Assessment of Plasma Zinc and Total Leukocyte Count in Calves Experimentally Infected with Mannheimia haemolytica.

Mannheimia haemolytica is the main bacterial pathogen isolated in bovine respiratory disease (BRD), a common disease affecting calves before weaning. Previous research has shown that experimental infection with bovine herpesvirus 1, a respiratory virus, decreases plasma zinc (Zn) levels. However, changes in plasma Zn concentrations in calves experimentally infected with M. haemolytica have not been studied thus far. The objective of this study was to evaluate the effect of experimental infection with M. haemolytica on plasma Zn concentration in calves. Total leukocyte count and bovine respiratory disease (BRD) clinical score were also evaluated. We conducted a 6-day trial in 14 male Holstein calves randomly assigned to one of two groups, experimental (EG, n = 8) and control (CG, n = 6). Animals in EG were intrabronchially inoculated with M. haemolytica (6.5 × 106 CFU/mL) on day 0 of the trial. Plasma Zn levels were affected by time, treatment, and time by treatment interaction, being lower in EG compared with CG on days 1, 2, and 3. Differences in total leukocyte count were significant on day 1, observing a tendency on day 3. BRD clinical score differed between groups, being higher in EG throughout the trial. We conclude that experimental M. haemolytica infection reduced plasma Zn concentration in clinically ill calves, suggesting that the clinical condition of animals (healthy/ill) should be considered to better interpret plasma Zn values.

Analyses of apoptosis and DNA damage in bovine cumulus cells after in vitro maturation with different copper concentrations: consequences on early embryo development.

The aim of this study was to investigate the influence of copper (Cu) during in vitro maturation (IVM) on apoptosis and DNA integrity of cumulus cells (CC); and oocyte viability. Also, the role of CC in the transport of Cu during IVM was evaluated on oocyte developmental capacity. Damage of DNA was higher in CC matured without Cu (0 µg/dl Cu, P < 0.01) with respect to cells treated with Cu for cumulus-oocyte complexes (COCs) exposed to 0, 20, 40, or 60 µg/dl Cu). The percentage of apoptotic cells was higher in CC matured without Cu than in CC matured with Cu. Cumulus expansion and viability of CC did not show differences in COC treated with 0, 20, 40, or 60 µg/dl Cu during IVM. After in vitro fertilization (IVF), cleavage rates were higher in COC and DO + CC (denuded oocytes + CC) with or without Cu than in DO. Independently of CC presence (COC, DO + CC or DO) the blastocyst rates were higher when 60 µg/dl Cu was added to IVM medium compared to medium alone. These results indicate that Cu supplementation to IVM medium: (i) decreased DNA damage and apoptosis in CC; (ii) did not modify oocyte viability and cumulus expansion; and (iii) improved subsequent embryo development up to blastocyst stage regardless of CC presence during IVM.

Electrocardiographic changes in normal and abnormal canine pregnancy.

The aim of this study was to describe the canine electrocardiographic changes in the course of normal and abnormal pregnancy. Twenty-three Brucellosis-negative pregnant bitches were retrospectively classified as normal (n = 12) or abnormal (n = 11). A control group of non-pregnant dioestrous bitches (n = 10) was also included. Normal pregnant females delivered healthy puppies at term while abnormal animals interrupted their pregnancy between days 52-60 (from estimated luteinizing hormone peak) or presented perinatal litter death higher than 60%. All the bitches were electrocardiographically evaluated every 10 days from day 0 to day 65 of the oestrous cycle, to parturition or abortion. Percentage heart rate change increased 31.3% from day 40 to 60 in normal gestation while it decreased -1.8% in dioestrous bitches, although it did not change in the abnormal group (p < 0.01). In the abnormal pregnant group but not in the others, percentage QRSa change fell to -34% on day 60 (p < 0.01). At the same time point, percentage QRSd change was 6.2% vs -4.9% in normal gestations and dioestrous animals, respectively (p < 0.05). Corrected QT interval augmented from day 40 onwards up to 9.9% and 4.3% in the normal pregnant and dioestrous groups, respectively, while it remained unchanged in abnormal gestations (p < 0.05). It is concluded that during normal canine pregnancy, some electrocardiographic parameters begin changing from day 40 onwards, and that pathological gestations differ from normality from day 30. The use of electrocardiography in canine obstetrics might contribute to identify abnormal outcomes before they become clinically evident.

