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Controlling voluntary intake of molasses-based supplements in grazing cattle

Dixon, R. M. (2013) Controlling voluntary intake of molasses-based supplements in grazing cattle. Animal Production Science, 53 (3). pp. 217-225. ISSN 1836-0939

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Article Link(s): http://dx.doi.org/10.1071/an12130


Molasses-based liquid supplements fed ad libitum are widely used to provide additional metabolisable energy, non-protein N (NPN) and other nutrients to grazing cattle, but it is often difficult to achieve target intakes of supplementary nutrients. Experiments examined the effects of increasing concentrations of phosphoric acid, urea and ammonium sulfate on the voluntary intake (VI) of molasses-based supplements offered ad libitum to heifers grazing tropical pastures. In Experiment 1, the VI of a supplement containing 78 g urea/kg and 26 g phosphoric acid/kg as-fed (M80U+PA) was 3.61 g DM/kg liveweight (LW) per day, and provided 181 mg NPN and 32.4 mg phosphorus (P)/kg LW per day. Increasing the urea content of the supplement to 137 g/kg (M140U+PA) or 195 g/kg (M200U+PA) reduced VI of supplement DM, NPN and P by up to 76%, 44% and 80%, respectively. VI of supplement containing ammonium sulfate (M140+AS+PA) was lower (P < 0.05) than that of M140U+PA supplement, and tended (P > 0.05) to be lower than that of M200U+PA supplement. In experiment 2, the VI by heifers of a supplement containing 200 g urea/kg (M200U) was 1.53 g supplement DM/kg LW per day, which provided 186 mg NPN/kg LW per day. Inclusion of 49 g phosphoric acid/kg as-fed in this supplement (M190U+50PA) reduced (P < 0.05) VI of supplement DM and NPN by 33% and 36%, respectively, while inclusion of 97 g phosphoric acid/kg (M180U+100PA) reduced (P < 0.05) VI of supplement DM and NPN by 43% and 48%, respectively. The M190U+50PA and M180U+100PA supplements provided 16 and 26 mg P/kg LW per day, respectively. Heifers not fed supplements gained 0.07 kg/day, and the M200U supplement increased (P < 0.05) LW gain to 0.18 kg/day. LW gain was further increased (P < 0.05) by the M190U+50PA to 0.28 kg/day, indicating a growth response to supplementary P. No adverse effects of the supplements on animal health were observed in any of the experiments. In conclusion, addition of urea and/or phosphoric acid to molasses supplements effectively reduced VI of supplementary DM, NPN and P, and in the circumstances of Experiment 2, both molasses-urea and P supplements increased heifer LW.

Item Type:Article
Business groups:Animal Science
Additional Information:Dixon, R. M. Department of Agriculture, Fisheries and Forestry Queensland The research was conducted with the facilities, staff and support of the Department of Agriculture, Fisheries and Forestry Queensland. The assistance of Mr D. Hirst for field experimentation, and Mr B. Burren, Mr P. Martin and Mr I. Brock for laboratory analysis is gratefully acknowledged. Also, I thank Mr K. McGuigan for advice on chemistry, Ms C. Playford for advice on biometry, and Mr D. B. Coates for the near-infrared spectroscopy analysis and valuable comments on the manuscript. The research was approved by the (then) DPI&F Animal Ethics Committee (reference numbers TSV/11/00 and TSV/43/01). Csiro publishing Collingwood
Keywords:animal growth phosphoric acid supplement acidity supplement intake urea near-infrared spectroscopy beef breeder cows northern australia purine derivatives diet selection urea-phosphate crude protein mineral acids food-intake feed-intake
Subjects:Animal culture > Feeds and feeding. Animal nutrition
Deposited On:28 Nov 2013 01:22
Last Modified:28 Nov 2013 01:22

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