Breeding Gilts Research Articles

Purchasing policy, quarantine and acclimation practices of breeding gilts in Belgian pig farms

BackgroundThe breeding population is very important in pig herds, for productivity, health and profitability. Replacement of breeding animals can be accomplished by own rearing of breeding gilts or by purchasing them. Purchasing breeding gilts is a hazardous event in terms of biosecurity and introduction of pathogens into a farm. However, in literature, little is known about gilt introduction in a herd. The present study investigated the introduction procedures of purchased breeding gilts in Belgian pig herds, and the compliance of these herds to the optimal introduction procedures. A questionnaire consisting of twenty questions related to farm characteristics (n = 2), purchasing policy (n = 6), quarantine period (n = 5), and acclimation practices (n = 7) was designed, and 68 farms completed the questionnaire during an on-farm interview.ResultsThe median (min. – max.) number of sows on the farms was 300 (85–2500). Fifty-seven per cent of the farms purchased breeding gilts, and there was a lot of variation in the frequency of purchase and the age at which gilts are purchased. On 95 % of those farms, a quarantine unit was used, and on most of these farms the quarantine was located on the farm itself (internal quarantine). The median (min. – max.) duration of the quarantine period was 42 (14–140) days. The most common acclimation practice was vaccination against Porcine parvovirus (96 %) and Erysipelothrix rhusiopathiae (94 %), although in some farms exposure of gilts to farm-specific micro-organisms was done by providing faeces from suckling piglets (18 %) and bringing gilts in contact with sows that will be culled (16 %). Only 10 % of the farms complied with the optimal introduction procedures, i.e. purchasing policy, quarantine building and quarantine management.ConclusionsThis study showed that in many farms, practices related to purchasing, quarantine and acclimation could be improved to maintain optimal biosecurity.

Using the Biocheck.UGent\u2122 scoring tool in Irish farrow-to-finish pig farms: assessing biosecurity and its relation to productive performance

BackgroundBiosecurity is one of the main factors affecting disease occurrence and antimicrobial use, and it is associated with performance in pig production. However, the importance of specific measures could vary depending on the (national) context. The aim of this study was to describe the biosecurity status in a cohort of Irish pig farms, to investigate which of those biosecurity aspects are more relevant by using the Biocheck.UGent™ scoring system, and to study the impact of such aspects on farm performance.ResultsExternal biosecurity score was high compared to most countries due to the characteristics of the Irish pig sector (i.e. purchasing only semen and breeding gilts on farm). The internal biosecurity score was lower and had greater variability among farms than other EU countries. Using multivariable linear regression, the biosecurity practices explained 8, 23, and 16% of variability in piglet mortality, finisher mortality, and average daily gain, respectively. Three clusters of farms were defined based on their biosecurity scores (0 to 100) using principal components and hierarchical clustering analysis. Scores for clusters 1, 2 and 3 were (mean ± SD) 38 ± 7.6, 61 ± 7.0 and 66 ± 9.8 for internal and 73 ± 5.1, 74 ± 5.3 and 86 ± 4.5 for external biosecurity. Cluster 3 had lower piglet mortality (P = 0.022) and higher average daily gain (P = 0.037) when compared to cluster 2.ConclusionsIrish farms follow European tendencies with internal biosecurity posing as the biggest liability. Our results suggest that practices related to the environment and region, feed, water and equipment supply, and the management of the different stages, need to be addressed in lower performing farms to improve productive performance. Further studies on the economic impact of these biosecurity practices including complementary data on herd health, gilt rearing, piglet management, vaccination and feeding strategies are needed.

