A modified form of the comparative slaughter technique has been used to measure the energy value of well preserved malt distiller's groins (MDG) nrixed with dried ground grass and the same grass made into pellets. The mixture contained equal quantities of digestible organic matter as MDG and dried grass, and the energy retention of lambs given eiiher this mixture or pelleted grass was measured for an increase of weight from 30 to 45 kg. Lambs receiving the mixttrre had a significantly greater ( P < 0.05) raie of growih than those Jeci on the grass pellets. On average, the latter animals needed about 25% more meiaholisable energy than those given MDG and dried grass to reach the same slaurhter weight. The mean daily intake of energy by the lambs receiving the mixture was 7% higher and their energy retention per unii of metabolisable energy intake was significantly greater ( P < 0.05) than that of the other animals. The incan effkiency of utilisation of metuholisable energy for fattening was 6 3 . 3 "/, for the mixed diet and 50.7% for the pelleted dried grass. The outstanding productive ability of the mixture was thought to be due to a synergistic eject between the two components and dependent upon the w$lpreserved nutritive value of the MDG used.
IntroductionTHE comparative slaughter technique is rarely used t o evaluate animal foods because it is expensive in terms of animals and time. However, the method was chosen for the measurement of the energy value of malt distiller's grain ( M D G ) since the alternative method of either direct or indirect calorimetry was not available. In previous work's2 the digestibility of M D G has been measured when fed alone or with a variety of other foods and supplements and the content of metabolisable energy has been calculated from these data. Such calculated contents may differ however from directly determined values through errors in predicting losses of energy in urine and as methane. Czerkawski et u I . ,~ for example, have shown that the presenceofunsaturatedfattyacids in the rumen may result in a decrease in energy lost as methane. In addition, a variety of factors affect the utilisation of dietary energy for lipogenesis which makes prediction of net energy from metabolisable energy subject to considerable error. To avoid such errors the net energy of MDG, when mixed with dried grass has been determined directly using a modification of the slaughter technique described by Thornson.*
Experimental
DesignA mixture containing approximately equal quantities of digestible organic matter as MDG and dried grass, and the same dried grass but in the pelleted form were evaluated using a group of 19 lambs. Five lambs chosen at random were slaughtered when they reached a body weight of 30 kg and body energy content was determined on each. The remaining lambs were divided at random into two equal groups and when their body weight reached 30 kg they were placed on one of the two dietary treatments. These lambs were slaughtered when their liveweight reached 45 kg and the content of the...
