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Amino acid in farm animal nutrition metabolism, partition and consequences of imbalance

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... Serum BUN can also be used as an indicator of protein metabolism. Low BUN values indicate that the animal can make effective use of dietary nitrogen to synthesize whole-body protein and maintain a high protein deposition rate (Malmlof, 1988). We observed that dietary GAA supplementation decreased serum BUN levels and increased ALT and AST activities, and BT supplementation resulted in the same effects on BUN and ALT. ...
Article
This study was carried out to evaluate the impacts and interactions of guanidinoacetic acid (GAA) and betaine (BT) supplementation of soybean-meal-based diets on the growth, meat quality, and methionine utilization in the bullfrog Lithobates catesbeianus. A basal diet was supplemented with 0 or 4 g/kg of BT and/or 0, 0.4, or 4 g/kg GAA to formulate six experimental diets, designated Control (BT/GAA: 0/0), B0G0.4 (0/0.4), B0G4 (0/4), B4G0 (4/0), B4G0.4 (4/0.4) and B4G4 (4/4). Each diet was fed to three individual bullfrogs (initially weighing 51.70 ± 0.33 g) for 8 weeks. As a result, bullfrogs fed diets with GAA showed greater weight gain than the control group (P < 0.05). The addition of GAA or BT to the diets increased whole-body protein deposition and the hind leg index (P < 0.05). Diets supplemented with GAA led to reduced muscle glycolysis, which increased the muscle pH value 24 h after euthanasia (P < 0.05). However, a combination of BT and GAA had an insignificant effect on the expression of betaine homocysteine methyltransferase mRNA compared with the diets supplemented with GAA-only (P > 0.05). The findings of this study suggest that dietary GAA supplementation improves bullfrog growth performance and muscle energy metabolism after slaughter, but GAA combined BT supplementation does not improve methionine utilization for bullfrog.
... Urea nitrogen concentration reflects the balance between amino acid metabolism and protein synthesis in vivo. A reduced level of urea nitrogen corresponds to a higher rate of protein synthesis (Malmolf, 1988). A previous study have demonstrated that balance of N in animals is positively influenced by introducing Moringa foliage meal in the diet of Mong Cai pigs (Ly, Samkol, Phiny, & Bustamante, 2016). ...
Article
Moringa oleifera has been considered as a potential functional feed or food, since it contains multiple components beneficial to animal and human. However, little is known about the effects of Moringa oleifera supplementation on productive performances in sows. In the current study, the results showed that dietary Moringa oleifera significantly decreased the farrowing length and the number of stillborn (p < .05), while had an increasing trend in the number of live‐born (0.05 < p < .10). Furthermore, 8% Moringa oleifera supplementation significantly elevated protein levels in the colostrum (p < .05); 4% Moringa oleifera lowed serum urea nitrogen of sows after 90 days of gestation (p < .05) and significantly decreased serum glucose on 10 days of lactation (p < .05). Both groups showed significant elevation in serum T‐AOC activity (p < .05). The serum malondialdehyde (MDA) of sows declined significantly in 4% Moringa oleifera addition group (p < .05). 8% Moringa oleifera meal significantly elevated serum CAT activity after 60 days of gestation (p < .05), while decreased the serum MDA level and increased the serum GSH‐Px activity of sows at 10 days of lactation (p < .05). Of piglets, both two dosages of Moringa oleifera supplementation essentially reduced the serum urea nitrogen (p < .05), and 4% Moringa oleifera meal increased serum total protein (p < .05). In addition, piglets that received 8% Moringa oleifera had the highest serum CAT and SOD activities among all groups (p < .05). The present study indicated that Moringa oleifera supplementation could enhance the reproduction performances, elevate protein levels in the colostrum and improve the serum antioxidant indices in both sows and piglets.
... A reduced level of BUN corresponds to a higher rate of protein synthesis (Malmlof 1998). In this study, the significantly reduced BUN level in the nickel-complex treated groups suggests increased protein synthesis and enhanced immunity in pearl oysters. ...
