Mortality in piglets during the perinatal period, especially the first days after birth, is frequently caused by noninfectious conditions, such as hypoglucemia or low birth weight, which can be associated with hypothermia experienced at birth. The thermal stability of newborn piglets is a fundamental aspect of neonatal care, so maintaining a constant, ideal temperature will substantially reduce newborn mortality. Species-specific characteristics, such as a limited capacity for thermoregulation, low energy reserves, a lack of brown adipose tissue (BAT) (-, and environmental conditions that are adverse for the piglet around the time of birth, including the absence of a microclimate, all of them contribute to difficulties in reaching thermal homeostasis in the first hours post-birth. Shivering thermogenesis and behavioral modifications to regulate body temperature through innate mechanisms allow animals to reduce their energy expenditures. Some body postures are effective in reducing contact with the floor and also nestling are useful to avoid heat loss, and also decreases heat dissipation. Achieving optimal development of thermoregulation is a challenge that newborns must confront to successfully adapt to extrauterine life. The objectives of this review, are to discuss the adverse factors that can lead to a death event due to hypothermia by analyzing the thermoregulation mechanisms at the central and cutaneous levels, also to analyze the harmful impacts that surviving neonate piglets confront in an unfavorable thermal environment, and to describe the pathophysiological mechanisms of death caused by hypothermia.

The objective of this study was to evaluate uterine activity at farrowing in sows with different gestation lengths (GL), and its effect on the metabolic profile, blood gases and daily weight gain of neonate piglets. The experiment covered a period of 25 weeks and involved 200 Yorkshire-Landrace sows. The animals were assigned to four groups of 50 sows each and distributed according to GL, as follows: GL1: 107–109 days; GL2: 110–113 days; GL3: 114–116 days; GL4: 117–119 days. The productive indicators of the sows were recorded, as were the survival outcomes of the neonatal pigs. Fetal cardiac frequency and both intensity and frequency of myometrial contractions were monitored using a Corometrics Fetal monitor. The blood gases, electrolytes and glucose levels of the neonates were obtained by means of an automatic blood gas and electrolyte analyser. The GL groups GL1 and GL2 had more prolonged births (>226.26 ± 4.95 min) regardless of litter size (P < 0.05). Of the four groups, GL1 presented the longest duration (P < 0.05) of the expulsion phase (P < 0.05), the highest number of uterine contractions (P < 0.05), and the highest and lowest number of intra-partum deaths (P < 0.05) and live births, respectively. The live birth piglets in this group had both the lowest birthweights (P < 0.05) and the highest incidences of hypercapnia, hyperlactatemia and hypercalcaemia (P < 0.05), which later resulted in lower rates of daily weight gain (P < 0.05). In conclusion, premature births increase the number of intra-partum deaths and result in lower birthweights, the presence of apnoea, and severe metabolic alterations in piglets.

Labour challenges the newborn to adapt to extrauterine life and survive the troublesome neonatal period. Low vitality is a recurrent problem in veterinary perinatology, and several factors can directly or indirectly culminate in neonatal death. One prime determinant of low vitality in animals is foetal hypoxia resulting from prolonged labour or dystocia. Factors such as foetal acidosis, metabolic and electrolyte imbalances, and asphyxia can quickly lead to neonatal death, while others are a consequence of low vitality in which the weak neonate cannot reach the teat and feed, thermoregulate, or breathe because of airway obstruction by meconium. Neonatal hypoxia can also lead to a failure of passive transfer and neonatal infections. The birth weight, the age of the dam, the size of the litter, and parity are also relevant vitality determinants. Scoring systems, similar to the Apgar score used with human babies, have been modified in veterinary neonatology to identify low vitality neonates in need of medical intervention. This review focuses on the vitality assessments and risk factors associated with neonatal mortality in puppies, calves and piglets. Also reviewed is the relationship of umbilical cord morphology and hypoxia with the premature passing of meconium into the amniotic sac and subsequent aspiration into the lungs. Veterinary literature shows a need to improve Apgar scores in animals by using blood gases and other clinical and laboratory tests. Also, it is necessary to better train veterinarians and personnel to identify low vitality neonates and when necessary to implement a rapid medical intervention.

The facial expressions of animals constitute a means of manifesting emotions, fulfilling functions related to social interactions in several species. Interest has come to use facial expressions as a tool for predicting intentions; in the case of aggression, for example, impeding attacks between individuals prevents negative economic and emotional impacts. Recent research has sought to associate facial expressions with painful events as tail-cropping and castration on the assumption that objective evaluations of the presence or absence of grimaces in pigs' snouts may allow us to determine the intensity of the pain they perceive. Furthermore, to continue developing scales that will complement the existing piglet grimace scale (PGS), which is not yet fully-validated in terms of reliability. Another area of research is interpreting expressions of fear during traumatic events like pre-slaughter handling. Also, the phenomenon of emotional contagion in groups of animals suggests the need to focus on their emotions, since recognizing them could allow us to prevent alterations of meat quality. These approaches reveal the need for a detailed compilation of the facial expressions of pigs based on current scientific literature regarding emotions, alimentation, and pain-related behavioral responses in pigs.

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