Reproductive performance of purebred landrace and Yorkshire sows in Thailand with special reference to seasonal influence and parity number

The purpose of this study was to analyze reproductive performance in purebred Landrace and Yorkshire sows with special reference to seasonal influence and parity number, under tropical conditions where day length is almost constant throughout the year. Data from three purebred sow herds in Thailand during the period from 1993 to 1996 were analyzed. The two breeds were present in all three herds. The analysis comprised records of 3848 Landrace sow litters and 2033 Yorkshire sow litters. The statistical models included the fixed effects of month, year, parity, breed of the sow, herd, and two-way interactions of breed-parity, breed-herd, breed-month, breed-year, parity-month, month-herd, year-herd and month-year. The random effect of sow within breed was included in all models. Analysis of covariance was performed to analyze the effect of temperature, humidity and heat index on number of total born per litter (NTB), weaning to first service interval (WSI) and farrowing rate (FR). Landrace sows had significantly higher NTB (0.6 piglets), number of live born per litter (0.5 piglets), and average birth weight (0.13 kg) than Yorkshire sows (P<0.001). Farrowing rate was 3.9% higher in Landrace sows than in Yorkshire sows (P<0.01). However, Yorkshire sows had significantly shorter WSI (P<0.001) and significantly higher proportion of sows served within 7 days after weaning (P<0.01) than Landrace sows. No breed differences were found in number of stillborn per litter and weaning to conception interval. Parity had significant effect on all reproductive parameters analyzed. Number of total born and live born per litter was significantly lower for sows farrowing during the rainy season than in other seasons. Farrowing rate was low for sows mated during the hot and rainy season. Weaning to service interval and WSI7 were prolonged for sows weaned during the hot and rainy season. Reproductive performance was significantly unfavorably influenced by elevated temperature and heat index after mating (NTB and FR) or during lactation (WSI).     

Relationships between ovulation rate and litter size in purebred Landrace and Yorkshire gilts

The aim of the present study was to investigate the ovulation rate and its relationship to number of total piglets born in purebred gilts under tropical climatic conditions. This study was conducted in two swine breeding herds (A and B) in the northeastern part of Thailand. The sources of swine genetic material originate from West Europe. Gilts were mated (AI) on the second or later observed estrus at a body weight of at least 130 kg. In most cases, they were mated at third estrus. One hundred and twenty-seven gilts, 24 Landrace and 24 Yorkshire from herd A, and 42 Landrace and 37 Yorkshire from herd B were used. Gilts were examined once by laparoscopy under general anesthesia between days 8 and 15 after mating. The ovaries were examined and the pathological findings were recorded. The number of corpora lutea was counted, and was assumed to equal the ovulation rate. Subsequent mating results and farrowing data were recorded. The data were analyzed with analysis of variance. Single or double unilateral cysts and par-ovarian cysts did not affect mating results. Landrace gilts were significantly younger at first mating than Yorkshire gilts (244 versus 249 days, P < 0.05). At first mating, Yorkshire gilts had a significantly higher ovulation rate compared to Landrace gilts (15.3 versus 13.8, P < 0.001). There was no difference in the number of total piglets born per litter between the two breeds, but the total prenatal loss from ovulation to farrowing was significantly higher in Yorkshire than in Landrace gilts. Both the low ovulation rate and the high prenatal loss contribute to the low litter size in gilts raised under tropical climatic conditions.     

Some Factors Influencing the Losses of Pigs Prior to Weaning

Analyses of the records of 244 litters of purebred Yorkshire, Landrace, the crosses, backcrosses and crisscrosses of these two breeds were carried out to evaluate some of the factors influencing the losses of piglets prior to weaning. There were differences in percentage survival between mating systems, with crossbred Landrace x Yorkshire piglets showing the highest rate of survival.A direct relationship existed between the duration of farrowing and the incidence of stillbirths. The incidence of stillbirths was higher for male piglets than for female piglets.Litter size at birth and weight loss of sow from parturition to weaning were important factors in determining litter size at weaning. Litter size at birth however, exerted a more important influence on litter performance than weight loss. Age of sow had no significant effect on the number of piglets alive at weaning and implied that gilts were apparently as good mothers as sows. From computed least squares estimates, it was implied that in general, piglets of low birthweights had much less chance of survival than those born with heavier weights.     

