Applying a Progesterone Assay to Faecal Samples Collected from Sows during the Oestrous Cycle

Puberty in female wild boar (Sus scrofa) in Sweden

Background

Since the re-appearance of wild boars in Sweden in the 1970s, the population has increased. Besides having large litter sizes, puberty at an early age is considered as an important factor contributing to the high reproductive potential of wild boar. Although controversial, supplemental feeding is applied to varying extent throughout the wild boar range in Sweden, and its effect on wild boar reproduction is debated. The aim of this study was to investigate the proportion of post-pubertal female wild boar gilts in a population subjected to supplemental feeding, in relation to age, weight, and season. Also, the effect of another definition of puberty (based upon follicular size) on the outcome of the proportion of female wild boar gilts considered to be able to reproduce in a population was illustrated. Between Jan 2013 and Dec 2015 reproductive organs from 592 female wild boars, were collected. Ovaries and uterus were macroscopically examined, and reproductive stage was determined by the presence of ovarian structures and uterus characteristics. Age was estimated using tooth eruption and tooth replacement, and weight was noted. A subset of 175 female wild boars, aged 5–15 months, was included in this study. An animal was considered to be post-pubertal if the ovaries contained one or more corpora lutea (CL) or if the uterus showed signs of previous pregnancy (presence of enlarged blood vessels in the cut surface between the mesometric ligament and the uterus).

Results

In total, 29 (16.6 %) animals were classified as post-pubertal. Field dressed weight ranged from 20.6 to 65.3 kg. Season, weight, and age class significantly influenced the variation in proportion of post-pubertal females. Post-pubertal animals were found in autumn, winter, and spring, but not in the summer season. Another definition of puberty, based on follicle size, lead to different result on proportions of animals considered to have passed puberty.

Conclusions

Season, weight, and age significantly influenced the variation in proportion of post-pubertal wild boar females. The proportion of post-pubertal animals increased with age and weight. However, weight is probably a better proxy for puberty than age group is. The proportion of post-pubertal females also increased from summer to spring suggesting a seasonal reproductive pattern. Different definitions of puberty will result in various outcomes, which high-lights the importance of using adequate definition of puberty.

A 25 years experience of group-housed sows-reproduction in animal welfare-friendly systems

Since January 1 2013, group housing of sows has been compulsory within the European Union (EU) in all pig holdings with more than ten sows. Sows and gilts need to be kept in groups from 4 weeks after service to 1 week before the expected time of farrowing (Article 3(4) of Directive 2008/120/EC on the protection of pigs). The legislation regarding group housing was adopted already in 2001 and a long transitional period was allowed to give member states and producers enough time for adaptation. Even so, group housing of sows still seems to be uncommon in the EU, and is also uncommon in commercial pig farming systems in the rest of the world. In this review we share our experience of the Swedish 25 years of animal welfare legislation stipulating that sows must be loose-housed which de facto means group housed. The two most important concerns related to reproductive function among group-housed sows are the occurrence of lactational oestrus when sows are group-housed during lactation, and the stress that is associated with group housing during mating and gestation. Field and clinical observations in non-lactating, group-housed sows in Sweden suggest that by making basic facts known about the pig reproductive physiology related to mating, we might achieve application of efficient batch-wise breeding without pharmacological interventions. Group housing of lactating sows has some production disadvantages and somewhat lower productivity would likely have to be expected. Recordings of behavioural indicators in different housing systems suggest a lower welfare level in stalled animals compared with group-housed ones. However, there are no consistent effects on the reproductive performance associated with different housing systems. Experimental studies suggest that the most sensitive period, regarding disturbance of reproductive functions by external stressors, is the time around oestrus. We conclude that by keeping sows according to the pig welfare-friendly Directive 2008/120/EC, it is possible to combine group-housing of sows with good reproductive performance and productivity. However, substantially increased research and development is needed to optimize these systems.

