Nutritional improvements using diets and novel feed additives to enhance overall efficiency of beef production including meat quality and mitigation of greenhouse gas emissions as identified by characterisation of the rumen microbial population

Project number:                    72207

Lead contractor:                   SRUC

Partners:                                  The Rowett Institute, Bristol University

Start & end date:                   01 October 2012 – 01 December 2015

 

The Problem:

The potential of feed additives to improve feed efficiency and consequently improve profit margins show considerable promise but further research is required.  Additives could also play a role in reducing methane emissions to help the sector meet the targets of the UK Climate Change Act.   Up to date information on the long term effects of commercially available additives on different breeds and feed rations is required to better advise the beef production industry.

 

Project Aims:

  • To investigate the effect of different diets in combination with novel candidate feed additives and their interaction with methane emissions, performance and efficiency in different breeds of beef cattle
  • To assess the changes in rumen function by characterising the rumen microbial population differences as a result of different diets and feed additives in different breeds of beef cattle
  • To assess the changes in rumen function by repeated rumen sampling to determine the long-term effect of feed additives on methane emissions, performance and efficiency in different breeds of beef cattle
  • To investigate the influence of different diets, feed additives and breeds on carcass and meat quality (sensory characteristics, colour and fatty acid profiles) and shelf life
  • Nutritional and economic modelling to identify the best nutritional strategy for improving overall economic beef production efficiency considering scenarios of mitigation of greenhouse gas emissions and improvement of meat quality.

 

Approach:

A total of 144 finishing beef cattle (steers) will be studied (72 in each of two consecutive years). In the first evaluation trial, two contrasting breeds (Charolais and Luing) will be used from those available at the Beef Research Centre, SAC. In the second validation trial, two further breeds (Aberdeen Angus and Limousin sired) will be used to obtain information from a wide spectrum of breeds.

Animals will be studied during the final 3 months of finishing before slaughter at approximately 18-20 months of age. In each year, cattle will be fed one of two diets (concentrate based or forage based), with and without selected feed additives (provisionally, allicin based or nitrate based) and balanced across breeds.

Feed efficiency, productivity, methane emissions, rumen microorganism population and meat quality measures will be monitored using specialised equipment and novel techniques available at the SAC beef research unit.

 

Deliverables:

Information on the effect of feed additives on cattle production, methane emissions and meat quality for different breeds, diet types and their long term efficiency.

Improved understanding of interactions between rumen microbial populations and methane emissions.

Cost-benefit calculations of feed additives for different system types.

 

Results

Enteric methane emissions from livestock account for 39% of the global emissions from livestock supply chains.  Some feed additives can potentially improve feed efficiency and consequently profit margins at the same time as reducing methane emissions.  A project led by the Scottish Rural College (SRUC) and involving the Universities of Aberdeen and Bristol has recently completed its work to better understand the long-term effects of two commercially available additives on methane emissions, cattle performance and meat quality when fed with different finishing rations to a range of cattle breeds.

 

Study outline

Two types of additives 1.   nitrates (calcium nitrate)

2.   oils (rapeseed cake or maize distillers grains)

Two basal finishing rations 1.    mixed forage/concentrate ration (50-58% DM as grass silage and barley whole crop silage)

2.   concentrate based ration (74% DM rolled barley).

Four breeds – all steers

 

 

1.   Charolais cross

2.   Luing

3.   Limousin cross

4.   Aberdeen Angus cross

 

Key findings

  • Cattle performed well on all rations with growth rates ranging between 1.2-1.8 kgLW/day and no adverse effects on animal health were observed when nitrate was fed.
  • The effects of nitrate or oil additives on methane production depended on the basal diet fed.
  • When added to the mixed forage/concentrate diet, nitrate and oil reduced methane emissions by 9-17% and 4-7.5%, respectively.
  • The effects of the two additives on methane production were additive when fed in combination in a mixed forage/concentrate ration.
  • On the concentrate diet neither oil nor nitrate additives reduced methane emissions
  • Analysis of the rumen microflora showed a greater number of Selenomonas ruminantium (capable of reducing nitrate) in the rumen of animals offered concentrate diet, which may provide an explanation for the absence of a reduction in methane when Nitrate was added to this diet
  • Following an appropriate adaptation period feeding nitrate alone or in combination with oil with either the concentrate or the mixed ration did not cause any measurable adverse effects on cattle health or performance.
  • Using rapeseed cake to increase the oil content in the ration from 2.7 to 5.1% in the DM did not suppress feed intake or reduce live weight gain. Nor did using maize distillers dark grains to increase oil content in the ration to 3.7% DM.
  • No effect on carcase traits nor meat quality was seen with either additive.
  • Loin steaks from animals fed the mixed diet had significant higher Vitamin E content and longer shelf life (17 v. 15 days) than those fed the concentrate based diet.
  • There were no feed additive x breed interactions
  • Nitrate showed inconsistent effects on performance with growth rate and feed conversion efficiency being lower in cattle fed mixed diets containing nitrate compared to those not containing nitrate in one out of the two studies

Notes:

    • Cattle were introduced to diets containing added nitrate during a four week adaptation phase when the amount of the additive was gradually increased to the required level.  
    • Rapeseed cake is different from rapeseed meal, each having oil contents of 17.2 and 2.8% in DM, respectively.
    • An upper limit of 6% of oil in the diet DM is recommended to avoid any disruption to rumen digestive function which can occur with excessively high oil diets

 

 Table 1: Intake and methane emissions produced from cattle fed either forage or concentrate rations with different additives

Basal diet Mixed forage/concentrate# Concentrate*
Additive None Nitrate Oil None Nitrate Oil
Dry matter intake

(kg/hd/day)

12.1 12.2 11.8 11.2 10.9 11.0
Methane emissions (g/kg DMI) 25.1 20.6 23.2 14.6 15.4 15.7

 

# wholecrop barley silage, grass silage, rolled barley, rapeseed meal, molasses, minerals

*  rolled barley, straw, rapeseed meal, molasses, minerals

 

Commercial messages

Concentrate based diets resulted in lower methane emissions than mixed forage /concentrate rations, regardless of cattle breed.

When added to the mixed forage/concentrate diet, nitrate and oil reduced methane emissions by 9-17% and 4-7.5%, respectively.

Whilst feeding a nitrate additive has some advantages in terms of reducing methane, in both trials its use was not financially attractive. In addition, to avoid potential effects from toxicity, a careful diet preparation and adaptation period must be implemented.  Consequently, without incentives for farmers to reduce methane emissions, nitrate feeding cannot be recommended on commercial beef farms from this work.

Feeding high oil feedstuffs in finishing cattle diets to reduce methane emissions can be recommended provided its use is economically competitive and excessive oil levels (>6% in DM) in the diet are avoided.