Prepuberal evolution of plasma leptin levels in gilts of thrifty genotype (Iberian pig) and lean commercial crosses (Large White × Landrace)

Current study aimed to determine possible differences in plasma leptin levels during the prepuberal period and their relationship with the onset of puberty in gilts of obese thrifty genotype (Iberian breed) and lean genotype (Large White × Landrace commercial crosses) reared under similar conditions. Plasma leptin concentration increased linearly during the 7 weeks prior to the day of puberty attainment in both genotypes (P<0.005, r=0.707 for LW × L and P<0.0005, r=0.874 for Iberian gilts). However, leptin levels in the Iberian gilts was higher from the first sample of the experimental period, with females having 16 weeks-old (2.7±0.3 vs 1.7±0.2 ng/ml in LW × L; P<0.001), to the onset of puberty (8.5±0.7 vs 2.8±0.3 ng/ml in LW × L; P<0.005). Thus, the current study reinforces previous data on changes in around puberty and evidences, for the first time, profound differences in prepuberal plasma leptin levels between gilts of obese (Iberian) and lean genotypes (LW×L).     

Preovulatory follicle development in goats following oestrous synchronization with progestagens or prostaglandins.

The study reports on differences in the dynamics of growth and functionality of preovulatory follicles in response to oestrous synchronization, either by the administration of two doses of prostaglandin or by an intravaginal progestagen sponge, in goats. The progestagen-treated group (n = 8) showed more follicles of preovulatory size (> or =5.5 mm) than the cloprostenol group (n = 8) during the follicular phase (4.5 +/- 0.6 vs 1.9 +/- 0.2, p < 0.01). The diameters of the largest follicles (LF1, LF2 and LF3) were also larger in the progestagen group (LF1, 7.8 +/- 0.3 vs 7.0 +/- 0.2 mm, p < 0.05; LF2, 6.7 +/- 0.2 vs 5.6 +/- 0.2 mm, p < 0.01; LF3, 5.5 +/- 0.3 vs 4.2 +/- 0.2 mm, p < 0.01). The study of the preovulatory follicles showed that 27.2% (3/11) of the follicles were in the static phase in the cloprostenol group, whilst 71.4% (10/14) were static in progestagen group (p < 0.05). Higher plasma oestradiol levels were recorded in the progestagen-treated goats during the 48 h prior to cloprostenol injection or progestagen withdrawal (4.2 +/- 0.4 vs 3.0 +/- 0.2 pg/ml, p < 0.05). In conclusion, goats with oestrus synchronized by progestagen showed a higher number of preovulatory-sized follicles, but a decreased oestradiol secretion when compared with does with oestrus synchronized by using prostaglandin analogues. These would support the development of alternative protocols for assisted reproduction.     

Pharmacokinetics of meloxicam after intravenous,intramuscular and oral administration of a single dose to African grey parrots (Psittacus erithacus)

Meloxicam is a nonsteroidal anti‐inflammatory drug commonly used in avian species. In this study, the pharmacokinetic parameters for meloxicam were determined following single intravenous (i.v.), intramuscular (i.m.) and oral (p.o.) administrations of the drug (1 mg/kg·b.w.) in adult African grey parrots (Psittacus erithacus; n = 6). Serial plasma samples were collected and meloxicam concentrations were determined using a validated high‐performance liquid chromatography assay. A noncompartmental pharmacokinetic analysis was performed. No undesirable side effects were observed during the study. After i.v. administration, the volume of distribution, clearance and elimination half‐life were 90.6 ± 4.1 mL/kg, 2.18 ± 0.25 mL/h/kg and 31.4 ± 4.6 h, respectively. The peak mean ± SD plasma concentration was 8.32 ± 0.95 μg/mL at 30 min after i.m. administration. Oral administration resulted in a slower absorption (t_max = 13.2 ± 3.5 h; C_max = 4.69 ± 0.75 μg/mL) and a lower bioavailability (38.1 ± 3.6%) than for i.m. (78.4 ± 5.5%) route. At 24 h, concentrations were 5.90 ± 0.28 μg/mL for i.v., 4.59 ± 0.36 μg/mL for i.m. and 3.21 ± 0.34 μg/mL for p.o. administrations and were higher than those published for Hispaniolan Amazon parrots at 12 h with predicted analgesic effects.     

