Maataloustieteellinen A ikakauskirja Vo I. 60: 549—552, 1988 Performance of crossbreds of Polish Merino dams with F, rams: Finnsheep x Polish Merino. C. Preliminary results of reproductive performance of ewes M. OSIKOWSKI, B. BORYS and M. A. OSIKOWSKI Institute of Zootechnics, Experiment Station Kotuda Wielka, 88-160 Janikowo, Poland Abstract. The investigations were carried out on the basis of the first three reproductive cycles of ewes born in the same year. The experimental flock consisted of 100 ewes progeny of Polish Merino (PM) dams and F, rams: Finnsheep (F)x PM; there were also 32 purebred PM used as controls. The crossbred ewes, with 25 % of F genotype, had a much better reproduc- tive performance (117 % vs. 96 % in the PM), mainly due to a much higher prolificacy (152.2 vs. 133.6 %) and improved fertility (by 3.1 %) and the percentage of lambs weaned (higher in the crossbreds by 3.4 %). Index words: Finnsheep, Polish Merino, crossbreeding, fertility, prolificacy, stillbirths, weaning-% Introduction The Polish Merino (PM), as well as other sheep breeds and types in Poland, has a rela- tively low prolificacy of about 130 % (3). At present, studies are carried out to improve its prolificacy, both through breeding and selec- tion methods (4) and through commercial crossbreeding with prolific breeds (2, 7). At the same time an attempt was made to develop a wool-prolific line which would produce merinotype wool, through introducing a limit- ed proportion of F genotype to the PM. In the present study, an analysis of reproductive performance of ewes with 25 % F genotype (progeny of PM dams with F, rams F X PM) is presented. Materials and methods The experimental flock consisted initially of 100 crossbred ewes (FxPMxPM), and the control group of 32 purebred PM ewes. The first mating took place in June/July 1985 (reproductive cycle I, at the age of about 18 months); the second one (cycle II) in June/ July 1986, and the third one (cycle III) in February/March 1987. Starting with cycle II both groups of ewes entered the system of 3 matings in 2 years (i.e. every Bth months). 549 JOURNAL OF AGRICULTURAL SCIENCE IN FINLAND The crossbred ewes were mated to meat rams: in cycles I and 11, Polish Blackheaded (PB), Ile de France (IF) and Berrichon du Cher (B), and in the third cycle only to Berri- chon rams. Purebred PM ewes were mated to PM rams. In cycles I and II no selection was carried out, but before the cycle 111 culling was performed, mainly due to infertility, udder diseases and low wool yield. The ewes and their progeny were fed farm-produced feed- stuffs, supplemented by concentrate and mineral mixtures according to the standards of the Institute of Zootechnics (6). Lambs were weaned in cycle I at 100 days, and in cycles II and 111 at 56 days. Body weight of ewes before mating, fertility and prolificacy, percent of stillborn and weaned lambs were recorded and the number of lambs weaned per 100 ewes mated was calculated. The results were analysed by arithmetic means of the above parameters; for ewe body weights statistical significance was variance analysed according to Ruszczyc (8). Results and discussion No differences were observed in body weight of ewes of the tested groups at 18 months, before the first mating (table 1), which indicates that the ewes were in the same stage of development at the moment when they began reproduction. There were, howev- er, considerable differences in ewe body weight before the second and third mating; in both cases the crossbreds were heavier by 6.9 and 8.7 Vo, respectively (P<0.01). Further research is needed to explain these differences, but taking into account the better reproduc- tive performance of the crossbreds (higher percentage of lambs weaned) it can be sup- posed that their vitality and feed conversion were better than of the purebred PM. In all the three reproductive cycles taken to- gether, the crossbred ewes performed better on the average by 3.1 Vo. There was, how- ever, much variation between the cycles: in cy- cles I and II the crossbreds had a better per- formance by 2.6 and 11.2 Vo respectively, while in cycle II it was the purebred PM which had 4.5 Vo higher reproductive performance. The effect of 25 Vo F genotype on prolifica- cy was positive. The crossbreds were more prolific than the purebreds in all three reproductive cycles (on the average by 22.6 Vo). It should be noted, however, that while in the cycles I and II the difference