Changes in body weight and fatness of sows during reproductive activity depending on LEPR and MC4R genes polymorphism

The use of genetic markers in selection of maternal breed gilts for reduced feed intake and fatness of pigs, may impact on their reproductive performance in subsequent breeding. The objective of the study was to analyse changes, over three consecutive lactations, in condition (body weight and fatness) and reproductive performance of Polish Large White (PLW) and Polish Landrace (PL) sows of known genotype at leptin receptor (LEPR) and melanocortin 4 receptor (MC4R) loci. The study involved 58 PLW and 65 PL gilts. Gilts and subsequently sows were monitored for body weight (BW) and backfat thickness (P2) over three reproductive cycles, and their litters were analysed for the number and body weight of the piglets. A total of 168 litters of PLW pigs and 186 litters of PL pigs were evaluated. It is concluded that over the three reproductive cycles, PLW sows exhibited higher weight gains and lower fatness compared to PL sows. The interaction between LEPR and MC4R genes had a significant effect on changes in body weight of the gilts, subsequently on changes in the condition of sows (BW and P2) during consecutive reproductive cycles, and on the average weight of piglets born. Heterozygous sows of LEPRAB/MC4RAG genotype were characterized during that time by the highest weight gains and backfat thickness at P2, and their the piglets born had low birth weight. Over the three reproductive cycles, sows of LEPRAA/MC4RGG and LEPRAB/MC4RGG genotypes produced piglets with significantly higher birth weight compared to sows of LEPRAB/MC4RAG, LEPRBB/MC4RAA and LEPRBB/MC4RGG genotypes.

Comparison of methods to assess fear of humans in commercial breeding gilts and sows

The aim of this study was to compare three behavioural tests to assess fear of humans in breeding gilts and sows in a commercial setting. Two hundred and thirty-two crossbred gilts and sows were studied and the tests were: HAT, behavioural response of sows individually held in an arena to a stationary experimenter (n=232); HTA, behavioural response of sows in a group pen to an approaching experimenter (n=232); HTW, behavioural response of sows in a farrowing crate to an approaching experimenter (n=116). The validated HAT has been used extensively in research to assess fear of humans in pigs and it has been consistently shown that handling treatments designed to differentially affect the pigs' fear of humans produced the expected variations in the approach behaviour of pigs to a stationary experimenter. However, the HAT is impractical for regular on-farm assessment of fear as it involves moving animals individually to an empty pen and is time consuming. There is no evidence in the literature of a well-validated practical test to assess fear of humans in sows in commercial settings and therefore the validity of the HTA and the HTW was investigated by examining their relationship with the HAT. A principal component (PCA) analysis was conducted on each data set for the HAT and HTA to identify a small set of factors for each test that represents the underlying relationships between the variables in each test. For each test a single ‘factor’ (Factor1HAT and Factor2HTA) was identified that provided an appropriate summary of the data. Only three behavioural variables were measured for the HTW, and as such were not suitable for PCA and therefore were treated individually. Spearman rank correlations were used to investigate the relationships between Factor1HAT and both Factor2HTA and the HTW variables. The effects of group, parity, time of day, test order in the HAT or HTA, test order in the penand experimenter on Factor1HAT, Factor2HTA and the three HTW variables were also studied. A low but significant correlation was found between the HTW and the HAT score (r=0.24, P=0.02), while a moderate significant correlation was found between the HAT and HTA scores (r=0.37, P<0.01). These relationships suggest that the HTA has reasonable validity; however, further research is required to modify the HTA in order to improve its validity while maintaining its feasibility.

Quantitative-genetic analysis of intensity growth of gilts fertile breed and their hybrids in the nucleus farm

The paper analyzes the 2760 gilts four different genotypes, two of which are pure bred Landrace (429 gilts) and Yorkshire (421 gilts) and two hybrid F1(YxL) (999 gilts) and F1(LxY) (911 gilts), tested in the period from 2010 to 2011.Analyzed by the following traits of intensity growth: weight at weaning (WW), daily gain at suckling (DGS), weight in rearing (WR), daily gain at rearing (DGR), weight in test (WT), daily gain on test (DGT), weight of gilts (WG) and life gain (LG). Due to the manifestation of heterosis effect, hybrid gilts in rearing made any higher body weight of about 3 kg, while the age of 160 days on average had a higher body weight by 7.0 kg compared to the pure breed gilts, which resulted in higher daily gain in different phases of rearing. Degree of heritability for analysis traits of intensity growth is of medium to high. Heritability (h2) for daily gains were larger (0.640 for DGS, 0.858 for DGR and 0.859 for DGT) in relation to the heritability for achieved body weight (0.584 for WW, 0.558 for WR and 0.816 for WT) in different phases of rearing. Between the most observed traits were found positive genetic and phenotypic correlations. The negative correlation found between WR, DGR and WT, DGT (rg= -0.055 to -0.108; rp = -0.010 to - 0.033), between WW, DGS and DGR (rg= -0.301 respectively -0.466; rp = -0.234 respectively -0.271).

