Monitoring chromosome mutations in large-scale breeding operations

The frequency of chromosomal aberrations and exchanges of sister chromatids (SCEs) in peripheral lymphocytes was studied in 65 pigs from five large breeding herds. Four groups comprised fattened pigs and the fifth group consisted of sows from a large multiplier breeding herd. During the investigation, the dust from the sites was analyzed for the presence of zinc, lead, cadmium, mercury, aflatoxin B1, PCB, DDT, and lindane. The average frequency of aberrant cells (AB.B) in the pigs of group I was 3.85 +/- 1.60%, in group II 2.10 +/- 1.52%, in group III 5.01 +/- 2.1%, in group IV 3.50 +/- 1.58%, and in group V 6.20 +/- 3.21%. The cytogenetic finding corresponded to the differences in the amount of foreign substances found in the dust on the premises where the animals of all groups were kept. The average frequency of the SCEs was 7.00 +/- 1.10 (I), 6.51 +/- 0.89 (II), 6.92 +/- 0.72 (III), 7.10 +/- 0.85 (IV) and 7.06 +/- 1.47 (V) per one cell. Statistically significant differences in the numbers of AB.B. were recorded between groups II and I, II and IV, I and III, IV and V (p less than 0.05) and between groups II and III, II and V (p less than 0.01). There was no statistically significant difference in the frequency of SCEs. The determination of the frequency of chromosomal aberrations can be used for the hygienic control of the degree of exposure of pigs to mutagens.     

Effect of castration on plasma luteinizing hormone concentrations in prepubertal boars

Mean concentrations and the occurrence of pulsatile release of luteinizing hormone (LH) were determined in 14-wk-old crossbred boars (50.5 +/- 1.5 kg) after bilateral or unilateral castration at 10 wk of age. Blood was collected at 10-min intervals for 5 h. Then gonadotropin releasing hormone (GnRH; 40 micrograms) was given and sampling was continued at 5-min intervals for 1 h. Compared with intact boars, bilateral castration increased (P less than .001) mean LH (982 +/- 56 vs 389 +/- 56 pg/ml), pulsatile releases of LH (7.0 +/- .6 vs 2.0 +/- .6 pulses/5 h) and LH pulse amplitude (617 +/- 29 vs 360 +/- 58 pg/ml). Unilaterally castrated boars did not differ from intact boars in any of the above measures of LH secretion. Testis weight increased more between 10 and 14 wk of age in the unilateral castrates than in the intact boars (432 +/- 42 vs 245 +/- 34%; P less than .05). Thus, compensatory hypertrophy occurred within 4 wk of castration. Plasma testosterone was lower for bilateral castrates than for intact animals (.1 +/- .8 vs 3.6 +/- .9 ng/ml; P less than .05) while unilateral castrates (3.8 +/- 1.0 ng/ml) and intact boars did not differ. Plasma estradiol concentrations in bilateral and unilateral castrates were not different from levels found in intact boars (1.8 +/- 1.8, 8.8 +/- 2.1 and 6.0 +/- 1.8 pg/ml, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Semen characteristics and libido in boars treated repeatedly with PGF2alpha

