- Wooled sheep production in harmony with the extensive grazing areas of South Africa
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WOOL SHEEP PRODUCTION IN HARMONY WITH THE EXTENSIVE GRAZING AREAS OF SOUTH AFRICA
MJ Herselman & MA Snyman
Grootfontein ADI, P/Bag X529, Middelburg, 5900
It is important for small stock farmers in the extensive grazing areas to farm with well adapted animals to ensure maximum production with minimum input costs. Recently, the importance of adaptation of livestock to extensive conditions has again been realized and the terms "well adapted" and "hardiness"are currently widely used in the promotion of breeds and studs. In the past, fibre-producing small stock always fulfilled a vital role in the agriculture of the arid regions. However, adaptation to arid conditions has largely been ignored in selection programs and selection of rams was performed almost exclusively under optimum feeding conditions. This is, however, not the first time that the adaptation of wool sheep to arid regions has been placed under the spotlight.
As early as 1949, a publication with the title "Verloor die Merinoskaap?" has been published in "Boerdery in Suid-Afrika" as a result of a large decrease in wool sheep numbers and an increase in the numbers of mutton sheep. Some of the most serious shortcomings of the Merino mentioned by the authors were low reproduction and low milk production. The conclusion (in Afrikaans) reads as follows: "Genoemde tekortkominge in die Merino hou gevare vir die ras in, maar hierdie gevare kan tot ‘n groot mate uitgeskakel word mits die Merino nie slegs as ‘n wolproduseerder beskou word nie. Dit is gebiedend noodsaaklik dat daar ook aandag bestee moet word aan sy vrugbaarheid en aan die beheer van faktore wat vrugbaarheid direk en indirek benadeel. Die moeder-eienskappe kan verbeter word deur seleksie, deur die lammers met speentyd te klasseer en die ooie met die swakste lammers uit te gooi. As sukses hiermee behaal word, sal die ras baie beter toegerus wees om die mededinging wat dit vandag ondervind, die hoof te bied. Die algemene gerusstellende opvatting dat die Merino as fynwolproduserende ras onontbeerlik is, veroorsaak dat die klem by seleksie en teling slegs op die wol en sy kwalitatiewe en kwantitatiewe eienskappe val. Hierdie toedrag van sake is gevaarlik en kan meer kwaad aan die ras doen as wat al die propaganda en organisasie wat die ras tans geniet, goed kan doen."
The situation today has not changed much since 1949. The movement away from wool sheep to mutton sheep production is still continuing in the extensive grazing areas. Furthermore, the Merino is still characterized by relative low reproduction and growth rates under extensive conditions. However, the Merino remains the most important sheep breed in South Africa and there is a growing realisation among producers and breeders that is has become essential to genetically improve the adaptation of the Merino to extensive grazing conditions.
In the context of this presentation, adaptation refers to the ability of animals to survive, to reproduce and to produce under extensive grazing conditions such as the arid Karoo. In this regard, it follows that total weight of lamb weaned (kg lamb weaned/ ewe/ year) would be a useful measure of adaptability.
2. IMPORTANCE OF ADAPTABILITY IN WOOL SHEEP
The relative importance of adaptability in wool sheep is primarily an economic issue. Although the Merino is a wool sheep, it should actually be seen as a dual purpose breed as approximately 50 % of its income is generated by mutton. Due to the sensitivity of reproduction and growth to environmental conditions, it follows that the economic importance of adaptation is mainly related to the mutton production function. Therefore, it can be assumed that adaptation in wool sheep is of less importance than in mutton sheep where total income is dependent on mutton production. This, however, does not mean that adaptability of wool sheep to extensive grazing conditions can be neglected. On the contrary, adaptability is the most important characteristic which can be genetically improved to ensure that wool sheep production remains economically competitive to mutton sheep production.
3. HISTORIC REASONS FOR ADAPTATIONAL PROBLEMS IN WOOL SHEEP
Probably the most important reason why wool sheep is not well adapted to arid, extensive grazing conditions can be related to the environmental conditions where these sheep genetically originated from and where they have been selected and bred for many years. Traditionally, stud breeders of wool sheep ran their animals under favourable nutritional conditions such as irrigated pastures or with supplementary feeding, whereas commercial producers were dependent on natural grazing in the extensive areas. In other words, rams bought by commercial producers for production under extensive conditions were bred under favourable nutritional conditions. This would not have been a problem if no genotype x environment interaction was involved. Several studies, however, revealed that individuals which produce best under favourable conditions do not always produce best under less favourable conditions. In one such a study, Hart et al. (1993) reported that when Angora, Nubian and Alpine goats were run on improved pastures during the winter, Angora goats had the highest growth rate. In another group which were run on natural grass, Angora goats had the lowest growth rate (Figure 1). This is a clear example of a genotype x environment interaction where the breed which was superior in one environment was not superior in another.
