REPRODUCTIVE PERFORMANCE OF POLISH LARGE WHITE SOWS IN INTENSIVE PRODUCTION EFFECT OF PARITY AND SEASON

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1 Ann. Anim. Sci., Vol. 9, No. 3 (2009) REPRODUCTIVE PERFORMANCE OF POLISH LARGE WHITE SOWS IN INTENSIVE PRODUCTION EFFECT OF PARITY AND SEASON T o m a s z S c h w a r z, J a c e k N o w i c k i, R y s z a r d T u z Department of Pig Breeding, University of Agriculture, Al. Mickiewicza 24/28, Kraków, Poland Abstract The lifetime reproductive performance of 79 Polish Large White sows, kept at a large commercial farm was analysed according to age, parity and season. Reproductive indices of the sows changed significantly with age, but the direction of these changes depended on the parameter analysed. Conception rate, gestation length, number of stillborn piglets and number of piglets that died before weaning increased over successive parities. The weaning to conception period and the reproductive cycle decreased as sows became older. Total and live born litter size were increasing up to the 5th parity and then decreasing, but the decline of total born litter size was slight and the decrease in liveborn litter size was more rapid and statistically significant. Differences between seasons were smaller and most noticeable in the conception rate. Best results were obtained by sows mated in the autumn and poorest by summer-mated sows. Key words: Large White sows, reproductive performance, parity number, season Polish Large White is one of the two principal maternal pig breeds in Poland. The percentage of Large White sows in the population of Polish purebred pigs is about 38% (Blicharski et al., 2006). Mean reproductive coefficients of pedigree Large White sows in performance-tested farms are: of liveborn piglets, of weaned piglets, 179 days of farrowing interval, 2.04 of farrowing frequency (Blicharski et al., 2006). Changes in reproductive performance according to sow s age and parity number are well known and described, but the physiological aspects and breed influence are not clear. Reproductive coefficients improve until the 3rd parity, because of the increase in ovulation rate and embryo survival, and then remain stable up to the 6th parity (Alsing et al., 1980; Schwarz and Kopyra, 2006). Starting from the 7th parity, the most important reproductive performance parameters such as farrowing rate and litter size begin to fall, but the reasons for this decline remain unknown (Schwarz and Kopyra, 2006; Tantasuparuk et al., 2000; Tummaruk et al., 2000). In addition to age and parity number, two main categories of factors affect the reproductive performance of sows: genetic factors, i.e. potential of the breed including

2 270 T. Schwarz et al. ovulation rate, capacity of the uterus, milk production and maternal responsiveness (Rydhmer et al., 1995), and environmental factors, including climate zone, season, and herd management (Clark and Leman, 1986; Dewey et al., 1995). The European wild boar, the ancestor of modern pig breeds, is a seasonal species with a breeding season occurring in early winter (Mauget, 1982). Some kind of seasonal infertility is observed in domestic pigs too, including a reduced farrowing rate (Love et al., 1993; Peltoniemi et al., 1999 b; Xue et al., 1994), delayed puberty of gilts (Peltoniemi et al., 1999 a; 1999 b), a prolonged weaning to oestrus interval (Peltoniemi et al., 1999 a; Prunier et al., 1996) and reduced litter size during late summer and early autumn (Claus and Weiler, 1985). The climate zone of Poland is characterized by considerable changes in daylength and temperature during the year. That is why the seasonal infertility should be noticeable in Polish pig stocks. Because Polish Large White is the maternal breed, the reproductive performance of sows of this breed should be the most important trait. However, the selection is based on production traits such as growth rate and leanness. The effect of such selection for reproductive performance is indirect, but it is evident that gilts with deeper backfat have much better lifetime reproductive productivity (Gaughan et al., 1995). The liveborn litter size, and the number of weaned piglets are similar in Polish Large White sows and in Polish Landrace sows in performance-tested farms. Similar observations were made also in other countries (Irgang et al., 1994; Tantasuparuk et al., 2000; Tummaruk et al., 2000). However, unreported observations made in practice suggest that Large White sows are more nervous, impatient and aggressive, which is why they require more attention and care from the breeder. Meanwhile, in intensive production systems the time spent on individual care is very short. The mean value of performance-tested farms is 30.4 sows (Blicharski et al., 2006), which indicates a small scale of production. Therefore it is difficult to evaluate if the above reproductive performance could be maintained under intensive conditions of large farms with over 500 sows. The aim of the study was to evaluate lifetime reproductive performance of Polish Large white sows in intensive production according to parity number and season. Material and methods The lifetime reproductive performance of 79 purebred Polish Large White sows was analysed. The animals were kept in a farm of 900 sows and formed a dam-line nucleus herd to produce crossbred gilts. After a 2-month quarantine, all of them were introduced to the foundation herd in four groups during one year. During the second month of quarantine gilts were vaccinated twice against PRV and PRRS, and two weeks after the second vaccination, they were inseminated after heat detection using semen with spermatozoa per dose in 100 ml of MIII solution (Mini Tub, Germany). The lifetime reproductive performance analysed included farrowing rate, litter size (total, liveborn and stillborn), number of piglets that died before weaning, number of weaned piglets, and farrowing interval (including gestation, lactation and weaning to

