NEWBORN CALVES' FEATURES IN RELATION TO THE TYPE OF DELIVERY

During recent years, an increase in perinatal mortality has been reported in dairy calves, quite typically not associated with an increase in the rate of dystocia. These perinatal losses not only represent a tremendous economic loss but also mirror an important welfare problem in cattle farms. In order to reduce the losses occurring during the perinatal and neonatal period, management of the parturient cow and newborn calf have to be addressed critically. As for all newborns, also calf’s survival and subsequent health conditions require a perfect transition from fetal to extra uterine life. Critical observation and/or investigation of the calf during and immediately after calving is important, considering that several problems encountered during the first days after delivery can originate from the calving period itself. In a crude analysis for fetal and neonatal outcomes related to the type of delivery in the human specie, the highest rates of neonatal morbidity and mortality were seen in the elective caesarean group. Elective caesarean delivery could increase neonatal morbidity and mortality because lack of labour affects the physiological process for initiation of respiration. Caesarean delivery is known to be associated with respiratory distress syndrome and transient tachypnoea possibly mediated by the lower release of catecholamine and prostaglandins, as well as the lack of the mechanical compression of the lungs during labour needed to facilitate postnatal lung adaptation. Moreover, several studies on babies demonstrated that the type of delivery can deeply influence the adaptational process in the newborn, modifying the immune response, the oxygenation status and the developing endocrine axis; the influence of delivery is not only immediate but extended in time, possibly affecting also the future health status of the subject. The main focus of this experimental thesis was on the effects of two different types of delivery on the conditions of the calf at birth and during the neonatal period; differences in clinical features and biochemical, metabolic, hormonal, hematological and inflammatory profiles, have been described and discussed in details. In the first study (chapter 7-8-9), clinical data and biochemical, metabolic and hormonal profiles from newborn calves born by spontaneous parturition or by caesarean section were compared. For each newborn many clinical data (Apgar score, rectal temperature, extimated weight) were collected within 5 minutes from birth. Time for sternal recumbency and time to stand up were registered as soon as evident. Biochemical and metabolic profiles during the first 2 days of life (birth, 24 h, 48 h) were determined. Plasma concentrations of IGF-I, cortisol and thyroid hormones were investigated for the first 14 days of life. No significant differences between calves from spontaneous parturition and from caesarean section were found concerning clinical features at birth and during neonatal period (chapter 7). Many differences between the two groups were found regarding some biochemical, metabolic and hormonal parameters. These fast changes in biochemical and metabolic parameters in the newborn calf are probably due to the maturational processes of liver, kidney and metabolism for adaptation to the extra uterine life; basing on our data, the caesarean section seems to entail a lower physical effort for calves during birth, and a slower or delayed adaptational process. In the second study (chapter 10) the plasmatic profile of prostaglandin F2α was determined in 10 newborn calves from spontaneous parturition, and compared with those from neonates of other animal species. Plasmatic levels of prostaglandin metabolite in calves remained high for the first 3 hours of life, unlike newborn horse and donkey foals, in which the metabolite already decreased at 30 minutes after birth. Differences in placentation type or in gestation length could be the reason for the difference between these species. In the third study (chapter 11) the hematological profile of the newborn calves during the first 14 days of life was investigated in relation to the type of delivery. Data from 16 Holstein Friesian calves from spontaneous parturition and from 25 Belgian White and Blue calves from caesarean section were compared. Differences were found regarding many parameters; red blood cells count was always higher in the CS group, as hemoglobin concentrations and hematocrit levels. White blood cells count was higher in the CS group at birth and at 14 days after birth, and it was due to an higher neutrophil count. Different type of delivery can lead to different degree of stress and oxygenation in the newborn, which can represent the reason for variation in hematological pattern; difference in breed could anyway also play a role in this. In the fourth study (chapter 12) a new acute phase protein (PON1) was investigated in newborn calves from spontaneous parturition, and in calves up to 120 days old. Samples from some calves with inflammation were examined and compared with those of age-matched controls. The profile of PON1 activity in the newborn calves was characterized by a gradual increase starting from day 3 of life, probably due to maturation of hepatic system; this result evidences the importance to establish age-related reference intervals. In sick calves, PON1 was significantly lower than in age-matched controls, confirming the role of PON1 as a negative acute phase protein also in calves. From this thesis, the following general conclusion can be drawn: - during the first minutes, hours and days after delivery, a wide number of physiological changes take place in the newborn calf; - circulating levels of many hormones, which are responsible for maturation and adaptation of the neonate, rapidly change with age; most of these hormones reach stable values after the first 24 hours of life, so that the first day after birth has a key role in the adaptational process of the newborn to the extra uterine life; - prostaglandins F2α metabolite plasma concentrations in the newborn calf remain high for the first 3 hours of life, unlike newborn horse and donkey foals, in which the metabolite already decreased at 30 minutes after birth. Differences in placentation type or in gestation length could be the reason for the difference between these species; - PON1 activity in the newborn calves is characterized by a gradual increase starting from day 3 of life, probably due to maturation of hepatic system; this result evidences the importance to establish age-related reference intervals; - in sick calves, PON1 is significantly lower than in age-matched controls, confirming the role of PON1 as a negative acute phase protein also in calves; - the type of delivery does not seem to influence the immediate clinical conditions of the newborn calf, above all in terms of viability; - the type of delivery seems to influence the biochemical, metabolic, haematological and hormonal profiles of the newborn calf: these differences are probably due to a different stress stimulation, which is normally lower during elective caesarean section.