The effects of feed intake and body fatness on progesterone metabolism in ovariectomized gilts

Evidence-based practice in canine artificial insemination

A number of methods are currently used to predict the optimal date of insemination of the breeding bitch, particularly with the use of frozen-thawed canine semen which has a far shorter lifespan than fresh semen. Aside from confirming cytological oestrus, vaginal cytology is of no assistance in predicting the most fertile day(s) in a bitch; however, a neglected avenue of research suggests that vaginal cytology may be of great importance in confirming the days of optimal fertility retrospectively. Similarly, vaginoscopy provides clues as to the stage of a bitch's cycle but is inadequate as a sole determinant of her most fertile days. Nevertheless, vaginoscopy is useful to identify very late oestrus and the onset of dioestrus, as well as Stage I of labour (cervical dilatation). Due to variations in the rate at which circulating progesterone concentrations rise in individual bitches, the reliability of circulating progesterone concentrations for determining the optimal day(s) of insemination with frozen-thawed semen decreases as values rise. Moreover, progesterone assay results can vary widely due to extrinsic factors such as the time of blood sampling, sample storage conditions and the assay employed. Finally, this review investigates evidence surrounding various insemination routes and suggests that well-performed vaginal insemination, even with frozen-thawed semen, may be an acceptable approach for cases where transcervical insemination is impractical.

Design and evaluation of a recyclable intravaginal device made of ethylene vinyl acetate copolymer for bovine estrus synchronization

In bovine estrus synchronization, intravaginal devices made of silicone are used to administer exogenous progesterone with the aim of maintain plasmatic levels above 2 ng ml^-1 during the treatment. After their use, devices must be discarded. There is an important concern on the environmental impact of the disposal of these used products due mainly to the non-degradability of the silicone and to the residual content of the hormone. Different alternatives are being studied, and the use of ecological materials appears as the more important. The objective of the present contribution was to design and evaluate a recyclable intravaginal prototype using ethylene vinyl acetate copolymer (EVA). Devices were fabricated by an injection-molding technique and characterized in terms of dimensions, loading efficiency, release rate, and wing tension. An analysis was first conducted to compare three different matrices and two supports. Secondly, the best candidate prototype was assayed in both beef and dairy cattle. Finally, used matrices were recycled measuring the progesterone content in the resulting devices and testing them in vitro. According to release tests, no differences were observed between the three matrices both in vitro and in vivo. On the contrary, a better performance was achieved when a support with a more flexible Y shape was used in comparison with a rigid T geometry. Successful results were observed in non-lactating cows, with plasma concentrations above the threshold value defined for the synchronization therapy. However, lower progesterone levels resulted when devices were tested in animals with large milk production. By last, recycled matrices presented a similar initial content and in vitro release rate than original matrices. These findings could open the possibility to use recyclable EVA devices as an alternative to the non-degradable silicone intravaginal inserts. Future research must be carried out to optimize the performance of the recycled matrices in dairy cattle. Modifications of the release surface and/or the initial loading can give a solution to the lower values observed in these animals. Graphical abstract.

Caudal vena cava progesterone and LH release patterns on Day 14 of gestation in primiparous sows

The aim of the present study was to explore the relationship between systemic and local progesterone secretion and LH pulsatility during implantation in the pig. Differences in progesterone concentrations measured locally in the caudal vena cava and systemically in the jugular vein were studied in eight primiparous sows on Day 14 of pregnancy. LH pulsatility was analysed for its effects on the local progesterone-releasing pattern. Mean (±s.d.) progesterone concentrations in the vena cava (65.5±19.8ngmL^-1) were approximately double basal concentrations (33.6±13.1ngmL^-1). Basal concentrations of progesterone and LH were calculated as the average of the lowest six values. Basal caudal vena cava and mean jugular (27.6±1.5ngmL^-1) progesterone concentrations did not differ significantly. Pre- and postprandial jugular progesterone concentrations were significantly different in the morning and afternoon (P=0.025 and 0.023). Mean LH ranged from 0.24 to 0.43ngmL^-1 and was approximately double as high as basal LH in individual sows. In 60.8% of cases, LH pulses were followed by a progesterone pulse within 1h. In conclusion, the present study showed that corpus luteum function appears to respond to LH pulsatility on Day 14 of pregnancy. However, the response varies at the level of individual sows. In addition, systemic postprandial decreases in progesterone were confirmed on Day 14 of pregnancy.

