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.

Normal values for the scrotal circumference in rams of gotlandic breed.

Selection of fertile sires is crucial for profitable lamb production. Males with larger testes tend to sire daughters that reach puberty at an earlier age and ovulate more ova during each oestrus period. Measurement of the scrotal circumference (SC) is thus an essential part of the breeding soundness evaluation. Testicular size varies with breed, age and time of the year. No SC values or recommendations for minimal values have been established in any of the Scandinavian domestic sheep breeds. Data were recorded of the SC, age and weight in 245 ram lambs and 27 mature rams of the Gotlandic breed, which is the breed that constitutes about 50% of the Swedish sheep population. For the ram lambs, the overall mean SC was 28.9 (+/-1.9) cm at an average age of 170 (+/-9) days and mean weight of 53.5 (+/-7.0) kg, and the mean SC varied between 27.1 and 29.6 cm depending on age and weight. For mature rams (17-54 month old), the mean SC was 32.4(+/-2) cm. To provide a practical tool for exclusion of rams with sub-optimal reproductive capacity (abnormal testes or those with small testes because of delayed puberty) a threshold value was established based on the average SC minus 2 SD. The calculated minimal SC is 26 cm for ram lambs >5.5 months of age with a body weight of >50 kg. For mature rams, minimum SC is 28 cm regardless of weight and age.

Hormonal profiles and embryo survival of sows subjected to induced stress during days 13 and 14 of pregnancy.

Group housing of sows during the mating and gestation period has become the overall common management practice in Sweden. Loose housing is probably less stressful for the animals because it allows them more opportunities to behave naturally, but mixing unfamiliar sows does create a stressful situation due to aggressive interactions, which can lead to food deprivation. The objective of the present study was to investigate and compare the effects of stress in form of food deprivation and ACTH administration at days 13 and 14 of pregnancy (day 1, first day of standing oestrus) in sows. The hormonal secretion of the sows and foetal survival by day 30 of pregnancy was, therefore, studied in 17 crossbred multiparous sows. The sows were randomly allocated into three different groups: one control (C-) group; one food deprived (FD-) group, which was deprived of food from the morning of day 13 of pregnancy until the evening meal on day 14; and a third group (A-), which was given intravenous injections of synthetic ACTH (Synachten Depot), at a dose of 0.01 mg/kg body weight every sixth hour from 6 a.m. on day 13 until 6 a.m. on day 15 of pregnancy. All sows were slaughtered at 30 +/- 2 day of pregnancy and the genital tracts recovered. Total number of corpora lutea (CL), total number of viable or nonviable embryos and foetal survival rates were determined. Samples from the peripheral blood circulation were collected four times a day from day 12 until slaughter, except during days 13-15 when blood was collected every second hour. The blood samples were analysed for cortisol, progesterone, oestrone, prostaglandin F(2alpha)-metabolite, oestrone-sulphate, insulin, free fatty acids and triglycerides. FD-sows had increased levels of cortisol, free fatty acids and progesterone, as well as a lowered level of insulin in the peripheral blood plasma, while A-group sows had increased levels of both cortisol and insulin compared with the C-group. Treatment with ACTH seemed to cause a 2-day delay in the increase of oestrone, from day 19, as seen in the FD- and C-group, to day 21 of pregnancy. At the time of slaughter, there were no significant differences among groups in terms of total number of foetuses and foetal survival rate. The results of the present study suggest a capacity of the sow to compensate for the influence of induced moderate stress at the time of pregnancy when maternal recognition occurs.

Transport of fertilised and unfertilized ova in sows.

