Effect of boar presence before and after weaning on estrus and ovulation in sows

Two hundred sixty-two sows were used to investigate the effects of boar exposure during the last week of nursing (BPRE) and after weaning (BPOST) on the return to estrus. Because approximately one-half of the sows were weaning their first litter, a third factor, primiparous vs multiparous (LITT), was considered in the statistical analysis. To evaluate the effect of treatment on ovarian activity, the sows were also blood-sampled twice weekly for 3 wk after weaning for the measurement of plasma progesterone concentrations as an index of ovulation. Boar exposure after weaning was the most important stimulus of early ovulation and estrus after weaning (P less than .001). A greater proportion of first-litter sows exhibited estrus later (P less than .02) and ovulated later (P less than .09) than did multiparous sows. First-litter sows were unaffected (P greater than .10) by boar exposure before weaning. Multiparous sows were sensitive to boar exposure during nursing. Maximal boar exposure for these sows (BPRE + BPOST) resulted in 95% of sows in estrus and ovulating within 20 d of weaning. No boar exposure resulted in 45% and 38% anestrus and anovulatory sows. Boar exposure, either before or after weaning, was effective in reducing the number of anestrus and anovulatory sows to between 15 to 30%. The effects of BPRE and BPOST on return to ovulation were additive and approximately equal.     

Lactation feed disappearance and weaning to estrus interval for sows fed spray-dried plasma

Four experiments involving 265, 410, 894, and 554 sows (Exp. 1 to 4, respectively) were conducted to determine the effect of spray-dried plasma (SDP) at 0 or 0.25% (Exp. 1 and 2) and 0 or 0.50% (Exp. 3 and 4) in lactation diets on average daily feed disappearance (FD), sum of sow BW, fetal and placental loss from d 110 gestation to weaning (SWL), litter size at weaning, litter weight at weaning, and average days from weaning to first estrus (WEI). Experiments 1, 3, and 4 were conducted during summer months, and Exp. 2 was conducted during fall to winter months. Experiment 1 used only parity 1 and parity 2 sows and Exp. 4 used only mature (>2 parities) sows, whereas Exp. 2 and 3 used all parity groups. Sows fed SDP in Exp. 1 had increased (P < 0.01) FD and a tendency for reduced (P = 0.06) SWL and WEI (P = 0.06). Sows fed SDP in Exp. 2 had a tendency for increased (P = 0.09) sow BW at weaning and reduced (P = 0.09) SWL, whereas other variables were not different between diets. Parity 1 and 2 sows fed SDP in Exp. 3 had increased (P < 0.01) FD, but mature sows fed SDP had reduced (P = 0.02) FD. Pig survival and litter size at weaning for all parity groups was not different between diets. The WEI for parity 1 sows fed SDP was reduced (P = 0.02) and tended to be reduced (P = 0.10) for mature sows fed SDP, but was not different between diets for parity 2 sows. More parity 1 sows fed SDP were detected (P = 0.01) in estrus 4 to 6 d after weaning, and fewer were detected (P < 0.01) in estrus 6 d after weaning compared with control parity 1 sows. In Exp. 4, FD was reduced (P < 0.01) for mature sows fed SDP; however, litter weight and average pig BW at weaning was increased (P < 0.01) with more (P < 0.01) marketable pigs (pig BW > 3.6 kg) weaned per litter. Relatively low dietary levels of SDP (0.25 to 0.50%) fed to parity 1 sows farrowed during summer months increased lactation FD and reduced WEI. Mature sows fed SDP during summer months consumed less lactation feed without compromising WEI, but had an increased litter weight, average pig BW, and number of marketable pigs at weaning.     