Effect of nutrition on plasma lipid profile and mRNA levels of ovarian genes involved in steroid hormone synthesis in Hu sheep during luteal phase

Ovarian steroid hormones regulate follicular growth and atresia. This study aims to determine whether key ovarian sterol-regulatory genes are differentially expressed in Hu sheep under different short-term nutritional regimens. Estrus was synchronized using intravaginal progestagen sponges. The ewes were assigned randomly to 3 groups. On d 6 to 12 of their estrous cycle, the control (CON) group received a maintenance diet (1.0×M), the supplemented (SUP) group received 1.5×M, and the restricted (R) group received 0.5×M. On d 7 to 12, blood samples were taken. The sheep were slaughtered at the end of the treatment, and their organs and ovaries were collected. The plasma concentrations of urea (P<0.01), total cholesterol (P<0.01), low-density lipoprotein cholesterol (P<0.01), NEFA (P<0.01), FSH (P<0.05), and estradiol (P<0.05) increased with decreasing dietary intake, whereas plasma triglyceride (P<0.01) and triiodothyronine (T3) concentrations decreased (P<0.05). The ewes in the R group had higher spleen weight and percentage of spleen to BW and lower liver and small intestine weights and percentage of liver/stomach to BW than the SUP group ewes (P<0.05). Nutritional restriction decreased the cytochrome p450 (CYP17A1) and estrogen receptor 1 (ESR1) mRNA expression (P<0.05) and increased the cytochrome p450 aromatase (CYP19A1) mRNA expression (P<0.05) in follicles>2.5 mm. Follicle size affected the mRNA expression of very low density lipoprotein receptor (VLDLR), estrogen receptor 2 (ESR2), FSH receptor (FSHR), CYP17A1, and CYP19A1 (P<0.05). In conclusion, we suggest that a potential mechanism by which short-term negative energy balance inhibits follicular growth may involve responses to disrupted reproductive hormone concentrations and influenced the intrafollicular expression of CYP17A1, CYP19A1, and ESR1. This result may be due to increased plasma urea and lipid concentrations.

Timing of lactational oestrus in intermittent suckling regimes: consequences for sow fertility

Three intermittent suckling (IS) regimes were evaluated for their effects on lactational oestrus and subsequent fertility. Control sows were weaned (CW; n = 38) at d 26 ± 2 of lactation. In IS19-7D (n=40) and IS19-14D (n=42) sows, IS started at d 19 ± 1 of lactation and sows were weaned 7 or 14 d later. In IS26-7D (n=41), IS started at d 26 ± 1 of lactation and sows were weaned 7d later. During IS, sows were separated from their piglets for 10h/day. Oestrus detection was performed twice daily without a boar and ovulation was confirmed by ultrasound once a week. In IS19-7D, IS19-14D and IS26-7D, respectively, 50%, 64% and 61% of the sows showed oestrus and ovulation during IS (P>0.05), and, of the remaining sows, 100%, 93%, and 69% showed oestrus in the first week after weaning. In CW sows, 95% showed oestrus in the first week after weaning. Parity 1 sows were considerably less likely than older parities (23% vs. 68%) to show oestrus in lactation. Pregnancy rate of the first post partum oestrus (during lactation or after weaning) was 89% (CW), 92% (IS19-7D), 80% (IS19-14D) and 77% (IS26-7D) (P>0.05) and subsequent litter size was 14.5 ± 0.5, 14.5 ± 0.6, 15.3 ± 0.5 and 15.2 ± 0.8, respectively (P>0.05). Sows mated during lactation had similar pregnancy rate and litter size to those mated after weaning. Hence, ongoing lactation for the first 2-9 d of pregnancy did not negatively affect fertility. A total of 50-64% of IS sows showed lactational oestrus, regardless of the stage of lactation. Pregnancy rates and litter size were similar to control sows, and were not affected by stage of lactation at mating.