Changes in fecal progestagen profile after excretion in miniature pigs

The aim of this study was to evaluate whether the fecal progestagen (progesterone and its metabolites) levels of miniature pigs would change after excretion at room temperature. Our initial investigation focused on the correlations between the fecal progestagen concentrations with and without ether extraction and between the plasma progesterone and fecal progestagen concentrations in order to develop an enzyme-linked immunosorbent assay (ELISA) for fecal progestagen without ether extraction. There were significant correlations between fecal progestagen concentrations with and without ether extraction (r=0.880) and between fecal progestagen concentrations without ether extraction and plasma progesterone (r=0.763). The fecal progestagen concentration obtained by ELISA without ether extraction was almost identical to that obtained with ether extraction. These results validate the ELISA method without ether extraction, which was therefore used for the latter experiment. Fecal samples collected from the pigs were preserved for 0-24 h at room temperature, and then their fecal progestagen concentrations were measured. The fecal samples preserved for 0 to 24 h were analyzed by high performance liquid chromatography (HPLC) and ELISA. The concentrations of all samples significantly increased with time after preservation. The progestagen concentration of fresh feces (0 h) with high progestagen concentration (>1000 ng/g) increased significantly after 3 h. The concentration increased significantly after 12 h for fresh feces containing about 500 ng/g progestagen. HPLC analysis is showed that the fecal progesterone concentration, but not its other metabolites, doubled 24 h after excretion compared with the concentration at 0 h. These results suggest that dynamic changes in the profile of progesterone metabolites occur in feces after excretion.

Ovarian activity and oestrous signs among group-housed, lactating sows: influence of behaviour, environment and production

Animal welfare concerns require the development of housing systems that allow the animals to express their natural behaviour. One example of this is the group-housing system for lactating sows. The present study aimed at exploring ovarian activity in such a system. Thirty-eight sows farrowing individually outdoors during spring and summer, and indoors during autumn and winter, and group-housed in groups of four during weeks 3-7 of the lactation period, were monitored regarding reproductive functions, behaviour and production during their first to fourth lactation period. Average ovulation frequency during lactation was 47%. Only 50% of these ovulating cases were accompanied by a standing oestrus. Lactational ovulation frequency was higher in later parities (p < 0.001). Ovulation frequency was higher (p < 0.05) during winter (74%) and spring (69%), than during summer (10%) and autumn (23%). Occurrence of lactational ovulation was associated with some aspects of suckling behaviour and also with litter weight gain (p < 0.05). Forty-nine per cent of the lactational ovulations occurred during the seventh week of lactation. Timing of ovulation seemed positively (p = 0.08) associated with weight loss during lactation. Compared with the sows that were anoestrus during lactation, oestradiol-17beta values were higher (p < 0.05) only in the week before occurrence of lactational ovulation. Weaning-to-oestrous interval was prolonged (p < 0.05) among the sows that ovulated during lactation. The present study identifies several factors influencing ovarian activity among group-housed sows, thereby providing tools for the control of lactational ovulation in group-housing systems.

Age, body weight and backfat thickness at first observed oestrus in crossbred Landrace x Yorkshire gilts, seasonal variations and their influence on subsequence reproductive performance

The objective of the present study was to investigate puberty attainment in crossbred Landrace x Yorkshire (LY) gilts reared under tropical conditions and their subsequent reproductive performance. This study was carried out in a 2400-sow herd over a 1-year period. A total of 696 crossbred LY replacement gilts were included. Faecal samples from 214 gilts were collected to determine the faecal progesterone profiles around the time of first oestrus. Solid-phase 125I-radioimmunoassay was used to determine the progesterone concentrations in the faecal extract. The gilts entered the herd at an average age of 177.5 +/- 12.6 days, 95.7 +/- 10.2 kg body weight (BW) and a backfat thickness (BF) of 12.0 +/- 2.9 mm. On average, the gilts expressed first standing oestrus at 195 days of age, 106 kg of BW and a BF of 13.0 mm. The interval from entry to the gilt pool to the first observed oestrus (EOI) was 24.4 +/- 18.0 days (range 0-88 days). The hormonal profile indicated that the gilts that actually ovulated during the first observed oestrus was 34% (group A), the gilts that had ovulated before the first observed oestrus was 21% (group B) and the gilts that did not ovulate during the first observed oestrus was 45% (group C). During summer the proportion of group A gilts was significantly lower than during the winter and the rainy seasons (P < 0.05). The BW of gilts at entry significantly correlated with the BF at entry (r = 0.31, P < 0.001), the age at entry (r = 0.47, P < 0.001), the BW at first oestrus (r = 0.65, P < 0.001) and the BF at first oestrus (r = 0.33, P < 0.001). An increase of BW at entry of 1 kg resulted in a decrease of EOI of 0.28 days. The age, BW and BF of gilts at the first observed oestrus significantly influenced the total number of piglets born per litter (TB) and the number of piglets born alive per litter (BA) in the first three parities. Gilts expressing their first oestrus between 181 and 200 days had a significantly larger TB than gilts that expressed first oestrus between 150 and 180 days (P = 0.03) and between 201 and 220 days (P = 0.003). Gilts that showed first oestrus between 110.1 and 120.0 kg had a larger TB and BA than gilts that showed first oestrus between 80.0 and 100.0 kg (P < 0.05). Gilts that showed first oestrus with a BF between 13.1 and 15.0 mm had a larger TB and BA than gilts that showed first oestrus with a BF between 11.1 and 13.0 mm (P < 0.05). Group A gilts had a significantly larger TB than group B (10.5 piglets/L versus 9.4 piglets/L, P = 0.02), while farrowing rate (FR) did not differ significantly among groups A, B and C (78.1, 76.9 and 77.6%, respectively). Gilts that farrowed in the summer had a larger TB and BA than gilts that farrowed in the winter (TB, P = 0.03; BA, P = 0.09) and the rainy season (TB, P = 0.006; BA, P = 0.003). In conclusion, LY gilts reared under tropical conditions expressed first standing oestrus at 195 days of age, 106 kg BW and a BF of 13.0 mm. Under field conditions, 21% of the gilts with an observed oestrus had ovulated. The proportion of gilts that showed first oestrus and ovulated normally was lowest during the summer. The age, BW and BF at first observed oestrus influenced subsequent reproductive performance over the first three parities. The mean litter size (TB and BA) in the first three parities were highest in gilts that had a first observed oestrus between 181 and 200 days with 110.1-120.0 kg BW and 13.1-15.0 mm BF.

