Neonatal mortality, as an economic and animal welfare problem

Neonatal piglet mortality is a major economic and animal welfare problem. The percentage of neonatal mortality varies greatly between farms, ranging between 5 and 35%. Deaths occur mainly during the first 48 hours after farrowing, with sow squashing the leading cause of mortality.

However, neonatal piglet mortality is the result of a set of complex interactions between sow, piglets and the environment, so identifying a single cause is often very difficult.

THE HYPOTHERMIA COMPLEX – STARVATION – CRUSHING

Interactions that occur in the hypothermia – starvation – crush complex (modified from Edwards, 2002)

Although several studies identify sow squashing as one of the leading causes of piglet death, squashing is very often the result of the combined effects of sow. perinatal hypothermia and the starvation. Malnourished piglets spend more time near the sow and are more likely to be crushed.

The newborn piglet’s immune system is immature, so ingestion of colostrum (which is a source of energy and immunoglobulins) before 36 hours postpartum is essential for its survival. Starvation, which is usually secondary to neonatal hypothermia, makes piglets even more lethargic and less able to compete with their littermates for access to the city.

The lower critical temperature of newborn piglets is 34ºC and when the ambient temperature is lower, the piglets will try to warm themselves by shivering and huddling. Interestingly, one of the reasons newborn piglets are so sensitive to cold is that they lack brown adipose tissue.

IMPORTANCE OF THE VIGOR OF THE PIGLET AND THE WEIGHT AT BIRTH

Once the body reserves and thermoregulation capacity are guaranteed, the most important factor for the survival of the piglet is its vigor just after birth. The vigor of the newborn piglet can be measured by behavioral observations, such as the time it takes to access the udder, and physiological parameters such as muscle tone.

The vigor can vary considerably between piglets of the same litter and this variability depends largely on the degree of hypoxia at birth. Piglets born last and those born longer farrowing are more prone to hypoxia. Neonatal asphyxia can lead to severe acidosis and it has significant negative consequences.

Various problems such as lack of vigor, inability to regulate body temperature, failure to passively transfer immunity, increased susceptibility to infection, and poor productive performance are associated with a state of neonatal asphyxia and acidosis.

Piglets with a low birth weight they present both an increased risk of mortality and reduced growth during lactation. Thus, piglets weighing less than 1 kg at birth have a higher risk of dying before being weaned.

BREAST-FEEDING

A breastfeeding lasts between 2 and 3 minutes, while the milk ejection is completed in 10 – 20 seconds. Piglets from the same litter suckle simultaneously every 30 to 70 minutes and up to 20 times a day. A breastfeeding includes five different phases:

In the first three phases a communication process is established between the sow and her litter to ensure that the piglets are at the udder when milk ejection begins. The sow lies down, exposes the udder and makes a series of growls with increasing frequency.

Piglets compete for access to the udder (phase 1), massage the udder rhythmically (phase 2) and stimulate the mother’s oxytocin release by performing slow sucking movements (step 3).

The fourth phase consists of the ejection of milk. During this phase, the sow increases the frequency of grunting and the piglets perform rapid sucking movements.

During the fifth stage, which occurs after ejection, the piglets massage the udder and perform slow sucking movements. It has been suggested that in this phase the piglets stimulate the synthesis of milk that they will consume in the next episode of suckling. During the fifth phase of suckling, the sow decreases the frequency of her grunts.

Both vitality and birth weight determine the degree of udder stimulation and consequently the amount of milk consumed.

“The lack of vigor of the piglet and a reduced maternal behavior are the main causes of neonatal mortality”

CONDUCTA MATERNAL

Several elements of maternal behavior are relevant to the survival of the piglet. The nesting behavior it is important not only for the delivery itself, but also for the expression of appropriate behavior during and after delivery. The correct expression of nesting behavior has been associated with a lower mortality rate during lactation and an increase in the duration of suckling episodes.

A restless sow it is more likely to crush its piglets, which also have more difficulty locating the udder and ingesting colostrum or milk, with the consequent increase in neonatal mortality. Crushing usually occurs when the sow lies down from a standing or sitting position, when sitting up after lying down, or when turning on herself.

The speed and nature of the movements carried out by the sow largely depend on the “quality” of her maternal behavior. Sows that do not crush any of their piglets show a more developed maternal behavior: they carry out the nesting behavior for longer or with more intensity, respond more quickly to the vocalizations emitted by the piglets and sniff them more frequently.