Occurrence of Mycobacterium avium subsp. paratuberculosis in milk at dairy cattle farms: a systematic review and meta-analysis

Presence of Mycobacterium avium subsp. paratuberculosis (MAP) in milk for human consumption is a concern due to its possible relationship with Crohn's disease in humans. Pasteurization effectively reduces the MAP load by four to five logs, but the efficacy depends on the MAP concentration, which depends on the prevalence among contributing herds and individuals. Considerable variation of MAP in bulk tank milk (BTM) and individual cow's milk (IM) is reported, but factors associated with MAP occurrence in milk at farm level have not been described. This study systematically reviewed published studies aiming at estimating the occurrence of MAP in on-farm BTM and IM by meta-analysis. A total of 692 articles were identified through electronic databases and initially screened using title and abstract. The quality of the 61 potentially relevant articles was assessed using full text and 31 articles were eventually included in the meta-analysis. The apparent prevalence (AP) of MAP in BTM and IM on farm were summarized in relation to strata defined by the test used to identify MAP and the infection status of the herds/animals. There was considerable inconsistency in the reporting, resulting in missing information potentially explaining the dispersion in the estimated AP. The overall AP and 95% confidence intervals based on PCR and culture of MAP were summarized to 0.10 (0.04-0.22) in BTM and 0.20 (0.12-0.32) in IM. Quantifying the MAP load in test-positive milk samples was not possible because very few articles provided quantitative information on individual samples.     

硫酸铜,硝酸银和脱落酸对草地早熟禾胚性愈伤诱导的影响

试验以草地早熟禾4个品种的成熟种子为外植体,研究了CuSO4、AgNO3、脱落酸(ABA)对草地早熟禾胚性愈伤诱导的影响,结果表明,K3诱导培养基中添加CuSO4对草地早熟禾胚性愈伤组织的形成有促进作用,除DP192-10之外的3个品种都发生了明显的形态上的变化,DP-LF-300和2W42-117在添加5μmol/LCuSO4的培养基上诱导出了乳白色、致密的胚性愈伤组织,2W42-117的胚性愈伤率高达40%。在MS基本培养基中添加AgNO3、ABA对草地早熟禾4个品种的胚性愈伤组织的诱导没有作用。     

Root-released organic acids and phosphorus uptake of two barley cultivars in laboratory and field experiments

A major portion of phosphorus (P) applied as fertilizers is bound in soils as P compounds of variable adsorption strength, reducing the effectiveness of P fertilization. Plant genotypes equipped with mechanisms for utilizing the adsorbed P more efficiently can, therefore, enhance the effectiveness of P fertilization. Such genotypes will also enrich plant gene pools for further analysis and upgrading of P efficiency by selection and breeding. We studied the variation and the mechanisms of P uptake of two winter barley (Hordeum vulgare L.) cultivars Marinka and Sonate (parents of existing 200 haploid progeny lines), by laboratory and field experiments. After cultivation in nutrient solution for 21 days, Marinka produced more roots than Sonate, but similar amounts of dry shoots of lower P content (Marinka 3.4±0.4 mg g⁻¹, Sonate 4.9±0.6 mg g⁻¹). The total P uptake per plant did not differ between the cultivars. Marinka retained more P in roots as indicated by the higher concentration of P in the roots (Marinka 3.9±0.3 mg g⁻¹ and Sonate 3.0±0.4 mg g⁻¹). In sterile nutrient solution culture, the cultivars differed mainly in release of organic acids from the roots, with Marinka releasing three times more citric acid and nearly two times more acetic acid than Sonate. The cultivars had similar root hair lengths and they did not differ (P>0.05) in depletion of available soil P fraction (extracted with 0.5 M NaHCO₃) in the rhizosphere. Marinka absorbed nearly twice as much P from the strongly adsorbed soil P fraction (extracted with 0.1M NaOH). Also under field conditions, Marinka absorbed more P and produced more shoot dry matter. The higher P uptake by Marinka than Sonate can be attributed to its ability to acquire P from strongly adsorbed soil P by releasing more organic acids, especially citric acid, from its roots.     

Rehydration fluid temperature affects voluntary drinking in horses dehydrated by furosemide administration and endurance exercise