Impact of Mated Female Nonproductive Days in Breeding Herd after Porcine Epidemic Diarrhea Virus Outbreak

Porcine epidemic diarrhea virus (PEDV) is an important pathogen that has a significant economic impact on the swine industry by imposing a high rate of mortality in suckling piglets. However, limited information on the productivity values of gilts and sows infected with PEDV is available. Here, we evaluate the productivity index in gilts and sows during the 1-year period before (19 January 2013 to 18 January 2014) and after (19 January 2014 to 18 January 2015) a PEDV outbreak from a 2000-sow breeding herd in Taiwan. The farrowing rate (FR), return rate (RR), total pigs born per litter (TB), pigs born alive per litter (BA), weaning pigs per litter (WPL), pre-weaning mortality, percentage of sows mated by 7 days after weaning, weaning to first service interval (WFSI), mated female nonproductive days (NPDs), replacement rate of sows and sow culling rate were compared using productive records. The FR (-9.6%), RR (+9.8%), TB (-1.6), BA (-1.1), WPL (-1.1), sows mated by 7 days after weaning (-6.9%), WFSI (+0.8 days), NPDs (+6.9 days) and sow culling rate (+7.2%) were significantly different between the 1-year pre-PEDV outbreak period and the post-PEDV outbreak period. Impacts of the PEDV infection on the reproductive performance were more severe in pregnant gilts than in sows. In conclusion, these findings indicate that the outbreak of PEDV caused an increase in the rate of NPDs in breeding herds.     

Effect of birth litter size, birth parity number, growth rate, backfat thickness and age at first mating of gilts on their reproductive performance as sows

The present study was performed to evaluate retrospectively the influence of birth litter size, birth parity number, performance test parameters (growth rate from birth to 100kg body weight and backfat thickness at 100kg body weight) and age at first mating (AFM) of gilts on their reproductive performance as sows. Traits analysed included remating rate in gilts (RRG), litter size, weaning-to-first-service interval (WSI), remating rate in sows and farrowing rate (FR). Data were collected from 11 Swedish Landrace (L) and 8 Swedish Yorkshire (Y) nucleus herds and included 20712 farrowing records from sow parities 1-5. Sows that farrowed for the first time during 1993-1997, having complete records of performance test and AFM, were followed up to investigate their subsequent reproductive performance until their last farrowing in 1999. Analysis of variance and multiple regression were applied to continuous data. Logistic regression was applied to categorical data. The analyses were based on the same animals and the records were split into six groups of females, i.e. gilts, primiparous sows, and sows in parities 2-5, respectively. Each additional piglet in the litter in which the gilt was born was associated with an increase of her own litter size of between 0.07 and 0.1 piglets per litter (P<0.001). Gilts born from sow parity 1 had a longer WSI as primiparous sows compared with gilts born from sow parity 4 (0.3 days; P<0.05) or parity 5 (0.4 days; P<0.01). Gilts with a higher growth rate of up to 100kg body weight had a larger litter size (all parities 1-5; P<0.05), shorter WSI (all parities 1-5; P<0.05) and higher FR (parities 2 and 5; P<0.05) than gilts with a lower growth rate. Gilts with a high backfat thickness at 100kg body weight had a shorter WSI as primiparous sows (P<0.001) compared with low backfat gilts, and 0.1 piglets per litter more as second parity sows (P<0.01). A 10 day increase in AFM resulted in an increase in litter size of about 0.1 piglet for primiparous sows (P<0.001) and a decrease (P<0.05) for sow parities 4 and 5.     

Repeat breeding and subsequent reproductive performance in Swedish Landrace and Swedish Yorkshire sows