Article
In the pearl cultivation industry, the implantation of the nucleus is a critical step in the production process. The surgical insertion of the nucleus and the mantle results in a wound and stress that affect not only the survival chances of the pearl oysters but also the quality of the pearls produced. This study proposes a synthesized imidazole-dicarboxylic acid nickel complex that may hold potential in assisting the wound healing and nacre formation processes. The acute toxicity of the complex to pearl oysters, Pinctada martensii, was examined in a dose–response study over a 90-h exposure. The safe concentrations of the nickel complex determined using probit analysis were 0.916 mg/L and 0.471 mg/L for 72-h and 96-h treatments, respectively. The reliability of the regression was verified using the chi-square test. The alkaline phosphatase (ALP) activity in different regions of the treated and control oysters, along with relevant blood biochemical indices, were measured over a 90-d period to predict the potential effects of the nickel complex on wound healing and nacre formation. A significant increase in ALP activity in the mantle, together with elevated blood levels of Mg (II) and globulin, and reduced blood levels of Zn (II) and blood urea nitrogen were observed. These results indicate that the prepared nickel complex may hold promise in helping wound healing post mantle implantation, promote the secretion of nacre, and enhance the immunity of the oysters, thus ultimately improving the yield and quality of the pearls.
... Current study showed that supplemented dried mealworm stimulated the IGF-1 secretion and it had a positive influence on growth and feed efficiency. High level of BUN indicated that excessive amino acids were metabolized and circulated in the blood (Malmolf, 1988). Therefore, BUN concentration can be considered as an indicator for measurement of protein property and amino acid availability by animals (Eggum, 1970). ...
Article
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This experiment was conducted to investigate the effects of dietary mealworm (Tenebrio molitor larva) on growth performance, nutrient digestibility and blood profiles in weaning pigs. A total of 120 weaning pigs (28 ± 3 days and 8.04 ± 0.08 kg of BW) were allotted to one of five treatments, based on sex and body weight, in 6 replicates with 4 pigs per pen by a randomized complete block (RCB) design. Five different levels of dietary mealworm (0, 1.5, 3.0, 4.5 or 6.0 %) were used as dietary treatments. Two phase feeding programs (phase I for 0-14 day, phase II for 14-35 day) were used in this experiment. All animals were allotted to access diet and water ad libitum. During phase I, increasing level of dietary mealworm in diet linearly improved the body weight (P<0.01), ADG (P<0.01) and ADFI (P<0.01). During phase II, ADG also tended to increase linearly when pigs were fed higher level of dietary mealworm (P=0.08). As a results of growth performance, increasing level of dietary mealworm improved the ADG (P<0.01) and ADFI (P<0.05) and tended to increase G:F ratio (P=0.07) during the whole experimental period. As dietary mealworm level was increased, nitrogen retention and digestibility of dry matter as well as crude protein were linearly increased, respectively (P=0.05). In the results of blood profiles, decrease of blood urea nitrogen (linear, P=0.05) and increase of IGF-1 (linear, P=0.03) were observed as dietary mealworm was increased in diet during phase II. However, there were no significant differences in IgA and IgG concentration by addition of dietary mealworm on the growth trial. Consequently, supplementation of dietary mealworm up to 6% in weaning pig's diet could improve growth performance and nutrient digestibility without any detrimental effect on immune responses.
... Serum concentrations of hormones and urea nitrogen reflected the metabolic status of animals [20]. Insulin growth factors (IGFs) are integral components of multiple systems controlling both growth and metabolism [21] and serum urea nitrogen could reflect protein metabolism and amino acid balance of animals [22]. In the present study, dietary supplementation with LY and SFY increased serum concentrations of GH, T 3 , T 4 , and IGF-1, and reduced serum concentration of serum urea nitrogen in weaned piglets. ...