Figure 1 Growth rate of different goat genotypes on improved pasture and dry natural grass
In another study a progeny test was performed using two different Merino genotypes (Cloete & Olivier, 1995). One group of rams from the Tygerhoek Control flock and another group from the Grootfontein Merino stud were mated to Merino flock ewes. In the Tygerhoek Control flock no selection has been performed since 1968, while selection using the latest technology has been performed in the Grootfontein Merino stud over the years. Furthermore, the Grootfontein Merino stud is kept under favourable nutritional conditions which include irrigated pastures and supplementary feeding. Progeny born were either kept on natural Karoo veld or in a feedlot. The production of the progeny born are shown in Table 1. In the feedlot, clean fleece weight and body weight were, as expected, higher for the Grootfontein Merino rams which have been selected for these parameters over many years. However, under veld conditions clean fleece weight and body weight were higher in the progeny of Tygerhoek rams compared to Grootfontein rams. In other words, the selection performed in the Grootfontein Merino stud over many years under favourable nutritional conditions had no advantage if these animals are kept under marginal Karoo veld. It can therefore be speculated that genetic changes in most wool sheep studs of the past contributed little to increased productivity of commercial flocks. On the contrary, there is a possibility that genetic change to some characteristics of wool sheep was to the detriment of the adaptability of these breeds and therefore to commercial producers.
Table 1 Production of the progeny of Grootfontein stud rams compared to Tygerhoek control rams when used on commercial Merino flock ewes.
Grootfontein Tygerhoek Grootfontein Tygerhoek
Body weight (kg) 41.8 43.2 91.3 89.9
Clean fleece weight (kg) 3.4 3.5 8.4 7.9
Furthermore, income of stud breeders and of commercial producers is generated from different products. The stud breeders sell rams whereas the commercial producers sell wool and surplus lambs. In their selection and breeding programs, stud breeders attempted to breed animals which conformed with the breed standards, which looked good, which had a superior conformation and with wool of good quality, staple formation, etc. On the other hand, income of commercial producers is dependent on characteristics such as reproduction rate, survival rate, growth rate, carcass quality , wool production and fibre diameter. This situation, where the selection objectives of the stud breeders were in conflict with that of commercial producers, contributed further to animals been bred which were not best suited for commercial wool sheep production under extensive conditions.
Another contributing factor to adaptational problems in wool producing sheep can possibly be related to negative correlated responses when selecting for increased wool production. Considering different wool sheep breeds in practice, it is evident that amount of wool is negatively related to body weight. For example, the Merino has a relative high wool production function but a relative low body weight when compared to the Mutton Merino or the Dohne Merino. This trend is also evident when comparing different lines within the Merino breed. As reflected by observations on ewe productivity (kg lamb weaned/ewe/year) in practice, it is also clear that breeds with a high wool production function are usually less adapted to extensive grazing conditions than breeds with relatively low wool production functions. This trend is clearly illustrated by the data in Table 2 which were collected for Afrino and Merino sheep at the Carnarvon Experimental station and at Grootfontein (Herselman et al., 1998).
Table 2 Mean body weight (BW), clean fleece weight (CFW) and wool production potential (WPP=CFW/BW) of Merino and Afrino ewes at 18 months of age as well as ewe productivity (EP) over three lambing seasons
Carnarvon Carnarvon Grootfontein
n 609 2234 1616
BW (kg) 47.9 ± 0.100 32.0 ± 0.04 42.8 ± 0.05
CFW (kg) 2.01 ± 0.009 2.60 ± 0.003 4.8 ± 0.006
WPP (%) 4.21 ± 0.02 8.15 ± 0.01 11.24 ± 0.02
EP (kg) 116.8 ± 1.28 38.3 ± 0.44 90.2 ± 0.82
As these observations reflects the general trends among different genotypes, it is necessary to consider these relationships within breeds or flocks to comment on possible associated responses with selection and breeding of wool sheep.
Using the same data as in the previous table, it is evident that within flocks, clean fleece weight and ewe productivity was generally uncorrelated (Figure 2). In Figures 2 - 4 each data point represents the mean of 50 ewes. Within flocks, EP was directly related to BW (Figure 3), a phenomenon similar to the one observed among flocks. This is in accordance with numerous reports (Cloete & Olivier, 1995; Fogarty, 1995; Snyman et al., 1997) which revealed positive genetic and phenotypic correlations between body weight and reproduction rate. Neither the intercepts, nor the slopes of the regression of EP on BW differed among flocks. Thus, EP was directly related to BW irrespective of breed or environmental conditions. Ewe productivity was also negatively related to wool production potential (WPP), which is the amount of wool produced per kg of body weight (Figure 4). In other words, small animals with relative high wool production are associated with low ewe productivity. It can therefore be assumed that any selection program of the past with the net result of increased WPP would have had a detrimental effect on ewe productivity irrespective of breed or environment.
