Weaning and other common production practices may have negative consequences on pig health and performance. Many physical aspects of a pig’s environment also may impact its overall well-being. 

Light is probably the most ignored physical aspect of a pig’s environment because the general belief is that pigs are less sensitive to light than some other species.  In fact, there is no particular lighting schedule recommended for pigs.  However, a defined lighting schedule may provide a non-invasive and easy management tool that could be used throughout different production stages.         

Over the years, research results related to light have provided conflicting messages. Does day length influence reproduction, physiology and performance of pigs?  The jury is still out.

Recent research results suggest that a set lighting schedule may improve pigs’ productivity and immune function. Many producers in Europe (specifically Denmark) use a 16-hour lighting schedule in the breeding and gestation areas. Our research has shown that a short exposure, either 8 hours or 16 hours, of light during gestation can influence sow physiology and performance. But perhaps more importantly, it has shown an impact on the piglets’ physiology. 

Data from our University of Illinois laboratory show that lighting can impact piglet performance and physiology based on the pig’s age at weaning. We looked at the effect of 250 lux, provided at the pig’s eye level.

Body weight and immune responses in pigs that are weaned early (14 days old) and late (28 days old) were affected by the amount of light they received. More specifically, the amount of light that a piglet was exposed to influenced its immune response until at least 10 weeks of age (the end of the study).  It is important to note that there was a strong interaction between the pig’s age and its response to light exposure in terms of impacting various aspects of its immune system.

For example, the ability of the immune cells — which are responsible for producing antibodies (B-cells) — to divide is stimulated by 8 hours of light on pigs by 8 weeks of age. Pigs weaned at 14 days of age and exposed to only 8 hours of light have higher B-cell responses than their counterparts that were weaned at 14 days but kept on 16 hours of light. Conversely, pigs that were weaned at 28 days of age and received 16 hours of light had higher total lymphocyte numbers and a greater percentage of  T-cells dividing.  It is apparent that weaning age and the amount of light exposure can influence different aspects of the growing pig’s immune system in different ways.

Our data also show that using light manipulation is not only influenced by weaning age and the amount of light exposure, but also the physiological measure that you want to manipulate.  For example, if a pig is weaned at 14 days old, by the time it reaches 10 weeks old, receiving 16 hours of light will increase its body weight gain.

However, if pigs are weaned at 14 days of age and exposed to 8 hours of light until they are 6 weeks old, their stimulated immune response comes at the cost of growth.  Thus, it may seem more logical to subject these pigs to 8 hours of light until they are 6 weeks old, then switch them to 16 hours of light to enhance their productivity and other immune system responses to benefit the piglets.

Pigs that were weaned at 28 days old and kept on 16 hours of light gained more body weight until they reached 10 weeks of age than did any other group of pigs that we studied. They also had a different (more balanced) immune profile throughout the study.

Despite the potential use of light as a management tool, it is important that we understand whether or not immune stimulation benefits the pig as it faces health challenges throughout its life. That question remains to be resolved; more research is needed to define the ideal lighting schedule in the various production phases.

In the meantime, it may be worth exposing pigs in confinement facilities to more lighting than they currently receive. At least make sure that light intensity is consistent across the entire barn. For example, the level should be more than 50 lux (like a bright, clear day) at the pig’s eye level.