Growth intensity of the fertile breed gilts in the nucleus pig farm

Production in the farm directly depends on the quality of gilts. For this reason it would be necessary to replace non-productive sows. By monitoring and control of the growth intensity in the performance test make possibility to provide selection effect and get gilts adequate age and weight at insemination. The present paper analyses of growth traits from birth until the end of the performance test. The investigations included 205 gilts, of which 104 Landrace and 101 Yorkshire, which were obtained from 7 sires (4 of Landrace and 3 of Yorkshire breed). The gilts that had a smaller weight at birth, showed a smaller daily gain and body weight realized at the end of the test. Lactation duration of 32 days, weight at weaning was not less than 7 kg. During the test of 85 days, the realized average weight was 76 kg, with a gain of 0.90 kg for Landrace gilts, while Yorkshire had smaller one (71 kg) and so smaller daily gain (0.84 kg). With an average age of gilts of 160 days, Landrace gilts reached weight 108 kg, with an average life gain of 0.67 kg, while the Yorkshire gilts reached weight of 101 kg, with an average life gain of 0.62 kg. Tests of significance showed that the sire, breed and weight at birth have a highly significant impact on most of the observed traits and represent a significant source of phenotypic variability in growth traits of tested gilts.

The combined effects of transport and food and water deprivation on the physiology of breeding age gilts

The objective of this study was to evaluate the effects of a 6, 12, 18, 24, or 30h transport period on the physiology and reproductive success of breeding age gilts, simulating transport of breeding gilts from one farm to a commercial breeding herd. Fifty gilts were allocated to one of five transport (TRANS) treatment groups; transported for 6, 12, 18, 24, or 30h. Fifteen gilts were allocated to one of five control (CON) treatments; gilts remained in their home pen for 6, 12, 18, 24, or 30h. Every 6h, gilts from one TRANS treatment were removed from the trailer. Blood samples were collected from gilts and their respective controls before and after transport. Gilts were then bred after puberty. The granulocyte to lymphocyte ratio (P<0.05) and cortisol concentrations (P<0.07) were greater in TRANS compared with CON gilts after a 6 and 12h transport period. Albumin concentrations were greater (P<0.001) in transported gilts after an 18 and 30h transport period compared with CON gilts. Blood urea nitrogen, glucose, and total protein concentrations were greater (P<0.05) in transported gilts compared with controls, regardless of the transport period. Reproductive performance measures did not differ (P>0.05) among treatments regardless of the length of transport duration. These data indicate that gilts transported for a period of up to 30h experienced initial acute stress during the first 6 to 12h and changes in water homeostasis throughout the 30h journey due to dehydration, food deprivation, and transport, however reproductive measures suggest that the long-term homeostasis of the gilts in this study were not significantly compromised. Transport of breeding gilts induced acute, transient stress but did not negatively impact reproductive performance. Interestingly, gilts were more at risk of physiological perturbations when transported 6h or less than 12 to 30h.

Effect of breeding strategy and feeding system on the within-herd variation of lean meat percents in Danish slaughter pigs

In several countries slaughter pigs are paid for individually, according to slaughter weight and lean meat percent (LMP). Production of uniform batches of pigs within the optimal weight and LMP limits will obtain the best price. Therefore, all pigs should have a similar growth rate (average daily gain, ADG) and reach an appropriate slaughter weight within the same time period. LMP may serve as a proxy for ADG since pigs with low LMP have significantly higher ADG than pigs with high LMP and vice versa. Both breeding strategy and feeding system may influence the range of variation among pigs. The aim of this study was to test the two following hypotheses: (1) Herds purchasing breeding gilts have a higher mean value and a lower variation (standard deviation) in LMP than herds producing their own breeding gilts and (2) Herds using restricted feeding of finishers have a higher mean value and a lower variation (standard deviation) in LMP than herds with ad libitum feeding of finishers. The study included 72 herds and a total of 345,132 pigs slaughtered during one year. Among the 72 herds, 40 were home-breeders and 32 purchased breeding gilts from a breeding company. Nineteen herds used restricted feeding, of which 8 (42%) were home-breeders. Fifty-three herds used ad libitum feeding, of which 32 (60%) were home-breeders. Breeding strategy had a significant effect on SDLMP ( p = 0.003), where purchase of breeding gilts resulted in a significantly lower standard deviation of the monthly LMP compared to home-bred gilts (a difference in median SDLMP of 0.2 percentage points or 8% difference between groups). Feeding system had a significant effect on the meanLMP ( p < 0.001), with a significantly higher meanLMP in herds using restrictive feeding compared to ad libitum feeding (60.7% versus 60.0%). Restrictive feeding also resulted in a significantly lower SDLMP ( p < 0.001) compared to ad libitum feeding (2.2% versus 2.5% or a 12% difference between groups).