Morphine suppresses luteinizing hormone concentrations in transiently weaned sows and delays onset of estrus after weaning

Lactating sows were used to evaluate effects of morphine and suckling on secretion of LH and prolactin (PRL) and occurrence of estrus after weaning. In the first experiment, crossbred multiparous sows nursing 7.9 +/- .4 pigs per litter at 25.2 +/- .3 d of lactation were subjected to one of three treatments during the middle 8-h segment of a 24-h experimental period. Treatments were infusion (i.v.) of morphine (200 mg/h) with the litter present (n = 4) or transiently weaned (n = 4), or transient weaning of litters without morphine (n = 4). Transient weaning decreased (P less than .05) prolactin and increased (P less than .05) the frequency of LH pulses and average concentration of LH. Infusion of morphine caused transient hyperthermia and suppressed (P less than .05) LH release in two of four sows nursing litters and in four sows whose litters were absent. Infusion of morphine, in the presence or absence of litters, suppressed PRL during the middle and last 8-h segments. A second experiment was conducted to test the hypothesis that chronic administration of morphine delays onset of estrus after weaning. Primiparous Duroc sows were assigned at weaning (53 to 63 d postpartum) to receive morphine (n = 10) or saline (n = 11). Saline (1.5 ml) or morphine (75 mg) was administered s.c. three times a day for 5 d after weaning. Onset of estrus after weaning was delayed in sows given morphine compared with those given saline (9.7 +/- .4 vs 5.2 +/- .3 d, respectively; P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Ovarian follicular changes after weaning in sows.

Three experiments investigated ovarian follicular development in sows whose litters were weaned at 28 to 31 d of lactation. Unilateral ovariectomy near the time of weaning was used to assess early follicular characteristics and to identify those sows that would not return to estrus within 10 d after weaning. This allowed segregation of and exclusion from the study those sows that had a prolonged interval from weaning to first estrus. In Exp. 1, 82 and 72% of the large follicles that were marked at 48 or 72 h after weaning (10 sows per time point) were subsequently identified as corpora lutea. In Exp. 2, sows (seven to nine per time point) were unilaterally ovariectomized at 0, 6, 12, 18, 24, or 48 h after weaning, and follicular fluid was evaluated for changes in steroid concentrations. Progesterone concentrations in fluid from medium-sized (4 to 6 mm) follicles increased by 6 h after weaning and then declined through 24 h concomitant with increases in testosterone and estradiol. For Exp. 3, follicular fluid and granulosa cells from individual follicles were obtained from sows (seven to nine per time point) at 0, 6, and 24 h after weaning. In follicular fluid, insulin-like growth factor I (IGF-I) concentrations were not correlated (P greater than .05) with concentrations of progesterone, testosterone, or estradiol, or with granulosa cell production of estradiol during culture in androstenedione-supplemented medium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Decreased follicular size during late lactation caused by treatment with charcoal-treated follicular fluid delays onset of estrus and ovulation after weaning in sows

The weaning to estrus and weaning to ovulation intervals in sows are controlled by ovarian follicular growth after weaning. Longer intervals could be caused by smaller diameter follicles at weaning that take more time to reach a preovulatory size. We addressed this hypothesis by decreasing the diameter of follicular populations before weaning and then measuring follicular development and interval to estrus and ovulation after weaning. The posterior vena cava, cranial to the entry of the ovarian vein, was cathetered for blood sampling and infusion in 20 sows at 12 +/- 1 d after farrowing. Sows were assigned randomly to receive either 30 mL of charcoal-treated follicular fluid (FF, n = 9; a treatment known to decrease serum FSH and follicular diameter) or 30 mL of saline (n = 11) by venous infusion thrice daily (0700, 1500, and 2300 h) for 96 h beginning at 14 +/- 1 d after farrowing. Sows were weaned 48 h after the last infusion. Blood samples were collected for FSH analysis thrice daily beginning on the day of catheterization and continuing until ovulation. Follicular diameter was determined once daily by transrectal ultrasonography. A treatment x time interaction was detected for serum FSH (P < 0.001) and follicular diameter (P < 0.001) because serum FSH and the diameter of follicular populations decreased in FF sows during the infusion period. After the infusion period, serum FSH rebounded in FF sows, and follicles resumed growth but grew at the same rate as those of saline-treated sows, thus failing to achieve equivalent diameters relative to saline-treated sows on a given day after weaning. As a result, sows treated with FF had longer (P < 0.05) weaning to estrus (6.1 +/- 0.4 d) and weaning to ovulation (8.6 +/- 0.5 d) intervals compared with saline-treated sows (4.7 +/- 0.4 d and 7.2 +/- 0.4 d, respectively). We conclude that the diameter of the follicular population at weaning is one factor that controls interval to estrus and ovulation in sows. Small follicles at weaning cannot undergo compensatory growth and require additional time to reach a preovulatory size.     

