We investigated the effect of feeding time on behavior and stress responses in pregnant sows under isocaloric conditions. Twenty-four sows were balanced for parity and randomly assigned to 1 of 3 feeding times. Corn-soybean meal-based diet was fed once at: 0730 (Control, T1), 1130 (T2), and 1530 h (T3). On average, sows received 7062 kcal ME/d from 2.20 kg of diet formulated to contain SID Lys/ME of 1.71 g/Mcal. The study was conducted for 28 days (21 d acclimation to the feeding regime and 7 days data collection). Saliva samples were collected every 2 hours for 12 hr in stalls on day 52 of pregnancy. Behavior data were collected 24 hr for 7 d from day 53 of gestating by affixing a remote insights ear tag to each sow. Each sow had 120,960 data points categorized into: "Active", "Feed" or "Dormant". Due to housing constraint, all sows were housed in individual stalls in the same barn presenting a potential limitation of the study. Data were analyzed using PROC MIXED and GLIMMIX procedures of SAS 9.4 for cortisol and behavior 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. A 12-hr cortisol total area under the curve (AUC) for sows fed once daily at 1130 h was reduced relative to sow group fed at 1530 h (P = 0.046) but similar compared with the control sows (P = 0. 323). The control sows (0730 h) had reduced total (P < 0.001) and feeding (P = 0.001) activity AUCs relative to sows on 1130 but did not differ compared with sows on 1530 h feeding schedules (P > 0.100). Sows on 1130 h feeding schedule had greater feed anticipatory activity (FAA), 24-hr total activity count, total (P < 0.001) and feeding (P < 0.001) activity AUC compared with sows fed daily at 1530 h. In conclusion, feeding pregnant sows earlier in the morning (0730 h) appears to minimize sows’ behavior but similar cortisol response. Sows on 1130 h feeding schedule had greater activities but reduced cortisol concentration, suggesting that elevated sow activity might not necessarily indicate activation of hypothalamic-pituitary-adrenal axis.

Investigated the effect of feeding time on behavior and stress responses in pregnant sows under isocaloric conditions. Eighteen sows (Landrace × Yorkshire); BW 248.6 ± 2.8 kg; parity 3.30 ± 0.39); were blocked by parity and randomly assigned to 1 of 3 feeding times. Corn-soybean meal-based diet was fed once at: 0730 (Control, T1), 1130 (T2), 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 every 2 h for 12 h in stalls on d 52 of pregnancy and assayed for cortisol using ELISA technique. Behavior data were collected 24 h for 7 d from d 53 of gestation by affixing a Remote Insights ear tag to each sow after 21 d adaptation period. Each sow had 120,960 data points categorized into: “Active,” “Feed” or “Dormant”. Data were analyzed using GLIMMIX procedure of SAS 9.4. Statistical significance was set at P ≤ 0.05, and a trend as 0.05 < P ≤ 0.10. Sow was the experimental unit. A 24 h area under the curve (AUC) was estimated by trapezoidal summation method. Adjustment for multiple comparisons was based on Tukey Kramer’s method. Sows fed daily at 0730 had both lower feeding and total activity compared with sows fed at 1130 h (P < 0.02) but similar to sows fed at 1530 h (P > 0.05). Feeding sows at 1130 h daily resulted in reduced cortisol AUC compared with 1530 h fed sows (P < 0.04) but similar to sows fed at 0730 h (P > 0.05). In conclusion, feeding sows daily at 1130 resulted in increased feed and total activity but reduced cortisol concentration, suggesting that elevated sow activity might not necessary indicate activation of hypothalamic-pituitary-adrenal (HPA) axis.

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.

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 &lt; 0.01). Consequently, T2 sows had lower 24-h total activity (P &lt; 0.001) and feeding activities (P &lt; 0.001) AUC compared with both the control and T3 sows, respectively. The T3 sows had greater FAA (P &lt; 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.