Spatial and temporal patterns in the sex ratio of American lobsters (Homarus americanus) in southwestern Nova Scotia, Canada.

An approximate 1:1 sex ratio of American lobsters can be skewed due to environmental factors or fisheries management. Substantial skewness can impact mating behaviour and lower reproduction which could have far-reaching ecological and economic consequences. The aim was to investigate the sex ratio patterns of lobsters in two lobster fishing areas (LFAs) in southwestern Nova Scotia, Canada and identify factors associated with skewed sex ratios. This study analyzed biological data from more than 270,000 lobsters sampled over ten years (2010-2019) by the Fishermen and Scientists Research Society. A mixed effect logistic regression model evaluated the effect of spatial, temporal and environmental factors as well as size on the sex ratio of lobsters. There were significant temporal patterns in sex ratios that differed by LFA. After the effects of sampling month, year and LFA were accounted for, lower bottom temperature and deeper water depth were associated with a higher prevalence of females, especially in larger lobsters. We present the first long term analyses of sex ratio patterns in H. americanus in Atlantic Canada's most commercially important region for this species and provide evidence that these patterns are influenced by environmental factors and fisheries. In view of future climate change scenarios, monitoring the population dynamics of this iconic fishery species is crucial to ensure sustainable fisheries and healthy lobster stocks.

Transfer of maternal immunity to piglets is involved in early protection against Mycoplasma hyosynoviae infection.

Mycoplasma hyosynoviae causes arthritis in pigs older than 12 weeks. The role of colostrum in protection of piglets against M. hyosynoviae infection is not clear. Our objective was therefore to investigate whether transfer of maternal immunity to piglets was involved in early protection against the infection. Experimental infections were carried out in three groups of weaners receiving different levels of M. hyosynoviae-specific colostrum components; Group NC derived from Mycoplasma free sows and possessed no specific immunity to M. hyosynoviae. Group CAb pigs, siblings of the NC group, received colostrum with M. hyosynoviae-specific antibodies immediately after birth. Group CCE pigs were born and raised by infected sows and presumably had the full set of colostrally transferred factors, including specific antibodies. When 4½ weeks old, all pigs were inoculated intranasally with M. hyosynoviae. The course of infection was measured through clinical observations of lameness, cultivation of M. hyosynoviae from tonsils, blood and synovial fluid and observation for gross pathological lesions in selected joints. Specific immune status in the pigs was evaluated through detection of antibodies by immunoblotting and measurement of M. hyosynoviae-specific T-cell proliferation. The latter analysis may possibly indicate that M. hyosynoviae infection induces a T-cell response. The CCE piglets were significantly protected against development of lameness and pathology, as well as infection with M. hyosynoviae in tonsils, blood and joints, when compared to the two other groups. Raising the CCE pigs in an infected environment until weaning, with carrier sows as mothers, apparently made them resistant to M. hyosynoviae-arthritis when challenge-infected at 4½ weeks of age. More pigs in group NC had M. hyosynoviae related pathological lesions than in group CAb, a difference that was significant for cubital joints when analysed on joint type level. This finding indicates a partially protective effect of passively transferred M. hyosynoviae-specific colostral antibodies upon development of M. hyosynoviae related pathology. Thus, the level of passive immunity transferred from sow to piglet seems to provide, at least partial, protection against development of arthritis. It cannot be ruled out that the CCE pigs, by growing up in an infected environment, have had the chance to establish an active anti-M. hyosynoviae immune response that complements the maternally transferred immune factors. Evident from this study is that the general absence of M. hyosynoviae arthritis in piglets can be ascribed mainly to their immunological status.

The effect of selenium supplementation before calving on early-lactation udder health in pastured dairy heifers.