The appearance of ovarian cysts in young sows after treatment with gonadotropin preparations for estrus induction

In 72 (46%) of 155 gilts discarded for genetic reasons after performance testing and housed under fattening conditions no heat could have been detected during the first 30 days. The gilts were assigned alternatingly to a control group and four different treatments of delayed puberty. The induction of puberty was carried out by injections of 1000 iu PMSG, 400 iu HCG and 2 mg oestradiol benzoate, 400 iu PMSG and 200 iu HCG and 800 iu PMSG and 400 iu HCG. If there was no estrus gilts were slaughtered 12 days later for examination of the ovaries. Those coming into estrus were slaughtered 8 days after disappearance of estrus. Estrus could be induced in 69 to 94% of the gilts, whereas 40% of the untreated showed estrus signs. After treatment with PMSG and HCG in 40 and 87% of the gilts cysts were found whereas none of the untreated and 26 and 29% of those treated with PMSG und HCG + oestradiol benzoate revealed ovarian cysts. In addition, those gilts that had come into estrus during the first 30 days were given injections of either 1000 iu PMSG or 800 iu PMSG and 400 iu HCG. The injections were made either on the 5th, 10th or 15th day of cycle. In both latter groups significantly more gilts showed standing heat than after treatment at cycle day 5. The results of inspection of the ovaries at slaughter and steroid hormones could not be assigned to a defined stage of the physiological ovarian cycle.(ABSTRACT TRUNCATED AT 250 WORDS)     

烯丙孕素内服溶液调控母猪同期发情的临床药效试验

为评价国产烯丙孕素内服溶液调控母猪同期发情的临床药效,选取性成熟后备母猪171头进行实验性临床试验和扩大临床试验,根据母猪发情及妊娠情况评价其临床药效。结果显示:实验性临床试验中,国产烯丙孕素内服溶液高(25 mg/d)、中(20 mg/d)、低(10 mg/d)剂量组以及空白对照组母猪从停药到发情的间隔时间分别为(3.45±0.81)d、(3.35±0.66)d、(5.21±2.65)d和(11.71±5.39)d,各用药组的发情间隔与空白对照组相比显著缩短(P0.05);扩大临床试验中,国产烯丙孕素内服溶液组和进口药物对照组的母猪在药物调控下均表现出良好的同期发情效果,发情间隔分别为(3.59±1.07)d和(3.75±1.22)d,发情率分别为96.72%(59/61)和98.33%(59/60)。研究结果表明,国产烯丙孕素内服溶液按推荐剂量(20 mg/d)连续给药18 d,可以使母猪达到良好的同期发情效果。     

丹系母猪断奶后发情和排卵规律的研究

母猪适时配种是提高受胎率的关键措施之一,而决定配种时间的主要依据是母猪排卵时间。本研究采用B超探测技术对56头不同胎龄的丹系高产母猪发情后的排卵规律进行观测研究。结果发现,母猪断奶后发情至排卵间隔平均为(29.28±8.14)h,排卵持续时间平均是(14.64±4.07)h;母猪断奶至发情间隔为4 d时,母猪发情至排卵间隔和排卵持续时间与其他组差异均显著(P0.05);当断奶至发情天数从2 d增加到5 d,发情至排卵间隔平均减少4.78 h,排卵持续时间平均减少2.39 h;哺乳期小于25 d的母猪断奶到发情间隔及排卵间隔与其他两组母猪均差异显著(P0.05);不同哺乳期的母猪排卵持续时间差异不显著(P0.05);胎次对母猪发情排卵时间存在一定的影响,高胎次母猪比低胎次母猪断奶后发情较迟,排卵持续时间也较长。     