Transport of fertilised and unfertilized ova was studied in 22 crossbred (Landrace x Yorkshire) multiparous sows. Sows in the inseminated group (I-group, n=11) were inseminated once with 100ml of BTS extended semen from two fertile boars with a total of 10 x 10 (9) spermatozoa during the second oestrus after weaning between 18 and 8h prior to estimated time of ovulation, as estimated from the first oestrus after weaning. All the sows were slaughtered between 36 and 48 h after ovulation in the second oestrus after weaning by stunning and bleeding. After slaughter, the reproductive tract was immediately recovered, the isthmus was divided into three equal segments, and the number of ova was determined in each segment and in the upper third of the uterine horn from the UTJ. There were no significant differences (P>0.05) either in the intervals from ovulation to slaughter (42.3+/-6.2h versus 43.2+/-5.4h) or in the numbers of corpora lutea (CL) (18.2+/-5.5 versus 15.9+/-3.5) between the non-inseminated (N-group) and the inseminated groups (I-group), respectively. Ova recovery rate was 92.5% in the N-group and 82.9% in the I-group (P>0.05). In the I-group, ova had passed 2.2+/-0.3 segments whereas in the N-group, ova had passed 2.6+/-0.3 segments (P=0.38). It can be concluded that there is no difference in the transportation of either fertilised or unfertilized ova in the reproductive tract of pigs.

Effect of repeated ACTH-stimulation on early embryonic development and hormonal profiles in sows.

This study was conducted to evaluate the effect of adrenal stimulation by synthetic adrenocorticotrophic hormone (ACTH) on the first 2 days of pregnancy in 22 multiparous sows. The experiment was performed during the second oestrus after weaning and the sows were divided into one control (C-group) and one experiment group (E-group). To determine the time of ovulation, transrectal ultrasonographic examination was performed. E-group sows were treated repeatedly with 0.1 mg/kg bodyweight of synthetic ACTH (tetracosactide) i.v. 4-8h after ovulation and continuing every 6h, until slaughter. Blood samples were collected every second hour from about 12h before expected ovulation until slaughter and were analyzed for cortisol, prostaglandin F(2 alpha) -metabolite, and progesterone (P(4)). All sows were slaughtered approximately 48 h after ovulation and the isthmic part of the oviduct was divided into three equally long segments and flushed separately with phosphate buffered saline (PBS). The uterine horns were also flushed with PBS. The embryos of the E-group sows tended (P=0.056) to have a lower cleavage rate than the embryos of the C-group sows but there was no difference between groups in oviductal transport rate of the embryos. In the E-group, significantly (P<0.05) more sows had only embryos with <20 spermatozoa attached to the ZP compared with the C-group. The plasma concentration of cortisol was significantly higher (P<0.0001) in the E-group sows during the time of treatment while the baseline level of prostaglandin F(2 alpha) -metabolite was significantly lower. The baseline level of progesterone increased in both groups after ovulation but there was no significant difference between the groups. Repeated ACTH-stimulation (1) had no effect on the oviductal transport rate of the embryos, (2) had a negative effect on the embryo development, (3) and caused a changed endocrine profile that might have changed oviductal milieu affecting embryo development.

Impact of postovulatory food deprivation on the ova transport, hormonal profiles and metabolic changes in sows.

The effect of food deprivation on ova transport, hormonal profiles and metabolic changes was studied in 20 crossbred multiparous sows during their second oestrus after weaning. To determine the time of ovulation, transrectal ultrasonographic examination was performed. The sows were divided into 2 groups, one control group (C-group), which was fed according to Swedish standards, and one experimental group (E-group). The E-group sows were deprived of food from the first morning meal after ovulation until slaughter. Blood samples were collected every second hour from about 12 h before expected ovulation in the second oestrus after weaning until slaughter and were analysed for progesterone, prostaglandin F2 alpha-metabolite, insulin, glucose, free fatty acids and triglycerides. All sows were slaughtered approximately 48 h after ovulation and the genital tract was recovered. The isthmic part of the oviduct was divided into 3 equally long segments and flushed separately with phosphate buffered saline (PBS). Uterine horns were also flushed with PBS. A significantly greater number of ova were found in the first and second part of the isthmus in the E-group (p = 0.05) while in the C-group most of the ova were found in the third part of the isthmus or the uterus (p = 0.01). The level of prostaglandin F2 alpha-metabolite was significantly higher in the E-group compared with the C-group. The concentration of progesterone increased in both groups after ovulation but there were no significant differences between the groups. The other blood parameters showed that the food-deprived sows were in a catabolic state. The 48 h period of fasting results, directly or indirectly in an delayed ova transport, which may be due to a delayed relaxation in the smooth circular muscle layer of the isthmus.

