Effect of dietary beta-carotene on the early embryonic development and uterine fluid composition of gilts

The role of beta-carotene in reproduction was investigated in gilts assigned to three dietary supplementations: VA (4000 IU vitamin A); VA + VA (4000 IU + 8300 IU); VA + BC (4000 IU + 100 mg beta-carotene) per kg diet for 14 weeks. Gilts were slaughtered at day 12 of gestation. In the VA + BC group, number of corpora lutea was lowest, but the number of embryos was greatest, resulting in a non-significant decreased prenatal mortality (p<0.07). The proportion of less developed spherical and tubular embryos compared with filamentous was greatest in the VA + BC group (p<0.01). No differences were observed for vitamin A and retinal binding protein (RBP) in the uterine fluid. When animals were grouped according to the development of blastocysts, vitamin A and RBP levels were higher in the VA + BC group with only filamentous embryos (p<0.01). This indicates that the supplementation of beta-carotene to gilts might affect embryonic losses possibly because of slower alterations in the uterine environment, resulting in a higher and less variable number of embryos, despite an apparently more heterogeneous development.     

Effect of human chorionic gonadotropin on preovulatory luteinizing hormone surge and ovarian hormone secretion in gilts

The influence of varying doses of human chorionic gonadotropin (hCG) on the preovulatory luteinizing hormone (LH) surge, estradiol-17 beta (E2) and progesterone (P4) was studied in synchronized gilts. Altrenogest (AT) was fed (15 mg X head-1 X d-1) to 24 cyclic gilts for 14 d. Pregnant mares serum gonadotropin (PMSG; 750 IU) was given im on the last day of AT feeding. The gilts were then assigned to one of four groups (n = 6): saline (I), 500 IU hCG (II), 1,000 IU hCG (III) and 1,500 IU hCG (IV). Human chorionic gonadotropin or saline was injected im 72 h after PMSG. No differences in ovulation rate or time from last feeding of AT to occurrence of estrus were observed. All gilts in Groups I and II expressed a preovulatory LH surge compared with only four of six and three of six in Groups III and IV, respectively. All groups treated with hCG showed a rapid drop (P less than .01) in plasma levels of E2 11, 17, 23 h after hCG injection when compared with the control group (35 h). The hCG-treated gilts exhibited elevated P4 concentrations 12 h earlier than the control group (3.1 +/- .5, 3.4 +/- .72, 3.1 +/- .10 ng/ml in groups II, III and IV at 60 h post-hCG vs .9 +/- .08 ng/ml in group I; P less than .05). These studies demonstrate that injections of ovulatory doses of hCG (500 to 1,500 IU) had three distinct effects on events concomitant with occurrence of estrus in gilts: decreased secretion of E2 immediately after hCG administration, failure to observe a preovulatory LH surge in some treated animals and earlier production of P4 by newly developed corpora lutea.     

Flushing and altrenogest affect litter traits in gilts

Gilts (n = 267) were allotted to flushing (1.55 kg/d additional grain sorghum), altrenogest (15 mg.gilt-1.d-1) and control treatments in a 2 x 2 factorial arrangement. Altrenogest was fed for 14 d. Flushing began on d 9 of the altrenogest treatment and continued until first observed estrus; 209 gilts (78%) were detected in estrus. The interval from the last day of altrenogest feeding to estrus was shorter (P less than .05) with the altrenogest + flushing treatment (6.6 +/- .2 d) than with flushing alone (7.6 + .3 d). Ovulation rates (no. of corpora lutea) were higher (P less than .05) in all flushed gilts (14.5 +/- .4 vs 13.4 +/- .4), whether or not they received altrenogest. Flushing also increased the total number of pigs farrowed (.9 pigs/litter; P = .06) and total litter weight (1.43 kg/litter; P = .01), independent of altrenogest treatment. Number of pigs born alive and weight of live pigs were higher for gilts treated with altrenogest + flushing and inseminated at their pubertal estrus than for gilts in all other treatment combinations. In contrast, gilts receiving only altrenogest had greater live litter weight and more live pigs born when inseminated at a postpubertal estrus than when inseminated at pubertal estrus. We conclude that flushing increased litter size and litter weight, particularly for gilts that were inseminated at their pubertal estrus. Increased litter size resulted from increased ovulation rates, which, in nonflushed gilts, limited litter size at first farrowing.     

