High level cereal diets for the growing/finishing pig: III. A comparison with a control diet of diets containing high levels of maize, flaked maize, sorghum, wheat and barley

Abstract

SUMMARYIn a randomized block experiment, seventy-two Large White type weaner pigs (thirty-six hogs and thirty-six gilts) were individually and restrictedly fed to 200 lb live weight six diets (as wet mashes). Five of these diets contained high levels (85 % in the starter diets and 90 % in the finisher diets) of either maize, flaked maize, sorghum, wheat or barley. The sixth diet, which acted as the control diet for the experiment, was similar to the barley diet except that 25 % of weatings replaced a similar percentage of barley. A further three groups of six litter-mate hog pigs per group were used to measure the digestibility of these diets.For the starter diets the maize diet had the highest digestible energy content, for the finisher diets the highest values were for the wheat and sorghum diets which in turn were similar to each other. The digestible energy content of the flaked maize diet was higher than the contents of the barley and control diets but lower than the contents determined for the other three diets.Three of the pigs fed the sorghum diet developed leg weaknesses and this affected growth rate and food conversion efficiency. The symptoms suggested a pantothenic acid deficiency but the results of assays carried out on all the diets indicated that the condition was not necessarily due to a deficiency of this vitamin. Growth rates in the starter period (up to 115 lb) did not differ significantly between diets but food conversion for the maize and barley diets was significantly superior to that for the wheat and sorghum diets. In the finisher period growth rate and food conversion efficiency for the maize and wheat diets was significantly superior compared with that for the other four diets. Overall, from start to slaughter, the maize diet was significantly superior to the flaked maize, sorghum and control diets in both these parameters of performance. The energetic efficiencies of growth tended to be poorer for those diets with the better food conversion ratios, the best efficiency being for the control diet.Carcass length differences were not significant but backfat thickness and eye muscle area differences followed closely the pattern found for lean and fat content of the carcass. In this context the highest percentages of lean were found first in the control and, secondly, in the barley treatment carcasses. Some differences were found in the development of anatomical regions and tissues within these regions. In particular, and relative to the five other diets, there were in the control diet carcasses (1) higher percentages formed by the leg and shoulder and (2) a higher percentage of lean in the middle.