The objective of the present study was to analyse the association between repeat breeding (RB) in gilts/sows and their subsequent reproductive performance as well as the impact of interactions between repeat breeding and factors like parity number, boar breed, season and mating type (MT) on subsequent reproductive performance in Swedish Landrace (L) and Swedish Yorkshire (Y) sows. Data analysed included 7040 sows (3654 L and 3386 Y), farrowing during January 1994 until December 1999 in 11 L and 8 Y nucleus herds. The study was assigned as a cohort design and the aim was to study gilts/sows from their first mating as gilts until mating after third parity. Analysis of variance was applied to continuous data and logistic regression was applied to categorical data. Percentages of litters as a result of repeat breeding in sow parities 1-3 were 6.1, 12.0 and 6.3% for L sows and 6.7, 13.1 and 7.4% for Y sows. For parity 3, the incidence of litters resulting from repeat breeding was significantly higher (P<0.001) in Y than in L sows. The proportion of irregular return to oestrus (>24 days after first mating) was higher (P<0.01) in primiparous sows than in multiparous sows (69% versus 61%). On average, litters resulting from repeat breeding were larger (P<0.001) than litters resulting from non-repeat breeding (NR) (about 0.5 piglets per litter) in both L and Y sows. For Y sows, if the previous litter was a result of repeat breeding, the subsequent reproductive cycle had 2.7% higher RR (P<0.05) and 2.4% lower FR (N.S.) compared with sows that were not repeat bred. The same trend was found in L sows (1.4% higher RR and 1.3% lower FR) but the differences were not significant. Among the sows removed from the herds, about 24% of L and 28% of Y were culled due to reproductive problems (gilts not included). In addition, a number of sows from these nucleus herds were also culled due to low breeding value and poor conformation.     

Body weight loss during lactation and its influence on weaning-to-service interval and ovulation rate in Landrace and Yorkshire sows in the tropical environment of Thailand

The aim of this study was to investigate the ovulation rate and the weaning-to-service interval (WSI) of sows in relation to their body weight loss during lactation in tropical climatic conditions. Effect of lactation length (LL), number of total born piglets, number of live born piglets, litter birth weight, average piglet birth weight, number of pigs weaned, litter weaning weight and average pig weaned weight on sow weight loss during lactation were also studied. This study was conducted in two commercial purebred sow herds (A, B) in the central part of Thailand from August to December 1997. The herds had both Landrace (L) and Yorkshire (Y) sows. The 123 sows (55 L and 68 Y) in herd A and 153 sows (95 L and 58 Y) in herd B, parity 1-4, were weighed within 4 days after farrowing and at weaning. Lactation length, litter size at birth and at weaning, litter weight at birth and at weaning, and WSI were recorded for each of these sows. In herd A, 52 sows (20 L and 32 Y) were examined once by laparoscopy between days 8 and 14 after AI-service. These sows had farrowed at least seven piglets in the previous parturition. The numbers of corpora lutea (CL) in both ovaries were counted, and were assumed to equal the ovulation rate. L-sows had significantly (P < 0.05) higher relative weight loss during lactation (RWL) than Y-sows. The RWL increased by 0.7% for each extra pig weaned. When LL increased by 1 day, within the interval of 17-34 days, RWL decreased by 0.6%. Sows with a high weight loss had significantly (P < 0.05) longer WSI than sows with medium or low weight loss. Weight loss had a significant (P < 0.05) effect on WSI in parity 1 and 2 sows. Y-sows had more CL than L-sows (15.7 versus 14.0) (P < 0.05). RWL, parity and regression on lactation length had no significant effect on number of CL. In conclusion, sows with higher number of pigs weaned lose more weight. Under the restricted feeding regime applied, high weight loss during lactation prolongs WSI in parity 1 and 2 sows, but has no influence on the ovulation rate at first oestrus after weaning. The ovulation rate is higher in Yorkshire than in Landrace sows. The ovulation rate is independent of parity.     

Sow level risk factors for early piglet mortality and crushing in organic outdoor production

Piglet mortality is a major problem in organic pig production affecting both farm economy and animal welfare. Knowledge is scarce on the risk factors of piglet mortality in Danish commercial organic pig production. The objectives of this study were to evaluate season, litter size, parity, sow body condition and stillborn littermates as risk factors for early piglet mortality and crushing of liveborn piglets from parturition until castration at day 3 to 5 postpartum (pp). The study was conducted over a 1-year period in nine commercial Danish organic pig herds practicing outdoor farrowing all year round. Data included recordings on 3393 farrowings with 50 284 liveborn piglets of which 14.8% died before castration. A subset of the dead piglets were collected and necropsied to identify crushed piglets. The average number of liveborn piglets per litter was 14.8 (SD=3.7) and the average time from parturition until castration was 4.1 (SD=1.7) days. A negative binomial regression analysis was used to model the effect of the predictive variables on the early piglet mortality accounting for different time periods from parturition to castration. An increase in maternal body condition score (BCS) and parity significantly increased the risk of dying between parturition and castration. Early mortality was found to be lowest during spring (March to May) and highest during summer (June to August). Being born into a litter with one or more stillborn littermates increased the risk of early mortality. The risk factors for crushing of piglets were evaluated using a logistic analysis. A significant effect of parity and litter size was found where the odds of at least one piglet in a litter with mortality was diagnosed as crushed increased with increasing parity and litter size. In conclusion, being born during summer (June to August), high parity and maternal BCS and stillborn littermates were found to be risk factors for piglet mortality between parturition and castration. In addition, parity and increasing litter size were found to be risk factors for crushing of piglets in litters with mortality.     