3 Reproductive performance of Polish Large White sows 271 oestrus period length). Then the same data were analysed for consecutive parities. The maximum number of litters obtained was 14, but the number of sows after 9th parity was small. For this reason the 1st to 8th parities were analysed separately and the 9th to 14th parities were pooled to enable statistical evaluation. The number of females in consecutive parities were: 1 79, 2 58, 3 49, 4 33, 5 28, 6 22, 7 18, 8 12, 9 4, 10 4, 11 2, 12 2, 13 2, Final analysis comprised the same reproductive performance data for the seasons. The treatment factor was the time of sow insemination. The number of sows inseminated by season was 68 in spring, 82 in summer, 88 in autumn and 76 in winter. During statistical analysis differences between age groups (parities), and between seasons were estimated by one-way ANOVA using Duncan s test. Results A total of 314 litters were obtained from 79 sows. The mean farrowing rate was 89.3 ± The mean litter size was ± 3.04, including ± 3.00 of liveborn and 0.91 ± 1.97 of stillborn piglets. The mean number of piglets that died before weaning was 1.06 ± 1.28, but the mean number of weaned piglets was only 8.22 ± The mean farrowing interval was ± 9.9 days, including ± 1.7 days of gestation, 24.0 ± 8.2 days of lactation and 10.2 ± 18.4 days between weaning and oestrus. The reproductive coefficients of the analysed sows in consecutive parities are presented in Table 1. The lowest farrowing rate was in the 2nd and 8th parity, and the highest in parities beyond the 8th parity, where farrowing rate was 100%. Total born litter size increased to the 5th parity and then decreased but slowly and non-significantly. Liveborn litter size increased to the 5th parity too, but later the decrease was more rapid and statistically significant, especially after the 6th parity. This was associated with a rapid increase in the number of stillborn piglets. The highest number of weaned piglets was in parity 2, and the lowest between parities 5 and 7. Farrowing interval decreased together with parity number, especially as a result of the shorter weaning to oestrus period; however, gestation length increased significantly in older sows. The correlation factor between gestation length and number of stillborn piglets was 0.71, and it was statistically highly significant. The reproductive performance of the analysed sows by season is presented in Table 2. The lowest farrowing rate was in summer, and the highest in autumn, with a highly significant difference. The lowest number of total born and liveborn piglets was in sows inseminated in winter, and the highest in sows inseminated in autumn, but the differences were not significant. Meanwhile, the number of weaned piglets was the highest in sows inseminated in winter, and the lowest in sows inseminated in summer, with non-significant differences. The shortest farrowing interval began in autumn, and the longest in spring, but the differences were not significant either.

4 272 T. Schwarz et al. Table 1. Reproductive performance in consecutive parities of Polish Large White sows Item Parity 1 Parity 2 Parity 3 Parity 4 Parity 5 Parity 6 Parity 7 Parity 8 Parity 9 Farrowing rate (%) 88.4 ac ±22.2 Total born litter size including: 10.19Aa ±2.16 live born 9.41A a ±2.46 stillborn 0.78A Ca ±2.46 Number of piglets that died before weaning Number of weaned piglets Farrowing interval including: 0.75Aa ± ab ± a ±24.8 gestation ac ±1.5 lactation 25.4 abd ±9.5 weaning to conception period 14.5a ± c ± Aab ± Aac ± Ab ± Aa ± a ± a ± ab ± b ± a ± abc ± Bc ± Bb ± Aab ± ABab ± ab ± a ± ab ± ac ± ac ± ab ± Bcd ± Bb ± ABad ± ABbc ± ab ± ab ± ac ± c ± acd ± abc ± Bd ± Bb ± ABac ± ABbc ± b ± abc ± abc ± c ± ac ± abc ± Bcd ± Bb ± ACa ± Bc ± b ± bc ± b ± c ± abc ± abc ± Bcd ± ABbc ± BCcd ± Bc ± b ± bc ± ac ± cd ± bc ± ac ± ABcd ± ABac ± BCcd ± ABbc ± ab ± c ± abc ± c ± bd ± b ± Bcd ± ABac ± Bc ± Bc ± ab ± b ± c ± ab ± c ±0.4 abcd values in rows with different letters differ significantly (P 0.05). ABCD as above for P 0.01.

