A performance test for boar taint compounds in live boars

Genetically reducing boar taint using low-taint lines is considered the most sustainable and economic long-term alternative to surgical castration of male pigs. Owing to the high heritability of the main boar taint components (androstenone, skatole and indole), breeding is an excellent tool for reducing the number of tainted carcasses. To incorporate boar taint into breeding programmes, standardized performance testing is required. The objective of this study was to develop and formally present a performance test for the main boar taint compounds on live breeding candidates. First, a standardized performance test for boar taint was established. A biopsy device was developed to extract small tissue samples (200 to 300 mg) from breeding candidates. Quantification of boar taint components from these small samples using specialized chemical extraction methods proved accurate and repeatable (r = 0.938). Following establishment of the method, biopsy samples of 516 live boars (100 to 130 kg live weight) were collected in the second step. Various mixed linear models were tested for each boar taint compound; models were ranked in terms of their information content. Pedigree information of 2245 ancestors of biopsied animals was included, and genetic parameters were estimated using univariate and multivariate models. Androstenone (in μg/g liquid fat (LF): mean = 0.578, σ = 0.527), skatole (in μg/g LF: mean = 0.033, σ = 0.002) and indole (in μg/g LF: mean = 0.032, σ = 0.002) levels obtained by biopsy were plausible. Heritability estimates for androstenone calculated with univariate (0.453) and multivariate (0.452) analyses were comparable to those in the literature. Heritabilities for skatole (0.495) and indole (0.550) were higher than that for androstenone. Genetic and phenotypic correlations were similar to those published previously. Our results show that data on boar taint compounds from small adipose samples obtained by biopsy provide similar genetic parameters as that described in the literature for larger samples and are therefore a reliable performance test for boar taint in live breeding candidates.     

Fertility test of frozen boar semen.

The fertility results of two experiments are presented. In experiment 1, the semen was frozen in tris-fructose-EDTA or BF3 diluents at 0-25 X 10(9)/ml sperm concentration and extended after thawing with either seminal plasma (SP) or the freezing medium (FM) containing no cryoprotective agent. In the second experiment the semen was glycerolated by two methods, frozen at 1-0 X 10(9)/ml sperm concentration, and extended wtih FM before insemination. Fertility after double insemination within one oestrus with semen frozen in tris-fructose-EDTA or BF3 diluents varied depending on the medium used for extension of thawed semen. The farrowing rates for semen frozen in the former diluent with FM and SP post-thawing media were 4/8 and 1/8 respectively, and for semen frozen BF3 diluent with FM and SP post-thawing extenders 1/8 and 5/8. The mean farrowing for the 32 animals inseminasted was 34-4%. Pregnancies for semen frozen in tris-fructose-EDTA and glycerolated at 30 or 5 degrees C were 5/12 and 4/12 respectively, and for single and double inseminations 6/12 and 3/12 respectively. Of 24 animals inseminated 37-5% farrowed.     

Impact of genetic selection on management of boar replacement

Boars in an artificial insemination centre have been selected for their superior genetic potential, with 'superior' being defined as having traits the customer wants transmitted to his herd. The ability to meet the customers' needs depends on the heritability of the trait, the geneticist's success in devising a selection scheme for the trait in balance with other economically important traits, and the boar's ability to produce sperm that can fertilise oocytes. Genetic evaluation research over the past 20 years has greatly increased the number of traits for which a boar can be selected: currently in the Canadian national program, these include age at 100 kg, backfat at 100 kg, feed efficiency, lean yield and litter size. In the near future, traits that are very likely to be added to this selection list include piglet survival, marbling, loin eye area and structure traits. In Canada, sires are ranked on two estimated breeding value (EBV) indices; one, focused on development of terminal sire lines, is based on the growth and yield traits and another, primarily focused on maternal line development, de-emphasises these traits and incorporates litter size. Boars that are in Canadian AI centres because of their excellent growth traits are typically in the top 5-10% of the national population for terminal sire line index, but they may be only average or substandard for litter size. Conversely, boars selected to be in the top 5-10% for conveying such reproductive traits as litter size may only be in the top 33% for growth traits. The more offspring from a superior boar in either of these indices, the faster the population average for the trait improves. The original sire gets knocked out of the elite group, is culled and replaced by a higher ranked young boar from the now improved general population. Although genetic superiority should govern an AI centre's selection and culling of boars, decision-making in real life is seldom that simple. Selection criteria may be contradictory as above, or a boar with truly superior traits may be excluded because a newly-developed molecular genetics test determines he carries an undesirable gene such as PSS, RN or others being developed. Selection for terminal sire or maternal line traits can ignore important practical factors that affect an AI centre--boars with superior genetics may not produce good semen because skeletal or penile problems prevent ejaculation, or because sperm production is poor due to a genetic flaw, disease, or some other cause. Interestingly, selection pressure for one trait may inadvertently select for a trait that is linked but whose linkage is unrecognised, and such unintentionally selected genes could benefit, harm, or have no effect on production traits. An AI centre serving a variety of customers must select boars in anticipation of their customers' needs (including new, foreign and niche markets). A centre should also review its genetic evaluation results and progeny records, both to critique its own selection success and to try to detect unexpected linkages. Finally, an AI centre needs to predict its own future, selecting not just for production traits for the swine producer, but also for factors that enhance the centre's efficiency including boar conformation and temperament, and sperm quantity, quality and hardiness. Can we select for efficiency? Our colleagues in dairy cattle AI evaluate bull performance--should the swine industry consider evaluation of male fertility traits?     

