Indicators of piglet survival in an outdoor farrowing system

Pre-weaning piglet mortality continues to be a major welfare and economic concern. In outdoor farrowing systems, there is a particular need to broaden breeding goals by incorporating selection for piglet survival to improve both productivity and welfare. This study aimed to identify behavioural and physiological survival indicators that are influential in outdoor systems and that could provide additional information for use when selecting for piglet survival. Data were collected from 511 piglets from Large White × Landrace × Duroc sows and Generalised Linear Mixed Models determined which indicators were most important for piglet survival in an outdoor system. With respect to prenatal mortality (surviving vs. stillborn piglets) high ponderal index (P < 0.001) or body mass index (P < 0.001) in conjunction with being born earlier in the farrowing birth order (P < 0.001) were the most important survival indicators. Birth weight (P < 0.001) and rectal temperature 1 h after birth (P = 0.032) were the most significant postnatal survival indicators. However survival indicators identified as important in indoor, conventional farrowing crates, such as landmark behaviours (latency to reach the udder, a teat and to suckle colostrum), were not influential in this system. These results highlight the importance of studying potential indicators of survival in alternative farrowing systems to the farrowing crate.     

Does a Boar's Season of Birth Determine Semen Parameters and Reproductive Performance?

This article studies the effect of a boar's birth season and breed on semen parameters and its further reproductive performance. Research material consisted of 72 boars from three breeds (24 Polish Large White PLW, 24 Polish Landrace PL, 24 Duroc × Pietrain D×P). During the whole period of the study, selected semen parameters were analysed: semen volume, spermatozoa concentration, total number of spermatozoa, total number of motile spermatozoa, number of insemination doses and also reproductive indicators: farrowing rate, total born litter size, total number of piglets born live and still, and average piglet weight. Boars born in the winter and summer months demonstrated the highest spermatozoa concentrations (383.25 and 392.37 × 10⁶/ml), total number of spermatozoa (91.75 and 93.21 × 10⁹), total number of motile spermatozoa (76.10 and 77.99 × 10⁹) and number of insemination doses (24.53 and 24.89; p ≤0.01). Statistically lower values for these parameters were observed for boars born in the spring and especially in autumn (p ≤0.01). The significant impact of birth season on farrowing rate (p ≤ 0.05) and average piglet weight (p ≤ 0.05) was confirmed for PLW boars. For the PL breed, only the total number of piglets born live was proven to be significantly affected (p ≤ 0.05). No impact of birth season was shown on semen quality or reproductive performance for D×P boars. In our study, we showed that the birth season of a boar had a more impact on the level of semen parameters, and less on the reproductive performance indicators. The results indicated that both the quality of semen and reproductive performance varied in terms of the study factors, as well as between individual breeds of boars involved in the experiment.     

An investigation into uterine capacity based on litter and placental characteristics in two sow lines with different prolificacy (Danish Landrace x Danish Yorkshire versus German Saddleback)

Litter size in modern so called hyperprolific pig (Sus scrofa Linnaeus) breeds such as of crossbred Danish Landrace x Danish Yorkshire (LY/YL) sows increased remarkably over recent years, however, commonly associated with reduced piglet birth weight and higher within litter birth weight variability likely due to a limited uterine capacity. Since investigation into this issue is patchy, the aim of this study was to investigate uterine capacity based on litter and placental characteristics in two sow lines with different prolificacy, that is crossbred Danish genetic (Danish Landrace x Danish Yorkshire; DG; n = 14) and purebred German Saddleback (GS) sows (n = 12). Parameters recorded were litter size, piglet birth weight and vitality, placental weight and surface area as well as placental vascularization. Litters of DG were on average larger than of GS (p < .001). Piglets of DG weighed on average less than GS (p < .001) and were less vital (p < .001–.142). Increasing litter size was associated with reduced piglet birth weight and increased within litter birth weight variability in GS, but not in DG. DG had on average a lower placental weight (p < .001) and smaller placentae (p < .001) than GS, but the placenta was on average more efficient than of GS (based on the quotient of piglet and corresponding placental weight; p < .001). Vascularization of placentae was on average not or only slightly different between breeds (p < .05 – .982). Remarkably, however, vascularization of the lateral and apical chorionic epithelium of the chorionic ridges as the immediate foetal/maternal interface was on average slightly higher in DG than GS (p < .05–.111). Results thus demonstrate that uterine capacity based on litter and placental characteristics is higher in DG than GS sows.     

