MILK PERFORMANCE OF EWES OF THE IMPROVED VALACHIAN AND TSIGAI BREEDS DURING LAMB SUCKING

Interest in increasing market production of milk is growing in the she ep of the Improved Valachian (IV) and Tsigai (T) breeds. One of the po ssibilities of its increase could be an earlier weaning of lambs at th e age of 25 - 40 days. This method might effectively combine the produ ction of milk-fed lambs (12 - 18 kg) with the higher milk production d uring the milking period. But milk performance (particularly until lam b weaning) has been little important in Slovakia in the last 30 years. This is the reason why the objective of the present paper was to eval uate some indicators of the milk performance of ewes of the Improved V alachian and Tsigai breeds until lamb weaning, determine some genetic and epigenetic factors that influence these indicators, and to analyze the shape of lactation curve of both breeds within this period. Analy sis of covariance was used to assess the milk performance of 37 ewes o f the IV breed and 40 ewes of the T breed until lamb weaning (average age of lambs 64 days). The ewes were housed in the same conditions and received the same dict during the trial (concentrates, alfalfa hay, s ilage or fodder beet, straw). Daily milk production was estimated by a pplication of Mc Cance's method (1959) from an amount of milk produced within approximately 4-hour period. Milk samples were taken from milk releases after the 2nd intravenous administration of oxytocin (5 I.U. ) to determine the contents of dry matter, fat and proteins (Multispec ). Control milk records and ewe weighing took place at regular 14-day intervals. Total milk production over the first 64 days of lactation w as 105.7 1 (s.e. 1.94) in the investigated population, average daily m ilk production 1,6534 ml (s.e. 30.33), protein production 4.48 kg (s.e . 0.078) and fat production 8.06 kg (s.e. 0.207) - Tabs. I and II. The effect of breed on the above indicators was significant (P < 0.05) - dic IV ewes produced 110.0 1, the T ewes 101.6 1. The ewes with twins had the higher milk production than the ewes with single lambs (I 15.7 vs. 103.1 l; P < 0.001 - Tabs. 1). The investigated indicators of pro ductivity were not influenced by the lactation number (Tabs. I - III), but the effect of ewe weight was highly significant (P < 0.001). Fig. 1 shows the linear dependence of total milk production on the average weight of ewes until lamb weaning (r = 0.549; P < 0.01). Cumulative d ata on both investigated years (1992, 1993) and on both breeds are pre sented. Figs. 2 and 3, in which the lactation curve of ewes of the IV and T breeds is plotted for the first 9 weeks of lactation, show that IV ewes have the peak of productivity later (between the 4th and 5th w eek - 2,211.4 ml) dian the T ewes (between the 2nd and 3rd week - 2,06 4.4 ml). Variability of milk production was higher in the IV breed tha n in the T breed (Figs. 2 and 3). The results of the control milk reco rds: milk production 1,575.5 ml (s.e. 27.52), ewe weight 53.74 kg (se. 0.347) and milk production converted per kg of metabolizable weight ( MW) 79.30 ml (s.e. 1.364) - Tabs. III. Tab. III indicates that in spit e of the insignificant difference between the IV and T breeds in ewe w eight, milk production x MW0.75 was considerably higher in the IV ewes (83.44 ml) than in the ewes of the T breed (75.53 ml; P < 0.05). The results indicate relatively high production of milk, dry matter, fat a nd proteins in the first two months of lactation. The data shown by th e shape of lactation curve in the ewes of the IV and T breeds document the need for earlier lamb weaning in these breeds oriented to milk pe rformance, particularly in the ewes of the T breed.