The influence of inhibited prostaglandin biosynthesis on post-ovulatory oviductal ova transport in sows.

Changes in prostaglandin and progesterone concentrations after ovulation seem to affect reproductive functions in the sow. The influence of lowered prostaglandin levels on ova transport velocity through the isthmus part of the oviduct, and on progesterone concentrations, was studied during the second estrus after weaning in thirteen purebred Yorkshire multiparous sows. To determine the time of ovulation transrectal ultrasonographic examination was performed. In the second estrus, six sows were given intravenous injections of flunixin meglumine (2.2 mg/kg body weight) every sixth hour from 4 to 8 h after time of ovulation until about 48 h after ovulation, at which time the sows were slaughtered. Blood samples were collected every second hour from about 12 h before ovulation until slaughter. Progesterone and prostaglandin F2alpha (PGF2alpha) metabolite levels were determined. Immediately after slaughter the isthmus part of the oviducts were cut into 3 equally long segments and the number of ova in each segment, and in the upper part of the uterine horns, was determined. Before start of treatment, PGF2alpha metabolite levels were similar in the 2 groups (P=0.84). In the treatment group, PGF2alpha values dropped to below the detection limit immediately after start of treatment, whereas in the control group the concentrations were quite stable throughout the sampling period (P=0.005). Ova recovery rate was 94% in the treatment group and 95 % in the control group. At time of slaughter, in the treatment group ova had on average passed 2.1 segments whereas in the control group the ova had passed 2.5 segments (P=0.57). The progesterone levels increased continuously in both groups after ovulation but there was no difference in the mean progesterone concentrations between the two groups before (P=0.96) or after (P=0.58) ovulation. It can be concluded that the transport of ova through the isthmus part of the oviduct is unaffected by an inhibition of prostaglandin synthesis immediately after ovulation. Furthermore, the post-ovulatory progesterone profile seems unaffected by lowered PGF2alpha levels.

Reproductive performance among sows group-housed during late lactation.

Four farms (540 sows) that group-housed sows from 2 weeks of lactation until weaning (G-farms) and 3 farms (300 sows)--used as controls--that kept the sows individually penned throughout the 5- to 6-week-long lactation period (C-farms) were compared in terms of reproductive performance. All sows were crossbred Swedish Yorkshire x Swedish Landrace. Sows were kept in groups in the breeding section and were also grouped on deep litter in the dry-sow section on all farms. Batchwise farrowing routines were used on all farms, and batch size ranged between 8 and 22 sows. Fertility and culling data were collected in connection with monthly visits to the farms for 16 months. Among the older (> or = 5th parity) sows, litter sizes were significantly (p = 0.02) smaller in the G-farm group compared with the C-farm group. The percentage of sows mated within 10 days post weaning was lower (p < 0.001) in the G-farm group than in the C-farm group, with the difference being most evident among the older (> or = 5th parity) sows. The frequency of repeat breeders among primiparous sows was similar in the 2 housing systems, but among the multiparous sows repeat-breeder frequency was higher (p = 0.04) in the G-farm group than in the C-farm group. In both groups, repeat-breeder frequency seemed to be highest from July to September. Repeat breeding/failure to farrow was a common reason for culling in the G-farm group. These results indicate that reproductive performance was impaired in the group-housing system. This impairment could have been due partly to the occurrence of lactational oestrus, which makes it difficult to maintain adequate routines for oestrous detection and mating/insemination.

Relationships between health and weight loss during lactation and between health and ability to return to oestrus after weaning in primiparous sows.

