Inflammation of the mammary gland, mastitis in cows, presents one of the most acute problems in intensive dairy production, inflicting huge economic losses. In the course of one year, 80 samples were taken at investigated farms from udder quarters of cows with clinical mastitis and 160 samples from udder quarters of cows with subclinical mastitis. The efficacy of three preparations, A, B, and C, was examined in the treatment of clinical and subclinical mastitis in cows. The investigations indicate that antibiotic preparation A (neomycin, polimixine B, oleandomycin and prednisolone) exhibited a greater efficacy in the treatment of clinical mastitis caused by Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis and Micrococcus sp., but a smaller efficacy in the treatment of subclinical mastitis caused by Staphylococcus aureus. Preparation B (amoxicillin, clavulanic acid and prednisolone) exhibited a higher efficacy in the treatment of clinical mastitis caused by Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis and Micrococcus, but a weaker effect in the treatment of subclinical mastitis caused by Staphylococcus aureus. Preparation C (procaine penicillin G, streptomycin, neomycin sulfate and prednisolone acetate) exihibited efficacy in the treatment of clinical and subclinical mastitis caused by Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, Micrococcus, Staphylococcus aureus and Esherichie coli. [Projekat Ministarstva nauke Republike Srbije, br. III 46002: Molekularno-genetička i ekofiziološka istraživanja u zaštiti autohtonih animalnih genetičkih resursa, očuvanju dobrobiti, zdravlja i reprodukcije gajenih životinja i proizvodnji bezbedne hrane

The objective of this study was to investigate the effects of peroral administration of chromium-enriched yeast on glucose tolerance in Holstein calves, assessed by insulin signaling pathway molecule determination and intravenous glucose tolerance test (IVGTT). Twenty-four Holstein calves, aged 1 month, were chosen for the study and divided into two groups: the PoCr group (n = 12) that perorally received 0.04 mg of Cr/kg of body mass daily, for 70 days, and the NCr group (n = 12) that received no chromium supplementation. Skeletal tissue samples from each calf were obtained on day 0 and day 70 of the experiment. Chromium supplementation increased protein content of the insulin β-subunit receptor, phosphorylation of insulin receptor substrate 1 at Tyrosine 632, phosphorylation of Akt at Serine 473, glucose transporter-4, and AMP-activated protein kinase in skeletal muscle tissue, while phosphorylation of insulin receptor substrate 1 at Serine 307 was not affected by chromium treatment. Results obtained during IVGTT, which was conducted on days 0, 30, 50, and 70, suggested an increased insulin sensitivity and, consequently, a better utilization of glucose in the PoCr group. Lower basal concentrations of glucose and insulin in the PoCr group on days 30 and 70 were also obtained. Our results indicate that chromium supplementation improves glucose utilization in calves by enhancing insulin intracellular signaling in the skeletal muscle tissue.

Season may affect calves' thermal comfort and behavior, but the data related to the overall influence of seasonal variations on dams' colostrum and postnatal adaptive capability of calves are limited. The aim of this study was to measure the effects of a 49-day-long low air temperature (LAT) season (5.20 ± 0.46 °C mean air temperature) and a 53-day-long high air temperature (HAT) season (27.40 ± 0.39 °C mean air temperature) on dams' colostrum quality and physiological, biochemical, hormonal, and oxidative stress parameters of their calves during the first 7 days of life. The dams' colostrum was sampled at 2, 14, and 26 h after calving, before feeding of their calves. Calves' blood samples were taken before the first colostrum intake and on days 1, 2, 3, and 7 of life. Calves' physiological parameters were measured on days 0 and 7. HAT season significantly reduced the quality of dams' colostrum. The ingestion of the low-quality colostrum, combined with the thermal discomfort during HAT season, probably provoked impaired physiological, biochemical, hormonal, and oxidative stress parameters in samples taken from the post-colostral calves. Additionally, intravenous glucose tolerance test was performed on day 7, which suggested an enhanced insulin response in HAT season calves. This study highlights the importance of adequate supporting strategies for the care of the late gestation cows and postnatal calves during the HAT season.

SummaryThirty days before expected time of parturition, 20 Holstein cows were divided into ÀCr and +Cr groups. From day 25 before parturition (BP) up to day 30 after parturition (AP), +Cr cows received 10 mg of Cr (chromiumenriched yeast) daily. Muscle and adipose tissue samples were taken at days À30, À10, +7 and +10 related to parturition, when body condition score (BCS) was also determined. Hepatic tissue samples were taken at days À10 and +7. Tissue samples were used for determination of the insulin signalling pathway protein expressions. Intravenous glucose tolerance test (IVGTT) was performed at days À28, À7, +10 and +30. Milk yield was recorded during first 14 weeks AP. Milk composition was obtained at days 7 and 28 AP. At day 10 BP, protein content of b-subunit of insulin receptor (IRb) was significantly higher (p ˂ 0.05) in muscle, and phosphorylation of insulin receptor substrate 1 at serine 307 (pIRS-1 Ser 307 ) was significantly lower (p ˂ 0.05) in hepatic tissue of +Cr group. After parturition, pIRS-1 Ser 307 was significantly lower in muscle tissue at days 7 and 28 (p ˂ 0.05 and p ˂ 0.001, respectively), while phosphorylation of Akt at serine 473 (pAkt Ser 473 ) was significantly higher (p ˂ 0.01) in hepatic tissue at day 7 AP in +Cr group. Chromium had opposite effect on insulin kinetics during IVGTTs obtained BP and AP. Insulin secretion was significantly reduced at day 7 BP and significantly enhanced at day 10 AP, when NEFA concentration was also significantly increased. Milk yield and ECM value were depressed in +Cr group. DMI and BCS were significantly enhanced in +Cr group at day 7 BP. In conclusion, chromium modulates insulin signalling pathway in dairy cows, but targeted signalling molecules are different in antepartal then post-partal period, probably due to duration of exposure to chromium and different energy status between those periods.

Mastitis in cows represents one of the most actual problems in intensive dairy production. The longtime different approaches to the treatment of mastitis have not offered a suitable solution, and the problem of mastitis is still present and acute. Prevention of pathogen penetration into the mammary gland, its colonization and multiplication impose a constant need for regular inspections of milk, as well as preventive and therapeutic measures to reduce the incidence of mastitis. Studies in the field of vaccination of ruminants against mastitis pathogens suggest a limited success in obtaining significant results in immunoprophylaxis. Considering the results of other researchers and our own research, and bearing in mind the problems mastitis caused by Staphylococcus aureus and Streptococcus agalactiae represent, the aim of this study was the preparation and testing of an indigenous vaccine prepared with two stable strains, SAU 7 (S. aureus) and SAG 3 (Str.agalactiae). The dose was 5 mL/cow and consisted of inactivated bacterial S. aureus SAU 7 cells in a concentration of 1x10 10 cfu/mL and Str. agalactiae SAG 3 in a concentration of 4 x 10 9 cfu/mL. The number of somatic cells in the milk samples during the whole study period was higher in vaccinated cows in both groups compared with the control, but this difference was not statistically significant. The concentration of immunoglobulin IgG in the milk of vaccinated cows was significantly higher than the concentration of this class of proteins in the milk of unvaccinated cows.