Last update: December 1, 2010 04:12:03 PM E-mail Print





J.H. Hoon, B.R. King & M. van Heerden

Grootfontein Agricultural Development Institute, Private Bag X529, Middelburg, EC, 5900

E-mail: Jan Hoon



With the feeding of ruminants it is important to keep in mind that it is actually the micro organisms in the rumen that are fed. These organisms digest the feed, and the by-products of this process are utilized for maintenance and the production of meat, wool/hair and milk. Growth promoters that are included as additives in complete diets and supplementary feeds, act indirectly to benefit the animal by maintaining the natural balance of the rumen flora in the digestive tract. In this way, overproduction of harmful micro organisms is limited in order to facilitate the absorption of nutrients from the feed.

Studies with cattle have indicated that Flavomycin® (Hoechst Roussel Vet (Pty) Ltd), the antibiotic growth promoter flavophospholipol, manipulates the metabolic processes in the rumen by selectively influencing the growth rate of certain groups of rumen flora. It also promotes the growth of amylolytic and cellulolytic micro organisms, as well as those, which ferment both starch and cellulose. Furthermore, it leads to a quick increase in the numbers of the bacteria that are responsible for the digestion of cellulose (van den Bergh, 1995). All these factors can amount to an increase of up to 15% in the digestion and utilization of cellulose, which should make Flavomycin® a suitable supplement for ruminants under extensive grazing conditions. Positive results have been obtained with the inclusion of Flavomycin® in supplementary feeds for cattle under veld conditions (Morris, 1995), as well as with sheep under feedlot conditions (Murray et al., 1992).

The aim of this study was therefore to determine the effect of the inclusion of Flavomycin® in a combined energy-protein supplementary feed mixture on the performance of sheep during the dry season (winter) under extensive grazing conditions.



The study was carried out under natural veld conditions at the Grootfontein Agricultural Development Institute. Eighty-six young Merino wethers (6-8 months old) were randomly divided into two groups of 43 each and placed into two adjoining camps, comparable in size, vegetation type, vegetation density, etc. One group served as a control and received a supplementary feed mixture, while the treatment group received the mixture + Flavomycin® at the recommended inclusion level of30grm(active)/sheep/day.

The composition of the supplementary feed mixture was as follows;

71 kg maize meal

18 kg salt

6 kg molasses power

1 kg slaked lime (calcium hydroxide)

1 kg dicalciumphosphate 18

for the treatment group, 1.25kg Flavomycin® was added to the mixture.

The duration of the experiment was 100 days (20 June - 29 September). The two groups of animals were rotated every two weeks between the respective camps to eliminate the possibility of a camp effect. Supplementary feed intake per group was determined weekly, while the body weight of the individual animals was determined on a two-weekly basis. The data were analysed statistically by using the GLM-procedures of SAS (Litell et al., 1991). The average daily gain (ADG) of the individual animals was determined by the regression of body weight over the duration (days) of the experiment.



The average daily supplementary feed intake, body weight and average daily gain (ADG) of the two groups of sheep are presented in Table 1.


Both groups of sheep maintained an average supplementary feed intake of about 300gisheep/day, with a slightly higher intake in the control group. No significant differences (P>0.05) were observed between the two groups with regard to final body weight, but the ADG of the individual animals from the treatment group was significantly higher (P>0.05) than that of the control group, despite lower intakes of supplementary feed.



From the results it is clear that the inclusion of Flavomycin® at the recommended level in a supplementary feed mixture had a positive effect on the growth rate of young Merino wethers grazing dry winter veld. Replications of this experiment are, however, essential to quantify the economic benefits of the inclusion of Flavomycin® in supplementary feeds for sheep under extensive grazing conditions more accurately.



Litell, R.C., et al., 1991. SAS System for Linear Models.

Morris, S.D., 1995. Pro Agri 6, 34.

Murray, P.J., et al., 1992. Aust. J. Agric. Res., 43, 367.

Van den Bergh, G., 1995. Pro Agri 3, 22.