The objective was to determine the effects of repeated injections of PGF2alpha (Lutalyse; Pfizer) on semen and libido characteristics in terminal-line boars. Semen was collected once weekly from wk 0 to 15 and on four consecutive days during wk 16. Boars received an i.m. injection of 10 mg of PGF2alpha (n = 11) or 2 mL of vehicle (n = 11) immediately before entering the collection room. For the weekly collections, semen volume (220.3 +/- 3.2 mL; mean +/- SE), gel weight (38.7 +/- 0.7 g), total sperm cells (65.4 +/- 1.2 billion), motile sperm cells (67.4 +/- 0.6 %), and sperm velocity (125.9 +/- 1.2 microm/s), were affected by time (P < 0.01) but not by treatment (P > 0.10). Sperm concentration (0.31 +/- 0.01 billion/mL) was not affected (P > 0.10) by time or treatment. The percentage of morphologically normal sperm cells, assessed at wk 16, did not differ (P = 0.39) between groups (80.8 +/- 1.0). Libido was evaluated from wk 0 to 16. There were no effects of treatment or time (P > 0.10) on the period from injection to the start of ejaculation (225.6 +/- 9.1 s). Duration of ejaculation was affected by treatment (P < 0.01; 472.0 +/- 43.1 s and 280.4 +/- 43.1 s, for PGF2alpha-treated and control boars, respectively) and time (P < 0.01). During the intensive collection period (wk 16), semen volume (200.1 +/- 7.1 mL), gel weight (39.2 +/- 1.5 g), sperm concentration (0.19 +/- 0.01 billion/ mL), total sperm cells (39.5 +/- 3.6 billion), motile sperm cells (65.6 +/- 2.2%), and sperm velocity (117.8 +/- 3.7 microm/ s) were affected by time (P < 0.10) but not by treatment (P > 0.10). The period from injection to the start of ejaculation tended to decrease (by 44%) during the intensive collection period in PGF2alpha-treated boars, but not in controls (treatment x time, P = 0.07). Regardless, the period from injection to the start of ejaculation did not differ (P = 0.63) between groups on d 4 of the intensive collection period. Duration of ejaculation was affected by treatment (P < 0.01; 459.1 +/- 24.1 s for PGF22alpha-treated boars vs. 303.1 +/- 24.1 s for controls) but not by time (P > 0.10). Overall, there were no exceptional positive or negative effects of long-term treatment with PGF2alpha on semen characteristics and libido in boars.     

The incidence of agglutination and its influence on sperm quality and fertility of boar semen

The aim of this study was to examine the incidence of sperm agglutinations and their relationships with sperm quality and fertility. Semen samples of 40 boars of an AI-station were investigated. Nineteen of the 40 investigated boars showed a constantly low (< 10% agglutinated sperm), 3 an intermediate (10-20%) and 6 boars a high level (> 20%) of agglutination in raw semen. The degree of agglutination in sperm samples of 12 boars varied distinctly during the investigation period. During summer more (P < 0.05) agglutinated sperm were observed (11.0 +/- 11.6%) than during winter (6.2 +/- 7.3%). There was no association between bacterial contamination and incidence of agglutinations (P > 0.05). After dilution in extender the percentage of agglutinated sperm decreased from 6.2 +/- 7.3% to 1.1 +/- 1.4% (P < 0.0001). Twenty-four hours after dilution the percentage of progressively motile sperm was 7.4% lower (P < 0.05) in ejaculates with an initially high degree of agglutination (> 20% agglutinated sperm) compared to samples with an initially low degree of agglutinated sperm (< 10%). Plasma membrane integrity, mitochondrial membrane potential, acrosome reaction and chromatin structure were independent (P > 0.05) from the level of agglutination. Fertility data did not differ (P > 0.05) between boars with low and high numbers of agglutinated sperm in raw semen. The results show that there are individual, ejaculatory and seasonal variations in the incidence and degree of agglutination. Agglutinations have a negative effect on motility of sperm and disappear to a large extent after dilution in sperm extender. They have no negative consequences on fertility.     

Administration of estradiol-17beta increases anterior pituitary IGF-I and relative amounts of serum and anterior pituitary IGF-binding proteins in barrows