Immune Cell Population in Oviducts in Relation to Ovarian and Progesterone Status of Anoestrous and Repeat Breeding Gilts

Immune Cell Population in Oviducts in Relation to Ovarian and Progesterone Status of Anoestrous and Repeat Breeding Gilts

Beziehung zwischen mittels Dualenergie-Röntgenabsorptiometrie bestimmter Körperzusammensetzung und Fruchtbarkeit von Jungsauen

Abstract. Title of the paper: Relationship between body composition measured by dual energy x-ray absorptiometry and reproduction performance in gilts This study was conducted to evaluate the relationship between body composition and reproduction traits in gilts. A number of 176 gilts of different genotypes were categorized in three different groups. Group 0 consists of gilts that were disqualified for breeding according performance test results or showed no occurrence of oestrus. Group 1 consists of all gilts, which farrowed after an artificially insemination. Group 2 was composed of gilts that were artificially inseminated but did not give birth to a litter. Body composition was determined in vivo using dual energy x-ray absorptiometry at a live weight of about 90 kg. Initial reproduction data from group 1 were also evaluated. Results of the performance test showed considerable variation among the different groups. Group 1 was significantly heavier and the daily gain was significantly higher than in group 0. However, results of breeding index and value were clearly below the results of the other two groups. The body fat content was significantly higher in gilts with a litter (&gt;1.65 absolutely) than in gilts without a litter (group 2) and in disqualified gilts (group 0). Group 2 gilts showed the smallest body fat mass. However, the relation between DXA fat percentage and litter size for group 1 showed in tendency that the litter size might decrease with an increasing fat content of gilts. Therefore, an optimum body fat content for conventional breeding gilts of European or American origin needs to be determined for a maximum fertility.

Improved Reproductive Efficiency in Gilts by Intrauterine Infusion of Killed Boar Semen before Breeding

Two separate trials were conducted to determine the effects of uterine priming prior to first breeding and quantify any changes in the reproductive efficiency of gilts. In trial I twelve (12) gilts were randomly assigned to 3 treatments:T1:infusion of distilled water (control), T2: single infusion of killed semen (KS1), and T3: double infusion of killed semen (KS2). Each treatment had 4 breeding gilts which were bred by natural insemination (NI). In trial II, another set of 12 breeding gilts were randomly allotted to the same treatments and were subsequently bred by artificial insemination (AI). Infusions, through the use of AI catheters, were done during the 2 nd estrous cycle for T1 and T2, whereas infusions for T3 were made during the 1 st and 2 nd cycles. Regular breeding was subsequently made during the 3 rd estrous cycle. All gilts that returned to cycle were rebred within the 30-day period. In trial I (natural breeding), total piglets born was higher (p<0.05) in T2 (12.75 piglets) and T3 (11.75 piglets) than in the control (10.5 piglets). T3 obtained the highest (p<0.05) litter size (10.25 piglets) and heaviest litter weight (74.12 kg) at 28 days weaning, followed by T2 (9.80 piglets and 65.0 kg, respectively). The control yielded the lowest (p<0.05) litter size (7.50) and the lightest litter weight (47.00 kg) at weaning. For Trial II gilts (artificially inseminated), T3 gave higher (p<0.05) litter size born alive (10.88 piglets), total piglets born (11.72 piglets) and live litter weight at birth (15.30 kg) than those of T2 and the control. These results indicate that prebreeding intrauterine infusion of killed boar semen, either single or double, improved the reproductive performance of gilts. (Asian-Aust. J. Anim. Sci. 2006. Vol 19, No. 6 : 789-792)

