----start---- repro 9.23.98 Dr Parsons Swine Reproduction of the Swine "this lecture brought to you by the center for animal health and productivity (CAHP)" disclaimer: this lecture is NOT about the sex lives of your ex lovers -- it is about the reproductive anatomy, physiology, and pathology of the pig. Dr. Parsons will try to avoid making any Bill Clinton jokes. PA: 16th largest swine producing state in USA Lancaster: 5th largest swine dense county in the country [yada yada...there are a lot of opportunities in swine production medicine in this state...yada yada yada] Ok, bring on the information: Ground rules for swine veterinary medicine: remember that the swine veterinarian's patients are populations of animals, herds of animals, not generally individual patients. Furthermore, they aim to prevent rather than to treat problems. Reproductive problems on a farm are minimized if the farm has adequate: -biosecurity -nutrition -housing and facilities -management if you remember nothing else, remember that these things, if adequate, will really make problems minimal. To reduce anxiety level-- for the test, the handout is a resource. You are not responsible for all that info for the test. The ground rules will be you are responsible for what is said in lecture, and what is relevant in handout to what he said. Terminology: parity - number of litters a female has had (usually about 2 x age in years) gilt - young female up to and including first parity pigs sow - adult female swine boar - uncastrated male swine barrow - castrated male swine mating - breeding of a sow during estrus service - each time a sow receives the boar during a mating (there are multiple services per mating) prototypic swine farm facilities: adults: gestation barn, farrowing house young: nursery, grower, finisher We find adult swine mainly in gestation barn or farrowing house - group housing for sows in the gestation barn, and specialized individual farrowing pens in the farrowing house where they stay with the piglets about 3 wks to nurse the piglets. after weaning the sows return to gestation house to be bred. Then piglets move into the nursery, where they are usually grouped by litter in small pens designed to meet environmental needs of pigs, usually warm, plenty of food and water. as they grow, they need more room, so they go into the grower or grower/finisher facility - larger pens where they grow until they go to market or to gestation barn to breed. that's the swine 101 primer. Now, specifics of reproduction: objective: cover these topics: sow pregnancy piglets postpartum sow hormonal manipulations of sow boar infertility goal during these two hours is to get some basic information across. in Large animal block you'll get more of this, if you do it. SOW: anatomy puberty estrus cycle ovulation insemination and fertilization SOW ANATOMY: ovaries: multiple follicles/CLs present - discrete bumps present all over it. b/c pigs have litters, they obviously ovulate multiple simultaneous ova so require multiple follicles or CLs. uterus: horns can be up to 6 feet long during pregnancy! They are sort of folded in accordion style otherwise. So when you try to do u/s visualization of fetuses, there is a big area to look at, and if there is a dystocia you may need a REALLY long arm to reach back in there for the last piglet. cervix: transverse folds of the cervix grip the boar's corkscrew penis. The folds interdigitate with the ridge of the penis, allowing the sow to grip onto the penis and provide him with the pressure stimulus which makes him ejaculate. When you do AI in a sow and pass in a pipette, you can feel her gripping onto it. Especially when she's in heat. Vagina: largely nonremarkable (first time I heard a man say that...) Labia: edematous and hyperemic in estrus SOW - PUBERTY: triggered by onset of hypothalamic axis as it matures - increased pulsatile release of gonadotrophins. First estrus usually at about 6 mos old...depends on breed, environment, and season. What we find is that white pigs, or "maternal" breeds tend to reach puberty earlier and exhibit stronger signs of estrus. we try to target breeding gilts at 8 mos of age, on 3rd estrus cycle, b/c with each ovulation, the number of follicles ovulated increasees until maximum fecundity at 2-4 yrs. First ovulation is also often behaviorally "silent" due to lack of progesterone priming. YOu don't want to breed too early either, b/c growing animals are diverting nutrition to growth. If you wait til 8 mos, sow will be pretty much over the growth peak and will produce an acceptable number of follicles and will be able to support the litter. you can hasten puberty onset in gilts within 1 month of puberty by: -interaction with boars or other estrus females (pheromone mediated) -mild forms of stress such as "mixing" with other groups, or transportation -exogenous gonadotrophins - PG600 - PMSG and HCG - but cost prohibitive you can delay puberty onset by: -season: sows have seasonal anestrus; when they are born will affect when they come into heat -ambient temperature -diet -housing SOW- ESTRUS CYCLE: 