Agriculture Reference
In-Depth Information
2 Production Efficiency of Ruminants:
Feed, Nitrogen and Methane
J. Dijkstra, 1 * J. France, 2 J.L. Ellis, 1,2 A.B. Strathe, 3 E. Kebreab 4 and A. Bannink 5
1 Animal Nutrition Group, Wageningen University, Wageningen, The Netherlands;
2 Centre for Nutrition Modelling, Department of Animal and Poultry Science,
University of Guelph, Ontario, Canada; 3 Department of Basic Animal and Veterinary
Sciences, University of Copenhagen, Copenhagen, Denmark; 4 Department of
Animal Science, University of California, Davis, California, USA; 5 Wageningen UR
Livestock Research, Lelystad, The Netherlands
Introduction
of feed into milk or meat is associated with
various energy and nutrient losses, including
excretion of nitrogen (N) and phosphorus (P) in
faeces and urine, and emission of environmental
pollutants including the greenhouse gases
methane (CH 4 ), nitrous oxide (N 2 O) and carbon
dioxide (CO 2 ). Moreover, resources such as ara-
ble land, water, minerals and fuel are limited.
The livestock sector is by far the largest anthro-
pogenic user of land. Overgrazing and erosion
caused by livestock action is a major contributor
to land degradation. On the other hand, live-
stock production makes important contribu-
tions to agricultural economies throughout the
world. Livestock products provide a major share
of food for human consumption, and livestock
production is socially and politically significant,
contributing to livelihood and employment of
many people (Steinfeld et al ., 2006). Mearns
(2005) argues that livestock production can
play an instrumental role in supporting sus-
tainable rangeland management, preserving
wildlife and other forms of biodiversity, and
enhancing soil fertility and nutrient cycling. In
particular, since the area of grazing land is more
than double that of cropping land (FAO, 2011),
The world population is expected to grow from
6.9 billion in 2010 to 9.3 billion in 2050
(United Nations Population Division, 2010). Less
developed countries will experience the most
population growth, with only minor population
increases in developed countries. By 2050, this
expanded world population is expected to con-
sume two-thirds more animal protein than it does
today. Total consumption of meat is projected to
increase by 73% and that of dairy products by
58% (FAO, 2011). The prospects to increase sig-
nificantly the amount of arable agricultural land
are small, and food production must intensify to
ensure an abundant food supply.
Increased animal production has the
potential for added consequences (usually per-
ceived to be negative) for the environment,
unless steps are taken to ensure that the natural
resource base (land, vegetation, water, air and
biodiversity) can be sustained while still increas-
ing food production. Thus a major challenge is
not merely increasing productivity, but achiev-
ing this increased productivity without adverse
consequences (Godfray et al ., 2010). Conversion
 
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