PRKAG3基因在骨骼肌中的营养代谢调节作用及其对肉质的影响

PRKAG3是近年来确定的一个影响猪肉pH、肉色以及系水力的主效基因,其突变R200Q与过量肌糖原含量有关,被认为是汉普夏猪发生RN-突变的根本原因。AMPK-γ3复合物在糖酵解骨骼肌中对糖和脂肪的代谢有着独特的调节作用。本文系统综述了PRKAG3基因在骨骼肌中营养代谢调节作用和对肉质的影响及其基因表达的调控,为从分子水平深入开展肉质的研究提供参考。     

Effect of chicken egg yolk antibody against adipose tissue plasma membranes on carcass composition and lipogenic hormones and enzymes in pigs

Chicken egg yolk antibody against pig adipose tissue plasma membranes (AIgY) was raised and used in the present experiment to evaluate the effect of dietary AIgY supplementation on pig growth and carcass composition. 160 crossbred (Duroc–Jersey × Landrace·Meishan) pigs, with initial live body weight of 27.5 ± 2.4 kg, were treated with AIgY or non-immunized control egg yolk powder (NIgY) at the inclusion level of 75 mg/kg diet. Following a 104-day trial, the pigs were slaughtered for analyzing the carcass and meat quality traits. The perirenal, mesenteric and subcutaneous fat depots were weighed and the diameter of adipocytes from different fat depots was measured with histological methods. Serum concentrations of insulin and leptin as well as the activities of malic enzyme (ME) and lipoprotein lipase (LPL) in adipose tissue were measured. Dietary supplementation of AIgY enhanced average daily gain and feed efficiency by 13.03% (P < 0.01) and 7.49%, respectively, with no influence on feed consumption. AIgY increased the lean mass by 10.3% (P < 0.01) without affecting the dressing percentage. Backfat thickness at 6th–7th rib and the weights of perirenal, mesenteric and subcutaneous fat depots were reduced by 24.14% (P < 0.01), 27.27% (P < 0.05), 20.42% (P < 0.01) and 29.21% (P < 0.01), respectively. Dietary supplementation of AIgY reduced the size of adipocytes in all the three fat pads (P < 0.05). The meat color was improved whereas the marbling score, the intramuscular fat content, and pH₄₅ of the longissimus muscle remained unaffected. Serum concentration of non-esterified fatty acids (NEFA) was significantly increased (P < 0.01) while urea-N content was reduced (P < 0.05). No alterations were detected for the serum levels of triacylglycerides (TG) and glucose. Serum concentrations of insulin and leptin were decreased by 26.19% (P < 0.05) and 26.53% (P < 0.05), respectively. LPL activity in adipose tissue was depressed significantly (P < 0.05) without affecting ME activity. This study demonstrates that dietary supplementation of AIgY can effectively improve growth and carcass composition of pigs and the changes of serum insulin and leptin levels as well as the tissue LPL activity may be involved in the acting mechanism.     

Effects of GHR gene polymorphisms on growth and carcass traits in Zebu and crossbred beef cattle

The growth hormone receptor (GHR) is the cell surface receptor for growth hormone (GH) and is required for GH to carry out its effects on target tissues. The objectives of the present study were to estimate the allele and genotype frequencies of the GHR/Alu I gene polymorphism located in the regulatory region in beef cattle belonging to different genetic groups and to determine associations between this polymorphism and growth and carcass traits. Genotyping was performed on 384 animals, including 79 Nellore (Zebu), 30 Canchim (5/8 Charolais + 3/8 Zebu), 30 Simmental × Nellore crossbred and 245 Angus × Nellore crossbred cattle. Alleles Alu I(+), Alu I(−) and Alu I(N)–null allele–were evidenced for the GHR/Alu I polymorphism and the frequency of the Alu I(N) allele was significantly higher than the frequency of the Alu I(+) and Alu I(−) alleles in all genetic groups. Genotype Alu I(N/N) of the GHR/Alu I predominated in Nellore animals, while the Alu I(N/+) and Alu I(N/−) predominated in the other genetic groups. In the association studies, traits of interest were analyzed using the General Linear Model (GLM) procedure of the SAS program and least squares means of the genotypes were compared by the Tukey test. Significant associations (P < 0.05) were observed between the Alu I(N/N) genotype of the GHR/Alu I polymorphism and lower weight gain and body weight at slaughter, although a confounding between genotypes and genetic groups may have occurred.     