21 days long: estrus metestrus diestrus proestrus we can define follicular and luteal phase by hormonal dominance - luteal phase is metestrus and diestrus, follicular phase is proestrus and estrus. the sow is polyestrous as you know; they do have periods of lactational anestrus which ceases 4 to 7 days after weaning. by removing the pigs from mom, you promote return to estrus. Most breeding programs are designed around this fact. Pigs have mild seasonal anestrus in the summer time. There is extended, delayed returned to estrus after weaning, and decreased conception rates. You have to have large numbers of animals together to see this; it is a fairly subtle effect; only noticed maybe 10 yrs ago. Estrus: triggered by preovulatory LH surge. estrus is 2-3 days in duration with ovulation in last third often defined as "standing heat" Metestrus: (beginning of luteal phase) progesterone rises to maximum levels over first 5-7 days, and is maintained for a while - metestrus lasts til about day 7 Diestrus: maximum luteal function - lasts til day 15 or 16 before day 12, CL is refractory to PGF uterine release of PGF starts on day 14, to trigger lysis of CL day 14-16 progesterone rapidly drops estrogen is luteotrophic in sow - exogenous estrogens prolong diestrus, promote the luteal phase (such as zoralanone toxin in feed...) Proestrus: day 17 rapid degradation of CL sow shows interest in boar but won't stand start to get follicular maturation waves of FSH produced, which feed bak to pituitary, ultimately triggering LH surge... Post-farrowing estrus: historical artifact observation was that sows could be found in standing heat 2-3 days postfarrowing, but weren't ovulating and implantation was impossible. was attributed to estrogens ingested with placenta. no practical significance to this and most modern farms do not allow sow access to the placenta. Behavior of Estrus: important clinically - you have to detect heat so you can breed animals at the right time! lasts 60 hrs in sows - 48 hrs in gilts standing to be mounted by boar - most definitive sign sow assumes rigid stance in response to contact with the boar, or sometimes just pressure on rump from the herdsperson. her ears stand perked up. This response is seriously enhanced or triggered by pheromones from the boar, so when doing heat detection you try to walk boar through the barn in front of the sows, and follow along behind sows pressing on their butts. Or, spray the boar in a can stuff in the barn. vulvar lips are swollen and red with a thin mucous d/c behavioral signs are less pronounced in gilts Another good indicator is the texture of the mucous at the vulva - it should be thin. Sow Estrus Detection: check sows once a day, gilts twice a day (b/c estrus is shorter) -limited boar contact (allowing boar to walk down and have nose:nose contact with sow)(watch her interaction with boar) -back pressure test -boar mate spray (not really used much except as gag gift) Most modern systems use hand matings where boar is brought to sow personally, or they use AI - deficient estrus detection is pretty much the most important cause of "infertility" in herds using these systems. Failing to recognize animals in heat is the problem. In problem herds we recommend heat-checking twice a day to increase probability of heat detection. Really, those who do this day in and day out are best at it. The best sign of an animal being in heat is a change in behavior. Some sows get more active, some get less active, many go off feed when they come into heat. But if you know how a particular sow normally acts, you can see when she's not acting that way. Vets who visit farm only to find a problem aren't the best at it! SOW- OVULATION: 36-42 hrs after onset of standing heat in sows (12 hrs earlier in gilts) 10-20 ova are shed by the sow (10-15 in gilt) 65-75% embryonic survival rate results in about 8-12 piglets/litter high ovulation rates do NOT yield greater litter size - placental space limitations regulate litter size Optimum fertility occurs 18 to 42 hrs after onset of standing heat It requires live sperm in the tract during ovulation Breeding more than 10 hours after ovulation results in reduced fertility It takes about 8 hrs for sperm to get through tract to site of ovulation, so it is good to breed animal right before ovulation. Of course, in commercial setting, if you heat check once daily, your determination of onset of estrus is +/- 24 hrs so this induces a margin of error. The ultimate way of looking for response to "back pressure" by the way is sitting on top of the sow. Some mating systems require herdsman to sit on sow while infusing semen via AI into sow, to increase fertility by more closely simulating natural breeding. SOW INSEMINATION AND FERTILIZATION: breeding schedules target: at least 3 services per mating - dramatically increases conception rates breed sows at least once every 24 hrs during standing heat. additional service can be added at a 12 hr interval. exact placement will depend on quality of heat detection in the herd. gilts we recommend breeding every 12 hrs during standing