Effect of intramuscularly administered beta-carotene on reproductive performance in sows

The present study investigated the effects of intramuscularly administered beta-carotene on reproductive parameters in female pigs. A total of 216 multiparous sows were observed from weaning of their litters until the next farrowing. On the day of weaning, the animals were allocated to two groups. Sows of the treatment group were injected with 70 mg beta-carotene both at the day of weaning and after the last insemination, sows of the control group were left untreated. For all sows, intramuscular injection of beta-carotene resulted in a significant increase of the total number of piglets born per litter by 1.2 (p < 0.05). When sows were divided by parity, beta-carotene treatment in second parity sows increased the total number of piglets per litter (beta-carotene 13.7 +/- 1.2, control 11.2 +/- 3.7, p < 0.01) and the number of piglets born alive (beta-carotene 12.0 +/- 2.7, control 10.0 +/- 3.4, p < 0.05). No such effect was seen in sows of third or higher parity. No other reproductive parameters were affected by beta-carotene supplementation. Tolerability and safety of the administered preparation were good. No side effects related to the medication were observed. The effect of beta-carotene on reproduction is thus affected by parity of the sows. This effect seems to be exerted mainly during early pregnancy and is most likely beta-carotene-specific and independent from its role as a vitamin A precursor.     

The effects of recombinant porcine somatotropin on reproductive function in gilts treated during the finishing phase.

The objective of this study was to determine the effects of recombinant porcine somatotropin (rpST) treatment during the finishing phase on subsequent reproductive function in crossbred gilts. Forty gilts weighing 50 kg and housed in a swine finishing facility were randomly assigned to control or rpST treatment. Four control and four rpST-treated gilts were allotted per pen. Twenty rpST-treated gilts received 6 mg of rpST.gilt-1.d-1 in 1 ml of buffered carrier and 20 control gilts received 1 ml of buffered carrier.gilt-1.d-1. Injections were administered daily at 1400 in the extensor muscle of the neck. All gilts received an 18% CP diet containing 1.2% lysine. Treatment was terminated when the average weight in each pen reached 110 kg. Gilts treated with rpST gained more weight (P less than .05) than control gilts (59.8 +/- 1.0 vs 53.5 +/- 1.0 kg). Age at puberty was not different (rpST, 182.2 +/- 3.3; control 181.4 +/- 3.1 d). Prior treatment with rpST did not significantly affect length of estrus (rpST, 1.9 +/- .1; control, 1.8 +/- .1 d) or estrous cycle length (rpST, 20.6 +/- .4; control, 20.4 +/- .4 d). Ovulation rates at second estrus were similar for rpST gilts (15.1 +/- .5) and control gilts (14.4 +/- .5). More embryos (P = .10) were recovered on d 9 to 12 of gestation from rpST-treated gilts than from control gilts (13.1 +/- .9 vs 10.7 +/- .9).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of inorganic or organic selenium on immunoglobulins in swine

