The present study was conducted to evaluate the effects of different rearing methods and stocking densities on carcass yield and proximate composition of meat in small-sized meat ducks. A total of 555 one-day-old birds were randomly allocated to six treatment groups (three replicates per treatment, sex ratio 1/1) with a 2 × 3 factorial arrangement of two rearing methods (reared in cage or net) and three stocking densities (5 [low], 7 [medium], or 9 [high] birds/m 2 ) until day 70. Five male and five female birds from each replicate were randomly selected and processed to determine the carcass yield. Proximate composition was determined by proximate analysis using the breast and thigh muscles. There was no interaction effect between the rearing method and stocking density on carcass yield. The rearing method affected the thigh muscle rate, which was higher in the cage groups ( P < 0.05). The final BW and abdominal fat rate decreased with increasing density ( P < 0.05), whereas the thigh muscle rate increased ( P < 0.05). There were significant interaction effects ( P < 0.05) between the rearing method and stocking density on the content of protein, fat, and collagen. The content of fat and moisture was greater and lower, respectively, in the cage groups ( P < 0.05). The content of moisture, fat, and collagen with a medium density was higher ( P < 0.05). In addition, the content of protein and fat was lower in the ducks fed in nets at low and high densities ( P < 0.05), respectively; the collagen content of breast and thigh muscle was lower in the ducks fed in cages and nets, respectively, at a low density ( P < 0.05). Our findings provide valuable insights into the single and interactive effects of the rearing method and stocking density on duck slaughter performance and proximate composition of meat. The results indicate that a rearing system with a cage pattern and a medium density is better than other arrangements for small-sized meat ducks.

The objectives of this study were to reveal protein molecular structure in relation to rumen degradation kinetics and intestinal availability in combined feeds of hulless barley with bioethanol coproduct [pure wheat dried distillers grains with solubles (DDGS)] at 5 different ratios (100:0, 75:25, 50:50, 25:75, and 0:100) in dairy cattle. The parameters assessed included 1) protein chemical profiles, 2) protein subfractions partitioned by the Cornell Net Carbohydrate and Protein System, 3) in situ protein degradation kinetics, 4) truly absorbed protein supply in the small intestine (DVE), metabolizable protein characteristics and degraded protein balance (OEB), 5) protein molecular structure spectral profiles, and 6) correlation between protein molecular structure and protein nutrient profiles and metabolic characteristics. We found that 1) with increasing inclusion of wheat DDGS in feed combinations, protein chemical compositions of crude protein (CP), neutral detergent-insoluble CP, acid detergent-insoluble CP, and nonprotein N were increased, whereas soluble CP was decreased linearly; CP subfractions A, B₃, and C were increased linearly, but CP subfractions B₁ and B₂ were decreased; truly digestible CP increased but total digestible nutrients at 1× maintenance decreased linearly; protein degradation rate was decreased without affecting potentially soluble, potentially degradable, and potentially undegradable fractions, and both rumen-degradable protein and rumen-undegradable protein were increased; by using the DVE/OEB system, the DVE and OEB values were increased from 98 to 226 g/kg of dry matter and -1 to 105 g/kg of dry matter, respectively; 2) by using the molecular spectroscopy technique, the spectral differences in protein molecular structure were detected among the feed combinations; in the original combined feeds, amide I and II peak area and ratio of amide I to II were increased linearly; although no difference existed in α-helix and β-sheet height among the combinations, the ratio of α-helix to β-sheet height was changed quadratically; 3) in the in situ 48-h residue samples, amide I and amide II peak area intensities were increased linearly and the ratio of amide I to II peak area was decreased linearly from 4.28 to 2.63; α-helix and β-sheet height of rumen residues were similar among 5 feed combinations; and 4) the ratio of α-helix to β-sheet height in original feed combinations was strongly correlation with protein chemical and nutrient profiles, but the ratio of amide I to II area had no significant correlation with all items that were tested; no correlation was found between the ratio of α-helix to β-sheet height of the in situ rumen residues and protein chemical and nutrient profiles. In conclusion, by integration of hulless barley with bioethanol coproduct of wheat DDGS, feed quality in combined feeds was improved and more optimized. Adding wheat DDGS increased linearly CP, truly digestible CP, rumen-degradable protein, rumen-undegradable protein, DVE, and OEB values in combined feeds. The mole...