灌胃左旋甲状腺素(L-T4)对妊娠小鼠胎盘中DIO3基因表达及胚胎数的影响

旨在探究小鼠胚胎发育过程中DIO3的表达模式和灌胃左旋甲状腺素(L-T4)对孕鼠胎盘中DIO3基因表达和胚胎数的影响,以期为研究妊娠期母体甲状腺激素异常提供基础数据.本研究以6周龄健康昆明小鼠(雌鼠70只,雄鼠35只)为试验对象.雌鼠经适应性饲养1周后,腹腔灌胃10 U PMSG(溶于0.3 mL生理盐水),正常饲喂4...     

Distribution of the mutant allele of the DMRT3 gene associated with ambling gaits in Japanese native horse populations

There are currently eight native horse populations in Japan, namely, Hokkaido, Kiso, Noma, Taishu, Misaki, Tokara, Miyako, and Yonaguni horses. Since locomotion traits, including gaitedness, are important for riding and packing horses, the genetic properties associated with these traits could be informative for understanding the characteristics and history of these horses. In this study, we investigated the distribution of the mutant allele of DMRT3 gene (DMRT3:p.Ser301Ter) associated with ambling gaits in the Japanese native horse. We also examined haplotypes of SNPs in the 83‐kb region including DMRT3 gene by genotyping four SNPs in this region. The results revealed the presence of DMRT3:p.Ser301Ter in the Hokkaido and Yonaguni populations at allele frequencies of 0.18 and 0.02, respectively, and the observed haplotype associated with DMRT3:p.Ser301Ter was estimated as the most common haplotype in the horses in the world. Since DMRT3:p.Ser301Ter has been hypothesized to spread across Eurasian continent from Medieval England after 850 to 900 CE, our findings of the presence of DMRT3:p.Ser301Ter with the common haplotype in the Japanese native horses will provide a new insight into the history of the Japanese native horse, such as considerable level of gene flow from Eurasian continent after 850 to 900 CE.     

Allelic frequencies of PRKAG3 in several pig breeds and its technological consequences on a Duroc × Landrace‐Large White cross

The allelic frequencies of PRKAG3 gene (the RN gene) have been investigated in several pig breeds. R200Q mutation appear only in Hampshire pigs, whereas V199I mutation is most abundant in Iberian, Porco Celta or Bizaro, and less in breeds selected for muscularity as Duroc, Landrace and Pietrain. A thorough study of phenotypic effects of V1991 has been performed in a Duroc × Landrace‐Large White cross. 199I homozygous pigs show increased pH₂₄ values in ham homogenates and loin (0.14 and 0.16 pH units, respectively) compared to 199V homozygous ones. Meat of 199I homozygous pigs exudates 42.6% less fluid and is darker (2.46 ‘L’‐value units). 199I homozygous pigs are fatter (4.2 mm more backfat thickness) and contain less muscle mass in ham (1.0 percentage points) and shoulder (2.7 percentage points), than 199V homozygous ones. 199I homozygous pigs contain 7.3% less protein in the belly and 8.5% more fat in shoulder muscle mass than 199V homozygous pigs. 199I homozygous pigs have also superior functional properties: better gelling (22.8% larger G′ value) and emulsion capacities (14 percentage points less of total exuded fluid), and higher curing yield in the belly (6 percentage points more). These data support the adipogenic character of the V199I mutation. The advantages and disadvantages of selecting any of the two PRKAG3 alleles for position 199 are discussed.     