Two experiments were conducted to determine whether 1) administration of estradiol-173 (E2) implants to barrows elevates serum concentrations of E2 to levels similar to those of adult boars and subsequently affects the anterior pituitary gland IGF system and 2) administration of E2 to barrows increases serum concentrations of E2, serum and anterior pituitary concentrations of IGF-I, and relative amounts of serum and anterior pituitary IGF-binding proteins (IGFBP), vs boars and unimplanted barrows. In Exp. 1, 20 crossbred barrows (150 +/- 6 d, 103 +/- 8 kg) were administered varying number of E2 implants (0, 2, 3, 4; n = 5/group) on d 1. Blood samples were collected weekly by jugular venipuncture, beginning on d 1. Pigs were killed on d 36 when a blood sample and anterior pituitary were collected. Serum concentrations of E2 were increased (P < 0.05) in pigs with 2,3, and 4 implants vs 0 implants, but no difference (P > 0.05) was detected in serum concentrations of E2 among pigs with 2, 3, and 4 implants. Orthogonal contrasts identified that three or four E2 implants were necessary to increase serum concentrations of E2 to that similar to boars. Serum and anterior pituitary concentrations of IGF-I were increased (P < 0.05) in pigs with 2, 3, and 4 implants vs 0 implants. Relative amounts of anterior pituitary IGFBP-2 and - 5 increased (P < 0.05) in response to administration of E2. In Exp. 2, three treatment groups were randomly allotted by litter; boars (n = 11), E2-implanted barrows (n = 9), and unimplanted barrows (n = 12). A blood sample was taken from all pigs on d 1 and every 14 d thereafter. Implanted pigs received four implants on d 1. Pigs were killed on d 91, when a blood sample and anterior pituitary were collected. Mean serum concentrations of E2 were greater (P < 0.05) in implanted pigs vs boars. Mean serum concentrations of IGF-I (ng/mL) were greater (P < 0.05) in boars (238.7 +/- 6.8) than in implanted barrows (170.2 +/- 8.9) and unimplanted (150.4 +/- 6.7) pigs and tended to be greater (P = 0.08) in implanted vs unimplanted pigs. Mean anterior pituitary concentrations of IGF-I (ng/mg tissue) were greater (P < 0.05) in implanted (773.6 +/- 57.0) pigs than boars (251.9 +/- 51.6) and unimplanted (185.6 +/- 49.4) pigs. Relative amounts of serum IGFBP-2 were greater (P < 0.05) in implanted pigs vs boars. Relative amounts of anterior pituitary IGFBP-2 and -5 were greater (P < 0.05) in boars than in implanted and unimplanted pigs. These data suggest that E2 may influence components of the porcine IGF system in the serum and anterior pituitary. Other gonadal factors present in boars may additionally affect the serum and anterior pituitary IGF system.     

Identification of pseudorabies virus-infected swine herds by evaluating the serostatus of boars or finishing pigs

Data were collected from 39 Minnesota swine farms quarantined for pseudorabies virus (PRV) infection. Each herd was serologically evaluated for antibodies to PRV in the sows, boars, and finishing pigs. To identify PRV-seropositive swine herds, the Kappa statistic was used to estimate the effectiveness of evaluating the PRV serostatus of boars or of finishing pigs. Using the serostatus of all herd boars, the sensitivity (with 95% confidence interval) of identifying PRV-infected herds was 58 +/- 22%, and the specificity was 100 +/- 0%; Kappa statistic was 0.55. Using the serostatus of a representative sample of finishing pigs, the sensitivity of identifying PRV-infected herds (with 95% confidence interval) was 63 +/- 22%, and specificity was 87 +/- 23%; Kappa statistic was 0.40. The PRV serostatus of herd boars or of a representative sample of finishing pigs did not accurately reflect the PRV serostatus of the herd.     

Serum concentrations of luteinizing hormone, growth hormone, testosterone, estradiol, and leptin in boars treated with n-methyl-D,L-aspartate

Three experiments were conducted to determine the effects of n-methyl-D,L-aspartate (NMA), an agonist of the excitatory amino acid glutamate, on secretion of hormones in boars. In Exp. 1, boars (185.0+/-.3 d of age; mean +/- SE) received i.v. injections of either 0, 1.25, 2.5, 5, or 10 mg of NMA/kg BW. There were no effects of NMA (P>.1) on secretion of LH and testosterone. Treatment with NMA, however, increased (P<.01) circulating GH concentrations in a dose-dependent manner. In Exp. 2, boars (401 d of age) received an i.v. challenge of NMA at a dose of 10 mg/kg BW or .9% saline. Treatment with NMA, but not saline (P>.1), increased serum concentrations of LH (P<.01), GH (P <.01), and testosterone (P<.06). In Exp. 3, boars that were 152, 221, or 336 d of age were treated i.v. with NMA (10 mg/kg BW). Across ages, treatment with NMA increased circulating concentrations of LH (P<.07) and testosterone (P<.01). However, NMA increased (P<.01) mean GH concentrations in only the oldest boars. Treatment with NMA had no effect (P>.1) on circulating concentrations of estradiol or leptin; however, estradiol concentrations increased (P<.03) with age. In summary, NMA increased secretion of LH, GH, and testosterone in boars. However, endocrine responses to treatment with NMA may be influenced by age of the animal. Finally, NMA did not influence circulating concentrations of estradiol or leptin.     

