Long-term effects of different handling procedures on behavioural, physiological, and production-related parameters in silver foxes

Fifty-one silver fox vixens, subjected to three different handling treatments as cubs (no-handling, gentle or forced handling), were studied for long-term effects on behavioural, physiological and production-related parameters in a one and a half year period following the last handling session. As juveniles, the animals were exposed to three different behavioural tests at 18, 22, 28, and 32 weeks of age. Both forcibly and gently handled animals showed reduced fear responses compared with nonhandled controls in test situations involving close contact with humans (P < 0.05). The foxes were tested again as adults at 10, 13, 15, and 18 months of age with the same behavioural tests. It was revealed that forcibly handled animals persistently showed reduced fear responses compared with control animals, both in close contact with humans and when exposed to a novel object, whereas gently handled animals only differed from control animals in one of the tests involving some human contact and when exposed to a novel object (P < 0.05). Significant differences between adult gently handled and forcibly handled animals were found in the “confront’ test involving close human contact. In this test more flight responses were observed in the gently handled group than in the forcibly handled group (P < 0.01). Control animals had significantly larger adrenal weights compared with both forcibly handled animals and gently handled animals at 22 months of age (total mean adrenal weight: controls, 0.62 g; gentle, 0.54 g; forced, 0.54 g, P < 0.05, general linear models). Other physiological measures and production-related parameters such as body weight, body size, gastric ulceration and pelt qualities did not differ between treatments (P > 0.05). Early post-weaning handling made foxes less fearful towards humans. Forced handling seemed somewhat superior to gentle handling as a means to produce animals which, in the long term, adapted better to the farm environment both behaviourally and physiologically. Non-handled control animals suffered from long-term stress as reflected by high levels of fear responses and enlarged adrenals. Thus post-weaning handling may be beneficial in the long term for the wellbeing of farmed foxes. When applied as a management routine, handling had no significant influence on later production-related parameters and was not considered an economic risk.     

Pregnancy diagnosis based on the fecal progesterone concentration in beef and dairy heifers and beef cows

The present study was undertaken to examine whether pregnancy diagnosis was possible by measuring fecal progesterone concentrations in beef and dairy heifers and beef cows. Rectal fecal samples collected on days 18–24 after insemination or days 11–17 after embryo transfer were mixed with methanol and shaken for preparation of a fecal solution. After centrifugation, the supernatant was extracted with petroleum ether followed by an enzyme immunoassay for progesterone. All pregnant animals showed fecal progesterone concentrations greater than 50 ng/g of fecal material on days 18–24 after AI or estrus. In non-pregnant animals, however, the fecal progesterone concentrations ranged widely from 5 to 180 ng/g of fecal material. In non-pregnant cattle, the percentage of cattle with <50 ng progesterone/g of fecal material compared with the total number was 37–60% on days 18–20, whereas the percentages increased more than 70% to a maximum of 78.1% on day 23. When 50 ng/g was considered as the cut-off value, the sensitivity and specificity of positive pregnancy tests were less than 70% on days 21–24, and 100% for negative pregnancy tests on days 18–24. There were significant differences in the mean fecal progesterone concentrations between pregnant and non-pregnant cattle on days 19–24. These results suggest that feces can be utilized to substitute for plasma and milk to measure progesterone for the purpose of pregnancy diagnosis in heifers and cows.     

Behaviour during the first stage of labour in cattle: Influence of parity and dystocia

The aim of the study was to examine typical behavioural elements in suckling cows and heifers at the first stage of labour and how these are affected by parity and dystocia. For this purpose, the parturitions of 87 cattle (10 Simmental heifers; 77 multiparous cows, 55 Simmental, 21 Simmental × Limousin) were observed from the appearance of the amniotic sacs in the cervix up to the emergence of the foetal phalanges in the rima vulvae. The animals were divided into three groups: group 1—cows with eutocia, n = 68; group 2—heifers with eutocia, n = 10; group 3—cows with dystocia, n = 9.