5 Reproductive performance of Polish Large White sows 273 Table 2. Influence of the season on reproductive performance of Polish Large White sows Items Spring Summer Autumn Winter Farrowing rate (%) 94.7±15.4 ABa 86.6±22.6 Ab 97.5±11.6 Ba 92.7±18.2 ABa Total born litter size including: 11.57± ± ± ±3.18 live born 10.84± ± ± ±2.81 stillborn 0.75± ± ± ±1.31 Number of piglets that died before weaning 1.28±1.24a 1.09±1.26 ab 0.95±1.25 b 0.84±1.15b Number of weaned piglets 8.01± ± ± ±3.91 Farrowing interval including: 152.3± ± ± ±22.8 gestation 115.8± ± ± ±1.4 lactation 22.4±8.0 a 25.8±7.8 b 22.7±7.2 a 25.7±7.6 b weaning to conception period 9.3± ± ± ±21.4 ab values in rows with different letters differ significantly (P 0.05). AB as above for P Discussion The study presents the lifetime reproductive performance of a dam-line nucleus herd in a large commercial farm in Poland. The system of evaluation and selection in Poland is based on two parameters: daily gain and lean meat percentage. This system does not include any reproductive coefficients, and it provides for a decline in backfat thickness. This can lead to reproductive problems such as small litter size or delays in return to oestrus after weaning (Beckova et al., 2005; Chen et al., 2003; Kerr and Cameron, 1996; Reese et al., 1984; Young et al., 1991). Other data showed that lean gilts were later to attain reproductive maturity, had lower ovulation rate and, like sows, had poorer lifetime reproductive performance (Gaughan et al., 1995; 1997). Nevertheless, the reproductive performance of Polish Large White sows in performance-tested farms was increasing until However, starting from the year 2003, a slight decrease was observed in the number of piglets born and weaned (Orzechowska and Mucha, 2006). At the same time the growth rate and leanness were still growing (Eckert and Żak, 2006). The second problem with the Polish selection system is a high potential of growth. Especially in large commercial farms, 2nd parity sows often weigh kg and older sows even 400 kg. However, the weight differences between farrowing intervals are very large, which leads to other problems, especially those with milk production during lactation. It is well known that sow s age and parity number affect reproductive performance, but the physiological mechanism remains unknown, especially in older sows (Koketsu and Dial, 1997; Lucia et al., 2002; Van Dijk et al., 2005). In the present study, the poorest results in terms of farrowing rate were achieved by 2nd parity sows. This was probably associated with the second parity syndrome, which is much more noticeable in large herds. The best farrowing rate was achieved by the oldest sows. This does not support an earlier study with Large White Landrace sows on the