Effects of chronic gonadotropin-releasing hormone agonist treatment on serum luteinizing hormone and testosterone concentrations in boars.

Mature boars were subjected to chronic treatment with a gonadotropin-releasing hormone (GnRH) agonist, goserelin (D-Ser[But]6, Azgly-NH210), and serum luteinizing hormone (LH) and testosterone concentrations were measured. Ten sexually mature boars were randomly assigned to treatment (n = 5) or control (n = 5) groups. On day 0, boars were implanted sc (day 0) with 2 GnRH agonist implants (1 mg of GnRH/implant) or sham implants. Blood samples were collected at 12-hour intervals on days -2 and -1, at 6-hour intervals on days 0 through 4, and at 12-hour intervals on days 5 through 8. In addition, blood samples were collected at 15-minute intervals for 6 hours on days -1, 0, 4, and 8. Serum testosterone and LH concentrations were determined by radioimmunoassay. Maximal LH (7 +/- 1 ng/ml) and testosterone (26 +/- 3 ng/ml) concentrations were observed at 5 and 18 hours, respectively, after GnRH agonist treatment. Subsequently, LH and testosterone concentrations decreased to pretreatment values (0.3 +/- 0.1 ng/ml and 1.8 +/- 0.4 ng/ml, respectively) by 24 and 48 hours, respectively, after GnRH agonist implantation. Few differences in the characteristics of pulsatile LH release were observed between the groups. Testosterone and LH concentrations in samples collected at 6- and 12-hour intervals and pulsatile LH release did not change after sham treatment of control boars. Whereas previous reports indicated that chronic GnRH administration suppressed serum LH and testosterone concentrations in rams, rats, and dogs, our results indicate that chronic GnRH agonist treatment induced transitory increases, without subsequent suppression, in LH and testosterone concentrations in mature boars.     

Detection and duration of porcine reproductive and respiratory syndrome virus in semen, serum, peripheral blood mononuclear cells, and tissues from Yorkshire, Hampshire, and Landrace boars.

Because transmission of porcine reproductive and respiratory syndrome virus (PRRSV) can occur through boar semen, it is important to identify persistently infected boars. However, even for boars given the same PRRSV strain and dose, variability in the duration of viral shedding in semen has been observed, suggesting that host factors are involved in PRRSV persistence. To determine whether there are host genetic factors, particularly litter and breed differences related to the persistence of PRRSV, 3 litters from 3 purebred swine breeds were used for this study. It was also determined whether PRRSV could be detected for a longer period of time in serum, semen, or peripheral blood mononuclear cells (PBMC) and if PRRSV could still be detected in tissues after these antemortem specimens were PRRSV negative for a minimum of 2-3 weeks. Three Hampshire, 3 Yorkshire, and 2 Landrace PRRSV-naive boars were obtained and inoculated intranasally with a wild-type PRRSV isolate (SD-23983). All boars within each breed were from the same litter, and litters were within 9 days of age. Serum and PBMC were collected twice weekly from each boar and analyzed for the presence of PRRSV by virus isolation and the polymerase chain reaction (PCR). Serum was also used to obtain virus neutralization titers and enzyme-linked immunosorbent assay S/P values. Semen was collected twice weekly from 7 of 8 boars and analyzed by PCR. After all specimens were PRRSV negative for a minimum of 2-3 weeks, each boar was euthanized, and 21 tissues plus saliva, serum, feces, and urine were collected. All postmortem specimens were evaluated by virus isolation. Specimens that were PRRSV negative by virus isolation were then evaluated by PCR. The mean number of days (+/-SD) for the duration of PRRSV shedding in semen was 51+/-26.9 days, 7.5+/-4.9 days, and 28.3+/-17.5 days for Landrace, Yorkshire, and Hampshire boars, respectively. Because of small sample sizes and large SDs, the differences in duration of PRRSV shedding in semen between breeds were not considered significant. However, the trend suggested that Yorkshire boars were more resistant to PRRSV shedding in semen than were Landrace boars, requiring further investigation using a larger numbers of boars. PRRSV was detected for a longer period in semen than in serum or PBMC in 4 of 7 boars. Viremia could be detected for a longer period in serum than in PBMC in 6 of 8 boars. After a minimum of 2-3 weeks of PRRSV-negative serum, semen, and PBMC, PRRSV could still be detected in the tonsil of 3 of 8 boars by virus isolation, indicating that boars still harbor PRRSV within the tonsil even though antemortem specimens are PRRSV negative.     

