Influence of 17-α-Methyltestosterone on Red Tilapia Under Two Thermal Regimes

Fingerling red tilapia ( Oreochromis mossambicus ± O. niloticus ) were orally administered 17-α-methyltestosterone (MT) under a warmwater (27.0 ± 0.5 C) and coolwater (21.5 ± 0.5 C) thermal regime. In the warmwater experiment, fish received either 0, 1, 5, 10, 30, 60, or 100 mg MT/kg feed for 75 days. In the coolwater experiment, fish received 0, 10, or 60 mg MT/kg feed for 75 days followed by a 34 day withdrawal period. After 75 days, fish receiving 60 mg MT/kg feed (best treatment) in the warmwater and coolwater experiments exhibited significantly higher growth rates than controls by 35.3 and 45.8%, respectively. Likewise, feed conversion among groups receiving 60 mg MT/kg feed in the warmwater and coolwater experiments were significantly better than the controls (1.14 versus 1.30 and 1.44 versus 1.77, respectively). During the withdrawal period, no significant differences in growth rates or feed conversion were observed between the control and treatment groups. MT treatment significantly affected the body composition (whole body and empty carcass) of the red tilapia in both experiments, elevating percent moisture and protein values, but depressing percent fat values. Results demonstrated that incorporation of MT into fingerling diets offers potential for extending the period when tilapias actively feed and grow in temperate climates.     

Contribution of propylene glycol-induced Heinz body formation to anemia in cats

Propylene glycol (PG) is a common preservative and source of synthetic carbohydrates in soft-moist pet foods. Propylene glycol was fed to cats for 5 weeks at concentrations found in commercial diets (1.6 g/kg of body weight; 12% of diet on a dry-weight basis) and for 3 weeks at concentrations exceeding usual intake (8 g/kg; 41% of diet). There was a dose-dependent increase in Heinz body percentage to 28% in cats fed the low dose of PG and to 92% in cats fed the high dose. Erythrocyte half-life, measured using [14C]-cyanate hemoglobin (Hb), decreased significantly (P less than 0.05) by 18.8% and 60% in cats fed the low and high PG doses, respectively. The PCV in cats fed the low dose was unaffected, whereas cats fed the high dose had a mean (+/- SEM) decrease in PCV from 33.5 +/- 1.05% to 26.3 +/- 1.45%, accompanied by punctate reticulocytosis and bone marrow erythroid hyperplasia. A dose-dependent increase in iron pigment was found in the liver and spleen of all cats. In cats fed the low dose of PG, erythrocyte reduced glutathione concentration actually increased from 7.02 +/- 0.56 to 9.74 +/- 0.69 mumol/g of Hb, but decreased to 2.96 +/- 0.27 mumol/g of Hb in cats fed the high dose. There was no significant increase in methemoglobin concentration. These results indicated that PG cannot be considered innocuous even at concentrations consumed by cats eating commercial diets. Heinz body-induced acceleration of RBC destruction develops in a dose-dependent manner, so that cats with greater food intake, ie, lactating queens and nursing kittens, are at greater risk for development of PG-induced Heinz body hemolytic anemia.     

Pocono mesic till barrens in retreat: topography,fire and forest contagion effects