Compared to cows, there was a lower proportion of heifers with calm behaviour, whereas a higher proportion of heifers showed pawing with the forefeet (P < 0.05).

There was a higher proportion of cows with dystocia which showed rubbing against the wall (P < 0.05), discharge of urine (P < 0.05) and scraping on the floor (P < 0.05) compared to cows with eutocia.

The differences in behaviour of cows and heifers should be considered in a system for monitoring parturition to avoid misconstruing the normal calving situation and to obviate unnecessary obstetric intervention in heifers. Behavioural elements which were more frequently detectable in cases of dystocia should draw attention to the possibility that there may be a problem in the first stage of labour.     

Synergistic anti-proliferative effects of vitamin D derivatives and 9-cis retinoic acid in SH-SY5Y human neuroblastoma cells.

This study examines the effect of 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], 24,25-dihydroxyvitamin D₃ [24,25(OH)₂D₃], two vitamin D analogues (KH 1060 and EB 1089, which are 20-epi-22-oxa and 22,24-diene-analogues, respectively), 9-cis retinoic acid and all-trans retinoic acid on proliferation of SH-SY5Y human neuroblastoma cells, after treatment for 7 days. Cell number did not change when the cells were incubated with 1, 10 or 100 nM 1,25(OH)₂D₃ or its derivatives, but significantly decreased in the presence of the two retinoids (0.001–10 μM final concentration). A synergistic inhibition was observed, when SH-SY5Y cells were treated combining 0.1 μM 9-cis retinoic acid and 10 nM 1,25(OH)₂D₃ or 10 nM KH 1060, and 1 μM 9-cis retinoic acid and 10 nM 1,25(OH)₂D₃ or 10 nM EB 1089. Acetylcholinesterase activity showed a significant increase, in comparison with controls, after treatment of the cells for 7 days with 0.1 or 1 μM 9-cis retinoic acid, alone or combined with 10 nM 1,25(OH)₂D₃ or 10 nM KH 1060 or 10 nM EB 1089. This increase was synergistic, combining 1 μM 9-cis retinoic acid and 10 nM 1,25(OH)₂D₃ or EB 1089. The levels of the c-myc encoded protein remarkably decreased after treatment of SH-SY5Y cells for 1, 3, 7 days with 0.1 and 1 μM 9-cis retinoic acid, alone or combined with 10 nM 1,25(OH)₂D₃ or 10 nM KH 1060 or 10 nM EB 1089. In particular, the association of 1 μM 9-cis retinoic acid and 10 nM 1,25(OH)₂D₃ or 10 nM EB 1089 resulted in a synergistic c-myc inhibition, in comparison with that obtained in the presence of the retinoid alone. These findings may have therapeutic implications in human neuroblastoma.     

Effect of LH or GnRH on the dominant follicle of the first follicular wave in beef heifers