The bovine annexin 9 gene (ANXA9) is significantly associated with milk-fat yield in a Spanish Holstein–Friesian population

On the basis of QTL studies for milk-fat yield trait on BTA3, annexin 9 protein (ANXA9), fatty acid transport protein type 3 (SLC27A3) and diacylglycerol O-acyltransferase 1 (DGAT1) were selected as candidate genes. Three different single nucleotide polymorphisms (SNPs) of bovine ANXA9, SLC27A3 and DGAT1 genes have been tested in a selective genotyping design for milk-fat yield. Significant allele frequency differences were found for ANXA9 (p = 0.02), in Holstein–Friesian animals with high and low breeding values for milk-fat yield. Regression analysis also showed a significant effect (p = 0.0207) between estimated breeding values (EBVs) for fat milk content and ANXA9 polymorphism. So ANXA9 gene falls into a significant quantitative trait loci interval for milk-fat yield that was previously reported on bovine chromosome 3 in other dairy populations. Our results suggest that the ANXA9 gene polymorphism or a linked segregating QTL contributes to variation in milk-fat yield.     

Effects of corn gluten feed inclusion at graded levels in a corn-soybean diet on the ileal and fecal digestibility of growing pigs

Background

This study aimed to determine the effect of the inclusion of corn gluten feed (CGF) on the apparent and standardized ileal digestibility of protein and amino acids and the apparent ileal and total tract digestibility of energy in growing pigs. The study was performed using 16 barrows (weight, 45.3 ± 4.5 kg) that were fitted with a T cannula at the terminal ileum. There were four treatments: a corn-soybean diet without CGF and three corn-soybean diets containing increasing levels of CGF (65, 130, and 195 g/kg). Data were analyzed according to a randomized complete block design, four blocks with four pigs each (one pig per treatment). The trend of the response (linear or quadratic) was determined using orthogonal contrasts, and when a linear effect was determined, a linear equation was obtained.

Results

The results showed that the inclusion up to 195 g/kg of CGF in the corn-soybean diet did not diminish the ileal digestibility (apparent and standardized) of protein and amino acids (P > 0.05), except that of phenylalanine, cystine, and proline. A linear decrease (P < 0.05) per gram of CGF added to the diet in the apparent and standardized ileal digestibility of phenylalanine (0.011 and 0.015 percentage units, respectively), cystine (0.048 and 0.043 percentage units, respectively), and proline (0.045 and 0.047 percentage units, respectively) was noted. Similarly, ileal digestibility of dry matter and energy were adversely affected (reduced by 0.028 and 0.025 percentage units, respectively, per gram of CGF increment in the diet). A significant (P < 0.05) linear reduction in total tract digestibility with increase in CGF amount in the diet was observed for energy (0.027 percentage units), dry matter (0.027 percentage units), crude protein (0.020 percentage units), and neutral detergent fiber (0.041 percentage units) per gram of CGF added to the diet.

Conclusion

CGF did not affect the ileal digestibility of protein and most amino acids but reduced the ileal and total tract digestibility of energy.     

Evaluation of tagasaste (Chamaecytisus palmensis) forage as a substitute for concentrate in diets of sheep

