All you can eat? Ad libitum feeding patterns of lactating sows

Knowing how much and when a sow chooses to eat and what influences her choices provides an opportunity to optimise feeding strategies and improve welfare. Across three farms, we thus examined the ad libitum feeding patterns of a total of 82 lactating sows and the respective effects of internal and external factors. We hypothesised sows to feed more as days of lactation and number of weaned piglets increased and with lower relative weight loss, to exhibit a diurnal feeding pattern, and to shift their feeding times with temperature/humidity. Sows could obtain feed by triggering the sensor of a computer-controlled feeder. From lactation day 6 on, feed allowance was increased stepwise to ad libitum and feeding behaviour was investigated using time-resolved records of feed obtained and analysed for two farms using linear mixed models. Feed obtained per day increased with day of lactation (p < 0.001), the number of weaned piglets (p = 0.001), and a decrease in relative weight loss (p < 0.001). Furthermore, it was affected by interactions between farm and lactation stage (p < 0.001) as well as temperature-humidty-index (THI) and lactation stage (p = 0.02). Daily feeding patterns varied between sows, as they exercised their ability to choose their feeding times, yielding two to three feeding peaks throughout the day. Taken together, these findings highlight the complexity of lactating sows’ feeding patterns as well as how sensor-triggered, computer-controlled ad libitum feeders allow lactating sows individual choice over their feed delivery.