The study comprises observations in 301 Swedish Yorkshire primiparous sows belonging to a research herd. During the 6 weeks of lactation, they were fed according to a conventional feeding regime based on litter size. The sows were weighed at farrowing and at weaning. After weaning the sows were checked daily for standing reflex and blood samples for determination of plasma progesterone were drawn regularly. Diseases occurring during lactation were recorded in 223 sows. A clinical health examination of these sows was also performed on the day of weaning, including body temperature, condition scoring, appetite, locomotor disorders, remarks on legs and mammary glands. A blood sample was drawn 1 week before weaning in 155 sows for analysis of blood haemoglobin concentration, packed cell volume, total white blood cell count, serum concentration of urea, creatinine, triglycerides, free fatty acids, total protein and electrophoretic separation of proteins. Sows with large weight loss had a higher total incidence of diseases during lactation, mastitis being the most common disease, than sows with small weight loss. Sows with large weight loss seemed to be more catabolic during late lactation than sows with small weight loss, according to the blood analyses. The blood analyses did not show any signs of subclinical infection being more common among sows with large weight loss than among sows with small weight loss. There were neither any significant differences in the total incidence of diseases during lactation nor in the health at weaning between sows returning to oestrus within 10 days of weaning and sows not returning within this time.

Pre- and post-weaning piglet performance, sow food intake and change in backfat thickness in a group-housing system for lactating sows.

Four farms that group-housed sows from about 2 weeks of lactation until weaning (G-farms) and 3 farms, used as controls, that kept the sows individually penned throughout the 5 to 6-week-long lactation period (C-farms) were compared in terms of pre- and post-weaning piglet growth rate and mortality, sow food intake and change in backfat thickness. Piglets from 169 G-farm sows and 136 C-farm sows were individually weighed at the time of grouping and weaning. In addition, some of the piglets were weighed 2 weeks post weaning. Piglet mortality was recorded during the pre- and post-weaning periods. Sow backfat thickness was measured at the time of grouping (at a corresponding time in the C-farms) and weaning, and sow food consumption was determined during the group-housing period. Piglet weight, growth rate and within-litter variation in growth rate did not differ significantly between the two groups during the group-housing and post-weaning periods. However, the pre-weaning growth rate varied considerably between farms. For multiparous sows during the group-housing period, piglet mortality was higher (p = 0.002) in the G-farm group (6.5%) than in the C-farm group (1.4%). However, for primiparous sows the corresponding piglet mortality was similar (p = 0.21) in the two groups. Significant between-batch variation in mortality during the group-housing period was noted within the G-farms but not within the C-farms. At the time of weaning, backfat thickness tended (p = 0.09) to be higher in the G-farm group than in the C-farm group. For primiparous sows the decrease in backfat thickness was similar (p = 0.37) in the two groups. By contrast, multiparous G-farm sows gained backfat during the group-housing period, whereas multiparous C-farm sows lost some backfat (p = 0.02). G-farm sows consumed 23% more food than C-farm sows during the group-housing period. These results indicate that productivity is lower in the group-housing system, mainly owing to the poor performance of the older sows.

Ovarian activity at naturally attained oestrus in the sow. An ultrasonographic and LH study.

In 6 multiparous crossbred sows (2nd to 4th parity, Swedish Landrace x Swedish Yorkshire), 15 proosestrous-oestrous periods during 2 oestrous cycles were studied after weaning. The animals were controlled for oestrus, and the follicular growth and ovulation in their ovaries were followed by transrectal ultrasonography. Blood was sampled through indwelling catheters for analyses of LH and progesterone (P4). The duration of oestrus (standing reflex) was 47 +/- 12.4 h, and the interval from onset of standing reflex until the end of ovulation was 39 +/- 12.4 h (range 20-64 h). The LH peak concentration was 3.7 +/- 0.8 microgram/l, and the interval from LH peak level until ovulation was 23 +/- 8.4 h (range 8-32 h). The onset of standing reflex occurred in average 13 h before the LH peak level (range -4 - +36 h). The peripheral plasma concentration of P4 showed a normal cyclic pattern in all animals. Low levels (mean levels, 1.1-1.3 nmol/l) were seen during prooestrus and oestrus, high mean levels were found on days 10-16 (45-75 nmol/l) in the oestrous cycle. It was concluded that for an accurate determination of ovulation, each animal has to be examined repeatedly. Ultrasonography is a most valuable tool for this purpose.

