Last update: August 16, 2011 03:27:54 PM E-mail Print


EFFECT OF NUTRITION ON CERTAIN MOHAIR QUALITY TRAITS

 

Margaretha A Badenhorst, J C Diedericks & P A Schlebusch

Grootfontein College of Agriculture, Middelburg Cape, 5900

 

N M Kritzinger

Mohair Board, P O Box 2243, Port Elizabeth, 6056

 

The Angora goat has an exceptional ability to convert available food into fibre and it is deservedly considered to be the most efficient fibre-producing animal species. In addition, as a natural fibre, mohair has certain unique qualities (probably the most important of which is its unparalleled lustre) which make it very sought after. Income from fibre forms by far the greatest part of the total income from Angora goats, and both quantity and the quality of mohair play vital roles in this. For this reason it is logical that, over the years, in the selection of breeding animals, strong emphasis has been placed on both quantity (amount of mohair) and quality (fineness, style and character, lustre, length, etc).

Most stud breeders acknowledge that nutrition should not be a limiting factor in the realization of the full genetic potential of individual animals. Selection is therefore usually done under favourable nutritional conditions. The question arises whether those goats which perform ideally under optimum nutritional conditions, will maintain their performance under less favourable conditions. This trial was therefore aimed at investigating the effect of the level of nutrition on the most important quality traits of mohair.

 

Experimental procedures

The investigation was carried out at the Grootfontein College of Agriculture over a period of six months. Fourty 12-month-old Angora kids were divided into two groups on a stratified mass base, and in such a way that each group contained equal numbers of ewe and wether kids. The kids were shorn just prior to the beginning of the experiment.

Group 1 (High level = HL) received a pelleted ration consisting of 10 per cent mealies, 10 per cent molasses and 80 per cent lucerne, while Group 2 (Low level = LL) received a much less nutritious ration of 70 per cent milled lucerne plus 30 per cent milled wheat straw. Body mass was recorded on a weekly basis. At the end of the experiment, just before shearing, a number of subjective mohair qualities were assessed according to a linear scale ranging from 1 to 50 (Table 1). At shearing, individual fleece mass was recorded and individual samples was taken for determining fibre diameter.

TABLE 1. Linear score card for subjective assessment of various mohair characteristics in Angora goats

Characteristic Score awarded
Style

None

1

Ideal

50

 
Character

Straight

1

Ideal

25

Over-curly

50

Evenness

Uneven

1

Ideal

50

 
Density

Light

1

Dense

50

 
Facial cover

Poor

1

Good cover

50

 
Neck cover

Poor

1

Good cover

50

 
Kemp

Kempy

1

None

50

 


 

The data was analised by means of Least-square-means methods (Harvey, 1990) and the following fixed effects were included in the linear model fitted to the data, namely group (HL & LL), sex (ewes & wethers) as well as a group x sex-interaction.

 

Results

Except for fibre diameter, no significant differences occured between sexes in respect of any of the traits measured. In both groups the average fibre diameter of the ewes was two micron stronger (P<0.05) when compared to that of the wethers.

The effects of level of nutrition on the various mohair qualities are presented in Table 2.

 

TABLE 2. Effect of nutrition on the linear score of various characteristics in Angora kids

Characteristic High nutrition level (HL) Low nutrition level (LL) P
Facial cover 28.15 37.99 **
Neck cover 29.03 39.59 **
Style
29.01 24.30 ns
Character 27.84 17.88 **
Evenness 37.01 37.71 ns
Density 44.53 39.31 **
Kemp 20.95 32.29 **
Initial body mass (kg) 24.63 24.43 ns
Final body mass (kg) 45.55 29.33 **
Fleece mass (kg) 3.70 2.07 **
Fibre diameter (micron) 39.79 30.72 **

 

 

** Significant (P<0.01)

ns Non-significant


From Table 2 it is clear that animals in the HL-group maintained better gains and eventually weighed on average approximately 60 per cent more than LL-group. Mean mohair production of the HL-group was 78.7 per cent higher, and average fibre diameter 30 per cent stronger (39.7 vs 30.7 micron) than that of the LL-group. Furthermore, the HL-kids had significantly (P<0.01) less facial and neck hair covering. In respect of character, HL-animals were inclined to be over-curly when compared to the much straighter hair (P<0.01) of LL-kids. Fleece density and kemp content (as scored subjectively) were both significantly higher in the HL-group. Style and evenness of fleece, however, did not differ significantly between the two groups.

The photograph in Figure 1 was taken six weeks after the beginning of the trial, and even at this early stage, the difference in character and body mass between the HL- and LL-kids was obvious.

 

Conclusions

With the exception of style and evenness of fleece, nutrition appears to have a substantial effect on all the important quantitative and qualitative characteristics of mohair production. The selection of breeding animals based on these qualities can therefore be effective only if all the animals receive the same nutritional treatment. Similarly, the pronounced effect of nutrition, as displayed in this trial, signifies that between-flock comparisons should be treated with great caution. Superior character, for example, may be the result of a high nutritional plane, but when such animals are subjected to nutritional stress, this "quality trait" may largely disappear.

An important finding of this study was that style and character are affected differently by the level of nutrition. This is in accordance with the results of another investigation, into the repeatability of style and character between successive shearings, where it has been found that style has a much lower repeatability than character when measured at 10 and 18 months of age. These findings suggest that style and character cannot be regarded as one combined quality or trait, but must rather be assessed as two separate traits.

 

References

HARVEY, W R, 1990. Mixed Model Least-Squares and Maximum Likelihood Computer Program. Walter R Harvey

 

Published

Angora Goat and Mohair Journal 34 (1) : 28-29Karoo Agric 4 (4) :7-8