The objective of this study was to assess the morphological integrity and functional potential of mitochondria from postmortem bovine cardiac muscle and evaluate mitochondrial interactions with myoglobin (Mb) in vitro. Electron microscopy revealed that mitochondria maintained structural integrity at 2 h postmortem; prolonged storage resulted in swelling and breakage. At 2 h, 96 h, and 60 days postmortem, the mitochondrial state III oxygen consumption rate (OCR) and respiratory control ratio decreased with time at pH 7.2 and 5.6 (p < 0.05). Mitochondria isolated at 60 days did not exhibit ADP-induced transitions from state IV to state III oxygen consumption. Tissue oxygen consumption also decreased with time postmortem (p < 0.05). Mitochondrial oxygen consumption was inhibited by decreased pH in vitro (p < 0.05). In a closed system, mitochondrial respiration resulted in decreased oxygen partial pressure (pO(2)) and enhanced conversion of oxymyoglobin (OxyMb) to deoxymyoglobin (DeoMb) or metmyoglobin (MetMb). Greater mitochondrial densities caused rapid decreases in pO(2) and favored DeoMb formation at pH 7.2 in closed systems (p < 0.05); there was no effect on MetMb formation (p > 0.05). MetMb formation was inversely proportional to mitochondrial density at pH 5.6 in closed systems. Mitochondrial respiration in open systems resulted in greater MetMb and DeoMb formation at pH 5.6 and pH 7.2, respectively, vs controls (p < 0.05). The greatest MetMb formation was observed with a mitochondrial density of 0.5 mg/mL at both pH values in open systems. Mitochondrial respiration facilitated a shift in Mb form from OxyMb to DeoMb or MetMb, and this was dependent on pH, oxygen availability, and mitochondrial density.

Krzywicki's equations have been widely used for estimating the relative proportions of myoglobin (Mb) redox forms in aqueous solution. However, these equations have generated negative values for some redox forms, and total Mb estimates obtained by summation of the individual redox forms have deviated from unity. The inappropriate selection of wavelengths (545, 565, and 572 nm) used to generate these equations appears to have been responsible for these problems. Therefore, Krzywicki's equations were modified by using wavelength maxima at 503, 557, and 582 nm, representative for metmyoglobin, deoxymyoglobin, and oxymyoglobin, respectively. Millimolar extinction coefficients at these wavelengths were calculated, and a set of modified equations was established for determining the relative proportions of Mb redox forms in aqueous solution. The new equations demonstrated improved performance in decreasing the occurrence and magnitude of negative values and in estimating total Mb, when compared with Krzywicki' original equations.

Bovine mastitis is the most significant economic drain on the worldwide dairy industry. Concerns regarding poor cure rates, emergence of bacterial resistance, and residues in milk necessitate development of alternative therapeutic approaches to antibiotics for treatment of mastitis. A variety of free fatty acids and their monoglycerides have been reported to exert antimicrobial activity against a wide range of microorganisms. The objective of our study was to examine the efficacy of caprylic acid, a short-chain fatty acid, and its monoglyceride, monocaprylin, to inactivate common mastitis pathogens, including Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, Staphylococcus aureus, and Escherichia coli. Milk samples containing 50 mM or 100 mM caprylic acid, and 25 mM or 50 mM monocaprylin were inoculated separately with a 3-isolate mixture of each of the 5 pathogens, and incubated at 39 degrees C. Populations of surviving bacteria were determined at 0 min, 1 min, 6 h, 12 h, and 24 h of incubation. Both caprylic acid and monocaprylin reduced all 5 pathogens by >5.0 log cfu/mL after 6 h of incubation. Among the bacterial species tested, Strep. agalactiae, Strep. dysgalactiae, and Strep. uberis were most sensitive, and E. coli was most tolerant to caprylic acid and monocaprylin. Results of this study indicate that caprylic acid and monocaprylin should be evaluated as alternatives or adjuncts to antibiotics as intra-mammary infusion to treat bovine mastitis.

ABSTRACTThe efficacies oftrans-cinnamaldehyde (TC) and eugenol (EG) for reducingSalmonella entericaserovar Enteritidis colonization in broiler chickens were investigated. In three experiments for each compound, 1-day-old chicks (n= 75/experiment) were randomly assigned to five treatment groups (n= 15/treatment group): negative control (-veS. Enteritidis, -ve TC, or EG), compound control (-veS. Enteritidis, +ve 0.75% [vol/wt] TC or 1% [vol/wt] EG), positive control (+veS. Enteritidis, -ve TC, or EG), low-dose treatment (+veS. Enteritidis, +ve 0.5% TC, or 0.75% EG), and high-dose treatment (+veS. Enteritidis, +ve 0.75% TC, or 1% EG). On day 0, birds were tested for the presence of any inherentSalmonella(n= 5/experiment). On day 8, birds were inoculated with ∼8.0 log10CFUS. Enteritidis, and cecal colonization byS. Enteritidis was ascertained (n= 10 chicks/experiment) after 24 h (day 9). Six birds from each treatment group were euthanized on days 7 and 10 after inoculation, and cecalS. Enteritidis numbers were determined. TC at 0.5 or 0.75% and EG at 0.75 or 1% consistently reduced (P< 0.05)S. Enteritidis in the cecum (≥3 log10CFU/g) after 10 days of infection in all experiments. Feed intake and body weight were not different for TC treatments (P> 0.05); however, EG supplementation led to significantly lower (P< 0.05) body weights. Follow-upin vitroexperiments revealed that the subinhibitory concentrations (SICs, the concentrations that did not inhibitSalmonellagrowth) of TC and EG reduced the motility and invasive abilities ofS. Enteritidis and downregulated expression of the motility genesflhCandmotAand invasion geneshilA,hilD, andinvF. The results suggest that supplementation with TC and EG through feed can reduceS. Enteritidis colonization in chickens.