Simulation model of within-herd transmission of bovine tuberculosis in Argentine dairy herds

Transmission of bovine tuberculosis was quantified in three dairy herds located in south Santa Fe Province, Argentina. Using estimates of Mycobacterium bovis transmission (β) and a Reed–Frost simulation model, the prevalence of tuberculosis infection in the study herds over time was investigated. The Reed–Frost model was modified by incorporating randomness in both β and the incubation period () of M. bovis. The mean estimated herd β was 2.2 infective contacts per year and did not differ significantly between the study herds. Modeling as Poisson distributed (mean 24 months) best fit the observed prevalences. Infection was predicted by the model either to spread quickly (<10 years) within a herd and reach a high prevalence (>50%), or to persist at a low prevalence (<5–10%). The model was robust, predictions were realistic and the mean β estimated was consistent with previous studies of bovine tuberculosis.     

Survival of Mycobacterium avium subsp. paratuberculosis in bovine monocyte-derived macrophages is not affected by host infection status but depends on the infecting bacterial genotype

In this study we investigated the ability of different Mycobacterium avium subsp. paratuberculosis (M. paratuberculosis) strains to survive in bovine monocyte-derived macrophages (MDMs) of cows naturally infected with M. paratuberculosis and control cows. We tested the hypotheses that infection status of cows affects macrophage killing ability and that survival of M. paratuberculosis in macrophages is dependent on the strain. Peripheral blood mononuclear cells (PBMC) were obtained from Johne's disease-positive (n = 3) and age and stage of lactation matched Johne's disease-negative (n = 3) multiparious cows. Following differentiation, MDMs were challenged in vitro with four M. paratuberculosis strains of different host specificity (cattle and sheep). Two hours and 2, 4, and 7 days after infection, ingestion, and intracellular survival of M. paratuberculosis strains were determined by fluorescence microscopy. There was no effect of the origin of MDMs (Johne's disease-positive or control animals) on phagocytosis, survival of bacteria, or macrophage survival. In contrast, important strain differences were observed. These findings suggest that some M. paratuberculosis strains interfere more successfully than others with the ability of macrophages to kill intracellular pathogens which may make it important to include strain typing when designing control programs.     

分枝杆菌分型三重PCR检测方法的建立及应用

本研究旨在建立一种快速鉴定分枝杆菌的三重PCR方法,并比较分析其在临床检测中的可靠性。根据已发表的结核分枝杆菌、牛分枝杆菌和非洲分枝杆菌rv 3036c基因,结核分枝杆菌rv 1970f基因(RD7)和牛分枝杆菌pncA基因的序列,改造并设计合成了3对特异性扩增引物,建立了一种能对分枝杆菌样品进行初步鉴定的三重PCR方法。结果显示该方法可针对rv 3036c、rv 1970f和pncA基因分别扩增出大小为500、125和249 bp的目的片段,能特异性检测出结核分枝杆菌(500和125 bp两条带)和牛分枝杆菌(500和249 bp两条带),并可将结核分枝杆菌、牛分枝杆菌与其他分枝杆菌加以区分。本方法的检测灵敏度为50 pg/μL模板基因组DNA。对86株抗酸染色阳性菌进行三重PCR鉴定,鉴定结果与细菌16S rDNA和ITS序列测定结果一致,检测准确度为100%,优于生长特征和生化试验鉴定。     

Serological reactivity to Mycobacterium bovis protein antigens in cattle.

The serological response to 12 purified Mycobacterium bovis antigens were examined in an ELISA assay. These antigens included the majority of M. bovis protein antigens described to date and in most cases they were very similar to the M. tuberculosis antigens of the same molecular mass.

The purified antigens were tested against sera from M. bovis infected cattle, M. bovis culture-negative cattle from infected herds and animals infected with related microorganisms, mainly other mycobacterial species. All the antigens gave strong reactions with at least some sera from the M. bovis infected group and showed cross-reactivity with some of the sera from the other two groups. The antigen with the highest specificity reacted strongly with only 60% of the M. bovis infected sera. Antigens that reacted with most or all of the M. bovis infected sera also gave the highest cross-reactivity with sera from the other two groups. These results indicate that a serological test based on any one or a combination of these antigens, without removal of the cross-reacting epitopes, would be unsatisfactory.     