The Pocono mesic till barrens (PMTB) are a unique assemblage of fire-maintained shrub communities that support numerous rare species. Historically these barrens covered a large area in the vicinity of Long Pond, Pennsylvania, USA. However, due largely to regional fire suppression instituted in the early 1960s, over 70% of the area covered by barrens succeeded to fire-intolerant forest that does not support the rare species. We investigated the influence of forest proximity on barrens succession across three geomorphic types during periods of high fire frequency and fire suppression, testing the hypothesis that forest processes such as seed rain, shading, and detrital enrichment of soils enhances barrens succession through a contagion effect. Evidence of a forest contagion effect should be shown by increased rates of barrens succession with increasing proximity to the nearest forest edge. In order to detect a forest contagion effect, barrens persistence and barrens succession were modeled in proximity zones of 0-50 m, 50-100 m, 100-200 m, and greater than 200 m from the nearest forest edge. We used existing GIS data layers for fire, geomorphology, and vegetation distribution in 1938, 1963, and 1992. The layers were modified and overlain using ArcView software to determine persistence and succession rates for each unique combination of layers in each proximity zone from 1938 to 1963 (pre-fire suppression) and 1963 to 1992 (post-fire suppression). ANCOVA results indicate that proximity to the nearest forest edge significantly affected barrens persistence rates in both time periods, but succession rates were significantly affected in 1938 to 1963 only. Twenty-eight percent of the 1938 barrens succeeded to forest by 1963; 56% of the 1963 barrens became forest by 1992. Results support previous findings that barrens persistence is enhanced by increased fire frequency, and that barrens persist longer where they overlie flat glacial till than on other geomorphology types.     

Effect of hay type on cecal and fecal microbiome and fermentation parameters in horses

The effect of hay type on the microbiome of the equine gastrointestinal tract is relatively unexplored. Our objective was to characterize the cecal and fecal microbiome of mature horses consuming alfalfa or Smooth Bromegrass (brome) hay. Six cecally cannulated horses were used in a split-plot design run as a crossover in two periods. The whole plot treatment was ad libitum access to brome or alfalfa hay fed over two 21-d acclimation periods with subplots of sampling location (cecum and rectum) and sampling hour. Each acclimation period was followed by a 24-h collection period where cecal and fecal samples were collected every 3 h for analysis of pH and volatile fatty acids (VFA). Fecal and cecal samples were pooled and sent to a commercial lab (MR DNA, Shallowater, TX) for the amplification of the V4 region of the 16S rRNA gene and sequenced using Illumina HiSeq. The main effects of hay on VFA, pH, and taxonomic abundances were analyzed using the MIXED procedure of SAS 9.4 with fixed effects of hay, hour, location, period, and all possible interactions and random effect of horse. Alpha and beta diversities were analyzed using the R Dame package. Horses fed alfalfa had greater fecal than cecal pH (P ≤ 0.05), whereas horses fed brome had greater cecal than fecal pH (P ≤ 0.05). Regardless of hay type, total VFA concentrations were greater (P ≤ 0.05) in the cecum than in feces, and alfalfa resulted in greater (P ≤ 0.05) VFA concentrations than brome in both sampling locations. Alpha diversity was greater (P ≤ 0.05) in fecal compared with cecal samples. Microbial community structure within each sampling location and hay type differed from one another (P ≤ 0.05). Bacteroidetes were greater (P ≤ 0.05) in the cecum compared with the rectum, regardless of hay type. Firmicutes and Firmicutes:Bacteroidetes were greater (P ≤ 0.05) in the feces compared with cecal samples of alfalfa-fed horses. In all, fermentation parameters and bacterial abundances were impacted by hay type and sampling location in the hindgut.     

Influence of amount and frequency of protein supplementation to ruminants consuming low-quality cool-season forages: efficiency of nitrogen utilization in lambs and performance of gestating beef cows