Effect of feeding allowance level on embryonic survival, IGF-1, insulin, GH, leptin and progesterone secretion in early pregnancy gilts

The present experiment was conducted to evaluate the effects of feeding allowance level on embryonic survival, uterine development and reproductive hormone secretion in early gestation gilts. A total of 54 F1 crosses of Landrace x Large white gilts were randomly allocated to three treatment groups of high (H, 2 x maintenance), medium (M, 1.2 x maintenance) and low (L, 0.6 x maintenance) feeding level after mating. Blood samples and uterine flushings were collected on day 12, 25 and 35 of pregnancy, and embryonic survival rate was estimated. Concentrations of insulin-like growth factor I (IGF)-1, insulin, growth harmone (GH), leptin and progesterone in serum and uterine flushings were determined by enzyme-linked immunosorbent assay. Embryonic survival was affected by dietary treatment; total number of viable embryos and embryo survival of group M were higher than other groups in the early pregnancy (p < 0.05). Greater foetal weight in M gilts was achieved when gestation advanced to day 35 (p < 0.05), though there was no difference on day 25 of pregnancy among treatments. No appreciable differences were observed in the crown-rump length on day 25 and 35 of pregnancy among groups. Greater weight of uterus and products of conception were identified in M gilts compared with group H and L (p = 0.024 and p = 0.005, respectively) on day 25 of pregnancy. The hormone level was greatly affected by feeding allowance level. In serum, concentrations of IGF-1, leptin and insulin tended to be greater in H than in M and L during the early gestation, while concentrations of GH were greater in M and progesterone were the lowest in H. At the same time, feed allowance level affected the concentration of IGF-1, insulin, GH, leptin and progesterone in uterine flushings. These data demonstrated that feed allowance level after mating has important consequence on embryo survival, embryo development and uterine development, possibly mediated by nutrition level inducing changes in concentrations of reproductive hormones and/or intermediary metabolites in early pregnancy.

Effects of dietary vitamin supplementation and semen collection frequency on hormonal profile during ejaculation in the boar

To evaluate the effect of dietary and management factors on boar hormonal status during ejaculation, 39 boars were canulated to determine the profiles of luteinizing hormone (LH), follicle-stimulating hormone (FSH), 17beta-estradiol (E2), and testosterone (T) in blood plasma and seminal fluid. Prior to canulation, 18 boars were fed a basal diet (control), whereas the remainder (n=21) were fed a basal diet supplemented with extra vitamins (supplemented). Within each dietary treatment, two regimens of semen collection were used over the 3mo preceding the hormonal evaluation: three times per 2wk (3/2) or three times per wk (3/1). Plasma E2 was lower (P<0.01) before ejaculation (232.5+/-22.6pg/mL) than at the onset of ejaculation (255.2+/-27.1ng/mL). Plasma T increased from 5.14+/-0.72, before ejaculation to 5.87+/-0.86ng/mL at the onset of ejaculation in supplemented boars, whereas it decreased from 5.15+/-0.65 to 4.87+/-0.70ng/mL in controls (diet by time, P<0.05). At the onset of ejaculation, plasma FSH was higher in 3/2 boars (0.436+/-0.06ng/mL) than in 3/1 boars (0.266+/-0.04ng/mL; P<0.05). During ejaculation, plasma LH increased linearly (P<0.01) from 0.59+/-0.07 to 0.97+/-0.10ng/mL, and plasma E2 and T concentrations were correlated (r=0.62, P<0.01). Plasma FSH before and during ejaculation was negatively correlated with sperm production (r=-0.60, P<0.01) and testicular weight (r=-0.50, P<0.01). In conclusion, dietary and management factors had few impacts on hormonal profiles during ejaculation, but homeostasis of some hormones was related to some criteria of reproductive performance in boars.

