Differences in pituitary cell number but not cell type between genetically lean and fat Coopworth sheep

Coopworth sheep selected for low backfat (lean genotype) have been shown to have heavier pituitary glands than those selected for high backfat (fat genotype). This paper investigated whether this difference was due to an increase in pituitary cell number or cell size and whether the relative proportions of different pituitary cell types differed between the genotypes. In three separate trials, ram lambs aged 6 to 8 months were slaughtered and the pituitary glands were processed for stereological or immunocytochemical studies. The pituitary glands of lean genotype sheep were between 30 and 60% heavier than those of the fat sheep. Lean sheep had a significantly (P<0.05) larger cross-sectional area of the pituitary fossa (96.6 vs. 81.7 mm(2)) than fat genotype sheep. The pituitaries from lean sheep contained significantly more total cells than fat sheep (Trial 1: 290 vs. 183 million cells, P<0.01; Trial 2: 353 vs. 239 million cells, P <0.05). The volume of individual cells did not differ between the genotypes. Trial 3 showed that there was no difference between lean and fat sheep in the percentage of cells staining positive for the five pituitary hormones studied. It is concluded that the larger pituitary glands of lean compared to fat genotype sheep are a result of a nonspecific increase in the size of the whole gland through increased cell numbers, with no change in cell size or the relative proportion of different cell types.     

Toll-like receptor genes are differentially expressed at the sites of infection during the progression of Johne's disease in outbred sheep

Toll-like receptors (TLR) are engaged by ligands on microbial pathogens to initiate innate and adaptive immune responses. Little is known about TLR involvement during infection with Mycobacterium avium subsp. paratuberculosis (M. ptb), the cause of Johne's disease in ruminants, although there is a profound immunopathological response in affected animals. We have analyzed the expression of 10 TLR genes relative to validated reference genes at predilection sites in ileum, jejunum and associated lymph nodes as well as in peripheral blood, to determine if TLR expression is altered in response to infection with M. ptb in outbred sheep. Previously unexposed animals from two flocks and animals from three naturally infected flocks were used with restricted maximum likelihood linear mixed modeling applied to determine significant differences. These were related to the pathologies observed at different stages of infection in exposed sheep, after allowing for other sources of variation. In most cases there were differences in TLR expression between early paucibacillary and multibacillary groups when compared to uninfected sheep, with most TLRs for the paucibacillary group having lower expression levels than the multibacillary group. Increased expression of TLR1-5, and 8 was observed in ileum or jejunum, and TLR1-4, 6, and 8 in mesenteric lymph nodes. There was a trend for increased expression of TLR1, 2, and 6-8 in PBMCs of exposed compared to non-exposed animals. Further study of TLR expression in Johne's disease in ruminants is warranted as these observed differences may help explain pathogenesis and may be useful in the future diagnosis of M. ptb infection.     

Comparative analysis of differentially expressed genes related to triglyceride metabolism between intramuscular fat and abdominal fat in broilers

ABSTRACT

1. Lipid metabolism is an indispensable process in an organism, though little is known about the regulatory mechanisms of fat deposition in different types of adipose tissues.

2. The differentially expressed genes related to triglyceride (TG) metabolism between abdominal and intramuscular fat (IMF) of Beijing-You chickens were investigated in this study.

3. TG content in abdominal fat (AF) (349.7 mg/g) was significantly higher (P < 0.01) than in the breast and thigh (12.3 mg/g and 24.8 mg/g, respectively).

4. Using Agilent chicken gene-expression profiling in adipose tissues between AF and muscle (breast and thigh), certain representative genes related to fatty acid metabolism, lipoprotein catabolism and esterification reactions were significantly upregulated (P < 0.05 or P < 0.01).

5. Genes involved in fatty acid oxidation or carbohydrate utilisation were significantly up- or downregulated (P < 0.05 or P < 0.01), including those involved with highly enriched pathways of lipid metabolism (PPAR, Wnt pathway and inositol phosphate metabolism), cell junctions (focal adhesion and regulation of actin cytoskeleton) and muscle contraction.

6. Overall, higher TG levels were observed in AF tissue than in adipose tissues of breast and thigh, which could be regulated through gene expression of pathways related to lipid metabolism (PPAR, Wnt pathway and inositol phosphate metabolism), cell junctions (focal adhesion and regulation of actin cytoskeleton) and muscle contraction. These results provide clues to understanding the molecular mechanisms of TG metabolism between abdominal and IMF.     

