Comparing mRNA levels of genes encoding leptin,leptin receptor,and lipoprotein lipase between dairy and beef cattle

Body weight and fat mass vary distinctly between German Holstein (dairy cattle) and Charolais (beef cattle). The aim of this study was to determine whether the expression of the obese (Ob) gene and lipoprotein lipase (LPL) gene in fat tissues and expression of the long isoform leptin receptor (Ob-Rb) gene in the hypothalamus were different between these two cattle breeds. Body weight and the area of longissimus muscle cross-section of German Holstein were lower (P<0.001), while body fat content, as well as the omental and perirenal fat mass were higher (P<0.001), compared to Charolais. Plasma insulin and leptin levels between two cattle breeds were determined by radioimmunoassay. Compared to Charolais, plasma insulin concentrations were significantly higher (P<0.01), and plasma leptin levels were tended to be higher (P<0.1) in German Holstein. Ob mRNA levels in subcutaneous and perirenal fat depots, but not in the omental fat depot, were significantly higher (P<0.05) in German Holstein than in Charolais. LPL mRNA expression in the perirenal fat depot of German Holstein was greater in abundance than that of Charolais. No significantly different LPL mRNA levels were found in subcutaneous and omental fat depots, and Ob-Rb mRNA levels in the hypothalamus between these two cattle breeds (P<0.05). Both Ob and LPL expression was greater in perirenal and omental fat depots than in the subcutaneous fat depot (P<0.05). Data indicated that in bovine the Ob and LPL gene expression levels in perirenal fats are an important index that is associated with body fat content, while Ob-Rb in hypothalamus is not.     

Adipose tissue growth and cellularity: changes in bovine adipocyte size and number

Forty crossbred steers of similar birth date and fed the same growing-finishing diet were used to study adipocyte changes in six fat depots during growth from 11 to 19 mo of age. Steers were slaughtered at 2-mo intervals. Adipose tissue samples were obtained from kidney, mesenteric and brisket fat and subcutaneous, intermuscular and intramuscular fat from the 10th to 12th rib section. The osmium tetroxide fixation technique was used for determination of cell size and number. Except for three brisket fat samples, distributions of adipocyte diameters from six different fat depots were monophasic during the age range considered in this study. At 17 mo of age, the mean adipocyte diameter, in decreasing order, was: kidney fat greater than mesenteric greater than subcutaneous greater than intermuscular greater than intramuscular greater than brisket fat. Fat deposition during growth to 19 mo of age occurred mainly by hypertrophy of adipocytes. An apparent cell hyperplasia occurred in the intramuscular fat depot from 11 to 15 mo and in the brisket fat depot after 15 mo of age. Based on cellularity characteristics, evidence exists to classify intramuscular and brisket fat depots as late-developing ones. Cell number/gram of intramuscular adipose tissue was a better predictor of marbling score than was fat cell diameter.     

Relationship between adipose maturity and fatty acid composition in various adipose tissues of Japanese Black,Holstein and Crossbred (F1) steers

The amount of monounsaturated fatty acid (MUFA) is intimately related to adipose softness, melting point (MP) and flavor in beef. Stearoyl‐CoA desaturase (SCD) is a main gene involved in MUFA synthesis. Mature adipose tends to be highly saturated, whereas immature or maturing adipose is highly unsaturated when chronologically based, so the degree of non‐saturation can be an index of adipose maturity. In this study, three different adipose tissues (coelomic (CL), perirenal (PR), and subcutaneous (SC)) from three beef breeds with differing slaughter ages (Japanese Black (29.5 months), Holstein (20.1 month), and F1 crossbreed (25.6 months)) were examined to: (i) determine adipose maturity level as indexed by MUFA %; and (ii) determine SCD and other lipogenic gene messenger RNA (mRNA) expression levels in relation to unsaturated fatty acid content. Fatty acid composition was significantly different between adipose tissues (P < 0.05). MUFA amount was high in the following order: SC > CL > PR. This pattern corresponded to SCD mRNA expression profile showing higher expression in SC than CL and PR. However, Japanese black cattle are an exception with CL adipose containing similar UFA % as SC adipose, yet having the lowest SCD mRNA expression level among all adipose tissues tested. Therefore, SCD mRNA expression and MUFA % appear to be directly related; however, differences in SCD mRNA expression among three adipose tissues may reflect differences in the fat development characteristics affected by chronological age of the cattle breeds.     