Prevalence of chromosomal aberrations in breeding pigs in Spain

The main aim of this study was to document the prevalence of chromosomal aberrations found to date on the pig population in Spain, a country in which this production sector has a critical role, being the fourth country in the world in pig production and the second one within the European Union. The total number of animals studied was 849, and the founded frequency of carrier pigs with chromosomal alterations was 3.8%. When only the structural alterations were considered, the prevalence in males was 3.3%. This percentage is far from the 0.5% of carrier boars that has been estimated in France, a country where there is a systematic cytogenetic screening of future breeding pigs since 1992. In order to avoid the productive and economic losses caused by karyotype alterations in breeding pigs, it would be important to establish a cytogenetic screening of breeding animals at artificial insemination centres and genetic selection farms.     

Effect of ACTH and CRH on plasma levels of cortisol and prostaglandin F2alpha metabolite in cycling gilts and castrated boars

The present study was designed to evaluate the effects of synthetic ACTH (1-24, tetracosactid) and porcine CRH on the plasma levels of cortisol and PGF2alpha metabolite in cycling gilts (n = 3) and castrated boars (n = 3). The experiments were designed as crossover studies for each gender separately. Each animal received, during three consecutive days; 1) ACTH (Synacthen Depot) at a dose of 10 microg/kg body weight in 5 ml physiological saline, 2) porcine CRH at a dose 0.6 microg/kg body weight in 5 ml physiological saline or 3) physiological saline (5 ml). The test substances were administered via an indwelling jugular cannula in randomized order according to a Latin square. The administration of ACTH to cycling gilts resulted in concomitant elevations of cortisol and PGF2alpha metabolite with peak levels reached at 70.0 +/- 10.0 and 33.3 +/- 6.7 min, respectively. Similarly, the administration of ACTH to castrated boars resulted in concomitant elevation of cortisol and PGF2alpha metabolite with peak levels reached at 60.0 +/- 0.0 and 20.0 +/- 0.0 min, respectively. Cortisol peaked at 20 min after administration of CRH in both cycling gilts and castrated boars with maximum levels of 149.3 +/- 16.5 nmol/l and 138.3 +/- 10.1 nmol/l, respectively. It can be concluded that administration of synthetic ACTH (tetracosactid) to pigs caused a concomitant elevation of cortisol and PGF2alpha metabolite levels in both cycling gilts as well as castrated boars. The administration of CRH to pigs resulted in an elevation of cortisol levels in both cycling gilts and castrated boars. Conversely, PGF2alpha metabolite levels were not influenced by the administration of CRH either in cycling gilts or in castrated boars.     