Efficacy of spheroplastic and cell-wall competent vaccines for Mycobacterium avium subsp. paratuberculosis in experimentally-challenged baby goats

A Mycobacterium avium subspecies paratuberculosis (MAP) vaccine that reduced the incidence of clinical disease or reduced fecal shedding of MAP would aid control of Johne's disease (JD). The objective of the present study was to evaluate the efficacy of four MAP vaccine combinations, including cell-wall competent (CWC) alum adjuvant, CWC-QS21 adjuvant, cell-wall deficient (CWD) alum adjuvant and CWD-QS21 adjuvant vaccines. Eighty baby goats were vaccinated at 1 and 4 weeks of age with one of these vaccines or a sham control vaccine consisting of alum adjuvant. Kids were challenged orally with approximately 6.0 × 10⁹ organisms in four divided doses of 1.5 × 10⁹ organisms using a goat isolate of MAP. Vaccinated challenged and challenged control groups had 10 and 6 kids per group, respectively. Half of the kids within each group were necropsied at either 6 or 9 months post-challenge. Gross and microscopic lesions and relative number of acid-fast bacilli were evaluated and scored at necropsy. Results indicated all challenged kids had some lesions compatible with JD suggesting none of the vaccines prevented infection. Three vaccines (CWC-alum, CWC-QS21 and CWD-QS21) reduced lesion scores by 46–51% at 9 months. CWD-alum vaccine resulted in a more severe (+33.5%) lesion score than sham-vaccinated challenged control. Lesion scores were greater at 9 months than at 6 months post-challenge in the sham-vaccinated challenged group and CWD-alum vaccinated group, while lesion scores were generally stable with remaining vaccines. Mean fecal CFU/g were significantly different across time from challenge to 9-month necropsy (p = 0.043) and the CWC-QS21 vaccine group had a marked reduction in fecal CFU/g at all time points post-challenge. A reduction in MAP CFU/g was also detected in necropsy tissues from kids given the CWC-alum, CWC-QS21 and CWD-QS21 vaccines, and increased CFU/g were detected in tissues from kids given the CWD-alum vaccine. Immunological tests evaluated included, humoral response evaluation by AGID, ELISA and Western blot, and cell mediated response by comparative PPD skin testing (M. avium, Old Johnin, M. bovis and Lot 2 Johnin PPD's), and production of MAP induced γ-interferon. Vaccination also resulted in false-positive PPD skin test reactions for M. avium PPD, Old Johnin PPD and γ-interferon tests. When a 2-mm cutoff above normal skin thickness was used to define positive skin test reactions, false-positive reactions for M. bovis were detected in only 2 of 32 kids given a vaccine with QS21 adjuvant.     

Establishment and Application of Mycobacterium Typing Triple PCR Detection Method

This study was aimed to establish a triple PCR method to rapidly identify Mycobacterium species, and evaluate its testing reliability.Three pairs of primer that were respectively specific to rv 3036c, rv 1970f and pncA genes of Mycobacterium were designed to establish a triple PCR for preliminary identification of Mycobacterium tuberculosis(M.tuberculosis), Mycobacterium bovis(M.bovis) and other Mycobacterium spp.PCR products were the expected sizes of 500(rv3036c), 125(rv1970f) and 249 bp(pncA), and contained two DNA bands(500 and 125 bp) with M.tuberculosis DNA template, two DNA bands(500 and 249 bp) with M.bovis DNA template.No band or non-specific band appeared with Mycobacterium spp.except M.tuberculosis and M.bovis DNA templates.The sensitivity of the triple PCR was calculated to 50 pg/μL template of genomic DNA.86 acid-fast bacteria were detected by the triple PCR, 16S rDNA and ITS gene sequencing, growth test and biochemical test, and the results were consistent between triple PCR and 16S rDNA and ITS gene sequencing.The detecting accuracy of triple PCR was 100%, and higher than growth test and biochemical test.     