Timing of preovulatory LH surge and ovulation in superovulated sheep are affected by follicular status at start of the FSH treatment.

The aims of this study were to evaluate the chronology of periovulatory events (oestrus behaviour, LH surge and ovulation) in 16 superovulated Manchega sheep and to determine whether follicular status at start of the FSH supply might affect their occurrence. Mean timing for onset of oestrus behaviour was detected at 28.1 +/- 0.7 h after sponge withdrawal; the preovulatory LH surge and ovulation started at 37.2 +/- 0.7 h and 65.4 +/- 0.7 h after progestagen withdrawal, respectively. The intervals between oestrus, LH surge and ovulation were affected by a high individual variability, which might be the cause for reported decreased efficiency in embryo production. Current results also addressed the role of follicular status at start of the superovulatory treatment on the preovulatory LH surge and the ovulation. The interval LH surge-ovulation was increased in ewes with a growing dominant follicle at starting the FSH treatment (32.3 +/- 0.9 vs 28.6 +/- 0.5 h, p < 0.05). The developmental stage of the largest follicle at starting the superovulatory treatment also affected occurrence of LH surge and ovulation; follicles in growing phase advanced the occurrence of the LH surge and ovulation when compared to decreasing follicles (33.0 +/- 1.0 vs 43.5 +/- 1.1 h, p < 0.05, for LH peak and 60.7 +/- 1.1 vs 72.8 +/- 1.2 h, p < 0.05, for ovulation). Thus, only ewes with growing follicles ovulated prior to 55 h after sponge withdrawal; conversely, no sheep with decreasing follicles ovulated earlier than 67 h, when an 85.7% of the ewes bearing growing follicles has ovulated at 63 h.     

Influence of vehicle on kinetics of exogenous progesterone administered either by subcutaneous and intramuscular routes to sheep

This study aimed to determine the best vehicle and administration route for progesterone administration in sheep. In a first replicate, single intramuscular doses of 25mg progesterone were administered to ewes previously ovariectomized, either in propylene glycol (group IM-PG, n=6) or olive oil (group IM-OO, n=5). In a second replicate, the same solutions of progesterone were administered subcutaneously to the same ewes (groups SC-PG, n=6, and SC-OO, n=5). In the present study, the best pharmacokinetic results of a single dose of 25mg of progesterone were obtained, both using PG and OO as vehicles, by the subcutaneous route. Thus, progesterone remained in plasma for a longer time after subcutaneous administration in PG than in OO (t(1/2beta): 60.65+/-13.07 vs. 27.51+/-3.59 h; P<0.05); the mean residence time being higher in SC-PG than in SC-OO group (88.99+/-18.36 vs. 41.04+/-5.31h; P<0.05). However, both vehicles allowed maintained plasma levels 0.5 ng/ml for at least 30 h, so any of these treatments may be efficiently used for administration of exogenous progesterone.     

Effects of Breed on Follicular Dynamics and Oestradiol Secretion during the Follicular Phase in Sheep

Current study evaluates effects from breed and management background on follicular dynamics and endocrine output during the follicular phase of sheep oestrous cycle. Follicular phases were synchronized with three cloprostenol doses, 10 days apart, in three groups of 10 females of different non-prolific Spanish breeds (Manchega, Rubia del Molar and Negra de Colmenar). Development of all follicles reaching antral diameters >or=2 mm was assessed by daily transrectal ultrasonographies, whereas follicular function was evaluated by measurement of plasma oestradiol concentrations. All the ovulatory follicles were present at induced luteolysis in Manchega sheep, while a 93.7% were detected in Rubia del Molar and Negra de Colmenar ewes. The mean size of these ovulatory follicles was similar between breeds at 0 h, but their growth rates were higher in Manchega ewes, reaching a larger size at oestrous detection than in Negra de Colmenar and Rubia del Molar sheep (p < 0.05). Conversely, the oestradiol levels increased with time in Rubia del Molar and Negra de Colmenar (p < 0.05); whilst remained stable in Manchega females. However, the patterns of follicular turnover were similar between breeds. These results indicate that, though differences in follicular size and size distribution, patterns of follicular turnover in sheep are affected neither by the breed nor by the background of management and selection.     

