Swine Vision and Lighting

ANATOMY AND PHYSIOLOGY OF THE SWINE EYE

• Similar size eye to humans - ~24 mm diameter
• Pupil size is 5 - 11 mm—Larger than humans
• Pupil is round whereas most ungulates are oval or slits
• Pigs not adapted to bright sunlight
• Iris is blue to dark brown in color in domestic swine
• 310 degree field of vision with blind spot directly behind the body.  Binocular view is 35 - 50 degrees
• Not sensitive to ultraviolet light
• Pigs are near-sighted vs humans
• Visual acuity is ~1/6 or less vs humans

Other Senses:

• Very sensitive sense of smell
• Sense of taste similar to humans
• Sweet, Sour, Salty, Bitter
• Prefer sweet to sour
• Hearing similar to humans
• Greater sensitivity in the ultrasonic range
• Communication is by grunts that vary in frequency, tone, and magnitude

SPECTRAL SENSITIVITY OF PIGS

Pigs have 2 cones

• Blue—Peak sensitivity at about 439 nm
• Green-Yellow—Peak sensitivity at about 556 nm

Pigs are red/green color blind—unable to distinguish red from green colors

LIGHTING RECOMMENDATIONS FOR SWINE

Farrowing Sows and Piglets

Bright lights with longer photoperiods showed an increase in litter size, heavier pigs, healthier piglets with a better immune response, with little effect on sow behavior (nursing interval, duration of nursing, or sitting/standing/lying behavior).     

—> Long day, bright light (16 - 20 hour photoperiod, 70+ lux)

Growing-Finishing Pigs

Pigs prefer to urinate and defecate in bright light, rest in dim light.  A 14 hour photoperiod showed increased weight gain and improved FCR and 80 lux showed better welfare and fewer agonistic interactions than 40 lux without affecting production

—> 14 hour photoperiod, 80 lux, dimmer light over resting area

Breeding Gilts and Sows

Illuminance has little effect on the maturation of gilts, but a significant effect in boars.  Short photoperiods encourage the onset of puberty in gilts and decrease the weaning to estrus interval in sows.  A low CRI has little effect on pigs but limited the ability of caretakers to detect changes in redness of the vulva for estrus or farrowing detection

—> Short or decreasing photoperiod and bright enough to work comfortably and detect estrus with a high CRI light source

Boars

A short photoperiod encourages puberty and results in higher steroid production, increased sperm count, and increased libido and also increases volume of ejaculation and number of sperm per ejaculate

—> Short photoperiod, dim light

_References

_{Dalmau, Antoni, Pol Llonch, Antonio Velarde.  Pig vision and management/handling.  www.pig333.com.}

_{Li, Yuzhi. (2014).  Normal and abnormal behaviours of swine under production conditions.  The Pig Site.}

_{Neitz, J., & Jacobs, G. H. (1989). Spectral sensitivity of cones in an ungulate. Visual Neuroscience, 2(2), 97–100.}

_{Taylor, N. (2010). Lighting for Pig Units. http://pork.ahdb.org.uk/media/39814/lighting-for-pig-units-final-report.pdf}

_{Taylor, N., Prescott, N., Perry, G., Potter, M., Sueur, C. L., & Wathes, C. (2006). Preference of growing pigs for illuminance. Applied Animal Behaviour Science, 96(1–2), 19–31. https://doi.org/10.1016/j.applanim.2005.04.016}