Effect of exogenous corticosterone in genetically fat and lean chickens

1. The effects of daily injections of corticosterone (1 or 5 mg/bird) on growth, fat deposition, liver lipid and plasma concentrations of uric acid, glucose, insulin and growth hormone were studied using genetically selected lines of fat (FL) and lean (LL) chickens. 2. Both doses of corticosterone depressed body weight gain and increased the liver lipid and the abdominal fat to the same extent in both lines. 3. In both lines, corticosterone caused a dose-dependent increase in the plasma concentrations of uric acid, glucose and insulin in the fasted and refed states. 4. In untreated birds, plasma concentrations of growth hormone (GH) were slightly higher in FL than in LL chickens and slightly decreased during refeeding. The response was not modified by injection of 1 mg corticosterone. Injections of 5 mg decreased plasma GH in both lines in the fasting state and in LL chickens during refeeding. In contrast, the same dose increased GH in FL chickens during refeeding. This contradiction remains unexplained. 5. The results suggest that corticosterone sensitivity is not involved in difference of fattening between FL and LL chickens.     

Further investigations on protein requirement of genetically lean and fat chickens

1. Genetically lean (LL) or fat (FL) chickens were fed from 28 to 42 d of age on one of 6 diets with different protein contents (from 73 to 208 g/kg). In order to keep a constant amino acid balance the experimental diets were made by diluting a well-balanced protein-rich diet with a protein-free diet. 2. Dietary protein influenced the growth rate of both genotypes similarly. However, maximum weight gain was reached in LL at a lower protein intake than in FL. 3. Regression between total protein gain (body protein + feather protein) or body protein gain and protein intake exhibited significantly different slopes, that of LL being superior to that of FL. 4. At a given protein intake, feather protein gain was also superior in LL to FL. Moreover feather protein, as a percentage of total protein gain, was superior in LL to FL. When the dietary protein fell below 126 g/kg, feather protein represented a higher proportion of total protein gain. 5. Multiple linear regressions of protein intake (as the dependent variable), and body weight and protein gain or weight gain (as the independent variables) suggest that the maintenance requirement for protein is similar in both lines but that the protein efficiency for growth is significantly superior in LL. 6. In a second experiment both genotypes were offered either a single high protein diet (232 g/kg) or a single medium protein diet (186 g/kg) or had free-choice between a high (269 g/kg) and a low protein (145 g/kg) diet. In free-choice feeding, FL chickens selected an overall dietary protein content which was significantly lower (179 v. 200 g/kg) to that of LL. In both genotypes, free-choice feeding led to fatter and less efficient chickens than predicted by the linear regression between adiposity or food conversion and protein content.     

Relationship between body fatness,ovarian structure and reproduction in mature females from lines of genetically lean or fat broilers given different food allowances

1. Reproductive and other characteristics were measured at 34 and 60 weeks of age in broiler breeder hens on 6 different feeding regimes. The hens came from genetically lean and fat lines selected on the basis of low or high 7‐week plasma very low density lipoprotein (VLDL) concentration.

2. Plasma VLDL concentrations were consistently higher at all ages in fat line hens but were not affected by dietary treatment.

3. Mature body weight did not differ between the lines in birds fed ad libitum but with food restriction throughout life, fat line birds were lighter at 34 weeks.

4. There was little difference between the lines in abdominal fatness of birds fed ad libitum up to 60 weeks. Fat line birds were always fatter than lean line counterparts under food restriction.

5. Egg production was higher in lean line birds fed ad libitum but food restriction improved egg production in both lines. Peak egg productions were similar in both lines but there was evidence that the optimal food allowances for egg production was higher in the lean compared with the fat line.

6. Ovarian yellow follicle numbers were highest at 34 weeks in ad libitum fed lean line birds and declined linearly with decreasing body weight caused by food restriction but there was no such relationship in fat line birds.

7. White follicle numbers were higher and follicular atresia was lower in the lean line.

8. It is concluded that poor reproduction in fat line birds was associated with inhibition of follicular development and atresia rather than by high plasma VLDL concentrations promoting excessive yolk formation.     

Divergent selection of lean and fat lines of broilers over eight generations using plasma very low density lipoprotein as selection criterion

1. Male and female broilers from a male grandparent line have been selected over 8 generations on the basis of low or high plasma very low density lipoprotein (VLDL) concentration. This has given lines of lean and fat broilers.

2. Plasma VLDL concentration in the two lines has diverged steadily and showed a 7‐fold difference in the 8th generation.

3. Divergence of other traits, including abdominal and total body fat, body protein and conversion efficiencies of food and dietary protein has continued but body weight has not changed with selection.