Reproductive performance of wild boar females in Portugal

Reproductive tracts of 214 female wild boars collected in Central Portugal between October and February over the period 1997 to 2001 were examined. From this material, we were able to determine reproductive phenology (conception and birth periods) as well as age and weight of sows at puberty, ovulation rates of adults, foetal sex ratio, levels of intrauterine mortality, final litter size and postnatal mortality. Differences between year, region, age and body weight were analysed. A total of 66.8% of the females examined were gestating or lactating and 96.3% of these weighed >40 kg. The highest proportions of pregnant sows were found in the adult age/weight classes (74%). None of the juvenile females (1 year old and younger) were lactating and only 7% was pregnant. The average number of foetuses/female (4.1 ± 1.2SD) and that of corpora lutea per female (4.6 ± 1.7SD) increased from lighter and younger to heavier and older wild sows. Foetal sex ratio was biased towards males (1.3:1). Observed intrauterine mortality rate (9.7%) and postnatal mortality (6.3%) were among the lowest recorded in European wild boar populations. The productivity rate of the Central Portuguese wild boar population was calculated as 1.1 young per individual in the population. Conception and birth periods did not differ significantly between the considered 4 years. Birth synchronisation was pronounced in all the years, with a peak of births occurring in March.     

Efficiency of different selection strategies against boar taint in pigs

The breeding scheme of a Swiss sire line was modeled to compare different target traits and information sources for selection against boar taint. The impact of selection against boar taint on production traits was assessed for different economic weights of boar taint compounds. Genetic gain and breeding costs were evaluated using ZPlan+, a software based on selection index theory, gene flow method and economic modeling. Scenario I reflected the currently practiced breeding strategy as a reference scenario without selection against boar taint. Scenario II incorporated selection against the chemical compounds of boar taint, androstenone (AND), skatole (SKA) and indole (IND) with economic weights of −2.74, −1.69 and −0.99 Euro per unit of the log transformed trait, respectively. As information sources, biopsy-based performance testing of live boars (BPT) was compared with genomic selection (GS) and a combination of both. Scenario III included selection against the subjectively assessed human nose score (HNS) of boar taint. Information sources were either station testing of full and half sibs of the selection candidate or GS against HNS of boar taint compounds. In scenario I, annual genetic gain of log-transformed AND (SKA; IND) was 0.06 (0.09; 0.02) Euro, which was because of favorable genetic correlations with lean meat percentage and meat surface. In scenario II, genetic gain increased to 0.28 (0.20; 0.09) Euro per year when conducting BPT. Compared with BPT, genetic gain was smaller with GS. A combination of BPT and GS only marginally increased annual genetic gain, whereas variable costs per selection candidate augmented from 230 Euro (BPT) to 330 Euro (GS) or 380 Euro (both). The potential of GS was found to be higher when selecting against HNS, which has a low heritability. Annual genetic gain from GS was higher than from station testing of 4 full sibs and 76 half sibs with one or two measurements. The most effective strategy to reduce HNS was selecting against chemical compounds by conducting BPT. Because of heritabilities higher than 0.45 for AND, SKA and IND and high genetic correlations to HNS, the (correlated) response in units of the trait could be increased by 62% compared with scenario III with GS and even by 79% compared with scenario III, with station testing of siblings with two measurements. Increasing the economic weights of boar taint compounds amplified negative effects on average daily gain, drip loss and intramuscular fat percentage.     