A field study on group housing of lactating sows with special reference to sow health at weaning.

Four farms that group-housed sows from 2 weeks of lactation until weaning (G-farms) and 3 farms that kept the sows individually penned throughout the 5 to 6-week-long lactation period (C-farms), were compared in terms of sow health. All sows were crossbred Swedish Yorkshire x Swedish Landrace. The daily food ration was similar on all farms except during the group-housing period, when G-farm sows were fed ad libitum. Sows were grouped in the breeding section and kept grouped on deep litter in the dry sow section on all farms. Individual health examinations were performed at the time of weaning (+/- 4 days) on 179 G-farm sows and on 167 C-farm sows. Teat- and udder skin wounds occurred less frequently (p < 0.001) in G-farm sows than in C-farm sows. In addition, preweaning atrophy of all mammary glands occurred in 6.6% of the G-farm-sows but not in a single C-farm sow (p < 0.001). This indicates that sow-piglet interactions decrease when sows are group housed. However, these differences did not occur in primiparous sows, suggesting that the relation between the primiparous sow and her litter is not affected. Mastitis frequency was the same in the 2 systems. Moreover, the frequency of locomotor disorders was the same in the 2 groups, and hoof overgrowth was common in both systems. These similarities could be due to the fact that all farms group housed dry sows on deep litter. A strong relation (p < 0.001) between hoof overgrowth and locomotor disorders was evident. Low access to food due to low rank among primiparous group-housed sows was indicated by a lower (p < 0.05) backfat thickness compared with multiparous sows, and a higher (p < 0.001) frequency of skin wounds compared with individually housed primiparous sows.

Energy metabolism during late gestation and lactation in multiparous sows in relation to backfat thickness and the interval from weaning to first oestrus.

Ten crossbred, fourth or fifth parity sows were divided into 2 groups - high (H) and low (L)- according to their backfat thickness 9 days before parturition. Body weight, backfat thickness and litter weight were recorded repeatedly during a 5 week lactation period. The length of the interval from weaning to first oestrus was also noted. All sows were fed a commercial diet (11.9 MJ/kg, 14.5% crude protein). During gestation, daily food intake was 2.2 kg/sow, while during lactation it was 3.0 kg/sow plus 0.4 kg/piglet. Blood samples were drawn on day 9 before parturition and on days 2, 7, 14 and 21 of lactation. The samples were analysed to determine concentrations of glucose, urea nitrogen, creatinine, triglycerides, free fatty acids and beta-hydroxybutyric acid. In both groups, concentrations of free fatty acids and urea nitrogen were low on day 9 before parturition while those of triglycerides were high, indicating anabolism regardless of backfat thickness. During the first week of lactation, concentrations of free fatty acids increased in the H-group but not in the L-group, and concentrations of urea nitrogen were higher in the H-group. These differences, together with the greater loss of weight observed in the H-group, indicate that catabolism of maternal fat and protein depots was more pronounced in the H-group than in the L-group during this time. On day 14 of lactation, both groups showed equally low concentrations of free fatty acids, decreasing creatinine concentrations and stable triglyceride and urea nitrogen concentrations. Furthermore, weight loss during the second and third weeks of lactation was low in both groups. These facts, taken together, indicate that the catabolic rate was decreasing in both groups during this period. No differences in return to oestrus interval were noted between the groups. The present study indicates that under a restricted feeding regime the catabolic rate during the first week of lactation is higher in sows with higher backfat thickness in late gestation. As lactation progresses, a more balanced metabolism is achieved regardless of backfat thickness, which may tend to reduce differences in return to oestrous interval.