Rhipicephalus (Boophilus) microplus is one of the most widespread ticks causing a massive loss to livestock production. The long-term use of acaracides rapidly develops acaracide resistance. In R. microplus, enhancing the metabolic activity of glutathione S-transferase (RmGST) is one of the mechanisms underlying acaracide resistance. RmGST catalyzes the conjugation of glutathione (GSH) to insecticides causing an easy-to-excrete conjugate. The active RmGST dimer contains two active sites (hydrophobic co-substrate binding site (H-site) and GSH binding site (G-site)) in each monomer. To preserve the insecticide efficacy, s-hexyl glutathione (GTX), a GST inhibitor, has been used as a synergist. To date, no molecular information on the RmGST-GSH/GTX complex is available. The insight is important for developing a novel RmGST inhibitor. Therefore, in this work, molecular dynamics simulations (MD) were performed to explore the binding of GTX and GSH to RmGST. GSH binds tighter and sits rigidly inside the G-site, while flexible GTX occupies both active sites. In GSH, the backbone mainly interacts with W8, R43, W46, K50, N59, L60, Q72, and S73, while its thiol group directs to Y7. In contrast, the aliphatic hexyl of GTX protrudes into the H-site and allows a flexible peptide core to form various interactions. Such high GTX flexibility and the protrusion of its hexyl moiety to the H-site suggest the dual role of GTX in preventing the conjugation reaction and the binding of acaracide. This insight can provide a better understanding of an important insecticide-resistance mechanism, which may in turn facilitate the development of novel approaches to tick control.

Deproteinization has been recognized as a prerequisite for amino acid analysis of plasma samples. For plasma stored at room temperature, delaying deproteinization for 30, 60 or 120 minutes did not result in significant changes in the mean CV (coefficient of variation), which ranged from 4.4 to 5.6%. However the mean CV of aspartic acid, α-aminoadipic acid, alanine and lysine was about 10%. When the plasma was stored frozen at-20°C, the CV was increased at 0 and 120 minutes after thawing, to 12.4% (range, 4.1 to 35.3%) and 8.0% (2.5 to 30.7%), respectively. The concentrations in plasma during storage at room temperature of all the amino acids analyzed showed significant changes. In plasma stored for 30 minutes at room temperature, 17 amino acids increased in concentrations and two decreased. Extending this period to 60 or 120 minutes increased the instability as compare to the reference group. Storing plasma at-20°C for 2 weeks resulted in significantly greater changes in the amino acid concentrations than at room temperature. On extending the storage time at room temperature, after thawing, to 30, 60, and 120 minutes, 21, 20, and all 22 amino acids respectively changed significantly (p<0.01). The present study indicates that methodological errors occur in the concentrations determined for all amino acids when plasma is left at room temperature. The storage of frozen non-deproteinized plasma accompanied more significant changes in most amino acid concentrations and thus should be avoided. Deproteinization should be performed as soon as possible after plasma collection.

Objective: This study aimed to evaluate the effects of different levels of coated cysteamine HCl (CSH) supplementation on growth performance, carcass traits, and meat quality in Charolais crossbred cattle.Methods: Twenty-four Charolais crossbred steers, aged 24–30 months with an initial body weight of 418±31 kg, were assigned to three dietary treatments: 0% (control), 0.5%, or 1.0% CSH in concentrate. The steers were fed the experimental diets for 200 days.Results: Increased CSH levels in concentrate diets led to significant increases (p<0.05) in body weight, hot carcass weight, cold carcass weight, and dressing percentage. CSH supplementation decreased shear force values and cooking loss (p<0.05). Meat lightness was significantly greater in the 1.0% CSH-supplemented group (p<0.05). With increasing CSH levels, the proportion of high-value cuts, such as rib set and T-bone, increased (p<0.05), while the proportion of lower-value cuts, including macreuse, shank, and tendons, decreased (p<0.05). Non-carcass weights, including the feet, head, digestive tract, and scraps, were significantly higher in the 1.0% CSH-supplemented diet (p0.05). Muscle fiber diameter was significantly larger in the 1.0% CSH-supplemented group (p<0.05). Monounsaturated fatty acids increased (p<0.05) with higher CSH levels, whereas polyunsaturated and saturated fatty acids exhibited a significant decrease (p<0.05).Conclusion: Dietary supplementation with CSH enhances growth rate, carcass traits, and meat quality in steers. An inclusion level of 1.0% CSH in concentrate is the optimum feeding dosage, demonstrating its potential as an effective feed additive for enhancing beef production efficiency.

Objective: This study aims to assess the impact of aging time on the quality of meat, fatty acid profiles, and volatile compounds in cooked Thai native beef. Materials and Methods: The experiment utilized a randomized complete block design, where the aging time (0, 7, 14, 21, and 28 days) served as the treatment and the longissimus thoracis et lumborum muscle from Thai native cattle (n = 4) was considered a block. Results: Meat color and Warner-Bratzler shear force values decreased as the aging time increased. Furthermore, the moisture content decreased while the protein and ash content increased with a longer aging time. The proportions of fatty acids showed significant differences with varying aging times. These fatty acids exhibited the highest proportions in the 14-day dry-aged beef samples. The levels of short-chain aldehydes (pentanal, heptanal, octanal, nonanal, decanal, and 2-non¬enal) and alcohols (1-hexanol and 1-octanol) decreased as the aging time increased. However, there was an increase in long-chain aldehydes (tetradecanal, hexadecanal, heptadecanal, and octadecanal) with longer aging time. In addition, the levels of toluene, dodecane, tridecane, methyl-pyrazine, 2,5-dimethyl-pyrazine, trimethyl-pyrazine, and dimethyl trisulfide were higher in 14-day dry-aged beef compared to beef that had not been aged. Furthermore, a correlation was found between the number of the 6 significant fatty acids in the dry-aged beef samples and the 12 volatile compounds in cooked beef. Conclusion: Our results suggest that aging times significantly influence the fatty acid profiles of Thai native beef, which in turn are correlated with the characteristic volatile compounds.

Poapolathep A, et al. J Vet Sci. 2024 Jul;25(4):e58. https://doi.org/10.4142/jvs.24118