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The FFC – Information – Livestock Management – The Effect of Effective Microorganisms on Lamb Growth Rates

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By Kathrin Richter and Ivan Barnett BHU Organics Trust

August 2003


A microbial inoculant, Effective Microorganisms (EM – from New Zealand Nature Farming Society) was tested for effect on lamb growth rate.  Several preparations including EM as bought and EM ‘activated’ by further fermentation as well as EM extracts containing no live organisms were tested as drenches.  Live weight of treated lambs was monitored over a six-week period.

Materials and Methods

The EM preparations compared included EM1 (the bought stock version of EM) at 4 mL per lamb, Activated EM or AEM (EM1 that has been fermented with water and molasses according to manufacturers instructions) at 4 mL and at 40 mL per lamb and extracted versions (no live organisms present) of both EM1 and AEM at 4 mL per lamb.  Treatments were administered as one-off doses at the start of the trial.

Controls included a treatment of 4mL water (control) and no drench (nil control).  For each of the seven treatments, 20 tagged lambs were treated.  Lambs were weighed on the first day, grazed on kale, weighed three weeks later and then grazed on pasture before a final six-week weighing.  Weights were compared on an individual lamb basis to allow statistical analysis.

Table 1: Treatments

Treatment Code



Control Water

4 mL

Nil Control None
EM1 X4 EM1

4 mL

AEM X4 Activated EM

4 mL

AEM X40 Activated EM

40 mL

EM1 Extract X4 Extracted EM1

4 mL

AEM Extract X4

Extracted Activated EM

4 mL

Table 2: Experiment Dates



5 February 2004

Lambs Drenched, Initial Weighing, put onto kale

27 February 2004

Lambs Weighed, put onto pasture

18 March 2004

Final Lamb Weighing

Results and Discussion

Overall lamb growth rates were low in the first three weeks on kale with a mean growth rate of (68 grams per day).  Growth rates increased significantly in the next three weeks on pasture (337 grams per day).  It is likely that climatic factors were involved in the poor weight gain of the first three weeks (as neighbouring farmers reported similar poor lamb weight gains at this time).  It is also possible that some of the final 3 weeks weight gain was compensatory growth after that period of poor growth.

There was a statistically significant difference between the EM treatments and control in the first three weeks of the trial.  No statistically significant difference was seen in the final three weeks though the EM treated lambs generally gained less weight than control lambs (possibly indicating a compensatory growth effect).  In the first three weeks, EM treated lambs grew an average of 77 grams per day compared to control at 49 grams per day (nil control and drench control combined) representing a percentage increase in weight gain of 56% over control (significant, p=0.03, one tailed t-test of mean results).  In the final three weeks, EM treated lambs grew 331 grams per day and control lambs 351 grams per day (not statistically significantly different).  Over the full six weeks EM treated lambs gained 3.3% more liveweight than control lambs from the one-off drench treatment.

No statistical differences could be proven between individual treatments though the tendency for the extracted EM treatments to perform better than other treatments over the six week period should be investigated further.  In fact, the entire experiment would be worthwhile repeating in a period of faster lamb growth rates in the three weeks post drenching (this is key time that responses are expected) to better compare between treatments.  The tendency for drenching to reduce lamb growth rate (seen in the comparison between undrenched lambs and water drenched lambs) may indicate a confounding effect of drenching treatment highlighting the importance of having both a control and a nil control.

Table 3: Mean weight of Lambs over the course of the trial

Treatment Code

Weight gain over first 3 weeks

(g / day)

Weight gain over second 3 weeks

(g / day)

Weight gain over whole 6 weeks

(g / day)





Nil Controla




EM1 X4b








AEM X40d




ExtractedEM1 X4e




ExtractedAEM X4




a two lambs missing for final weighing

b one lamb missing for both three week and final weighing

c one lamb missing for both three week and final weighing

d one lamb missing for both three week and final weighing and two further lambs missing for final weighing

e one lamb missing at three week weighing

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