提高夏季断奶母猪发情率的几点措施

<正>广东省地处热带和亚热带季风气候区,每年夏季,平均气温为28～29℃,6～8月份最高气温达到36～38℃,且持续较久,给养猪生产带来极为不利的影响,表现为母猪发情率等生产指标明显下降。断奶母猪发情率,与其他月份相比往往下降20%～40%,甚至出现暗发情或发情状态很不稳定,造成配种后返情率很高,一定程度上困扰养猪生产。这可以从我场2008年全年一个单元内断奶母猪的发情率进行比较(见表1)。鉴于此,笔者从防暑降温工作落实、改善母猪膘情、改变查情时间等方面谈谈提高断奶母猪发情率的一些看法。     

Effect of fractionated weaning on hormonal patterns and weaning to oestrus interval in primiparous sows

The effect of weaning the 4-5 heaviest piglets in the litter on day 33 of lactation and the remainder 2 days later (fractionated weaning) on plasma levels of prolactin, cortisol, oestradiol-17 beta (E2), progesterone (P4) and LH, as well as on the weaning to oestrus interval in primiparous sows was studied. Twelve crossbred sows were grouped into 6 pairs according to farrowing date and litter size. The litter of 1 sow in each pair (F) was weaned in 2 stages, and the other conventionally weaned at 35 days (C). Blood samples were collected via a permanent jugular vein catheter every 3 h from 9 a m to 9 p m daily throughout the experimental period, and intensively at 15 min intervals for 12 h on the day of first and final weaning and for 6 h on the day after each weaning. All sows were slaughtered following their first post-weaning oestrus and the reproductive organs were macroscopically examined. Lactational oestrus was not observed in any of the sows. Sows from 5 out of 6 pairs showed oestrus within 8 days of weaning and post-mortem examination showed normal ovulation. There was a tendency for the F sows to have a shorter weaning to oestrus interval, as compared with the C sows (5 of 6 pairs, 4.8 days v 5.6 days). The plasma levels of prolactin around weaning were not significantly different between the 2 groups. Within 6 h after final weaning, the prolactin concentrations decreased gradually from 7.6 and 8.7 to 1.6 and 1.7 microgram/l in the control and treatment groups, respectively. The plasma levels of cortisol, showing a diurnal rhythm (with the lowest level at 6 and/or 9 p m), did on no occasion differ between the 2 groups. On the day of final weaning, no diurnal rhythm was observed, with cortisol remaining high at 6 and 9 p m. The plasma levels of E2 and P4 were low until final weaning in both groups. After final weaning the E2 levels rose faster in the F sows than in the C sows, to 44.3 and 34.8 pmol/l, respectively, on day 2 (p less than 0.01). No significant differences in levels of plasma LH and the number of LH pulses were observed between the groups. After final weaning the average and base levels of LH and the number of LH pulse(s) increased significantly.     

Quantification of mammary gland tissue size and composition changes after weaning in sows

The objectives of this study were to characterize the tissue compositional changes in porcine mammary glands after weaning and to determine whether administration of estradiol alters the profile of these tissue changes. Forty-five primiparous sows were assigned randomly to one of two treatment groups after weaning, control or estrogen treated. Estrogen-treated sows received twice-daily injections of estradiol-17beta (0.125 mg/kg of BW); control sows received vehicle injections. Sows were weaned at d 21 of lactation and killed on either d 0 (d of weaning; n = 5) or on d 2, 3, 4, 5, or 7 after weaning (n = 4 per treatment on each day). Teat order relative to suckling behavior was observed on the day before weaning to determine which mammary glands the piglets suckled. Suckled and non-suckled glands were identified from the teat order observation, and individual mammary glands were collected at slaughter. Mammary glands were trimmed of skin and extraneous fat pad, individually weighed, and bisected to measure cross-sectional area. The remaining half of each gland was ground and stored at -20 degrees C for chemical analyses. Frozen tissue was used for measuring tissue DNA, DM, protein, fat, and ash contents. Suckled mammary glands of sows undergo significant and dramatic changes during the initial 7 d after weaning, with significant changes occurring even by d 2 after weaning. Mean cross-sectional area of parenchymal tissue in suckled mammary glands decreased from 59.7 +/- 2.1 cm2 on the day of weaning to 26.8 +/- 2.3 cm2 by d 7 after weaning (P < 0.0001). Mammary gland wet weight decreased from 485.9 +/- 22.0 g on the day of weaning to 151.5 +/- 24.8 g by d 7 after weaning (P < 0.0001), whereas DNA decreased from 838.8 +/- 46.2 g on the day of weaning to 278.4 +/- 52.5 g by d 7 after weaning (P < 0.0001). The changes in gland wet weight and DNA during the period of mammary gland involution in the sow represent loses of over two-thirds of the parenchymal mass and nearly two-thirds of the cells that were present on the day of weaning. Estrogen treatment did not affect overall mammary involution during the first 7 d after weaning. Mammary glands that were not suckled during lactation had no further loss of parenchymal tissue during the first 7 d after weaning. Mammary gland involution in the sow is a rapid process and is probably irreversible within 2 or 3 d after weaning.     

