The effect of grinding and pelleting on the nutritive value of poor quality roughages for sheep

Abstract

SUMMARYAnalysis of published data relating to the chemical composition of feeds – mostly roughages – before and after grinding and pelleting showed that ash and crude-protein content increased and crude fibre declined. On the assumption that the ash content was unaffected by grinding and pelleting, the crude-protein and crude-lipid content of the original material was shown to be unaffected by the process but the total carbohydrate was depressed. The loss of organic matter on pelleting was 9% and reasons are given for believing that this was due to partial pyrolysis of the carbohydrate.Calorimetric experiments with a poor quality sainfoin hay and a poor aftermath mixed hay showed that grinding and pelleting increased intake by over 80%, and also increased the metabolizability of the gross energy. The increases were from 37·4 to 40·7% for sainfoin and from 38·2 to 44·4% for the hay. The energy of the pellets was used more efficiently for maintenance in both instances, and with the hay, the efficiency of utilization of its metabolizable energy for production increased from 24·2 to 54·1%. With sainfoin no similar comparison was possible since the sheep given the chopped sainfoin could not achieve positive energy retention. The sainfoin pellets were used for production with an efficiency of 56%. Energy retention in sheep given as much sainfoin as they would consume without refusal increased from – 336 to + 3207 kj/d on pelleting the diet. With hay or hay pellets which were given ad libitumthe corresponding values were + 297 to + 4742 kj/d respectively.