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.     

Daily selection of habitat in wild boar (Sus scrofa)

Spatial segregation of the sexes is observed in numerous species of ungulates, but are there other forms of segregation in species where spatial segregation is not present, such as in the wild boar? This study investigates the differences in habitat selection between two categories of individuals whose ecological requirements are supposedly divergent: subadult males, and females with dependent piglets. The proportion of the day spent in each category of habitat was used as a parameter representative of daily decisions. The overall results fit with the hypothesis that females with piglets avoid insecure habitats, and that both categories select habitats on the basis of food richness. In addition, it was found that the pattern of habitat selection depends on the total time spent moving slowly. A short duration of slow movement was observed only in males, but the time dedicated to efficient foraging (in rich habitats) was sufficient in all observations of all animals. Subadult males, therefore, do not differ from each other in foraging efficiency, but in the time spent on slow movement in secure habitats. Those spending more time active in secure habitats have the opportunity of performing more potentially beneficial activities such as social interactions and sexual contacts.     

Zona-penetration in vitro test for evaluating boar sperm fertility

We investigated the capacity of porcine sperm-zona binding and penetration by using bioassay to differentiate between spermatozoa from fertile and subfertile boars. Semen was collected from Large White boars grouped into categories of fertile and subfertile (n=5 per each group) according to the results of artificial insemination. Boars in both groups showed similarly hyperactivated sperm motility at insemination (44.72 and 43.03% respectively) regardless of the lower percentage of progressive motility observed in the ejaculates of subfertile boars. At in vitro insemination, a high proportion of the sperm population (43.76%) in the subfertile boars was without acrosomes, while in the fertile boars this proportion was only 24.35%. The sperm penetration rate of fertile boars reached 66.03% while that of subfertile boars was only 25.08%. In conclusion, the results of our study showed that the penetration rate by boar spermatozoa of the zona pellucida can be used to predict fertility and/or as an in vitro standard for describing porcine semen characteristics.     

Prediction of effects of beef selection indexes on greenhouse gas emissions

Genetic improvement in production efficiency traits can also drive reduction in greenhouse gas emissions. This study used international ‘best-practice’ methodology to quantify the improvements in system-wide CO₂ equivalent emissions per unit of genetic progress in the Irish Maternal Replacement (MR) and Terminal (T) beef cattle indexes. Effects of each index trait on system gross emissions (GE) and system emissions intensity (EI) were modelled by estimating effects of trait changes on per-animal feed consumption and associated methane production, per-animal meat production and numbers of animals in the system. Trait responses to index selection were predicted from linear regression of individual bull estimated breeding values for each index trait on their MR or T index value, and the resulting regression coefficients were used to calculate trait-wise responses in GE and EI from index selection. Summed over all trait responses, the MR index was predicted to reduce system GE by 0.810 kg CO₂e/breeding cow per year per € index and system EI by 0.009 kg CO₂e/kg meat per breeding cow per year per € index. These reductions were mainly driven by improvements in cow survival, reduced mature cow maintenance feed requirements, shorter calving interval and reduced offspring mortality. The T index was predicted to reduce system EI by 0.021 kg CO₂e/kg meat per breeding cow per year per € index, driven by increased meat production from improvements in carcass weight, conformation and fat. Implications for incorporating an EI reduction index to the current production indexes and long-term projections for national breeding programs are discussed.     