Figure 2 Relationship between clean fleece weight (kg) and ewe productivity over three lambing opportunities (kg lamb weaned / ewe) in the Carnarvon Merino and Afrino flocks and in the Grootfontein Merino stud
Figure 3 Relationship between body weight (kg) and ewe productivity over three lambing opportunities (kg lamb weaned /ewe) in the Carnarvon Merino and Afrino flocks and in the Grootfontein Merino stud
Figure 4 Relationship between wool production potential (%) and ewe productivity over three lambing opportunities (kg lamb weaned /ewe) in the Carnarvon Merino and Afrino flocks and in the Grootfontein Merino stud
As far as the reasons for adaptational problems of wooled sheep to extensive grazing areas are concerned, it can be concluded that, amongst others, the following three factors might have been involved. Firstly, due to genotype x environment interactions and favourable nutritional conditions, genetic changes in wool sheep studs in the past were not to the advantage of animals kept under arid conditions. Secondly, selection objectives of stud breeders did not include aspects of adaptation to extensive conditions. Lastly, too much emphasis on wool quality and quantity and to little on body weight could have resulted in increased wool production potential, which is negatively related to adaptation.
4. ECONOMIC ASPECTS OF WOOL SHEEP IN ARID AREAS
From the foregoing it can be argued that in wool sheep, not well adapted to a specific environment, income from wool would be a relative large proportion of total income because reproduction and therefore income from mutton would be low. To illustrate the characteristics within a flock which influences income, data from the Carnarvon Merino flock were again used. For the purpose of this, it was assumed that the clean wool price was twice as high as the mutton price and that each ewe was shorn four times until her third parity. Income for each of 1786 ewes which had at least three lambing opportunities was calculated. Subsequently, ewes were divided into three groups according to income, namely low, average and high (Table 3). The most striking result in Table 3 is the high ewe productivity associated with the high income ewes, which confirms the importance of mutton as source of income in wool sheep. Furthermore, high income was also associated with high 18-month body weight and a somewhat lower WPP. From this it is clear that adaptability of wool sheep to extensive conditions is the most important characteristic which can contribute to the economic success of wool sheep farming in those areas.
Table 3 Division of 1786 ewe records of the Carnarvon Merino flock into three income categories
Category n Income (R) BW (kg) CFW (kg) WPP (%) EP (kg)
Low 595 42.67 30.2 2.4 8.14 23.2
Average 595 61.64 32.1 2.6 8.04 40.8
Best 596 84.29 34.2 2.8 7.89 62.2
BW = 18-month body weight (kg)
CFW = 18-month clean fleece weight (kg)
WPP = Wool production potential (%)
EP = Ewe productivity; total kg lamb weaned during first 3 parities
From Figure 5 it is also evident that by increasing wool production per se, only a relative small increase in lifetime income of a ewe can be expected. On the other hand, by selecting for reproduction and growth aspects (adaptation) dramatic increases in lifetime income can be brought about.
(a) (b) (c)
Figure 5 The relationship between clean fleece weight (a), ewe productivity (b), wool production potential (c) and total income in the Carnarvon Merino flock
5. STRATEGIES FOR BREEDING BETTER ADAPTED WOOL SHEEP
From the foregoing it is evident that increased ewe productivity is essential for increased economic efficiency of wool sheep in extensive grazing areas. This can be achieved by farming with animals better adapted to these conditions. However, it is essential that existing shortcomings in the stud and commercial sectors of the wool sheep industry, which have been discussed earlier, are properly addressed. It should, however, be mentioned that stud breeders cannot be blamed for the current situation where selection practices in the stud industry are not always to the advantage of commercial producers. As long as commercial producers are not prepared to pay a premium for animals bred specifically for their needs, this situation will not improve. It is therefore essential to put forward a strategy to bring stud breeding in line with the requirements of commercial producers.
