Effects of increasing dietary niacin on growth performance and meat quality in finishing pigs reared in two different environments

We conducted two experiments to determine the effects of added dietary niacin on growth performance and meat quality in finishing pigs. Pigs were blocked by weight and assigned to one of six dietary treatments in both experiments. Dietary treatments consisted of a corn-soybean meal-based control diet (no added niacin) or the control diet with 13, 28, 55, 110, or 550 mg/kg of added niacin. In Exp. 1, pigs were housed at the Kansas State University research from with two pigs per pen (six pens per treatment per sex). In Exp. 2, pigs were housed with 26 pigs per pen (four pens per treatment per sex) in a commercial research barn. In Exp. 1, 144 pigs (initially 51.2 kg) were fed diets in two phases (d 0 to 25 and 25 to 62) that were formulated to 1.00 and 0.75% lysine, respectively. In Exp. 2, 1,248 pigs (initially 35.9 kg) were fed diets in four phases (d 0 to 28, 29 to 56, 57 to 84, and 85 to 117), with corresponding total lysine concentrations of 1.25, 1.10, 0.90, and 0.65% lysine, respectively. Added fat (6.0%) was included in the first three phases. In Exp. 1, average daily feed intake tended (quadratic, P < 0.07) to increase then return to values similar to control pigs as dietary niacin increased. Longissimus muscle (LM) 24-h pH (longissimus of pigs fed added niacin) tended to increase (control vs niacin, P < 0.06) for pigs fed added niacin. In the commercial facility (Exp. 2), increasing added niacin improved gain:feed (quadratic, P < 0.01) and subjective color score, and ultimate pH (linear, P < 0.01). Added niacin also decreased (linear, P < 0.04) carcass shrink, L* values, and drip loss percentage. Results from these two studies show that 13 to 55 mg/kg added dietary niacin can be fed to pigs in a commercial environment to improve gain:feed. It also appears that pork quality, as measured by drip loss, pH, and color, may be improved by higher concentrations of added dietary niacin.     

Comparison of selection indices to screen lowland rice for drought resistance

Summary Although many selection indices have been used to screen rices (Oryza sativa L.) for drought resistance, there has been little comparison of the relative merits of these indices. Research was conducted to compare drought resistance as estimated from grain yields, canopy-temperature-based stress indices, visual scoring, and uprooting force for 30 rice genotypes grown in the field with a puddled Maahas clay (Typic Tropaquept) and to evaluate traits related to drought resistance from nonstressed plants grown in the field and in aeroponic culture. Water deficit was imposed in the field by withholding irrigation from 45 to 75 days after transplanting compared to a continuously flooded control. Grain yields in the stress treatment were most strongly correlated with visual assessment of drought stress symptoms according to a standard evaluation system (r = 0.66). Canopy-temperature-based indices were also significantly correlated with grain yields of the stress treatment (r from –0.55 to –0.63). No trait of aeroponically grown plants was correlated with traits of stressed plants in the field. We conclude that visual scoring of stressed plants was the best method of screening for drought resistance, but if controlled water deficit cannot be imposed, then drought resistance may be estimated by measuring both uprooting force and grain yield.     

Development of an indirect enzyme-linked immunosorbent assay for detecting equine serum antibodies to the lipopolysaccharide of Salmonella abortusequi

An indirect enzyme-linked immunosorbent assay (IELISA) was developed for the detection of equine serum antibodies to lipopolysaccharide of Salmonella enterica subsp. enterica serovar Abortusequi (LPS), a causative organism of Equine Paratyphoid. The data presented demonstrates that horses immunized with S. abortusequi LPS developed antibodies detectable by the IELISA. By comparison, the tube agglutination test (TAT) did not detect antibody to S. abortusequi LPS as consistently as the IELISA. The data suggests that the IELISA may be a more suitable test for the detection of serum antibodies to S. abortusequi than the TAT.     

Characterization of the probiotic strain Vagococcus fluvialis in the protection of European sea bass (Dicentrarchus labrax) against vibriosis by Vibrio anguillarum

Aquaculture is one of the main sources of income in many countries worldwide. Intensive farms are often affected by different infectious diseases that can decrease their final production. To control this situation, several antibiotics are frequently used with known environmental consequences. The aim of this study was to analyze different bacterial strains isolated from of gilthead sea bream, sea bass, sole and meagre guts, for use as probiotics in aquaculture. The strains were evaluated in vitro through various mechanisms of selection, such as the production of antagonistic effects against pathogens, production of antibacterial substance, adhesion to the intestinal mucus, competition for nutrients or binding site, and growth in intestinal mucus. A total of 50 bacterial strains were analyzed and only one showed excellent in vitro results for consideration as a candidate to be analyzed in vivo. The strain, identified as Vagococcus fluvialis, showed good protection against Vibrio anguillarum 975-1 in vivo in the experimental challenge, showing a relative percent survival of 42.3% higher than positive control group. Therefore, in conclusion we consider this strain to be a good candidate for use as a future probiotic in aquaculture.     