4. Divergence of body composition and nutrient conversion relative to a commercially selected control line derived from the same origin as the experimental lines has been slightly greater for the fat line.

5. In the lean line, females have been more responsive to selection with the result that body compositions of lean line males and females at 7 weeks have become quite similar.

6. Plasma VLDL concentration decreased little in the lean line over the later generations and showed a lower phenotypic correlation with abdominal fatness than in the fat line in the 8th generation. A limit to selection for body fatness using this criterion may be approaching in the lean, but not in the fat, line.     

发情期和乏情期哈萨克羊垂体差异表达基因筛选及功能预测

垂体是哺乳动物重要的内分泌器官之一,主要通过调控激素合成来调节动物发情。为了研究绵羊垂体系统在发情状态和乏情状态之间的基因表达差异,本研究使用RNA-seq技术分析了发情期和乏情期哈萨克羊垂体前叶的转录组数据。通过比较转录组数据发现:在发情期和乏情期的哈萨克羊垂体中共筛选出了3 211个差异表达的基因,其中包含298个上调的和2 913个下调的基因。利用GO和KEGG富集分析这些差异表达的基因发现:它们被显著地富集在卵母细胞减数分裂和孕酮介导的卵母细胞成熟等调控发情的信号通路上,提示这些基因在调控哈萨克羊发情状态中发挥着不可或缺的作用。本研究丰富了绵羊的转录组资源,为今后深入研究绵羊季节发情机制、提高绵羊繁殖率打下了良好的基础。     

Comparative responses of genetically lean and fat broiler chickens to dietary threonine concentration

Genetically lean (LL) or fat (FL) male broiler chicken's were fed on 5 diets containing either 3.80, 4.27, 4.75, 5.22 or 5.70 g true digestible threonine per kg. Threonine deficiency induced a more pronounced reduction in growth in the LL than in the FL but did not influence abdominal fat and breast muscle proportions in either line. Plotting weight gain or protein gain against threonine intake suggests that the requirement of both lines is very similar in terms of mg per g of gain. Thus food intake or appetite should account for differences between genotypes. Requirement for true digestible threonine was estimated as 10.70 mg per g of weight gain or 63.8 mg per g of protein gain, using a linear regression approach. The quadratic polynomial equations suggest that the requirements are 13.9 and 12.4 mg digestible threonine per g of gain for LL and FL respectively.     

Proteomics analysis of preadipocytes between fat and lean broilers

ABSTRACT

1. Reducing excessive chicken body fat deposition is a main goal of the poultry industry. Preadipocytes are important in adipose tissue growth and development.

2. To discover proteins related to chicken fat deposition, two-dimensional fluorescence difference gel electrophoresis (2-D DIGE) was used to identify differentially expressed proteins in preadipocytes derived from Northeast Agricultural University broiler lines divergently selected for abdominal fat content (NEAUHLF).

3. A total of 46 differentially expressed protein spots were found in the preadipocytes between fat and lean broilers. Matrix-assisted laser desorption-ionisation time-of-flight mass spectrometry (MALDI-TOF-MS) analysis showed the protein spots corresponded to 33 different proteins. The proteins were mainly related to biological oxidation, cell proliferation, cytoskeleton, lipid metabolism, molecular chaperone, protein synthesis and signal transduction.

4. From the perspective of protein expression, these results lay a foundation for further study of the genetic mechanism of broiler adipose tissue growth and development.     

Changes to daily feed intake during the laying period alters embryonic MSTN and MYOG gene expression in genetically fat and lean lines of chickens

1. Broiler breeders are unable to self-regulate feed intake to a level that permits reproductive function and restricted feeding is normal for broiler parent stock. The aim of this study was to determine whether myostatin (MSTN) and myogenin (MYOG) mRNA expression could be altered in relation to differences in body composition of the embryos and the hen’s diet.

2. A 2 × 2 factorial experiment was conducted with two dietary intake levels (100% and 75% of nutrition recommendation) and two broiler genotypes (Fat line and Lean line). Hens (384 of each line) were randomly divided at 23 weeks of age into 4 treatments, with each treatment represented by 12 replicates of 16 birds each. The experiment started when the rate of lay reached 5% and continued until 54 weeks of age.

3. There were significant effects of line and dietary intake, and interactions between them on MSTN and MYOG mRNA expression levels in embryonic tissues. The trend in MSTN mRNA expression level over the embryonic period was similar between lines. Low daily feed intake did not alter the trend in MSTN mRNA expression levels in either line, but significantly changed the peak values. MYOG mRNA expression varied by line and over time, with a delay in the Lean line. Low daily feed intake influenced the trend in MYOG mRNA expression levels in both lines and delayed its onset.     

