Effects of two levels of dietary energy supplementation and rearing systems on growth and carcass characteristics of grower pigs

Abstract

The eight-week study was conducted to evaluate the effects of rearing system (indoor vs. outdoor) and energy level on digestibility, growth performance and on the carcass characteristics and visceral organs of pigs. A total of 48 Large Whites (LW) X Landrace (LR) male grower pigs were randomly selected at average weights of 27 ± 4.6.kg and divided into two equal groups that were either raised indoors or outdoors. Within each rearing system, half the pigs were fed on a diet formulated to contain either a normal energy level (14 MJ DE/kg) or high energy level (16.1 MJ DE/kg) resulting in a 2 X 2 factorial design. The pigs were fed ad libitum and water was freely available. Pigs were housed in pairs and each indoor and outdoor pig was offered a space allowance of 0.51 and 13.5 m2 respectively. Indoor pigs were raised in a temperature controlled house consisting of a concrete floor pen while outdoor pigs were on a pasture that predominantly consisted of Kikuyu. Movable gates were used to construct outdoor camps and empty feed bags were used to construct a shade for use as shelter. Faecal collection for digestibility determination took place during week 7 while the growth performance trial was still in progress. Chromium oxide was used to evaluate digestibility and faeces were grabbed before they fell to the ground and sampled. With the exception of ether extracts (EE), the digestibilities of crude protein (CP), digestible energy (DE), crude fibre (CF), neutral detergent fibre (NDF), acid detergent fibre (ADF) and organic matter (OM) were reduced (P <0.05) by rearing pigs outdoors. EE followed the same trend. Feeding the high energy (HE) diet significantly (P >0.05) improved the digestibilities of all the nutrients except for CP. There were no significant interactions (P>0.05) between rearing system and diet for the digestibility of nutrients. Daily gains were similar (P >0.05) between indoor and outdoor pigs. Daily feed intakes and conversions were significantly (P <0.05) lower in indoor pigs. There were no significant (P >0.05) differences between the daily gains and feed conversions of pigs fed either the normal energy (NE) or the HE diet. Indoor pigs fed the HE diet had lower (P < 0.05) feed intakes compared to pigs on the other treatments. In general, average daily feed intakes (ADFI) of the HE fed pigs were significantly (P <0.05) lower than those of the NE fed pigs. The carcass measurements of the indoor and outdoor pigs were similar. The gastro-intestinal tract (GIT) and the liver weights of the outdoor reared pigs were significantly (P <0.05) heavier than those of the indoor reared pigs. Feeding the HE diet led to significantly (P <0.05) higher carcass weights and dressing percentages. Interactive effects (P <0.05) of diet and rearing system were found for lean meat percentage (Lean P) and eye muscle area (EMA). Indoor pigs fed on the NE diet had higher Lean P and EMA while an opposite effect was obtained in the outdoor system. The liver of the NE diet fed pigs was significantly (P < 0.05) heavier than that of the pigs fed the HE diet. It can be concluded that with regard to growth performance and carcass characteristics, the NE and HE diets are respectively best suited for the indoor and outdoor rearing of pigs.