Age at puberty, ovulation rate, uterine length, prenatal survival and litter size in Chinese Meishan and Yorkshire females

Studies on the ovulation rate, prenatal survival and litter size of Chinese Meishan pigs have given widely divergent results depending on the extent of inbreeding of the animals, their original genetic diversity, the age and parity, and the conditions of management. To obtain meaningful results, it is necessary to characterize the population under study. The following report characterizes populations of Meishan and Yorkshire of a widely diverse background. First farrowing data were collected on 21 Meishan and 20 Yorkshire gilts. Meishan gilts had 12.4 fully formed piglets and Yorkshire gilts had 7.4 fully formed piglets (P < 0.01). Meishan gilts averaged 1.86 mummified fetuses per litter vs 0.05 per Yorkshire litter (P < 0.01). Yorkshire piglets averaged 1.3 kg body weight at birth vs 0.9 kg for Meishan piglets (P < 0.01). At 47 days of second gestation, 19 Meishan and 12 Yorkshire sows averaged 22.7 and 16.3 corpora lutea (CL), respectively (P < 0.01). Uterine length and number of fetuses were not different (P > 0.40) in the two breeds. Daily estrous detection of 50 Meishan and 34 Yorkshire gilts began at 60 and 120 days of age, respectively. Meishan gilts reached sexual maturity at 95 days of age, which was 105 days earlier than Yorkshire gilts (P < 0.01). Meishan gilts were in estrus nearly 1 day longer than Yorkshire gilts at first, second and third estrus (P < 0.05). No differences in cycle length between breeds were detected for the first or second estrous cycle (P > 0.60). Nineteen Meishan gilts were slaughtered at 51 days of gestation and their reproductive tracts were recovered. The mean number of dissected CL (17.0), number of fetuses (13.1), total uterine length (396 cm), spacing per fetus (29.9 cm), allantoic (124.9 ml) and amniotic (32.2 ml) volumes, crown-rump length (82.8 mm), weight (35.4 g), sex, and direction of each fetus were determined. Chinese Meishan gilts reached puberty much earlier and were in estrus longer than Yorkshire gilts and Meishan sows had more CL than Yorkshire sows.     

Genetic parameters for haemoglobin levels in sows and piglets as well as sow reproductive performance and piglet survival

Genetic parameters were estimated for haemoglobin (Hb) levels in sows and piglets as well as sow reproductive performance and piglet survival. Reproductive traits were available between 2005 and 2014 for 7857 litters from 1029 Large White and 858 Landrace sows. In 2012 and 2013, Hb levels, sow BW and sow back fat depth were measured on 348 sows with 529 litters 5 days prior to farrowing. In addition, Hb levels were available for 1127 one-day-old piglets from 383 litters (a maximum of three piglets per litter) of 277 sows with Hb levels. The average Hb levels in sows (sow Hb), their litters (litter Hb, based on average Hb of three piglets) and individual piglets (piglet Hb) were 112 ± 12.6 g/l, 103 ± 15.3 g/l and 105 ± 21.7 g/l, respectively. Heritabilities for Hb levels were 0.09 ± 0.07 for sow Hb, 0.19 ± 0.11 for litter Hb and 0.08 ± 0.05 for piglet Hb. Estimates for the permanent environment effect of sows were 0.09 ± 0.09 for sow Hb, 0.11 ± 0.12 for litter Hb and 0.12 ± 0.03 for piglet Hb. In comparison, heritabilities for both number of stillborn piglets and pre-weaning survival were lower (0.05 ± 0.01 and 0.04 ± 0.01). Sow BW had no significant heritability, while sow back fat depth was lowly heritable (0.10 ± 0.08). Positive genetic correlations were found between sow Hb and litter Hb (0.64 ± 0.47) and between litter Hb and sow back fat depth (0.71 ± 0.53). Higher litter Hb was genetically associated with lower number of stillborn piglets (−0.78 ± 0.35) and higher pre-weaning survival (0.28 ± 0.33). Negative genetic correlations between sow Hb and average piglet birth weight of the litter (−0.60 ± 0.34) and between piglet Hb and birth weight of individual piglets (−0.37 ± 0.32) indicate that selection for heavier piglets may reduce Hb levels in sows and piglets. Similarly, selection for larger litter size will reduce average piglet birth weight (r_g: −0.40 ± 0.12) and pre-weaning survival (−0.57 ± 0.13) and may lead to lower litter Hb (−0.48 ± 0.27). This study shows promising first results for the use of Hb levels as a selection criterion in pig breeding programs, and selection for higher Hb levels may improve piglet survival and limit further reduction in Hb levels in sows and piglets due to selection for larger and heavier litters.     