Within-litter variation of birth weight in hyperprolific Czech Large White sows and its relation to litter size traits, stillborn piglets and losses until weaning

Data from about 2900 litters (approximately 40,000 piglets) originating from 1063 Czech Large White hyperprolific sows were analyzed. The phenotypic and genetic relations between litter size traits, piglet mortality during farrowing and from birth to weaning and several statistics referring to the distribution of the birth weight within litter were analyzed. All genetic parameters were estimated from multi-trait animal models including the following factors: mating type (natural service or insemination), parity, linear and quadratic regression on age at first farrowing (1st litter) or farrowing interval (2nd and subsequent litters), herd-year-season effect and additive-genetic effect of the sow. The phenotypic correlations of the mean birth weight with the total number of piglets born and piglets born alive were − 0.30. Traits describing the variability of the birth weight within litter (range, variance, standard deviation, coefficient of variation) were mostly positively correlated with litter size. A statistically significant phenotypic correlation (− 0.09 to − 0.15) between mean birth weight and losses at birth and from birth to weaning was found. The heritability for the number of piglets born, piglets born alive and piglets weaned was around 0.15. The number of stillborn piglets had only a very low heritability less than 0.05, whereas the heritability for losses from birth to weaning was 0.13. The heritabilities of the mean, minimal and maximal birth weight were 0.16, 0.10 and 0.10, respectively. The heritability for all statistics and measures referring to the variability of the birth weight within litter was very low and did never exceed the value of 0.05. An increase in litter size was shown to be genetically connected with a decrease in the mean piglet birth weight and an increase in the within-litter variability of birth weight. Selection on litter size should be accompanied by selection on mortality traits and/or birth-weight traits. Losses from birth to weaning and the minimal birth weight in the litter were proposed as potential traits for a selection against piglet mortality.     

Between-breed variability of stillbirth and its relationship with sow and piglet characteristics

Litter characteristics at birth were recorded in 4 genetic types of sows with differing maternal abilities. Eighty-two litters from F(1) Duroc x Large White sows, 651 litters from Large White sows, 63 litters from Meishan sows, and 173 litters from Laconie sows were considered. Statistical models included random effects of sow, litter, or both; fixed effects of sow genetic type, parity, birth assistance, and piglet sex, as well as gestation length, farrowing duration, piglet birth weight, and litter size as linear covariates. The quadratic components of the last 2 factors were also considered. For statistical analyses, GLM were first considered, assuming a binomial distribution of stillbirth. Hierarchical models were also fitted to the data to take into account correlations among piglets from the same litter. Model selection was performed based on deviance and deviance information criterion. Finally, standard and robust generalized estimating equations (GEE) procedures were applied to quantify the importance of each effect on a piglet's probability of stillbirth. The 5 most important factors involved were, in decreasing order (contribution of each effect to variance reduction): difference between piglet birth weight and the litter mean (2.36%), individual birth weight (2.25%), piglet sex (1.01%), farrowing duration (0.99%), and sow genetic type (0.94%). Probability of stillbirth was greater for lighter piglets, for male piglets, and for piglets from small or very large litters. Probability of stillbirth increased with sow parity number and with farrowing duration. Piglets born from Meishan sows had a lower risk of stillbirth (P < 0.0001) and were little affected by the sources of variation mentioned above compared with the 3 other sow genetic types. Standard and robust GEE approaches gave similar results despite some disequilibrium in the data set structure highlighted with the robust GEE approach.     

Colostrum yield and litter performance in multiparous sows subjected to farrowing induction

The consumption of colostrum at a low level can compromise the survival and growth of piglets. Therefore, this study aimed to evaluate the effect of farrowing induction on colostrum yield, IgG concentration and the survival and performance of piglets until the weaning. Sows of parity 3 to 7 were assigned into two groups: Control (n = 48), sows with spontaneous farrowing; and induction (n = 48), sows induced to farrow on day 114 of gestation with a PGF₂ analogue. Colostrum and blood samples were collected from the sows, at farrowing and 24 hr later. Blood samples from the piglets were collected at 24 hr after birth. The performance of the piglets was evaluated in a subsample of 28 litters from each group. All piglets were weighed at 7, 14 and 20 days of age. The farrowing length, the number of piglets born alive, stillborn piglets, weight at birth, litter weight at birth and colostrum yield were not significantly affected (p > .05) by farrowing induction. There was no difference between the groups (p > .05) in the percentage of sows with obstetric interventions. Serum IgG concentration, in both sows and piglets, and colostrum IgG concentration were similar between the groups (p > .05). Furthermore, survival rate, piglet weight and litter weight at 7, 14 and 20 days of age were also similar between the groups (p > .05). Therefore, it can be concluded that the farrowing induction performed on day 114 of gestation does not affect the colostrum yield, the IgG concentration in colostrum and serum of piglets, and the litter performance until the weaning.     