To determine whether temperature of rehydration fluid influences voluntary rehydration by horses, six 2-3-year-old horses were dehydrated (4-5% body weight loss) by a combination of furosemide administration and 30 km of treadmill exercise. For the initial 5 min following exercise, horses were offered a 0.9% NaCl solution at 10, 20, or 30 degrees C. Subsequently, after washing and cooling out, voluntary intake of water at 10, 20, or 30 degrees C from 20 to 60 min after exercise was measured. Fluid intake (FI) during the first 5 min of recovery was 9.8+/-2.5,12.3+/-2.1 and 9.7+/-2.0L (p>0.05) for saline at 10, 20, and 30 degrees C, respectively. Although not a significant finding, horses offered 0.9% NaCl at 20 degrees C tended to take fewer (p=0.07), longer drinks than when saline at either 10 or 30 degrees C was offered. Between 20 and 60 min of recovery, intake of water at 20 degrees C (7.7+/-0.8L) and 30 degrees C (6.6+/-1.2L) was greater (p<0.05) than that at 10 degrees C (4.9+/-0.5L). Thus, total FI was 14.7+/-2.5,19.9+/-2.5, and 16.3+/-2.4L for rehydration fluids at 10, 20, and 30 degrees C, respectively (p<0.05, value for 20 degrees C water greater than that for 10 degrees C water). Although the amount of metabolic heat transferred to the initial saline drink was correlated with the decrease in core temperature during the initial 5 min of recovery, heat transfer to ingested fluid was most likely responsible for the dissipation of, at most, 5% of the heat generated during endurance exercise. In conclusion, following exercise these dehydrated-normothermic horses voluntary drank the greatest amount of fluid at near ambient (20 degrees C) temperature. Although not determined in this study, greater satiation of thirst by oropharyngeal cooling may have contributed to lesser intake of colder (10 degrees C) fluid.     

Demonstration of airborne transmission of Actinobacillus pleuropneumoniae serotype 2 between simulated pig units located at close range

Airborne transmission of Actinobacillus pleuropneumoniae was studied as the percentage of air needed to establish airborne transmission from an infected pig unit into a neighbouring non-infected pig unit. The experiment was carried out in two containers constructed as pig units, placed 1m apart and connected by pipes. By manipulating the air pressure in the two units, the amount of ventilation air transferred from the infected pigs (unit A) to the non-infected pigs (unit B) was controlled and measured. In three experiments, between 48 and 50 specific pathogen free-pigs were randomly assigned to each of the two units. In unit A, five pigs (experiment 1) or eight pigs (experiments 2 and 3) were inoculated with A. pleuropneumoniae serotype 2. In experiments 1 and 3, 10% of the air was transferred from unit A to B; in experiment 2, 70% of the air was transferred. In the non-infected unit (B), 36% of the pigs seroconverted during experiment 2 (70% air transfer), whereas none of the pigs seroconverted in experiments 1 and 3 (10% air transfer). As air transmission between closely located pig units has been estimated to be less than 2% under field conditions, these results indicate that airborne transmission of A. pleuropneumoniae serotype 2 between closely located pig units is rare.     

Herd prevalence of Salmonella spp. in Danish pig herds after implementation of the Danish Salmonella Control Program with reference to a pre-implementation study

The problems addressed are: (1) comparison of prevalences of Salmonella spp. in different herd types in the Danish pig population after implementation of the Danish Salmonella Control Program (DSCP), and (2) to make a reference to a study from 1993/1994 (pre-implementation) with a discussion of possible biases when diagnostic methods differ slightly. The objectives were to present the prevalences of Salmonella spp., Salmonella Typhimurium, and multiresistant S. Typhimurium DT104 in Danish pig herds in 1998. Further, to discuss how herd prevalences may be compared to a previous study.A bacteriological study in 1998 comprised: (a) a random sample of slaughter pig producing herds (N=1962); (b) a random sample of farrow-to-grower (sow) herds (N=305); and (c) all breeding and multiplying (genetic) herds (N=366). A previous bacteriological study on Salmonella presence in 1993/1994 served as a model for the present study. The results of the study were that multiresistant S. Typhimurium DT104 was detected in one herd producing slaughter pigs. The herd apparent prevalences (HAPs) of Salmonella spp. were 11.7, 16.7 and 11.4% in genetic, sow, and slaughter pig herds, respectively. The conclusion of the study was that prevalence of multiresistant S. Typhimurium DT104 was low in the examined slaughter pig herds. The herd true prevalence (HTP) of Salmonella spp. in pigs had declined from before the start of the DSCP in 1993/1994 to 4 years later (1998).     

Influence of age,sex and herd characteristics on the occurrence of Verocytotoxin-producing Escherichia coli O157 in Danish dairy farms

Verocytotoxin-producing Escherichia coli (VTEC) O157 is an important emerging human pathogen. Cattle are considered to be the main reservoir for VTEC O157. The objectives of this study were to determine the prevalence of VTEC O157 in Danish dairy herds and to investigate the relationship between shedding of VTEC O157 and a number of animal and herd characteristics. Sixty dairy farms were visited once in August-October, and from each herd faecal samples from up to 50 animals were analysed for VTEC O157 by enrichment, immunomagnetic separation (IMS), and plating on selective agar. In total, 2419 animals were sampled, and 3.6% of these excreted VTEC O157. These animals were located on 10 farms (17%). On average, 21% of the sampled animals in the positive herds excreted VTEC O157. Register data, including age, sex, breed, housing conditions and herd composition, were extracted from a database. No influence of herd size or housing conditions was found. A strong effect of age was seen with 2-6-month-old calves as the high-risk age group (8.6% positive) in contrast to calves <2 months (0.7%) and cows (2.4%). There was a non-significant tendency of bull calves to have a higher prevalence than heifers within the age group of 2-6 months. Significantly, more of the herds characterised by having relatively many bull calves or many animals bought into the herd were positive for VTEC O157. Despite the low incidence of human VTEC O157 infections in Denmark, the prevalence in Danish dairy herds was found to be at a similar level as in many other countries.     