An association analysis of sow parity,live-weight and back-fat depth as indicators of sow productivity

Understanding how critical sow live-weight and back-fat depth during gestation are in ensuring optimum sow productivity is important. The objective of this study was to quantify the association between sow parity, live-weight and back-fat depth during gestation with subsequent sow reproductive performance. Records of 1058 sows and 13 827 piglets from 10 trials on two research farms between the years 2005 and 2015 were analysed. Sows ranged from parity 1 to 6 with the number of sows per parity distributed as follows: 232, 277, 180, 131, 132 and 106, respectively. Variables that were analysed included total born (TB), born alive (BA), piglet birth weight (BtWT), pre-weaning mortality (PWM), piglet wean weight (WnWT), number of piglets weaned (Wn), wean to service interval (WSI), piglets born alive in subsequent farrowing and sow lactation feed intake. Calculated variables included the within-litter CV in birth weight (LtV), pre-weaning growth rate per litter (PWG), total litter gain (TLG), lactation efficiency and litter size reared after cross-fostering. Data were analysed using linear mixed models accounting for covariance among records. Third and fourth parity sows had more (P<0.05) TB, BA and heavier BtWT compared with gilts and parity 6 sow contemporaries. Parities 2 and 3 sows weaned more (P<0.05) piglets than older sows. These piglets had heavier (P<0.05) birth weights than those from gilt litters. LtV and PWM were greater (P<0.01) in litters born to parity 5 sows than those born to younger sows. Sow live-weight and back-fat depth at service, days 25 and 50 of gestation were not associated with TB, BA, BtWT, LtV, PWG, WnWT or lactation efficiency (P>0.05). Heavier sow live-weight throughout gestation was associated with an increase in PWM (P<0.01) and reduced Wn and lactation feed intake (P<0.05). Deeper back-fat in late gestation was associated with fewer (P<0.05) BA but heavier (P<0.05) BtWT, whereas deeper back-fat depth throughout gestation was associated with reduced (P<0.01) lactation feed intake. Sow back-fat depth was not associated with LtV, PWG, TLG, WSI or piglets born alive in subsequent farrowing (P>0.05). In conclusion, this study showed that sow parity, live-weight and back-fat depth can be used as indicators of reproductive performance. In addition, this study also provides validation for future development of a benchmarking tool to monitor and improve the productivity of modern sow herd.     

Sow-level risk factors for stillbirth of piglets in organic sow herds

In Danish organic pig production, one-third of total born piglets die before weaning, and stillbirth has previously crudely been estimated to account for 27% of the total preweaning mortality. The objective of this study was to evaluate season, litter size, parity and body condition of the sow as risk factors for stillbirth in nine commercial Danish organic pig herds. The study was conducted over a 1-year period, and the data included registrations on 5170 farrowings with 82 906 total born piglets. The average number of total born piglets per litter was 16.0, and the number of stillborn piglets per litter was 1.1. A significant effect of season was seen with an odds ratio for stillbirth of 1.15 during summer (May to August) compared with the remaining part of the year. A non-linear effect of litter size was seen where an increase in litter size from 11 to 16 resulted in an odds ratio of stillbirth of 1.11. An increase in litter size from 16 to 21 resulted in an odds ratio of stillbirth of 1.45. A significant interaction between body condition and parity was present. In first parity sows, an increase in body condition score from 2 (thin) to 3 (moderate) and from 3 to 4 (fat) increased the probability of stillbirth with an odds ratio of 1.23 and 1.36, respectively. In sows with parity above 4, an increase in body condition score from 2 to 3 and from 3 to 4 decreases the probability of stillbirth with an odds ratio of 0.68 and 0.79, respectively. In conclusion, increasing litter size and being born during the summer months of May to August were found to be risk factors for stillbirth. Furthermore, an interaction between body condition and parity showed that thin sows with parity above 4 had a substantially increased risk of stillbirth compared with normal and fat sows with parity above 4. In contrast, for parity 1 sows risk of stillbirth was increased in fat sows.     

