By: Dinesh Thekkoot PhD, Genesus Inc.

Factors Affecting Preweaning Piglet Mortality
Part 1

Generally, it’s difficult to attribute a single cause to preweaning mortality (PWM). Various predisposing causes and their complex interactions lead to PWM (Figure 1). These predisposing factors can be broadly classified into (A) Sow factors (B) Piglet factors and (C) Environmental factors.

Unraveling these complex interactions to find out the primary cause is an important step in decreasing PWM.

Figure 1: Predisposing factors of piglet pre-weaning mortality (Adopted from Edwards and Baxter, 2015)

A. Sow factors

The dam provides the fetus/piglet vital resources in-utero, at farrowing, and during lactation and thereby plays a pivotal role in the survival of the piglets till weaning. Sow genotype, parity, nutrition, and physical condition during gestation and lactation can also influence the resource mobilization to the piglet, and thereby can affect PWM.

Figure 1: Predisposing factors of piglet pre-weaning mortality (Adopted from Edwards and Baxter, 2015)

A. Sow factors

The dam provides the fetus/piglet vital resources in-utero, at farrowing, and during lactation and thereby plays a pivotal role in the survival of the piglets till weaning. Sow genotype, parity, nutrition, and physical condition during gestation and lactation can also influence the resource mobilization to the piglet, and thereby can affect PWM.

B. Piglet factors

These are factors that are caused mainly by physical or behavioral issues with piglets

1. Bodyweight, maturity and vigor: Body weight is considered as the single most important factor that determines piglet survival. A study published by Roehe and Kalm (2000), reported that pre-weaning mortality rates were around 40% for piglets weighing less than 1 kg, 15% for piglets weighing between 1 to 1.2 kg and only 7% for piglets above 1.6 kg. Along with size, degree of development or maturity also plays an important role in survival. Piglets that have undergone intra uterine growth retardation (IUGR), have a lesser chance of survival even if they fall in the higher body weight range. Immature piglets with underdeveloped digestive or other internal organs, even if they can achieve early ingestion of colostrum, can die due to a lack of a piglet’s ability to absorb/digest colostrum. Vigor or vitality of the piglet describes the survival behavior of the piglet, and piglets that are quicker to reach the udder, find a teat and ingest colostrum, have a higher chance of survival.
2. Gender: Baxter et al (2012) reported that even though male piglets were born heavier and with higher body mass index (birth weight/crown-rump length) than females, they tend to suffer more from crushing and have a significantly lower chance of survival until weaning than females.
3. Thermoregulatory abilities: The capability of the newborn piglet to produce metabolic (body) heat depends on the coordinated activities of various organs and is crucial for the survival of piglets. This is vital, especially in colder environments. If the body temperature drops and becomes irreversible, then the piglet will die of hypothermia or will become more susceptible to secondary factors like crushing. The thermoregulatory mechanism is more important for the survival of piglets with low birthweight as heat loss per unit of body weight is inversely proportional to body size (Herpin et al 2002)

C. Environmental factors

1. Thermoregulation of the environment: The thermal comfort zone of piglets and sow are markedly different. The lower critical temperature of a newborn piglet is around 34oC (93.2oF) and the thermal comfort zone for the sow is between 12-22oC (53.6 – 71.6oF). Creating an environment in which newborn piglets are above their lower critical temperature provides one of the biggest challenges in the farrowing pen.
2. Competition: This challenge comes from the social environment, and if not managed well by employing strategies like split suckling within the first 24 to 48 hours of birth, low birth weight piglets, regardless of their vigor will be at risk of starvation. The situation is complicated by an increased within litter birth weight variation.
3. Caretaker influence: The person managing the farrowing rooms also plays a role in controlling PWM. Some of these factors are environmental temperature, barn airflow, intervention in farrowing when required, provide assistance to weak piglets with colostrum, proper hygiene, treatment protocols, etc.

All these factors, independently or in combination lead to PWM, and it requires various management, and selection strategies to reduce it. Pre weaning mortality does have a genetic component, and in the last part of this series, we will discuss in detail the genetic selection strategies that Genesus has adopted to reduce it.

References:
Baxter et al (2012) The Weaker Sex? The Propensity for Male-Biased Piglet Mortality. PLoS ONE 7(1)
Devillers et al (2011). Influence of colostrum intake on piglet survival and immunity. Animal 5: 1605-1612.
Edwards et al. (2015). Piglet mortality: Causes and prevention. The Gestating and Lactating Sow. 253-278
Herpin et al (2002). Development of thermoregulation and neonatal survival in pigs. Livestock Production Science 78: 25-45.
Roehe et al. (2000). Estimation of genetic and environmental risk factors associated with pre-weaning mortality in piglets using generalized linear mixed models. Animal Science, 70(2), 227-240

Integrating Commercial Data into Genetic Improvement

Production traits of interest in the commercial level can’t always be measured or measured accurately at the nucleus level.

We invite you to watch the presentation below “Integrating Commercial Data into Genetic Improvement” by Dr. Bob Kemp, Vice President Research and Development, Genesus Inc. and learn how Genesus Genetics uses this approach to improve commercial production performance.