Molecular fingerprinting confirms extensive cow-to-cow intra-herd transmission of a single Mycobacterium bovis strain

In this study we have characterized M. bovis isolates from a herd of cattle in Uvalde, Texas in which 52 of the 193 animals selected at random in 1994 from a herd of 331 were caudal fold skin-test positive. Thirty-two of 52 skin-test positive cattle had gross lesions at slaughter, and isolations of M. bovis were made from 29 animals. The herd was comprised of Red Devon cattle purchased between 1978 and 1980 (n = 26) and breeding bulls (n = 3) introduced at later times, and all were tuberculosis test negative at the time of purchase. Other animals were natural additions (offspring) of these cattle. One additional animal, a Holstein present on the ranch at the time of purchase in 1976, was retained to nurse orphaned and weak calves. Using several molecular fingerprinting techniques we have verified a clonal relationship among the M. bovis isolates consistent with infection originating with a single strain. The molecular fingerprint patterns demonstrate the stability of the profiles despite persistence and spread of the organism within the herd for two decades and confirms their use in epidemiological tracing.     

Intrauterine infusion of BQ-610, an endothelin type A receptor antagonist, delays luteolysis in dairy heifers

Three separate in vivo experiments were conducted to evaluate the putative role of endothelin-1 (ET-1) during luteal regression in heifers. In Experiment 1, a single intraluteal injection of 500 μg BQ-610 [(N,N-hexamethylene) carbamoyl-Leu-d-Trp (CHO)-d-Trp], a highly specific endothelin A (ET_A) receptor antagonist, did not diminish the decline in plasma progesterone following a single exogenous injection of 25 mg prostaglandin F2 alpha (PGF₂) administered at midcycle of the estrous cycle. In Experiment 2, six intrauterine infusions of 500 μg BQ-610 given every 12 h on days 16–18 delayed spontaneous luteolysis, as evidenced by an extended elevation (P = 0.054) of plasma progesterone concentration. In Experiment 3, heifers were administered six intrauterine infusions of BQ-610 or saline on days 16–19, and peripheral blood samples were collected from day 11 to 16 (before infusion), hourly on days 16–19 (during infusion), and on days 20–25 (after infusion). BQ-610 treated heifers had markedly higher (P < 0.0001) levels of plasma progesterone compared with saline controls, and this effect was most notable during the infusion period (treatment by period interaction; P ≤ 0.05). Heifers infused with BQ-610 also had higher progesterone levels on day 21 (treatment by time interaction; P ≤ 0.05). Mean plasma concentrations of 13,14-dihydro-15-keto-PGF₂ (PGFM), the primary metabolite of PGF₂, were measured in the samples collected hourly and were not different (P ≥ 0.05) between treatments. These results indicate that the in vivo antagonism of the ET_A receptor can delay functional luteolysis, and supports the theory that ET-1 regulates luteal function in ruminants.     

Correlation between carcass conformation and fat cover degree, and muscle fatty acid profile of yearling bulls depending on breed and mh-genotype