was not very con- siderable (16.5 and 15.6 Vo respectively), in cy- cle 111 the crossbreds were superior to purebreds by 35.6 Vo. On the whole the results seem to confirm the assumption that this sys- tem of crossbreeding with the F would in- crease ewe prolificacy by 20—25 Vo in com- parison to purebreds. i.e. less than half of the superiority achieved when PM ewes are mat- ed directly to F rams (7). This is confirmed by authors from other countries who com- pared the effect of different percentage of F genotype on prolificacy of crossbred ewes (1, 5). The considerable differences in fertility and prolificacy observed between the tested groups in the 3rd cycle (mating February/March) may indicate that reproductive ability of the cross- breds is less seasonal than that of purebred PM. Mating of the crossbred ewes to meat rams caused large diversity in their fertility and prolificacy in the three reproductive cycles (ta- ble 1). It is, however, difficult to draw con- clusions about any clear influence of the meat breeds on reproductive traits of ewes from the results obtained from the three cycles. The differences in percent of stillborn lambs do not indicate any significant effect of cross- breeding with F. In both genetic groups this percentage was much higher in cycle 111, which could have been caused by shortening the »open» period from 7 months (between cycles I and II) to 3 months (between cycles II and III), due to the introduction of the system of three matings in two years. The percentage of lambs weaned in cycles I and II was similar in both groups, while the results of cycle 111 were significantly affected by a series of sudden lamb deaths caused by a bacterial infection of the respiratory and digestive tract. On the whole the differences 550 551 Table 1. Reproductive performance of FxPMxPM ewes in comparison to purebred PM ewes. Trail Ewe breed FxPMxPM PM Ram breed PB IF B PB+IF+B PM Reprod.cycle Total No. of ewes I 36 29 35 100 32 II 27 27 28 82 25 111 65 65 23 Body weight 1 49,1 51,5 50,6 50,3 50,6 before mating II 56,9 57,2 57,6 57,3A 53,6 B (kg) 111 53,9 53,9A 49,6» I 88,9 96,6 94,3 93,0 90,6 Fertility (%) II 96,2 88,9 89,3 91,5 96,0 111 93,8 93,8 82,6 Average I, II i 111 92,5 92,7 92,5 92,8 89,7 Prolificacy (%) 1 150,0 153,6 130,3 144,1 127,6 II 161,0 141,7 168,0 157,3 141,7 111 167,2 167,2 131,6 Average 1, II i 111 155,7 147,6 155,2 156,2 133,6 % of stillborn 1 4,2 2,3 0,0 2,2 0,0 lambs II 4,8 0,0 0,0 1,7 0,0 111 6,9 6,9 8,0 Average I, II i 111 4,5 1,1 2,3 3,6 2,7 % of lambs 1 91,3 78,6 88,4 86,3 83,8 weaned 1 11 85,0 91,2 80,9 85,3 88,2 111 80,0 80,0 69,6 Average 1, II i 111 88,1 84,9 83,1 83,9 80,5 No. of lambs I 117 114 109 113 97 weaned per 100 II 126 115 121 121 120 ewes mated 1 111 117 117 70 Average 1, II i 111 121 114 116 117 96 1 lambs were weaned in the first cycle after 100 days and in the second and third cycle after 56 days. in the percentage of lambs weaned can be dis- reproductive index of the crossbred ewes, regarded. The reproductive index of the crossbred Conclusion ewes was much better than that of the purebreds in cycles I and 111 (by 16 and 47 °?o The analysis of reproductive traits of respectively), while in cycle II the two groups FxPM x PM ewes has shown that crossbreds of ewes had nearly the same index values. The with 25 % F genotype have a better reproduc- mean superiority of the crossbred ewes in all tive performance than purebred PM (by 21 % three reproductive cycles was 21 %. on average), which is mainly due to higher There was no effect of mating to rams of prolificacy (by 22.6 %) together with slightly different meat breeds on the percentage of improved fertility (by 3.1 %) and lamb wean- stillborn and weaned lambs and on the ing rate (by 3.4 °/o). References 1. Drozdz, A., 1988. Owezarstwo 1, 5 —7. 2. Gut, A., Kozal, E. & Grajczak, L. 1986. Zeszyty Problemowe Postepow Nauk Rolniczych, z. 303, 39—45. 3. Kierubinska, Z. 1987. Owezarstwo 9, 3—B. 4. Krupinski, J. & Rzepecki, R. 1987. Prace hodowlane Instytutu Zootechniki i ich wplyw na rozvvöj owczarst- wa krajowego. Materialy konferencyjne Gdansk, pazdziernik, 28—29. 5. Maijala, K. 1979. Experiences of Finnsheep and its crosses as dams for fat lambs. Symp. Intensive Sheep Prod., Helsinki, 2—9. 6. Normy zywienia zwierzat gospodarskich, 1982. PWRiL Warszawa. 7. Osikowski, B. & Borys, B. 1986. Hodowla- ny 6, B—l3. 8. Ruszczyc, Z. 1978. Metodyka doswiadczen zootech- nicznych, PWRiL Warszawa. 552