Effect of polymorphisms linked to LEP gene on its expression on adipose tissues in beef cattle

In cattle, genetic markers at the leptin (LEP) gene and at those linked to the gene have been described as affecting calving interval (markers LEPSau3AI and IDVGA51), or daily weight gain (BMS1074 and BM1500). This work investigated the effect of these alleles on LEP mRNA levels in cattle subcutaneous and omental adipose tissues. A sample of 137 females of a Brangus‐Ibage beef cattle herd was analysed to evaluate the distribution of the polymorphisms; then, animals having at least one of the IDVGA51*181 (allele 181 at marker IDVGA51; six animals), LEPSau3AI*2 (four), BMS1074*151 (13), BM1500*135 (six) alleles and a control group composed of animals without any of these alleles (four animals) were submitted to surgery to obtain omental and subcutaneous adipose tissues. Leptin mRNA expression was quantified by TaqMan RT‐PCR, using 18S rRNA as internal control and adjusted for the effect of body condition score, through regression analysis. Omental fat had LEP gene expression 33% lower than the subcutaneous tissue. Carriers of IDVGA*181 and BMS1074*151 showed subcutaneous fat leptin mRNA levels higher than the controls. Leptin controls feed intake and coordinates reproduction; therefore, animals with higher LEP gene expression will probably have lower daily weight gain than others with similar forage offer and nutritional condition and probably will also have longer calving interval.     

Adipogenic differentiation state-specific gene expression as related to bovine carcass adiposity

Genetic regulation of the site of fat deposition is not well defined. The objective of this study was to investigate adipogenic differentiation state-specific gene expression in feedlot cattle (>75% Angus; <25% Simmental parentage) of varying adipose accretion patterns. Four groups of 4 steers were selected via ultrasound for the following adipose tissue characteristics: low subcutaneous-low intramuscular (LSQ-LIM), low subcutaneous-high intramuscular (LSQ-HIM), high subcutaneous-low intramuscular (HSQ-LIM), and high subcutaneous-high intramuscular (HSQ-HIM). Adipose tissue from the subcutaneous (SQ) and intramuscular (IM) depots was collected at slaughter. The relative expression of adipogenic genes was evaluated using quantitative PCR. Data were analyzed using the mixed model of SAS, and gene expression data were analyzed using covariate analysis with ribosomal protein L19 as the covariate. No interactions (P > 0.10) were observed between IM and SQ adipose tissue depots for any of the variables measured. Therefore, only the main effects of high and low accretion within a depot and the effects of depot are reported. Steers with LIM had smaller mean diameter IM adipocytes (P < 0.001) than HIM steers. Steers with HSQ had larger mean diameter SQ adipocytes (P < 0.001) than LSQ. However, there were no differences (P > 0.10) in any of the genes measured due to high or low adipose accretion. Preadipogenic delta-like kinase1 mRNA was greater in the IM than the SQ adipose tissue; conversely, differentiating and adipogenic genes, lipoprotein lipase, PPARγ, fatty acid synthetase, and fatty acid binding protein 4 were greater (P < 0.001) in the SQ than the IM depot. Intramuscular adipocytes were smaller than SQ adipocytes and had greater expression of the preadipogenic gene, indicating that more hyperplasia was occurring. Meanwhile, SQ adipose tissue contained much larger (P < 0.001) adipocytes that had a greater expression (P < 0.001) of differentiating and adipogenic genes than did the IM adipose tissue, indicating more cells were undergoing differentiation and hypertrophy. Adipogenic differentiation state-specific gene expression was not different in cattle with various phenotypes, but adipogenesis in the SQ and IM adipose tissues seems to occur independently.     

