PIn Pig Farming, Growing Concern - Marc Kaufman, Washington Post, June 18, 2001
"Some pork producers and Texas Tech University have experimented with outdoor and group systems for raising sows that are as effective and productive as the stalls, John McGlone said. On his research farm outside Lubbock, sows and their piglets live on fields outdoors with small metal hoop huts for protection.
"The industry may not think that crates are a problem, but what if consumers disagree">
http://www.washingtonpost.com/wp-dyn/articles/
A12663-2001Jun17.html

RESEARCH:

Progesterone therapy during early pregnancy and embryonal survival in primiparous weaned sows - J Mao, and GR Foxcroft, Department of Agricultural, Food and Nutritional Science, University of Alberta. J Anim Sci 1998 Jul;76(7):1922-8.
The experiment was conducted in primiparous sows to determine whether progesterone supplementation during early pregnancy could improve embryonal survival and to confirm a functional relationship between progesterone concentrations in the postovulatory period and embryonal survival. Thirty-four primiparous sows were fed for ad libitum intake from farrowing to d 21 of lactation, restricted to 50% of ad libitum intakes between d 22 and 28, weaned on d 27, and then fed for ad libitum intake from weaning until d 28 of gestation. The number of pigs per litter was standardized to nine within 48 h after farrowing. After mating, sows were allocated either to be treated with ethyl oleate (control group) or to receive progesterone (P4) therapy (progesterone group) as 2 mg of P4/kg(.75) i.m., every 12 h from 36 to 96 h after onset of standing estrus. There was no difference in the weaning-to-estrus interval (123.5 +/- 5.7 vs 123.1 +/- 5.9 h) and number of corpora lutea (18.1 +/- .4 vs 18.3 +/- .5) between the control and progesterone sows (P > .05). Compared with a more gradual increase in control sows, plasma progesterone concentrations in progesterone sows increased immediately from .6 +/- .1 ng/mL at 36 h after onset of standing estrus to 6.3 +/- .5 ng/mL (P < .001) 12 h later and remained high. Total number of embryos, total embryonal survival rate, number of viable embryos, and viable embryonal survival rate on d 28 of gestation in control sows were greater than in progesterone sows (13.3 +/- 1.0 vs 8.5 +/- 1.1; 73.1 +/- 4.7 vs 47.3 +/- 5.4%, P < .005; 12.6 +/- .9 vs 7.1 +/- .9, and 69.5 +/- 4.2 vs 39.7 +/- 4.8%, P < .0005; respectively). Embryonal survival in control sows was comparable to that in previous experiments using the same primiparous sow model, and the relationship between plasma progesterone and embryonal survival seemed similar. However, using the treatment schedule adopted, progesterone not only failed to reverse the presumed detrimental effect of increased catabolism in the late lactation period on embryonal survival, but also adversely affected the number of embryos at d 28 in 7 out of 15 progesterone-treated sows.
PDF : http://www.asas.org/jas/papers/1998/jul/jul1922.pdf

