O.M. Mahmoud and L.K. JajaDepartment of Veterinary Pathology
University of Khartoum
P.O. Box 32
Khartoum North
Sudan
Summary
Resume
Introduction
Materials and methods
Results
Acknowledgements
References
Subcutaneous injection of 250 mg of zinc to desert ewes grazing zinc-deficient pasture increased both conception and lambing rates. Lambs born from ewes injected with zinc were heavier than those born from the undosed ones.
Une quantité de 250 mg de zinc injectée par voie sous-cutanée à des brebis du désert utilisant des pâturages carencés en zinc augmente aussi bien la fertilité que le taux d'agnelage. Les agneaux nés des brebis traités sont plus lourds que ceux non traités.
It has been shown that zinc deficiency causes poor growth, alopecia, skin lesions and mortalities in desert ewes and lambs (Mahmoud et al, 1983) and also that these conditions can be successfully treated by the subcutaneous injection of zinc (Mahmoud et al, 1985). There do not appear to be any reports regarding the effect of zinc injection on the reproductive performance of naturally zinc-deficient sheep, but a deficiency of zinc in the rat affected spermatogenesis and disrupted oestrous cycle and fertility (Ewan, 1978).
This experiment was designed to study the effect of zinc injection on the reproductive performance of naturally zinc-deficient desert ewes.
Two groups of 40 ewes, 2-3 yr old, obtained from Omdurman and Gezira markets were used in the experiment. Group 1 ewes were injected subcutaneoulsy with 250 mg zinc as zinc oxide suspended in olive oil. Group 2 were unclosed controls. The groups were run together as a single flock with 3 breeding rams and were allowed natural grazing only.
Ten randomly selected ewes from each group were bled at 3 mo intervals for serum zinc measurements. Blood was collected from the jugular vein in clean acid washed tubes and allowed to clot and separate overnight. Serum was deproteinized by 10% trichloroacetie acid and zinc concentration was determined in the protein-free filtrate (Henry et al, 1974).
Ten pasture samples from different locations were analysed for Zn, Cu, Mo, Se, S, P and Ca concentrations (MAFF, 1973). Mineral measurements in both serum and grass were done by atomic absorption spectrophotometry (AAS, Pye Unicam SP 90B).
Monthly records of conception rate (ewes giving birth as a percentage of total flock), lambing rate (lambs born as a percentage of ewes lambing) and all birth weights of lambs in both groups were collected.
The alkaline and highly saline soil of central Sudan produces pastures which are low in Zn (23.2 ± 2.4 ppm) and P (0.08 ± 0.02%), normal in Ca (0.30 ± 0.05%), Mo (1.2 ± 0.2 ppm), S (4.2 ± 0.8 g/kg), and Se (0.1 ± 0.01 ppm) and relatively high in Cu (11.4 ± 2.1 ppm).
The mean serum zinc in Group 2 animals was 8.0 ± 0.6 m mol/litre. Group 1 animals had a value of 10.2 ± 1.2 m mol/litre. The low values of zinc in pasture and serum might be the reason for the appearance of clinical disease in uninjected ewes and lambs.
More animals conceived and lambed in the zinc-dosed than in the control group (Table 1). In Group 1 there was 1 abortion and 4 ewes aborted in Group 2.
The average birth weight of 42 lambs was 3.3 ± 0.9 kg. Group 1 lambs (n - 36) were heavier at 3.4 ± 0.8 kg than Group 2 lambs (n - 6) which weighed 2.9 ± 1.2 kg.
Table 1. Monthly conception and lambing rates (%) in zinc-treated and control groups in Sudan.
|
Trait and treatment |
Month |
||||
|
Jul |
Aug |
Sep |
Oct |
||
|
Conception rate |
|
|
|
|
|
|
|
Overall |
4.0 |
5.1 |
5.2 |
7.5 |
|
|
Zinc-treated |
1.5 |
5.1 |
4.7 |
7.5 |
|
|
Control |
2.5 |
0.0 |
0.5 |
0.0 |
|
Lambing rate |
|
|
|
|
|
|
|
Overall |
100.0 |
111.1 |
125.0 |
127.3 |
|
|
Zinc-treated |
37.5 |
111.1 |
112.5 |
127.3 |
|
|
Control |
62.5 |
0.0 |
12.5 |
0.0 |
This research was financed by the International Foundation for Science. Technical help was provided by John Zakaria.
Ewan R C. 1978. Toxicity and adverse effects of mineral imbalances with emphasis on selenium and other minerals. In: F W Oehme (ed.), Toxicity of heavy metals in the environment. Marcel Dekker, Basel, Switzerland.
Henry R J. Cannon D C and Winkelman J W. 1974. Clinical chemistry, principles and techniques (2nd edition). Harper and Row, New York, USA.
Mahmoud O M, Elsamani F. Bakeit A O and Hassan M A. 1983. Zinc deficiency in Sudan Desert sheep. Journal of Comparative Pathology 93: 591-595.
Mahmoud O M, Bakeit A O and Elsamani F. 1985. Treatment of zinc deficiency by zinc injection. In: Trace element metabolism in man and animals. Commonwealth Agricultural Bureaux, Farnham Royal, UK.
MAFF 1973. The analysis of agricultural materials. Bulletin No. 27. Her Majesty's Stationery Office, London, UK.
Sudan Desert ewes of the Dubasi sub-type on the Nile bank