Genetic parameter estimates for reproductive traits of male and female littermate swine

Reproductive traits of purebred and crossbred pigs produced in a four-breed diallel mating system using the Duroc, Landrace, Spotted and Yorkshire breeds were collected for five consecutive farrowing seasons (two farrowing seasons/year) beginning in fall 1976. Paternal half-sib heritabilities and genetic correlations for testicular traits (120 boars from 36 sires), serum testosterone (TE) and luteinizing hormone (LH) concentrations before and after treatment with gonadotropin releasing hormone (GnRH; 131 boars from 37 sires) and breeding performance traits (151 boars from 38 sires) were estimated. Heritability estimates were generally small to moderate except for sperm/gram testis (SGT), LH concentrations before (LHO) and at 3 h (LH3) after treatment with GnRH (.73 +/- .48, .61 +/- .46 and 1.19 +/- .45, respectively). A large positive genetic correlation was found for LHO with LH3 (.94 +/- .39), while a negative relationship existed for LH3 with TE concentrations at 3 h after GnRH injection. The genetic correlation between a boar's average first service conception rate and average conception rate also was significant (.82 +/- .54). Genetic correlations among littermate traits would suggest that selection for decreased age at puberty in gilts could cause an increase in LH concentrations in boar offspring, before and after GnRH injection, and may also have adverse effects on their ability to settle females. Selection for increased weight at puberty of gilts could cause TE concentrations of boar offspring to increase while having little effect on their breeding performance.     

Factors influencing semen characteristics in boars

Factors influencing semen characteristics in young boars reared in a subtropical environment were studied. Age had only a slight effect on semen volume, but had a significant effect on sperm concentration, total sperm in the ejaculate and daily sperm output (DSO), there being marked increase in boars over 12 months of age compared with younger boars. Boars aged between 8 and 12 months had a DSO of 8.1 +/- 2.6 X 10(9) compared with boars 13 to 15.5 months with a DSO of 14.3 +/- 3.9 X 10(9) and boars aged 16 to 18 months with a DSO of 15.2 +/- 6.2 X 10(9). A highly significant correlation was found between bodyweight and all the semen characteristics examined, the highest correlation being with total number of sperm in the ejaculate. Daily sperm output was not significantly correlated with testicular size as measured by width or length in the live animal. Copulatory behavior had little influence on semen characteristics. Semen characteristics studied were not found to be adversely affected by season. A highly significant correlation between total volume and fluid volume, total volume and gel volume, and total volume and sperm concentration was found, but no correlation was found between total volume and total sperm in the ejaculate. Fluid volume was correlated significantly with gel volume, sperm concentration and total sperm in the ejaculate. A highly significant correlation was found between sperm concentration and total sperm in the ejaculate.     

The chemotactic properties of porcine seminal components toward neutrophils in vitro

Our objectives were to investigate the mechanisms of postbreeding inflammation in swine by examining the chemotactic properties of polymorphonuclear neutrophilic granulocytes (PMN) and of various populations of spermatozoa and seminal plasma. Epididymal spermatozoa from two boars obtained under sterile conditions, washed ejaculated spermatozoa from two boars, and pooled seminal plasma from eight boars of known fertility were examined for chemotaxis to PMN. The chemotaxis of blood-derived PMN in response to sperm and seminal plasma was evaluated and expressed as a percentage of a positive control (lipopolysaccharide-activated blood plasma). The mean chemotactic effect of washed sperm alone (4.4+/-0.04) and of epididymal sperm alone (3.4+/-0.06) was not different from that of the negative controls (3.1+/-0.05) of McCoy's medium with 10% heat-inactivated fetal calf serum. A marked chemotactic effect was detected when washed ejaculated and epididymal sperm were incubated with blood plasma, compared with blood plasma without spermatozoa (P < 0.001). Washed sperm in blood plasma (86.2+/-5.6) and epididymal sperm in blood plasma (83.9+/-7.7) were different from blood plasma alone (11.2+/-1.5), but no differences were detected between the two populations of sperm. This effect, however, was not completely inhibited by heat inactivation of the blood plasma. The chemotactic response of washed ejaculated and epididymal spermatozoa incubated in lipopolysaccharide-treated, heat-inactivated blood plasma were greater than that of the negative control (P < 0.05). Polymorphonuclear neutrophilic granulocyte migration toward seminal plasma was similar to the negative control (4.0+/-0.04 vs 3.1+/-0.05). It seems that porcine epididymal sperm and ejaculated sperm activate chemotactic components in porcine blood plasma and heat-inactivated blood plasma, suggesting that, at least partially, a heat-stable (noncomplement) blood plasma component may be involved in sperm-induced PMN chemotaxis. In contrast, porcine seminal plasma was not chemotactic to PMN. These results support the hypothesis that spermatozoa play an active role in initiating postbreeding endometritis.     