A feeding trial was carried out for 90 days to asses the supplementing effect of tagasaste forage as a substitute for a concentrate supplement (wheat bran–noug seed cake (Gizotia abyssinica) mixture in 3:1 proportion) using 24 Menz male sheep (initial weight of 18.3 ± 1.6 kg). The sheep were fed on natural pasture hay as basal diet. The treatments were iso-nitrogenous supplements of 100% concentrate offered at 200 g DM/sheep/day (T1), 67% concentrate + 33% tagasaste (T2), 33% concentrate + 67% tagasaste (T3) and 100% tagasaste (T4). Digestibility tests of treatment diets were done for 10 days following the feeding trial using the same experimental animals. At the end of the experiment, carcass parameters were also evaluated. In situ degradability of feeds was determined using three rumen fistulated crossbred steers. Tagasaste forage contains more CP (215 g/kg), ADF (221 g/kg), ADL (69 g/kg); and less NDF (351 g/kg) compared to the concentrate. The concentrate had a high immediately soluble fraction (a), and a low insoluble but potential degradable matter (b), while tagasaste had a low a and higher b values and the overall potential degradability was 755, 702, and 586 g/kg, for tagasaste, concentrate and natural pasture hay respectively. Tagasaste forage had also shown higher rates of degradation (c) compared to the concentrate which might increase the total effective degradability. In the feeding trial the supplements made 26.8, 27.0, 28.3 and 29% of the total dry matter (DM) intake for T1, T2, T3, and T4, respectively. Increasing the inclusion of tagasaste forage significantly (P < 0.01) decreased the daily total DM intake of the basal diet and total metabolizable energy (ME), and increased the CP intake. The average weight gain of sheep did not show significant difference (P > 0.05), but had a decreasing trend, with 44.4, 41.4, 38.9 and 38.1 g/sheep for T1, T2, T3, and T4, respectively. The in vivo digestibility of DM and nutrients generally followed the order of T1 > T2 > T3 > T4. The dressing percentage of the carcass was 40.4% and all other parameters measured did not show significant variation due to treatment diets (P > 0.05). However, weight of liver, kidney and spleen was higher for sheep fed with higher tagasaste forage diet. The result of this study revealed that tagasaste can substitute wheat bran–noug seed cake concentrate mixture as a protein supplement. Options to increase the low ME and minimize the effect of the anti nutritional factors will improve nutrient digestibility in tagasaste forage and will enhance the overall efficiency of feed utilization.     

Resistance patterns and detection of aac(3)-IV gene in apramycin-resistant Escherichia coli isolated from farm animals and farm workers in northeastern of China

The aminoglycoside apramycin has been used widely in animal production in China since 1999. This study was aimed to investigate the resistance pattern of apramycin-resistant Escherichia coli isolated from farm animals and farm workers in northeastern of China during 2004–2007 and to determine whether resistance to apramycin was mediated by plasmid containing the aac(3)-IV gene and the mode for the transfer of genetic information between bacteria of farm animals and farm workers. Thirty six E. coli isolates of swine, chicken, and human origins, chosen randomly from 318 apramycin-resistant E. coli isolates of six farms in northeastern of China during 2004–2007, were multi-resistant and carried the aac(3)-IV gene encoding resistance to apramycin. Conjugation experiments demonstrated that in all 36 cases, the gene encoding resistance to apramycin was borne on a mobilisable plasmid. Homology analysis of the cloned aac(3)-IV gene with the sequence (accession no. X01385) in GenBank showed 99.3% identity at a nucleotide level, but only with a deletion of guanosine in position 813 of the gene in all 36 cases. The results indicted that resistance to apramycin in these isolates was closely related to aac(3)-IV gene. Therefore, the multi-resistance of E. coli could complicate therapeutic practices for enteric infections in both farm animals and human.     