Eradication of Aujeszky's disease from a large-scale pig farm

Eradication of Aujeszky's disease from a large-scale pig farm by the 'test-and-cull' eradication procedure based on the use of gene-deleted vaccines and serological monitoring using gE ELISA is described. Aujeszky's disease free status was successfully achieved on a farrow-to-finish type farm characterised by three difficulties interfering with the success of eradication: (i) weaned (30-day-old) piglets remained in the farrowing house until 65 days of age; (ii) the farm did not use nursery rearing; (iii) fatteners were kept together with the breeding gilts. Thus, the immunisation programme had to be adjusted to the management technology used on the farm, and by regular serological monitoring it had to be periodically modified to make it suitable for attaining the goals. This meant that breeding animal candidates of a wide age range and kept in the same air space had to be provided with a continuously high-level immunity by regular vaccination sufficient even for rectifying potential human errors. The immunisation programme was designed by taking into consideration the disappearance of maternal immunity, and a strict vaccination programme was applied during the rearing of breeding gilts kept together with the fattening pigs. Frequent immunisation applied during the rearing of the own breeding animal replacements proved to be of decisive importance for the eradication of Aujeszky's disease from the entire herd. In addition to the accurate implementation of the vaccination programme, regular serological monitoring also made a major contribution to the success of eradication.

The effect of modified eros centre, outdoor raising or conventional group housing on breeding gilts and its effects on reproductive performance over four parities

The present study was conducted in a large Croatian “built up unit”. The objective of the study was to determine if an indoor modified eros centre (MEC) compared to indoor or outdoor group housing of gilts, influenced the onset of puberty of gilts and the reproductive performance of the evaluated females ( n=783) over four parities. The gilts were from the same nucleus herd. Gilts of same age (140–150 days of age), body condition (body condition score of 3–4) and similar genetics (four-way cross females), during the same season (January to April 1999), were randomly divided at arrival into three groups and treated as follows: • MEC gilts ( n=279): These were placed into indoor MEC pens in groups of 8–10. The gilts had continuous fenceline contact to boars (one boar to two groups of gilts, boars were changed daily) and to shortly weaned oestrous sows. Gilts were regrouped and dislocated at 10-day intervals. • Outdoor gilts ( n=263): These were kept in groups of 8–10 on a large pasture (80–100 m 2 per group). The animals had fenceline contact to mature boar for 5–10 min daily. • Control indoor gilts ( n=241): These were housed indoors in large pens in groups of 8–10. The animals had fenceline contact to mature boars for 5–10 min daily. Each outdoor group had an insulated hut with straw bedding. All gilts were fed ad libitum with the same commercial diet. Housing gilts in MEC resulted in earlier ( P<0.001) onset of estrus (MEC: 174.8±2.4 days, indoor group housing: 207.6±4.1 days, outdoor group housing: 187.4±2.1 days) and lower ( P<0.001) farrowing rate to first service (MEC: 70.97%, indoor group housing: 89.73%, outdoor group housing: 89.62%). Farrowing rate of regularly returning MEC gilts to second service was 95.00%. First total-born litter size, first liveborn litter size, first wean-to-estrus interval (WEI), percent of sows bred after first weaning, second total-born litter size, second liveborn litter size, average third and fourth total-born and liveborn litter size, number of sows having four litters, number of litters per sow, total number of pigs per sow, total number of liveborn pigs per sow showed no significant differences between the groups. More ( P<0.05) sows were culled in outdoor group. Compared to MEC and outdoor housing, indoor housed sows suffered higher ( P<0.05) percentage of anoestrus.

