loin. Nucleotide sequence variations in IGF1 5′UTR could, thus, be exploited for marker-assisted selection in order to enhance growth and production attributes and carcass quality. This investigation was conducted to determine how the growth and carcass traits of meat-type sheep breeds raised in Turkey are associated with IGF1 5′UTR polymorphisms. Overall, 202 lambs from five breeds were evaluated. We identified eight nucleotide changes (seven substitutions and one deletion) in three variants of IGF1 5′UTR by SSCP analysis and nucleotide sequencing. It was found that the P1 variants had a unique deletion (g.171328230 delT), while the P2 variants were identified by SNPs rs401028781, rs422604851, and g.171328404C > Y. The P3 variants possessed one heterozygous substitution (g.171328260G > R) and three homozygous substitutions (g.171328246T > A, g.171328257T > G, g.171328265T > C) not observed in P1 or P2. Based on the growth and production traits, a statistically significant difference was found only in chest width at weaning (p < 0.01) and leg circumferences at yearling (p < 0.05). The P1 variants showed a leaner profile with a higher Musculus longissimus dorsi, but the differences were not significant (p > 0.05). The P2 variants had a higher percentage of rack (p < 0.01) and loin (p > 0.05). Moreover, there was no discernible difference between variants, even though the P3 variants had a higher percentage of neck and leg and the P1 variants had a higher percentage of the shoulder. It is concluded that nucleotide changes in IGF1 5′UTR could be exploited utilizing a marker-assisted selection technique to increase growth and production attributes, as well as carcass quality traits. [ABSTRACT FROM AUTHOR]

This study is set out to evaluate the effects of callipyge (CLPG) gene, attributed to sheep affecting growth and meat quality, on carcass and sensory trait of most preferred meat-type lamb (Kıvırcık, Karacabey Merino, Ramlıç, German Black-Head Mutton x Kıvırcık, Hampshire Down x Merino) in the western part of Turkey. Two datasets were used: (i) 177 lambs (66 males, 111 females) to determine genotype and allele frequencies; (ii) 48 genotypically identified male lambs for the assessment of carcass and meat sensory quality. It was found that homozygous (NN) and heterozygous (MN) conditions of the CLPG gene were observed in all sheep breeds, except Ramlıç which exhibits only NN. No significant differences were observed in CLPG genotypes for slaughter weight, cold carcass weight, and cold dressing percentage (p > 0.05). On the other hand, the effect of genotype on neck percentage was significant (p < 0.01), and lambs expressing CLPG genotype (MN) had a higher neck percentage. Not significantly, but numerically the MN genotype had a higher percentage of the shoulder, rack, and leg than the NN genotype, while the NN genotype had a higher percentage of loin (p > 0.05). Similarly, the effect of genotype on meat quality assessment was not significant (p > 0.05); however, shear force, water holding capacity, and cooking loss of the NN genotype were higher than the MN genotype. Indeed, no interaction between genotype and time was observed on the color parameter of the Longissimus thoracis et lumborum muscle at various storage periods (p > 0.05). The findings suggest that all meat-type sheep breeds (except Ramlıç) were polymorphic, suggesting that heterozygous individuals who received the CLPG mutation from the sire should be adopted in selection programs to improve carcass traits. [ABSTRACT FROM AUTHOR]

• CLPG mutated sheep had higher IBF and BCI values. • BCI and IVF should be adopted as performance criteria and etiological comparisons in breeding schemes. • CBP was the differentiation point of CLPG genotypes. • BL, CC, CW, WH, IBF, BCI, and LW could be used for the morphometric characterization of CLPG genotypes. This study is set out to examine the relationship between the callipyge (CLPG) gene, attributed to sheep affecting growth and meat quality, and body indexes of meat-type sheep breeds to assess its feasibility in using it genomic selection programs. For this purpose, blood samples were collected from 177 lambs (66 male, 111 female) of five different sheep breeds (Kivircik, Karacabey Merino, Ramlic, German Black-Head Mutton × Kivircik, Hampshire Down × Merino) to identify M (mutant) and N (normal) alleles and genotypes. Live weight (LW) and morphometric measurements were taken on the 90th, 180th, and 360th day of the study. The principal component analysis results show that four morphometric measurements (body length, BL; chest circumference, CC; chest width, CW; withers height, WH) and two body indexes (index of body weight, IBF; Baron-Crevat index, BCI) with LW could be used to the morphometric characterization. It was found that the cannon bone perimeter (CBP) was the differentiation point of CLPG genotypes. While a lower to moderate correlation was observed between CBP to CC, LW, CW, chest depth (CD), and rump width (RW) in the NN genotype, no significant correlation was observed in the MN genotype. This investigation also revealed that BCI and IBF were the two body indexes that should be adopted into breeding schemes as a performance and etiological comparison of animals, especially in marker-assisted selection schemes due to well-reflecting animal current status. [ABSTRACT FROM AUTHOR]