Aggregate diversity: New approach combining within- and between-breed genetic diversity

Between-breed genetic diversity is classically considered as a major criterion to be taken into account when setting priorities for conservation of domestic animal breeds. However, it has been argued that methods based on the between-breed component of genetic diversity may not be optimal because they ignore the within-breed component of variation. The paper considers the most common methods used to evaluate those two components when genetic diversity is evaluated on the basis of genetic markers, and proposes to define an aggregate diversity combining linearly the two components. This implies defining for each breed (or population) its contributions to the between-breed and to the within-breed diversity. When defining an aggregate diversity, one can weight these contributions by F_ST and 1−F_ST, respectively, since the fixation index F_ST of Wright represents the proportion of the total genetic variation which is due to differences in allelic frequencies between populations. Such an approach is valid when the objective is genetic improvement by selection within a so-called “meta-population”. However, in a more general context of animal breeding, when heterosis and complementarities between breeds have to be considered, as well as adaptation to specific environments, more weight should be given to the between-breed variation. The proper weight to apply may require solutions adapted to each particular situation. In a long-term conservation perspective, priorities should also take into account the degree of endangerment of each breed. By combining diversity contributions and probability of extinction, a cryopreservation potential (or priority) may be estimated for each breed. The problem is illustrated on a sample of 11 European pig breeds typed for 18 microsatellite loci.     

Direct and maternal breed effects on growth and milk intake of piglets: Meishan versus Dutch breeds

Cross fostering techniques were used to evaluate pre-natal (direct genetic and maternal) and post-natal (maternal) breed effects in Meishan and Dutch breeds on milk intake and growth of piglets during the suckling period and growth after weaning. Meishan as well as Dutch sows nursed mixed litters of Meishan and Dutch piglets. Birth weight of Dutch as compared to Meishan piglets was 56% higher. The effects of this birth weight difference on milk intake and growth of piglets were studied. Data on 44 mixed litters nursed by 21 Dutch and 23 Meishan sows were available.At an average birth weight difference, growth rate from birth to 21 and 21–35 d was 25 and 31% higher for Dutch than for Meishan piglets respectively, while milk intake per piglet at days 13 and 30 of lactation was 38 and 36% higher, respectively. Differences between Dutch and Meishan sows were small.Higher growth during the suckling period of Dutch as compared to Meishan piglets was mainly caused by their higher birth weight. Results indicate that Meishan sows have good maternal characteristics, i.e. significantly lower piglet mortality and the ability to raise also the heavier, more demanding Dutch piglets.     

Factors affecting piglet mortality in loose farrowing systems on commercial farms

Crating sows in farrowing systems greatly restricts their normal behaviour (e.g. movement, nest-building, leaving the nest site for defecation), which is usually justified by the assumption that piglet mortality is higher with loose-housed sows. Based on experiments showing that this is not the case, farrowing crates were banned in Switzerland in 1997, with a 10-year transitional period. Since then, many farms have introduced loose farrowing systems, enabling an analysis of risk factors for piglet mortality in crateless farrowing systems based on a large sample size. Data from a Swiss sow recording scheme (UFA2000) were analysed using generalised linear mixed-effects models with an underlying Poisson distribution. Average total piglet mortality for the years 2002 and 2003 on 99 farms (N = 12457 litters) with loose farrowing systems amounted to 1.36 liveborn piglets per litter. The number of crushed piglets was 0.64 piglets per litter, whereas the number of piglets that died for other reasons was 0.72 piglets per litter.Herd size, pen size, possibility of confinement of the sow, presence of piglet protection bars and year of data collection did not significantly influence total piglet losses, losses due to crushing and losses due to reasons other than crushing. With greater litter size at birth, significantly more losses occurred due to all reasons (total, crushed, others). Total piglet mortality and losses for reasons other than crushing were significantly higher in older sows. Losses were therefore mainly attributable to sow-related characteristics rather than to the design of the farrowing pen.     

