REPRODUCTIVE-PERFORMANCE OF COMMERCIAL MERINO, DOHNE MERINO AND SA MUTTON MERINO FLOCKS IN THE SOUTHERN CAPE

Data of 23 189 Merino ewes (8 farms), 7 692 Dohne Merino ewes (3 farms ) and 2 399 SA Mutton Merino ewes (1 farm) were recorded for the 1988- 1991 lambing seasons. The udders of ewes present at lamb marking were inspected to differentiate between barren (unlambed), lambed and lost (lambed ewes suckling no progeny), and wet (lambed and suckling greate r-than-or-equal-to 1 lamb) ewes, using the 'wet and dry' technique. Th e lambs present at lamb marking were counted, and information regardin g number of ewes mated and managerial inputs was recorded. The mean nu mber of lambs marked as a percentage of ewes joined (Lm/Ej) was 87.7% for Merino flocks, ranging between 62.8-103.3%. Figures for Dohne Meri no flocks were found to be similar, ranging between 75.6-113.2% Lm/Ej, with a mean of 92.6%, while Lm/Ej was 112.7% in the SA Mutton Merino flock. Between 72.2% (Merino) and 80.4% (SA Mutton Merino) of joined e wes suckled greater-than-or-equal-to 1 lamb at lamb marking. Mean fecu ndity (estimated number of lambs born as a percentage of ewes lambed) was estimated at 121.6% for Merino ewes, 122.7% for Dohne Merino ewes and 140.2% for SA Mutton Merino ewes. Significant (P less-than-or-equa l-to 0.05) differences in Lm/Ej occurred between Merino and Dohne Meri no ewes stocked on different farms. It was attempted to relate these d ifferences to managerial practices (flock size at mating, mating perio d, percentage of rams, the use of vasectomized rams, the use of ultras onic scanning, and management at lambing). Increasing flock sizes tend ed to be associated with a decline in Lm/Ej. Reproductive efficiency w ithin flocks was independent of the other managerial practices. Ewes w hich failed to suckle greater-than-or-equal-to 1 lamb to lamb marking during 1988-1990 were ear notched (marked). The mean levels of reprodu ctive failure in marked ewes (groups with < 40 marked ewes were exclud ed) were compared with those of contemporaries without a history of re productive failure within lambing years and farms. In 15 groups of Mer ino ewes where this procedure was followed, the number of ewes dry (th e total of the unlambed and lambed and lost categories) as a percentag e of ewes present at lamb marking (Ed/Epm) was 33.7% compared to 24.2% for the 15 groups of contemporaries of these ewes (P less-than-or-equ al-to 0.05). In four groups of Dohne Merino ewes, Ed/Epm was 32.8% for marked ewes and 21.5% for their contemporaries (P = 0.06). It was con cluded that there was scope for the improvement of the reproductive ef ficiency of local woolled sheep flocks. Selection against reproductive failure by using the simple 'wet and dry' technique appears to be a l ow-input method for the improvement of reproductive performance in com mercial sheep flocks, at least in the current flock. Results from the literature suggest that such selection will also benefit future genera tions.