Article
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The present study was conducted to determine effects of different forms of yeast (Saccharomyces cerevisiae, strain Y200007) on the growth performance, intestinal development, and systemic immunity in early-weaned piglets. A total of 96 piglets (14-d old, initial average body weight of 4.5 kg) were assigned to 4 dietary treatments: (1) basal diet without yeast (Control); (2) basal diet supplemented with 3.00 g/kg live yeast (LY); (3) basal diet supplemented with 2.66 g/kg heat-killed whole yeast (HKY); and (4) basal diet supplemented with 3.00 g/kg superfine yeast powders (SFY). Diets and water were provided ad libitum to the piglets during 3-week experiment. Growth performance of piglets was measured weekly. Samples of blood and small intestine were collected at days 7 and 21 of experiment. Dietary supplementation with LY and SFY improved G:F of piglets at days 1-21 of the experiment (P < 0.05) compared to Control group. Serum concentrations of growth hormone (GH), triiodothyronine (T3), tetraiodothyronine (T4), and insulin growth factor 1 (IGF-1) in piglets at day 21 of the experiment were higher when fed diets supplemented with LY and SFY than those in Control group (P < 0.05). Compared to Control group, contents of serum urea nitrogen of piglets were reduced by the 3 yeast-supplemented diets (P < 0.05). Diets supplemented with LY increased villus height and villus-to-crypt ratio in duodenum and jejunum of piglets (P < 0.05) compared to other two groups at day 7 of the experiment. Feeding diets supplemented with LY and SFY increased (P < 0.05) serum concentrations of IgA, IL-2, and IL-6 levels in piglets compared to Control. The CD4(+)/CD8(+) ratio and proliferation of T-lymphocytes in piglets fed diets supplemented with LY were increased compared to that of Control group at day 7 of the experiment (P < 0.05). In conclusion, dietary supplementation with both LY and SFY enhanced feed conversion, small intestinal development, and systemic immunity in early-weaned piglets, with better improvement in feed conversion by dietary supplementation with LY, while dietary supplementation with SFY was more effective in increasing systemic immune functions in early-weaned piglets.
... The unused amino acids in the animal's body are hydrolyzed by the liver into ammonia and carbon chain. The ammonia is then further synthesized by the liver into urea or uric acid and released into the bloodstream (Malmlof, 1988). Therefore, BUN levels are regarded as an important indicator of liver and kidney function (Bossart et al., 2001). ...
Article
This study aimed to investigate the effects of mulberry leaf polysaccharides (MLPs) dietary supplements on the growth performance, diarrhea, blood biochemical parameters, and gut microbiota of early weanling piglets. A total of 150 Duroc-Landrace-Yorkshire crossbred weanling pigs (age: 28±2 d; body weight: 9.18±0.46 kg), were used in this study. Subjects were randomly divided into five treatment groups with six replicates in each group (n=5 animals per replicate). The dietary treatments were as follows: l) control treatment (CT): basal diet (BD); 2) low-dose MLPs treatment (LT): 0.3 g/kg of MLPs+BD; 3) medium-dose MLPs treatment (MT): 0.6 g/kg of MLPs+BD; 4) high-dose MLPs treatment (HT): 0.9 g/kg of MLPs+BD; and 5) antibiotic treatment (AT): 0.15 g/kg chlortetracycline+BD. The fasting weight of each animal was measured and recorded in the morning at three time points (0, 10, and 21 d) in addition to food intake per pigpen. These data were then used to calculate the average daily gain (ADG), average daily feed intake (ADFI), and feed-to-gain (F/G) ratio of each subject. The diarrheal status of each piglet was examined and recorded twice daily (morning and afternoon). At the end of the experiment, blood samples were collected for biochemical analysis, and the contents from the ceacum, colon, and rectum were harvested to identify and quantify relevant gut microbiota. Our results showed that there was no significant differences in the ADG, ADFI, or F/G ratio among MLPs-treated groups (P>0.05), but the ADFI in LT, MT, and HT groups were all higher than those of both the CT and AT groups. Additionally, the F/G ratios in LT, MT, and HT groups were lower than those in the CT and AT groups. The LT, MT and HT groups showed a significant reduction in diarrheal incidence (P<0.05) when compared to the CT and AT groups. Biochemical analysis revealed that blood glucose (GLU) levels in all MLPs-treated groups were significantly (P<0.05) lower than in either the CT or AT groups. Blood urea nitrogen (BUN) levels in the MT and HT groups were significantly (P<0.05) different from those in CT and AT group and T3 levels in HT were significantly (P<0.05) higher than those in either the CT or AT groups. Although T4 levels in MLPs-treated groups were not significantly different from the AT control group, both IGF-1 and GH levels in the MT group were significantly higher than those in either the CT or AT groups (P<0.05). Our microbiota results indicated that the overall effects of LT, MT, and HT in both inhibiting gut E. coli and in promoting gut lactobacilli and bifidobacteria were superior than those of both the CT and AT groups. Notably, the HT group (0.9 g/kg MLPs) showed a significantly better inhibitory effect on gut E. coli as well as a significantly better promotional effect on gut-beneficial bacteria when compared to both the CT and AT groups (P<0.05). Collectively, these results suggest that dietary addition of MLPs can improve the ecology of gut microbiota, reduce diarrhea rate, and improve the overall growth performance in early-weanling pigs.
