Post-weaning Estrus Research Articles

The effects of zearalenone on reproduction in swine. II. The effect on puberty attainment and postweaning rebreeding performance

Eighty-five prepuberal, crossbred gilts received, ad libitum, a diet containing 0 or 10 ppm purified zearalenone for 30 d beginning at 145 to 193 d of age. At the end of this period all gilts were placed on the control diet and exposed daily to a mature boar for 60 d. Within 3 to 5 d of zearalenone ingestion, gilts showed marked vulval swelling and reddening, which continued for the 30-d feeding period. Thereafter symptoms slowly subsided. Zearalenone treated gilts showed first estrus significantly later than controls (P < 0.05), but the proportion of gilts showing estrus within 60 d of boar exposure was similar (P > 0.05). The length of the first estrous cycle was not affected by the ingestion of zearalenone before puberty (P > 0.05). In a second study, 65 multiparous, crossbred sows were full-fed twice daily a ration containing 0 or 10 ppm of purified zearalenone beginning 14 d before weaning. Postweaning, all sows were fed the control diet, were checked for estrus daily, and inseminated at the first postweaning estrus. Neither sows nor gilts from their litters exhibited signs of hyperestrogenism during treatment. Weaning to estrus interval was significantly extended in zearalenone treated sows (P < 0.05), but all other variables of fertility assessed were similar. These data suggest that zearalenone ingestion before puberty delays the stimulation of puberty associated with boar exposure, but does not affect subsequent cyclicity if zearalenone is removed from the ration. Similarly, zearalenone ingestion during lactation delays the return to estrus after weaning, but does not affect subsequent fertility when removed from the ration at weaning.

Effect of lactation and rebreeding phase energy intake on primiparous and multiparous sow performance.

Fifty-three primiparous sows were used to study the effects of a high-energy, fat-supplemented diet on sow lactation and rebreeding performance. Sows received either a low [Lo, 12.5 Mcal metabolizable energy (ME)/d] or high (Hi, 16.0 Mcal ME/d) energy sorghum-soybean diet during a 28-d lactation. At weaning, sows were randomly allotted, within lactation treatment, to a low (lo, 5.54 Mcal ME/d) or high (hi, 9.61 Mcal ME/d) energy sorghum-soybean diet until the day of first postweaning estrus. Primiparous sows fed Lo weaned larger (P less than .05) litters than sows fed Hi; however, average pig weight was not affected by lactation treatments. Primiparous sows fed Hi had more backfat at weaning (P less than .01) than Lo sows. In contrast, sow weight was not affected by dietary treatments. Neither lactation nor rebreeding treatments influenced days to rebreeding; however, an interaction (P less than .01) was observed. Mean days from weaning to rebreeding for Lolo, Lohi, Hilo and Hihi sows were 10.0, 7.6, 6.9 and 17.1, respectively. Forty sows were maintained on the same dietary treatments during their second parity. Sows receiving Lo during their second parity farrowed and weaned more (P less than .05) pigs than Hi sows. Multiparous sows fed Hi nursed heavier (P less than .05) pigs on d 21 of lactation and at weaning compared with Lo sows. Sows fed Hi were heavier (P less than .05) and had more (P less than .01) backfat at weaning of their second litter compared to Lo sows. Days to postweaning estrus were not affected by lactation or rebreeding diets. Mean length of the second parity rebreeding interval for Lolo, Lohi, Hilo and Hihi sows was 6.2, 10.2, 7.0 and 10.5 d, respectively. These results suggest that feeding levels during lactation of 12.5 Mcal ME/d or higher supported adequate rebreeding performance. Postweaning feeding levels did not influence days to first estrus. Feeding a high energy diet continuously throughout the lactation and rebreeding phases in primiparous sows may lengthen the postweaning interval to estrus.

Interval to first postweaning estrus and causes for leaving the breeding herd in Large White, Landrace, Yorkshire and Chester White females after three parities.

Three hundred and five Large White (LW, 93), Landrace (L, 92), Yorkshire (Y, 69) and Chester White (CW, 51) gilts produced at the Roman L. Hruska U.S. Meat Animal Research Center over 3 yr with 15 to 41 gilts per breed group per year were housed in total confinement and mated to farrow at 1 yr of age. After 28 to 30 d lactation, piglets were weaned and all females were observed for estrus daily for 30 d. During the year that each gilt initially farrowed, she was mated to produce a second and third litter if she returned to estrus within 30 d after piglet removal. Interval from weaning (d 0) to estrus and reason for leaving the breeding herd were recorded for each animal. Interval from weaning to estrus was influenced by breed (P less than .01), parity (P less than .01) and interaction between breed and parity (P less than .01). Intervals from weaning to estrus, in first parity females which exhibited estrus, were 7.8, 6.6, 9.3 and 14.0 d for the LW, L, Y and CW breeds. Intervals for all females after the second litter were 6.8, 4.9, 8.0 and 9.1 d, and after the third litter 6.4, 5.2, 8.3 and 10.1 d for the LW, L, Y and CW breeds. Breed, parity and year (P less than .01) affected the number of females not exhibiting estrus. Percentages of females not exhibiting estrus were 6.5, 18.7, 37.7 and 23.5 for the LW, L, Y and CW breeds and 16.1, 2.3 and 2.0 for sows after the first, second and third parities.(ABSTRACT TRUNCATED AT 250 WORDS)