The objective was to study the relationships between the actual European beef carcass classification scale, which classifies carcasses with regard to conformation and degree of fat cover scores, and muscle fat quality, depending on breed and mh-genotype. For this purpose samples from 100 yearling bulls from “Asturiana de los Valles” (24 AV(mh/mh), 26 AV(mh/+), 25 AV (+/+)) and “Asturiana de la Montaña” (25 AM) were analysed. The results of the study showed that breed or genotype affect carcass measurement scores and muscle fatty acid profile through its important effect on animal overall fatness. Homozygous double-muscled animals produced carcasses with high conformation and low intramuscular (IM) fat content. While early-maturing and rustic AM animals produced low carcass yield and high IM fat content. The other genotypes (mh/+, +/+) showed, in general, intermediate characteristics. Referring to correlations, carcass conformation was negatively related to saturated (SFA) (r = − 0.69, P < 0.001) and monounsaturated fatty acid (MUFA) (r = − 0.69, P < 0.001) groups, and positively to polyunsaturated (PUFA) (r = 0.72), n-6 (r = 0.72), n-3 (r = 0.71) and unsaturated fatty acid (UFA) (r = 0.69) groups, being all of them significant (P < 0.001). However, carcass degree of fat cover was positively related to SFA (r = 0.53, P < 0.001) and MUFA (r = 0.62, P < 0.001), and negatively to PUFA (r = − 0.61), n-6 (r = − 0.60), n-3 (r = − 0.62) and UFA (r = − 0.53) groups, being all of them significant. Moreover, simple and low-cost prediction equations were calculated for a rapid and sufficiently accurate fatty acid group (SFA, MUFA, PUFA, n-6, n-3, UFA) estimation (R² > 0.46, P < 0.001). In general, meat obtained from double-muscled animals display a more appropriate IM fatty acid profile from the nutritional point of view according to actual recommendations, but it could happen the disability of these lean animals to deposit sufficient IM fat to ensure consumer overall liking or acceptability.     

Changes in hormones, growth factor and lipid metabolism in finishing pigs fed betaine

An experiment was conducted to investigate the effect of dietary betaine supplementation on carcass characteristics, hormones, growth factor and lipid metabolism in finishing pigs. Forty-eight crossbred barrows and gilts (Seghers × Seghers × Duroc) weighing about 55 kg were divided into two groups, each with three replicates of eight pigs (four barrows and four gilts) per replicate, and fed corn–soybean meal basal diets supplemented with 0 and 0.125% betaine for 42 days. At trial termination, two pigs (one barrow and one gilt) weighing about 90 kg were selected from each replicate and slaughtered for analyses. The results showed that betaine increased carcass lean percentage and longissimus muscle area by 5.19% (P < 0.01) and 17.85% (P < 0.01), respectively, and decreased carcass fat percentage and average backfat thickness by 13.07% (P < 0.01) and 10.30% (P < 0.05), respectively. Serum growth hormone, insulin-like growth factor I, free triiodothyronine, free thyroxine and insulin levels in pigs fed betaine were elevated by 45.61% (P < 0.01), 55.50% (P < 0.01), 57.95% (P < 0.01), 51.80% (P < 0.01) and 42.34% (P < 0.05), respectively. Fatty acid synthase activity in the 10th rib subcutaneous adipose tissue was decreased by 24.35% (P < 0.05) with betaine supplementation, whereas hormone-sensitive lipase activity was significantly increased (P < 0.05). Meanwhile, serum free fatty acids concentration in betaine-fed pigs was 25.75% higher compared to controls (P < 0.01). The study suggested that betaine could induce changes in hormones and growth factor in finishing pigs, and therefore could inhibit fat synthesis through reducing lipogenic enzymes activities and promote fat degradation by increasing hormone-sensitive lipase activity, with a resultant decrease in adipose tissue mass and improvement in carcass characteristics.     

Mapping of IS6110 insertion sites in Mycobacterium bovis isolates in relation to adaptation from the animal to human host

The physiological role and impact of IS6110 insertions on the biology of Mycobacterium tuberculosis complex is not well understood. Insertion of IS6110 in coding regions can cause loss of gene activity, while homologous recombination between two copies of IS6110 can result in the deletion of genes or in rearrangement of genomic regions involved. In addition to these genomic changes, IS6110 can also activate flanking genes through acting as a mobile promoter.

In order to determine the possible role of IS6110 transposition in the adaptation to humans, we selected Mycobacterium bovis isolates from endogenous reactivation cases in elderly people in The Netherlands. The human isolates contained higher number of IS6110 copies in comparison to the bovine M. bovis strains. These additional integration sites of IS6110 were sequenced and analyzed. From 12 of such IS6110 insertion sites, 6 loci were located in the intergenic regions, and 6 other occurred within coding regions. IS6110 was inserted in a position where it might serve as a promoter in two cases. We conclude that IS6110 transpositions in M. bovis may be a driving force in the adaptation from the animal to the human host.     