Effect of increasing zinc sulphate concentration during in vitro maturation of bovine oocytes.

The objective was to investigate the effects of supplementary zinc (Zn) during in vitro maturation (IVM) of bovine oocytes. The DNA damage in cumulus cells was low with supplemental Zn concentrations of 1.1 and 1.5 µg/mL in the IVM medium (mean ± SEM index of DNA damage was 67.52 ± 9.32, 68.52 ± 13.34, 33.80 ± 4.89, and 34.65 ± 7.92 for supplementation with 0, 0.7, 1.1, and 1.5 µg/mL Zn, respectively; P < 0.01). Total glutathione concentrations did not differ following Zn supplementation of 1.1 and 1.5 µg/mL (3.7 ± 0.4 vs. 4.0 ± 0.5 pmol, respectively, in oocytes; and in cumulus cells, 0.5 ± 0.04 nmol/10(6) cells, combined for both treatments), but were greater (P < 0.01) than supplementation with 0.7 µg/mL (1.8 ± 0.5 pmol in oocytes and 0.2 ± 0.02 nmol/10(6) cumulus cells). Cleavage rate increased (P < 0.05) when Zn was added to the IVM medium at any concentration (67.16 ± 1.17, 73.15 ± 1.15, 74.05 ± 1.23, and 72.76 ± 0.74 for 0, 0.7, 1.1, and 1.5 µg/mL Zn). For these concentrations, subsequent embryo development to the blastocyst stage was 17.83 ± 2.15, 21.95 ± 0.95, 27.65 ± 1.61, and 30.33 ± 2.78%, highest (P < 0.01) in oocytes matured with 1.5 µg/mL Zn. There was an increase (P < 0.05) in mean cell number per blastocyst obtained from oocytes matured with 1.1 and 1.5 µg/mL Zn relative to 0 Zn (IVM alone) and 0.7 µg/mL Zn. In conclusion, Zn during oocytes maturation significantly affected intracellular GSH content and DNA integrity of cumulus cells, and improved preimplantational embryo development. We inferred that optimal embryo development to the blastocyst stage was partially dependent on the presence of adequate Zn concentrations.

Association between copper deficiency and DNA damage in cattle.

Cattle hypocuprosis is the second most widespread mineral deficiency affecting grazing cattle. The consequences of hypocuprosis include a failure of copper metalloenzymes, many of which form part of the antioxidant defence system. This work focuses on the association between copper (Cu) plasma concentration and DNA damage in Aberdeen Angus cattle. Two-hundred and ninety-nine heparinized blood samples from 2-year-old Aberdeen Angus cows were obtained from different farms located in the Salado River basin, Argentina. Plasma copper level analysis was carried out in whole samples, while cytogenetic analysis and single cell gel electrophoresis assay (comet assay) were carried out in 82 and 217 samples, respectively. Cytogenetic analysis showed a significant increase in the frequency of abnormal metaphases in moderate/severe hypocupremic groups (groups B and C) in relation to the normocupremic group (group A) (4.5 and 1.5 abnormal metaphases/100 cells, respectively, P < 0.01). The Spearman correlation test showed a negative association between cupremic values and the yield of chromosomal aberrations (r = -0.708, P < 0.0001). In the comet assay greater migration was observed in cells from the hypocupremic group, from a median of 54 in the severe hypocupremic group to 31 in the normocupremic group (P < 0.01). Accordingly, the Spearman correlation test showed a significant positive relationship between copper levels and cells without DNA migration and a significant negative relationship between copper levels and cells with a tiny tail (P < 0.0001 in both cases). The results obtained show that hypocupremia in cattle is associated with an increase in the frequency of chromosomal aberrations as well as in DNA migration as assessed by the comet assay. Whereas the comet assay could differentiate copper plasma level groups, chromosomal aberrations only detected differences between normal and hypocupremic animals. The increase of DNA damage found in hypocupremic animals could be explained by higher oxidative stress suffered by these animals.