Variability of piglet birth weights: A systematic review and meta-analysis

The objective of the study was to evaluate the effects of litter size and supplementation of functional amino acids on the piglet birth weight variability through of a systematic review and meta-analysis. PubMed, ISI Web of Science, Science Direct, Scopus and SciELO are the main used databases and were searched in January 2019 by using the following keywords and their combinations: within-litter birth, weight variability, piglets, litter size, sow, amino acids, gestation, uniformity, CV and/or SD. Of the 64 pre-selected articles, only articles presenting the coefficients of variation and/or standard deviations according to the litter size and different levels of amino acid supplementation in the sow diets during gestation were selected. The average birth weights of total and live piglets were 43% lower in litters from sows with high prolificacy than those from sows with low prolificacy. The weight variability was affected by high prolificacy sows, with increases of 4.04% and 4.54% in the coefficients of variation of total and born alive piglets respectively (p = .074; p = .009). The standard deviation increased by 180 g in born alive piglets to high prolificacy sows. The coefficients of variation of total and live piglets born from high prolificacy sows showed an increase of 4.04% and 4.54% respectively (p = .07; p < .05). There was a tendency for reduced weight variability with amino acids supplementation when considering the standard deviation of total born (p = .072). However, reproductive performance was not significantly influenced (p > .05). In conclusion, the average litter weight and the number of piglets born influence weight variability. Amino acids supplementation may reduce the birth weight variability between piglets. However, this effect depends on the amino acid used, the levels of supplementation and on other factors not completely addressed in this study. Thus, more research is necessary to fully elucidate this topic.     

Variables related to the progress of parturition and probability of stillbirth in swine

Sow and piglet variables related to probability of stillbirth and to viability score were analyzed in litters from 98 multiparous Yorkshire sows. Immediately after the birth of each piglet, viability was scored using Randall's method. Sow variables related to the probability of stillbirth were average birth weight of the litter (p = 0.0001), sow age (p = 0.001), sow condition score (p = 0.003), length of gestation (p = 0.005), and number of piglets in the litter (p = 0.01). Sow variables related to average viability score were average birth weight of the litter (p = 0.001), standard deviation in birth weight in the litter (p = 0.02), sow age (p = 0.03), sow condition score (p = 0.03), and length of gestation (p = 0.03). Piglet variables related to probability of stillbirth were piglet hemoglobin (p = 0.0001), position in the birth order (p = 0.0001), broken umbilical cord (p = 0.0004), and preceding birth interval (p = 0.0004). Piglet variables related to viability score were piglet hemoglobin (p = 0.0001), position in the birth order (p = 0.0001), broken umbilical cord (p = 0.0001), preceding birth interval (p = 0.0001), and birth weight (p = 0.004). Preceding birth interval was related to whether the piglet was live or stillborn (p = 0.0001), to position in the birth order (p = 0.003), and to the sex of the piglet (p = 0.03).

The results demonstrated that sow and piglet variables were highly correlated to probability of stillbirth and to viability score. In addition it was also found that the probability of stillbirth was not associated with the duration of farrowing but with the number of piglets in the litter and piglet hemoglobin level. This study also found that lower weight piglets tend to have poor viability, but are not more prone to stillbirth as commonly suggested. These low viability piglets may survive if the necessary care is given during the farrowing process.

     

Genetic parameters for litter size,piglet growth and sow's early growth and body composition in the Chinese–European line Tai Zumu