Tuberculosis as a zoonosis from a veterinary perspective

Tuberculosis is an important disease among many zoonoses, because both Mycobacterium tuberculosis and Mycobacterium bovis, which are the major causes of tuberculosis, are highly pathogenic, infect many animal species and thus are likely to be the source of infection in humans. In particular, monkeys are highly susceptible to these bacteria and are important spreaders. Recently, two outbreaks of M. tuberculosis occurred in four different kinds of monkeys and humans were also infected with the disease in Japan. In zoos, tuberculosis was reported not only in monkeys, but also in several different kinds of animals, including elephants. Pets such as dogs and cats are believed to be generally less susceptible to M. tuberculosis, but in this article we introduce a case of infection from man to dog by close contact. Japan is one of the few countries that have been able to control M. bovis infection. In other countries, however, cases of bovine tuberculosis and human M. bovis infection have been reported, and thus further attention is still required in the future.     

The effect of dietary protein supply on carcass composition, size of organs, muscle properties and meat quality of pigs

This study investigated the effect of dietary protein supply on growth performance, carcass composition and size of organs in pigs slaughtered at the age of 165 ± 2 d. In addition, we analysed muscle fibre properties and glycolytic potential of light muscles longissimus lumborum (LD), semimembranosus (SM), and gluteus superficialis (GS), and dark muscles infraspinatus (IS) and masseter (M) of 20 gilts and 20 barrows. Of these pigs, 16 were Finnish Landrace, 16 were Finnish Yorkshire, and 8 were crosses of these breeds. The pigs were fed low-or high-protein diets formulated to contain 6.0 and 9.5 g of apparent ileal digestible lysine/feed unit (1 fu = 9.3 MJ NE), respectively. The pigs were fed according to a restricted weight-based feeding scale (13–30 MJ NE/d). Lean meat, fat, bones, and skin of the carcasses as well as organs were dissected and weighed. The pH value was measured 45 min post mortem from LD, and 24 h post mortem from LD, SM and GS. Drip loss, lightness (L) and redness (a) were measured from LD, SM and GS. Pigs with a low-protein supply showed a lower growth rate (P < 0.01), carcass weight (P < 0.01), and carcass lean meat content (P < 0.01), but higher carcass fat content (P < 0.01) and smaller kidneys (P < 0.01) than did pigs with a high-protein supply. In LD, the differences in cross-sectional areas in all muscle fibre types (P < 0.05) between the feeding groups were significant; in GS we found significant differences in cross-sectional areas of type IIA and type IIB (P < 0.05), while in SM we found no differences in muscle fibre cross-sectional areas between the feeding groups (P > 0.05). We found no such differences in the dark muscles studied. We also took into account the effect of both the breed and sex on the studied properties. The low-protein diet increased glycolytic potential in porcine LD and SM, and decreased the pH value measured 45 min post mortem from LD. The dietary protein supply affected no other meat quality traits studied. A more rapid drop in pH in LD resulted in a lighter and less red meat with higher drip loss.     

Quantification of the spread of Mycoplasma hyopneumoniae in nursery pigs using transmission experiments

Mycoplasma hyopneumoniae (M. hyopneumoniae) is present in almost all swine herds worldwide, but transmission of the pathogen through herds is not yet fully clarified. The aim of this study, performed in 2003, was to investigate and to quantify the transmission of M. hyopneumoniae under experimental conditions by means of an adjusted reproduction ratio (R_n). This R_n-value, calculated according to the final size method, expresses the mean number of secondary infections due to one typical infectious piglet during the nursery period. The period lasted from 4 to 10 weeks of age, corresponding with the nursery period used in most European production systems. Additionally, a comparison was made between transmissions of highly virulent and low virulent isolates.

