Effects of long- or short-term exposure to a calf identified as persistently infected with bovine viral diarrhea virus on feedlot performance of freshly weaned, transport-stressed beef heifers

A single experiment with a completely randomized design was conducted to evaluate the effects of long- or short-term exposure to a calf identified as persistently infected with bovine viral diarrhea virus (PI-BVD) on feedlot performance and carcass characteristics of freshly weaned, transport-stressed beef heifers. Two hundred eighty-eight heifers that had been vaccinated for BVD before weaning and transport were processed and given a metaphylactic antibiotic treatment at arrival and were fed common receiving, growing, and finishing diets for a 215-d period. Treatments were designed to directly or adjacently expose the cattle to a PI-BVD heifer. Directly exposed treatments were 1) negative control with no PI-BVD calf exposure (control), 2) PI-BVD calf commingled in the pen for 60 h and then removed (short-term exposure), and 3) PI-BVD calf commingled in the pen for the duration of the study (long-term exposure); and spatially exposed treatments were 1) negative control with no PI-BVD calf exposure (adjacent pen control), 2) PI-BVD calf commingled in the adjacent pen for 60 h and then removed (adjacent pen short-term exposure), and 3) PI-BVD calf commingled in the adjacent pen for the duration of the study (adjacent pen long-term exposure). Exposure to a PI calf transiently (60 h) or for the duration of the feeding period (215 d) did not affect (P > or = 0.25) final BW compared with heifers that were not exposed. Neither period nor overall DMI was affected (P > or = 0.37) by PI-BVD calf exposure, and no differences (P > or = 0.44) were observed between short- and long-term exposed heifers in the direct or spatially exposed groups. Likewise, total trial ADG was not affected (P > or = 0.36) and overall efficiency of gain (P > or = 0.19) was unaffected by PI-BVD calf exposure in the direct or spatially exposed groups. The results from this study suggest that exposing previously vaccinated, freshly weaned, transport- stressed beef calves to a calf that is persistently infected with bovine viral diarrhea virus has little, if any, marked effects on health, performance, or carcass characteristics.     

The NS3 proteins of global strains of bluetongue virus evolve into regional topotypes through negative (purifying) selection

Comparison of the deduced amino acid sequences of the genes (S10) encoding the NS3 protein of 137 strains of bluetongue virus (BTV) from Africa, the Americas, Asia, Australia and the Mediterranean Basin showed limited variation. Common to all NS3 sequences were potential glycosylation sites at amino acid residues 63 and 150 and a cysteine at residue 137, whereas a cysteine at residue 181 was not conserved. The PPXY and PS/TAP late-domain motifs were conserved in all but three of the viruses. Phylogenetic analyses of these same sequences yielded two principal clades that grouped the viruses irrespective of their serotype or year of isolation (1900-2003). All viruses from Asia and Australia were grouped in one clade, whereas those from the other regions were present in both clades. Each clade segregated into distinct subclades that included viruses from single or multiple regions, and the S10 genes of some field viruses were identical to those of live-attenuated BTV vaccines. There was no evidence of positive selection on the S10 gene as assessed by reconstruction of ancestral codon states on the phylogeny, rather the functional constraints of the NS3 protein are expressed through substantial negative (purifying) selection.     

Identification and validation of housekeeping genes as internal control for gene expression in an intravenous LPS inflammation model in chickens

Real-time PCR has become a powerful tool for the detection of inflammatory parameters, including cytokines. Reference or housekeeping genes are used for the normalization of real-time RT-PCR results. In order to obtain reliable results, the stability of these housekeeping genes needs to be determined. In this study the stability of five genes, including beta-actin, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), hypoxanthine phophoribosyl-transferase (HPRT), ubiquitin (UB) and glucose-6-phosphate dehydrogenase (G6PDH), was determined in a lipopolysaccharide inflammation model in chickens. beta-Actin appeared to be the most stable single gene in our model. Because the use of a single gene for normalization can lead to relatively large errors, the use of the geometric mean of multiple reference genes or normalization factor is preferred. The most stable combination for gene expression analysis in this lipopolysaccharide inflammation model in chickens is G6PDH and UB, since their correlation coefficients were 0.953 and 0.969, respectively (BestKeeper) and an M value of 0.34 and a low V(2/3) value of 0.155 (geNorm) were obtained. The use of HPRT and GAPDH should be avoided. The stable housekeeping genes, G6PDH and UB together, can be used to normalize the expression of pro-inflammatory cytokines in a lipopolysaccharide inflammation model in chickens.     