饲料中维生素D3水平对黄鳝抗菌肽hepcidin基因表达的影响

本试验旨在探索饲料中维生素D3水平对黄鳝(Monopterus albus)抗菌肽hepcidin基因表达的影响.挑选体质健康、平均体重为(21.7±2.1)g的黄鳝360尾,随机分为6组,每组2个重复,每个重复30尾.6组黄鳝分别饲喂在基础饲料(0 IU/kg维生素D3)中添加0、250、500、1 000、2 000和4 000 IU/kg维生素D3的试验饲料.于投喂试验饲料后20、40和60 d,从各组随机选择6尾黄鳝,分别采集其肝胰脏、脾脏、头肾和后肠组织,采用荧光定量聚合酶链式反应(RT-PCR)技术检测样品中hepcidin基因表达量.结果表明:投喂20、40和60 d后,黄鳝4种组织中均有hepcidin基因表达,并且肝胰脏中显著高于脾脏、头肾和后肠中(P＜0.05);随维生素D3添加水平的增加,黄鳝hepcidin基因在4种组织的表达量同一时间点均呈现出先升高后降低的趋势;第20天时4种组织中的表达量均以2 000 IU/kg组为最高,显著高于其他各组(P＜0.05);第40和60天时肝胰脏、头肾中的表达量均以500 IU/kg组为最高,其中第40天时显著高于0、250、4 000 IU/kg组(P＜0.05),第60天时显著高于其他各组(P＜0.05).结果提示,短期(20 d)内在饲料中添加2 000 IU/kg的维生素D3可显著提高黄鳝内脏组织中hepcidin 基因的表达量;饲喂周期较长(40或60 d)时,饲料中添加500 IU/kg维生素D3可显著提高hepcidin基因在黄鳝肝胰脏和头肾中的表达量.     

Transmission of Cyprinid herpesvirus-3 (CyHV-3) from goldfish to naïve common carp by cohabitation

Cyprinid herpesvirus-3 (CyHV-3) has spread worldwide and has had a major impact on koi and common carp production. Previous studies on the host range of the CyHV-3 found that fish species other than koi and common carp are fully resistant to natural virus exposure. Recently, CyHV-3 was detected in goldfish (Carassius auratus auratus) that were in contact with CyHV-3 infected koi. In the present study, a specific RT-PCR product was amplified from the viral thymidine kinase gene in gills, intestine and brain tissues of CyHV-3 infected goldfish. This implied that CyHV-3 replicated in these goldfish. Also, in the presence of a stress factor such as temperature fluctuation, the CyHV-3 infected goldfish transmitted the virus to cohabitated naïve SPF common carp. CyHV-3 DNA was detected in the cohabitated naïve carp tissues by PCR. The results of this study demonstrate that goldfish is a carrier for CyHV-3, permit virus propagation, and disseminate the virus to susceptible carp causing the disease.     

MC3R基因对京海黄鸡屠体性状的遗传效应分析

本研究以MC3R基因为鸡屠体性状的候选基因,旨在探讨其对京海黄鸡屠体性状的影响。运用PCR-SSCP方法结合测序技术,检测了MC3R基因在京海黄鸡群体中的多态性,并采用一般线性模型(GLM)分析基因型与屠体性状的遗传效应。结果显示,MC3R基因CDS序列检测区内,引物MR2、MR3和MR8扩增的片段具有多态性,其中引物MR2和MR3扩增片段均存在2个SNP位点,分别形成AA、AB、AC 3种基因型和EE、EF、FF、EH 4种基因型,引物MR8扩增片段只存在1个SNP位点,形成了KK、KL和LL 3种基因型;检测到的5个SNPs位点分别为CDS区C160A、G192T、C273T、G310A、G762A突变。关联分析结果显示,MR2位点对京海黄鸡各屠体性状(除腹脂质量)均有极显著影响(P0.01);MR3位点各基因型(排除个体数少于3的基因型)屠体性状间差异均不显著(P0.05),推断MR3位点对京海黄鸡屠体性状影响不显著(P0.05);MR8位点对京海黄鸡屠体质量、胸肌质量、腿肌质量、全净膛质量、半净膛质量有极显著影响(P0.01),对活体质量和腹脂质量有显著影响(P0.05)。对MR2和MR8 2个位点的效应进行联合分析,结果显示,2个位点组合基因型对所有屠体性状均有显著或极显著影响(P0.05或P0.01),其中AB/KK基因型组合为有利基因型组合,AA/LL基因型组合为不利基因型组合。因此,本研究可为京海黄鸡分子标记辅助育种提供依据,有利于加快对京海黄鸡屠体性状选择的育种进程,同时通过本研究可推测MC3R基因对家禽的屠体性状具有很大的遗传效应,为家禽育种工作提供理论依据。     