Effect of feeding flax or linseed meal on progesterone clearance rate in ovariectomized ewes

Ovariectomized ewes (n=22; 68.76+/-2.34 kg initial body weight; 2.9+/-0.1 initial body condition score) were individually fed one of three diets: (1) control (phytoestrogen-free; n=7), (2) flax containing diet (n=8), or (3) linseed meal (LSM) containing diet (n=7) to investigate the rate of progesterone (P4) clearance. On day 20 of feeding (day 0=initiation of treatment), a P4 releasing device (CIDR) was placed in the vagina and jugular blood samples were obtained prior to CIDR insertion and 15, 30, 60, and 120 min following CIDR insertion. Further, blood samples were obtained daily between days 21 and 24. On day 25, blood samples were retrieved prior to CIDR removal and 2, 5, 10, 15, 30, 60, 120, and 360 min following CIDR removal. There was no difference in initial or final body weight or body condition score and there were no time by diet interactions on P4 clearance. The fractional rate of P4 uptake measured prior to CIDR insertion through day 4 following insertion tended to be greater (P=0.07) in LSM fed ewes (508.75+/-71.37%/min) compared to flax (295.39+/-66.76%/min) and control fed (287.54+/-71.37%/min) ewes. Diet tended (P=0.10) to influence P4 clearance rate when measured from prior to CIDR removal through 120 min following CIDR removal with LSM fed ewes having a greater (1.26+/-0.2) fractional rate constant than flax (0.929+/-0.09) and control fed (0.922+/-0.09) ewes. Flax fed ewes also had more (P<0.01) omega-3 fatty acids and total fatty acids in plasma. Reports of increased pregnancy rates in dairy cows fed flax may relate to P4 metabolism.

Peri-oestrus hormone profiles and follicle growth in lactating sows with oestrus induced by intermittent suckling

This study describes follicle dynamics, endocrine profiles in multiparous sows with lactational oestrus compared with conventionally weaned sows (C). Lactational oestrus was induced by Intermittent Suckling (IS) with separation of sows and piglets for either 12 consecutive hours per day (IS12, n = 14) or twice per day for 6 h per occasion (IS6, n = 13) from day 14 of lactation onwards. Control sows (n = 23) were weaned at day 21 of lactation. Pre-ovulatory follicles (> or =6 mm) were observed in 100% of IS12, 92% of IS6 and 26% of C sows before day 21 of lactation and in the remaining 74% C sows within 7 days after weaning. All sows with pre-ovulatory follicles showed oestrus, but not all sows showed ovulation. Four IS6 sows and one IS12 sow developed cystic follicles of which two IS6 sows partially ovulated. Follicle growth, ovulation rate and time of ovulation were similar. E(2) levels tended to be higher in IS sows (p = 0.06), the pre-ovulatory LH surge tended to be lower in IS12 (5.1 +/- 1.7 ng/ml) than in C sows (8.4 +/- 5.0 ng/ml; p = 0.08) and P(4) levels were lower in IS12 and IS6 than in C sows (at 75 h after ovulation: 8.8 +/- 2.4 ng/ml vs 7.0 +/- 1.4 ng/ml vs 17.1 +/- 4.4 ng/ml; p < 0.01). In conclusion, sows with lactational oestrus induced by IS are similar to weaned sows in the timing of oestrus, early follicle development and ovulation rates, but the pre-ovulatory LH surge and post-ovulatory P(4) increase are lower.

Feeding level does not affect progesterone levels in intermittently suckled sows with lactational ovulation

The aim of this study was to examine whether the low post-ovulatory plasma P(4) levels found in intermittently suckled (IS) sows are related to the high feeding level during intermittent lactation. Multiparous sows (n=21) were separated from their piglets for 12h per day starting at day 14 of lactation until 6 days after ovulation. At day 28 of lactation, 9 sows had ovulated (spontaneous) and the remaining 12 sows were treated with PG600 (PG600-induced). At ovulation sows were allocated to either a high (H) feeding level (on average 6.5 kg) or a low (L) feeding level (high feeding level minus 2.5 kg) until 6 days after ovulation. Plasma P(4) levels were not affected by feeding level or type of ovulation (P>0.10), and neither were CL parameters, embryo survival rate and embryo development at day 30 of gestation. In conclusion, low levels of plasma P(4) were found in IS sows with lactational ovulation but these were not affected by feeding level during the first week after ovulation. Further studies are needed to investigate which factors cause the lower plasma P(4) levels in these sows.