A study was conducted to determine if Se source fed during gestation and lactation affects passive transfer of immunoglobulins. Sixty days prior to breeding （d -60）, gilts were randomly assigned to one of three treatments prior to breeding and throughout gestation： control （Control, no supplemental Se; n = 8）, inorganic Se （Inorganic Se, 0.3 ppm; n = 4） and organic Se （Organic Se, 0.3 ppm; n = 4）. Blood was collected on d -60, 57 and 113 of gestation and on d 21 of lactation and milk was collected at d 0, 1, 7, 14, and 21 of lactation. Blood was collected from piglets at d 0, 1, 7, 14, and 21 of age. Gilts fed organic Se had greater （P 〈 0.05） circulating concentrations of Se than Inorganic and Control gilts. Regardless of treatment, circulating concentrations of Se were greatest （P 〈 0.05） at d -60 compared to all other days. Serum concentrations of IgG were greatest （P 〈 0.05） in gilts at d 57 of gestation compared to d 113. Serum concentrations of IgA were greatest （P 〈 0.05） on d 113 of gestation and d 21 of lactation compared to d -60 and 57. Serum concentrations of IgM were greater （P 〈 0.05） at d 57 compared to d -60. Inorganic gilts had greater （P 〈 0.05） colostral and milk concentrations of IgG and IgM than Organic or Control gilts. Circulating concentrations of Se in piglets were greatest （P 〈 0.05） at d 14 and 21 of age compared to all other days. Piglets from gilts supplemented with organic Se had greater （P 〈 0.05） circulating concentrations of Se on d 1 versus piglets from gilts supplemented with no additional Se. The immunoglobulin concentrations of IgG, IgA, and IgM were lowest （P 〈 0.05） on d 0 and then different sources of Se did not affect the immunoglobulin ncreased when compared to d 1. The addition of concentrations in the gilt or piglet.     

Justification of unilateral hysterectomy-ovariectomy as a model to evaluate uterine capacity in swine

Experimental objectives were to measure the effect of ovulation rate on litter size at 86 d of gestation and at farrowing in 110 unilaterally hysterectomized-ovariectomized (UHO) gilts and in 142 intact, control gilts and to evaluate postnatal survival and development of progeny. Surgery (UHO) was performed on gilts 8 to 12 d following first estrus. Control and UHO gilts were mated and then randomly assigned to be slaughtered at d 86 of gestation or allowed to farrow. Gilts scheduled to farrow were observed by laparoscopy on d 40 of gestation to count corpora lutea (CL). Ovulation rate (number of CL) was similar for control (12.1 CL) and UHO (11.9 CL) gilts, thus indicating that compensatory ovarian hypertrophy had occurred in UHO gilts and resulted in a near doubling of ova per uterine horn relative to control gilts. Average litter size at 86 d of gestation and farrowing was greater (P less than .01) for control than UHO gilts. At farrowing, litter size for control and UHO gilts was 9.0 +/- .3 and 5.7 +/- .3 pigs, respectively. Fetal losses were greater and pig weights at birth were less in litters by UHO gilts. Postnatal pig survival, growth rate to 14 d of age and 14-d individual pig weight did not differ for progeny of control and UHO gilts, and performance of UHO pogeny did not appear to compromise the usefulness of this animal model. Regression of litter size on ovulation rate was .41 +/- .15 pigs/CL for UHO and .60 +/- .12 pigs/CL for control gilts at d 86 of gestation. Regression was .07 +/- .17 pigs/CL for UHO and .42 +/- .14 pigs/CL for control gilts at farrowing.(ABSTRACT TRUNCATED AT 250 WORDS)     

The performance of gilts in a new group housing system: endocrinological and immunological functions.