Immunohistochemical study of matrix metalloproteinase‐3 (MMP‐3) at the articular cartilage in osteochondrotic pigs

In order to understand the mechanism of osteochondrosis in the pig, articular cartilage was taken from the distal femoral condyles of Duroc pigs exhibiting leg weakness and then examined immunohistochemically for the localization of matrix metalloproteinases‐3 (MMP‐3), one of the enzymes involved in the resolution of cartilage matrix. The articular cartilage had the typical characteristics of osteochondrotic lesions, such as abnormal calcification, clefts of cartilage, disappearance of proteoglycan, and necrotic chondrocytes. The immunoreaction of MMP‐3 was observed in chondrocytes at the boundary between normal cartilage and proteoglycan‐deficient area. Moreover, chondrocytes expressing MMP‐3 showed normal morphology, but the surrounding cartilage matrix did not stain with toluidine blue, which indicated a lack of glycosaminoglycans. These results suggest that MMP‐3 is highly involved in the appearance and expansion of osteochondrotic lesions.     

Effect of supplementation with MgCO3 and l-Tryptophan on the welfare and on the carcass and meat quality of two halothane pig genotypes (NN and nn)

Sixty-one animals with different Halothane genes (homozygous halothane positive, n = 34; and homozygous halothane negative, n = 27) were fed with three diets (control group, with no supplement; magnesium (Mg) group with 1.28 g MgCO₃/kg and tryptophan (Trp) group with 5 g l-Trp/kg) during the last 5 days before slaughter. Animals were submitted to minimal stress antemortem conditions. Pig behaviour was recorded at the experimental farm, raceway to the CO₂ stunning system and during the stunning period. Corneal reflexes were recorded after stunning as well. There were no differences in feed intake among diets (P > 0.05) during the 5 days of treatment. The halothane positive (nn) group had lower intake than the halothane negative (NN) group (P < 0.01). The behaviour of the pigs in the raceway did not differ (P > 0.05) among treatments or halothane genotype. A significant (P < 0.001) interaction diet  halothane was found in the time to appear the first retreat attempt during the exposure to the CO₂ system. In the nn group, the time of performing the first retreat attempt was later in the Mg (P < 0.05) than the control group. Moreover, in the Mg group, the nn had a later (P < 0.05) first retreat attempt than the NN. Thus, Mg supplementation could have a positive effect on welfare of nn pigs. The nn had a lower proportion of animals that showed corneal reflexes after stunning than NN, indicating a higher effectiveness of the stunning method in nn pigs. Neither Mg nor Trp affected carcass quality and meat quality parameters, although significant differences were found between genotypes.     

乙酸镁对氟烷基因杂合子育肥猪肌肉加工品质的影响

育肥猪屠宰前饲粮中短期添加乙酸镁,研究其对氟烷基因杂合子育肥猪肌肉加工品质的影响。选用体重相近的氟烷基因杂合子(HalNHaln)大长猪(大白猪×长白猪)36头随机分为2组,即对照组、乙酸镁组,每组18头。乙酸镁组在屠宰前5 d,基础日粮中添加镁1 500mg/kg(以乙酸镁形式),对照组饲喂基础日粮。试验表明:在猪屠宰前饲粮中短期添加1 500 mg/kg水平的镁对试验猪的平均日采食量没有明显影响(P>0.05);可以显著降低肌肉的滴水损失(P<0.05),提高猪肉的熟肉率,从而提高猪肉的加工品质。     

饲喂25羟基维生素D3和维生素D3对不同阶段荷斯坦种公牛冻精品质和营养物质表观消化率的影响

本试验对比研究25羟基维生素D3(25VD3)和维生素D3对青年和成年荷斯坦种公牛的冻精品质和抗氧化能力及钙、磷、镁代谢和营养物质表观消化率的影响.本试验采用2×2双因素试验设计(不同形式维生素D3和不同阶段种公牛),不同形式维生素D3分别为25VD3和维生素D3,不同阶段种公牛分别为16头平均30月龄成年荷斯坦种公牛...     