Effects of lactation length and weaning-to-service interval on subsequent farrowing rate and litter size in Landrace and Yorkshire sows in Thailand

The aim of the present study was to investigate the influence of lactation length (LL) on weaning-to-service interval (WSI), and the effect of LL and WSI on the subsequent farrowing rate and litter size among purebred Landrace and Yorkshire sows under tropical conditions. The variation in litter weight at weaning (LWW) was also studied. Data were analyzed from three purebred sow herds located in the central part of Thailand, including sows weaned during the period from January 1993 to December 1996. Data were analyzed with analysis of variance using SAS software. The procedure MIXED was used for analysis of the continuous outcome variables (namely LL, LWW, WSI, number of total born and number of live born piglets). The GLIMMIX macro was used for analysis of the categorical outcome variable, farrowing rate (FR). In the statistical analyses, WSI was grouped into 7 groups, when it was an independent variable, as follows: 1 to 4, 5, 6, 7, 8, 9, to 10, and 11 to 21 days. Lactation length was grouped into 4 groups as follows: 17 to 24, 25 to 27, 28 to 30 and 31 to 35 days. Parities were grouped into 4 groups as follows: 1, 2, 3 + 4, and 5 to 8. Landrace sows had significantly higher LWW (P < 0.001) compared with Yorkshire sows (56.1 vs. 53.6 kg). The LL was significantly (P < 0.05) shorter during the cool season than during the other seasons while no difference was found in LWW between the hot and the cool season. The LL had no effect on WSI, FR and litter sizes. The FR was significantly lower when the WSI was 7 to 10 days than when the WSI was 1 to 6 days. An increase in WSI between Days 9 to 10 and Day 21 resulted in a significant increase in FR. Subsequent litter size decreased by about 0.5 piglets when the WSI increased from 1 to 5 days to 6 to 7 days. Thereafter, litter size increased as the WSI increased from 9 to 10 days to 21 days.     

A model for economic comparison of swine insemination programs

Optimal artificial insemination schedules are those that result in a high farrowing rate and litter size, while minimizing costs of semen and labor by avoiding unnecessary inseminations. A simulation model programmed in a commercial spreadsheet was developed to permit comparison of alternative schedules. Farrowing rate and litter size for a particular schedule were dependent on the timing of insemination relative to the time of ovulation. Economic return was calculated by multiplying the number of pigs born per bred sow by $33.00 and subtracting the cost of producing a litter of pigs and raising them to weaning ($222.88 per sow plus $2.44 per pig born) and the cost of detection of estrus and breeding. Seven insemination schedules combined with once versus twice per day detection of estrus were simulated in 500 herds of 100 sows each. Inseminations were simulated to occur on schedules of: 1) 0, 12, 24 and 36 h; 2) 12, 24 and 36 h; 3) 0 and 24 h; 4) 12 and 36 h; 5) 12 h; 6) 24 h; and 7) 36 h after first detection of estrus. Schedule 1 was predicted to yield the highest farrowing rate and litter size. Economic return was highest for Schedule 2 with twice per day detection of estrus followed closely by Schedule 1 with once per day detection of estrus at $14.90 and $13.75 per bred sow, respectively. High performance was dependent on insuring that inseminations occurred at an optimum time in as great a proportion of sows as possible.     