Biochemical and hematological changes in sows during estrus]

After the second and fourth parturition of piglets, ten clinically healthy sows, weaned on the second day of life, were subjected to examination two to three days before heat, during heat (defined by typical changes on the outer genitals and immobilization in the presence of a boar) and two days after insemination. During the morning hours, four hours after the last feeding, blood was taken from V. cava cranialis. Seventeen parameters were determined in whole blood and in the blood serum. In the period of oestrus, compared with the period two to three days before this period and two days after insemination, a marked increase was observed in the concentration of the serum levels of 11-hydroxycorticosteroids, iron, and in the activity of alanine aminotransferase. The activity of aspartate aminotransferase was increased in heat only in comparison with the period of the two days after insemination. The concentration of haemaglobin in whole blood was significantly increased in comparison with the period before oestrus and after insemination. Further, in the heat period -- as compared with the time before it -- a considerable drop was observed in the content of inorganic phosphorus and vitamin A. The possible mechanism of the occurrence of other changes is discussed.     

Relationship between body fat and postweaning interval to estrus in primiparous sows

Twenty-two primiparous Yorkshire sows were used to determine whether a minimal threshold of body fat exists below which the return to estrus is delayed. A second objective was to examine the relationship between body fat and interval from weaning to estrus in restricted-fed sows. During lactation (28 d), sows received 7, 9, 11 or 13 Mcal of ME daily to produce a range of sow body fatness at weaning. Intake of all dietary essentials except ME was similar for all sows. Litter size was adjusted to 10 pigs for all sows by d 3 postpartum. Each day from weaning to estrus, sows received 110 kcal ME per kg metabolic body weight plus 1,359 kcal ME per sow. Body fat was estimated at weaning and at first postweaning estrus by deuterium oxide dilution. Last rib backfat depth was determined ultrasonically 24 h postpartum and at weaning. Irrespective of dietary ME intake, percentage body fat at weaning (R2 = .24; P less than .05) and first postweaning estrus (R2 = .03; P greater than .50) accounted for only a small portion of variation in interval from weaning to estrus. Likewise, loss of backfat depth during lactation was not an accurate predictor of interval from weaning to estrus (R2 = .24; P less than .05). The low coefficients of determination (less than .25) suggest that body fat is a minor controller of postweaning interval to estrus. In contrast, dietary ME intake during lactation accounted for the largest portion of the variation (R2; = .48; P less than .01) in postweaning interval to estrus. We conclude that timing of postweaning estrus in primiparous sows is not dependent on a minimal threshold of body fat. Furthermore, effects of lactational ME intake on the postweaning interval to estrus are more pronounced than the effects of body fat.     

