It well recognized that the main profit driver in any livestock farming enterprise is efficient reproduction. In woolled sheep, the total weight of lamb weaned represents the total outcome of the reproductive cycle of the ewe. This trait is currently receiving more attention by Dohne Merino breeders to increase profitability.
Dohne Merinos were selected for reproduction under adverse environmental conditions long before the formal founding of the breed society 50 years ago. In fact the very reason for developing the breed was to breed hardy and adaptable woolled sheep for the extremely harsh high rainfall and cold conditions of the Eastern Cape Sour veld areas. In the process of breed development, reproduction under natural conditions, was a main selection criterion as explained in detail by JC McMaster in his latest book “Birth of a Breed – The Dohne Merino Story”.
When the Dohne Merino breed expanded to areas better suited to woolled sheep, a dramatic increase in the breed’s reproduction and growth rate was experienced. In fact the international success attained by the breed, can to a large degree be ascribed to this extremely important attribute. Reproduction rate of the breed is not only monitored on a continuous basis but measures to retain and improve the inherent reproduction potential of the breed are constantly revised.
Current level of reproduction
The accompanying graph indicates a substantial increase in not only the total number of Dohne Merinos registered since 2008 but also in the number of multiple born animals. Since 2012 (1673 or 10 percent) more twins than singles were registered at the breed society. The increase in the number of triplets registered (more than 1600 per annum), actually forced a change to the model used for breeding value evaluations.
The obvious reason for such a dramatic increase in reproduction is of course the growing use of accelerated reproductive techniques (Synchronization of ewes, artificial insemination accompanied by hormonal treatment etc.). Improved management procedures such as the use of lambing pens, to not only identify lambs correctly, but to improve bonding between mothers and multiple lambs also contributed to this improvement in the number of multiples registered.
Breeders are now confronted with the question whether the use of these so-called “artificial” but in a physiological, nutritional management sense, advanced techniques, is justified.
The answer is of course not simple. In economic terms even commercial farmers who mastered these more advanced techniques, are farming more profitably. From a breed perspective, it is crucial to retain hardiness and various options have to be considered to maintain and even improve on the current levels of adaptability and reproductive fitness of the breed.
Current methods employed
The main selection criterion in the breed is in the form of a selection index for which minimum standards of overall efficient productivity are applied (see article by WJJ Olivier in this journal). The selection index incorporates breeding values for growth rate, clean fleece mass and fibre diameter. Growth rate is separated into a direct and maternal component. The weaning weight maternal component obviously promotes maternal ability of ewes and contributes towards pursuing the ultimate objective of hardiness and fitness. The extremely high correlation with 12 months body weight also implies indirect selection for lambing percentage. On sales catalogues, it is standard procedure to indicate the birth status of rams as well as the lifetime lambing performance of their mothers. Lately buyers are taking note progressively more of these figures which is a more direct indication of reproductive performance.
At the past World Merino Conference at Stellenbosch, Mr. JC McMaster pointed out that the reproduction of registered Dohne Merinos increased linearly in relation to the decline in wool production potential (WPP%) from 7 to 8 percent down to 5 to 6 percent. Breeders can however not rely on an unlimited decrease in WPP% to promote reproduction.
Another measure used on a within flock basis is based on lifetime records of ewes that also incorporate total weight of lamb weaned. More prominent breeders frequently select top performing ewes on this basis for the purpose of laparoscopy and embryo transfer.
One such example is the Weska stud consisting of 575 ewes. In this flock, for the past 3 years, laparoscopy was used as standard practice to identify parentage and two lambing seasons is employed. However ewes are generally allowed one lambing opportunity per year. The most recent registration record for this stud, indicate 996 lambs born across the two most recent lambing seasons. A total of 773 lambs were the result of laparoscopy and 223 lambs from natural mating (follow up rams and natural mating). Recently 14 ewes were selected for embryo transfer with the following performance figures:
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Embryos from these older ewes with accurate records will be used to promote reproduction in this flock already operating at extremely high reproduction rates. According to Mr. Wessels he is also selling embryos to recover the costs of this expensive operation. Lambing pens on lands are used as standard management practice to increase income from fewer but more productive ewes. Interestingly enough, the lambing pens are also used to identify poor mothers. By means of close observation, ewes that do not bond easily with lambs are culled immediately and the wet and dry method (see article by AJ Fourie elsewhere in this journal) is applied six weeks after lambing.
Obviously the Weska stud is following the route of intensification (see article by AJ Fourie) to farm more profitably. From only the numbers of lambs available per breeding ewe it is clear that this enterprise is extremely successful!
Reproduction records available to Dohne Merino breeders provide the necessary means to further improve on the current high rates of reproduction. Dohne Merino breeders are therefore urged to pay special attention to this strong point of the breed, especially when intensifying their enterprise. By making full use of available options, not only can commercial profitability be increased but more importantly the scope for selection can be increased dramatically.
A dual purpose breed such as the Dohne Merino, should, against the background of possible intensification, seriously consider the possibility of changing minimum performance standards for ewe selection to include some measure of ewe productivity and/or reproduction.
The Editor express his gratitude towards Mr. DH Wessels for his consent to make use of his data