Evaluation of the specificity of three enzyme-linked immunosorbent assays for detection of antibodies against Salmonella in bovine bulk milk

Background

The Swedish Salmonella control program has been running for decades and has resulted in a low prevalence of Salmonella in Swedish food producing animals. Routine bacteriology is used to detect Salmonella, however, bacteriology is time consuming, costly and has a low sensitivity. Different enzyme-linked immunosorbent assays (ELISAs) have been developed for detection of antibodies against Salmonella Dublin and S. Typhimurium in bovine bulk milk, individual milk samples as well as in sera. Screening bulk milk for antibodies against Salmonella spp. could improve the cost-effectiveness of the surveillance in Swedish dairy cattle, but as characteristics of tests may vary in different populations, tests should always be evaluated in the specific population where they will be used. Hence, the aim of this study was to evaluate the specificities of three bovine ELISAs when used to analyse bulk milk samples from Swedish dairy cattle. A second aim was to compare the performance of the two Dublin ELISAs tested.

Methods

Bulk milk samples for analysis were randomly selected from samples collected within the Swedish bulk milk sampling scheme and analyzed with the three ELISAs; a Danish in-house Dublin ELISA, PrioCHECK® Salmonella Ab bovine Dublin ELISA and PrioCHECK® Salmonella Ab bovine ELISA (hereafter named mixed ELISA). The specificities of the ELISAs were calculated assuming a disease-free status in Sweden i.e. that all test positive samples were assumed to be false positive results. This assumption can be used when a disease is known to be infrequent.

Results

The calculated specificities of the two Dublin ELISAs and the mixed ELISA, when using the producer’s recommended cut-off value of the corrected optic-density percent (ODC%) were 99.4% (95% Confidence Interval (CI): 98.8% -99.8%), 99.4% (95% CI: 98.8% -99.8%) and 97.9% (95% CI: 96.8% -98.7%), respectively. The correlation between the ODC% values of the two Dublin ELISAs was 0.83.

Conclusions

We conclude that the evaluated ELISAs have sufficiently high specificities to be used as supplement to bacteriological examinations in the Swedish Salmonella control program in cattle as well as a primary screening test in routine surveillance for S. Dublin.     

Detection of a Babesia sp. genotype closely related to marsupial-associated Babesia spp. in male Haemaphysalis shimoga from Sarawak,Malaysian Borneo

In this study, Babesia screening was conducted in 55 rodents and 160 tick samples collected from primary forests and an oil palm plantation in Sarawak, Malaysian Borneo. PCR targeting the 18S ribosomal DNA revealed the presence of Babesia spp. DNA detected in two questing male Haemaphysalis shimoga ticks collected from the oil palm plantation. Sequence analysis revealed that both sequences were identical and had 98.6% identity to a Babesia macropus sequence obtained from Eastern grey kangaroos (Macropus giganteus) in Australia. Phylogenetic tree revealed clustering with marsupial-associated Babesia spp. in the Babesia sensu stricto clade. Whether or not H. shimoga is the competent vector and the importance of the Babesia sp. detected in this study warrants more investigation.     

Red Drum Sciaenops ocellatus Field Trials: Economic Implications

Abstract.– Although recent changes in coastal fisheries regulations in several Gulf states have renewed interest in the economic potential for culture of red drum S. ocellatus , few decision making tools with up-to-date information on production economics are available. From 1988 to 1995, estimates of investment costs, equipment specifications and typical input utilization in commercial-scale production were developed from field trials involving complete or partial grow-out of S. ocellatus . Operating costs and expected yields were subsequently estimated based on "best-case" data from a 70-wk production trial in which 5–7 cm fingerlings were stocked on 1 July and grown to marketable size by the following November, thus avoiding a second overwintering period and the associated risks of losses from freezing temperatures. To allow an evaluation of potential returns with earlier or staggered stocking dates, however, growth and mortality rates from the 70-wk trial were used in a computer-based simulation to estimate yields and costs associated with a hypothetical growout period beginning 1 April, deemed the earliest suitable date to avoid fingerling mortality resulting from abrupt or extreme cold temperatures. The April stocking simulation projected a preferred market size of 1.4 kg prior to a second overwintering period, with yield increasing from 3,454 kg/ha to 4,203 kg/ha and a reduction in breakeven costs from $5.97/kg to $5.53/kg. Partial budget analysis, based on a current average market price of $5.72/ kg, suggested April 1 stocking could result in a positive net change of $1,679 per ha over July 1 stocking.     

