Plasma Acyl Ghrelin and Non-Esterified Fatty Acids Are the Best Indicators for Hunger Status in Pregnant Gilts

In the present study, 3 different feeding levels were used to create different hunger status in pregnant gilts. Plasma hormones related to energy homeostasis and non-esterified fatty acids (NEFA) were analyzed to quantify their response to different feeding levels. A total of 18 gilts fitted with permanent cephalic vein catheters were allotted to 1 of 3 dietary treatments using a completely randomized design. All gilts were fed one common corn-soybean meal-based diet with the amount being 1.0 × maintenance energy intake (100 × BW (BW)^0.75 kcal ME/d) throughout gestation except 3 periods of 7 d when dietary treatments were imposed on d 27, 55 and 83 of gestation. During the 3 short periods, sows were fed 1 of 3 different feeding levels: 0.5, 1.0 and 2.0 × maintenance energy level (0.5M, 1.0M and 2.0M, respectively). During period 1 (d 27-34), serial blood samples were collected at the last day after 6 d adaptation. Results showed that during gestation period 1, BW and backfat (BF) changes were higher (P < 0.01) for gilts on 2.0M than gilts on 0.5M feeding level. Plasma ghrelin concentrations showed a relatively flat pattern during the 24 h period. Generally, plasma ghrelin and NEFA concentrations and the area under curves (AUC) were greater (P < 0.05) in gilts on 0.5M feeding level than those on 2.0M feeding level. Additionally, consumption time for 1.82 kg feed at d 35 of gestation was longer (P < 0.01) in gilts fed 2.0M feeding level during d 27 to 34 of gestation than those on 0.5M feeding level. Simple linear regression results showed that AUC of acyl ghrelin was the best predictor for prediction of consumption time, whereas AUC of NEFA was the best predictor for prediction of BW or BF change during d 27 to 34 of gestation. In conclusion, our data suggested that a relative flat pattern existed in pregnant gilts in terms of diurnal plasma profile of acyl ghrelin and that 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. AUC of acyl ghrelin and NEFA seemed to be the best predictors for hunger status of pregnant gilts. This study provided insight to evaluate the hunger status in pregnant sows, which could be used as a reference to improve the welfare of gestation sows.