Abstract:
A COMPARISON OF PASTURE CONSERVED AS HAY OR AS SILAGE FOR FATTENING BEEF CATTLE A. H. BISHOP* and T. D. KENTISH Summary Hay and silage were made by mowing at the same time (at ear emergence of perennial rye grass) equal areas of the same clover grass pasture. The whole of each fodder was later fed, as the sole ration, to groups year-old steers which were then slaughtered. Over four years, the two fodders yielded equal quantities of dry matter and produced similar total liveweight gain and carcass weight. Highest rates of gain recorded were from hay. The quality and total recovery of edible fodder was consistent between years for the silage, but was variable for the hay as a result of weather effects during field curing. I. INTRODUCTION Hay and silage are alternate forms in which pasture can be conserved in the spring. Bishop and Kentish (1970) compared these two products by feeding them as a sole ration to sheep, and found that hay provided more fodder and that the liveweight performance of the sheep was better on hay than on silage. Franklin (1956) suggested silage as a ration which might be used for fattening cattle during the summer period when cattle on dry pastures in southern Australia normally cease gaining weight. The present series of experiments was conducted to compare hay and silage mown at the same time as rations for fattening two year-old beef cattle. II. MATERIALS AND METHODS (a) Location The investigation was carried out at the Pastoral Research Station, Hamilton, for four years 1963 to 1966. The environment was described by Bishop and Kentish (1968). (b) Pastures and Areu Conserved An area of pasture was closed for conservation in September of each year. The pastures used from 1963 to 1965 were described by Bishop and Kentish * Department of Agriculture, Pastoral Research Station, Hamilton, Victoria. t 'Kedron', Kalangadoo, South Australia. (1968) (Table l), and the hay was the early mown hay in Table 1. In 1966, the pasture used was similar to those used in 1963 and 1964, and 2.2 ha was mown for each treatment on November 14, 1966. The weather was overcast and light rain fell during the mowing and ensiling; but only 5 mm was recorded between mowing and baling. . Silage was made from four strips of the same pasture, adjacent to those used for hay, and mown on the same-date in each year. The areas used for hay and silage were equal and were allotted at random to the treatments. Silage was made by picking up the mown swathes with a forage harvester after wilting for 1 to 4 h during the day, or overnight after a late afternoon mowing. The material was stacked in a clamp supported by steel sidewalls and roled with a tractor continually during stacking. On completion, the whole stack was rolled for 10 to 25 h, and covered with polythene sheeting held down with 7 cm of earth. The method of making hay was described by Bishop and Kentish (1968). (d) Experimental Animals (c) Conservation Methods In February of each year, the conserved fodders were fed, as a sole diet, to groups of nine or ten steers in feedlots. The animals were Aberdeen Angus or Herefords, about two years old (Table 3). (e) Experimental The steers were allocated to treatments at random within liveweight classes. Initial and final liveweights were taken after fasting for 17-21 h. Intermediate weighings at intervals of two weeks were direct from the feedlot. The steers were fed in troughs to appetite daily. The ration was adjusted when necesary so that 10 to 20 per cent remained at the next feeding. Once each week for hay and twice each week for silage, residues were collected, weighed and dry matter percentage determined. The animals were slaughtered as soon as the last of each fodder had been fed. The dressing percentage was calculated from the hot carcass weight and final liveweigh t. III. RESULTS (a) Yield and Chemical Composition of the Fodders In two years 1964/65 and 1965/66, the yield of silage exceeded that of the hay and, in the other two years, the yield of hay exceeded that of the silage (Table 1). The relative recovery of edible fodder varied widely between years (Table 1) . In the different years, between 13 per cent and 26 per cent of silage D.M. was wasted, mainly decomposed material removed at the stack. Very little hay was wasted. In 1965/66, the recovery of hay was much lower than that of silage because high winds during field curing broke up the windrows. The crude protein of the hay was higher than that of the silage in two of the four years (Table 2). In each year, the nitrogen-free extract of the hay was higher than that of the silage and the ether extract was lower. The difference between the moisture content of the silage determined by oven-drying at lOO'C, and by the method of Dean and Stark, is evidence of loss of volatiles during drying. Differences varying from 1.3 to 2.2 per cent in different TABLE I TABLE 2 495 years suggest 10 per cent by The low that the silage that the dry mater yield could be underestimated by as much as oven-drying at 65 'C. pH, high lactic acid content and low content of volatiles indicate was of high quality in each year. (b) Consumption of the Fodders Except in the first year when the consumption of both fodders was low, there was relatively little variation in the consump;ion of th.e fodders between years (Table 3). Steers fed silage consumed daily between 6.7 and 9.3 kg of D.M., and those fed hay between 8.0 and 9.3 kg D.M. (c) Liveweight Gain, Carcass Yield and Dressing Percentage There was little difference in total liveweight gains between steers receiving the two fodders (Table 3). The daily rate of gain of steers fed hay was significantly better than that of steers fed silage only in 1965/66 (P<O.Ol ). The mean carcass weights of groups of steers were not significantly different in any