The relationship between plasma levels of estradiol-17β, progesterone and the consistency of the cervix in the sow

The object of this investigation was to estimate the peripheral plasma levels of estradiol-17β and progesterone and the consistency of the cervix by rectal palpation of sows before, during and after post-weaning estrus. The tonicity of the cervix increased from approximately 4 days before the onset of heat, became firmest during estrus, and became softer again during the post-estrual period. The levels of estradiol increased before the onset of heat and reached maximum levels on the day preceding heat, then decreased to baseline. The progesterone levels remained low until post-estrus, then increased rapidly. One sow which did not come in heat constantly had a soft cervix and low hormone levels. It is concluded that estrogen might be implicated in the increased tonicity of the cervix and that rectal examination of the cervix provides valuable information on ovarian function.

Evidence for ovulation and fertilization in beef cows with short estrous cycles

Calves were weaned from 15 Polled hereford anestrous cows 25 to 42 days after calving. In eight cows the uterus was flushed on day 6 or 8 after the first postweaning estrus (day 0), and in seven cows the oviduct ipsilateral to the ovary containing an ovulation papilla was removed and flushed on day 3. One ovum (morula) was recovered from the eight uterine flushings, while six ova were recovered from six of the seven oviductal flushings. Of the six, three were fertilized (4 to 8 cells), two unfertilized and only the broken zona pellucida of one was recovered. An ovulation papilla was observed in all cows at the time of oviduct removal. Six of the 15 cows had cycles less than 12 days, and from four of those six fertilized ova were recovered. The data indicate that previously anestrous cows ovulate at their first postweaning estrus and the ova released are capable of being fertilized. Failure to maintain pregnancy appears to be due to early corpus luteum regression.

EFFECT OF BIOTIN SUPPLEMENTATION ON REPRODUCTIVE PERFORMANCE AND FOOT LESIONS IN SWINE

Two experiments, using 237 gilts and primi-parous sows of Lacombe and Yorkshire breeding, were conducted during the winter and summer months to study the effect of biotin supplementation (200 and 300 μg/kg in exps. 1 and 2) of barley-wheat-soy gestation and lactation diets on reproductive performance and incidence of foot lesions in swine. The control and supplemented groups did not significantly differ in weight change during gestation or lactation in either breed. The number of pigs born alive, mean birth weight (kg), 21 -day weight gain (kg) and number of pigs weaned (5 wk) per litter were 9.18, 1.38, 4.15, 8.0 and 8.97, 1.35, 4.14, and 7.6, respectively, for control and supplemented groups and did not differ significantly between treatments. The time to post-weaning estrus was similar (7.62 vs. 7.72 days) for both groups. Also, this interval was not significantly different (8.33 vs. 7.10 days) between Lacombes and Yorkshires. The foot lesions observed in both gilts and sows were composed of vertical and horizontal cracks including hemorrhagic ulcers on the hoof surface. Biotin supplementation did not prevent the incidence of these lesions; however, the severity was slightly decreased and this response was similar in both gilts and sows of both breeds.

FACTORS AFFECTING THE ONSET OF PUBERTY, POST-WEANING ESTRUS AND BLOOD HORMONE LEVELS OF LACOMBE GILTS

Lacombe gilts which were exposed to a boar at 55 kg liveweight reached puberty at an average age of 145 days (range 102–200 days) and an average weight of 78.9 kg (range 55–118 kg). Restricting energy intake to 85% of free-choice intake from 45 to 90 kg increased the age at 90 kg by approximately 7 days but decreased the age at puberty by 9 days. Level of energy intake before service had no significant effect on the number of pigs born or weaned per litter. The overall average number of pigs born alive was 9.5, with 7.8 weaned per litter. Ninety-three percent of the gilts were rebred and the average time taken to post-weaning estrus was 8 days. Depriving the gilts of feed and water on the day of weaning did not significantly affect the time taken to return to estrus or influence the levels of any of the blood hormones measured. In sows that came into heat within 10 days of weaning, peak plasma concentrations of follicle stimulating hormone (FSH) occurred on the day of weaning or the 1st day after weaning, and plasma concentrations of luteinizing hormone (LH) and estradiol were low at weaning but reached peak concentrations on the day of estrus or the day prior to estrus. Patterns of plasma FSH, LH and estradiol were different in sows that failed to show an early post-weaning estrus.