The effect of a new group housing system on performance (132 gilts and litters) and endocrinological (35 gilts) and immunological functions (28 gilts) was studied. Animals were randomly assigned to a conventional system (control), involving greater than 2 mo in individual stalls, or to the Hurnik-Morris (H-M) housing system, involving continuous housing in small groups, for breeding-gestating swine. The gilts were reared throughout gestation in their respective housing systems and moved 3 to 5 d prefarrowing to a common farrowing facility. Various production data were collected, including sow weight and backfat measurements, number of pigs born, number born alive, number weaned, litter birth weight, and litter weaning weight. An adrenal function test using dexamethasone pretreatment and ACTH1-24 challenge was imposed on gilts 5 d prebreeding and once between d 81 to 87 of gestation. Plasma progesterone was measured at the same time. Immune function was measured by serum antibody response to hen egg white lysozyme (HEWL) and delayed-type hypersensitivity (DTH) to tuberculin. Gilts reared in the H-M housing system exhibited a number of pigs weaned per litter and litter weaning weights comparable to the number and weights in the control system (7.3 +/- .33 vs 6.9 +/- .38, P = .421 and 56.9 +/- 2.42 kg vs 51.3 +/- 2.76 kg, P = .132, respectively). Prefarrowing and weaning backfat measurements were significantly reduced in group-housed gilts (15.8 +/- .45 mm vs 17.8 +/- .55 mm, P = .005 and 14.6 +/- .4 mm vs 16.2 +/- .42 mm, P = .008, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Induction of fertile estrus in prepuberal gilts by treatment with a combination of pregnant mare's serum gonadotropin and human chorionic gonadotropin

Ten trials involving 678 presumed prepuberal gilts (5.5 to 7.5 mo old) were conducted in North Carolina, Illinois and Missouri to evaluate the reproductive performance of gilts given a combination of 400 IU of pregnant mare's serum gonadotropin and 200 IU of human chorionic gonadotropin (P. G. 600). Gilts that were presumed to be prepuberal received P. G. 600 or no treatment (control) on the day of movement from finishing facilities to pens for breeding. Detection of estrus, with the aid of mature boars, was conducted daily for 28 d; gilts in estrus were mated naturally. Treatment with P. G. 600 increased the percentage in estrus within 7 (57.5 vs 40.9%) or 28 d (72.9 vs 59.5%); average interval to estrus was reduced (P less than .05) from 10.4 to 7.5 d. Farrowing rate (78.5 +/- 3.1%), number of pigs born alive (8.6 +/- .2) or dead (.26 +/- .06) and number of pigs weaned (8.0 +/- .2) were unaffected by treatment. Gilts that were heavier than the median for each farm were in heat sooner and more were detected in heat, but no other reproductive traits differed between heavy and light gilts. Overall, the results reveal that P. G. 600 was useful for induction of fertile estrus in prepuberal gilts.     

Influence of prenatal and postnatal fraternity size on reproduction in swine

Hypotheses of a negative association between fraternity size (size of litter in which an individual develops prior to birth or is reared following birth) and ovulation rate or litter size were tested by examining reproduction of females born or reared in varying prenatal and postnatal fraternities. Gifts were randomly assigned to develop prenatally and be reared postnatal in small or large fraternities. Dams of experimental animals were randomly assigned to one of two prenatal fraternity size treatments, either unilateral oviductal ligation (to bear a small prenatal litter) or no ligation (to bear a normal prenatal litter). Whereas this did result in differences (P less than .01) in litter size at birth (small = 6.2 +/- .4 vs large = 9.6 +/- .9), there was considerable overlap in observed litter sizes between ligated and nonligated dams. Consequently, effects of prenatal fraternity size were examined by regression. Distinct differences in postnatal fraternity size were created by randomly assigning piglets to small (5 piglets) or large (10 piglets) postnatal fraternities within 24 h of birth. Differences in postnatal fraternity size were maintained through weaning at 3 wk (small = 4.9 +/- .1 vs large = 9.4 +/- .2). Weights at birth (regression of birth weight on prenatal fraternity size = -.07 +/- .02, P less than .01) and weaning (small = 6.09 +/- .15 vs large = 5.46 +/- .17 kg, P less than .01) were heavier for gilts from small prenatal and postnatal fraternities, respectively, compared with gilts from large fraternities. Effects of prenatal and postnatal size on BW did not persist following weaning (P greater than .20).     