Pharmacokinetics of indomethacin in sheep after intravenous and intramuscular administration

The pharmacokinetics of indomethacin (1mg/kg) was determined in six adult sheep after intravenous (i.v.) and intramuscular (i.m.) injection. Plasma concentrations were maintained within the therapeutic range (0.3–3.0 μg/mL) from 5 to 50 min after i.v. and from 5 to 60–90 min after i.m. administration. After two trials, indomethacin best fitted an open two-compartment model. The mean (±SD) volumes of distribution at steady state ( V d_ss) were 4.10 ± 1.40 and 4.21 ± 1.93 L/kg and the mean clearance values ( C l_B) were 0.17 ± 0.06 and 0.22 ± 0.12 L/h.kg for i.v. and i.m. routes, respectively. The elimination phase half-lives did not show any significant difference between routes of injection ( t _½β = 17.4 ± 4.6 and 21.25 ± 4.44 h, i.v. and i.m. respectively). After i.m. administration, plasma maximum concentration ( C _max =  1.10 ± 0.68 μg/mL) was reached 10 min after dosing; the absorption phase was fast ( K _ab = 26 ± 18 h-1) and short ( t _½ab = 2.33 ± 1.51 min) and the mean bioavailability was 91.0 ± 32.8%, although there was considerable interanimal variation. In some individuals, bioavailability was higher than 100%. This fact combined with the slower elimination phase after i.m. than after i.v. administration, could be related with enterohepatic recycling.     

Administration of single short-acting doses of GnRH antagonist modifies pituitary and follicular function in sheep

Current study determined the effect of two different single subcutaneous doses (1.5 and 3 mg) of GnRH antagonist (GnRHa) on pituitary and follicular function in non-lactating cyclic ewes. Both doses abolished the pulsatile secretion of luteinizing hormone (LH) for at least 3 days and decreased mean LH concentration during 6 days (0.64 +/- 0.09 for control and 0.54 +/- 0.05, P < 0.005, and 0.46 +/- 0.02, P < 0.00001, for 1.5 and 3 mg, respectively). Supply of GnRHa decreased the number of large dominant follicles, so the total number of smaller follicles, 2-3 mm in size, increased in both treated groups from day 0, reaching its maximum at day 2 in ewes treated with 1.5 mg (19.83+/-1.05 versus 5.83 +/- 0.50 in the control, P < 0.005) and at day 4 in sheep treated with 3mg (18.67 +/- 0.65 versus 5.50 +/- 0.65 in the control, P < 0.0001). However, the analysis of follicular function in terms of inhibin A indicated a possible effect of the higher dose of GnRHa on follicular function. The pattern of inhibin secretion in the group treated with 3mg of GnRHa decreased after the first 48 h, reaching its lowest value on day 4.5 (182.59 +/- 3.75 to 140.28 +/- 9.91 pg/ml, P < 0.05) concentration significant lower than control sheep (171.93 +/- 6.21 pg/ml, P +/- 0.01) or treated with 1.5 mg (168.04 +/- 7.16 pg/ml, P+ /- 0.05). Hence, the use of 1.5 mg would be more suitable to induce the presence of a high number of follicles able to grow to preovulatory sizes.     

Onset of oestrus and periovulatory events in sheep exposed to 5 and 14 days of CIDR treatment with and without eCG

The present study supports that 5‐day short‐term CIDR treatments without administration of eCG are equally effective for inducing oestrus behaviour, preovulatory LH discharge and ovulation in sheep than classical protocols based on 14‐day treatments plus eCG at CIDR withdrawal. However, the implementation of a 5‐day protocol without eCG for fixed‐time artificial insemination would be adapted to a later timing of ovulation (p < .05).