year. In two years, the dressing percentage of the steers fed silage was significantly higher (P<O.Ol ) than of those fed hay. In the other two years, the dressing percentage of the silage groups was lower (P<O.Ol and P<O.O5 respectively) than of those fed hay. The mean intake of fodder per unit of Iiveweight gain (Table 3) was variable for the hays but consistent for the silages. In two years, the ratio for hay was lower and in two years it was higher than any of the ratios for silage. IV. DISCUSSION The conservation of equal areas of pasture, at the same time, as hay or as silage resulted in no difference in the mean yield of dry matter as measured at feeding. The crude protein content of the hay was usually higher and the ether extract lower than in the silage. The daily consumption of dry matter by the animals fed silage was consistently lower than by those fed hay. The total liveweight gain of the steers was similar for hay and silage in all years, but hay produced significantly faster rates of gain than did silage in one year (P<O.O5): Hay showed a higher potential for daily rate of gain, the two best performances being 0.9 and 1.25 kg per day compared with 0.77 kg for silage. McCarrick (1966) compared hay and silage and found that consistent differences in dressing percentage gave silage-fed steers an advantage in carcass weight over hay-fed steers. He concluded that liveweight data were of little value in such comparisons. Such a difference in dressing percentage was obtained in only two out of four years in this experiment. In the other two years the silage-fed steers had the higher dressing percentage and, in these years, hay was inferior to, or no better than, silage in rate and efficiency of liveweight gain. In discussing the time to mow hay for maximum animal production, Blaxter and Wilson (1963) showed that the optimum may depend on which form of production is studied and whether a fodder is to be fed alone or with a concentrate. In this experiment, the form of production studied was one for which silage TABLE 3 is commonly used, but the results could be different if the products were fed with a concentrate. Harris, Raymond and Wilson (1966) studied the wilting time used in silagemaking. They concluded that silage intake was limited by factors to which young sheep were more sensitive than older sheep - an effect which could be cumulative - and they suggested that this could be due to organic acids, particularly lactic acid, in silage. The similarity in the overall result conceals the important difference that silage was the more consistent between years in yield of edible products and in feeding value, as indicated by the daily gain of steers. The analyses of the silage suggest that the quality was good ,throughout the experiment and the recovery of edible nutrients compared very favourably with that of hay. By contrast, Bishop and Kentish (1970) found nutrient recovery was very much lower with silage made in vacuum stacks. In the present study, the stack was adequately rolled and then covered with nolythene sheeting and 5 to 7 cm of soil (Minson and Lancaster 1965). Daily gain of animals fed hay was variable and was seriously depressed in two years; in 1963/64, when there was an excessive amount of mould in the hay and, in 1966/67, when only a small amount of mould was noted but much dust was present, possibly a consequence of heavy infestation by red-legged earth mite (Halotydeus destructor). In 1965/66, when the rate of daily gain of steers fed hay was high, the total recovery of fodder was seriously depressed by the effects of a high wind during curing. Thus in three out of four years, the results of feeding the hay were affected `by factors which do not normallv apply to early mown hay. A comparison of the results of other experiments at the same location, in which six early hays were fed to weaner sheep, suggests that the above frequency was abnormally high (McLaughlin and Bishon 1969 and unpublished data). It is the practice in the industry to make hay over an extended period in November and December, whereas silage is made only in the early part of the season, often with the aim of making high quality fodder, when the risk of weather damage to hay is high. The results confirm the effect of weather on early made hay as found by Bishop and Kentish ( 1968). This has not resulted in an overall advantage in terms of the carcass weight of the steers fed silage made at the same time, but suggests that mid-season hay would often be better than early hay in this environment. It is concluded that when equipment for both practices is available, personal preference, operating costs, rate of harvesting and rate of fattening will determine how much of each product is made. The investment in additional equipment to harvest early fodder-as silage is not justified in the environment studied. V. ACKNOWLEDGMENT The authors are indebted to Mr. R. Jardine for assistance with the statistical analysis, to Mr. W. J. Walbran for the analysis of the fodders, and to Mr. R. Widmer for his assistance in caring for the experimental animals. VI. REFERENCES B ISHOP , A. H., and K ENTISH , T. D. (1968). Proc. Aust. Soc. Anim. Prod. 7: 71. B ISHOP , A. H., and K ENTISH , T. D. (1970). Aust. J. exp. Agric. Anim. Hub. 10: 13. B LAXTER , K. L., and W ILSON, R. S. ( 1963). Anim. Prod. 5: 27. F RANKLIN, M. C. (1956). Beef Cattle Investigations in the Southern States of Australia. H ARRIS, Rep. Anim. Prod. Comm. Aust. (C.S.I.R.O. Melbourne). C. E., R AYMOND , W. F., and W ILSON R. F. ( 1966). Proc. ht. Grassland Congr. MCCARIUCK, R. B. (1966). Proc. ht. Grassland Congr. 10: 575. M CL AUGHLIN , J. W., and B ISHOP A. H. (1969). Aust. J. exp. Agric. anim. Hub. 9: 272. MINION, D. J., and L ANCASTER , R. J. ( 1965). N.Z. J. Agric. Sci. 8: 542. 10: 565. 499