Food deprivation stimulates the luteolytic capacity in the gilt

The aims of this study were to study the effects of fasting on progesterone (P4) production in the pig and to verify whether fasting influences luteal expression of PGF(2alpha) receptor (FPr) and prostaglandin secretion. Superovulated prepubertal gilts were used; half of them were fasted for 72h starting on day 2 (F2) or 9 (F9) of the induced estrous cycle, respectively, while two groups (C2 and C9) served as respective controls. Plasma P4 and PGFM concentrations were determined by RIA while FPr mRNA expression in CLs collected at the end of fasting period was measured by real-time PCR. In experiment 1, plasma P4 concentrations in fasted gilts were significantly (P<0.01) higher than in controls starting from day 3 (F2; n=6) and 10 (F9; n=6). FPr mRNA expression was similar in F2 and C2 (n=6) CLs while it was significantly (P<0.05) higher in F9 than in C9 (n=6) CLs. In experiment 2, cloprostenol administered on day 12 significantly (P<0.05) increased FPr mRNA expression in CLs from both F9 (n=6) and C9 (n=6) gilts. At the time of cloprostenol injection PGFM levels were significantly higher (P<0.05) in the fasted group and cloprostenol-induced luteolysis in fasted but not in normally fed gilts. Results from this study indicate that fasting in prepubertal gilts induced to ovulate stimulates luteal P4 and PGFM production as well as FPr mRNA expression, thus increasing luteolytic susceptibility.

Hormonal relationships during the periovulatory period among ewe breeds known to differ in fertility after cervical artificial insemination with frozen thawed semen

Our previous work indicates that ewe breed differences in fertility following cervical AI with frozen-thawed semen are due to failure of normal sperm transport and/or early embryo development. Here we examined differences in hormone concentrations about the time of ovulation among more (Finnish Landrace and Belclare) and less (Suffolk and Texel) fertile ewes after AI with frozen thawed semen. In Experiment 1, oestradiol concentrations were measured in samples collected frequently from 12h before to 18h after the LH surge and progesterone was measured in samples collected from 9 to 27h after the LH surge in Suffolk (n=24), Texel (n=20) and Finnish Landrace (n=27) ewes. In Experiment 2, oestradiol concentrations were measured in samples collected frequently from 24h before to 6h after the LH surge and progesterone was measured in samples collected from 6h to 6 days after the LH surge in Suffolk (n=35) and Belclare (n=30) ewes. In Experiment 1, there was an effect of breed, time and their interaction (P<0.001) on oestradiol concentrations between -12 and +6h but only breed differences at +12 and +18h (P<0.01). Progesterone concentrations increased over time (P<0.001) and the rate of increase was significantly greater in Finnish Landrace than in the other two breeds. In Experiment 2, oestradiol concentrations were unaffected by breed. There was an interaction between breed and time with the rate of increase of progesterone being greater in Belclare than Suffolk ewes (P<0.001). In conclusion, differences in hormone concentrations in the periovulatory period are not consistent with ewe breed differences in fertility; however, we have showed that progesterone concentrations rise earlier in the more prolific breeds and suggest that this may explain reported ewe breed differences in embryo development.

Ingestão de concentrado e concentração plasmática de progesterona em vacas da raça Holandesa

Vacas da raça Holandesa não-lactantes (n=7), que receberam 4kg/dia de concentrado durante 28 dias e pasto ad libitum, foram sincronizadas com protocolo Ovsynch. No dia 0 (segunda aplicação de GnRH), as vacas foram distribuídas em dois grupos: as do grupo 2kg receberam 2kg/dia, e as do grupo 8kg receberam 8kg/dia de concentrado, oferecido duas vezes/dia. Os animais foram sincronizados novamente na fase 2. Aqueles que receberam 2kg de concentrado na primeira fase passaram a receber 8kg na segunda fase e vice-versa. As estruturas ovarianas foram avaliadas diariamente por ultra-sonografia. Amostras de sangue para dosagem de progesterona (P4), por radioimunoensaio, foram colhidas diariamente, antes do fornecimento do concentrado e quatro horas depois, até o dia 16 do ciclo estral. Não houve diferença entre os grupos quanto ao diâmetro do folículo ovulatório no dia 0 e ao diâmetro do maior folículo no dia 16. O diâmetro do corpo lúteo foi maior (P<0,05) no dia 16 nos animais do grupo 8kg. Observou-se interação (P<0,05) da quantidade de concentrado fornecida versus dia da colheita das amostras quanto à concentração plasmática de P4. A concentração plasmática de P4, imediatamente antes do fornecimento do concentrado e quatro horas depois, foi menor no grupo 8kg, após o dia 9 do ciclo estral.