不同日龄阿勒泰大尾羊脂肪组织形态学及血脂指标的比较

为了研究阿勒泰大尾羊不同部位脂肪组织沉积的变化规律,本试验选取90和270日龄健康、雄性阿勒泰大尾羊各6只,分别采集了90和270日龄时肾周脂、尾脂、腹部皮下脂肪组织样和血清,采用冰冻脂肪组织切片油红O滴染技术和Motic显微数字图像处理系统,测定脂肪细胞面积,并采用放射性免疫技术和酶联免疫法测定了血脂指标.结果显示,90日龄时,阿勒泰大尾羊尾脂脂肪细胞面积极显著高于肾周脂脂肪细胞面积(P<0.01),270日龄时,尾脂和腹部皮下脂肪脂肪细胞面积均极显著高于肾周脂脂肪细胞面积(P<0.01),但脂肪细胞的面积在尾脂和皮下脂肪之间无显著差异(P>0.05);与90日龄相比,270日龄阿勒泰大尾羊肾周脂脂肪细胞面积显著增高(P<0.05),而尾脂脂肪细胞面积极显著降低(P<0.01);90日龄阿勒泰大尾羊血清中leptin和HSL含量极显著高于270日龄(P<0.01),而血清中AST和ALT含量极显著低于270日龄(P<0.01).结果表明,阿勒泰大尾羊从90日龄生长至270日龄时,肾周脂脂肪细胞面积呈增加的趋势,而尾脂脂肪细胞的面积呈减少的趋势,这种变化可能与血清瘦素、激素敏感脂肪酶、天门冬氨酸氨基转氨酶和丙氨酸氨基转移酶含量有关.     

Lipogenic enzyme activities in different adipose depots of Pirenaican and Holstein bulls and heifers taking into account adipocyte size

The effects of sex, genotype, and adipose depot on lipogenic enzyme activity have been investigated in Holstein and Pirenaican bulls and heifers, taking into account differences in adipocyte size. Fifteen Pirenaican bulls and 15 heifers and 15 Holstein bulls and 13 heifers were fattened until slaughter (12 to 13 mo old and 450 to 500 kg of body weight). During the fattening period, animals had ad libitum access to commercial concentrates and straw. The 10th rib was dissected to determine the fat content. Adipocyte size and activities of the following lipogenic enzymes were determined: glycerol 3-phosphate dehydrogenase, fatty acid synthase, nicotinamide adenine dinucleotide phosphate (NADP)-malate dehydrogenase, glucose 6-phosphate dehydrogenase, and NADP-isocitrate dehydrogenase, in the omental, perirenal, subcutaneous, and intermuscular adipose depots, respectively. Because adipocyte mean cell volume varied with sex, breed, and depot, regression analyses of log(e) activity per cell and log(e) cell volume were used to compare activities per unit volume. Sex, breed and depot had no effect (P > 0.05) on the gradients of regressions, which did not differ significantly from 1. Thus, activity per unit volume did not vary with cell size. Consequently, sex, breed, and depot effects on the regression analyses were equivalent to effects on activity per unit volume. Females had greater amounts of fat in the 10th rib (P < 0.001), larger adipocytes (P < 0.001) and, in general, greater (P < 0.05) lipogenic activity per cell, even when adjusted for cell size, than males. These findings suggest that differences in adiposity between sexes are mainly due to females having a greater capacity for lipid synthesis, and hence, hypertrophy, than males. When adjusted for differences in carcass weight, Holsteins had larger adipocytes than Pirenaicans. The abdominal depots, omental and perirenal, had a greater adipocyte size (P < 0.001) and, in general, greater lipogenic enzyme activities per cell (P < 0.05) than the subcutaneous and intermuscular carcass depots. However, when activity per cell was adjusted for cell size, subcutaneous depots had greater fatty acid synthae, glucose 6-phosphate dehydrogenase, and NADP-malate dehydrogenase activities than omental and perirenal, indicating that other factors such as nutrient supply may restrict hypertrophy of carcass adipocytes.     