Effect of daily feed intake in laying period on laying performance, egg quality and egg composition of genetically fat and lean lines of chickens

1. The objectives of this study were to evaluate the effects of feed intake on laying performance, egg quality and egg composition in a Fat line and a Lean line during the laying period (34 to 54 weeks of age). 2. The experiment was a 2 × 2 factorial design with two dietary intake levels (nutrition recommendation and 75% of recommendation) and two broiler genotypes (Fat line and Lean line). Hens (384 of each line) were randomly divided at 23 weeks of age into 4 treatments, with each treatment represented by 12 replicates of 16 birds each. The experiment started when the rate of lay reached 5% and continued until 54 weeks of age. 3. The results indicated that there was a significant interaction between daily feed intake and genotype on egg production, egg weight, percentage yolk, yolk/albumen ratio and yolk cholesterol content. Fat line hens produced significantly more eggs and had a lower incidence of cracked eggs than the Lean line hens. The reduction in feed intake decreased egg weight and increased egg production, egg-shape index and cholesterol content of yolk significantly.     

Liver X receptor alpha and beta genes have the potential role on loin lean and fat content in pigs

Liver X receptor alpha (LXRA) and beta (LXRB) are members of the nuclear receptor subfamily and are important regulators of genes involved in lipid, fatty acid and glucose metabolism in liver, and adipose tissue as well as in skeletal muscle. To investigate whether the two LXR genes play a role in influencing lean and fat growth in pigs, we discovered and examined two polymorphisms in LXRA (LXRA Bsl in exon 2, and LXRA HpyCH4 III in intron 8) and one polymorphism in LXRB (LXRB Aci I in exon 5) for genetic linkage and association analyses. Linkage analyses using a three‐generation resource family of a cross between the Berkshire and Yorkshire (BY) pig breeds assigned LXRA to SSC2 and LXRB to SSC6. Association analyses were carried out among those polymorphisms and traits evaluated in the BY F₂ family and four pig commercial populations. These analyses indicated that the LXRA HpyCH4 III polymorphism was significantly associated with loin eye area and total lipid in individuals from the BY family. Significant associations were also found between Bsl I polymorphism in LXRA and boneless loin (%), as well as marbling score in one commercial line. The LXRB Aci I polymorphism was significantly associated with lean meat and fat content in the BY family and a number of the commercial lines examined. Our current findings suggested that LXRA and LXRB might have potential effects, especially for loin lean and fat content.     

Development of divergent lines of lean and fat broilers using plasma very low density lipoprotein concentration as selection criterion: The first three generations

1. Male and female broilers of a pure line were selected over three generations on the basis of high or low plasma very low density lipoprotein (VLDL) concentration at 7 weeks of age.

2. Heritability of plasma VLDL was high (h ² = 0·50 ± 0·08) and by the third generation mean values in the two lines differed by a factor of 2·5.

3. Correlated responses to selection for low plasma VLDL included a relative decrease in abdominal fat and total body lipid and an increase in body protein, together with improvements in the conversion efficiences of food and dietary protein.

4. There was no difference between the lines in 7‐week body weight.

     

Development of divergent lines of lean and fat broilers using plasma very low density lipoprotein concentration as selection criterion; results over the fourth generation and lack of effect of dietary fat on performance and carcase fat content

Comparisons were made of the performance and carcase composition of lean and fat broilers from the 4th generation of a breeding experiment which were fed diets containing 25 or 80 g fat/kg. Selection over the 4th generation resulted in continued divergence in the selection trait and the correlated responses of total body lipid and protein contents and the efficiencies of conversion of food and dietary protein. In both lines body weight, efficiency of food utilisation and total body lipid and protein contents were unaffected by dietary fat content. Tissue fatty acid composition was influenced by dietary and genetic factors: dietary fat increased the proportions of linoleic and oleic acids at the expense of palmitic, palmitoleic and stearic acids whilst greater body fatness increased the proportion of palmitoleic at the expense of linoleic acid.     