Morphometry and abnormalities of the feet of Kaimanawa feral horses in New Zealand

Objective The present study investigated the foot health of the Kaimanawa feral horse population and tested the hypotheses that horses would have a large range of foot morphology and that the incidence of foot abnormality would be significantly high. Procedures Abnormality was defined as a variation from what the two veterinarian assessors considered as optimal morphology and which was considered to impact negatively on the structure and/or function of the foot. Fifteen morphometric variables were measured on four calibrated photographic views of all four feet of 20 adult Kaimanawa feral horses. Four morphometric variables were measured from the lateromedial radiographs of the left forefoot of each horse. In addition, the study identified the incidence of gross abnormality observed on the photographs and radiographs of all 80 feet. Results There was a large variation between horses in the morphometric dimensions, indicating an inconsistent foot type. Mean hoof variables were outside the normal range recommended by veterinarians and hoof care providers; 35% of all feet had a long toe conformation and 15% had a mediolateral imbalance. Abnormalities included lateral (85% of horses) and dorsal (90% of horses) wall flares, presence of laminar rings (80% of horses) and bull-nose tip of the distal phalanx (75% of horses). Both hypotheses were therefore accepted. Conclusions The Kaimanawa feral horse population demonstrated a broad range of foot abnormalities and we propose that one reason for the questionable foot health and conformation is lack of abrasive wearing by the environment. In comparison with other feral horse populations in Australia and America there may be less pressure on the natural selection of the foot of the Kaimanawa horses by the forgiving environment of the Kaimanawa Ranges. Contrary to popular belief, the feral horse foot type should not be used as an ideal model for the domestic horse foot.     

Effect of dry period length on the effect of an intramammary teat sealant on the risk of mastitis in cattle treated with antibiotics at drying off

AIM: The aim of this study was to evaluate, under farm conditions, the use of a teat sealant in addition to whole herd dry cow antibiotic therapy on the risk of clinical mastitis in dairy cattle at pasture, and to evaluate the impact of dry period length on that risk and the impact of the teat sealant on that risk.

METHODS: Dairy cows in three herds which used routine whole herd antibiotic therapy were randomly assigned to receive either treatment with an internal teat sealant (n=322) or no additional treatment (n=313) at drying-off between March and May 2010. All clinical mastitis cases during the dry period and to the end of the subsequent lactation were recorded by farm staff; factors affecting risk of clinical mastitis were then analysed using a Cox proportional hazards model.

RESULTS: Median duration of the dry period was 112 days with >25% of cows having a dry period >130 days. The incidence risk of mastitis during lactation for cows treated with teat sealant was 9.9 (95% CI=6.9–13.7) cases per 100 cows compared with 17.9 (95% CI=13.8–22.6) cases per 100 cows for cows treated with antibiotic alone. The addition of a teat sealant to dry cow antibiotic therapy decreased the risk of clinical mastitis only in the first 33 days after calving (Hazard risk 0.24 (95% CI=0.12–0.48)). Length of dry period did not significantly affect the risk of clinical mastitis, or the effect of adding teat sealant to dry cow antibiotic therapy on the risk of clinical mastitis.

CONCLUSIONS: In these herds where, based on the mastitis history, whole herd antibiotic therapy had been recommended, the use of a teat sealant significantly reduced the risk of clinical mastitis. This effect was limited to the first 33 days after calving; subsequently there was no significant effect of treatment. There was no effect of dry period length on risk of clinical mastitis, nor any significant interaction with treatment.