Suppression of cycling activity in sheep using parenteral progestagen treatment

The objective of this study was to evaluate the effect of two synthetic progestagen preparations Chlormadinone acetate (CAP, Chronosyn, Veterinaria AG Zürich) and Medroxyprogesterone acetate (MPA, Nadigest, G Streuli & Co. Uznach) on cycling activity and fertility in sheep. A flock of 28 non pregnant white alpine sheep was randomly divided into three groups, A (n = 10), B (n = 9) and C (n = 9). During a period of 4 weeks the cycling activity was confirmed by blood progesterone analysis. Thereafter, the animals of group A were treated with 50 mg CAP, those of group B with 140 mg MPA and those of group C with physiological saline solution. All injections were given intramuscularly. Suppression of endogenous progesterone secretion lasted from 28 to 49 days (mean = 39 days) in group A and from 42 to 70 days (mean = 50 days) in group B. The synchronization effect of both preparations was unsatisfactory as the occurrence of first estrus was distributed over a period of 3 weeks in group A and 4 weeks in group B. These findings could also be confirmed by the lambing period which lasted 52 days in group A and 36 days in group B. Control animals lambed within 9 days due to the synchronizing effect of the ram. The first fertile estrus was observed 36 days (group A) and 45 days (group B) after the treatment. In group A all 10 animals and in groups B and C 8 of 9 ewes each became pregnant. Parenteral progestagen application with CAP and MPA is a simple, safe and reversible method of estrus suppression in the sheep. The minimal suppressive duration of 4 (CAP) and 5 weeks (MPA) is not sufficient when a period of 3 months (alpine pasture period) is desired.     

Synchronized estrus and fertility of beef cows after weaning calves for short intervals

In Exp. 1, the objective was to determine if interval of separating calves from cows (24 or 48 h) immediately before insemination affects detection and precision of estrus and pregnancy rates of lactating beef cows implanted with norgestomet. Separation of calves from cows for 24 h (n = 418) lengthened intervals to estrus, did not affect precision of estrus, reduced success of detecting estrus and lowered pregnancy rates relative to positive controls (48 h separation, n = 508). Cows with poor body condition, and not suckled for 24 h, conceived at lower rates than cows with similar condition that were not suckled for 48 h. Adverse effects of separation for only 24 h on fertility are apparently due to inadequate intervals between estrus and insemination at 48 h after removing implants. In Exp. 2, the objective was to determine effects of separating calves from cows for 48 h immediately before insemination on detection and precision of estrus and on pregnancy rate of ovulatory lactating beef cows injected twice with prostaglandin F2 alpha (PGF2 alpha). Weaning increased detection of estrus but overall pregnancy rates did not differ between suckled (n = 256) and nonsuckled (n = 221) cows. But, weaning calves improved pregnancy rates of young (2 to 3 yr) cows and reduced fertility among middle (4 to 6 yr)-aged cows. Increased pregnancy rates after weaning calves for 48 h are due largely to greater detection of estrus and inseminating more cows.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influences of parity and level of feed intake on reproductive response to insulin administration after weaning in sows

In three experiments, the influence of insulin administered after weaning was examined in primiparous sows given extra feed or in primiparous compared to multiparous sows. In Exp. 1, 171 primiparous and 231 multiparous crossbred sows on a commercial farm were injected with 0.4 IU/kg BW insulin (Eli Lilly Lente Iletin II) or saline for 4 d beginning the day after weaning (d 0) and were fed 2.3 kg/d until mating. In Exp. 2, 153 primiparous sows from the same farm as those in Exp. 1 were injected with insulin or saline as in Exp. 1 and were fed 2.7 or 3.6 kg/d until mating. In Exp. 3, 63 primiparous crossbred sows were injected with insulin or saline as described above and fed either 2.3 or 4.5 kg/d for 5 d after weaning and were remated. On the commercial farm (Exp. 1 and 2), insulin administration increased percentage in estrus for primiparous sows compared to multiparous sows (treatment x parity interaction, P < 0.02) but tended to lower litter size in primiparous sows (treatment x parity interaction, P < 0.06). In Exp. 2, insulin combined with extra feed increased (P < 0.05) litter size by two pigs but tended (P < 0.07) to decrease farrowing rate in that group (treatment x feed interaction). Weaning-to-estrus interval, pregnancy rate, ovulation rate, and embryo survival were not influenced by treatment or feeding level (Exp. 3); however, postweaning intake and embryo survival were negatively related for saline-treated sows only (r = -0.55; P < 0.01), and backfat depth at weaning and embryo survival were positively related for insulin-treated sows only (r = 0.44; P < 0.05). Overall, insulin administration differentially influenced reproduction in primiparous sows and may have interacted with metabolic or nutritional state of the animal.