A new approach to enhance reproductive performance in sheep using royal jelly in comparison with equine chorionic gonadotropin

The objective was to compare the effects of royal jelly (RJ) and eCG treatments on reproductive performance of ewes synchronized using intravaginal progesterone-releasing devices. Forty-two cycling Awassi ewes were treated intramuscularly (i.m.) with 15 mg PGF2alpha. On the following day, all ewes were administered with CIDR-G for 12 days and were randomly allocated to three (RJ, eCG and control) groups of 14 ewes each. Ewes in the RJ-treated group received daily i.m. treatments of 400mg RJ during the period of CIDR-treatment. Each ewe in the eCG-treated group received an i.m. treatment of 500 IU eCG at the time of CIDR-G removal (day 0) and no further treatment was given to ewes in the control group. Ewes were exposed to four fertile rams for 72 h, from the time of CIDR-G removal, and checked for breeding marks at 6-h intervals. Blood samples were collected from day -13 until day 0 and thereafter until day 19 for progesterone analysis. Royal jelly treatment resulted in a greater rate of decline and lower (P<0.02) progesterone concentrations between days -10 and 0 than eCG-treated and control ewes. Expression of estrus was similar among the three groups and intervals to onset of estrus were shorter (P<0.01) in RJ-treated (31.3h) and eCG-treated (29.8h) than control (41.3h) ewes. First-cycle pregnancy and lambing rates were greater (P<0.05) in RJ-treated (71.4 and 71.4%) and eCG-treated (85.7 and 78.6%) than in control (42.9 and 35.7%) ewes, respectively. Results demonstrate that the treatments of RJ and eCG in conjunction with CIDR-G were similarly effective in induction of estrus and improvement of pregnancy and lambing rates.

Effect of feeding level on progesterone concentration in early pregnant multiparous sows

The effect of three feeding regimens on progesterone level was tested during early pregnancy in multiparous sows. A total of eighteen sows in their eighth parity (8.1 +/- 2.8, mean +/- S.D.) were used. During lactation the sows were fed to appetite and after weaning they received 4 kg (52 MJ) a commercial feed per day. Following ovulation, sows were allocated to one of three treatment groups and fed 2 kg/day (low feeding, LLL) or 4 kg/day (high feeding, HHH) throughout the trial or 2 kg/day for 11 days, 4 kg/day for 10 days, and 2 kg/day for the remaining days of the study (modified feeding, LHL). Blood for progesterone and cortisol analyses was collected daily throughout the study, and for luteinizing hormone (LH) assay for 12 h at 15 min intervals on days 14 and 21 of pregnancy. An adrenocorticotropic hormone (ACTH) challenge test was performed on all sows day 28 of pregnancy. Dietary treatment did not significantly affect hormonal parameters. However, progesterone concentration tended to be lower (P = 0.08) in the HHH group than in the LLL group. In the LHL group venous progesterone concentration seemed to fluctuate. No effects of feeding were observed on progesterone concentration in allantoic fluid on day 35 of pregnancy. Venous cortisol level was significantly higher (P < 0.05) during proestrus and oestrus in all groups and there was no significant difference between groups in response to ACTH challenge. The mean amplitude of LH pulses decreased significantly (P < 0.01) from days 14 to 21 of pregnancy in all groups. In addition, an interaction was found between feeding level and baseline LH concentration and also between feeding level and mean LH concentration. Embryonic recovery was highest in the LLL (69%), lowest in the HHH (45%) and moderate in the LHL (55%) group. Neither high feeding nor modified feeding provided any benefits for reproductive performance in multiparous sows. A low feeding regimen thus appears optimal for multiparous sows in early pregnancy at least with the management regime described.