Selenium (Se) deficiency has been associated with lowered resistance to mastitis in dairy cattle. However, little published data exists on the effect of Se supplementation before calving on udder health of pastured dairy heifers. Further, the relative efficacy of injectable barium selenate and oral organic Se for improving udder health in cows has not previously been tested. The objectives of this study were to determine the effects of precalving Se supplementation and type of supplementation on the blood activity of glutathione peroxidase and measures of udder health immediately after calving and during the first month of lactation in pastured dairy heifers. One hundred forty pregnant Chilean Holstein-Friesian heifers were fed a basal diet containing, on average, 0.15 mg of Se/kg of dry matter. One month before predicted calving, heifers were allocated to 1 of 3 groups. Group 1 (n=49) received no supplementary Se, group 2 (n=46) received a single subcutaneous injection of Se (1 mg/kg of live weight, as barium selenate), and group 3 (n=45) was fed Se yeast (3 mg/heifer/d until calving). Heifers supplemented with barium selenate had a higher glutathione peroxidase activity from 14 d in milk onwards. Selenium supplementation, irrespective of source, tended to reduce the prevalence of intramammary infection (IMI) and decrease the prevalence of quarters with high somatic cell count (SCC) at calving. Overall, Se supplementation did not result in a reduction of the incidence of new IMI or clinical mastitis or in decreased SCC during the balance of the first month of lactation. However, in pasture-based heifers injected with barium selenate before calving, and fed diets with 1.3 and 2.5 mg of Se/d precalving and during lactation, respectively, no cases of clinical mastitis were observed in the first month of lactation.

Milk selenium concentration and its association with udder health in Atlantic Canadian dairy herds.

Soils and plants in Atlantic Canadian provinces are known to contain low concentrations of selenium (Se). Earlier studies have indicated that dairy producers in Atlantic Canada are providing insufficient supplementary Se in the ration to meet the Se requirements of dairy cattle, as measured by herd-level milk Se concentration. The objective of this study was to evaluate the association between milk Se concentration and somatic cell count (SCC) and the risk of new intramammary infection (IMI) in the dry period, in Atlantic Canadian dairy cows. Eighteen dairy farms participating in the Canadian Bovine Mastitis Research Network cohort study were selected as a convenience sample. On each farm 15 cows to be dried off were selected. Quarter milk samples were collected at 4 and 2 wk before drying-off, within 24 h after calving, and at 7 d after calving to evaluate IMI status. Composite milk samples were analyzed for SCC and Se concentration. Mean milk Se concentration was marginal in 14% of the cows that were on pasture during the grazing season. Milk Se concentration was not associated with the overall odds of new IMI in the dry period; however, the odds of having a new Streptococcus spp. and other gram-positive pathogen IMI in the dry period increased with increasing milk Se concentration. Somatic cell count increased with milk Se concentration, even after adjusting for IMI status. The dairy population in our study had higher ranges for milk Se concentration, whereas ranges for prevalence of IMI, and SCC were lower, compared with those in studies where a negative relationship between Se status and udder health was first noted. Therefore, under the current management conditions, milk Se concentration did not appear to be a principal determinant of udder health.

The effect of age on the immune response of horses to vaccination.

Few studies have investigated immunosenescence in the horse, but it is accepted that the primary and secondary (anamnestic) immune responses may differ between aged and younger horses. The aim of the present study was to determine whether aged horses have a protective immune response post-vaccination. Thirty-four aged healthy horses (> or =20 years) and 29 younger adult horses (4-12 years) of various breeds were vaccinated with commercially produced killed rabies and influenza vaccines. Rabies serum neutralizing antibody titres and equine influenza virus specific antibody subclasses (immunoglobulin IgGa and IgGb) and single radial haemolysis titres were determined. Healthy aged horses mounted a primary immune response to rabies vaccine that was similar to that of younger adult horses. However, aged horses had a significantly reduced anamnestic response to influenza vaccination in comparison with the younger adult horses, even though the pre-vaccination antibody titres of aged horses were higher. Rabies antibody titres in both groups declined significantly by 6 months post-vaccination. Serum concentrations of selenium (Se) and vitamin E were measured to test for potential confounding effects. Significant numbers of horses had suboptimal serum Se concentrations, but Se status had no significant impact on antibody production after vaccination.

Meta-analysis of the effect of oral selenium supplementation on milk selenium concentration in cattle.