Individual differences in behaviour, physiology and pathology in breeding gilts housed in groups or stalls

A number of studies in young pigs have demonstrated a relation between a variety of behavioural and physiological features and the degree of resistance displayed early in life in a so-called “backtest”. The current study aimed at investigating the relation between the backtest response and the development of stereotypies, the circadian rhythm of cortisol, the heart rate response to feeding, and pathological lesions of heart, lungs and stomach of adult breeding gilts. At 10 and 17 days of age, female piglets were subjected to the backtest. In this test, each piglet is restrained on its back for 1 min and the number of escape attempts is scored. Pigs classified as high-resisting (HR, n=36) or low-resisting (LR, n=36) were selected and housed in groups of six (3 HR, 3 LR). At 7 months of age, half of the groups were housed in individual stalls. Time spent chain biting by stall-housed gilts during 2 h after afternoon feeding was studied at regular intervals for 21 weeks. At 11 months of age, saliva was collected from all animals every hour during 24 h for cortisol analysis. At 8 and at 12 months of age, heart rate of all animals was measured around afternoon feeding. Pigs were slaughtered at 14 months of age and heart, lungs and stomach were macroscopically examined. Over time, stall-housed HR gilts tended to show more chain biting, had lower circadian cortisol concentrations and showed a diminished heart rate response to feed delivery compared to LR gilts. In group-housed gilts, the circadian rhythm of cortisol and the heart rate response to feed delivery did not relate to the backtest response. Stall-housed gilts had lower circadian cortisol concentrations than group-housed gilts. The prevalence of pathological lesions was not influenced by backtest type. Stomach wall damage was more severe in stall-housed than in group-housed gilts.

Individual differences in aggression and physiology in peri-pubertal breeding gilts

Several recent studies on pigs have demonstrated a relationship between the degree of resistance displayed in a so-called “backtest” and a variety of behavioural and physiological responses in piglets and young fattening pigs. However, the discussion about the predictive power of the backtest is still going on . This study aimed at investigating the relationship between the backtest response and behaviour and physiology in peri-pubertal, i.e. nulliparous breeding gilts. During the suckling period gilts were subjected to the backtest. Piglets classified as low resisting (LR, n=36) and high resisting (HR, n=36) were selected. At 20 weeks of age they were housed in groups of six (three HR, three LR). Between 23 and 29 weeks of age, behaviour and physiology under undisturbed conditions were measured. At 26 weeks of age, LR pigs showed higher baseline salivary cortisol levels during the light period than HR pigs. However, HR and LR gilts did not differ in weight gain, aggression and heart rate response to afternoon feeding. This study indicates that when breeding gilts are kept in groups containing both HR and LR animals, aggression and heart rate reactivity under undisturbed conditions do not relate to the backtest response.

Evaluation of maternal and piglet influences on performance of Meishan synthetic and European White breeds of pig during lactation

Meishan synthetic sows and gilts have been shown to produce higher litter weights at weaning than White breed type sows and gilts (Sinclair et al. 1995). The explanation for increased litter weight weaned could be attributed to one of three areas: (1) The M sows are inherently better mothers than W and can support a higher level of piglet production. (2) The higher piglet production could be solely a result of hybrid vigour in the cross-bred piglets. (3) The increased litter production could be primarily attributed to a higher number of piglets born and reared by M. This experiment aimed to evaluate the maternal post-natal effects by standardising litters between breeds by cross-fostering techniques.Sixty-four 3rd parity sows were used in a 2x2x2 factorial experiment to assess the influence of maternal breed type (Meishan synthetic 50% [M] or pure-bred European Landrace and Large White [W]), litter size (8 [L] or 12 [H] piglets) and breed of piglet (25% Meishan hybrid [m] or white hybrid [w]) on sow and litter production over a 28 day lactation. All litters were formed by cross-fostering 24hrs after farrowing.