Use of chlortetracycline for treatment of new feedlot cattle

Two 56-d shipping fever trials of similar design were conducted the same season (fall) at Kansas State University (KSU) and at Purdue University (PU) to compare various levels of chlortetracycline (0 or 350 mg X head-1 X d-1 continuously or 1, 2 or 4 g X head-1 X d-1 for the first 14 d). Weanling crossbred steer calves were utilized (210 head of Angus X Simmental, averaging 197 kg, at KSU; 268 head of Angus X Hereford, averaging 192 kg, at PU). For the first 28 d in the KSU trial (October 13 to December 8), cattle that received 4 g X head-1 X d-1 the first 14 d gained more rapidly (P less than .05) than cattle fed 350 mg X head-1 X d-1 continuously or than the controls that received no chlortetracycline (CTC; 1.05 vs .92 or .93 kg/d, respectively). Cattle that received 4 g CTC X head-1 X d-1 for the first 14 d required less (P less than .05) dry matter per kg gain than steers that received 350 mg X head-1 X d-1 continuously over the 56-d period. In the PU trial (October 6 through December 1), all CTC treatments resulted in increased feed efficiency (P less than .05) over the controls through 28 d, and the 4 g X head-1 d-1 for 14 d and 350 mg X head-1 X d-1 continuously, improved feed efficiency over the other groups for the 56-d period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of suckling intensity on milk yield and piglet growth from lactation-enhanced gilts

The effects of suckling intensity on milk yield and piglet growth were determined when lactation capacity of the sow was enhanced through overexpression of a mammary-specific transgene, bovine alpha-lactalbumin. Lactational response to increased suckling stimulation was determined by fostering litters of the same age (d 1) or 7 d older (d 7) than the day of lactation to sows nontransgenic (control) or transgenic (TG) for bovine alpha-lactalbumin. Twenty first-parity gilts were allocated to 4 treatments dependent on gilt genotype and age of litter fostered (control d 1, control d 7, TG d 1, and TG d 7). Litters were standardized to 10 piglets within 24 h postpartum, and nonbirth piglets were fostered to gilts with an equal litter BW within age groups at 36 h postpartum. Milk yield was determined by the weigh-suckle-weigh method on d 6, 9, 12, 15, and 18 of lactation. Mean daily milk yield was greater (P = 0.031) for TG gilts compared with control gilts and tended to be greater (P = 0.056) for all gilts with d-7 piglets compared with those with d-1 piglets. Daily milk yield of TG d 7 gilts increased rapidly to peak at d 9 and was greater than milk yield of all control gilts at d 9 (P < 0.01), 12 (P < 0.02), and 15 (P < 0.02). Mean daily milk yield of TG d 7 gilts was 2.1 kg greater (P = 0.002) than for control d 7 gilts and 2.0 kg greater (P = 0.004) than for TG d 1 gilts. Daily milk yield of control d 1 gilts was not different from that of TG d 1 gilts (P = 0.49) or control d 7 gilts (P = 0.63). Piglet BW gain between d 3 and 6 was greater (P < 0.01) in the TG d 7 group than for all other groups and was greater (P < 0.05) than the control groups between d 6 and 9. No difference was found when comparing accumulated BW gain of the piglets between the day of age at foster (d 1 vs. 7; P = 0.606) or between the control d 1 and control d 7 groups (P = 0.759). Accumulated BW gain of piglets suckling TG d 7 gilts from d 3 through 9 was greater (P < 0.02) than that of the other groups and continued to be greater (P < 0.05) than that of either of the control groups through d 15. However, by d 15, accumulated BW gain of piglets suckling TG d 1 gilts was no longer different (P = 0.40) from that of the TG d 7 group and was greater (P < 0.05) than that of the control d 1 group. The enhanced lactation potential of these TG gilts synergized with suckling intensity to stimulate increased milk production during early lactation, resulting in increased piglet growth.     