Host–strain mediated selection for an effective nitrogen-fixing symbiosis between Trifolium spp. and Rhizobium leguminosarum biovar trifolii

We have previously reported significant strain–host incompatibility between the microsymbiont Rhizobium leguminosarum biovar trifolii and Trifolium spp. related to geographic and phenological barriers. Additionally, we have shown that an effective symbiosis between strains of R. l. trifolii and clover was established despite the soil harbouring ineffective R. l. trifolii capable of nodulating the host. We termed this “selection” for effective symbiosis. This paper reports glasshouse-based experiments to validate and further explore this in situ selection phenomenon. The effect of cell density and strain ratio at the time of inoculation, as well as soil pH, were investigated on two hosts (Trifolium purpureum and Trifolium polymorphum) that were each exposed to one microsymbiont capable and one incapable of N₂ fixation. In co-inoculation experiments at a cell density of 10⁴ cells/mL, each host nodulated solely with its effective strain, even when this strain was outnumbered 100-fold by the ineffective strain. However, the selection process ceased when the effective strain was outnumbered 1000-fold. At higher basal cell concentrations of 10⁵–10⁸ cells/mL, selection for WSM1325 to form effective nodulation on T. purpureum was evident, but was significantly reduced as the ratio of ineffective cells in the inoculum increased above 4-fold. The results indicate that the selection mechanism is highly dependent on the basal rhizobial cell density. Soil pH did not significantly alter the process, and both strains grew at similar rates and formed nodules at similar rates. A preliminary investigation into the genetic backgrounds of WSM1325 and WSM2304 revealed that although their 16S rRNA sequences were identical, they have considerable differences in their symbiotic and chromosomal replicons through examination of atpD, GSII and nodD sequences.     

Influence of environmental conditions on biofilm formation by Hafnia alvei strains

Hafnia alvei is considered an opportunistic pathogen of animal and humans, affecting a wide range of homeothermic and poikilothermic hosts with different body temperatures. In this work, H. alvei strains isolated from different sources were studied with regard to their capacity to form biofilms under different environmental conditions. Strain, growth phase, temperature and culture media dependent changes of biofilm formation were semiquantitatively monitored using a microtiter plate method. Our study shows that all strains used could form biofilms in vitro, and that biofilm formation increases dramatically during growth at 25 degrees C but not at 37 degrees C, and decreases at both temperatures in presence of glucose. At 16 degrees C only one strain isolated from a lizard was able to form a dense biofilm showing that the ability to form biofilms in this species is regulated by environmental factors and is also strain specific.     

Analysis of the effect of the bovine adenosine triphosphate-binding cassette transporter G2 single nucleotide polymorphism Y581S on transcellular transport of veterinary drugs using new cell culture models

In commercial dairy production, the risk of drug residues and environmental pollutants in milk from ruminants has become an outstanding problem. One of the main determinants of active drug secretion into milk is the ATP-binding cassette transporter G2/breast cancer resistance protein (ABCG2/BCRP). It is located in several organs associated with drug absorption, metabolism, and excretion, and its expression is highly induced during lactation in the mammary gland of ruminants, mice, and humans. As a consequence, potential contamination of milk could expose suckling infants to xenotoxins. In cows, a SNP for this protein affecting quality and quantity of milk production has been described previously (Y581S). In this study, our main purpose was to determine whether this polymorphism has an effect on transcellular transport of veterinary drugs because this could alter substrate pharmacokinetics and milk residues. We stably expressed the wild-type bovine ABCG2 and the Y581S variant in Madin-Darby canine kidney epithelial cells (MDCKII) and MEF3.8 cell lines generating cell models in which the functionality of the bovine transporter could be addressed. Functional studies confirmed the greater functional activity in mitoxantrone accumulation assays for the Y581S variant with a greater relative V(MAX) value (P = 0.040) and showed for the first time that the Y581S variant presents greater transcellular transport of the model ABCG2 substrate nitrofurantoin (P = 0.024) and of 3 veterinary antibiotics, the fluoroquinolone agents enrofloxacin (P = 0.035), danofloxacin (P = 0.001), and difloxacin (P = 0.008), identified as new substrates of the bovine ABCG2. In addition, the inhibitory effect of the macrocyclic lactone ivermectin on the activity of wild-type bovine ABCG2 and the Y581S variant was also confirmed, showing a greater inhibitory potency on the wild-type protein at all the concentrations tested (5 μM, P = 0.017; 10 μM, P = 0.001; 25 μM, P = 0.008; and 50 μM, P = 0.003). Differential transport activity depending on the genotype together with the differential inhibition pattern might have clinical consequences, including changes in substrate pharmacokinetics (and subsequently pharmacodynamics) and more specifically, changes in secretion of ABCG2 substrates into milk, potentially implying important consequences to veterinary therapeutics.