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Effect of level of supplementary feeding on Mohair production and reproductive performance

of kraal-fed Angora ewes

 

P.R. King, V. Sumner, D. Wentzel, P. Schlebush and M.J. Herselman

Grootfontein Agricultural Development Institute,

Private Bag X529, Middelburg (EC) 5900

 


Introduction

The relatively big difference in price between adult and kid's mohair is of great importance to the mohair producer when deciding on a production system. This price difference is inevitably forcing the producer to increase the production of kid's mohair. However, certain factors prevent the producer to increase the production of kid's mohair. Firstly, the relatively low reproductive performance of Angora goats under extensive conditions is a major limiting factor. Other factors are exceptionally high losses from birth till weaning (12,5 %) and between weaning and 18 months of age (12,5 %) (Terblanche 1988) as well as the poor growth rate from weaning until 18 months of age (Van der Westhuysen et al. 1988).

These problems can to a large extent be overcome by energy supplementation. The energy supplementation of Angora goats, however, can also have a detrimental effect as fibre diameter of the fleece produced is directly correlated to the nutritional status of the animal. Excessive supplementation could lead to the production of over-strong mohair (above 39 microns). In the traditional mohair producing areas, some Angora goats are run on irrigated lucerne pastures during the summer months. During the winter months a large proportion of these goats are kept under intensive conditions and are fed lucerne hay. Sufficient evidence exists that lucerne hay alone cannot satisfy the energy requirements of pregnant and lactating Angora ewes. In view of the above mentioned problems this experiment was undertaken to establish the optimal level of energy supplementation required for reproducing ewes receiving lucerne hay.  

 

Materials an d methods

Two weeks before mating 100 newly shorn adult Angora ewes were randomly allocated to the treatment groups given in Table 1.

Each group was kept in a separate pen for the duration of the experimental period. Lucerne hay was given on an ad lib basis. Ewes had access to a roofed enclosure during wet, cold spells. Alkali-ionophore-treated whole maize was prepared by adding a mixture of 20 l of water, 16 l of molasses, 8 kg urea, 12,5 kg calcium hydroxide and 100 g Taurotec to 560 kg of maize. The alkali-ionophore-treated maize was fed daily. Live body mass was recorded at weekly intervals. Two weeks after commencing with flushing  the ewes were hand mated twice daily to Angora rams for a six week period.

The ewes were shorn at six and 12 months after the onset of the experimental period, while the kids were shorn at six months of age. The following mohair parameters were recorded for each animal using standard techniques : greasy fleece mass, percentage clean yield, clean fleece mass, fibre diameter and straight fibre length. Reproductive data collected included birth status, birth mass of kids and number of abortions. The body mass and mohair data of the kids were corrected for sex and birth status before statistical analysis. Experimental data were analysed by analysis of variance as described by Snedecor & Cochran (1967).

 

Results and discussion

Body mass recorded at four different stages of the experimental period namely, the onset of the experimental period, two weeks before the lambing season, the peak of lactation (six weeks after lambing) and at weaning is given in Table 2.

From Table 2 it is evident that none of the treatment levels had any effect on body mass at any stage of the experiment. This result was contrary to what was expected as it has been reported that the supplementation of Angora goats has a considerable effect on body mass. According to Hobson et al (1986) body mass of Angora goats grazing Atriplex nummularia (Oldman saltbush) during the gestation period was closely related to the amount of energy supplementation. In their study, body mass of the group receiving 600 g chocolate maize/ewe/day increased with 30,45 % over the gestation period, compared to the 5,7 % of the control group.

Loubser (1983) recorded an increase of 3,8 kg in body mass of Angora ewes grazing mixed karoo veld supplemented with 400 g chocolate maize/ewe/day, compared to a control group receiving no supplementation. Under veld conditions it is often physically . impossible for the ewe to take in sufficient roughage to meet her nutritional requirements during the last third of gestation and during lactation (Van der Westhuysen et al. 1988). It thus seems that the lucerne fed in this experiment supplied sufficient nutrients to the ewes during periods of higher demand.

The effect of level of supplementation on mohair production and characteristics of Angora ewes and kids is summarised in Tables 3 and 4 respectively.

The rate of supplementation had no significant effect on any of the mohair traits measured. Compared to the national flock producing 4,2 kg mohair per adult goat per year, the ewes in this study produced 5,2 kg/ewe/year, which represents a 23,8 % higher production.

The average fibre diameter of 38,4 microns for the first clip and 37,7 microns for the second clip is at the upper limit of the range for adult mohair (34 to 38 microns). This is further proof of the high level of production maintained by the Angora goats fed lucerne hay and is probably the reason for no effect of supplementation on mohair production.

The reproductive performance of the experimental animals [[able 5) also suggests that Angora goats could satisfy their energy requirements during all stages of the reproductive cycle when fed lucerne hay. The precise reason for the results obtained in this study, namely that energy supplementation does not increase the reproduction rate of the ewes or the production of mohair by the ewes and kids, is not explicable from the results of this experiment because the intake of lucerne hay was not determined.

Several authors (Craddock et al. 1974; Blaxter 1976; Herselman 1990) have reported that dry matter intake is to some degree controlled by energy intake.

In the present study the energy supplementation may have decreased the intake of lucerne hay, which would explain the fact that no differences occurred between treatment groups. Under extensive conditions, the intake of roughage from the veld is suppressed by physical limitations and the supplementation helps to overcome this shortage (Hobson et 01. 1986).

These results would then differ from the present results where no restriction on lucerne hay intake existed. It is furthermore possible that the lower reproduction rate of the treatment groups was the result of a nutrient imbalance caused by a lower intake of lucerne hay and a higher intake of the supplementation.

 

Conclusion

From the results obtained in this study it would seem that lucerne hay fed to reproducing Angora goats in pens, not only satisfies their energy requirements but also boosts production and reproduction to very high levels.

Additional supplementation under these conditions seems to be of no value. However, under sub-optimum conditions, such as low quality veld, it is a known fact that supplementation positively influences most production characteristics.

 

References

BLAXTER, K.L. 1976. Experimental obesity in farm animals.  Proceedings of 7th symposium on energy metabolism.  European Association of Animal Production, 14.

CRADDOCK, B.F., FIELD, R.A.& RILEY, M.I. 1974. Effect of protein and energy levels on lamb carcass composition. Journal of Animal Science, 39:325.

HERSELMAN, M.J. 1990. Die energiebehoeftes van Angorabokke. M.Sc. thesis, University of Stellenbosch, Stellenbosch.

HOBSON, V., GROBBELAAR, P.D., WENTZEL, D. & KOEN, A. 1986. Effect of level of supplementary feeding on mohair production and reproductive performance of Angora ewes grazing Atriplex nummularia (Oldman saltbush). South African Journal of Animal Science, 16(2):95.

LOUBSER, P.G. 1983. Die effek van prikkelvoeding op die reproduksievermoë van Merinoskape en Angorabokke.  Karoo Agric, 3(1):21.

SNEDECOR, G.W. & COCHRAN, W.G. 1967. Statistical methods. Sixth edition. Iowa, USA: Iowa State University Press.

TERBLANCHE, E.LE F. 1988. 'n Ondersoek na Angorabok-boerdery in die Republiek van Suid-Afrika. Boeremakelaars (Koöp).

VAN DER WESTHUYSEN, J.M., WENTZEL, D. & GROBLER, M.C. 1988. Angora goats and mohair in South Africa. Port Elizabeth: MKB Printers.