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This article in JAS

  1. Vol. 94 No. 5, p. 2047-2058
     
    Received: Jan 08, 2016
    Accepted: Mar 08, 2016
    Published: April 22, 2016


    2 Corresponding author(s): d.poppi@uq.edu.au
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doi:10.2527/jas.2016-0292

Supplementation of cattle fed tropical grasses with microalgae increases microbial protein production and average daily gain1

  1. D. F. A. Costa*†,
  2. S. P. Quigley,
  3. P. Isherwood,
  4. S. R. McLennan and
  5. D. P. Poppi 2
  1. * Octavio Bastos University Center, Av Dr Octavio Bastos, Sao Joao da Boa Vista, SP, Brazil 13874149
     School of Agriculture and Food Sciences, The University of Queensland, Warrego Highway, Gatton, QLD, Australia 4343
     Centre for Animal Science, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Dutton Park, QLD, Australia 4102

Abstract

A series of 3 experiments were conducted to evaluate the use of microalgae as supplements for ruminants consuming low-CP tropical grasses. In Exp. 1, the chemical composition and in vitro protein degradability of 9 algae species and 4 protein supplements were determined. In Exp. 2, rumen function and microbial protein (MCP) production were determined in Bos indicus steers fed speargrass hay alone or supplemented with Spirulina platensis, Chlorella pyrenoidosa, Dunaliella salina, or cottonseed meal (CSM). In Exp. 3, DMI and ADG were determined in B. indicus steers fed speargrass hay alone or supplemented with increasing amounts of NPN (urea combined with ammonia sulfate), CSM, or S. platensis. In Exp. 1, the CP content of S. platensis and C. pyrenoidosa (675 and 580 g/kg DM) was highest among the algae species and higher than the other protein supplements evaluated, and Schizochytrium sp. had the highest crude lipid (CL) content (198 g/kg DM). In Exp. 2, S. platensis supplementation increased speargrass hay intake, the efficiency of MCP production, the fractional outflow rate of digesta from the rumen, the concentration of NH3N, and the molar proportion of branched-chain fatty acids in the rumen fluid of steers above all other treatments. Dunaliella salina acceptance by steers was low and this resulted in no significant difference to unsupplemented steers for all parameters measured for this algae supplement. In Exp. 3, ADG linearly increased with increasing supplementary N intake from both S. platensis and NPN, with no difference between the 2 supplements. In contrast, ADG quadratically increased with increasing supplementary N intake from CSM. It was concluded that S. platensis and C. pyrenoidosa may potentially be used as protein sources for cattle grazing low-CP pastures.

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