A study was designed to characterise ovarian follicular dynamics in heifers treated with porcine luteinizing hormone (pLH) or gonadotropin releasing hormone (GnRH) on days 3, 6 or 9 (ovulation = day 0), corresponding to the growing, early-static, and late-static phases of the first follicular wave. Following ovulation, 65 beef heifers were assigned, by replicate, to the following seven treatment groups: 25 mg im of pLH on days 3, 6 or 9 (n = 9 per group); 100 microg im of GnRH on days 3, 6 or 9 (n = 9 per group); or controls (no treatment; n = 11). Ovulation occurred within 36 h in 67%, 100% and 67% of heifers treated with pLH and in 89%, 56% and 22% of heifers treated with GnRH on days 3, 6 or 9, respectively (treatment-by-day interaction, P < 0.09). Combined for all treatment days, ovulation rates were 78% and 56% in pLH- and GnRH-treated groups, respectively (P < 0.09). Overall, mean day (+/- SD) of emergence of the second follicular wave in heifers that ovulated was different from that in controls or in heifers that did not ovulate (P < 0.05). Mean (+/- SD) day of emergence of the second wave occurred earlier (day 5.6+/-1.2; P < 0.05) in heifers that ovulated after treatment on day 3 (n = 14) than in controls (day 8.7+/-1.6; n = 11); however, wave emergence in all heifers treated on day 6 (day 8.1+/-0.5; n = 18) did not differ from controls, regardless of whether or not ovulation occurred. In the heifers that ovulated in response to treatment on day 9 (n = 8), the emergence of the second follicular wave was delayed (day 10.9+/-0.4; P < 0.05). The day of emergence of the second wave in the 14 treated heifers that failed to ovulate, irrespective of the day of treatment (day 8.9+/-1.4) did not differ from control heifers. The emergence of the second wave was more synchronous in day 6 heifers (regardless of whether they ovulated) and in day 9 heifers that ovulated compared to control heifers (P < 0.05). Results did not support the hypothesis that the administration of pLH or GnRH at known stages of the follicular wave in cycling heifers would consistently induce ovulation or atresia and, thereby, induce emergence of a new follicular wave at a predictable interval. New wave emergence was induced consistently (1.3 days post-treatment) only in those animals that ovulated in response to treatment. However, 22% of LH-treated heifers and 44% of GnRH-treated heifers failed to ovulate. Treatments did not induce atresia of the dominant follicle or alter the interval to new wave emergence in animals that did not ovulate in response to treatment.     

Superovulation using recombinant human FSH and ultrasound-guided transabdominal follicular aspiration in baboon (Papio anubis)

The response of baboon females to a modified human ovarian stimulation protocol incorporating start of pituitary suppression in the luteal phase of the cycle with a GnRH agonist (GnRHa) and recombinant human FSH (rhFSH) was studied. A long-acting GnRHa implant supplying goserelin acetate was administered s.c. to six adult female baboons experiencing regular menstrual cycles (33–34 days) on days 22–24 of the cycle. Follicular development was monitored by transabdominal ultrasonography and serum levels of E2 and progesterone (P4) and rhFSH were determined by ELISA. Menses occurred 9–10 days after GnRHa administration. Daily i.m. administration of 75 IU rhFSH commenced 9–10 days after menses and continued for 9–10 days. When most follicles were ≥5 mm diameter and serum E2 had reached its maximum level, 2000 IU hCG was administered i.m. to induce follicle maturation. Transabdominal ultrasound-guided follicular aspiration of follicles ≥2 mm diameter was performed 30–34 h after hCG administration.

One baboon did not show an adequate response to rhFSH stimulation. This animal did not receive further treatment and no data for it are presented. The number of follicles aspirated was 21±4 and 17.2±3.8 oocytes were recovered per animal with an average recovery rate of 82% (86/105). The number of oocytes collected from five animals were 14, 21, 16, 15, and 20 (n=86). Most of the oocytes recovered were in metaphase II and 3 h after recovery 91% (78/86) were considered suitable for in vitro fertilization. It was concluded that recombinant human FSH can successfully induce follicular recruitment and oocyte maturation in baboon females during pituitary suppression with a GnRHa     

Sequential endocrine changes and behaviour during oestrus and metoestrus in repeat breeder and virgin heifers

The aim of the experiment was to study the oestrous behaviour and the peripheral blood plasma profiles of luteinizing hormone (LH), progesterone and the prostaglandin metabolite, 15-keto-13,14-dihydro-PGF₂, during oestrus and metoestrus in repeat breeder (RBH) and virgin heifers (VH). Ten animals of each category were utilized. The RBH had a history of at least three inseminations without conception, and the VH were sexually mature animals not previously inseminated or mated. Oestrous symptoms were recorded and blood collected from the onset of prooestrus to 7 days after oestrus. The animals were inseminated during oestrus and their embryos were collected by a nonsurgical technique 7 days after insemination. The morphology of the embryos was evaluated.

