Andrea D. Crum

Antioxidant activity of carnosine in cooked ground pork

Carnosine (0·5-1·5%) reduced (P < 0·05) the formation of thiobarbituric acid reactive substances (TBARS) in cooked unsalted ground pork after 7 days of storage at 4°C. The antioxidant activity of carnosine was less in cooked salted ground pork, with only 1·5% carnosine inhibiting (P < 0·05) TBARS formation during refrigerated storage. The antioxidant activity of carnosine in cooked salted and unsalted ground pork was greater than those of the lipid-soluble free radical scavengers, butylated hydroxytoluene and α-tocopherol (P < 0·05) but less than that of sodium tripolyphosphate (P < 0·05). These data suggest that carnosine could be used to reduce the oxidative deterioration of cooked salted and unsalted ground pork.

Effect of Dietary Starch Source and Concentration on Equine Fecal Microbiota

Starch from corn is less susceptible to equine small intestinal digestion than starch from oats, and starch that reaches the hindgut can be utilized by the microbiota. The objective of the current study was to examine the effects of starch source on equine fecal microbiota. Thirty horses were assigned to treatments: control (hay only), HC (high corn), HO (high oats), LC (low corn), LO (low oats), and LW (low pelleted wheat middlings). Horses received an all-forage diet (2 wk; d -14 to d -1) before the treatment diets (2 wk; d 1 to 14). Starch was introduced gradually so that horses received 50% of the assigned starch amount (high = 2 g starch/kg BW; low = 1 g starch/kg BW) by d 4 and 100% by d 11. Fecal samples were obtained at the end of the forage-only period (S0; d -2), and on d 6 (S1) and d 13 (S2) of the treatment period. Cellulolytics, lactobacilli, Group D Gram-positive cocci (GPC), lactate-utilizers and amylolytics were enumerated. Enumeration data were log transformed and analyzed by repeated measures ANOVA. There were sample day × treatment interactions (P < 0.0001) for all bacteria enumerated. Enumerations from control horses did not change during the sampling period (P > 0.05). All treatments except LO resulted in increased amylolytics and decreased cellulolytics, but the changes were larger in horses fed corn and wheat middlings (P < 0.05). Feeding oats resulted in increased lactobacilli and decreased GPC (P < 0.05), while corn had the opposite effects. LW had increased lactobacilli and GPC (P < 0.05). The predominant amylolytic isolates from HC, LC and LW on S2 were identified by 16S RNA gene sequencing as Enterococcus faecalis, but other species were found in oat fed horses. These results demonstrate that starch source can have a differential effect on the equine fecal microbiota.

Influence of dietary β-alanine and histidine on the oxidative stability of pork.

Carnosine (β-alanine-L-histidine) and anserine (β-alanine-1-methyl histidine) are endogenous antioxidants found in skeletal muscle. The objective of this research was to determine if supplementation of swine diets with histidine (histidine; 0.40%) and/or β-alanine (β-alanine; 0.225%) was an effective method to increase carnosine and anserine concentrations and the oxidative stability of Longissimus dorsi (LD) and Vastus intermedius (VI) muscles. Dietary treatments had no effect on carnosine and anserine concentrations in LD; however, histidine + β-alanine supplementation increased carnosine and anserine in VI muscle compared to β-alanine supplementation. Dietary supplementation had no effect on the formation of thiobarbituric acid reactive (TBARS) or lipid peroxides in cooked VI and LD. In salted VI and LD muscle, differences in TBARS and peroxides were observed; however, these differences did not consistently correlate with differences in anserine and carnosine concentrations. Therefore, the results of this research suggest that supplementation of swine diets with β-alanine and/or histidine is not an efficient method to increase the oxidative stability of pork.

Effect of starch source in pelleted concentrates on fecal bacteria in pre- and postpartum mares

&NA; Dietary starch source has been shown to affect fecal bacterial communities of horses fed minimally processed cereal grains. However, processing may increase foregut starch digestibility, reducing effects of starch source on fecal bacterial communities. This study aimed to determine the effect of starch source in pelleted concentrates on fecal Lactobacillus spp., amylolytic bacteria, and cellulolytic bacteria in broodmares mares, during the prepartum and postpartum period. Thoroughbred mares (n = 18) were paired by last breeding date then randomly assigned to either an oat‐based or a corn and wheat middlings‐based pelleted concentrate fed with forage. Mares were fed their assigned concentrates beginning on 310 days of gestation, and fecal samples were collected at 324 days of gestation, before parturition, 1 day, 14 days, and 28 days postpartum. Fecal samples were enumerated by serial dilution and inoculation into selective, enriched media for Lactobacillus spp., amylolytic bacteria, and cellulolytic bacteria. Data were log transformed then analyzed using a mixed model ANOVA with repeated measures (SAS 9.3) to test the main effects of treatment, time of sample, and treatment by time interaction. Starch source did not affect enumerated bacterial communities (P > .05); thus, pelleting concentrates may alter some of the effects of starch sources on the hindgut microbiota. Sample date did not affect amylolytic bacteria (P > .05); however, lactobacilli and cellulolytic bacteria decreased 1 day postpartum (P < .05). Although we did not observe an effect of starch source on fecal bacteria in mares, parturition did appear to alter the hindgut microbiota.

Redox cycling and generation of reactive oxygen species in commercial infant formulas

Three nationally prominent commercial powdered infant formulas generated hydrogen peroxide, ranging from 10.46 to 11.62 μM, when prepared according to the manufacturers instructions. Treating infant formulas with the chelating agent diethylene triamine pentaacetic acid (DTPA) significantly reduced H2O2 generation. In contrast, the addition of disodium ethylenediaminetetraacetic acid (EDTA) elevated the level of H2O2 generated in the same infant formulas by approximately 3- to 4-fold above the untreated infant formulas. The infant formulas contained ascorbate radicals ranging from about 138 nM to 40 nM. Treatment with catalase reduced the ascorbate radical contents by as much as 67%. Treatment with DTPA further reduced ascorbate radical signals to below quantifiable levels in most samples, further implicating the involvement of transition metal redox cycling in reactive oxygen species (ROS) formation. Supportive evidence of the generation of ROS is provided using luminol-enhanced luminescence (LEL) in both model mixtures of ascorbic acid and in commercial infant formulas.