Concentrate plus ground barley straw pellets can replace conventional feeding systems for light fattening lambs

Forty male Merino lambs (6–8 weeks old and 14.1 ± 0.20 kg body weight, BW) were used to compare the traditional feeding system for this animal, based on concentrate and long form barley supplied separately, with total mixed ration (TMR) pellets including different proportions of ground barley straw, for their effects on feed intake, animal performance and carcass and meat characteristics. Lambs were divided into four experimental groups (n = 10), each randomly assigned to one dietary treatment: Control (conventional system: long form barley straw and concentrate feed in separated feeding troughs), F05 (TMR pellet including 50 g barley straw/kg), F15 (TMR pellet including 150 g barley straw/kg) and F25 (TMR pellet including 250 g barley straw/kg). Lambs were fed the corresponding diet ad libitum. On days 22–26, feces and urine were collected from four animals per group. When animals reached 27 kg BW, they were slaughtered. Barley straw, total dry matter (DM), crude protein (CP), neutral detergent (NDF) and acid detergent (ADF) fiber and metabolizable energy intake linearly increased (P < 0.001) with the level of barley straw in the TMR. Dry matter digestibility decreased as barley straw in the diet increased, but NDF and ADF digestibility and N-balance were not affected (P > 0.10). F25 lambs had the greatest and F05 the smallest (P = 0.002) values of average daily gain, but the feed to gain ratio was not significantly affected by the dietary treatments (P = 0.172). Abomasum-intestine content weight linearly increased with barley straw in the TMR (P = 0.041). Neither carcass (carcass weight, chilling losses, dressing percentage, conformation, measurements, fat thickness or jointing into commercial cuts) nor meat characteristics (pH, fat and meat color, cooking losses and texture) were affected by the level of barley straw in the TMR (P > 0.10). Therefore, it is possible to fatten light lambs on a TMR pellet including ground barley straw by increasing average daily gain and reducing the fattening period, without any negative impact on carcass and meat characteristics.