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19 Acetogenesis as an Alternative to Methanogenesis in the Rumen

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19

Acetogenesis as an Alternative to Methanogenesis in the Rumen

Emma J. Gagen, Stuart E. Denman and

Christopher S. McSweeney*

CSIRO Agriculture, St Lucia, Queensland, Australia

Abstract

Bacteria capable of producing acetate from

H2 and CO2 using the acetyl-CoA pathway

(4H2 + 2CO2 Æ CH3COOH + 2H2O) are known as acetogens. They have been found in a variety of anaerobic ecosystems, including sediments, wastewater treatment systems, soils and animal gut systems. In recent years, acetogens have received attention as a hydrogenotrophic population that may play a role in reducing methane

(CH4) emissions from ruminant animals.

During ruminal fermentation, methanogenic archaea reduce CO2 (4H2 + CO2 Æ CH4 +

2H2O) or methylated compounds to CH4.

Ruminal methanogenesis represents a loss of 2–12% of gross energy of ingested feed and contributes significantly to global greenhouse gas emissions. If methanogenesis could be suppressed in the rumen, acetogenesis may serve as an effective alternative hydrogen sink, resulting in an energy gain for the ruminant through the production of acetate. Acetogenesis is the dominating hydrogenotrophic pathway in other gut systems such as those of humans, pigs, termites and potentially some native Australian marsupials. The latter are of particular interest as they exhibit foregut fermentation analogous to that of ruminants, though resulting in significantly less CH4 production, suggesting the

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11 Climate Change: Impacts on Livestock Diversity in Tropical Countries

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11

Climate Change: Impacts on

Livestock Diversity in Tropical

Countries

S. Banik,1* P.K. Pankaj2 and S. Naskar1

1National

Research Centre on Pig, Guwahati, India; 2Central

Research Institute for Dryland Agriculture, Hyderabad, India

Abstract

The effect of changing climate will not only be confined to limited production, and the productivity of agricultural commodities, but will also have far-reaching consequences on dairy, meat, wool and other animal products.

The impact of climate change on the livestock sector as a whole will be felt more in tropical countries compared to temperate countries, largely because of the structure of production system and economics. The resultant pressure, both direct and indirect, is likely to result in further dilution of livestock diversity, which would specially affect the nutritional security and livelihood of small and marginal farmers. The challenge is to sustain genetic diversity and productivity by different adaptation strategies like production adjustment, breeding strategies, alteration of management systems, developing appropriate policies, scientific intervention and capacity building of livestock owners. In light of concerns over the impacts of climate change and climate variability, this chapter provides an overview of the opportunities for adaptation and mitigation strategies in tropical climatic conditions.

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5 Nutritional Strategies for Minimizing Phosphorus Pollution from the Livestock Industry

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5

Nutritional Strategies for

Minimizing Phosphorus Pollution from the Livestock Industry

P.P. Ray* and K.F. Knowlton

Virginia Tech, Blacksburg, USA

Abstract

5.1 Introduction

Livestock manure traditionally has been considered and used as a valuable resource by farmers to improve crop production.

Livestock manure is rich in nutrients

(nitrogen (N) and phosphorus (P)) and thus has been land applied to enrich soils. But land application of manure nutrients in excess of crop requirements can lead to saturated soil and loss of nutrients to surface water via runoff. Environmental concerns with P from animal agriculture are significant because livestock manure has always been land applied to meet crops’ N requirement, resulting in P application in excess of crops’

P requirement. The problem is aggravated with the intensification of livestock production, and now animal agriculture has been identified as a primary source of water quality impairment in many regions. But intensification and continuous advancement of livestock production is required to meet the increasing demand of food supply to feed a growing global population. Therefore, management strategies are needed that will improve livestock production while supporting the environmental and social pillars of sustainability. Nutritional strategies are economically and environmentally efficient tools to reduce P excretion by livestock. This chapter discusses nutritional strategies including precision feeding, phase feeding and approaches to improve feed P availability.

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4 Nitrogen Emissions from Animal Agricultural Systems and Strategies to Protect the Environment

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4

Nitrogen Emissions from Animal

Agricultural Systems and

Strategies to Protect the

Environment

Richard A. Kohn*

University of Maryland, College Park, USA

Abstract

Animal production systems are among the largest contributors of reactive nitrogen to the environment. Nitrogen (N) is lost from animal agriculture through volatilization to the atmosphere (NH3, N2O, NO) and runoff and leaching to water resources (NH4+,

NO3–, organic N). Most N losses from agriculture are in a form (NH4+, NH3, NO3–) that does not directly affect climate change.

However, these compounds have serious environmental consequences of their own, including contributing to haze, acidity of rain, eutrophication of surface water bodies and damage to forests. In addition, a significant amount of nitrous oxide (N2O) emissions result from animal agriculture because the ammonium and nitrates from agriculture are converted to N2O during manure storage and crop production. N2O is a potent greenhouse gas. Although animals emit very little nitrogen directly to the air, animal excreta (urine and faeces) contains environmentally reactive nitrogen, which begins moving to the air and water from the moment it leaves the animal, unless it is incorporated into a crop or converted to molecular nitrogen (N2). Nitrogen is lost from the barn floor or pen, storage facility and from cropland during manure application and crop growth. Additional nitrogen is lost to the environment when

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18 Residual Feed Intake and Breeding Approaches for Enteric Methane Mitigation

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18

Residual Feed Intake and

Breeding Approaches for Enteric

Methane Mitigation

D.P. Berry,1* J. Lassen2 and Y. de Haas3

1Animal

and Grassland Research and Innovation Centre,

Teagasc, Fermoy, Co. Cork, Ireland; 2Aarhus University, Tjele,

Denmark; 3Wageningen UR Livestock Research, Lelystad, the

Netherlands

Abstract

The expanding world human population will require greater food production within the constraints of increasing societal pressure to minimize the resulting impact on the environment. Breeding goals in the past have achieved substantial gains in environmental load per unit product produced, despite no explicit inclusion of environmental load (and in most instances, even feed efficiency) in these goals. Heritability of feed intake-related traits in cattle is moderate to high, implying that relatively high accuracy of selection can be achieved with relatively low information content per animal; however, the genetic variation in feed intake independent of animal performance is expectedly less than other performance traits. Nonetheless, exploitable genetic variation does exist and, if properly utilized, could augment further gains in feed efficiency. Genetic parameters for enteric methane (CH4) emissions in cattle are rare. No estimate of the genetic variation in enteric CH4 emissions independent of animal performance exists; it is the parameters for this trait that depict the scope for genetic improvement. The approach to the inclusion of feed intake or

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