Life-history parameters of Culicoides (Avaritia) imicola Kieffer in the laboratory at different rearing temperatures

This laboratory study investigates the sub-adult developmental cycle of field collected Culicoides (Avaritia) imicola Kieffer (Diptera; Ceratopogonidae). The period required from blood-feeding field-collected females to the production of progeny adults occupied 34–56 days at 20 °C, 15–21 days at 25 °C and 11–16 days at 28 °C, demonstrating clear temperature dependence. When reared at 28 °C, C. imicola demonstrated higher variability in fecundity (between 2.4 and 20.6 eggs/female) and lower hatching rates (50.0–62.2%), although larval survival rates to pupation were low at all temperatures (20–30%). Similarly, the mean emergence rate from pupae was the highest at lower temperatures. These results highlight the difficulty in establishing and maintaining a laboratory colony of this species from field-collected material and results are discussed in reference to future research directions that may aid this process.     

Properties of the feline tumour suppressor reduced expression in immortalized cells (REIC/Dkk‐3)

Reduced expression in immortalized cells (REIC/Dkk‐3), a member of the human Dickkopf (Dkk) family, is a growth suppressor in human and canine mammary tumours. Mammary gland tumours are common neoplasms with high malignancy in female cats. The purpose of this study was to clone the feline REIC/Dkk‐3 homolog, investigate its expression in cell lines established from feline mammary gland tumours, and test its tumour suppressor function. Western blot analysis revealed that expression of the REIC/Dkk‐3 protein was reduced in feline mammary carcinoma cell lines. Forced expression of REIC/Dkk‐3 induced apoptosis in feline mammary tumour cell lines. These results demonstrate that REIC/Dkk‐3 expression, which is downregulated in feline mammary tumour cell lines, results in the induction of apoptosis in these cells. Our findings suggest that feline REIC/Dkk‐3 represents a potential molecular target for the development of therapies against feline mammary cancers.     

Effect of breed on fatty acid composition and stearoyl-CoA desaturase protein expression in the Semimembranosus muscle and subcutaneous adipose tissue of cattle

The present study investigated (i) the effect of breed on the expression of stearoyl-CoA desaturase (SCD) protein and fatty acid composition in Semimembranosus muscle and subcutaneous adipose tissue of beef cattle and (ii) the relationship between SCD expression, cis-9, trans-11 conjugated linoleic acid (CLA) content, and monounsaturated fatty acid (MUFA) level. The study was conducted on the following breeds: Longhorn (L), Charolais cross with Holstein–Friesian (CX), Hereford (H), Belted Galloway (BG) and Beef Shorthorn (BS). Significant breed differences in the total fatty acid content, saturated fatty acid (SFA) level, MUFA and n−3 PUFA content were observed in subcutaneous adipose tissue but not in muscle. In the case of CLA, the breed differences were observed in both muscle and subcutaneous adipose tissue, with the highest level in L and the lowest level in H. In the case of subcutaneous adipose tissue, the breed with the highest CLA content (L) also had the highest SCD protein expression. The breed-specific pattern of SCD expression in subcutaneous adipose tissue was similar to the breed-specific pattern of one of the products of an SCD-catalysed reaction, C16:1 (BS < BG < H < CX < L). It has been concluded that (i) the mechanisms regulating SCD protein expression and CLA level in beef cattle are tissue-specific; (ii) breed-specific variations in SCD expression might contribute to breed variations in MUFA and CLA content in subcutaneous adipose tissue but not in Semimembranosus muscle.