Effects of feed restriction on reproductive and metabolic hormones in ewes

The goal of this study was to determine the effects of short-term feed withdrawal on reproductive and metabolic hormones during the luteal phase of the estrous cycle in mature ewes. Mature ewes observed in estrus were assigned randomly to control and fasted groups (n = 10 per group Trials 1 and 2). For Trials 1 and 2, control ewes had ad libitum access to feed, whereas fasted ewes were not fed from d 7 through 11 of their estrous cycle; on d 12, all ewes were treated with 10 mg of PGF2alpha, and fasted ewes were gvien ad libitum access to feed. For Trial 1, blood samples were collected daily through fasting and at 2-h intervals following PGF2alpha for 72 h. Serum concentrations of insulin (P < or = 0.002) and IGF-I (P < or = 0.01), but not GH (P > or = 0.60), were decreased during fasting compared with fed ewes. Serum concentrations of 29 (P = 0.02) and 34 kDa (P = 0.04) IGFBP were greater in fasted ewes at 96 h after initiation of fasting than in control ewes. Two control and four fasted ewes in Trial 1 did not exhibit a preovulatory surge release of LH by 72 h. Therefore, Trial 2 was conducted so that the timing of the LH surge could be predicted following the collection of blood samples at 2-h intervals for 112 h and then at 6-h intervals until 178 h following PGF2alpha administration and realimentation. The magnitude of the preovulatory LH surge in Trial 2 was decreased (P = 0.009) and delayed (P = 0.04), and serum concentrations of estradiol were diminished (P < or = 0.03) 12 h before the LH surge in fasted ewes. Ovulation rates were not influenced (P > or = 0.32) by fasting in Trials 1 and 2. Serum concentrations of progesterone in both Trials 1 and 2 were, however, greater (P < 0.001) in fasted than in control ewes. A third trial with ovariectomized ewes was conducted to determine whether the increased serum concentrations of progesterone observed in fasted ewes during Trials 1 and 2 were ovarian-derived. Ovariectomized ewes were implanted with progesterone-containing intravaginal implants and allotted to control (n = 5) or fasted (n = 5) treatment groups and fed as described for Trials 1 and 2. Similar to intact ewes, serum concentrations of progesterone were approximately twofold greater (P < 0.001) in fasted than in control implanted ovariectomized ewes. In summary, feed withdrawal for 5 d during the luteal phase of the estrous cycle increased serum concentrations of progesterone and evoked endocrine changes that could perturb the subsequent estrous cycle.

Increasing feed intake in late gestation does not affect plasma progesterone concentration in the sow

Rate of decline in plasma progesterone concentration may influence the success of lactogenesis in the sow. The aim of this experiment was to investigate whether progesterone concentration and rate of decline of progesterone in the periparturient sow could be manipulated by changing her feeding level. Forty-two sows received either 1.15 or 2 times maintenance energy daily from day 100 of gestation up until and including the day of farrowing. Blood samples were taken on days 98 (pre-treatment baseline) and 109 of gestation, during farrowing, 6h after farrowing and at 09:00 h for the 3 days following farrowing. Plasma progesterone concentration was determined and progesterone half-life was calculated for each sow. High intake feeding had no effect on plasma progesterone concentration at any time of sampling. Progesterone half-life averaged 41.2 +/- 3.81 h and did not differ between treatments. There was no relationship between progesterone concentration, or half-life, and litter weight gain, although there was a weak correlation between decline in progesterone in the first 6h after birth and piglet growth rate from birth to 6 days of age (R(2) = 0.109, P < 0.05). It was concluded that increasing feed intake in late gestation cannot be used to increase progesterone clearance rate and hasten the onset of lactogenesis in sows.