Forty-eight weaned piglets, free of M. hyopneumoniae, were housed in six separate pens. During 6 weeks, two animals experimentally infected with M. hyopneumoniae were housed together with six susceptible piglets. At the end of the study, the number of contact-infected animals was determined by the use of nPCR on bronchoalveolar lavage fluid. The R_n-values of the highly virulent and the low virulent isolates were estimated to be 1.47 (0.68–5.38) and 0.85 (0.33–3.39), respectively. No significant difference between the groups was found (P = 0.53). The overall R_n was estimated to be 1.16 (0.94–4.08). Under the present experimental conditions, the transmission of M. hyopneumoniae, assessed for the first time by a reproduction ratio, shows that one piglet infected before weaning will infect on average one penmate during the nursery phase.     

The effects of increasing the level of dietary wormwood (Artemisia montana Pampan) on intake, digestibility, N balance and ruminal fermentation characteristics in sheep

This study investigated the effect of replacing concentrates with dry wormwood (Artemisia montana) on the performance of sheep. Four Corriedale × Polwarth sheep (41.3 ± 1.3 kg) were fed diets with an 8 : 2 straw to supplement ratio, for four, consecutive 16 d periods (10 d adaptation, 6 d collection) in a 4 × 4 Latin square design. Supplements were made by substituting 0 (Control), 30 (LW), 50 (MW) or 100 (HW) g/kg DM of concentrate (15.6% CP, 72.1% of TDN) with dried, ground wormwood. Ruminal pH, NH₃–N and volatile fatty acids (VFA) were measured on d 6 of collection. Ether extract (EE) intake was linearly decreased (P < 0.001) with increasing wormwood inclusion, otherwise intake was unaffected. The Control diet had lower (P < 0.05) DM and CP digestibility than LW and MW diets and lower EE digestibility than the LW diet. Retained N (P < 0.05) and microbial N yield (P < 0.01) linearly increased with dietary wormwood level, but efficiency of microbial N synthesis linearly decreased (P < 0.001). Mean concentrations of rumen NH₃–N, total VFA and propionic acid were quadratically increased (P < 0.05) by increasing wormwood inclusion. Replacing concentrates with 30–50 g/kg DM of wormwood increased N retention, microbial N yield and EE digestibility.     

Management factors associated with Babesia bovis seroprevalence in cattle from eastern Yucatán, Mexico.

The effect of management on the seroprevalence of Babesia bovis was studied in 399 Bos indicus cattle 1–2 years old from 92 farms in the eastern Yucatán, México. The management factors studied were: farm-type, production system, herd size, farm size, stocking density, vector control, dipping interval, type of dipping, type of acaricide and cattle introduction to the farm. A cross-sectional study was carried out (2-stage cluster sampling). The number of serum samples was proportionally distributed according to the number of farms in the nine locations of eastern Yucatán, México (399 animals from 92 farms). Antibody activity to B. bovis was tested using an indirect ELISA. The farms with a seroprevalence ≤75% were considered as cases and those with seroprevalence >75% were considered as controls. The variables with p ≤ 0.20 were included in fixed effects logistic regression. The seroprevalence of the zone was 73.8% (66.3–81.3%). The following risk factors were found: Stocking density (<1 head/ha, OR = 4.04, CI (OR) = 1.20–13.62) and dipping interval (>60 days, OR = 5.07 CI (OR) = 1.26–20.48).     

Evaluation of MPB70, bovine PPD and lipoarabinomannan as antigens in ELISA for the serodiagnosis of bovine tuberculosis

The performance of the secretory protein MPB70 of Mycobacterium bovis, bovine PPD, and lipoarabinomannan (LAM) were evaluated as antigens in ELISA for detection of tuberculosis (TB) infected cattle. Sera were from 120 M. bovis infected cattle and 223 cattle from a TB free herd. ELISA results were analyzed using receiver operating characteristic (ROC) curves in relation to culture results. The areas under the three ROC curves were 71 ± 49% SE (MPB70), 71 ± 27% SE (bovine PPD), and 56 ± 4% SE (LAM).     