Cross-sectional imaging assisted selection for heart performance in pigs

A two-way selection procedure was performed on a Landrace pig line. First the cardiac output (CO) values (6.89 +/- 1.27 L/min) were estimated by ECG-gated magnetic resonance imaging (MRI) to quantify the heart performance of the boars (n = 30), then total body skeletal muscle volume (MVTB; 48.7 +/- 5.17 dm3) was determined applying spiral computerised tomography (CT). The relative cardiac output value (RCO) was developed, expressing the relationship between CO and MVTB. Four superior [RCO value below 6.7 dm3 / (L x min(-1))] and one minus variant [(8.97 dm3 / (L x min(-1))] boars were taken into breeding. The best fifteen percentage of the first generation males (n = 30) was characterised according to their RCO values. Significant difference was found between the developed performance measure of the progenies of minus and plus variant boars [8.2 +/- 0.65 and 5.63 +/- 0.70 dm3 / (L x min(-1)), n = 7 and 23], respectively. Comparing the existing five progeny groups, all of the 'HP+' groups differed significantly from the 'HP-' one, where the largest heart performance contrast found was 3.2 dm3 / (L x min(-1)). Based upon the results, the selection is being continued on a larger population.     

Cytogenetic study of bovine leukosis

Nine dairy cows aged four to eleven years were subjected to examination by chromosomal analysis. These cows had been found, by haematological examination, to suffer from leucosis. The study also covered one ten-day-old calf - heifer. The test group included two dam-daughter pairs. The animals belonged to the Black-Pied Lowland breed. The blood was sampled from vena jugularis and the karyotypes were processed and evaluated by the method after Moorhead et al. (1960), modified by Lojda et al. (1974). A list was kept for each animal. The tested animals were included in classes by the percentages of the chromosome aberrations: class I - two animals (up to 10% of aberrations), class II - seven animals (from 10% to 20% of aberrations), class III - one animal (above 20% of aberrations). Hyposomy was found in all cases, polysomy and hyperploidy in four cases. Structural aberrations were observed in nine cases, breaks being the most frequent anomalies (7 cases). Breaks on sexual chromosomes were observed in five cases, including the dam-daughter pairs; centric fusion occurred in one case and mixed aberrations in two cases.     

Novel insight into the control of litter size in pigs, using placental efficiency as a selection tool.

Chinese Meishan pigs produce three to five more pigs per litter than less-prolific U.S. or European pig breeds as a result of a markedly decreased placental size and an increased pig weight: placental weight ratio (placental efficiency). We hypothesized that as a result of their intense selection for prolificacy, the Chinese had indirectly selected for a smaller, more efficient placenta in the Meishan breed. The goals of this study were to determine whether 1) significant variation in placental size and efficiency existed within our population of purebred Yorkshire pigs and 2) selection of pigs (boars and gilts) based on clear differences in placental size and efficiency would affect litter size. There was significant (approximately threefold) variation in placental efficiency in our herd of Yorkshire pigs, and marked (approximately twofold) variation existed within individual litters. We then selected pigs (boars and gilts) that had either a higher (A Group) or lower (B Group) than average placental efficiency. Although the birth weights of selected A Group pigs were similar to those of the B Group pigs, they had markedly smaller placentae. Males from each group (A or B) were bred to the females of the same group, and farrowing data were collected from parities 1 and 2. In both parities, A Group females farrowed more live pigs per litter than did B Group females (12.5 +/- .7 vs 9.6 +/- .5, P < .05). Although A Group pigs were on average approximately 20% lighter than B group pigs (1.2 +/- .1 vs 1.5 +/- .1 kg, P < .05), their placentae were approximately 40% lighter (250 +/- 10 vs 347 +/- 15 g, P < .01), resulting in a marked increase in placental efficiency. The results of this study suggest that selection on placental size and efficiency may provide a valuable tool for optimizing litter size in commercially important pig breeds.     