Pregnancy Diagnosis in Miniature Pig by Direct ELISA of Oestrone Derivatives in Faeces

The objectives of the present study were to measure oestrone derivatives [oestrone, oestrone sulphate (E1S) and oestrone glucuronide] in sow faeces by direct enzyme-linked immunosorbent assay (ELISA) and to explore the changes of oestrone derivative profile in faeces of miniature pig for demonstrating the possibility of pregnancy diagnosis. Faecal samples (1.5 g) were put into 6 ml of buffer, shaken and centrifuged. Then supernatant was added to the wells of multi-plate without extraction and incubated with anti-oestrone antibody and horseradish peroxidase-labelled oestrone. Standard solution was prepared at various concentrations of E1S. Sensitivity was estimated as 0.035 ng/ml (0.14 ng/g). Intra- and inter-assay coefficient variations were 3.5-7.7% and 10.9-15.3%, respectively. When 1-5 ng/ml E1S were added to a faecal solution, recovery rates ranged between 80.0 and 103.3%. There is a temporal increase in the E1S equivalent concentration of miniature pig faeces from day 25 to 31 after mating. From day 35 to 70, the E1S equivalent concentrations remained low. Thereafter its concentrations increased again towards farrowing. On day 27 and 29 after mating pregnancy diagnosis by the faecal E1S equivalent concentrations agreed with the results of farrowing (seven of seven animals). These results suggest that the present direct ELISA is practical and suitable as a routine assay for measuring the faecal concentration of oestrone derivatives and that this assay might be usable for pregnancy diagnosis in sows at day 27-29.

Non-invasive methods to measure androgen metabolites in excrements of European stonechats, Saxicola torquata rubicola

Traditionally androgen concentrations are measured invasively in blood plasma. However, non-invasive methods to detect androgens are desirable, as this reduces interference with the natural behavior of the study species and multiple samples can be obtained relatively easy. The aim of this study was to validate a method to measure androgens non-invasively in excrements of male European stonechats (Saxicola torquata rubicola). Extracts of excrements of a male stonechat injected with [3H]testosterone ([3H]T) were chromatographically separated using high performance liquid chromatography (HPLC). The resulting HPLC fractions were then analyzed with a radioimmunoassay against testosterone (T-RIA). The results showed that the assay picked up major metabolites of [3H]T. The physiological relevance of excreted androgen metabolites was further validated by showing that injection of exogenous GnRH to seven males led to a significant increase in excreted androgen metabolites. In contrast, androgen metabolite levels of six saline-injected control males did not increase. Furthermore, excrements from nine males were collected from January until April to see whether the typical seasonal increase in testosterone levels can also be traced when measuring excreted androgen metabolites. As expected, there was a significant seasonal increase in androgen metabolite concentrations. Thus, the T-RIA measures androgen metabolites in droppings of male European stonechats and to our knowledge this study represents the first validation of a non-invasive androgen assay in a passerine bird.

