Abstract:
EFFECT OF MATURITY OF PASTURE HAY ON ITS FEEDING VALUE FOR FATTENING STEERS A. H. BISHOP* and T. D. KENTISH* Summary Equal areas of grass-clover pasture were mown at three stages of maturity in the spring of three years, and the resulting hay was given to groups of steers in the following autumn as their sole feed. The steers ate similar amounts of early and mid-season hay each day but less of late hay or mouldy hay. The daily rate of gain in live weight of steers fed early hay was significantly greater in two out of three years than that of those fed either mid-season or late hay. Steers fed mid-season hay had higher rates of gain than those fed late hay. The total liveweight gain produced from the hay made on equal areas was greatest for steers fed mid-season hay. It is concluded that pasture hay mown between ear emergence and flowering of the perennial grass and cured without moulding, has a place as a fattening ration for cattle. I. INTRODUCTION Franklin (1956) found that beef cattle in southern Australia gained weight rapidly in the spring, but liveweight increase ceased in January and did not recommence until mid-winter or early spring. In Victoria, surplus pasture growth conserved in the spring as hay is often fed to sheep and cattle in the following autumn, later summer and winter. Provided such hay is of satisfactory feeding value, there appears to be no reason why it should not be used to fatten cattle. Kidwell, Bohman and Hunter (1954) working in the U.S.A., found that cattle fed on early-cut meadow hay fattened faster than those fed on late-cut hay, and Blaxter and Wilson (1963) showed that much more energy was available for production from hay, as the sole feed, made from young rather than mature grass. McLaughlin and Bishop (1968) showed that early-cut hay was superior to mid-season hay when fed as a supplement to weaner sheep. The present series of experiments compares the gain in weight of steers fed pasture hays conserved at three different stages of growth. In each experiment, the whole conserved product from equal areas of one pasture was fedf to the animals as the sole diet. II. EXPERIMENTAL The experiments were conducted at the Pastoral Research Station, Hamilton and continued for three years (1963-64 to 196566). The Station is on the basalt plains of western Victoria where the mean annual rainfall is 66 cm (26 in.). The areas conserved, mowing dates, type of pasture and weather conditions during conservation in each year are shown in Table 1 . `&Department of Agriculture, Pastoral Research Station, Hamilton, Victoria. tPresent address : 'Kedron', Kalangadoo, South Australia. 71 (a) Location and Period (b) Pastures and Area Conserved TABLE 1 Pastures and Conditions at Conservation The pasture was closed for hay making during September and in early November, 4 to 6 acres (1.6-2.4 ha) was mown in four strips, `each located centrally in a quarter of the area. Two weeks later, an equal area was mown by cutting additional swathes on each side of the four strips and after a further two weeks this process was repeated. The first cut was made when the heads of perennial ryegrass, Lolium perenne L., were emerging, the second was made when the ryegrass was in flower, and the third when seed was setting. (c) Conservation Methods The mown grass was raked into windrows and, when sufficiently dry, was baled with a pick-up baler. The baled hay was allowed to cure in the field for approximately one month and was then stacked in a shed for two months before use. (d) Sampling the Fodders In 1964-65 and 1965-66, the hays were sampled on eight occasions during the feeding period by cutting cores from all the bales being fed on one day. In 1963-64, one bale in ten had been sampled in like fashion as the hay was carted in for stacking. On each occasion these samples were combined and sub-sampled for the determination of moisture content and proximate constituents. (e) Cattle In February of each year, the conserved fodders were fed to groups of steers (Table 3) which were confined in yards and given no feed other than the hay. The steers were allocated to treatments at random within liveweight classes. The initial weights used in the experiment were taken after the animals had been removed from pasture and had been without water for 17 h. The final weights were taken after 17 h without food or water. Intermediate weighings were made at intervals of two weeks direct from the feedlot. The steers were fed to appetite daily in troughs. The amount of fodder given was weighed and the ration was adjusted when necessary, so that between 10% and 20% remained at the succeeding feeding. The animals were slaughtered as soon as practicable after the last of each hay had been given. The dressing percentage was calculated on a basis of the hot carcass weight and the final weight. III. RESULTS (a) Yield of Hay The yields of hay (Table 1) varied considerably according to the time of mowing in each year, but between years the variation was relatively small. In 1964, a year of low spring rainfall, the yield of late hay was less than that of mid-season hay, but in 1965 when a dry October was followed by ample rain in November, yield rose steeply with advancing maturity. (b) Analysis of Fodders In each year the crude protein content of the early hay (Table 2) was higher than that of the mid-season hay, and this in turn was higher than the late hay except in one instance. The decline in crude protein content was accompanied by 73 Chemical Composition of the Hays, Percent in Dry Matter t TABLE 2 an increase in nitrogen free extract in 1963-64, and by increases in crude fibre and nitrogen free extract in the remaining years. The total consumption of hay (Table 3) was the amount of hay made from the area mown. This amount, and the daily consumption of hay, determined the length of the feeding period which varied from 35 to 105 days. There was relatively little variation in the daily consumption of hay per head between years and treatments. However, the consumption of early hay in 1963-64, and of mid-season hay in 1964-65 were the lowest for these classes of hay and, in each case, the hay was noticeably mouldy at feeding. No other hay in any year was so noticeably mouldy, but some