Phosphorus supplementation of beef cattle in the Victorian mallee.

Abstract

Animal Production in Australia PHOSPHORUS SUPPLEMENTATION OF BEEF CATTLE IN THE VICTORIAN MALLEE G.H. SMITH*, G.H. CASTLEMAN** SUMMARY Two experiments investigated the effects of phosphorus supplements on beef cattle production in the Victorian Mallee. In the first experiment, a daily supplement of Boneflour (13% phosphorus) produced a small, but significant response in the growth of steers grazing good spring feed. The second experiment, conducted over three years groups of autumn- calving Hereford cows. Management of was identical, except that one group was provided with supplement of about l0g of phosphorus per cow per day. supplementation had no significant effect on growth of cows or calves, nor on fertility of the cows. INTRODUCTION The Mallee is production being of extends from May to confirmed reports of (Dodson, 1972; Reed, a major cereal-growing area with sheep and beef less importance. On average, the growing season October. Over the years there have been many cattle suffering from phosphorus deficiency 1973). involved two the two groups a continuous Phosphorus either the and J.K.D. PARKER** It is known that poor phosphorus nutrition of beef cattle can restrict growth but there is no conclusive evidence that it has any special function in reproduction or lactation (Cohen, 1975). Both experiments reported here aimed to establish whether phosphorus supplementation alone might boost the production of beef cattle grazing under typical Mallee conditions. The work was conducted at the Mallee Research Station at Walpeup. MATERIALS AND METHODS 1 Experiment Forty-four yearling steers of various British breeds and their crosses were weighed after a 24 hour fast from feed and water and then allotted to two groups at random. The two groups were grazed The predominant on very similar adjacent plots, each of 15ha. fora'ge species were Jemalong Barrel Medic (Medicago truncuZata) and wheat regrowth with various volunteer species such as Barley Grass (Hordeurn ZeporinumL The experiment was conducted in the spring of 1973 and at no time did feed become limiting. One group of phosphorus as per head per day of the wheat and The supplements November. * of steers was fed an average daily supplement of 14g sterilized boneflour. It was fed mixed with a 2OOg The same amount of whole wheat grain and molasses. molasses was fed to the control group of steers. were fed daily for 100 days from mid August to late Department of Agriculture, Rutherglen Research Institute, Rutherglen, Vic. 3685 **Department of Agriculture, Mallee Research Station, Walpeup, 365 3507 Animal Production in Australia The two groups of steers were rotated after 50 days in an Afl steers were weighed attempt to reduce any plot differences. after a 24 hour fast from feed and water at the end of the 100 day experimental period. Experiment 2 young and mated weaned two and For the years 1975, 1976 and 1977, two groups each of 25 Hereford cows were grazed in adjacent paddocks of similar size Each year the cows calved in autumn, were feed availability. to Hereford bulls in winter (for 8 weeks) and the calves were The initial allocation was such that the and sold in summer. groups were as similar as possible with respect to age, weight calving-time of the COWS. For the duration of the experiment, one group of cattle received a continuous phosphorus supplement, and the other group The phosphorus supplement (monosodium phosphate) was the control. was dissolved in water to form a concentrated solution which was The dispenser then automatically dispensed into the water trough. was set to maintain a concentration of 263 ppm of phosphorus in the trough, which assuming a daily water consumption of 38 1 per cow would provide a log daily supplement of phosphorus for each cow. The ,forage grazed by the cattle was typical. of that on Mallee Pasture comprised Barley Grass (Hordeum hporinum), Bromus farms. SPP; numerous species of weeds and certain amounts of Lucerne (Medicago sativa) and other medics (Medicago minima, Medicago When forage was limited, the truncuZata and Medicago ZittoraZis). The cattle grazed cattle were supplemented.with hay and/or grain. cereal stubble during the summer/autumn period each year. All cows and calves were weighed monthly and birth dates and All feeds were analysed for birth weights of calves were recorded. calcium and phosphorus. RESULTS Experiment 1 Both groups of steers had an average fasted weight of 332 kg at The liveweight gains for the two groups the start of the experiment. Liveweight gains for the phosphorus supplemenare shown in Table 1. ted group were significantly greater than for the control group. TABLE 1 Liveweight gains for yearling steers grazed on spring forage for 100 days At the end of the 100 day experimental period all cattle were in prime condition and were sold for slaughter. 366 Animal Production in Australia Experiment 2 The rainfall in two of the three years of this experiment was long-term average below average (1975-375mm; 1976-271mm; 1977-202mm; 340mm). Consequently, the cattle only grazed green feed for brief periods each year and some hand feeding with hay and wheat was necessary in the winter/spring for 3 months in 1975, 5 months in 1976 and 4 months in 1977. There were no significant differences between the phosphorussupplemented and the control cattle in calf birth weights, calf weaning weights, calving percentage or calving interval (Table 2), nor in the monthly weights of the cows and calves at any stage over the 3 years. TABLE 2 Calf birth weights, weaning weights, calving intervals for 1975-1977 calving percentage and Analyses of various feeds available during the experiment are presented in Table 3. TABLE 3 Calcium, phosphorus and calcium:phosphorus consumed in Experiment 2 ratios of feeds 367 Animal Production in Australia DISCUSSION The significant response to phosphorus in the growth of steers in Experiment 1 is consistent with findings of Bisschop (1964) and Van Schalkwyk and Lombard (1969). Bischopp (1964) reported that supplementing with phosphorus all year was no more effective than supplementing only during the period of active, pasture growth. For the three years of Experiment 2, at no stage was there any response in growth or fertility to phosphorus-supplementation in the breeding herd. In a review, Cohen (1975) concluded that there was no firm evidence that phosphorus alone plays any special role in reproduction or milk production in the beef cow. In Experiment 2, over the dry, summer/autumn periods when the cattle grazed cereal stubbles (0.07% phosphorus) with no hand-feeding, there was never any indication of a liveweight response to phosphorus. This occurred despite the claim of phosphorus deficiency being a problem in Mallee cattle under dry or drought conditions (Reed, 1973). The liveweight response to phosphorus in cattle grazing green feed demonstrated in Experiment 1, was not evident in Experiment 2. Below average rainfall during Experiment 2 limited the availability of green feed and also supplementation with wheat grain during the winter/spring periods increased the phosphorus available to all cattle, thus reducing the likelihood of a response to phosphorus. The general conclusion of Experiment 2 Cohen (1972), that continuous supplementation not improve the performance of beef cattle in phosphorus deficiency had been reported as a REFERENCES 'Feeding phosphates to cattle'. south BISSCHOP, J.H.R. (1964) African Department of Agriculture Technical Services Science Bulletin 365. Aust. J. Exp. Agric. and Anim. Husb. 12:455 COHEN, R.D.H. (1972) Aust. Meat Res. Corn. Rev. 23~1 COHEN, R.D.H. (1975) 5~72 Dept. of Agric. S.A. ExtensEn Bulletin DODSON, M.E. (1972) 'The nutrient requirements of NATIONAL RESEARCH COUNCIL (1970) beef cattle' (National Academy of Sciences, Washington, D.C.) Vic. J. of Agric. 7&:20 REED, G.A. (1973) Agroanimalia 1:45 VAN SCHALKWYK, A. and LOMBARD, P.E. (1969) agrees with that of with phosphorus did an area where problem. 368