Reproductive responses following royal jelly treatment administered orally or intramuscularly into progesterone-treated Awassi ewes

An experiment was conducted to determine whether natural royal jelly (RJ) paste administered orally or intramuscularly (i.m.) in conjunction with exogenous progesterone is associated with improved reproductive responses in ewes. Thirty 3-6-year-old Awassi ewes were randomly allocated into three (RJ-capsule, RJC; RJ-injection, RJI and control, CON) groups of 10 ewes each. All ewes were treated with intravaginal progesterone sponges for 12 days. Ewes in the RJC and RJI were administered orally or i.m. with a total of 3g of RJ given in 12 equal doses of 250 mg per ewe per day starting at the time of sponge insertion. At the time of sponge withdrawal (day 0, 0 h), ewes were exposed to three rams and checked for breeding marks at 6-h intervals for 3 days. Blood samples were collected from all ewes for analysis of progesterone concentrations. Pretreatment progesterone levels were <0.5 ng x ml(-1) in 16/30 and >1.3 ng x ml(-1) in the remaining ewes indicating luteal function and cyclicity. Similar reproductive responses and progesterone levels occurred in ewes of the RJC and RJI; therefore, data of the two groups were pooled. Following sponge insertion, progesterone levels increased rapidly and reached maximum values of 5.8+/-0.2 ng x ml(-1) within 2 days among ewes of the three groups, and then declined gradually to day 0 values of 1.6+/-0.1 and 1.9+/-0.1 ng x ml(-1) for the RJ-treated and CON ewes, respectively. The rate of progesterone decline was greater (P<0.001) in RJ-treated than in CON. Mean progesterone levels during the 12-day period were lower (P<0.001) in RJ-treated than in CON (2.8+/-0.2 ng x ml(-1) versus 3.3+/-0.2 ng x ml(-1)). Treatment with RJ resulted in greater (P<0.05) incidence of oestrus and shorter (P<0.05) intervals to onset of oestrus than CON. Based upon progesterone levels, ovulation occurred following day 0 in all ewes. Progesterone increased on day 3 in RJ-treated and on day 4 in CON ewes. Progesterone remained elevated through day 18 in 8/20 RJ-treated and 1/10 CON ewes (P=0.09). All pregnant ewes exhibited oestrus 14 h earlier (P<0.02), ovulated approximately 1 day earlier and had higher (P<0.001) luteal phase progesterone levels than non-pregnant ewes. Non-pregnant had higher (P<0.04) body weights than pregnant ewes. In conclusion, results demonstrate that both RJ treatments in conjunction with exogenous progesterone were equally capable of improving oestrus response and pregnancy rate.

High feed intake increases liver blood flow and metabolism of progesterone and estradiol-17beta in dairy cattle

Increased liver blood flow (LBF) resulting from elevated feed intake in lactating dairy cows may increase steroid metabolism. Continuous infusion of bromosulphthalein (BSP; specifically metabolized in liver) was used to measure LBF. Similarly, progesterone (P4) and estradiol-17beta (E2) were administered by continuous infusion. Circulating concentrations at steady state were used to calculate the metabolic clearance rate (MCR) of BSP, P4, and E2. Experiment 1: Variation in LBF was determined in thee nonlactating and four lactating cows over 3 d at 3 to 5 h after feeding. Coefficients of variation ranged from 14 to 31% among cows within day and from 4 to 8% within cows across days. Experiment 2: Six nonlactating cows were used in a 3 x 3 Latin-square design with three feed regimens: no feed, 0.5 maintenance diet (M), and 1.5 M. Experiment 3: Eight lactating cows were used in a 4 x 4 Latin-square design with four feed regimens: no feed, 0.5 M, 1.5 M, and 2.2 M. In experiments 2 and 3, LBF and MCR of P4 increased immediately after feed consumption and increases persisted longer at higher intakes. The LBF reached a maximum at 2 h after feeding and MCR of P4 reached maximum at 3 h after feeding with a positive correlation (r = 0.92) between LBF and MCR for P4. Experiment 4: A crossover design was used to determine MCR of E2 in unfed or full-fed lactating dairy cows. The MCR of E2 increased immediately after feeding and stayed elevated throughout the 4.5-h infusion period. Thus, LBF and steroid metabolism were acutely elevated by feed consumption in lactating and nonlactating cows. Higher rates of LBF and steroid metabolism in lactating than in nonlactating cows may indicate chronic effects of higher feed intakes as well.