ESTRUS AND PREGNANCY IN PRIMIPAROUS SOWS TREATED WITH PREGNANT MARE’S SERUM GONADOTROPIN OR ESTRADIOL-17β AND PROGESTERONE

Over a 3-yr period, the effectiveness of pregnant mare’s serum gonadotropin (PMSG-1,500 IU) or estradiol-17β (1 mg) plus progesterone (2 mg) for the stimulation of post-weaning estrus and conception in primiparous sows from a herd with a history of post-weaning anestrus was evaluated. On the day after weaning, an intramuscular (i.m.) injection of PMSG or steroids was given to 49 and 51 sows, respectively. Fifty untreated sows served as controls. Treated sows in estrus by day 8 and control sows in estrus by day 40 were bred on the 2nd day of estrus. Serviced sows were killed at day 25 of pregnancy or on the day after return to estrus. The remaining sows were killed when in estrus or between days 41 and 45 after weaning. By day 8, more (P &lt; 0.01) PMSG-treated (98.0%) sows were in estrus than either the steroid-treated (64.7%) or control (66.0%) sows. By day 14, fewer (P &lt; 0.05) steroid-treated than control sows were in estrus (64.7 vs. 82.0%). The mean interval between weaning and estrus for sows in estrus by day 8 was less for the PMSG (P &lt; 0.01) - and steroid (P &lt; 0.05) - treated sows than for the control sows (3.83 ± 0.11 and 4.36 ± 0.28 vs. 5.12 ± 0.23 days). For the steroid-treated and control sows in estrus after day 8, the mean time to estrus was 34.6 ± 3.5 and 21.2 ± 2.8 days, respectively (P &lt; 0.01). Pregnancy rates were similar for the PMSG and steroid treatments (57.1 and 47.0%), and lower than for the control sows (84.0%). The PMSG-treated animals had larger litters (16.4 ± 1.0 embryos) than either the steroid-treated (12.8 ± 1.1 embryos) or control (11.3 ± 0.8 embryos) animals.

OVULATION RATE AND WEIGHT OF THE REPRODUCTIVE ORGANS OF YORKSHIRE AND LACOMBE SWINE

Ovulation rates were determined in 41 Yorkshire, 46 Lacombe and 26 Lacombe × Yorkshire gilts, and in 37 Yorkshire and 32 Lacombe primiparous sows. Ovulation rates in gilts remained constant from puberty to the fifth estrus. For Yorkshire, Lacombe and crossbred gilts the ovulation rates were 12.2, 14.4 and 14.0, respectively. The ovulation rates in Yorkshire and Lacombe sows were the same (17.0). In sows, ovulation rate increased significantly from the first to second post-weaning estrus (15.4 vs. 17.5). In Yorkshire gilts, ovarian and uterine weights were significantly less than in Lacombe gilts. Within breeds, ovarian weight remained similar while uterine weight increased (P &lt; 0.05) from the first to second estrus. In sows, ovarian weight, which was similar for both breeds, increased significantly from the first to second post-weaning estrus. Uterine weight in Lacombe sows was significantly greater than in Yorkshire sows, and increased (P &lt; 0.05) from the first to third post-weaning estrus. In Yorkshire sows uterine weight remained constant over the first three estrous periods after weaning.

Factors affecting sow farrowing interval.

Sows mated on the first postweaning estrus following a short lactation have shown reduced reproductive performance in previous studies (Self and Grummer, 1958; Smidt, Scheven and Steinbach, 1965; Moody et al., 1969). Research on the problems encountered in attempts to reduce sow farrowing interval are worthy of further investigation because their solutions will increase the reproductive efficiency of the sow. Three experiments were conducted (1) to study the effects of lactation length on subsequent ovulation rate and embryo survival; (2) to determine the effects of flushing and stress after mating on reproductive traits at 25 days postcoitum; and (3) to collect further information on the effect of mating methods on the reproductive performance of sows mated on the first estrus following a short lactation. Yorkshire × Landrace crossbred sows were used in three experiments and they were mated to Poland China boars. The sows had previously farrowed from one to eight litters (parity).

Fertility level of sows superovulated at post-weaning estrus.

Fertility level of sows superovulated at post-weaning estrus.

Influences of litter size and nursing period on the recurrence of post-weaning estrus and subsequent fertility in rats

Influences of litter size and nursing period on the recurrence of post-weaning estrus and subsequent fertility in rats