... Our findings further indicate that the dietary supplementation of Bacillus subtilis natto significantly increased total protein, GOT, GPT, AKP, T 3 and T 4 contents in serum of Muscovy ducks, while decreased urea nitrogen, glucose, triglyceride, total cholesterol levels. Malmolf (1988) reported that the serum urea nitrogen concentration was related with the status of protein metabolism and amino acid balance. The serum concentration of urea nitrogen decreases when amino acids are well balanced. ...
Article
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The aim of the present study was to determine whether dietary Bacillus subtilis natto could affect growth performance of Muscovy ducks. A total of 120 hundred Muscovy ducks at the age of 1 day were randomly assigned to four groups (30 Muscovy ducks/group), and fed with diets supplemented with 0% (control group), 0.1%, 0.2%, and 0.4% Bacillus subtilis natto, respectively during the 6-week feeding period. Weight gain, feed intake and feed conversion efficiency of Muscovy ducks were significantly improved by the dietary addition of Bacillus subtilis natto, and the results were more significant in 0.4% dietary Bacillus subtilis natto treatment group; Also, Bacillus subtilis natto reduced Escherichia coli and Salmonella colonies, and increased lactobacilli population in the ileum and the cecum. Biochemical parameters, including total protein, GOT (glutamic oxaloacetic transaminase), GPT (glutamic pyruvic transaminase), AKP (alkaline phosphatase), triiodothyronine (T3) and tetraiodothyronine (T4) contents (pBacillus subtilis natto was added to the diets (p<0.05), and improved duodenum and immune functions. However, the results above were not significantly different between birds fed 0.1% Bacillus subtilis natto supplemented diets and the control group (p>0.05). The results of the present study indicate that diets with 0.4% Bacillus subtilis natto improved the growth performance of Muscovy ducks by increasing the absorption of protein, simulating hormone secretion, suppressing harmful microflora, and improving the duodenal structure and immune functions of Muscovy ducks. It is suggested that Bacillus subtilis natto is a potential candidate to be used use as a probiotic to improve the growth performance of Muscovy ducks.
... This study indicates that dietary dbcAMP can decrease the size of subcutaneous adipocytes and, therefore, backfat thickness in finishing pigs. Malmolf (1988) and Eggum (1970) suggested that the concentrations of urea nitrogen and total protein in serum can accurately reflect protein metabolism and amino acid balance in the whole body. A reduced concentration of urea nitrogen in serum may result from the enhancement of utilization of amino acids for protein deposition and the reduction of amino acids for oxidation in the whole body (Wu, 2009), leading to improvement in G:F Scott and Baxter, 1986). ...
... As a metabolite of glutamine, arginine fulfils an important function as the precursor for NO synthesis, and NO plays an important role in regulating the secretion of the intestine and maintaining its integrity. Malmolf (1988) and Holecek (2002) reported that the serum BUN concentration was related with the status of protein metabolism and balance of amino acids in the animal. The serum BUN concentration decreases when amino acids are well balanced. ...