mould was present in other early and mid-season hays. The total gain (Table 3) of steers fed early hay was less than that of those fed mid-season hay in 1963-64 and 1965-66 (P<O.Ol) but was greater in 1964-65 (PCO.05). It was greater than that of those fed late hay in one year, less in one year, and was not different in one year. For steers fed mid-season hay, the total gain was greater than those fed late hay in one year (P<O.Ol) and not different in two years. The quantity of hay fed (dry basis) per unit of liveweight gain per steer (Table 3) varied widely between hays. The ranges of values for this ratio were 7 to 13, 10 to 20 and 16 to 22 for the early, mid-season and late hays respectively. In all years, this ratio increased with time of harvest except in the first year, when the early hay was mouldy. For the first two years, the mean daily rate of gain (Table 3) for the steers on each hay was calculated from the initial empty weight and the empty weights taken at the time the early hay group finished their hay. In 1965-66, the daily gain was calculated on initial and final weights in each case, but a check on intermediate full weights showed that the rates of gain were uniform. The daily rate of gain of steers fed early hay was significantly higher than that of those fed mid-season hay in two years (P<O.Ol) and was lower (P<O.Ol) 74 (c) Consumption of Hay (d) Total Liveweight Gain (e) Ratio of Hay fed to Liveweight Gain (f) Daily rate of Gain TABLE 3 in one year. It was superior to that of those fed late hay in two years (P<O.Ol) and not different in one. For steers fed mid-season hay, the daily rate of gain was higher than that of those fed late hay in two years (P<O.Ol) and was not different in one year. (g) Yield of Carcass Meat In two years there were no significant differences in the mean dressing percentage of the steers fed the different hays (Table 3), but in 1965-66 the steers fed early hay had a significantly lower dressing percentage than those fed mid-season hay and late hay (P<O.Ol and P<O.O5). IV. DISCUSSION As the time of mowing for hay making advanced through three stages of maturity of the pasture, the following effects were noted; the yield increased substantially in the first interval; the crude protein content. of the resulting hay declined; and, when given to steers, the daily consumption was lower with the late cut hay and with mouldy hay. The total liveweight gain produced from the whole conserved product of the equal areas was determined by the quantity and quality of each product. In two out of three comparisons, the steers fed mid-season hay produced a higher total liveweight gain than that of those fed early hay or late hay. However, as the pasture first mown was able to commence regrowth two weeks earlier than that used for the mid-season hay, other uses to which this aftermath could be put (McLaughlin and Bishop 1968) may compensate for some or all of the differences between these two hays. Thus early and mid-season hay are likely to be preferable to late hay in terms of total production. Whilst total liveweight gain is a satisfactory basis for assessing the effect of applying fodder conservation at different times to the same area of pasture, it does not enable the fattening quality of rations to be assessed or compared with those recorded by other workers. The daily rate of liveweight gain is a basis on which such comparisons can be made, provided that the dressing percentage and carcass characteristics do not differ materially, and that the ration is substantially above the maintenance level (Myer and Garrett 1967). The daily rate of gain of the steers declined with increasing maturity of the hay and was further reduced by the presence of noticeable amounts of mould. However, in no instance was early hay or mid-season hay, which was mouldy, inferior to late hay in respect of either total gain or gain per day. The order of difference between the daily rates of gain was large, the decline being approximately 20% for mid-season hay and 50% for late hay. A similar order of difference was recorded for the weight of hay fed per unit of liveweight gain, which was 10, 14, and 19 for early hay, mid-season hay and late hay respectively. Such orders of difference are not explained simply by differences in the content of nutrients and the daily intake of the hays, and it is apparent that the digestibility is also involved. The maturing of pastures is associated with a decline in digestibility (Homb 1953; Reid et al. 1959; Minson, Raymond and Harris 1960 a, 1960 b). Furthermore, the voluntary intake is in turn affected by digestibility (Murdoch 1967; Milford and Minson 1966). 76 The cattle fattening experiments discussed by Franklin (1956) comprised over 300 steers fed 22 different rations, including pasture hay, silage, lucerne hay, grains, cereal products and industrial by-products. The rates of gain recorded in this experiment on four out of six early and mid-season hays compare favourably with the best performances reported by Franklin (1956). The work of Blaxter and Wilson (1963) suggests that there may be scope for improving the economic production from hay by adding grain or other concentrate supplement. However, this study also indicates that if hay is fed with a concentrate, the optimum time for conservation will depend on the quantity of concentrate fed. It is concluded that hay made from pasture mown between ear emergence and flowering, when baled dry enough to prevent moulding, has a place as a fattening c ration for cattle in southern Australia. V. ACKNOWLEDGMENT The authors are indebted to Mr. R. Jardine for assistance with the statistical analysis, to Mr. W. I. Walbran for the analysis of the fodders, and to Dr. R. H. Watson and colleagues at the Pastoral Research Station for assistance and suggestions in preparing this report. VI. REFERENCES BLAXTER, K. L., and W ILSON, R. S. ( 1963). Anim. Prod. 5: 27. F RANKLIN, M. C. ( 1956). Bull. Anim. Prod. Comm. Aust. H OMB, T. ( 1953). Acta Agric. stand. 3: 1. KIDWELL, J. F., BOHMAN , V. R., and H UNTER , J. %E. (1954). J. Anim. Sci. 13: 543. M CL AUGHLIN, J. M., and B ISHOP, A. H. (1968). Aust. J. expt. Agric. Anim. Hub. (in press). 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