Behavioral and cortisol responses to feeding frequency in pregnant sows under isocaloric intake

Abstract

The study focused on behavioral and cortisol responses to feeding frequency in pregnant sows under iso-caloric intake. Twenty-four sows [(Landrace × Yorkshire); BW 216.70 ± 3.98 kg; parity 3.04 ± 0.53] were balanced for parity and randomly assigned to 1 of 3 feeding frequency regimes. Sows were fed corn-soybean meal-based diet 1× [0730 (Control), T1], 2× [half ration at 0730 and 1530 h, T2], or 3× [one third portion at 0730, 1130, and 1530 h, T3] from days 30 to 60 of gestation. Sows received 7055 kcal ME/d during gestation from 2.21 kg of diet formulated to contain SID Lys/ME of 1.71 g/Mcal. Saliva samples were collected every 2 hours from 0630 to 1830 h on d 52 and assayed for cortisol using ELISA procedure. Behavior data were collected for 7 d from d 53 of gestation by affixing a remote insights ear tag to each sow. Each sow had 120,960 data points categorized into: "Active", "Feed" or "Dormant". Because of housing constraint, all sows were housed in individual stalls in the same room presenting a potential limitation of the study. The data were analyzed using PROC MIXED and GLIMMIX procedures of SAS 9.4 for cortisol and behavior count data, respectively. Sow was the experimental unit. The area under the curve (AUC) is quantitative evaluation of response as threshold varies over all possible values. The T2 sows had reduced 12-h cortisol AUC compared with control sows (P = 0.024) and T3 sows (P = 0.004), respectively. The T2 sows had lower 3-h (P = 0.039) and 5-h (P = 0.015) post-feeding cortisol AUC compared with control sows. Feed anticipatory activity (FAA), 24-h total activity, and feeding activities (eating and/or sham chewing) were reduced for T2 sows relative to the control and T3 sows (P < 0.01). Consequently, T2 sows had lower 24-h total activity (P < 0.001) and feeding activities (P < 0.001) AUC compared with both the control and T3 sows, respectively. The T3 sows had greater FAA (P < 0.001) and 24-hour total activity AUC (P = 0.010) compared with control sows. Our data although inconclusive due to small sample size, twice daily feeding appears to be the threshold that reduces sows’ total activity AUC, feeding activity AUC, and activation of HPA axis, reduced hunger, and exhibit potential to improve sow welfare in relation to once and thrice daily feeding regimes under iso-caloric intake per kilogram live metabolic weight.