Article
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An experiment was conducted to investigate the effects of glutamine on growth performance of weanling piglets. Sixty piglets weaned at 21 days of age were randomly assigned to two groups (10 piglets per pen, 3 pens per group). The control group received a maize-soybean meal-based diet. The treatment group received a maize-soybean meal-based diet supplemented with 1.0% free l-glutamine. Piglets were fed the diets for 20 days. Results showed that piglets fed the glutamine diet had lower diarrhoea ratio and shorter diarrhoea duration than those fed the control diet during 20 days after weaning. During the first ten days after weaning, pigs supplemented with glutamine had a 12.05% lower feed:gain ratio than those fed the control diet ( P < 0.05). During the second ten days after weaning, they had a 27.75% higher average daily gain than those fed the control diet ( P < 0.05); there were no differences in the feed:gain ratio and average daily feed intake. During the first ten days after wean - ing, the serum urea nitrogen of pigs supplemented with glutamine was reduced by 17.36% ( P > 0.05) compared to the control. During the second ten days after weaning, serum urea nitrogen was reduced by 4.27% and serum concentrations of total protein increased by 18.70% in pigs supplemented with glutamine compared to the control (P > 0.05). There were no differences in albumin, T 3, T 4 and growth hormone.
... The low level of serum urea nitrogen indicates a higher nitrogen utilization rate (Malmolf, 1988). In our experiment, the content of serum UA fell in the presence of Cr-Pyr and Cr. ...
Article
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The effects of pyruvate (Pyr), creatine pyruvate (Cr-Pyr) and creatine (Cr) on lipid and protein metabolism were compared in broiler chickens. A total of 400 1-day-old male birds (Aconred) were allocated to four groups, each of which included four replicates (25 birds per replicate). Treatments consisted of unsupplemented basal diet (Control), basal diet containing 2% Pyr, basal diet containing 3% Cr and basal diet containing 5% Cr-Pyr. Cr-Pyr and Pyr significantly decreased the hepatic triglyceride and serum total cholesterol concentration (P < 0.01). Cr-Pyr markedly increased the serum non-esterified fatty acid and high-density lipoprotein cholesterol concentrations (P < 0.05), whereas the expression of carnitine palmitoyl transferase I (P < 0.05) and peroxisome proliferators-activated receptor-α (P < 0.01) mRNA in the liver were both decidedly enhanced in the Cr-Pyr group. The relative leg muscle weight was higher in the Cr-Pyr group than in the control group, whereas the serum uric acid content and hepatic glutamic-oxaloacetic transaminase activity were lower in the Cr-Pyr and Cr groups (P < 0.05), respectively. Muscle insulin-like growth factor I (P < 0.05) expression was enhanced, and the myostatin (P < 0.01) mRNA level was reduced in both the Cr-Pyr and Cr groups. In addition, Cr-Pyr did not alter body weight or the feed conversion ratio. These results indicate that, compared with Pyr and Cr alone, Cr-Pyr has a bifunctional role in broiler chickens, in that it influences both lipid and protein metabolism.
Article
This study was conducted to determine the influence of substitution of fish meal with dried mealworm (Tenebrio molitor) larvae on growth performance, nutrient digestibility, blood profiles and fecal noxious gas emission in weaned pigs. A total of 240 crossbred weaned pigs [(Yorkshire × Landrace) × Duroc] at 22 d of age with an average body weight (BW) of 6.90 ± 0.03 kg were randomly allocated into 3 treatments with 8 replicates per treatment and 10 pigs per replicate (pen) according to BW. Dietary treatments included: 1) CON, basal diet with 2% fish meal; 2) T1, basal diet with 1% fish meal and 1% dried mealworm (Tenebrio molitor); T2, basal diet with 2% dried mealworm (Tenebrio molitor). During d 0-7, weaned pigs fed T2 diet had higher (P < 0.05) feed-to-gain ratio (F/G) than those fed CON and T1 diets. During d 8-21, feeding T1 diet decreased (P < 0.05) average daily gain (ADG) compared with CON diet and a quadratic effect on F/G was observed (P < 0.05). During d 0-35, ADG and final BW in T1 treatment was lower (P < 0.05) than that in CON. The apparent total tract digestibility of nitrogen in T1 treatment was lower compared with CON. Dietary treatments did not affect (P > 0.05) red blood cells, white blood cells, lymphocyte, total protein, blood urea nitrogen, insulin-like growth factor or immunoglobulin G and fecal ammonia, hydrogen sulfide or total mercaptans emission. Taken together, the dried mealworm (Tenebrio molitor) larvae did not outperform the fish meal in this study.
