9 Behavioral and stress responses to feeding frequency in pregnant sows under isocaloric conditions

Abstract

Abstract The objective of this study was to investigate behavioral and stress responses to feeding frequency in pregnant sows under isocaloric conditions. Eighteen sows (Landrace × Yorkshire); BW 226.10 ± 1.29 kg; parity 3.1 ± 0.42); were blocked by 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)]” and then “[one-third portion at 0730, 1130, and 1530 h (T3)]”. On average, sows received 7190 kcal ME d−1 during gestation from 2.25 kg of diet formulated to contain SID Lys/ME of 1.71 g/Mcal. Saliva samples were collected from 0630 to 1830 h, 2 hrs apart and assayed for cortisol using ELISA technique. 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”. The data were analyzed using GLIMMIX procedure of SAS 9.4 with treatment as fixed effect and sow as random effect. Results were considered statistically significant when P < 0·05 and were considered as trends when P ≤ 0·10. Sow was the experimental unit. A 24 h area under the curve (AUC) was calculated by trapezoidal method. The P-values were adjusted for multiplicity based on Tukey Kramer’s method. A 24 h total activity and total feeding activity AUC were reduced in sows fed 2× daily compared with sows fed 1× and 3× daily (P < 0.01). A 12 h cortisol AUC was lower for sows fed 2× daily relative to treatment groups fed 1× and 3× daily (P < 0.02). In conclusion, feeding pregnant sows twice daily may improve sow welfare by reducing feeding activity, total activity, and the activation of hypothalamic-pituitary-adrenal (HPA) axis.