Importance of the vitality on the performance of the piglets

The lactation is one of the most important stages in pig production due to the high piglet mortality recorded during its length, reaching average values of up to an 18% of losses with respect to the total number of piglets born (BDporc and the “Observatori del porcí” [Swine Observatory] of the Catalonian Regional Government Ministry of Agriculture, Farming and Fisheries).

In practice, a wide variety of handling practices implemented directly on the piglets in order to reduce their mortality are carried out. During the first hours of life we find ourselves with adoption policies of piglets between litters, oral colostrum/commercial product supplementation, etc. that can be carried out in different ways and following different criteria according to the characteristics of the farm and of the available staff.

All these measures take mainly as their only criterion the size or the weight of the piglet.

Nevertheless, it is frequent to see how piglets that we consider as small show a performance that is as good or even better than that of siblings with a bigger size under the same conditions or in a same litter. This demonstrates us that, regardless that the weight is the most deciding factor, there are other traits of the piglet that can have an influence when making the decisions about its handling. One of these traits is vitality, defined as the vigour of physical strength. The vitality of the piglet will have a direct influence on its ability to compete for a nipple and consume colostrum/milk. It is expectable that vitality is very related to viability, that is defined as the ability to survive with an adequate growth. Until now, at a scientific level, the vitality of the piglets has been studied in the moment of their birth. First, the pigs were provided with an adaptation of a vitality index used in human medicine oriented towards the evaluation of the degree of hypoxia. Later on, more factors were considered, as for instance the partial oxygen pressure in blood, the ability of standing up after being born, the time interval from the birth until the first consumption of colostrum, etc. In the great majority of the cases viability has been studied to better understand the bearing of the hypoxia problems during birth on the neonatal viability of the piglets, and little has been studied about its influence or relationship with the performance of the animals until the end of the lactation period.

Recently we have carried out a study in a farm, under commercial conditions, in which we tried to evaluate, objectively, the vitality of the piglets once the birth had ended from the observation of the behaviour and trying to relate it to the pre-weaning growth and mortality.

Table 1: Description of the evaluated behavioural parameters and their scoring

Introducing the piglets in a 55 cm diameter bucket for 30 seconds and without interacting with it, the two behavioural parameters presented in Table 1 were evaluated:

• M) Mobility of the piglet: this parameter was included with the intention of evaluating, indirectly, the ability of the piglet to move in order to reach the udder and/or escape from under the sow when she lays down. These qualities can be related to a higher colostrum/milk consumption and to a higher survival rate.
• U) Stimulation of the udder: this parameter was included with the intention of evaluating, indirectly, the ability of the piglet for suckling and stimulating the udder (carrying out, inside the bucket, of an oscillatory head movement similar to the rooting or the exploring action).

The relationship between the score obtained in the behavioural test (the sum of the U and M points) during a period of 30 seconds and the growth and the survival of the piglets was checked. In the first place, it was seen that the result in the vitality test was not related to the weight of the piglet, confirming its higher relationship with the neuronal and/or metabolic development that, in turn, can be influenced by the course of the birth. The result of the test was not necessarily better for having a higher weight or a bigger size. In the second place, we saw that the vitality can have an influence on the growth of the piglets. In general, the piglets with a higher score in the test showed a better growth along the lactation. In the same way, it was also confirmed that the higher the score, the better the probability of surviving during the lactation.

Other factors were also studied, and in this way it was confirmed, as it is well-known, that the factor with the highest influence on the growth ability and the survival rate of the piglets is their weight at birth. In closing, the sow responsible for nursing the piglets, the mean weight of the litter to which the piglet pertains and the thermoregulatory ability of the piglet will condition, to a lesser extent, the performance of the piglet.

The study, as well as corroborating the importance of the weight of the piglet at birth, the homogeneity of the litter and the good milk producing ability of the sow as the main factors responsible for the performance of the piglets, also points out the vitality of the piglets, evaluated through a method that is easy and quick to obtain in situ and from the animal. Although not having at our disposal studies on the efficacy of the test as a tool for the classification of the piglets, a simple evaluation of the motor skills and of the presence of "exploratory movement" of the piglet placing it on the floor for a few seconds could contribute to the decision making about if it is necessary to reject an animal with a low weight or if we have to place a piglet with an intermediate weight in a litter with siblings with a higher or a lower weight (just to put a couple of examples), that are situations in which the information about the weight or the size of the animal may not always be enough.