heat, reflecting her shorter estrus and earlier ovulation So, there are many different paradigms for this,b ut most simply we breed q 24 hrs during standing estrus and add services at 12 hr intervals as per needs of herd. If you are great at heat detection, you will have a delay prior to ovulation and you don't want to inseminate immediately - you will wait 12-24 hrs before first insemination. If heat detection isn't as good, and you are missing early subtle signs of heat, you will start right away. Heterospermic Mating: farrowing rates increase when different boars are used during different services of the same mating, for some reason. this can preclude or delay the identification of infertile boars, though. sometimes they will mix semen up front and do AI with mixed semen. but when first using a boar, should use him singly to check fertility first. PREGNANCY: the embryo: day 2 (post ovulation) - fetilized ovum at 4 cell stage enters the uterus day 9-12 - intrauterine migration equalizes number/horn, with efficient distribution and spacing of embryos. pigs at the ends of the horn are usually the runts, b/c there is less placental nutrition at the end of the horn. day 12 - blastocyst produces estrogen (luteotrophic - maintains pregnancy). CLs are required throughout pregnancy (lysis will terminate pregnancy). Estrogen blocks release of PGF into uterine vein. minimum of 4 embryos required to maintain pregnancy - to maintain luteotrophic effect. day 15-17 - attachment to placenta occurs - diffuse, microcotyledonary epitheliochorial type. day 30 - fetal skeleton starts to develop. ---break--- SOW: PREGNANCY DETECTION commonly used methods: observation: -failure to return to estrus at 17-21 days (key thing) -"piggy" appearance at about 3 mos -potbellied abdomen, enlarged udder ultrasonography (A mode) - as the price of realtime imaging decreases, we see this used more and more, but it isn't really used that much yet. -beam reflects off solid/liquid interface (don't confuse bladder w/uterus!) -fetal fluid in pregnant uterus -used at 35 days routinely PARTURITION (farrowing) occurs after 115 days (3 mos, 3 weeks, 3days) triggered by fetal ACTH and subsequent cortisol release cortisol stimulates release of PGF and luteolysis progesterone drops 24 hrs prepartum and myometrial activity increases -sow shows increased restlessness, goes off feed, shows nesting behavior -mammary glands distended with milk -engagement of first piglet into cervix causes release of oxytocin and more myometrial contractions -fetuses are brought to cervix prior to rupture of umbilical cord or separation of placenta length of parturiation: 20 min - 12 hrs, avg 4 hrs piglet should arrive q 10-15 min; intervene if 20-30 min go by after a piglet without another piglet retained placenta is uncommon in pigs signs of retained piglet: restlessness, anorexia, straining, fetid d/c. DYSTOCIA: rare in sow - under 1% of all farrowings need intervention (if higher than that, other problem on farm probably exists) signs: straining without delivery of piglets interval of >1 hr since birth of last pig delivery of 1 or 2 pigs, then cessation of labor foul vaginal d/c, anorexia and ill sow primary cause: uterine inertia - primary (failure to initiate contractions) or secondary (uterine exhaustion) - secondary is more common in pigs. other less common causes: obstruction (tumor, etc) treatment: if blockage - correct it, correct malpresentation of fetus, etc initiate contractions with oxytocin - give 10-30 IU 3 time at 2 hr units, injected into the vulva. c-section may be considered - rarely elected in commercial field situations due to cost, anesthesia, and postop care required. normal parameters for baby piglets: piglets born at 1% of mature weight they lack reserves of brown fat or glycogen to maintain body temperature they are born as really cute little fuzzy things and they grow up into big old pigs. piglets require: warm, dry environment (95 F) nursing within 10-35 min colostrum for energy ad antibodies if not nursing -give glucose or karo and put under heat lamp - might then be able to nurse. temperature requirement decreases by 0.5 degree per day over first 8 weeks of life. POSTPARTUM: lochia normal during first week rapid uterine involution 21 - 28 days lactational anestrus until weaning weaning usually at 21 days (before that often results in reduced fertility) return to service 4-7 days postweaning summer time or inadequate nutrition can delay return to estrus and reduce fertility HORMONAL MANIPULATION OF SOWS: induction of farrowing induction of ovulation luteolysis/abortion why induce farrowing? to synchronize them, so more are going on during day, when people are around to deal with complications; also to maximize opportunity for cross fostering large litters. how do you induce farrowing? give 10-12 mg PGF (Lutalyse) not before day 112 (or piglets are premature) parturition occurs 24-30 hrs later 95% will farrow within 48 hrs why induce ovulation? for synchronization of estrus, especially in gilts. We want to promote smooth flow of pigs through the system. how