Herd-level factors associated with piglet weight at weaning,kilograms of piglets weaned per sow per year and sow feed conversion

To understand the production factors that affect conclusive parameters of sow herd performance can improve the use of the resources and profitability of farm. The objective of this study was to identify associations and quantify the effects of a set of factors related to piglet weight at weaning (PWW), kilograms of piglets weaned per sow per year (kgPWSY) and sow feed conversion (SFC). Data from 150 farms were collected, for a total study population of 135 168 sows, including gilt replacement, breeding (mating), gestation and farrowing/lactation phases. A questionnaire focusing on reproductive performance, management, facilities, feeding, health and biosafety was administered. Multiple linear regression models were used to assess associations among factors with each of the three dependent variables. Increased duration of lactation was positively associated with PWW, kgPWSY and SFC. The increase in the number of live born pigs per litter was positively associated with kgPWSY and with SFC. Farms with higher PWW had farrowing room humidifiers, did not surgically castrate male piglets and used quaternary ammonia compounds for farrowing room disinfection. Farms with higher kgPWSY used lined ceilings in farrowing rooms and winter feeds with higher CP percentages in gestation; they also had more farrowings per sow per year. Sow feed conversion was worse in farms with partly slatted floors during gestation, in farms feeding lactating sows six times a day or ad libitum and farms with a higher sow-handler ratio. This study indicates that farms can increase PWW and kgPWSY and improve the SFC by changing one or more management, biosafety and feeding practices or facilities as well as by focusing on improving several performance parameters, particularly increasing the duration of lactation and the number of live born pigs per litter.     

Epidemiological Studies of Piglet Diarrhoea in Intensively Managed Danish Sow Herds

The study comprised 70,796 litters in 104 sow herds, observed from 1976 through 1982. Weaning age decreased from approx. 42 days to approx. 30 days during the observation period. Diseases and symptoms were recorded together with production parameters (feeding, barn construction, economic returns etc.). The mean incidence rate of pre-weaning diarrhoea was 6.8 % of litters, with considerable inter-herd differences (incidence rates from 0 to approx. 50%). There was a slight increase in incidence during the autumn (August through October). Incidence rates increased with litter size, with a peak incidence in litters of 11–13 piglets, and decreased with increasing parity of the sow. There was a positive association between occurrence of arthritis and pre-weaning diarrhoea in the litters, and litters from sows with post parturient disease (MMA complex) had 1.8 times higher risk of getting diarrhoea than litters from healthy sows. No important differences among breeds were found. Small herds (< 200 farrowings per year) had higher incidence rates than large herds (400–499 farrowings per year). Herds with a gilt proportion above 30 % had an incidence rate of 12.3 %, i. e. nearly twice as high as the overall mean (6.8 %). There was a trend towards a higher incidence rate in litters kept in traditional pens (i. e. large pens with solid floor and loose sows) than in intensive pens (i. e. small pens with slatted flooring and tethered sows). The overall pre-weaning mortality rate was 16.2 % of pigs born, half of which was due to stillbirths (6.3 %) and overlaid piglets (2.2 %). In litters with pre-weaning diarrhoea, the mortality rate was 19 %, compared to 13 % in litters without occurrence of diarrhoea. This difference accounts for an excess loss of 0.6 piglets from birth to weaning in diarrhoeic vs. non-diarrhoeic litters. Piglets from litters with pre-weaning diarrhoea had reduced weight gain. Thus, on the average, they were 2.2 days older at 25 kg bodyweight and weighed 0.4 kg less at 30 days than piglets from non-diarrhoeic litters. Also, litters with pre-weaning diarrhoea had a significantly increased risk of post-weaning diarrhoea. The present information forms a basis for defining acceptable disease thresholds in suckling litters in intensively managed herds.     

Effectiveness of frozen boar semen under practical conditions of artificial insemination

A technique of boar semen deep-freezing and frozen semen use was tested in practice. 338 sows and 43 gilts belonging to small herds with less than 10 females each were inseminated without oestrus detection by a teaser boar. About 58 % of the inseminated females produced 9.3 piglets per litter. But there were differences between parities. The sows had the highest fertility rate, whereas the gilts showed a significantly lower farrowing rate (59.8% vs 41.9%; P < 0.05). The standing reaction of the female to the back pressure test made by the inseminator and the behaviour of the female during insemination had an effect on the farrowing rate. The best result was obtained after a standing reaction and a behaviour score of 1 (64.5% and 9.6 piglets for farrowing rate and litters size respectively). Farrowing rate for inseminators ranged from 44.3% to 62.4% among inseminators. Farrowing rate for females inseminated with frozen semen from Large-White, Landrace, Pietrain boars was not different, but there were significant differences between the boars. Results showed that insemination with deep-frozen boar semen could be used under practical conditions as an additional technique to the use of fresh semen.     