One feeding trial and two metabolic trials were conducted to investigate the effects of lysine to protein ratio in practical swine diets on growth performance and efficiency of nitrogen retention and utilization in different growing phases, In Trial one (the feeding trial), 90 mixed sex pigs weighing 9.1 +/-1.4 kg (Duroc x Landrance x Beijing Black) were used to study the effects of concentrations of 5.2, 5.3, 5.8, 6.4 and 7.2 g lysine/100 g CP in diets containing 1.2% lysine on growth performance and serum urea nitrogen. The results showed that feed conversion efficiency and economic efficiency were best for pigs fed the diet containing the lysine concentration of 5.8 g/100 g crude protein. Serum urea nitrogen concentration decreased linearly (p=0.0009) and serum free lysine content increased linearly (p=0.0017) as the lysine to protein ratio in diets increased from 5.2 to 7.2 g/100 g. In Trials two and three (the metabolic trials), five growing barrows (Duroc x Landrance x Beijing black). with initial body weights of approximately 26 +/-2.4 kg and 56.3 +/-3.5 kg, respectively. were allotted to five dietary treatments according to a 5 x 5 Latin square design. Trial two contained 5.2. 5.7, 6.1, 6.7 and 6.8 a lysine/100 g CP treatments. Trial three contained 4.6, 5.0, 5.6, 6.1 and 6.6 g lysine/100 g CP treatments. The results showed that nitro-en retention in growing pigs decreased linearly (p=0.0011 in Trial mo: p=0.0099 in Trial three) as the lysine to protein ratio in diets increased. The ratio of lysine to protein in diets resulting in maximum nitrogen retention was 5.2 g/100 g and 5.0 g/100 g in Trial two and Trial three, respectively. In Trial two. apparent biological value and gross nitrogen efficiency increased linearly (p=0.0135 and p=0.0192, respectively) as the lysine to protein ratio increased from 5.2 to 6.8 g lysine/1100 g CP. In summary, we concluded that the optimal Lysine to Protein Ratios for 8-20 kg and 20-80 kg pigs were 5.8 g/100 g and 5.0 to 5.2 g/100 g, respectively.
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To investigate the effects of dietary supplementation with folic acid on growth performance, hepatic protein metabolism and serum biochemical indices of early-weaned intrauterine growth retardation (IUGR) piglets, 24 male (Duroc×(Landrace×Yorkshire)) weaned (14-d-old) IUGR piglets were randomly divided into 3 treatments with 8 replicates of 1 piglet per replicate. The piglets in each treatment were fed basal diet supplementation with either 0 (control), 5 and 10 mg kg−1folic acid. The trial lasted for 21 d. Dietary folic acid supplementation reduced average daily feed intake (ADFI) (P<0.05). In addition, the average daily gain (ADG) in 10 mg kg−1 folic acid group was significantly decreased (P<0.01) and the ratio of feed:gain (F/G) increased slightly (P>0.05). Serum folic acid concentration increased (P<0.01) with increasing folic acid inclusion, however, serum homocysteine concentration decreased significantly (P>0.01). Enhanced serum urine nitrogen (SUN) and diminished serum total protein (TP) as well as liver TP content were observed in 10 mg kg−1 folic acid group (P<0.05). Furthermore, the relative mRNA expressions of insulin-like growth factor 1 (IGF-1) and mammalian target of rapamycin (m-TOR) in liver were respectively tended to reduce (P=0.06) and significantly downregulated (P<0.05) in 10 mg kg−1 group, in compared with 5 mg kg−1 group. However, when compared with control group, folic acid supplementation had no significant effect on the mRNA abundance of IGF-1 and m-TOR. The results indicated that supplementation with 10 mg kg−1 folic acid impaired growth performance and hepatic protein metabolism of early-weaned IUGR piglets while 5 mg kg−1 folic acid enriched diet exerted limited positive effects.