Effect of source and amount of energy and rate of growth in the growing phase on adipocyte cellularity and lipogenic enzyme activity in the intramuscular and subcutaneous fat depots of Holstein steers

Seventy-three Holstein steers (initial BW 138.5 +/- 4.3 kg; approximately 3 mo of age) were allotted by BW to one of three growing-phase treatments to determine the effect of source and amount of energy on feedlot performance, and characteristics of subcutaneous (s.c.) and intramuscular (i.m.) adipose tissue. Treatment diets were 1) high concentrate fed ad libitum (ALC); 2) high forage fed ad libitum for 55 d, then a mid-level forage diet fed ad libitum for 98 d (ALF); or 3) limit-fed high concentrate to achieve a gain of 0.8 kg/d for 55 d, then to achieve a gain of 1.2 kg/d for 98 d (LFC). All steers were fed the ALC diet from d 154 to slaughter. Eight steers per treatment were selected after an average of 145 and 334 d on feed for determination of adipocyte cellularity and lipogenic enzyme activity at the end of the growing and finishing phases, respectively. Remaining steers were slaughtered after an average of 334 d on feed. At initial slaughter, ALC steers had a two- to threefold greater (P < 0.05) s.c. fat depth, and 1.9-fold greater (P < 0.01) longissimus muscle ether extract than steers in other groups. At final slaughter, LFC steers had a greater fat depth than ALF steers (P < 0.10) and had the greatest (P < 0.10) longissimus muscle ether extract. Increased fat depth for ALC steers at initial slaughter was a result of a greater (P < 0.05) mean adipocyte diameter in the s.c. depot. Mean i.m. adipocyte diameter followed the same trend (P < 0.16). The number of adipocytes per gram of s.c. fat was least for ALC and greatest for ALF (P < 0.10) at initial slaughter. Mean diameter and number of adipocytes per gram of i.m. and s.c. fat did not differ among treatments at final slaughter (after 180 d on a common finishing diet). High energy (ALC) increased activities of ATP-citrate lyase, fatty acid synthase, 6-phosphogluconate dehydrogenase, glucose-6-phosphate dehydrogenase, and malate dehydrogenase (P < 0.05), in the s.c. depot, and increased activities of ATP-citrate lyase and glucose-6-phosphate dehydrogenase (P < 0.10) in the i.m. depot at initial slaughter. Lipogenic enzyme activity in the s.c. depot at final slaughter did not differ among treatments. Glucose-6-phosphate dehydrogenase activity in the i.m. depot at final slaughter was lowest (P < 0.10) in ALF. Hypertrophy made a greater contribution to fat tissue growth than hyperplasia. Hypertrophy was affected by amount of energy, whereas hyperplasia was affected by source of energy. Differences diminished when cattle were fed the common finishing diet.     

Effects of short-term infusion with propionate on the mRNA expression of a putative G-protein coupled receptor 41 (GPR41) in adipose tissue of goats

Short chain fatty acids (SCFA) represent the main source for energy supply in ruminants. Propionate up-regulates leptin synthesis through the G protein-coupled receptor 41 (GPR41) in mice but the importance of the GPR41 in ruminants is not yet clarified. Here we characterise the short-term effects of intravenously infused propionate on a putative GPR41 mRNA in goat adipose tissue. Castrated male goats (Capra hircus) received propionate infusion or NaCl solution with equivalent sodium content for 260 min. A putative GPR41 mRNA was quantified in subcutaneous and perirenal adipose tissue by real-time RT-PCR. The mRNA concentration of the putative GPR41 mRNA increased (p = 0.029) in subcutaneous but not in perirenal adipose tissue (p = 0.756) of propionate-infused animals versus the NaCl group. We hypothesise that the differential response of the putative GPR41 mRNA in subcutaneous versus perirenal adipose tissue towards short-term propionate infusion could be involved in a differential nutrient sensing of SCFA in the two adipose depots of goats.     

The ontogeny of leptin mRNA expression in growing broilers and its relationship to metabolic body weight.