Allelic variation in the erythropoietin receptor gene is associated with uterine capacity and litter size in swine

A single nucleotide polymorphism (SNP; C vs. T) that creates an extra GATA-1 site (T allele) in intron 4 of the swine erythropoietin receptor (EPOR) gene was discovered and a genotyping assay for this SNP was developed. A total of 402 gilts from lines selected either at random (control), for ovulation rate (OR) or for uterine capacity (UC) for 11 generations were unilaterally hysterectomized-ovariectomized (UHO) at 160 days of age, mated at approximately 250 days of age and slaughtered at 105 days of pregnancy. Blood samples and spleens were collected from each foetus and the numbers of corpora lutea (CL) and live foetuses, the weights of each foetus and placenta, and each foetal haematocrit were recorded. In addition, intact gilts from the OR line or from a Yorkshire, Landrace, Duroc, crossbred line (BX) were mated and farrowed. At farrowing, the numbers of fully formed and live piglets were recorded for each litter. Genomic DNA was isolated for both the UHO and intact gilts, from foetuses from the UHO gilts that were heterozygous for the EPOR SNP, and from the boars from the BX line and were then used to determine EPOR SNP genotypes. Only CC and CT gilts were observed in the control, OR and UC selected lines. Presence of the EPOR T allele was associated (P < 0.05) with increased UC in these gilts. The number of heterozygous and homozygous foetuses did not differ within UHO litters, or did EPOR genotype influence foetal haematocrit. In intact gilts from the OR line, litter size was significantly associated (P < 0.05) with EPOR SNP genotype. Finally, results from intact gilts of the BX line, in which both the gilt and the boar genotypes were known, allowed an analysis to determine the effect of the gilt and/or the foetal genotype on litter size. This analysis indicated that the predicted foetal genotype (with gilt genotype as covariate) was associated with litter size (an increase of 2.6 +/- 1.0 piglets born alive predicted for homozygous T litters compared with homozygous C litters, P < 0.01) whereas the effect of the gilt genotype (adjusted for foetal genotype) on litter size was not significant. These results indicate that the EPOR SNP is associated with UC and litter size in two distinct populations and could be useful in increasing litter size in swine that are not limited in OR.     

Total cost estimation for implementing genome-enabled selection in a multi-level swine production system

Background

Determining an animal’s genetic merit using genomic information can improve estimated breeding value (EBV) accuracy; however, the magnitude of the accuracy improvement must be large enough to recover the costs associated with implementing genome-enabled selection. One way to reduce costs is to genotype nucleus herd selection candidates using a low-density chip and to use high-density chip genotyping for animals that are used as parents in the nucleus breeding herd. The objective of this study was to develop a tool to estimate the cost structure associated with incorporating genome-enabled selection into multi-level commercial breeding programs.

Results

For the purpose of this deterministic study, it was assumed that a commercial pig is created from a terminal line sire and a dam that is a cross between two maternal lines. It was also assumed that all male and female selection candidates from the 1000 sow maternal line nucleus herds were genotyped at low density and all animals used for breeding at high density. With the assumptions used in this analysis, it was estimated that genome-enabled selection costs for a maternal line would be approximately US$0.082 per weaned pig in the commercial production system. A total of US$0.164 per weaned pig is needed to incorporate genome-enabled selection into the two maternal lines. Similarly, for a 600 sow terminal line nucleus herd and genotyping only male selection candidates with the low-density panel, the cost per weaned pig in the commercial herd was estimated to be US$0.044. This means that US$0.21 per weaned pig produced at the commercial level and sired by boars obtained from the nucleus herd breeding program needs to be added to the genetic merit value in order to break even on the additional cost required when genome-enabled selection is used in both maternal lines and the terminal line.

Conclusions

By modifying the input values, such as herd size and genotyping strategy, a flexible spreadsheet tool developed from this work can be used to estimate the additional costs associated with genome-enabled selection. This tool will aid breeders in estimating the economic viability of incorporating genome-enabled selection into their specific breeding program.