We evaluated the influence of amount and crude protein (CP) supplementation frequency (SF) on nitrogen (N) use by wethers and the performance of late-gestation beef cows. In exp. 1, seven Western whiteface wethers (31.8 ± 1.4 kg) were used in an incomplete 7 × 4 Latin square to evaluate intake and N use. Wethers received one of the seven treatments in a 2 × 3 factorial design containing two levels of supplemental soybean meal offered at a rate of 100% (F) or 50% (H; 50% of F) of the estimated CP requirement daily, once every 5, or once every 10 d, plus a non-supplemented control (CON). Low-quality cool-season forage (4.9 % CP; dry matter [DM] basis) was provided daily for ad libitum intake. Experimental periods lasted 30 d. In exp. 2, 84 Angus × Hereford cows (560 ± 35 kg) were stratified by age, body condition score (BCS), and expected calving date and allocated to 1 of the 21 feedlot pens (three pens per treatment). Pens were randomly assigned to receive the same treatments as in exp. 1 and cows had free access to low-quality cool-season forage (2.9% CP; DM basis). Cow body weight (BW) and BCS were measured every 14 d until calving and within 24 h after calving. In exp. 1, supplementation did not alter total DM and organic matter (OM) intake (P ≥ 0.26), but both parameters linearly decreased as SF decreased (P = 0.02). Supplementation increased DM, OM, and neutral detergent fiber (NDF) digestibility (P ≤ 0.02). Additionally, F feeding linearly increased DM, OM, and NDF digestibility as SF decreased (P ≤ 0.04). Digestibility of N, N balance, and digested N retained were greater with supplementation (P < 0.01), and N digestibility linearly increased as SF decreased (P = 0.01). Mean plasma urea-N concentration was not only greater (P < 0.01) for supplemented vs. CON wethers but also greater (P = 0.03) for F vs. H. In exp. 2, pre-calving BCS change was greater (P = 0.03) for supplemented cows. A linear effect of SF × supplementation rate for pre-calving BCS change was noted (P = 0.05), as F-supplemented cows lost more BCS compared with H as SF decreased. When considering supplementation intervals greater than 5 d, reducing the quantity of supplement provided, compared with daily supplementation, may be a feasible management strategy to maintain acceptable nutrient use and animal performance while reducing supplement and labor costs.     

TRUNCATION ARTIFACT IN MAGNETIC RESONANCE IMAGES OF THE CANINE SPINAL CORD

The truncation artifact in magnetic resonance (MR) images is a line of abnormal signal intensity that occurs parallel to an interface between tissues of markedly different signal intensity. In order to demonstrate the truncation artifact in sagittal images of the canine spinal cord and the effect of changing spatial resolution, we conducted an experimental in vitro study. A section of fixed canine spinal cord was imaged using a 1.5T magnet. Spatial resolution was increased by increasing the acquisition matrix and reconstruction matrix, producing series of T2‐weighted (T2w) images with the following pixel sizes: A, 1.6 (vertical) × 2.2 mm² (horizontal); B, 1.2 × 1.7 mm²; C, 0.8 × 1.1 mm²; D, 0.4 × 0. 6 mm². Plots of mean pixel value across the cord showed variations in signal intensity compatible with truncation artifact, which appeared as a single, wide central hyperintense zone in low‐resolution images and as multiple narrower zones in high spatial resolution images. Even in images obtained using the highest spatial resolution available for the MR system, the edge of the spinal cord was not accurately defined and the central canal was not visible. The experiment was repeated using an unfixed spinal cord specimen with focal compression applied to mimic a pathologic lesion. Slight hyperintensity was observed within the spinal cord at the site of compression although the cord was normal histologically. Results of this study suggest that caution should be applied when interpreting hyperintensity affecting the spinal cord in T2w sagittal images of clinical patients because of the possibility that the abnormal signal could represent a truncation artifact.     

Achromatopsia in three sibling Labrador Retrievers in the UK

Achromatopsia was identified in three Labrador Retriever littermates. The dogs demonstrated day blindness, negotiating obstacles under low‐light conditions, but apparently blind when outdoors. One of the dogs presented with immature bilateral diffuse posterior cortical cataracts and clinical signs of day blindness became apparent following cataract extraction surgery. Electroretinography demonstrated an absence of a cone photoreceptor response to a bright stimulus and a flicker response of 30 Hz in all three dogs. No fundic lesions have been apparent ophthalmoscopically in any of the dogs as the initial presentation of each case. No abnormalities were detected with DNA screening for known mutations of the CNGB3 gene in any of the dogs.