Genetics of piglet growth in association with sow's early growth and body composition were estimated in the Tai Zumu line. Piglet and sow's litter growth traits were calculated from individual weights collected at birth and at 3 weeks of age. Sow's litter traits included the number of piglets born alive (NBA), the mean piglet weight (MW) and the standard deviation of weights within the litter (SDW). Sow's early growth was measured by the age at 100 kg (A₁₀₀), and body composition included backfat thickness (BF₁₀₀). A main objective of this study was to estimate separately the direct genetic effect (d) and the maternal genetic effect (m) on piglet weight and daily weight gain during lactation. Variance components were estimated using the restricted maximum likelihood methodology based on animal models. The heritability estimates were 0.19 for NBA, 0.15 and 0.26 for SDW and MW at 3 weeks and 0.42 and 0.70 for A₁₀₀ and BF₁₀₀. The NBA was almost independent from SDW. Conversely, the A₁₀₀ and BF₁₀₀ were correlated unfavourably with SDW (r_g<−0.24, SE<0.12). A stronger selection for litter size should have little effect on litter homogeneity in weights. Selection for lean growth rate tends to favour heterogeneity in weights. The direct effect on piglet weight at birth and daily weight gain accounted for 12% (h² (d) = 0.02) and 50% (h² (d) = 0.11) of the genetic variance, respectively. The association between d and m for piglet weight was not different from zero at birth (r_g = 0.19, SE = 0.27), but a strong antagonism between d and m for daily weight gain from birth to 3 weeks was found (r_g = −0.41, SE = 0.17). Substantial direct and maternal genetic effects influenced piglet growth until weaning in opposite way.     

Effects of L‐citrulline supplementation on heat stress physiology,lactation performance and subsequent reproductive performance of sows in summer

Lactating sows are susceptible to heat stress (HS). Part of the thermoregulatory response to HS is to increase peripheral blood flow, which is mediated in part by the vasodilator, nitric oxide (NO). Therefore, the aim of this experiment was to determine the effect of supplementation of L‐citrulline, a NO precursor, on symptoms of HS, lactation performance and subsequent reproductive performance of sows in summer. A total of 221 summer farrowing mixed parity sows were fed either a control diet or supplemented with 1% L‐citrulline upon entry to the farrowing house (6 ± 1.8 days for mean ± standard deviation [SD] before farrowing) until weaning (26 ± 1.5 days). The average daily minimum and maximum temperature in the farrowing house was 21.0 ± 1.88 and 29.2 ± 3.82°C (mean ± SD). Rectal temperature, respiration rate, and plasma and urinary nitrite and nitrate (NOx) of sows were measured on the 19th day post‐farrowing. Supplemental L‐citrulline in the diet did not affect the number of piglets born alive, feed intake of sows, body weight or backfat thickness of sows at weaning, or litter weight gain. L‐citrulline tended to reduce piglet pre‐weaning mortality rate from 18.6% to 15.6% (p = 0.058). L‐citrulline reduced the respiration rate of sows compared to the control diet at 17:00 hr (Time × Diet, p < 0.001); however, rectal temperature was not affected. L‐citrulline tended to increase urinary NOx concentrations (127 vs. 224 µM, p = 0.057) but not plasma NOx concentrations. L‐citrulline did not affect farrowing rate or number of piglets born alive in the subsequent parity. In conclusion, L‐citrulline supplementation reduced respiration rate of lactating sows and reduced piglet pre‐weaning mortality rate in summer. Whether the effects were due to a NO‐dependent mechanism requires further validation.     

Establishment of a multilevel linear model to analyse the factors affecting piglet litter performance at birth

This study aimed to establish a feasible model for analysing factors affecting piglet litter performance at birth. Data of 61,984 litters were collected from 16 herds, and general linear model (GLM), multilevel Poisson regression model (MPM) and multilevel linear model (MLM) were established to compare their goodness of fit for these data. Influencing factors of piglet litter performance at birth were analysed using the established optimal model. Results showed the intraclass correlation coefficients of total born piglets (TBP), piglets born alive (PBA), low-birth-weight piglets (LBW), and average birth weight of piglets (ABW) reached 27.89%, 23.88%, 24.66% and 22.27%, respectively (p < .05). Akaike's information criterion and Bayesian information criterion in MLM of TBP, PBA, LBW and ABW were lower than those in GLM. Pearson residuals in MPM increased to nearly 1 after introduction of a discrete scale factor, and the p values in MPM were similar to those in MLM. Analyses of MLM indicated crossbred sows with good management supplemented with oregano essential oil and farrowing at warm season had higher TBA, PBA and ABW, but lower LBW than other sows (p < .05). In conclusion, MLM is superior to GLM and can replace MPM in analysing discrete data with hierarchical structure in pig production. More importantly, other potential influencing factors of litter performance at birth can be analysed using the established MLM in the future.     