The effects of different photoperiods on reproduction in the sow - AN Perera, and RR Hacker. J Anim Sci 1984 Jun; 58(6):1418-1422.
Three groups of Yorkshire sows (total of 106) were exposed to photoperiods of light:dark (LD) 24:0, 12:12 and 0:24, respectively, from d 1 postweaning to 24 h postestrus. The onset and duration of estrus, conception rate, farrowing rate and litter size were recorded. Serum concentrations of luteinizing hormone (LH), estrogen and progesterone were measured. Sows in the LD 24:0 exhibited behavioral estrus for a longer period (P less than .0001) than those in LD 12:12 (4.0 vs 2.7 d). The number of days to estrus from d 1 postweaning (5.4, 4.5 and 4.7 d, respectively), conception rate (60, 67 and 73%, respectively), farrowing rate (60, 67 and 73%, respectively) and litter size (10.6, 10.2 and 10.8, respectively) were not different (P greater than .05) for the three light regimens of 24:0, 12:12 and 0:24. Maximum serum levels of LH (5.4, 5.0 and 4.5 ng/ml, respectively) and estrogen (71.8, 63.3 and 60.4 pg/ml, respectively) were not different, nor were progesterone profile means (P greater than .05) for the sows in LD 24:0, 12:12 and 0:24. These data suggest that long photoperiods prolong manifestations of behavioral estrus in the sow.
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Reproductive seasonality in domestic sows kept outdoors without boars - J. M. Bassett, C. J. Bray, and C. E. Sharpe, Growth and Development Unit, University of Oxford. UK Reproduction (2001) 121, 613-629.
Plasma progesterone, LH and prolactin concentrations were measured twice a week in mature sows kept outdoors without boars in two experiments to examine whether perception of daylength change underlies seasonal infertility in domestic pigs. In Expt 1, melatonin implants inserted on 12 April or 22 May to block perception of the increasing daylength did not affect the oestrous cycle significantly, since only two untreated control sows became seasonally anoestrous. In Expt 2, all control sows became anoestrous for 131 ± 42.5 days (n = 11). Melatonin implants inserted at the spring equinox (n = 9) prevented seasonal anoestrus (P < 0.001), but timed daily oral melatonin administration was less effective (P < 0.05): 5 of 11 sows became anoestrous for 132 ± 45.6 days. In both experiments, there were significant low-amplitude seasonal rhythms in mean plasma prolactin and LH concentrations. Prolactin reached maximum concentrations 2-4 weeks before the summer solstice, whereas LH reached a nadir 4-6 weeks after the summer solstice. Neither anoestrus nor melatonin administration altered these patterns consistently. Endogenous plasma melatonin was higher (P < 0.001) during darkness (12.5 ng l-1) than during daytime (8.9 ng l-1) in untreated sows, but only clearly so during spring and summer. Melatonin implants increased mean daily plasma melatonin to 146 ng l-1, whereas melatonin fed at 15:00 h increased values to 40-60 ng l-1 2-4 h after administration, but daytime concentrations were unchanged. Melatonin administration, despite decreasing seasonal anoestrus, did not prevent the seasonal increase in plasma prolactin and had no significant effect on plasma LH; therefore, its role in regulating seasonal changes in the reproduction of domestic sows remains uncertain.
http://www.jrf-journals.org.uk/rep/121/rep1210613.htm

Environmental influences on the postpartum animal - RK Christenson. J Anim Sci 1980;51 Suppl 2:53-67.
Environmental influences on postpartum reproduction of the ewe, cow and sow are quite evident. Photoperiod predominantly controls the reproductive cycle of ewes lambing in the spring season and presents little problem in ewes lambing in the fall. The effect of hot ambient temperature and high humidity on ewes bred during anestrus and those bred after estrous cycles resume (late summer) needs study. In the southern regions of the United States hot ambient temperature and high humidity severely impair postpartum reproduction in cattle of European breeding. In the postpartum postweaned sow from southern states such as Minnesota, a marked reduction in reproduction during late summer and early fall has been reported. Presently, the physiological mechanisms by which hot ambient temperature and high humidity influence postpartum reproduction are not fully understood in the ewe and cow, and even less so in the sow. Hot temperatures and high humidity at the time of breeding of the ewe and cow reduce conception rates and subsequent pregnancy rates. Ewes and cows exposed to hot temperatures have increased rectal and uterine temperatures that may cause lower pregnancy rates. Altered hormonal levels and uterine blood flow have been associated with increased environmental, rectal and uterine temperatures.
Not On-line.

ABSTRACTS:

Seasonal effects on reproduction in the domestic sow in Finland : a herd record study - Peltoniemi OAT, Heinonen M, Leppävuori A, Love RJ. Acta vet. scand. 1999, 40, 133-144. Seasonal effects on fertility of the domestic sow were assessed by retrospective analysis of the Finnish national computerized data management system covering 1081 herds in 1993. Multivariate analyses were used, where the reproductive parameter of interest (repeat breeding, weaning to oestrus interval, age of gilts at first farrowing, litter size, culling due to anoestrus or no conception) was designed as the response variable. The months of the year (each month compared with January) and all herds and breed were included in the models as explanatory variables. The study demonstrated clear seasonal effects on various aspects of fertility in the domestic sow. The poorest reproductive performance was consistently observed in late summer and autumn and was demonstrated in a number of ways. Firstly, the gilts born between December and April were older (>5 days) at farrowing than those born during the rest of the year (p<0.01). Secondly, the risk that a culled sow would be culled due to anoestrus was significantly increased during the autumn months (Odds Ratio (OR) ranged from 1.10 to 1.36). Thirdly, the risk of a repeat breeding was higher from July to November (OR = 1.16). Risk of a prolonged weaning-to-oestrus beyond day 10 was the highest from August to October (OR ranged from 1.70 to 1.77). Risk of a sow to be culled due to no conception was the highest in January and February (weaned in October-November). In addition, descriptive data gathered in a slaughterhouse in 1993 (a subpopulation of the sows included in the herd records) suggest that incidence of inactive ovaries is increased in summer-autumn (p<0.05). In conclusion, a marked reduction in fertility of the domestic sow in Finland is reported between July and November.