do we induce ovulation? PG600 (PMSG and HCG) - expensive Regumate - a progesterone analog not approved for use in swine in this country. we've used it extralabel and it works, but not as well as PG600. how do we abort sows? We use PGF given after day 12 or during gestation to lyse CL and return her to estrus. This is effective for abortion, but NOT for synchronization like it is in the cow. This is b/c CL isn't responsive until after day 12, and endogenous PGF is released b/w day 14 and 16, so there is no significant change in cycle length by using it. You can't short-cycle the sow like you can with the cow. So we only use it for abortions. BOAR STUFF: we are running late; this will be brief. anatomy, puberty,mating behavior, sperm production, AI ANATOMY OF THE BOAR: really big scrotum. large testes. long axis is vertical/oblique. The testes are big b/c sows have litters, and you need more viable sperm to result in successful mating. the testes to body size ratio is pretty big in the pig. epididymis: tail - dorsal, head - ventral; body - cranial and medial, hard to palpate. ductus deferens: lacks ampulla, empties directly into the urethra bulbourethral glands: secretes thick gel portion of ejaculate Prepuce: there is a dorsal preputial diverticulum which has a possible role in disease transmission. this is a little pocket of space dorsal to the area where the penis actually is. penis: highlight of boar's anatomy (sure, the vagina is nothing much to speak of, but he is going on and on about the penis. hmmm.) fibroelastic with no glans; corkscrew - counter clockwise coil at the end; locks into transverse folds of cervix. erection - occurs due to relaxation of sigmoid flexure. ejaculation largely stimulated by pressure. BOAR PUBERTY: more gradual than in gilts 5 mos - sufficient sperm for fertilization 8 mos - sufficient sperm for regular breeding (3-5 x per week) 18 mos - adult sperm numbers achieved raised in groups, boars have earlier onset of puberty and more aggressive libido. BOAR MATING BEHAVIOR: nasonasal or nasogenital contact with sow grunting, nuzzling, and chomping with copious salivation triggers reflex stance (lordosis) of sow multiple false mounts will occur ("gloved hand" of hand mating systems will assist boar with intromission) penis locks into cervix ejaculation occurs over a 4-6 minute period (you can tell when he is ejaculating due to winking of his anus and spinning of his tail) then he will dismount BOAR USAGE: not more than once/day or 4x/week; less for young boars rule of thumb in hand mating systems: 1 boar per 20 sows in herd. AI (artificial insemination) an ongoing revolution in the swine industry over past 2-3 years advantages: -sow:boar ratio increases to 100-200 sows/boar -rapid importation of improved genetics -more uniform products -minimum biological risk (of bringing disease onto farm) development of off-site boar studs: -extended semen remains viable at room temperature for days -ready availability of overnight delivery how is it done? boar is trained to mount a dummy then boar is collected manually by technicians semen is checked for morphology and motility, density is determined spectroscopically, then it is extended and stored in 80-100 ml aliquots of 3-5 billion cells per aliquot. INFERTILITY: infectious or noninfectious infectious: viral - most common bacterial protozoal SMEDI syndrome: stillbirths, mummies, embryonic death, infertility - this is what is seen with most viral, and some bacterial, syndromes. This is a historical term that was used before the advent of adequate diagnostic tools. Now, we can hopefully find etiological agents and get a specific diagnosis of the problem. largely, what determines what you see is the time during gestation that the animal is infected. slide: dead piglets from parvovirus outbreak - parvo is usually vaccinated for so you rarely see it. on the left is a stillborn piglet, and on the right is a mummified fetus and an "early embryonic death" embryo. again, manifestation of signs depends on time during gestion that infection occurs. infection prior to implantation (up to 15-17 days gestation) will result in return to heat at expected time (pregnancy not maintained) infection prior to skeletal development (30 days) but after implantation, will result in early embryonic death and resorption of litter, with delayed return to estrus. infection after 40 days, after skeletal development - results in mummification and maceration of fetuses - no resorption. if enough die, results in abortion. if only a few die, they are "born" that way. infection after fetus becomes immunocompetent (70-90 days)- piglets may survive but some will be stillborn or weak at birth abortions occur during last 2 trimesters noninfectious: long list in handout, rarely dealt with, won't be covered, you have list to refer to in the future. there is basically one general concept left here to discuss - PRRS, porcine respiratory and reproductive syndrome - and we do not have time to discuss it, so it is strongly recommended that you reaad the handout at some point about that. ----end----