The duration of oestrus was longer (P < 0.05) in the RBH (31.5 ± 3.6 h) than in the VH (23.8 ± 2.0 h). No differences in duration of prooestrus or in the interval from the end of oestrus to postoestrous bleeding were found between the heifer categories. The interval from the onset of oestrus to the preovulatory LH peak was longer (P < 0.05) in the RBH (12.2 ± 2.8 h) than in the VH (4.8 ± 1.5 h). There was a lower LH release in the RBH than in the VH, measured as the magnitude of the preovulatory LH peak (P < 0.05; 28.0 ± 4.0 vs. 40.7 ± 3.6 μg/l) or as the area under the curve of the LH peak (P < 0.01; 1141 ± 164 vs. 1765 ± 144 mm²). The progesterone levels were higher (P < 0.05) in the RBH than in the VH during the interval 5–48 h and lower (P < 0.05) during the interval 121–168 h after the LH peak. Peaks of the prostaglandin metabolite were seen during oestrus in both heifer groups. There were more prostaglandin metabolite peaks in the RBH than in the VH during the interval 13–24 h after the LH peak. Fewer normal embryos (P < 0.05) and more degenerated embryos (P < 0.01) were found in the RBH than in the VH group 7 days after insemination. No apparent relation was found between the morphology of the embryos and the hormonal changes.

The result of the study indicates a hormonal imbalance in the RBH. The hormonal asynchronism starts before or early in oestrus, which presumably leads to a sequence of improper hormonal changes responsible for the elevated embryonic loss in repeat breeder animals.     

Gonadotrophin secretion and ovarian responses in prepubertal heifers actively immunized against androstenedione and oestradiol-17 beta

Groups of heifer calves received a primary immunization against androstenedione (Group A; N = 11) or oestradiol-17 beta (Group E; N = 10) at 3 months of age and booster injections on 5 occasions at 2- to 3-month intervals. Controls (Group C, N = 11) were immunized against human serum albumin alone using the same protocol. Immunity was achieved against both steroids as judged by the secondary antisteroid antibody titres in Group A (1126 +/- 261; reciprocal of titre) and Group E (10,357 +/- 4067) heifers. In Groups A and E there was a general decline in the respective peak antibody titres after successive booster injections. From 3 to 9 months of age mean plasma concentrations of LH were higher (P less than 0.05) in Group E heifers (0.89 +/- 0.08 ng/ml) than in Group C (0.46 +/- 0.03 ng/ml) and Group A (0.59 +/- 0.05 ng/ml) heifers which did not differ from one another. There were no differences between groups in plasma FSH concentrations. At 10 months of age the LH response to exogenous LHRH was of higher (P less than 0.05) amplitude for heifers in Group E (2.59 +/- 0.56 ng/ml) than for those in Groups C (0.61 +/- 0.07 ng/ml) and A (1.04 +/- 0.22 ng/ml). Elevated plasma progesterone concentrations at 5 months of age were shown by 2 heifers in Group C, 10 in Group A, and 6 in Group E. From 8 to 14 months of age a consistently higher proportion of Group A heifers exhibited elevated progesterone compared with Group C and Group E heifers. After ovarian synchronization and booster injection at 15 months of age a corpus luteum was present in 2 heifers in Group C, 7 in Group A and none in Group E. The ovaries of Group A heifers were different from those of Groups C and E and were characterized by greater numbers of 2-4 mm follicles. It is concluded that active immunization against gonadal steroids influences both LH secretion and ovarian function in prepubertal heifers. Early increases in ovarian activity in androstenedione-immunized heifers are maintained after puberty and may therefore confer some lifetime reproductive advantages.     