The effect of dietary crude protein concentration and inulin supplementation on nitrogen excretion and intestinal microflora from finisher pigs

A 2 × 2 factorial experiment was used to investigate the interaction between dietary crude protein (CP) concentration (200 vs 140 g/kg) and inulin supplementation (0 vs 12.5 g/kg) on nitrogen (N) excretion and intestinal microflora from 16 boars (n = 4, 74.0 kg live weight). The diets were formulated to contain similar concentrations of digestible energy and lysine. Pigs offered the high CP diets had a higher excretion of urinary N (P < 0.01), faecal N (P < 0.01) and total N (P < 0.001) than the pigs offered the low CP diets. Inulin supplementation increased faecal N excretion (P < 0.05) and decreased urine: faeces N ratio (P < 0.05) compared to the inulin free diets. There was no significant effect (P > 0.05) of dietary treatment on N retention. There was an interaction (P < 0.05) between dietary CP concentration and inulin supplementation on caecal E.coli. Pigs offered the diet containing 200 g/kg CP plus inulin decreased the population of E.coli compared to the inulin supplemented 140 g/kg protein diet. However, CP concentration had no significant effect on the population of E.coli in the unsupplemented diets. Inulin supplementation increased caecal bifidobacteria (P < 0.01) compared to the inulin free diets. In conclusion, inulin supplementation favourably altered N excretion and lowered the population of E.coli at high CP concentrations.     

Postnatal changes in electromyographic signals during piglet growth, and in relation to muscle fibre types

This study uses non-invasive evoked surface electromyography (SEMG) to investigate postnatal muscle development in pigs, and to assess any correlation between recorded signal parameters and muscle fibre types in two different skeletal muscles. Four litters (n = 43) of Large White × Landrace pigs were used. Evoked SEMG measurements were taken on days 2, 5, 14, 26, 60 and 151 post partum from m. Longissimus dorsi (LD) and on days 14, 26, 60 and 151 post partum from m. Biceps femoris (BF). A third of each litter was slaughtered at days 27, 61 and 153 post partum. Biopsy samples for LD and BF were taken to categorize muscle fibre types. For LD there was a significant increase in compound muscle action potential (CMAP) parameters from day 2 to day 5 post partum, whilst for BF significant increases occurred from days 14 to 26 post partum. Fibre type development in both muscles showed a significant decrease in type IIA fibre number (P < 0.001) and an increase in type IIB fibre number (P < 0.001). Analysis of CMAP parameters in relation to fibre type percentages showed significant positive correlations between percentage of type I fibres in BF and CMAP Area (r = 0.71; P = 0.05), SlopeL (r = 0.79; P = 0.02) and Corr Peak (r = 0.78; P = 0.02) and a negative correlation with SlopeT (r = 0.89; P = 0.003) at day 151. A greater CMAP Area and Corr Peak as well as steeper leading and trailing slopes were on the other hand correlated to fewer type IIB fibres.

It is concluded that 1) changes in the evoked CMAP are muscle-specific during early postnatal development in the pig, and 2) in spite of a small sample size, the correlations between CMAP signal parameters and fibre type percentages warrant further investigation.     

Genomic, protein and antigenic variability of mycoplasma bovis

Restriction endonuclease analysis (REA) with three enzymes SmaI, PstI, BamHI- was used to identify 13 different genomic groups among 37 Mycoplasma bovis strains. One genomic group was comprised of 14 strains. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) patterns for one strain chosen from each genomic group and an international reference strain PG45 were all similar. Antigenic variability in M. bovis species was investigated by immunoblotting, using serum from a calf that had been naturally infected with M. bovis and three M. bovis-specific monoclonal antibodies — mAbs N₂, I₂ and 5D7. Twenty M. Bovis field strains were tested, comprising one from each genomic group, six from the same genomic group and the reference strain. Antigenic profiles obtained with calf serum differed markedly one from the other, the heterogeneity being equally great among the strains belonging to the same genomic group as those coming from different groups. A stable antigen common to 164 out of 168 strains was detected by mAb N₂, whilst with mAbs I₂ and 5D7, two different membrane antigenic systems were demonstrated that were strikingly variable. These variations in expression occurred not only from one strain to another, but also within the same lineage of clones from a single cell.