6 274 T. Schwarz et al. same farm, where the oldest sows were characterized by the poorest farrowing rate (Schwarz and Kopyra, 2006). The reason for such a difference could be the effect of breed, but in fact the experimental design was different, too. The observations of Schwarz and Kopyra (2006) were short and so only one parity of each sow was analysed. In the present study, each parity of each sow was analysed so the results seem to be more reliable. Total born litter size was increasing up to parity 5. However, there was no difference between the 1st and 2nd parity, a rapid increase was noted between the 2nd and 3rd parity and then the increase was gradual. Starting from the 6th parity the value of this indicator was decreasing, but slowly and not significantly. These results are in agreement with earlier studies (Tantasuparuk et al., 2000; Tummaruk et al., 2000). The most important reproductive coefficient is liveborn litter size. The pattern of differences for liveborn litter size was highly similar to total born litter size up to the 6th parity, but the later decrease was more rapid and significant. It was connected with a rapid rise in the number of stillborn piglets. The increase was so intense that the number of liveborn piglets in parities beyond the 7th parity decreased to the level of parity 1 and 2, nevertheless total born litter size was significantly higher. These results are in agreement with earlier studies of Tantasuparuk et al. (2000) and Schwarz and Kopyra (2006), but the reasons for this phenomenon are still not clear. The correlation between gestation length and number of stillborn piglets was found in the present research like in many earlier studies (Fahmy and Friend, 1981; Schwarz and Kopyra, 2006; Van Dijk et al., 2005), but it is not clear how prolonged gestation influences fetal loss. Meanwhile, gestation length increased with parity number and it was connected with the increasing number of stillborn piglets. The number of piglets that died before weaning increased with increasing parity number. Probably the reason was the large size and weight of sows. Some of the sows more often crush piglets, because they cannot effectively control their body and they are careless when lying down from standing position (Weary et al., 1998). However, crushing is not the only problem during lactation. The number of weaned piglets decreased with parity number, but the value of this coefficient was so low that the number of dead piglets cannot explain it. Large White sows had considerable problems with milk production and MMA syndrome. Over 11% of the analysed lactation periods were completed in the 1st week because of the complete lack of milk, or refusal to feed piglets due to poor maternal responsiveness. That is why mean lactation length is short, and the difference between liveborn litter size and the number of weaned piglets is much larger than the number of piglets which died before weaning. Selection system is not only the problem of gilts and sows in intensive production. Specific conditions in large farms lead to more frequent defects in the development of reproductive organs such as uterine and ovarian infantilism, single-horn uterus, cysts and growths on ovaries in gilts (Szostak and Sarzyńska, 2006). Other researchers observed frustration in sows, which causes increased aggression, displacement activities, immobility, flight or inhibition responses as well as nervousness and stereotypies (Meunier-Salaun and Dantzer, 1990; Nowicki and Klocek, 2004; 2006). Probably this is the second reason why the number of weaned piglets is so low in the present study. The standard procedure in large farms is making substitute mothers for piglets

7 Reproductive performance of Polish Large White sows 275 if their own sow does not want to feed them or produces too little milk to feed all of them. From the 314 analysed lactation periods Large White sows were only used as substitute mothers in 14 (4.45%), compared to 35 (11.15%) that lost all of the piglets in the 1st week. That is why the mean number of weaned piglets is so low among the Polish Large White sows analysed. They seem to be more susceptible to stressful environment than, for example, Landrace sows (Schwarz et al., 2007), but this does not influence their health, farrowing rate or litter size, and only decreases reproductive parameters connected with lactation and maternal responsivness. The last analysis concerned the influence of the season on reproductive performance of Polish Large White sows in a large farm. Seasonal changes in reproductive performance of sows were described in different climates. The primary environmental factors that influence reproductive indicators are photoperiod, temperature, and humidity, but temperature and humidity seem more significant under tropical conditions and photoperiod is the most important in a temperate climate (Love et al., 1993; Prunier et al., 1997; Tantasuparuk et al., 2000). The climate zone of Poland is temperate, with large fluctuations in daylength and temperature among seasons. Natural reproductive activity of domestic pigs, such as wild boars occurs during a short-day period (Mauget, 1982). In the present study the most visible are differences in farrowing rate, with a particularly significant decrease in the summer when the day is long and temperature high. During the summer period, the feed intake in lactating sows is reduced because of high temperature, which affects the loss of body weight (Prunier et al., 1997). The effect is seen as a decreased number of weaned piglets, and subsequent fertility problems. In the present study we observed a decrease in the number of weaned piglets in summer, nevertheless the lactation period was the longest. Farrowing interval in summer was the longest too, especially because of the prolonged weaning to conception period, which was connected with the lowest farrowing rate. All of these data confirm the earlier findings (Peltoniemi et al., 1999 b; Tummaruk et al., 2000). To conclude, the present study demonstrated that sow s age and parity number is the most important factor affecting every reproductive parameter. The effect of season is much weaker, and visible especially in farrowing rate and weaning to conception period length. Under intensive production conditions Polish Large White sows achieved very good reproductive results as regards the coefficients dependent on physiological potential (farrowing rate, born litter size), but the indicators dependent on psychology and behaviour, especially the number of weaned piglets, were rather poor. References A l s i n g I., K r i p p l J., P i r c h n e r F. (1980). Maternal effects on the heritability of litter traits of pigs. Zeitschrift für Tierzuchtung und Züchtungsbiologie, 97, p B e c k o v a R., D a n e k P., V a c l a v k o v a E., R o z k o t M. (2005). Influence of growth rate, backfat thickness and meatiness on reproduction efficiency in Landrace gilts. Czech J. Anim. Sci., 50: B l i c h a r s k i T., H a m e r m e i s t e r A., P t a k J., S n o p k i e w i c z M. (2007). Wyniki użytkowości rozpłodowej loch w roku Trz. Chl., 5:

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