Plasma acyl ghrelin and nonesterified fatty acids are the best predictors for hunger status in pregnant gilts

Sows are usually restricted fed during pregnancy to maximize their reproductive efficiency, which may predispose sows to a state of hunger. However, an objective measurement of hunger status has not been established. In the present study, we examined the correlation of plasma hormones and NEFA and selected the best predictors for hunger status using pregnant gilts. Three different levels of feed intake (0.5, 1.0 and 2.0 × maintenance energy intake [0.5M, 1.0M and 2.0M, respectively]) were imposed from Day 28 to 34 of gestation to create different hunger statuses in pregnant gilts. Plasma hormones related to energy homeostasis and NEFA were analyzed to quantify their response to different levels of feed intake. A total of 18 gilts (197.53 ± 6.41 kg) were allotted to 1 of 3 dietary treatments using a completely randomized design. Results showed that BW change, ADG, and G:F from Day 28 to 34 of gestation were higher (P < 0.01) for gilts on the 2.0M feeding level than for gilts on the 0.5M feeding level. Plasma acyl ghrelin concentrations showed a relatively flat pattern during the 24-h period. Plasma acyl ghrelin and NEFA concentrations and areas under the curve (AUC) were greater (P < 0.05) in gilts on the 0.5M level of feed intake than in those on the 2.0M level of feed intake. No differences were observed among the 3 feeding levels in terms of plasma glucagon-like peptide 1 and leptin concentrations. Additionally, consumption time for 1.82 kg feed on Day 35 of gestation was longer (P < 0.01) in gilts fed the 2.0M level of feed intake from Day 28 to 34 of gestation than in those on the 0.5M level of feed intake. Simple linear regression results showed that the AUC of acyl ghrelin was the best predictor for consumption time (R² = 0.82), whereas the AUC of NEFA was the best predictor for BW (R² = 0.55) or backfat change (R² = 0.42) from Day 28 to 34 of gestation. In conclusion, our data suggested that a relative flat pattern existed in pregnant gilts in terms of the diurnal plasma profile of acyl ghrelin and that the level of feed intake of pregnant gilts was negatively correlated with plasma concentrations of acyl ghrelin and NEFA, which, in turn, were negatively associated with feed consumption time. The AUC of acyl ghrelin and NEFA seemed to be the best predictors for hunger status of pregnant gilts.