Controlling stillbirth losses: Global Problem

In general, as total litter size has increased, there has been a tendency for an increase in the percentage of piglets born dead. It is now quite common to see an average stillbirth rate of 1.0 piglets per litter, or even more, in data from individual farms and herd recording schemes. This presents an opportunity to improve Weaning Capacity by reducing the level of stillbirths through a sound genetic program and good management procedures.

The Hypor genetic program includes selection for numbers born alive per litter, in addition to total numbers born, which makes a significant contribution to keeping stillbirths at a reasonable level. A focus on litter size alone presents the risk of lowering birth weights and decreased uniformity. Litter size and piglet quality traits tend to be negatively correlated. Focusing a breeding and selection program on a single trait would indirectly push other negatively correlated traits in an undesirable direction.

Birth weight is a trait that plays a major role when we consider piglet quality and survival. Traits like average birth weight and total birth weight have relatively high heritabilities, 0.25 and 0.15, respectively. Small piglets (<800 grams) and non-uniform litters also have high heritabilities, meaning there is the potential for genetic improvement. Traits such as number of small piglets and uniformity of litter at birth have a heritability of 0.10 and 0.07, respectively.

Good management vital

Applying the correct management procedures before and during the farrowing process can also have a major impact. A reduction of 0.3 in the number of stillborn pigs per litter, which is relatively easy to achieve on most farms, will result in about 1.4 more piglets weaned per sow lifetime and an increase in Weaning Capacity of nearly 10kg.

Stillbirths are defined as those piglets that die during the farrowing process because their placental blood supply through the umbilicus is restricted or cut off by the contractions of the uterus and therefore they are asphyxiated. There are a number of factors that influence stillbirth rate, most of them related to the sow and the farrowing process. Parity has the biggest effect because stillbirths increase steadily after the second litter and are highest in sows of parity 6 or more. Sows that produce large litters tend to have more still born piglets and also those that have had one or more stillbirths in a previous litter have an increased risk in subsequent litters.

Stillbirth rate is closely related to the time taken to farrow, which is usually in the range 2-5 hours, although most sows farrow within 2-3 hours. A longer farrowing time is associated with higher stillbirths because the risk of umbilical blood flow being disrupted increases over time. The other major factor involved is the stage of farrowing, because almost all stillbirths occur in the last third of farrowing and 70% in the last three piglets. In order to make most effective use of time when managing farrowing, the sows that have the highest likelihood of producing stillborn pigs (based on parity, previous history) should be identified and a note made on their farrowing card. This allows greater attention to be given to the highest risk sows, resulting in more effective management.

Supervision

Supervision of farrowing is essential in order to have a significant impact on stillbirth rate and, in most cases, this will require a high percentage of farrowings to be induced. Prior to commencement of this practice, it is important to know the average gestation length for natural farrowings for the herd as a whole and also by parity, because this varies from farm to farm. In order to maximize birth weights, induction should not be carried out too soon relative to the average gestation length.

The Guidelines

The following management procedures can be used to minimize stillbirth rate:

* Once farrowing has started, observe the sow quietly and note the time, number of liveborn piglets and number of stillbirths on the farrowing card each time the sow is checked. Technicians should be well trained in understanding farrowing behaviour so that they can identify and respond to any abnormalities or problems quickly.

* In the earlier stages of farrowing, assistance is rarely needed and unless the sow is having difficulties, or appears uncomfortable, she should be left to farrow on her own.

* When a sow has had 6-7 piglets, assistance should be given when about 20 minutes has elapsed without a piglet being born, or if a stillborn piglet is born. This time can be adjusted, if necessary, on the basis of experience.

* Good hygiene procedures should be observed when assisting sows, including washing the vulva area with warm water and a mild antiseptic and using arm-length plastic gloves lubricated with obstetric gel. Sows that have been assisted should also be given an injection of long-acting antibiotic, following the farm’s Treatment Protocol.

* Technicians should look for the telltale presence of yellow-brown meconium, or piglet faeces, in the sac that surrounds the piglet. This is excreted when piglets are deprived of oxygen in the uterus. If it is seen, it is a good indication that there is a problem and the sow should be assisted immediately.

* When sows are assisted, all piglets that can be reached should be carefully pulled out. Piglets should have any membranes around them removed, be assisted to breathe if necessary, placed under a heat lamp and later assisted to suckle colostrum.

* If farrowing is slow or the sow stops contracting, Oxytocin can be used sparingly to stimulate uterine contractions, once it has been checked that the cervix is clear of obstruction. A maximum dose of 0.5ml or 5 International Units (iu) should be given intramuscularly or, if directed by the farm veterinarian, 2.5 iu injected into the vulva. Administration of Oxytocin may be carried out every 20-30 minutes if required. Using too large a dose of Oxytocin may cause the uterus to “lock up”, leading to more stillborn piglets.

* After a sow has been assisted, she should be closely observed until farrowing is complete and assisted again if necessary.

Work by Scottish researcher Dr. Peter English has shown that when these measures are taken to reduce stillbirths, they also result in an increase in the survival rate of pigs born alive. This is because the incidence of anoxia, or oxygen starvation, which is the primary cause of low viability, is reduced. Herd records show clearly that those herds with a low stillbirth rate have the lowest pre-wean mortality.

Other factors

In addition to management of the farrowing process itself, other management and environmental factors can influence stillbirth rate.

* Overfeeding in the 3-4 days prior to farrowing can lead to increased stillbirths, so it is advisable to reduce the feed allowance to 2.0kg/day for sows and 1.8kg for gilts.

* Excessively high farrowing room temperatures, which result in discomfort for the sow, are also associated with higher stillbirths and the room temperature at farrowing should be 21-22ºC where possible.

* Any situation that results in the sow being stressed or uncomfortable may result in increased stillbirths. In particular, it is very important that staff act in a quiet and calm manner when sows are farrowing because noise and disturbance will lead to stress.

The Hypor Solution

Hypor has made efforts to take into consideration the animal’s biology while defining the breeding goals. This has led to more balanced breeding goals that fit naturally in the future breeding pig. Where we foresee biological limitations, we include those factors in the breeding goal.

Another area that Hypor breeding goals address is the maintenance of traits within sensible ranges. This avoids having traits fall out of a reasonable biological range and having to start fixing them after the fact. An example would be a trait like age at first mating. Breeding perpetually for reduced age at first mating can result in gilts that start cycling before they are physically strong enough to support pregnancy and lactation without negative effects. Consequently our breeding goal is to “optimize” age at first mating and such other traits like interval weaning to mating.

Ultimately the focus in selection is to create more quality piglets with a high total litter weight. Having 15 quality piglets of 1.5 kg average birth weight adds up to 22.5 litter weight. This can only be achieved as a target when piglet quality and birth weights do not get compromised too much while selecting for litter size.

A balanced genetic focus combined with correct management procedures during farrowing will help to realize the genetic potential for high numbers born alive in Hypor sows and gilts. By increasing the number of piglets weaned per litter and consequently the weight of piglets weaned per sow lifetime, attention to stillbirth management can make a valuable contribution to maximizing Weaning Capacity.