CLINICAL RELEVANCE: Combination therapy with teat sealant and antibiotic was effective under New Zealand conditions in herds using whole herd antibiotic treatment at drying off. Teat sealant reduced risk of clinical mastitis in cattle with dry periods substantially longer than 100 days, and there was no evidence that this effect changed as dry period length increased.     

Epigallocatechin‐3‐gallate (EGCG) and green tea polyphenols do not improve stallion semen parameters during cooling at 4°C

Stallion semen storage for artificial insemination is mainly based on liquid cooled storage. In many stallions this technique maintains sperm quality for an extended period of time (24–72 hr) at 7°C. While this technique is commonly used in the horse industry, there can be a decline in fertility in some stallions, due to an inability of their sperm to tolerate the cool storage process. The aim of the present work was to evaluate the effect of two natural antioxidants (epigallocatechin‐3‐gallate (EGCG) at 20, 60 and 120 μm and green tea polyphenols, and p at .001, .01 and .1 mg/ml) on some sperm parameters (sperm motility, viability/acrosome integrity and DNA quality) in extended semen immediately after its collection (T0) and after 2, 6, 24 and 48 hr of cool storage. Two ejaculates from three trotter stallions were analysed after 48 hr of storage at 4°C. No beneficial effect on the analysed parameters was observed: the two antioxidants were not able to improve sperm quality after 48 hr of storage. These results are in agreement with previous findings on the effect of different antioxidants reported by other researches, who have demonstrated that stallion semen keeps good antioxidant capacity after dilution for 24 hr. In conclusion, the positive effect exerted by antioxidant molecules in other species is not confirmed in the equine one.     

Growth performance,carcass and pork quality of finisher pigs fed oat-based diets containing different levels of beta-glucans

A study was undertaken to investigate the growth performance and carcass and meat quality of pigs (BW = 52 to 108 kg) fed oat-based (Avena sativa L.) diets containing four levels of mixed-linkage (1 --> 3), (1 --> 4)-beta-D-glucans. One hundred sixty pigs-80 barrows and 80 gilts (average starting BW = 52.7 kg)--were allocated to one of five diets: a wheat-barley-based control diet and four experimental diets. The groats of Marion, a covered oat, and OT789, a hulless oat, were used to formulate four isonitrogenous and isocaloric diets to achieve 4.1,3.3, 2.1, or 1.6% total /beta-glucans (as fed). Growth performance (daily gain and gain to feed ratio) was not affected (P > 0.05) by the different levels of beta-glucans. Carcass yield, although lower (P < or = 0.05) for pigs fed the control diet, was similar (P > 0.05) for pigs fed any of the experimental diets. Cutout yields were also alike (P > 0.05) across the five diets. Beta-glucan content had no effect (P > 0.05) on the longissimus muscle area, or, by and large, on the proportions of commercial cuts; the only exceptions were a commercial picnic from pigs fed the 2.1% diet lower (P < 0.05) relative to all other diets and a lower (P < 0.5) commercial loin from pigs fed diets 4.1 or 3.3% relative to the control diet. Furthermore, the relative proportions oftotal lean, total bone, and total dissectable fat in the four lean cuts (picnic, butt, loin, and ham) were not different (P > 0.05) among the five diets. For pigs fed 4.1% beta-glucans, the proportion of lean in each of the four major cuts was lower (P < 0.05). No differences (P > 0.05) associated with the level of beta-glucans were detected for either the initial or ultimate pH mean values, the subjective assessment of color or structure of the longissimus muscle, or the instrumentally measured color (L value). Similarly, drip loss was not influenced (P > 0.05) by the level of beta-glucans in the diets. Soluble protein did differ (P < 0.05) among the high- to low-beta-glucans diets. No differences (P > 0.05) associated with diets were found for fat hardness and shear values of grilled pork chops. Chemical fat of the longissimus muscle from pigs fed 4.1, 3.3, or 2.1% beta-glucans was lower (P < 0.05) compared to pigs fed the control or 1.6% beta-glucans diets. In summary, no evidence of detrimental effect of beta-glucans in oat-based diets, particularly at levels below 4%, was detected, lending support for the inclusion of oat into finisher diets.