Plasma concentration profiles of gonadotrophins and testosterone in the adult boar.

Follicle stimulating hormone, luteinizing hormone and testosterone were measured by radioimmunoassay in plasma samples collected at 15 min intervals for a 12 h period in eight adult boars. Pulse increases in follicle stimulating hormone concentrations varied from one to four between individual boars while those of luteinizing hormone ranged from zero to four. The index of hormone production, provided by calculation of the area under the curve, was 0.5 +/- 0.51 microgram/L (means +/- S.D.) for follicle stimulating hormone and 0.46 +/- 0.11 microgram/L (means +/- S.D.) for luteinizing hormone. A significant correlation between changes in follicle stimulating hormone and luteinizing hormone values was seen in only two boars. The mean plasma testosterone concentration was 7.43 +/- 1.58 nM/L (means +/- S.D.). An identified increase in testosterone values occurred once in the 12 h period for six of the boars but was not noted in the other two animals. Although increases in testosterone could be identified with a previous pulse of luteinizing hormone, not all luteinizing hormone pulses were followed by an elevation in testosterone. A significant correlation between luteinizing hormone and testosterone was present in three of the eight animals. Follicle stimulating hormone and luteinizing hormone were measured in samples similarly collected two weeks after castration in the same eight boars. The number of pulses of follicle stimulating hormone increased significantly (p less than 0.05) and ranged from 3 to 7/12 h. The index of production of 1.8 +/- 1.15 micrograms/L (mean +/- S.D.) also represented a significant increase (p less than 0.05) over precastration follicle stimulating hormone values.(ABSTRACT TRUNCATED AT 250 WORDS)     

Expression of 3beta-hydroxysteroid dehydrogenase, cytochrome P450-c17, and sulfotransferase 2B1 proteins in liver and testis of pigs of two breeds: relationship with adipose tissue androstenone concentration

An excessive accumulation of androstenone in pig adipose tissue is a major contributor to the phenomenon of boar taint. Androstenone deposition is dependent on the rate of androstenone biosynthesis in testis and androstenone degradation in liver. The aim of the current study was to examine the possibility of the existence of breed-specific mechanisms controlling androstenone accumulation in pig adipose tissue. The specific objective was to investigate the expression of some of the key enzymes involved in testicular and hepatic androstenone metabolism in pigs of 2 breeds by using animals with high and low androstenone concentrations within each breed. The study was conducted with Norwegian Landrace (N. Landrace) and Duroc boars. The mean androstenone values for the low- and high-androstenone groups were 0.1 +/- 0.01 microg/g and 7.58 +/- 0.68 microg/g for N. Landrace boars, and 0.22 +/- 0.04 microg/g and 13.55 +/- 1.14 microg/g for Duroc boars. The enzymes investigated were 3beta-hydroxysteroid dehydrogenase (3beta-HSD), cytochrome P450-c17, and sulfotransferase 2B1 (SULT2B1). Expression of cytochrome P450-c17 in liver and testis did not differ between animals with high and low androstenone concentrations in either the N. Landrace or Duroc breed. Expression of hepatic 3beta-HSD, which catalyzes the first stage of androstenone degradation, was decreased in high-androstenone N. Landrace boars (P < 0.01), but not in high-androstenone Duroc boars. In contrast, the expression of hepatic SULT2B1, which catalyzes the second stage of steroid catabolism, was decreased in high-androstenone Duroc animals (P < 0.05), but not in high-androstenone N. Landrace animals. Sulfotransferase 2B1 was also inhibited in testis of high-androstenone pigs of both breeds compared with low-androstenone animals. We report breed differences in expression of the androstenone-metabolizing enzymes 3beta-HSD and SULT2B1 in the liver of high- and low-androstenone pigs. It is suggested that accumulation of androstenone in adipose tissue of N. Landrace boars might be related to a low rate of hepatic androstenone degradation in metabolic stage I, whereas the high androstenone concentration in Duroc boars might be related to a low rate of androstenone metabolism in metabolic stage II.