Influence of vitamin A injection before mating on oocyte development, follicular hormones, and ovulation in gilts fed high-energy diets

Previous research revealed that treatment with vitamin A approximately 5 d before ovulation may increase litter size in weaned sows and improve embryonal survival in gilts fed high-energy diets that reduced embryonal survival. For the current study, the hypothesis was that administration of vitamin A before ovulation would alter development of follicles and oocytes in a way favorable to enhanced embryonal survival. (Landrace x Large White) x (Duroc x Hampshire) gilts (n = 44) were fed 11.0 Mcal ME x gilt(-1) x d(-1) beginning 7 d after second estrus and given (i.m.) corn oil or 1 x 10(6) IU of vitamin A (retinyl palmitate) on d 15 after second estrus. Gilts were checked for estrus every 4 h, mated naturally at third estrus, and assigned randomly to undergo midventral laparotomy beginning at 24 to 28, 28 to 32, 32 to 36, or 36 to 40 h after onset of third estrus. At laparotomy, ovulated oocytes and early-stage embryos were recovered from oviducts, and ovaries were removed for aspiration of oocytes and granulosa cells from unovulated follicles. Oocytes and embryos were stained for assessment of stage of development. Granulosa cells were cultured to assess their ability to secrete progesterone. Follicular fluid was assayed for progesterone, estradiol-17beta, IGF-I, and PGF2alpha. Treatment with vitamin A altered development of oocytes and embryos by decreasing the percentage at the germinal vesicle stage and increasing the percentage at advanced stages. Mean stage of development was increased by vitamin A, but variation in stage was decreased. Among follicles matched by meiotic stage of oocyte, follicular fluid concentrations of progesterone, IGF-I, and PGF2alpha were greater in vitamin A-treated gilts than in controls, but treatment with vitamin A in vivo did not affect LH-stimulated or unstimulated secretion of progesterone by granulosa cells in vitro. These data provide evidence that vitamin A may influence embryonic development by advancing resumption of meiosis and altering follicular hormonal environment during follicle maturation.     

The effect of age at first mating on litter characteristics in the native nigerian pig

Thirty primiparous gilts of the local breed, which has a very small size, were used in an experiment to study the effect of breeding age (3, 5, 7, 9, 11 and 13 months) on weight at breeding, gestation length, litter size, birth weight, and weaning weight.Increase of breeding age involved increase in breeding weight. Gilts in the three-month age group showed heat but none of them became pregnant at mating. Gilts in age groups from 5 up to 13 months became pregnant after breeding. The mean gestation length ranged between 113 and 114 days and seemed not to depend on the age at breeding.There was no significant difference among the various age groups in litter size (4 or 5 piglets). However, birth weight (between 0.6 and 1.1 kg) and weaning weight tended to increase with increase in age at mating.     

Reduction in age of puberty in gilts consuming melatonin during decreasing or increasing daylength

Two experiments were conducted to determine whether oral administration of melatonin alters the onset of puberty in gilts during naturally increasing or decreasing daylength. In Exp. 1, 20 crossbred prepubertal gilts weighing 77.5 +/- .5 kg at 171.8 +/- 1.0 d of age were assigned randomly to receive either a daily oral dose of 3 mg of melatonin (MEL) or ethanol vehicle (ETH) at 1530 from August 31 to December 1, 1987 (decreasing daylength). Gilts were exposed to mature boars for 20 min thrice weekly and blood samples were collected twice weekly. Serum concentrations of progesterone were used to establish age at puberty and length of estrous cycle. In Exp. 2, 20 crossbred prepubertal gilts weighing 67.7 +/- .7 kg at 143.8 +/- 1.1 d of age received either MEL or ETH treatment from February 1 to May 15, 1988 (increasing daylength). Age of puberty was less in gilts that received MEL than in gilts that received ETH in both Exp. 1 (198 +/- 3 vs 228 +/- 7 d; P less than .01) and Exp. 2 (183.8 +/- 2.7 d vs 194.3 +/- 3.3 d; P less than .05). Gilts that received MEL reached puberty at a lighter weight than gilts that received ETH in Exp. 1 (95.6 +/- 2.1 vs 112.4 +/- 3.9 kg; P less than .01) and Exp. 2 (88.1 +/- 1.5 vs 96.0 +/- 1.8 kg; P less than .01). Serum concentrations of LH and FSH, length of estrous cycles, and percentage of muscle of carcasses were similar between MEL and ETH gilts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Study on the oestrous synchronization in gilts by using progestin altrenogest and hCG: its effect on the follicular development, ovulation time and subsequent reproductive performance.