The polypeptide hormone leptin is produced by both adipose tissue and the liver and has been shown to induce satiety in chickens. In this study we have investigated the developmental regulation of leptin mRNA expression in growing broiler chickens. Leptin expression generally increases in all tissues from 1-12 weeks of age. In the subcutaneous fat depot there is an apparent pattern of increased leptin mRNA expression occurring at 2, 6, and 10 weeks post-hatch. This pattern was not evident in the other tissues surveyed and may relate to the cycle of loading and unloading of adipocytes with lipid. No consistent gender differences in leptin expression patterns were detected in the tissues surveyed, as is often observed in mammals. Positive correlations between metabolic body weight and adipose leptin expression levels were observed. Leptin expression by the liver was highly correlated with metabolic body weight from 1-6 weeks of age, and uncorrelated from 6-12 weeks of age. This pattern of increasing liver leptin expression with increasing body weight during the early rapid growth phase of the bird may be due to limited fat storage during this period, which is followed by rapid body fat accumulation from 6-12 weeks. The characterization and tissue specific distribution of leptin mRNA expression in the growing broiler indicate similar patterns of leptin production to that of growing mammals. Leptin may be involved in lipid flux through the adipocyte as well as the shift in lipid metabolism to increased storage during pre-puberty.     

Maternal obesity upregulates fatty acid and glucose transporters and increases expression of enzymes mediating fatty acid biosynthesis in fetal adipose tissue depots

Maternal nutrient restriction leads to alteration in fetal adipose tissue, and offspring from obese mothers have an increased risk of developing obesity. We hypothesized that maternal obesity increases fetal adipogenesis. Multiparous ewes (Columbia/Rambouillet cross 3 to 5 yr of age) carrying twins were assigned to a diet of 100% (Control; CON; n = 4) or 150% (Obese; OB, n = 7) of NRC maintenance requirements from 60 d before conception until necropsy on d 135 of gestation. Maternal and fetal plasma were collected and stored at -80°C for glucose and hormone analyses. Fetal measurements were made at necropsy, and perirenal, pericardial, and subcutaneous adipose tissues were collected from 7 male twin fetuses per group and snap frozen at -80°C. Protein and mRNA expression of fatty acid translocase [cluster of differentiation (CD) 36], fatty acid transport proteins (FATP) 1 and 4, insulin-sensitive glucose transporter (GLUT-4), fatty acid synthase (FASN), and acetyl-coA carboxylase (ACC) was evaluated. Fetal weight was similar, but fetal carcass weight (FCW) was reduced (P < 0.05) in OB versus CON fetuses. Pericardial and perirenal adipose tissue weights were increased (P < 0.05) as a percentage of FCW in OB versus CON fetuses, as was subcutaneous fat thickness (P < 0.001). Average adipocyte diameter was greater (P < 0.01) in the perirenal fat and the pericardial fat (P = 0.06) in OB fetuses compared with CON fetuses. Maternal plasma showed no difference (P > 0.05) in glucose or other hormones, fetal plasma glucose was similar (P = 0.42), and cortisol, IGF-1, and thyroxine were reduced (P ≤ 0.05) in OB fetuses compared with CON fetuses. Protein and mRNA expression of CD 36, FATP 1 and 4, and GLUT-4 were increased (P ≤ 0.05) in all fetal adipose depots in OB versus CON fetuses. The mRNA expression of FASN and ACC was increased (P < 0.05) in OB vs. CON fetuses in all 3 fetal adipose tissue depots. Fatty acid concentrations were increased (P = 0.01) in the perirenal depot of OB versus CON fetuses, and specific fatty acid concentrations were altered (P < 0.05) in subcutaneous and pericardial adipose tissue because of maternal obesity. In conclusion, maternal obesity was associated with increased fetal adiposity, increased fatty acid and glucose transporters, and increased expression of enzymes mediating fatty acid biosynthesis in adipose depots. These alterations, if maintained into the postnatal period, could predispose the offspring to later obesity and metabolic disease.     