A short hypoosmotic swelling test for the prediction of boar sperm fertility

This study was designed to explore the relationship between the ejaculate response to a hypoosmotic swelling test (HOST) and in vivo fertility in a group of 38 boars The hypoosmotic test used was a modification of the HOST that involves a shorter incubation time (5 vs 120 min) and lower osmotic pressure (75 vs 150 mOsm/kg). Ejaculates containing less than 20% abnormal spermatozoa were selected and checked for percentage of motility, percentage of normal acrosomes, percentage of short ORT and percentage of cells showing positive short HOST (sHOST) results Two hundred eightyeight sows were inseminated to obtain in vivo fertility and prolificacy data. No differences were shown between technicians in the sHOST results obtained. Significant differences were recorded between boars in sHOST results (p < 0.002). Only the sHOST result presented a significant correlation with in vivo fertility (r = 0.43, p < 0.01). Short HOST data significantly improved fertility prediction of routine semen analysis tests. Unlike motility and acrosomal status, sHOST values showed a significant decrease when fresh ejaculates (37 degrees C) were stored for 24 h at 15 degrees C, indicating possible damage due to cold shock.     

The use of constrained selection indexes in breeding for economic merit

Summary Various methods exist for the derivation of restricted and/or desired gains selection indexes, and their use in applied breeding has been advocated. It is shown that there exists a set of implied linear economic weights for all constrained indexes and their derivation is given. Where economic weights are linear and known, a standard selection index is, by definition, optimal and thus a constrained index will usually be suboptimal. It is argued that economic weights can always be estimated and that the effects of uncertain weights can be examined by sensitivity analysis. If economic weights are nonlinear, use of the first order (linear) economic weights or a derived linear index, using previously described methods, will give very close to optimum economic selection responses. Examples from the literature indicate that severe losses of potential economic gain can possibly occur through use of a constrained index. It is concluded that constrained indexes should be avoided for economic genetic selection.     

New thermal stress test to assess the viability of cryopreserved boar sperm.

A new, rapid, thermal stress test for assessing the viability of boar semen, requiring only 45 min of incubation at 42.5 degrees C, was developed and compared with a widely used stress test of 180 min incubation at 37 degrees C. The shorter procedure was found to have the same discriminatory ability as the standard test in assessing the effects of freezing conditions on the percentage of spermatozoa remaining motile. Neither test was able to show differences in the kinetic rating of motile sperm after freezing in relation to the glycerol concentration present during freezing. However, the new test had a greater ability to distinguish the effects of different concentrations of glycerol, over the range of 0 to 6%, and to reveal different degrees of acrosomal damage sustained during freezing. The longer procedure was unable to distinguish among glycerol concentrations from 0 to 4% with respect to acrosomal damage and produced an overall lower proportion of sperm having a normal apical ridge. The new thermal stress test thus has the advantages of greater sensitivity and more rapid execution over the test hitherto in widespread use.     

辽宁老秃顶子保护区野猪冬季觅食地生境选择

2009年11月—2010年3月对辽宁老秃顶子国家级自然保护区野猪冬季觅食地生境选择进行了研究,同时调查了觅食地样方中的14个生态因子(植被类型、海拔高度、坡位、坡向等),运用痕迹检验法和主成分分析方法,对野猪的觅食地进行了分析。结果表明:野猪喜欢选择在食物丰富、人为干扰较小、距水源较近、隐蔽程度较高、坡度较平缓的阳坡活动,在没有或者很少有倒木、树桩和大块山石的地方活动觅食;对其冬季觅食地生境选择影响最大的5个因子分别是人为干扰、水源、食物、隐蔽性和灌木,其贡献率分别为19.45%、14.04%、13.03%、12.19%和10.37%。     

黄泥河自然保护区野猪冬季栖息地利用

2009年11月-2010年1月,根据野猪的生物学特征和黄泥河自然保护区的地形、地貌特点,在研究地区布设47条样线,对保护区的野猪冬季栖息地利用进行了研究,测定了野猪对海拔、坡位、坡向、坡度、植被类型、郁闭度、树高度、树胸径、食物丰富度、隐蔽度、离水源距离和离人为干扰距离等12种生态因子的选择利用情况.结果表明:黄泥河自然保护区野猪冬季多活动在海拔≤1000 m,坡下位的阳坡平坦地带,食物丰富度高,隐蔽度强,郁闭度中等,且离水源≤500 m,离人为干扰>2000 m的阔叶林和针阔混交林内;主成分分析表明,栖息地变量前4个特征值的累积贡献率达到77.5%,较好地反应了野猪的栖息地特征;影响野猪栖息地选择的关键因子是海拔、坡度、离人为干扰距离,次要因子是离水源距离、隐蔽度、树胸径.