Seasonal relationships between plasma and fecal testosterone in response to GnRH in domestic ganders

In two groups (eight individuals each) of socially acquainted, outdoor-kept, domestic ganders (male Hungarian white: Anser domesticus), basal and GnRH-stimulated plasma testosterone (T) concentrations were compared with fecal testosterone metabolites (TM) in and between three seasons, spring peak of reproductive activity, summer photorefractoriness, and fall sexual reactivation. Plasma was sampled 90 min following the challenge and T was analyzed by radioimmunoassay following the GnRH challenge. Fecal TM were measured by enzyme immunoassay using two group-specific antibodies against 17beta-OH-androgens or a novel antibody against 17-oxo groups, which was found to react with major testosterone metabolites without prior hydrolytic deconjugation. Baseline plasma T and systemic levels were high in spring and fall but low in summer. Plasma T increases in response to GnRH were followed by significantly elevated fecal TM levels 2 to 6 h following the challenge in spring and fall. In fall, at high plasma T levels, fecal TM levels were disproportionally lower than in spring. Variability of TM levels was two to five times higher in feces than in plasma, which explains why correlations between individual plasma T and fecal TM levels generally remained nonsignificant. This points to a low-level short-term relationship between the excreted TM and the plasma T levels. However, the reliability of the method was demonstrated by standard inter- and intraassay variabilities and by a high correspondence between results obtained by the two assays. It is suggested that, with appropriate sample size, fecal TM reflects plasma T increase. However, fecal TM was more variable than the plasma T, and fecal TM responses to GnRH did not always parallel the plasma T response. In addition, seasonal changes in androgen excretion regimes must be taken into account.

Fecal estrone sulfate profile in sows during gestation

The aim of this study was to establish radioimmunoassay (RIA) for fecal estrone sulfate (E1S) and to elucidate changes in fecal E1S during pregnancy in the sow. Fecal E1S was extracted on a commercially available solid phase column, and the E1S fraction obtained was subjected to RIA. The sensitivity of the RIA was 8.5 pg/tube. The intra- and inter-assay coefficients of variation were 8.8-8.9% and 10.7-14.2%, respectively. Mean recovery for E1S added to fecal samples was as high as 95.0%. A significant positive correlation (r = 0.904, n = 147 p < 0.0001) existed between fecal and plasma E1S concentrations. Mean E1S concentration in feces and plasma fluctuated exhibiting two peaks. The first peak of E1S concentration was evident on day 28-32 in feces and on days 26-30 in plasma. The E1S concentration in both feces and plasma remained at baseline levels during mid-pregnancy, but began to rise gradually around days 72-82 and 70-80, in feces and plasma respectively, and reached a peak concentration on days 110-114. Following parturition, the concentration of E1S in plasma declined rapidly, but there was a two-day delay before a decline in fecal E1S. Apart from this two-day delay, changes in fecal E1S were similar to those in plasma E1S. The study indicates that the measurement of E1S in feces could be a useful tool for early pregnancy diagnosis and for monitoring fetal development in sows and gilts.

Measurement of gestagen concentration in feces using a bovine milk progesterone quantitative test EIA kit and its application to early pregnancy diagnosis in the sow

We attempted to measure the gestagen concentration in the feces of pigs by using a commercial bovine milk progesterone quantitative test EIA kit, and investigated the possibility of applying of this method of gestagen concentration measurement to early pregnancy diagnosis in the sow. Feces were collected from the rectum of the pig, and 0.5 g of the feces was placed in 20 ml of distilled water, stirred, and centrifuged. The supernatant was used as the fecal solution for measurement of gestagen. The procedure used for measuring gestagen in feces was the same as that for the measurement of progesterone in milk, except that a standard fecal gestagen solution (0.5-30.0 ng/ml) was prepared by the authors in the laboratory. The sensitivity of measurement using this method was 0.80 ng/ml, or 32.0 ng/g of fecal weight. The recovery was 105.2-105.6%. Intra-assay coeffecients of variation (CVs) were 2.8-8.5%. The interassay CVs were 7.4-10.2%. Gestagen concentrations in feces measured by the present method and progesterone concentrations in peripheral plasma, collected at the same time as the feces were highly correlated (r = 0.98, p < 0.001). The criteria for diagnosis of pregnancy based on the fecal gestagen level was positive for a gestagen level of > or = 200 ng/g and negative for a gestagen level of < 200 ng/g. When fecal gestagen measurements were applied to early pregnancy diagnosis in 149 sows, the accuracy of diagnosis from day 21 to day 25 after the last mating was 96.2% for positive cases (102/106) and 95.3% for negative cases (41/43). Thus, the results of this study show the quantitative measurement of the fecal gestagen concentration in the sow using a bovine milk quantitative test EIA kit is a practical method for early pregnancy diagnosis.