Subcutaneous and intramuscular adipose tissue stearoyl-coenzyme A desaturase gene expression and fatty acid composition in calf- and yearling-fed Angus steers

We proposed that stearoyl-CoA desaturase (SCD) activity dictates fatty acid composition of adipose tissue and muscle in beef cattle, regardless of ruminal or hepatic fatty acid hydrogenation or desaturation. Twelve Angus steers were assigned to a calf-fed (CF) group and slaughtered at weaning (8 mo of age; n=4), 12 mo of age (n=4), or 16 mo of age (n=4). Twelve steers were assigned to a yearling-fed (YF) group and slaughtered at 12 mo of age (n=4), 16 mo of age (n=4), and 17.5 mo of age (n=4; 525 kg, market weight). Data were analyzed based on time on the corn-based finishing diet, with terminal age as a covariate, and orthogonal polynomial contrasts were tested on the main effects of treatment group and time on the finishing diet. Fatty acids from duodenal digesta, plasma, liver, LM, and subcutaneous and intramuscular adipose tissue were measured, and SCD gene expression was measured in intramuscular and subcutaneous adipose tissues. In duodenal digesta, palmitic and linoleic acids increased by 100% over the sampling period, α-linolenic acid decreased over the sampling period, and trans-vaccenic acid was greater in YF than in CF steers (all P < 0.01). The proportion of α-linolenic acid decreased over time in all tissues, including liver. The SCD index (ratio of SCD fatty acid products to SCD fatty acid substrates) increased over time in LM and in intramuscular and subcutaneous adipose tissues. The SCD:glyceraldehyde 3-phosphate dehydrogenase mRNA ratio was virtually undetectable at the initial sampling periods in subcutaneous adipose tissue of YF and CF steers, and it increased over time (P < 0.01). The SCD index and SCD:glyceraldehyde 3-phosphate dehydrogenase ratio were greater in intramuscular adipose tissue of CF steers than in that of YF steers. The SCD index did not change over time in liver and decreased over time in duodenal digesta. We conclude that, unlike essential fatty acids, the SFA and MUFA composition of adipose tissue is regulated by adipose tissue fatty acid desaturation, with little contribution from hepatic or duodenal fatty acids.     

Correlations between carcass traits and mRNA levels of CGI-105 and CCAAT/enhancer protein α genes in steers of Korean cattle

To understand the molecular mechanisms that regulate intramuscular fat deposition (marbling), cDNA clones expressed in adipose tissues of Korean cattle were identified and characterized. One clone had a total length of 1262 nucleotides coding for 314 amino acids. It was identified as one encoding bovine homolog of human CGI-105 mRNA. CGI-105 is a member of fumarylacetoacetate hydrolase family. Comparison of the deduced amino acid sequences of bovine CGI-105 with those of human revealed more than 89% identity. High levels of CGI-105 mRNA expression were detected in muscle, heart, and kidney tissues among various bovine tissues. Carcass traits, including backfat thickness, rib eye area, yield index, marbling score, and quality grade were analyzed in steer of Korean cattle. A CCAAT/enhancer binding protein alpha (C/EBPα) is one of adipocyte differentiation factors that may affect deposition of fat in muscle. mRNA levels of CGI-105 and C/EBPα genes were determined in the loin muscle tissues of steers. Correlation between carcass traits and mRNA levels of the genes was estimated by Pearson's correlation coefficient. The mRNA levels of C/EBPα showed strong positive correlation (r = 0.83, p < 0.01) with marbling scores. The results of the present study indicate that the manipulation of the expression of the C/EBPα gene may contribute to the development of a method for enhancing intramuscular fat deposition in beef.     