Species of Staphylococcus isolated from animal infections

One hundred randomly selected clinical strains of staphylococci were identified by species using a commercial micromethod system. Eight species of staphylococci were identified. Staphylococcus intermedius was the most frequent (n = 74) species identified and accounted for 70/74 (94.6%) of the coagulase-positive strains and 70/79 (88.6%) of the total isolates from dogs. Other species identified, in order of their frequency, included S. epidermidis (8), S. aureus (7), S. simulans (4), S. sciuri (2), S. xylosus (2), S. hyicus (2) and S. saprophyticus (1). These results show that at least 8 different species of staphylococci can be recovered from animal infections and that coagulase-positive species such as S. intermedius may be more common than S. aureus. The relative significance of these other species in animal infections needs to be assessed.     

Bayesian inference for genetic parameter estimation on growth traits for Nelore cattle in Brazil,using the Gibbs sampler

This data set consisted of over 29 245 field records from 24 herds of registered Nelore cattle born between 1980 and 1993, with calves sires by 657 sires and 12 151 dams. The records were collected in south‐eastern and midwestern Brazil and animals were raised on pasture in a tropical climate. Three growth traits were included in these analyses: 205‐ (W205), 365‐ (W365) and 550‐day (W550) weight. The linear model included fixed effects for contemporary groups (herd‐year‐season‐sex) and age of dam at calving. The model also included random effects for direct genetic, maternal genetic and maternal permanent environmental (MPE) contributions to observations. The analyses were conducted using single‐trait and multiple‐trait animal models. Variance and covariance components were estimated by restricted maximum likelihood (REML) using a derivative‐free algorithm (DFREML) for multiple traits (MTDFREML). Bayesian inference was obtained by a multiple trait Gibbs sampling algorithm (GS) for (co)variance component inference in animal models (MTGSAM). Three different sets of prior distributions for the (co)variance components were used: flat, symmetric, and sharp. The shape parameters (ν) were 0, 5 and 9, respectively. The results suggested that the shape of the prior distributions did not affect the estimates of (co)variance components. From the REML analyses, for all traits, direct heritabilities obtained from single trait analyses were smaller than those obtained from bivariate analyses and by the GS method. Estimates of genetic correlations between direct and maternal effects obtained using REML were positive but very low, indicating that genetic selection programs should consider both components jointly. GS produced similar but slightly higher estimates of genetic parameters than REML, however, the greater robustness of GS makes it the method of choice for many applications.     

Cattle Infected with Bovine Leukaemia Virus may not only Develop Persistent B‐cell Lymphocytosis but also Persistent B‐cell Lymphopenia

We investigated the distribution of B and T cells in the peripheral blood of haematologically inconspicuous (non‐persistent lymphocytotic, PL^?) cattle infected with the bovine leukaemia virus (BLV). Flow cytometric data were obtained from six PL^? cattle and compared with six age‐matched animals with persistent lymphocytosis (PL⁺) and five non‐infected healthy controls (BLV^?). In the PL^? group, the percentage and number of surface immunoglobulin‐positive (sIg⁺) B cells were significantly reduced. Whereas in BLV^? cattle, about 40% of the peripheral blood lymphocytes (PBL) were sIg⁺ and 24% were sIgM⁺ B cells. In the PL^? group, less than 20% of the PBL were sIg⁺ and sIgM⁺ B cells. Only 5% of the PBL co‐expressed sIgM⁺ and CD5⁺ versus 16% in BLV^?. This decrease was persistent over 3 years and predominantly affected: (i) B cells that did not express sIgM; (ii) sIgM⁺ B cells co‐expressing CD5 and CD11b; and (iii) equally both λ‐ and κ‐type light chain B‐cell subpopulations. In contrast, the number of all circulating lymphocytes, CD5^? and CD11b^? sIgM⁺ B cells and CD2⁺ T cells did not differ. In PL⁺ animals, about 75% of the PBL were sIgM⁺CD5⁺ B cells. These cells were of polyclonal origin, as light chains of the λ‐ and κ‐type were expressed in a ratio of 4:1 (57.7% of PBL λ⁺, 14% κ⁺) as in BLV^? animals (33.6% of PBL λ⁺, 8.7% κ⁺). In PL⁺ cattle the absolute number of B‐cells and, therefore, their relative percentage is significantly increased. For this reason, even in case of absolutely increased T‐cell numbers, the relative percentage of T‐cells could be lower than in normal controls. The cause for the observed B cell decrease in PL^? cattle is unknown, but it can be assumed that cytotoxic T cells are involved in this B‐cell lymphopenia.