Oxidative stress and acid-base balance during the transition period of neonatal Holstein calves submitted to different calving times and obstetric assistance.

During the neonatal period, constant adaptations to the extrauterine environment are required. These adaptations are made impossible or hindered when unexpected obstetrical events take place. This study aimed to identify clinical changes of vitality, metabolic and acid-base balance, and oxidative stress of newborn calves born to assisted dams that experienced different durations of calving. A prospective and observational study was conducted with 44 Holstein calves allocated to 3 groups according to the duration of calving: 2 h (n = 16), 2-4 h (n = 16), and >4 h (n = 12), and to 2 subgroups: spontaneous calving (n = 22) and assisted calving (n = 22). We observed that obstetric assistance was beneficial when calving lasted more than 4 h, because 100% of assisted calves had a high Apgar score (≥7) at 5 min, similar to that of spontaneously born calves after 2 h of calving. Rectal temperature of all calves remained within normal values, albeit with a reduction at 20 min of life. Calves born after a calving time >4 h had the highest rectal temperatures, especially those that required obstetrical assistance. There was a progressive increase in blood oxygenation with time, but calves in the >4 h group showed the highest partial pressure of carbon dioxide at birth, whereas calves in the 2 h and 2-4 h groups had lower values. A decrease in partial pressure of CO2 was observed at 120 min in the 2-4 h and >4 h groups. In the 2-4 h group, calves with obstetrical assistance had higher oxidative stress (measured as thiobarbituric acid reactive substances, TBARS) at 120 min of life compared with that at birth. In spontaneously born calves, TBARS increased only after 240 min. In the >4 h group, TBARS increased progressively with time, regardless of obstetrical subgroup. Calves born spontaneously within the 2 h group had higher TBARS values at birth than calves in the >4 h group with obstetrical assistance. Calves in the >4 h group showed higher levels of glutathione peroxidase (an antioxidant enzyme) at birth than those in the remaining groups. Glutathione peroxidase decreased at 120 min in the >4 h group and at 240 min for the 2 h and 2-4 h groups. In conclusion, obstetric assistance did not improve neonatal vitality and blood oxygenation when calving lasted less than 2 h. Calves born after 2 h of calving showed decreased vitality, hypercapnia, hypoxemia, and increased antioxidant status (glutathione peroxidase).

Influence of the duration of calving and obstetric assistance on the placental retention index in Holstein dairy cows.

The aim of this study is to evaluate the influence of duration of calving and obstetric assistance on retained placenta incidence of high milk production Holstein cows. Experimental groups were determined according to the duration of the expulsive phase of calving: 2 h (n = 16), 2-4 h (n = 16) and >4 h (n = 12), and additionally allocated in two sub-groups: spontaneous calving (n = 22) and intervention calving (n = 22). Diagnosis of retained placenta was considered with a threshold of 8 h after the expulsive phase. Cows without obstetric intervention, with labor duration of 2 h, presented reduced time needed for placental release, in comparison to those with obstetric assistance. In the 2-4 h group and >4 h, there was no statistical difference. The 2 h and 2-4 h groups with intervention and the spontaneous >4 h group were considered retained placenta groups. On the other hand, performing obstetric intervention when calving period was superior to 4 h nulled the occurrence of retention of fetal membranes. As a conclusion, obstetric assistance predisposes placental retention to calving with <2 h of duration in dairy cows. Conversely, when calving is more than 4 h, performing fetal extraction has a beneficial influence on preventing retained placenta.

Immunohistochemical localization of VEGF and its receptors in the corpus luteum of the bitch during diestrus and anestrus.

The corpus luteum (CL) is a temporary endocrine gland, whose life span depends on the interaction of luteotrophic and luteolytic factors. Since development and maintenance of CL is based on angiogenesis, angiogenic growth factors may play a role in CL-function of the bitch, as described for other species. The aim of this study was to detect the presence of the vascular endothelial growth factor (VEGF) system in the bitch CL throughout diestrus and early anestrus. For that purpose, blood samples from 24 bitches were collected and analyzed for progesterone to determine ovulation time and the animals were subjected to ovariosalpingohysterectomy 10, 20, 30, 40, 50, 60 or 70 days after ovulation. The corpora lutea were fixed in formalin and embedded in Paraplast resin. Five micrometers sections were submitted to standard immunohistochemistry protocol using three primary antibodies (SC-315, SC-316 and VG76e) for detection of kinase domain region (KDR), fms-like tyrosine kinase 1 (Flt-1) and VEGF, respectively. The VEGF system expression could be detected in all diestrus stages in endothelial as well as luteal cells (responsible for blood vessel formation and progesterone production, respectively), indicating time dependent changes: immunostaining tended to increase from Day 10 to 50 and to decrease until Day 70 post-ovulation. In the CL of the bitch, structure related cells, like pericytes and stroma cells, expressed it in determined time points of diestrus with little intensity variation. We concluded that VEGF might have a modulatory effect in the CL of the dog acting as paracrine and autocrine factor through its receptors, Flt-1 and KDR.