Growth hormone releasing factors and secretion of growth hormone in sheep,calves and pigs

Human pancreatic growth hormone releasing factors (hpGRF) (1–40) and (1–44) were administered iv in sheep, pigs and calves to determine their effectiveness in stimulating GH release in these species. Both peptides produced a rapid increase in plasma GH concentration in all three species at dose levels ranging from .0065 to .65 nmol/kg. Moreover, there was no difference in the GH-secretory response observed between hpGRF(1–44)NH₂ and (1–40)OH in sheep. Sheep also responded to hpGRF(1–40)NH₂ and (1–40)OH as well as [his₁]- and [tyr₁]-hpGRF(1–40)NH₂ in a similar manner. Rat hypothalamic GRF was less effective than [his₁]-hpGRF(1–40), while the response to bGRF was not significantly different from hpGRF(1–40) in stimulating GH secretion in sheep. Although all three species responded to hpGRF, the elevation in plasma GH levels above baseline were greater after hpGRF injection in sheep than in pigs or calves. Subcutaneous injection of hpGRF in sheep was an effective mode of administration of the peptide, although the effect was not as long-lasting as that after iv injections and higher doses were required to stimulate GH secretion.     

Estimates of genetic parameters and predicted selection responses for growth, fat and lean traits in mice

Heritabilities (?2) and genetic correlations (rG) were estimated by regression of offspring on sire in two replicate, unselected lines of mice. Traits were associated with growth, feed efficiency, fat deposition and lean tissue. The ?2 for growth traits ranged from .34 to .42, except for 3-wk body weight, which was only .05. The ?2 for feed efficiency was .28. Ranges in ?2 were .45 to .50 for fat deposition traits and .36 to .42 for lean tissue traits. The rG involving 3-wk to 6-wk feed efficiency with hind carcass and fat measurements at 12 wk were small. Antagonisms were found between the sign of rG and the direction of usual breeding goals for pairs of traits (e.g., rG greater than 0 between fat deposition and hind carcass weight and rG less than 0 between hind carcass as a percentage of body weight and body weight). Selection indexes were developed to counteract these antagonisms. Modified selection indexes were compared where responses in individual traits rather than the aggregate breeding value were of major importance. The aggregate breeding values and selection indexes included: 1) epididymal fat pad weight and body weight, 2) hind carcass weight and body weight, or 3) all three traits. Economic weights in retrospect were calculated for the modified selection indexes. In some cases, expected correlated responses in component traits were not influenced greatly over a wide range of ratios of economic weights, but in other cases the component traits changed sharply over a narrow range of ratios.     

The effects of dietary protein independent of essential amino acids on growth and body composition in genetically lean and fat chickens

1. Growth performance between 28 and 49 d of age and carcase composition at 49 d in genetically lean (LL) and fat (FL) broilers fed on diets varying in non-essential amino acid (NEAA) concentrations were compared in 2 experiments. In experiment 1, 3 crude protein (CP) contents (133, 155, and 178 g/kg) were compared. In experiment 2, 4 CP levels (131, 150, 170 and 189 g/kg) were compared. All diets were supplemented with synthetic amino acids to cover the EAA requirement of the LL birds. 2. Weight gains of FL chickens were not affected by dietary treatments, while those of LL increased when CP level increased. 3. Reducing CP content always increased body lipids, abdominal fat and food conversion ratio in both lines in both experiments; however, the effect on abdominal fat was more pronounced in the FL birds. 4. Reducing CP concentration always decreased breast muscle proportion in both lines in both experiments, even when growth rate was not affected by CP. 5. It is concluded that LL chickens require diets more concentrated in NEAA than fat chickens and that there seems to be an effect of NEAA on breast muscle development.     

Neuroendocrine regulation of growth hormone secretion in sheep. V. Growth hormone releasing factor and thyrotrophin releasing hormone.

The effects of intravenous (IV) and intracerebroventricular (ICV) administration of either bovine growth hormone releasing hormone (GRF) or thyrotrophin releasing hormone (TRH) on plasma growth hormone (GH) and glucose levels have been examined in sheep. Intravenous GRF 1-29NH2 at 3 and 30 micrograms stimulated an increase in GH levels in a dose-dependent fashion; administration of GRF into a lateral cerebral ventricle, however, produced a smaller GH response which was similar at these two doses. Evaluation of somatostatin levels in petrosal sinus blood (which collects pituitary effluent blood) showed that ICV administration of GRF stimulated a release of somatostatin into the blood. Furthermore, concurrent administration of GRF and a potent anti-somatostatin serum ICV resulted in a much enhanced release of GH which was similar to that obtained with a comparable dose of GRF given IV. TRH (as another putative GH-secretagogue) was also administered both IV and ICV. When given IV, 200 micrograms (but not 100 micrograms) TRH produced an elevation in GH levels. By contrast, when 5 micrograms TRH was given ICV there was a decrease in circulating GH levels, but no change in plasma somatostatin concentrations. These results indicate that the smaller GH response to ICV- compared with IV-administered GRF is due to the release of somatostatin within the brain. In addition, it would seem that TRH is not a physiological GH-secretagogue in sheep.