Pig colostrum and milk composition:comparisons between Chinese Meishan and US breeds

The composition of colostrum and milk from Chinese Meishan and American Yorkshire gills was characterized at farrowing (d 0), 24 h after farrowing (d 1), and on d 7 and 21 of lactation. Lactose concentrations were lower for Meishan vs. Yorkshire gills on d 0, 1, and 7, but not on d 21. Fat concentrations were higher for Meishan than for Yorkshire gilts at each sampling time, particularly on d 1 and 7. Total protein concentrations were similar on d 0 and 1, but lower for Meishan than for Yorkshire gilts on d 7 and 21. Milk proteins from Meishan gilts, Yorkshire gilts, and crossbred sows (Yorkshire × Hampshire × Landrace) were compared by polyacrylamide gel electrophoresis. Differences in size or relative proportion of caseins and the major whey proteins were not observed. Several high molecular weight whey proteins and a minor casein band were observed to segregate among breeds. These protein differences among breeds may be valuable markers in studies on lactating Mei-shan × Yorkshire crossbred animals. Results of this study suggest that colostrum and milk composition should not be a major limiting factor in survival and growth of piglets born to Meishan × Yorkshire crossbred gilts.     

Genetic parameter estimates among scale activity score and farrowing disposition with reproductive traits in swine

The primary objective of this study was to determine if certain behavior traits were genetically correlated with reproduction. If 1 or both of the behavior traits were found to be correlated, a secondary objective was to determine if the behavior traits could be useful in selecting for more productive females. A scale activity score taken at 5 mo of age and a farrowing disposition score taken at farrowing were selected as the behavioral traits. Scale activity score ranged from 1 to 5 and farrowing disposition ranged from 1 to 3. Reproductive traits included age at puberty, number born alive, number born dead, litter birth weight, average piglet birth weight, number weaned, litter weaning weight, average weaning weight, wean-to-estrus interval, ovulation rate including gilts, and postweaning ovulation rate. Genetic correlations between scale activity score and reproduction ranged from -0.79 to 0.61. Three of the correlations, number born alive (P < 0.01), average piglet birth weight (P < 0.001), and wean-to-estrus interval (P = 0.014), were statistically significant but included both favorable and antagonistic correlations. In contrast, all but 1 of the farrowing disposition correlations was favorable and ranged from -0.66 to 0.67. Although only the correlation with litter birth weight was significant (P = 0.018), the consistent favorable direction of all farrowing disposition correlations, except average weaning weight, shows a potential for inclusion of farrowing disposition into a selection program.     

Altrenogest Treatment Associated with a Farrowing Induction Protocol to Avoid Early Parturition in Sows

This study investigated the effect of altrenogest treatment on the farrowing development of sows, and birth weight (BW) and piglet survival until the third day of life. Three control groups were used: (i) sows that farrowed spontaneously before 114 day of gestation (CONT <114); (ii) sows that spontaneously farrowed at ≥114 day of gestation (CONT ≥114); (iii) sows that farrowed at ≥114 day with cloprostenol treatment (CONTCLOPR). Other sows were treated with altrenogest (Regumate^®) for 3 days (days 111, 112 and 113 of gestation): one group gave birth spontaneously (ALT) and the other group received altrenogest until day 113 and cloprostenol on day 114 (ALTCLOPR). There were no differences (p > 0.05) in farrowing duration, BW, coefficient of variation (CV) of BW, stillborn piglets, mummified foetuses, percentage of light piglets and survival until Day 3 between sows with and without cloprostenol treatment, in both control (CONT ≥114 vs CONTCLOPR) and altrenogest‐treated sows (ALT vs ALTCLOPR). Further comparisons were performed taking into account three groups: sows with early delivery (CONT <114 – farrowing before 114 days of gestation; n = 56), sows with longer gestation (CONT ≥114 – with and without cloprostenol treatment sows; n = 103) and ALT sows (with and without cloprostenol treatment; n = 105). Gestation length of CONT ≥114 and ALT sows was similar (p > 0.05), but higher than in CONT <114 sows. There were no differences (p > 0.05) between groups in farrowing duration, CV of BW, and percentages of stillborn piglets and mummified foetuses. Sows of CONT <114 group had a larger litter size and a lower BW than sows of the other two groups (p < 0.05). Sows of CONT <114 group had a higher percentage of lighter piglets and a lower piglet survival rate (p < 0.05) than ALT sows. In conclusion, altrenogest treatment proved to be an efficient method to avoid early parturition in 3–5 parity sows resulting in heavier piglets at birth.     