The Influence of Fatness and Fat Change on the Performance of Breeding Gilts

Weight gains can occur with substantial fat losses and therefore liveweight change is unlikely to form the basis of feeding strategies, whereas the fatness of the animal may be a more appropriate criterion. Eighty Large White x Landrace gilts were first mated at 123.5 kg ± 1.54 with a P2 of 14.5 mm ± 0.24 [Meritronics] and 12.7 mm ± 0.19 (Vetscan]. Half these gilts were fed to be fat [F] at parturition [target 20-24 mm P2) and half were fed to be thin [T] [target 10-14 mm P2). F gilts consumed more feed during pregnancy and gained more weight and backfat than T gilts [all differences between the 2 treatments were significant P˂0.001). The number of piglets born and the number of live births were not affected by feeding gilts to be fat or thin, but fat gilts produced significantly heavier piglets. After parturition, half of both F and T gilts were offered either 7 kg of food per day [H] or 3 kg per day [L] and half were sucked by litters of 5 piglets and half by litters of 10 piglets during a 28 day lactation. Piglets were not given creep feed. Fatness of the gilts at parturition, feed level during lactation and sucking litter size all significantly influenced both the absolute and the change in liveweight and backfat from farrowing to weaning. Weight and P2 changes are shown in Figures 1 and 2. The performance of the litter was also significantly affected by the fatness of the gilt at parturition and by the number of piglets sucking. Results for each treatment group are given in Table 1. Animals offered the high level of feed during lactation had a significantly shorter interval between weaning and conception. There were also positive relationships between readiness to rebreed and absolute liveweight and absolute fatness.

Efficacy of Guardian 10% Swine Ear Tags for Control of Hog Lice, 1985

Abstract Guardian 10% swine ear tags were evaluated for hog lice control when applied to brood sows and gilts in Page Co, VA. The following treatment groups were established on 3 Mar: A) untreated control, consisting of 6 mixed breed gilts; each gilt received 2 Allflex identification tags; B) Guardian 10% ear tags, attached to the inside of ears (one per ear), consisting of 12 mixed breed gilts; C) Guardian 10% ear tags, attached to the outside of ears (one per ear), consisting of 7 mixed breed sows. Six animals from each group were individually identified and used for evaluation. Each group was confined separately in pens in a breeding and gestation barn. However, each group had access to a common self-feeder, which they used on a rotational basis. Each group was allowed to feed for a 24-h period, and then return to their holding pen for a 48-h period. An alternate untreated control group (D), consisting of 8 mixed-breed sows with Allflex identification tags, was established in the same location on 2 May. This group, of which 6 were used for evaluation, had no access to the self-feeder. This alternate control group was established because there was a concern that the original control animals were subject to contamination with insecticide from the treated animals through the rotational use of the self-feeder.

The incidence of, and factors associated with, failure to mate by 245 days of age in the gilt

The incidence of, and factors associated with, gilts failing to mate between 29 and 35 weeks of age were studied over 12 months at a large intensive piggery in southern Australia. After excluding gilts culled as physically unsound, 10.5% of the remaining 2484 gilts failed to mate and were slaughtered. Seventy percent of unmated gilts had ovulated, and of these, 54% had shown negative or low responses to the back-pressure test (BPT) and 16% had shown moderate or high responses. Few prepubertal gilts (1%) had abnormal reproductive tracts. When group size was greater than 50 gilts (< 0.9 m 2/gilt) immediately prior to mating (27–28 weeks of age), there was a higher incidence of unmated gilts and an increase in the proportion of unmated gilts which had shown negative or low BPT response than when groups were less than 50 gilts (12.9 vs. 8.6%, P < 0.001; and 8.0 vs. 3.6%, P < 0.001, respectively). The incidence of prepubertal gilts at 35 weeks was lower during spring than other seasons (1.48 and 3.36%, P < 0.05) and higher during summer than other seasons (4.61 and 2.37%, P < 0.01). Fewer Large White gilts remained unmated at 35 weeks of age than Landrace or Large White-Landrace synthetic breed gilts (7.7 and 14.1% of those selected, P < 0.001). More purebred gilts were prepubertal at 35 weeks of age than crossbred gilts (5.4 and 2.4%, P < 0.01).

Livestock judges: How much information can an expert use?

The number of dimensions used by expert livestock judges in making decisions was determined by two different experimental procedures. In the first, judgments were made of hypothetical gilts (female breeding pigs) described by verbal statements along 11 relevant dimensions. In the second, judgments were made based on photographs of Poland-China breeding gilts. The judges were found to use 9–11 pieces of information in the first study but were generally found to use fewer than three in the second. These results were interpreted to indicate that expert judges can integrate a large number of dimensions but that intercorrelations present in real stimuli tend to reduce the number of dimensions found. This suggests that experts may be able to use substantially more information than was previously thought.