Effects of Exogenous Ghrelin on the Behaviors and Performance of Weanling Piglets

The objective of this study was to evaluate the effect of exogenous ghrelin on the behaviors, weight gain, and feed intakes of weanling piglets. A total of 25 pairs of Duroc$\times$Landrace$\times$Large White piglets weaned at 21 days of age were used in this experiment which finished on day 36. Each pair of healthy piglets from the same litter with similar body weight and of the same gender were selected and randomly arranged to ghrelin or control groups. Thus, there were 50 piglets (ghrelin 25; control 25) kept in 10 pens (ghrelin 5; control 5) and 5 piglets per pen. Initial body weight of the pigs did not differ between the control and ghrelin treatment ($7.43{\pm}0.17kg$; p = 0.81). Experimental pigs were infused with ghrelin ($1{\mu}g/d$ pig) via the marginal ear vein between 0750 and 0800 h at 22, 23, 24 days of age. Control pigs were infused with 0.9% saline. Feed consumption was measured on days 23, 24, 25, 29 and 36. Body weight was measured on days 22, 23, 24, 25, 29 and 36. Behavior data of individual piglets were collected by real-time observation from 0800-1500 h through remote supervisory equipment at 22, 23 and 24 days of age. The results indicated that ghrelin infusion could increase drinking (p<0.05) and lying behaviors (p<0.01) and decrease mounting behaviors (p<0.05). No significant influence of ghrelin was found on average daily weight gain (ADG) and average daily feed intake (ADFI) in this experiment (p>0.05). In conclusion, exogenous ghrelin by the method above and at the dosage of $1{\mu}g/d$ pig could cause a variety of behavioral effects, but not improve performance of weanling piglets.