Assessing the quality of products from cloned cattle: an integrative approach

Scientific expertise was developed during a 3-year study to evaluate a large number of bovine female clones (n=37; from 4 to 36 months of age) and their products through a multidisciplinary approach and compare them to non-cloned breed, age and sex-matched contemporary control animals (n=38) maintained under the same conditions at the same experimental farm of INRA. In clone and control groups, most parameters measured for health and development of the animals as well as evaluation of milk and meat products were within the normal range for the breed. The strict comparison between cloned animals and controls allowed us to detect slight significant differences between the two groups. Cloned heifers reached puberty significantly later (+62 days) and at higher body weight (+56kg) than controls. There were slight differences in antigen-specific induced proliferation of lymphocytes after vaccination with ovalbumin before 10 months of age, but responses were normal responses in older animals. There were differences in the fatty acid (FA) composition of milk and muscle arising from two families of clones, suggesting a possible deviation in lipid metabolism as assessed by higher Delta-9 desaturase activity indices in both milk and muscle from clones compared to controls. Nutritional evaluation of milk and meat using the rat model did not reveal any difference between products derived from clones versus controls.     

Physiological changes in the Norway lobster Nephrops norvegicus (L.) escaping and discarded from commercial trawls on the West Coast of Scotland: II. Disturbances in haemolymph respiratory gases, tissue metabolites and swimming performance after capture and during recovery

The physiological states of trawled and creel-caught (control) Norway Lobsters (Nephrops norvegicus (L.)) captured on grounds off the West Coast of Scotland (120–150 m) were compared. Undersized “discards” (<25–35 mm carapace length) were sampled directly from the cod-end and following recovery in underwater (u/w) cages at a mean depth of 24 m. “Escaped” animals which had passed through the cod-end meshes and collected in a small-meshed net “cover” were transferred without emersion (air-exposure) for sampling on-board. Some of these individuals were also transferred by SCUBA divers to u/w cages. Haemolymph PO₂, PCO₂ and pH measurements showed that both discarded and escaped animals experienced moderate internal hypoxia, hypercapnia and acidosis which became severe after 1 h emersion of the former on deck. A marked handling effect was evident in which haemolymph PO₂ declined and PCO₂ became elevated in both controls and recovering trawled animals. In both discarded and escaped animals haemolymph l-lactate and d-glucose concentrations were high compared to controls, but with levels significantly lower in escapes suggesting less tail-flip swimming activity within the cod-end cover. Further emersion had little effect on haemolymph l-lactate in discards. Recovery to control levels of both metabolites occurred within 24 h in u/w cages but the exercising of captured individuals (by tactile stimulation) produced further significant increases. Abdominal flexor muscle concentrations of l-lactate were also elevated in discards and escapes and positively correlated with haemolymph levels. Muscle glycogen showed severe depletion in both groups compared to unexercised controls and 1 h emersion reduced levels drastically (to 20% of normal concentrations). High haemolymph ammonia (T_amm) was characteristic of both trawled groups but was reduced rapidly during recovery. These metabolite changes were accompanied by reductions in the number of escape swimming tail-flips that could be elicited before exhaustion, particularly in discards. This reduction in performance was evident in discards even after 24 h recovery, but escapes showed almost normal responses. The severity of the physiological stresses experienced during trawling, and to a lesser extent in escaped animals, and their effects on recovery of undersized discards regaining the seabed, is discussed. These findings may help us predict the survival, longer-term recovery and fitness of fished N. norvegicus, and their potential contribution to the regeneration of exploited populations.     

Variable progesterone response and estradiol secretion in prepubertal beef heifers following treatment with norgestomet implants