Fat depot‐specific effects of body fat distribution and adipocyte size on intramuscular fat accumulation in Wagyu cattle

Ectopic fats have been recognized as a new risk factor for metabolic syndrome. In obese humans, ectopic fat accumulations are affected by body fat distribution. Intramuscular adipose tissue is categorized as one of the ectopic fats. Japanese black cattle (Wagyu) are characterized by the ability to accumulate high amounts of intramuscular adipose tissue. In Japan, the marbling level is indicated by the beef marbling standard number (BMS No.), which reflects the intramuscular fat content of longissimus muscle. We hypothesized that the intramuscular fat accumulation is affected by the body fat distribution in Wagyu cattle. In this study, we showed that the BMS No. was not correlated with the subcutaneous and visceral adipocyte diameter. In contrast, the BMS No. was positively correlated with intramuscular adipocyte diameter. These results indicate that the intramuscular adipocyte diameter of Wagyu is hypertrophied with an increase in the intramuscular fat accumulation. In addition, we showed that the BMS No. was positively correlated with the subcutaneous fat percentage. In contrast, the BMS No. was negatively correlated with the visceral fat percentage. These results indicate that highly marbled Wagyu cattle have a higher percentage of subcutaneous fat and a lower percentage of visceral fat.     

Relationship between leptin content, metabolic hormones and fat deposition in three beef cattle breeds

The aim of the study was to determine if cattle breeds differing in their carcass characteristics also differ in the profiles of their leptin and metabolic hormones. Three breeds, Belgian Blue (BB) (n = 12), Limousin (L) (n = 12) and Aberdeen Angus (AA) (n = 12) with varying ability to deposit fat and protein were compared. Blood, muscle and subcutaneous (SC) adipose tissue were sampled. Animal performance, carcass and meat characteristics were determined as well as plasma leptin concentration, leptin gene expression in SC adipose tissue, leptin-receptor gene expression in SC adipose tissue and plasma concentration of insulin, tri-iodothyronin (T3), thyroxin (T4) and cortisol. The BB bulls showed the lowest values of leptin gene expression (P < 0.05). Values of plasma leptin concentration and of leptin-receptor gene expression tended to be lower in BB than in the other breeds. For a similar amount of adipose tissue (after normalisation), BB bulls showed a higher ratio of plasma leptin (P < 0.05), whereas normalised leptin gene and leptin-receptor gene expressions did not significantly differ between breeds. Belgian Blue bulls also differed in their metabolic hormone profile, tending to show lower values of insulin, T3 and T4 than the two other breeds. Cortisol levels were significantly lower (P < 0.05) in BB than in L and AA animals.     

Circulating ghrelin and leptin concentrations and growth hormone secretagogue receptor abundance in liver, muscle, and adipose tissue of beef cattle exhibiting differences in composition of gain

Data from species other than cattle indicate that ghrelin and GH secretagogue receptor (GHS-R) could play a key role in fat deposition, energy homeostasis, or glucose metabolism by directly affecting liver and adipose tissue metabolism. Beef steers (n = 72) were used to test the hypothesis that plasma ghrelin and leptin concentrations and abundance of the GHS-R in liver, muscle, and adipose tissues differ in steers exhibiting differences in composition of gain. At trial initiation (d 0), 8 steers were slaughtered for initial carcass composition. The remaining 64 steers were stratified by BW, allotted to pen, and treatment was assigned randomly to pen. Steers were not implanted with anabolic steroids. Treatments were 1) a low-energy (LE) diet fed during the growing period (0 to 111 d) followed by a high-energy (HE) diet during the finishing period (112 to 209 d; LE-HE) or 2) the HE diet for the duration of the trial (1 to 209 d; HE-HE). Eight steers per treatment were slaughtered on d 88, 111, 160, and 209. Carcass ninth, tenth, and eleventh rib sections were dissected for chemical composition and regression equations were developed to predict compositional gain. Liver, muscle, and subcutaneous adipose tissues were frozen in liquid nitrogen for subsequent Western blotting for GHS-R. Replicate blood samples collected before each slaughter were assayed for ghrelin and leptin concentrations. When compared at a common compositional fat end-point, the rate of carcass fat accretion (g·kg of shrunk BW(-1)) was greater (P < 0.001) in HE-HE steers whereas the rate of carcass protein accretion (g·kg of shrunk BW(-1)) was less (P < 0.001) compared with LE-HE steers. When compared at a common compositional fat end-point, plasma leptin, ghrelin, and insulin concentrations were greater (P < 0.05) for HE-HE compared with LE-HE steers. Abundance of the GHS-R, to which ghrelin binds, increased over time in liver and adipose tissue but did not differ as a result of treatment. Plasma ghrelin concentrations were increased for cattle continuously fed the HE diet as they became increasingly fatter; however, abundance of the GHS-R in liver, muscle, and subcutaneous adipose tissue was not different between treatment groups. The role of ghrelin in cattle metabolism warrants further investigation as it could have a significant effect on composition of BW gain, feed efficiency, and metabolic disorders such as ketosis and fatty liver.     