Estimation of Milk Production in Lactating Sows by Determination of Deuterated Water Turnover in Three Piglets per Litter

The milk intake in piglets from four lactating sows was measured in three 48 h periods, starting on days 3, 10 and 17 of lactation, using the deuterium oxide (D 2 O) dilution technique. The milk intake was estimated from the water turnover in the piglets corrected for the production of metabolic water. The water turnover was estimated from the water dilution space and the fractional turnover of body water, determined by the rate of D 2 O dilution. To determine the magnitude of isotopic recycling, a randomly selected piglet in each litter was not enriched with D 2 O. Milk production of the four lactating sows was also measured by the weigh-suckle-weigh (WSW) method on days 4, 11 and 18 of lactation. The average daily milk production determined by the D 2 O dilution technique (9.91 - 0.69 kg) was higher ( P <0.05) than that determined by the uncorrected WSW method (8.65 - 0.81 kg). Different procedures for selecting piglets were evaluated to obtain the best possible estimation of total milk production from three piglets in each litter. The total milk production of a sow based on three piglets in the litter was obtained from a quadratic model of the relationship between milk intake and daily gain. When the daily gain of all piglets were known the Pearson correlation between milk production determined for the whole litter ( n -1) and only three median piglets was 0.98.     

Genetic variation of in vivo muscle glycerol,glycogen, and pigment in Danish purebred pigs

Heritability values of glycerol, glycogen and pigment concentrations measured on muscle biopsy samples from longissimus dorsi obtained from 85?kg boars of Danish purebred pigs (Landrace, Yorkshire, and Duroc) and their genetic correlations to performance and meat quality traits were calculated. The heritability values of glycogen, pigment, and glycerol were 0.38±0.02, 0.17±0.02, and 0.065±0.016, respectively. Glycogen was negatively related to the feed conversion ratio (FCR) (r _g =?0.25±0.06) and ultimate meat pH (r _g =?0.41±0.04), and positively to the carcass meat percentage (r _g =0.35±0.04), L* (lightness of meat, r _g =0.32±0.04) and a* (redness of meat, r _g =0.12±0.03). Pigment was positively related to the FCR (r _g =0.12±0.05), the meat percentage (r _g =0.28±0.05), and a* (r _g =0.59±0.04), and negatively to the L* (r _g =?0.46±0.06). The concentrations of pigment and glycogen (r _g =0.27±0.05) were interrelated. Based on the heritability values and the signs of the genetic correlations the present data suggest that it is possible to select for higher ultimate pH and improved colour by selection for either lower muscle glycogen or higher pigment concentration, respectively. However, the positive genetic correlation between these two traits may restrict the efficiency of simultaneous selection for lower glycogen and higher pigment. All genetic parameter estimates presented are calculated across three purebreds. Values for each breed are warranted for use in pig production. However, this requires more animals per breed.     

The Effect of Low-Dose Marine n-3 Fatty Acids on Plasma Levels of sCD36 in Overweight Subjects: A Randomized,Double-Blind,Placebo-Controlled Trial

CD36 is a scavenger receptor involved in lipid uptake and inflammation. Recently, non-cell-bound CD36 (sCD36) was identified in plasma and suggested to be a marker of lipid accumulation in the vessel wall. Marine n-3 polyunsaturated fatty acids (PUFA) may have cardioprotective effects. This study evaluated the effect of marine n-3 PUFA on sCD36 levels in overweight subjects. Fifty overweight subjects were randomized to 1.1 g of n-3 PUFA or 2 g of olive oil daily for six weeks. Neutrophils were isolated at baseline and after six weeks of treatment while an adipose tissue biopsy was obtained at baseline. The content of n-3 PUFA in adipose tissue and neutrophils was analyzed by gas chromatography, while plasma levels of sCD36 were determined using an enzyme-linked immunosorbent assay (ELISA). After six weeks of supplement plasma sCD36 did not differ between supplements (P = 0.18). There was no significant correlation between plasma sCD36 levels and n-3 PUFA in neutrophils at baseline (r = −0.02, P = 0.88), after six weeks supplement (r = −0.03, P = 0.85) or in adipose tissue (r = 0.14, P = 0.34). This study therefore does not provide evidence for a cardioprotective effect of n-3 PUFA acting through a CD36-dependent mechanism.