Firstly, to ensure increased efficiency of production in commercial flocks, stud breeders must strive to increase the efficiency of their stud animals under commercial conditions. This can only be achieved if stud breeders will perform their selection and breeding programs under natural conditions. It is recommended that selection under natural grazing conditions in Merino sheep should be focused on :
* Increasing reproductive rate and ewe productivity
* Increasing the animal's own growth performance (body weight)
* Decreasing or maintaining fibre diameter
* Increasing or maintaining fleece weight
The feasibility of any breeding plan depends upon the number of records the breeder or producer has to keep. The aim with the recommended breeding plan is to achieve maximum gains with the minimum record keeping. For efficient selection, it is proposed that the following records be accurately kept by Merino stud breeders :
* Record of ewes mated
* Record of ewes that failed to lamb
* Parent-offspring identification if selection is to be performed on BLUP of breeding values
* Weaning weight of all lambs (used to calculate ewe productivity)
* Body weight of all animals (at 10 - 12 months of age)
* Fibre diameter (at 10 - 12 months of age)
* Fleece weight (at 10 - 12 months of age)
These records could then be used to implement the following breeding plans for Merino rams and ewes :
Selection of breeding sires
All the information needed for the selection of potential sires are available at an early age. Selection can therefore be based on a selection index incorporating the relevant objective traits. It is important that breeders use a selection index which concurs with their specific selection objectives. Traits such as breed standards, conformation and wool quality could be assessed subjectively and rams which meet these requirements could then be selected on the basis of a selection index. Snyman et al. (1997) indicated that there is a high genetic correlation between body weight and ewe productivity. This implies that ewe productivity can be improved genetically through selection based on body weight. Reproduction can therefore be taken into consideration by the inclusion of body weight in the selection index. Alternatively, rams could be selected on the ewe productivity of their dams.
Selection of ewes
At selection age, ewe productivity of the young ewe’s dam is the best predictor of lifetime reproduction of the young ewe. After the first parity, ewe productivity of the young ewe herself also gives the best indication of her lifetime reproduction in the current flock. The high genetic and especially phenotypic correlations estimated between ewe productivity after the first parity and future performance indicate that selection based on ewe productivity will ensure that the highest producers will be selected and therefore that gains in the current flock would be increased. It is therefore recommended that ewe selection should take place in two phases.
In the first phase, ewes could be assessed subjectively for breed standards and conformation or wool faults. Preliminary selection on the basis of a selection index could be done. The same selection index as for ram selection could be used, or one placing less emphasis on fleece weight and fibre diameter and more emphasis on body weight. As the production traits contribute much less to total productivity than the ewe's lifetime reproductive performance, more than the required number of young replacement ewes should be selected during the first phase. These ewes should then be mated and final selection (second phase) could be done after their first parity. With the second phase of ewe selection, selection should be based solely on reproductive performance. Ewes that failed to lamb or has below average ewe productivity after the first lambing opportunity, could be culled. Additionally, adult ewes with low ewe productivity values should also be culled.
Furthermore, the current situation, where selection practices in the stud industry is not to the advantage of commercial wool sheep production, can largely be ascribed to commercial producers paying a premium for well fed rams. They are, however, often disappointed with the unsatisfactory performance of these rams under commercial conditions. It is therefore proposed that commercial producers only buy rams from stud breeders whose farming practices and selection objectives are in accordance with the objectives of their own commercial enterprise. Commercial producers should also insist on records for rams they are buying from stud breeders. However, before commercial producers are not educated to interpret these records they will not be able to realize the value of it. Commercial producers should in future be willing to pay a premium for unfed or veld rams and for rams supplied with the necessary records. In other words, they should stop supporting the very system which they are criticising.
Finally, the commercial producer should concentrate his efforts on current flock gains, as genetic gains will entirely be due to the efforts of his ram supplier. Ewe selection could be done by culling young ewes that fail to wean a lamb or has below average ewe productivity. For selection to be based on ewe productivity, records of ewes mated, dam-offspring identification and weaning weight of lambs should be kept. However, the keeping of records under extensive conditions is not an easy task and many commercial producers would not be able to do this, or be unwilling to make the extra inputs required for the keeping of the necessary records. Due to increasing input costs, commercial producers can not afford to keep unproductive ewes in the flock. It is therefore recommended that records of ewes that failed to lamb should at least be kept. By culling such ewes, genetic progress with regard to reproduction could be achieved in the flock.
Despite the fact that the Merino is still the largest sheep breed in South Africa, it is alarming that wool sheep has totally disappeared from certain areas. To prevent further decreases in wool sheep numbers, it has become necessary to do something drastic about the adaptation of these sheep to extensive grazing areas. Although some initiatives such as veld ram clubs and group breeding projects are promising, to little emphasis is still placed on the genetic improvement of reproduction in wool sheep.
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Herselman, M.J., Olivier, J.J. & Snyman, M.A., 1998. S.Afr. J. Anim. Sci., 1998 (In press).
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Snyman, M.A., Olivier, J.J., Erasmus, G.J. & Van Wyk, J.B., 1997. Livest. Prod. Sci., 48(2), 111