Maintenance rations for Merino sheep. 1. A comparative study of daily and weekly feeding on rations containing high proportions of wheat and several proportions of roughage to concentrate

Abstract

Groups of full-mouthed Merino wethers were given 4.25 lb. starch equivalent (4,550 calories of net energy) per sheep per week, to maintain a low to moderate store condition of 75 lb. body weight, on each of four rations, namely 50:50, 30:60, 20:80, and 10:90 mixtures of wheaten chaff and wheat. Finely-ground limestone was added to these rations to correct calcium phosphorus imbalance. The groups were paired, one of each pair being given the food once a week and the other being given it in daily portions. The weekly-fed groups were brought on to this regime during a preparatory period of 77 days during which they were fed at intervals which were gradually increased from 3 to 7 days. The surviving sheep in the daily-fed groups maintained their mean body weight and general condition as well as did those in the weekly-fed groups but at the end of the experiment the range in body weight in the daily-fed groups was greater: 41.9 per cent. of the daily-fed animals gained in weight during the period of 344 days, whereas only 14.2 per cent. of the weekly-fed animals did so. This difference was due largely to differences in rate of food consumption. The rate of consumption of the food by the daily-fed groups increased during the progress of the experiment. The sheep receiving the larger amounts of roughage took longer to consume the daily ration. The sheep in the weekly-fed groups ate the week's ration in 4 – 4½ days and occasionally took half a day longer. The death rate in the daily-fed groups was 30.2 per cent, compared with 11.8 per cent. in the meekly-fed group. The deaths occurred mainly (72 per cent.) in the sheep which had lost 40 per cent. or more of their initial body weight. Mean wool production from the daily-fed sheep ranged from 6.73 lb. to 6.94 lb. per sheep, and from the weekly-fed groups from 7.19 lb. to 7.57 lb. Regain of body weight after the termination of the experiment on the low diet was studied. Groups which were retained in pens and fed ad lib. gained steadily in weight and maintained a considerable lead over those which had been turned out to graze. In a group of sheep at pasture there was a close positive correlation between the loss suffered in body weight on the experimental low diet and the subsequent improvement at pasture. The rate and magnitude of subsequent regain of weight were not influenced by the proportion of roughage in the experimental diet or by the origin of the sheep from the daily-fed and weekly-fed groups. An inverse relationship between atmospheric temperatures and body-weight changes was observed. The experiments showed that daily feeding of the sheep at levels sufficient for survival was less satisfactory than weekly feeding at the same level. The practical importance of the results is discussed briefly.