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Verticillium wilt is a severe disease in eggplant caused by Verticillium dahliae. Polygalacturonase-inhibiting proteins (PGIPs) have been shown to be involved in preventing the invasion of fungus including V. dahliae. Cloning genes encoding PGIPs is quite valuable for plant resistance breeding to Verticillium wilt. In this study, a cDNA encoding the polygalacturonase-inhibiting protein was isolated from Solanum torvum by RT-PCR and RACE, designated StPGIP (accession no. FJ943498). The cDNA sequence of StPGIP was 1 097 bp long and contained an open reading frame of 990 bp. The predicted amino acid sequence of the gene consisted of 329 amino acids and had conserved LRRs. The StPGIP protein had a high identity with PGIPs from other species. Analysis of StPGIP expression at the mRNA level by RT-PCR showed that the gene was expressed in all organs and could be induced to increase expression by V. erticillium dahliae infection.
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The effects of dietary lysine on production performance, serum concentrations of metabolites, growth hormone (GH), insulin-like growth factor-I (IGF-I) and IGF-I mRNA expression in growing rabbits were examined. One hundred weaned New Zealand rabbits were allocated to individual cages and randomly offered a diet containing 5.5 (L1), 6.5 (L2), 7.5 (L3), 8.5 (L4), or 9.5 g (L5) lysine per kg diet. The results showed that the average daily gain (ADG) of the rabbits from L3, L4 or L5 was higher than those from L1 or L2 (P < 0.05). The feed gain ratio (F/G) in the rabbits from L4 or L5 was lower than those from L1 or L2 (P < 0.05). Dietary lysine did not affect serum concentrations of total protein (TP), glucose, insulin (INS), and growth hormone (GH) (P > 0.05). The quadratic effects of lysine on the serum urea nitrogen (SUN) concentration was detected (P = 0.035). Serum IGF-I concentrations had a trend to increase quadratically with the increasing dietary lysine (P = 0.07). A significant correlation was found between serum IGF-I concentrations (x, ng mL−1) and ADG (y, g kg−1): y = −0.017x2 + 1.984x + 20.87 (R2 = 0.8982, P = 0.003). The relative abundance of hepatic and muscular IGF-I mRNA tended to increase with increasing dietary lysine levels (P = 0.053 and 0.082, respectively). Providing the diets mainly consisted of corn, wheat bran and peanut vine, the most appropriate dietary lysine level for growing meat rabbits from weaning to 70 d old was found to be 8.5 g kg−1, and IGF-I may be an important factor controlling growth of weaned rabbits.
Article
An experiment was conducted to determine the effects of different amounts of dietary methionine on growth performance, serum protein, growth hormone (GH), insulin-like growth factor-I (IGF-I) concentrations and IGF-I mRNA expression of growing meat rabbits. One hundred weaned growing meat rabbits were allocated to individual cages and randomly divided into five groups. The methionine addition concentrations of the five groups were 0, 2, 4, 6 and 8 g/kg diet (as-fed basis) and sulphur amino acids (SAA) concentrations ranging from 3.8 to 11.6 g/kg diet, respectively. The results obtained were as follows: the average daily gain of 2, 4 and 6 g/kg diet groups was higher than that of 0 g/kg diet group (p < 0.01). The feed gain ratio of the 4 g/kg diet group was lower than those of 0 and 8 g/kg diet group (p < 0.01). Methionine concentrations did not affect serum urea nitrogen, total protein, insulin and IGF-I concentration (p > 0.05). The quadratic effects of methionine on the serum concentration of albumin (Alb) and GH were obtained (p = 0.013, p = 0.018). The quadratic effect of methionine amount on IGF-I mRNA expression was obtained (p = 0.045). The serum concentration of Alb of the 4 g/kg diet group was higher than those of 0 and 8 g/kg diet group (p < 0.01). The serum concentration of GH of 8 g/kg diet group was higher than that of the 0 g/kg diet group (p < 0.05). The liver IGF-I mRNA expression of 4 g/kg diet group was higher than those of the 0 and 8 g/kg diet group (p < 0.05). Providing a diet mainly consisted of corn, wheat bran and peanut vine, the optimum dietary methionine addition concentration and SAA concentration for a weaner to 2-month-old growing meat rabbits were shown to be 2 and 5.7 g/kg diet respectively.
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