Factors effecting reproduction in the pig: seasonal effects and restricted feeding of the pregnant gilt and sow - OA Peltoniemi, A Tast, and RJ Love, Department of Veterinary Clinical Sciences, University of Helsinki. Anim Reprod Sci 2000 Jul 2; 60-61:173-184.
Recent advances in research on seasonal infertility are discussed with a special focus on implications of the generally recommended restricted post-mating feeding strategy of the early pregnant gilt and sow for the physiology of seasonal infertility. The endocrinological basis of seasonal breeding of the wild and domestic pig is being clarified: as in other seasonal breeders, melatonin is relaying photoperiodic information about season to the pituitary-gonadal axis. Earlier confusion on this matter appears to have been caused by a lack of specificity of the melatonin assays employed. Group housing of the pregnant sow is becoming a common practice and, as an important environmental risk factor for seasonal infertility, may lead to an increase in the incidence of seasonal infertility in the future. After an initial progesterone-mediated beneficial effect on embryonic survival, a restricted post-mating feeding strategy may have a negative effect on maintenance of early pregnancy in the gilt and sow in the summer-autumn period. The endocrinological mechanism of seasonal disruption of pregnancy is yet to be determined. However, it is proposed that LH is reduced in the summer-autumn period and this reduction is amplified by the commonly applied restricted post-mating feeding strategy. These changes in LH secretion, although not as such inducing CL regression, may exert a progesterone-mediated detrimental effect on the capability of embryos to produce adequate embryonic signaling. This may lead to a seasonal disruption of pregnancy and return to oestrus 25-30 days after mating.

Physical mapping of porcine seasonality genes - TM Skinner, NL Lopez-Corrales, SI Anderson, M Yerle, and AL Archibald. Pig Gene Mapping Group, Roslin Institute, Scotland. Anim Biotechnol 1999;10(3):143-146.
Seasonal infertility in sows is a problem in the pig industry characterized by delayed onset of puberty in summer and decreased farrowing rate resulting from silent oestrus and aborted pregnancy. Summer infertility is thought to be influenced by heat, sunburn and stress. However, the strongest contributory factor is photoperiod. The difference in seasonality between wild boar and commercial pig breeds suggests that there may be a genetic component to this trait. The maps and associated molecular tools emerging from the pig genome project have created opportunities to examine the genetic component of seasonal infertility. We are identifying and mapping genes that are likely to be involved in biological clock mechanisms and the melatonin pathways as candidate seasonality genes.

Seasonal effects on fertility in gilts and sows - RJ Love, G Evans, and C Klupiec, Department of Animal Health, University of Sydney. J Reprod Fertil Suppl 1993;48:191-206.
The ancestral wild pig is a short day length seasonal breeder. The domestic pig appears to have retained some of this seasonality as evidenced by a reduction in fertility during the summer-autumn period. The most important aspect of this seasonality is a reduction in the number of mated sows that farrow. Many of these sows conceive and embryos develop normally for 20-25 days before pregnancy is terminated and the sow returns to oestrus (25-35 days after mating). In other species, transduction of photoperiodic information is achieved by release of melatonin during the dark period. In the pig, the pattern of melatonin secretion and the subsequent hypothalamo-pituitary-gonadal responses appear to be more complex. A relatively high light intensity is required for pigs to generate a distinct diurnal melatonin rhythm and they appear unable to respond appropriately to abrupt changes in photoperiod. Pigs on restricted feeding and maintained under long photoperiods (but not under short photoperiods) have higher concentrations of melatonin than do similarly maintained pigs fed ad libitum. Continuous release melatonin implants have a deleterious effect on farrowing rate, suggesting that the abnormally high melatonin concentrations observed in sows in summer-autumn play a role in the pathogenesis of seasonal infertility. Ad libitum feeding of sows during the first few weeks of pregnancy may prevent the increase in melatonin concentrations and so remove the seasonal influence on fertility. The pituitary response to different photoperiods is also somewhat confusing. Although there is some evidence of increased sensitivity to the negative feedback of ovarian steroids in the prepubertal gilts and weaned sows during summer-autumn, LH concentrations are increased in early pregnant sows. It is proposed that the failure of sows to maintain pregnancy in summer-autumn results from disruption of maternal recognition of pregnancy causing regression of the corpora lutea, loss of pregnancy and return of the sow to oestrus.