ABSTRACT. DNA methylation is essential for adipose deposition in mammals. We screened SNPs of the bovine DNA methyltransferase 3b (DNMT3b) gene in Snow Dragon beef, a commercial beef cattle population in China. Nine SNPs were found in the population and three of six novel SNPs were chosen for genotyping and analyzing a possible association with 16 meat quality traits. The frequencies of the alleles and genotypes of the three SNPs in Snow Dragon beef were similar to those in their terminal-paternal breed, Wagyu. Association analysis disclosed that SNP1 was not associated with any of the traits; SNP2 was significantly associated with lean meat color score and chuck short rib score, and SNP3 had a significant effect on dressing percentage and back-fat thickness in the beef population. The individuals with genotype GG for SNP2 had a 25.7% increase in lean meat color score and a 146% increase in chuck short rib score, compared with genotype AA. The cattle with genotype AG for SNP3 had 35.7 and 24% increases in dressing percentage and 28.8 and 29.2% increases in back-fat thickness, compared with genotypes GG and AA, respectively. Genotypic combination analysis revealed significant interactions between SNP1 and SNP2 and between SNP2 and SNP3 for the traits rib-eye area and live weight. We conclude that there is considerable evidence that DNMT3b is a determiner of beef quality traits.

A previous in vitro study revealed that Arg elicits positive effects on casein synthesis through alterations of the Arg-ornithine pathway in bovine mammary epithelial cells. The main purpose of this work was to determine the effects of arginase inhibition using N-hydroxy-nor-l-arginine (nor-NOHA) on milk protein synthesis in vivo. Six healthy Chinese Holstein cows with similar body weight (550.0 ± 20 kg; means ± standard deviation), parity (4), body condition score (3.0), milk yield (21.0 ± 1.0 kg), and days in milk (80 ± 2) were selected and randomly assigned to 3 treatments in a replicated 3 × 3 Latin square design with 22 d for each period (7 d for infusion and 15 d for washout). The treatments were (1) control: saline infusion; (2) nor-NOHA: infusion of 125 mg/L of nor-NOHA; (3) nor-NOHA + Arg: infusion of 125 mg/L of nor-NOHA with 9.42 g/L of Arg. The activity of enzymes related to Arg metabolism, milk protein synthesis, and expression of AA transporters was determined. The infusion of nor-NOHA decreased the activity of arginase but had no effect on the activity of ornithine decarboxylase and nitric oxide synthase in serum, and these responses were the same at the gene expression level in mammary gland. In addition, the infusion of nor-NOHA also reduced protein and fat synthesis in milk but had no effect on milk yield. When Arg was infused with nor-NOHA, the activity of total arginase, ornithine decarboxylase, and nitric oxide synthase, and the concentration of casein, protein, and fat in milk did not change compared with the nor-NOHA group, but the milk protein yield, the expression of some Arg transporters (SLC7A5 and SLC7A8), and milk yield increased. Overall, results verified previous in vitro findings indicating that synthesis of casein protein is closely regulated by the Arg-ornithine pathway in bovine mammary gland.

The insecticidal efficacy of Bt cotton under different environments has generated controversy in recent years. The objective of this study was to investigate possible reasons of the conflicting results caused by temperature stress. Two different types of Bt transgenic cotton cultivars (a Bt cultivar, Sikang1, and an hybrid Bt cultivar, Sikang3) were selected. The plants of the two Bt cultivars were exposed to high temperature (37°C), low temperature (18°C), and the control (27°C) for short (24 h) and long (48 h) periods of stress at peak boll stage, and then moved to the glasshouse where the control plants were maintained. The results showed that the leaf insecticidal toxin content fully recovered within 24 h to the level of control after the end of short duration high-temperature treatment, and recovered mostly within 48 h of the termination of 24 h low-temperature stress. Under long duration high temperature treatment the Bt toxin content required longer recovery periods (48 and 72 h for Sikang3 and Sikang1, respectively) to reach the control level. The Bt protein content only recovered partially at 96 h after the end of the long-duration low-temperature stress, and the concentrations of the Cry1Ac protein were 74% and 77% of the corresponding control for Sikang1 and Sikang3, respectively. The different recovery and increase slowly of the leaf nitrogen metabolic rates after ceasing the heat and cold stress may be possible reason for the above difference. In summary, the duration and type of temperature (cold or heat) stress may cause different Bt insecticidal protein recovery rate due to different recovery rate of enzymes.