The aim of this study was to further investigate the effect of using progestin altrenogest and hCG to synchronize the oestrous cycle and its effect on follicular development, ovulation time and subsequent reproductive performance. Thirty crossbred gilts were divided into three groups. Group A (control) received a 5 ml of normal saline for 18 consecutive days by individually top-dressing. Groups B and C gilts received 20 mg (5 ml) of progestin altrenogest for 18 consecutive days by individually top-dressing. On day 3 (72 h) after withdrawal of progestin altrenogest, Group C gilts received hCG (500 IU, im). The follicular development and ovulation time were examined by transabdominal ultrasonography. Subsequent reproductive performances, i.e. number of total born per litter (NTB), number of live born per litter (NBA), number of stillbirth per litter (NSB), average piglet birth weight (ABW), lactation length (LL) and weaning to oestrous interval (WOI), were recorded. None of the gilts in Group A showed oestrus within 10 days after withdrawal of normal saline. Groups B (eight of 10) and C gilts (four of 10) came into oestrus at 5.6 +/- 0.5 and 6.5 +/- 0.6 days after withdrawal of progestin altrenogest, respectively. The ovulation time of Groups B and C gilts took placed at 25.0 +/- 4.7 and 25.0 +/- 5.0 h after standing oestrus, respectively. The pre-ovulatory follicular size (diameter) of Groups B and C gilts was 8.0 +/- 2.0 and 11.0 +/- 3.0 mm, respectively. A tendency of larger litter size (NTB) in Group B gilts was found when compared with Group A gilts. To conclude, using progestin altrenogest alone can be used to synchronize the oestrous cycle in gilts without unenthusiastic effect on the follicular development, ovulation time and subsequent reproductive performances. However, treatment of gilts with hCG at day 3 (72 h) after withdrawal of altrenogest had unenthusiastic effect on oestrus synchronization.     

Influence of norgestomet in combination with gonadotropins on induction of estrus and ovulation in prepubertal gilts.

Our objective was to determine whether priming with the progestogen norgestomet for 9 d would enhance estrual and ovulatory responses of prepubertal gilts to PG600 (400 IU eCG + 200 IU hCG). Gilts (140 to 190 d old) were assigned by litter, age, and weight to one of three treatments: 1) 9 d of norgestomet implant with an injection of PG600 after implant removal on d 9 (N+PG; n = 43); 2) no implant and an injection of PG600 on d 9 (PG; n = 36); or 3) neither implant nor PG600 (control; n = 29). Beginning on d 0, gilts were exposed once daily to a boar and checked until estrus was observed or until d 45 after the start of the experiment. Ovaries were examined for number of corpora lutea (CL) after estrus or at 45 d. Greater proportions of N+PG (63%, P < .05) and PG (69%, P < .01) gilts expressed estrus than did controls (34%), but proportions did not differ between N+PG and PG (P > .10). Among gilts in estrus following treatment with N+PG or PG, 100% showed estrus within 6 d after PG600 injection. For gilts that expressed estrus within 45 d, the average age at estrus was reduced (P < .05) by PG to 172 +/- 2 d compared with 182 +/- 4 d for controls. Average age at estrus did not differ (P > . 10) between PG and N+PG (177 +/- 2 d). Greater proportions of N+PG (82%; P < .001) and PG (65%; P < .001) gilts ovulated than controls (13%), but proportions did not differ between N+PG and PG (P > .10). The number of CL (20 +/- 2) was not affected by treatment and ranged from 2 to 71. There was no increase in ovarian cysts in response to treatment. Results indicated that norgestomet before PG600 did not enhance estrus expression or ovulation compared with PG600 alone, but use of PG600 increased the proportions of gilts that expressed estrus and ovulated compared with controls.     