PRACTICAL APPLICATIONS:

Sourcebook on pork production alternatives available from U of M - A new publication designed to provide information on a variety of pork production and marketing options is available from the University of Minnesota. Its title is "Swine Sourcebook: Alternatives for Pork Producers." The sourcebook highlights a variety of production systems designed to maximize profit for small and medium-sized producers while helping to sustain the environment and rural communities. These systems include hoop structures, deep-bedded gestation systems, pasture farrowing, and other low-capital investment swine management techniques. Producers from throughout Minnesota have contacted the University of Minnesota Swine Center for information on these systems.
http://www.extension.umn.edu/extensionnews/1999/JP1035.html

The One-Litter Pasture System (Farrow-To-Finish) - David H. Bache, Extension Agricultural Economist and James R. Foster, Extension Swine Specialist, Purdue University
This is a pasture system in which gilts are farrowed once, then marketed. All pigs are raised and sold as market hogs except for a new group of gilts, which is saved back to continue the production cycle.
This is a good system for beginners and part-time farmers, or as a secondary enterprise on the farm.
http://pasture.ecn.purdue.edu/~epados/swine/pubs/id103.htm

Hooped Structures for Grow-Finish Swine & Swine System Options for Iowa - USDA, Sustainable Research and Education (SARE)
Learn more about outdoor alternatives for raising swine, including details on hog feeding, animal health, housing, bedding and marketing.
http://www.sare.org/tipsheet/tip5.htm
Swine Production Field Notes - USDA, Sustainable Research and Education (SARE)
This four-page newsletter focuses on SARE research in the North Central Region on alternative hog production systems such as hoop houses, deep-bed systems or raising pigs on pasture.
http://www.sare.org/tipsheet/tip5.htm

TLC secret ingredient to outside success - Jeff DeYoung, Iowa Pork Today
Kevin Graham is familiar with all-in, all-out, segregated early weaning, split-sex feeding and all the other pork industry buzzwords.
But there's one thing missing from those terms, something Graham says is the key to any hog operation -- tender loving care.
Most of Graham's hogs are outside on his Poweshiek County farm. He switched to PIC genetics in 1990 and wondered how the pigs would handle an Iowa winter.
http://www.iowafarmer.com/agnews/tlchogs.htm

Behavioural and physiological responses of naïve gilts to electric fences - Dr. Mark J. Kennedy, Cambridge University, Dr. Jeremy N. Marchant, Cambridge University and Prof. Donald M. Broom, Cambridge University.
Whereas the general public has the opinion that outdoor production, by its very nature, is a high welfare production system, this may not always be the case. A number of areas of welfare concern exist, that are specific to outdoor systems of production. For example, the expansion in use of outdoor pig production systems in the UK and Europe has led to increasing exposure of pigs to electric fencing. Little is known about the responses of pigs to these fences and, as a major factor of the animal's environment, they may have significant impact on welfare and productivity. Where rooting by the pig results in water troughs or housing arks touching the fence, the aversion of the pig to utilize that resource may result in particularly severe welfare compromises if not immediately noticed by the stockperson. Any resulting 'over-exposure' to electric current may subsequently make the pigs difficult to move between paddocks.
http://www.dmu.ac.uk/ln/Agriculture/pigs/electric.html

Sustainable indoor and outdoor production systems -
http://anm123c-1.asft.ttu.edu/default.htm