Soils in many regions of the world have a low Se content. Consequently, forages and crops grown on these soils may provide inadequate dietary Se for humans and grazing animals. Selenium supplementation has been used to enhance Se status and milk Se concentration, but results conflict. Milk Se concentration appears to be a useful indicator of animal and herd Se status, and reflects the responsiveness to supplementation. A systematic review and meta-analysis were carried out to summarize all available scientific evidence for the effect of oral Se supplementation on milk Se concentration in cattle. The literature search was based on electronic and nonelectronic databases. Fixed- and random-effects models of meta-analysis were used, and a meta-regression was carried out to evaluate heterogeneity among studies. Random-effects meta-analysis was performed on 42 studies published between 1977 and 2007. Oral Se supplementation resulted in an average increase in milk Se content of 0.16 (95% confidence interval: 0.117, 0.207) micromol/L, with a significant heterogeneity among studies. Weak publication bias was evident, but it did not change the average effect. The continent where the study was performed, Se source, Se dose, and the interaction between source and dose explained 71% of the between-study variance. On average, American cows supplemented with Se yeast (e.g., 6 mg/h per day) had greater milk Se concentrations (approximately 0.37 micromol/L) 75 d after the beginning of supplementation when compared with those supplemented with inorganic forms of Se. This information provides a basis for tailoring daily animal requirements and for enhancing the Se intake of consumers of dairy products.

The effect of age on serum antibody titers after rabies and influenza vaccination in healthy horses.

BACKGROUND: The proportion of geriatric horses within the equine population has increased in the past decade, but there is limited information on the immune function of these animals. HYPOTHESIS: Aged horses will have a lesser increase in serum antibody response to vaccination. ANIMALS: Thirty-four aged healthy horses (> or = 20 years) and 29 younger adult horses (4-12 years) of various breeds. METHODS: All horses were vaccinated with vaccines of killed rabies and influenza virus. Horses in each age group were allocated to receive either rabies or influenza booster vaccine 4 weeks after the initial vaccination. Serum samples were taken at 0, 4, 8, and 24 weeks. Rabies serum neutralization titers and equine influenza virus specific antibody sub-isotypes (IgGa, IgGb, IgG(T), and IgA) as well as single radial hemolysis (SRH) titers were determined. RESULTS: Rabies antibody titers were similar in the 2 age groups at all sampling times. Aged horses had higher IgGa and IgGb influenza antibody titers before vaccination than younger horses but similar titers after vaccination (P= .004 and P= .0027, respectively). Younger horses had significantly greater increases in titer than aged horses at all sampling times for IgGa (P= .001) and at 8 and 24 weeks for IgGb (P= .041 and .01, respectively). There was no detectable serum IgG(T) at any time point. A significant booster vaccine effect was seen for both antirabies and anti-influenza titers. Anti-influenza titer before vaccination also had a significant effect on subsequent antibody response. CONCLUSIONS AND CLINICAL IMPORTANCE: Healthy aged horses generated a primary immune response to a killed rabies vaccine similar to that of younger adult horses. Aged horses had a significantly reduced anamnestic response to influenza vaccine.

Somatic cell count in milk of selenium-supplemented dairy cows after an intramammary challenge with Staphylococcus aureus.

The objective of this study was to evaluate the effect of selenium (Se) supplementation on milk somatic cell count (SCC) in dairy cows. Twelve multiparous Holstein-Friesian cows were fed a diet containing a suboptimal Se concentration (<0.05 ppm, dry basis) starting 2 months before calving. Supplemented cows (n=6) received a single s.c. injection of barium selenate (1 ml/50 kg BW) 45 days prior to calving, whereas control group was kept unsupplemented. Twenty weeks after calving, two mammary quarters (right side) of each cow were challenged with 205,000 cfu/ml of Staphylococcus aureus (strain Newbould 305). Blood was collected bi-weekly until day 150 of lactation for the analysis of blood glutathione peroxidase (GPx1; EC 1.11.1.9) activity. To re-isolate the challenging pathogen and to evaluate SCC, aseptic milk samples were collected daily starting on the day of challenge, and finishing 7 days after inoculation. Unsupplemented cows had a lower activity of GPx1 through the experiment (P<0.001). Natural log SCC (lnSCC) was higher in unsupplemented than Se-supplemented cows (P=0.04), showing evidence of significance after 5 days. Selenium supplementation of dairy cows fed a diet containing a suboptimal Se concentration, resulted in higher blood activity of GPx1, and lower mean lnSCC after an intramammary challenge with Staph. aureus.