Dose-response shift in the ability of gilts to remain pregnant following exogenous estradiol-17 beta exposure

Sixty mated gilts were assigned to a 2 X 6 factorial arrangement (n = 5) of day of injection (d 9 and 10 vs 12 and 13; d 0 = first day of estrus) and dose of estradiol-17 beta (0, .125, .5, 2, 8 and 32 mg X gilt-1 X d-1). Gilts were subsequently slaughtered on d 30; pregnancy was verified and percent embryonic survival calculated. A 64-fold shift in the dose-response curve for percent embryonic survival illustrated that the adverse effects of exogenous estradiol-17 beta were less when administered on d 12 and 13 as compared with d 9 and 10 (day X dose, P less than .01). This experiment demonstrated that the uterine-embryonic environment of d 12 and 13 pregnant gilts was more tolerant of exogenous estrogen alterations than that of d 9 and 10 pregnant gilts.     

Effect of treatment with and subsequent withdrawal of exogenous porcine somatotropin on growth and reproductive characteristics of gilts

Two experiments were conducted to examine responses of gilts to treatment with and withdrawal of exogenous porcine somatotropin (PST). In Exp. 1, 36 prepubertal gilts (79.7 +/- .9 kg; 159.1 +/- .7 d) were allotted randomly to receive daily either 0 micrograms PST (C) or 70 micrograms PST/kg initial BW for either 21 (PST-3) or 42 d (PST-6). Gilts were examined for estrus daily by a mature boar starting on d 22 and continuing for up to 50 d. Gilts that expressed estrus were mated and removed from treatment. PST-treated gilts had higher ADG (P less than .01) and lower feed/gain (P less than .02) than C gilts. Following initiation of boar exposure, C gilts (mean interval to estrus = 2.0 d) exhibited estrus earlier than PST-3 (24.8 d) and PST-6 (24.0 d) gilts (P less than .07); however, only two C gilts were observed in estrus compared with six PST-3 and six PST-6 gilts. In Exp. 2, 40 prepubertal gilts (72.6 +/- 1.0 kg; 141.1 +/- .7 d) were allotted randomly to receive daily either 0 mg PST (C) or 5 mg PST for 30 d. On d 31, half the gilts were comingled with unfamiliar penmates and examined for estrus daily by a mature boar for up to 45 d. Estrual gilts were removed from treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

The vitamin A activity of beta-carotene in growing pigs. 1. Effect of a supplementation of a grain soya bean meal diet with vitamin A or beta-carotene on the liver vitamin A storage

In 3 experiments with a total of 113 growing pigs, supplements of 1,000 to 9,000 IU vitamin A or 2 to 100 mg beta-carotene to vitamin A and beta-carotene free grains soyabean-meal-diets were tested. The liver samples were taken by biopsy or after slaughtering. The error of biopsy sampling was defined in preliminary experiments. The initial liver vitamin A depots were checked by slaughtering of 5 piglets of each group. The vitamin A content was analyzed by the anhydromethod or fluorometrically. In all 3 experiments, the different vitamin or provitamin intake did not influence feed intake and growth at any time. Highly significant linear relations were found between the intake of vitamin A or beta-carotene and the storage in the liver. Due to the higher relative liver weight, younger animals had a lower vitamin A concentration in this organ. Related to the tested beta-carotene dose of 2, 4, 8, 50 and 100 mg/kg feed, a vitamin A activity of 360, 320, 290, 130 and 80 micrograms retinol equivalents per mg beta-carotene was found. The conversion of beta-carotene into vitamin A decreases inversely to the beta-carotene intake. The vitamin A activity of synthetic beta-carotene which is higher than the beta-carotene analyzed in feedstuffs is discussed.