Effects of acute fasting and age on leptin and peroxisome proliferator‐activated receptor gamma production relative to fat depot in immature and mature pigs

Leptin and peroxisome proliferator‐activated receptor gamma (PPARγ) are adipogenic proteins that are actively involved in metabolic homeostasis of fat. Recently, it was reported that fat tissue in humans and rodents differs in metabolic activity relative to anatomical location of the fat tissue (i.e. depots) and animal age. Hence, we hypothesized that leptin and PPARγ production in various fat depots in female pigs differs in response to acute fasting, and that these responses vary with physiological maturity of the animal. Sixteen intact crossbred immature female pigs [prepubertal (PP); 132.2 ± 4.1 days] and 16 sexually mature female pigs (M; 224 ± 7.4 days) housed in an open‐air, concrete slab, sheltered barn were randomly assigned to either Control or Fasted treatments. Control pigs (PP, n = 8; M, n = 8) had ad libitum access to feed, while Fasted pigs (PP, n = 8; M, n = 8) were denied access to feed from the onset of the study (0 h) to euthanasia at 72 h. Immediately post‐mortem, fat samples were collected from the subcutaneous, pelvic, kidney, and heart (M pigs only) fat depots and analysed for leptin and PPARγ mRNA and protein content. Acute fasting decreased mean leptin mRNA tissue content in a depot specific manner in M pigs (p < 0.01), while mean leptin protein concentrations in fat tissues did not differ with fat depot or age of the pig. Furthermore, acute fasting did not affect mean PPARγ mRNA tissue content in a fat depot or age dependent manner. Mean concentrations of PPARγ protein in fat depots tended to be greater in M vs. PP pigs (p = 0.07). We suggest that these data provide evidence that acute fasting has a greater effect on leptin than PPARγ production in a fat depot dependent manner in M pigs, which may be indicative of changing physiological demands as an animal matures.     

Effects of vitamin A on growth performance and carcass quality in steers

Vitamin A plays a critical role in many essential life processes. In herbivores, it is either derived from plant β-carotene or directly as a dietary supplement. In cattle, vitamin A has the potential to influence various carcass traits that are sought by specific beef markets. A group of 20 Angus steers was removed from pasture and fed a low β-carotene and vitamin A cereal-based ration on a feedlot for 308 days. Ten of the steers were supplemented with vitamin A (retinyl palmitate, 60 IU of vitamin A/100 kg body weight/day) and the other ten received no supplement. The results demonstrated that restriction of vitamin A intake changed intramuscular fat deposition without changing subcutaneous fat depots. Angus steers that had been depleted of vitamin A showed increased intramuscular fat in the longissimus thoracis et lumborum (LTL) by 35% (P < 0.026) and seam fat area at the quartering site by 33% (P < 0.0273), when compared with cattle supplemented with vitamin A. There were no changes in intramuscular fat in the semitendinosus. Visually assessed marbling scores were also higher (19%; P < 0.094) in the non-supplemented, depleted group. There was no effect of vitamin A depletion on cattle growth and other meat traits (eye muscle area, meat colour, pH, meat cut weight), meat eating attributes (tenderness, cooking loss) or muscle fibre diameter. The only difference (P < 0.0177) among the meat traits was fat colour where depleted animals had whiter fat than the controls. Moreover, the fat from the vitamin A depleted group was softer with a lower melting point. We conclude that the reduced vitamin A consumption, leading to vitamin A depletion, increases intramuscular fat. On the other hand, the vitamin A depletion did not increase subcutaneous fat depth or change other meat quality traits, suggesting that marbling and these other traits are not invariably related.