Relationship between postnatal piglet mortality,environmental factors and management around farrowing in herds with loose-housed,lactating sows

Abstract

The objective of this study was to investigate management routines and environmental factors influencing postnatal piglet mortality in commercial herds with individually loose-housed sows. Last year production records from 39 herds were used. We gathered information on specific routines as well as environmental factors by visiting every farm once. Herds practising moderate roughage feeding during pregnancy tended to have lower piglet mortality (p=0.06). Use of farrowing rails along all the sides of the pen resulted in lower piglet mortality than when no rails were present (p<0.01). Herds that hardly used any litter in the sow area at the time of farrowing had significantly higher piglet mortality than herds that used a moderate or large amount (p<0.05). Helping the piglets to obtain colostrum immediately after birth also reduced mortality (p<0.05), whereas other routines such as shutting the piglets inside the creep area while feeding the sow did not have any significant effect.     

Direct,maternal and nurse sow genetic effects on farrowing-, pre-weaning- and total piglet survival

Peri- and postnatal survival data, including birth weights and cross-foster information from two line/farm combinations with 33 717 and 29 200 piglets, respectively, were analyzed to find the best genetic model to describe piglet survival. This was done in terms of direct (piglet), maternal and nurse sow genetic effects, maternal to cover uterine quality and nurse sow to cover mothering ability. The two component traits, farrowing and pre-weaning survival and — birth weight, the most important factor for survival — were similarly analyzed. As fixed effects, Year/Season, cross, parity, birth weight in classes of 100 g, litter size as such, and sex were included in the analyses. Models combining the different genetic effects were compared on the basis of the log-likelihood. A maternal/nurse sow model fitted the data best for pre-weaning survival, a direct/maternal model for birth weight, a direct model for farrowing survival in the dam line and a direct/maternal model for farrowing survival in the sire line. Including nurse sow effect in a model for piglet survival as a whole gave erratic results, making it difficult to define an optimal model. Estimated heritabilities for pre-weaning survival, measured on the binary scale, in the dam line were 0.02±0.005 for both maternal and nurse sow effects. Heritabilities for birth weight were, on average for the two lines, 0.04±0.01 for the direct effect and 0.20±0.03 for the maternal effect. In conclusion, selection for increased component traits of piglet survival is possible.     

Genetic diversity in native and commercial breeds of pigs in Portugal assessed by microsatellites

Population structure and genetic diversity in the Portuguese native breeds of pigs Alentejano (AL), Bísaro (BI), and Malhado de Alcoba?a (MA) and the exotic breeds Duroc (DU), Landrace (LR), Large White (LW), and Pietrain were analyzed by typing 22 microsatellite markers in 249 individuals. In general, the markers used were greatly polymorphic, with mean total and effective number of alleles per locus of 10.68 and 4.33, respectively, and an expected heterozygosity of 0.667 across loci. The effective number of alleles per locus and expected heterozygosity were greatest in BI, LR, and AL, and least in DU. Private alleles were found in 9 of the 22 markers analyzed, mostly in AL, but also in the other breeds, with the exception of LW. The proportion of loci not in Hardy-Weinberg equilibrium in each breed analyzed ranged between 0.23 (AL) and 0.41 (BI, LW, and Pietrain), mostly because of a less than expected number of heterozygotes in those loci. With the exception of MA, all breeds showed a significant deficit in heterozygosity (F(IS); P < 0.05), which was more pronounced in BI (F(IS) = 0.175) and AL (F(IS) = 0.139), suggesting that inbreeding is a major concern, especially in these breeds that have gone through a genetic bottleneck in the recent past. The analysis of relationships among breeds, assessed by different methods, indicates that DU and AL are the more distanced breeds relative to the others, with the closest relationship being observed between LR and MA. The degree of differentiation between subpopulations (F(ST)) indicates that 0.184 of the total genetic variability can be attributed to differences among breeds. The analysis of individual distances based on allele sharing indicates that animals of the same breed generally cluster together, but subdivision is observed in the BI and LR breeds. Furthermore, the analysis of population structure indicates there is very little admixture among breeds, with each one being identified with a single ancestral population. The results of this study confirm that native breeds of pigs represent a very interesting reservoir of allelic diversity, even though the current levels of inbreeding raise concerns. Therefore, appropriate conservation efforts should be undertaken, such as adopting strategies aimed at minimizing inbreeding, to avoid further losses of genetic diversity.