Two experiments were conducted to determine the effects of norgestomet ear implants on progesterone response and estradiol secretion in prepubertal beef heifers. In the first experiment, 47 beef heifers were treated with norgestomet. The implants were implanted subcutaneously for 9 d. After implant removal, blood samples were taken from heifers 2 to 4 d per week for 40 d. Following progesterone determination in jugular venous plasma, heifers were classified according to their progesterone response: 1) no response (Group 1); no rise in progesterone above 1 ng/ml throughout the sampling period; 2) one cycle (Group 2); one increase in progesterone above 1 ng/ml for at least 2 d followed by no further increase in progesterone during the sampling period; and 3) two cycles (Group 3); a rise in progesterone above 1 ng/ml for at least 2 d followed by another cycle of normal duration. Heifers treated with norgestomet were classified as 23 with no response, 9 with 1 cycle and 15 with 2 cycles. Concentrations of estradiol were measured in jugular venous samples on Day 2 after implant removal. Mean concentrations of estradiol were greater in Group 3 than in Group 1 (P < or = 0.01). In Experiment 2, 29 prepubertal beef heifers were assigned randomly to either a 9-d treatment with norgestomet (n = 14) or to serve as untreated controls (n = 15). Blood plasma samples were collected daily from Days 0 to 44 after implant removal. After progesterone determination, heifers were classified as 8 with no response, 4 with 1 cycle and 3 with 2 cycles in the control group, and 5 with no response, 3 with 1 cycle and 6 with 2 cycles in the norgestomet group (frequencies did not differ; P > 0.1). Jugular venous blood plasma was also collected at 4-h intervals from 0 h to 96 h after implant removal and concentrations of estradiol were measured. Patterns of estradiol secretion differed (P < or = 0.05) and overall mean concentrations of estradiol over the first 96 h following implant removal were greater (P < or = 0.01) in norgestomet-treated heifers versus the controls. We conclude that norgestomet can produce a variable progesterone response with heifers with 2 cycles secreting more estradiol. Implants of norgestomet also causes more acute secretion of estradiol in prepubertal beef heifers.     

Effect of low levels of exogenous progesterone on puberty in beef heifers

Twenty eight prepuberal Charolais-Angus cross heifers approximately 15 months old and averaging 334 kg were implanted intravaginally with either a placebo (control, 9 heifers) or progesterone containing implant (treated, 19 heifers). Implants were left in place 3 days. Seventeen heifers (8 controls and 9 treated) retained implants. Plasma progesterone concentrations were < .4 ng/ml in control heifers and 1.5 +/- .59 ng/ml in treated heifers while implants were in place. Seven heifers, all in the treated group, were observed in estrus within 4 days after implant removal. All but one heifer observed in estrus had elevated plasma progesterone concentrations 12 days after implant removal. None of the heifers not observed in estrus had elevated progesterone levels at this time. This study indicates that low levels of exogenous progesterone (1 to 2 ng/ml plasma for 3 days) will induce estrus in prepuberal heifers following its withdrawal.     

Effects of constant and cycling hot environments on mitogen-stimulated proliferation of peripheral blood lymphocytes from sows and litters

1. 1. Lymphocytes from sows maintained in a constant hot environment (32°C) showed reduced proliferative responses to mitogens PHA (P < 0.02) and PWM (P < 0.01) in comparison to sown maintained in a constant cool environment (21°C). In the piglets the hot constant temperature slightly reduced (P < 0.05) proliferative responses of lymphocytes to PHA.

2. 2. No significant effects of a cycling hot environment (27–32°C) were found for any proliferative responses of lymphocytes from sows and litters.

3. 3. In the constant hot environment, serum cortisol concentrations were significantly reduced in the sows (P < 0.0001) while no differences in serum cortisol concentrations were found in the litters.

     

Conception, embryonic development and corpus luteum function in beef cattle open for two consecutive breeding seasons

High-fertility (control cows) and low-fertility (cows and heifers not pregnant after two consecutive breeding seasons — twice-open) cyclic bovine females were treated with a single injection of 1000 IU of human chrionic gonadotropin (HCG) or 100 μg of gonadotropin releasing hormone (GnRH) to enhance and/or hasten corpus luteum formation and progesterone secretion, and improve conception rate in the low-fertility females. Hormone treatments were administered to 38 parous control cows, 34 twice-open parous cows, and 27 twice-open nonparous heifers immediately after natural mating by a fertile bull. Blood samples were collected on Days 3, 6, 9, 12, and 18 after mating for determination of systemic progesterone concentrations. Pregnancy rate at necrospy approximately 33 days after mating (range 31–37) was higher in control cows (73.0%) than in twice-open cows (48.4%; P<0.05) or twice-open heifers (34.6%; P<0.01). Pregnancy rate was not affected by the HCG or GnRH treatment. The HCG treatment increased plasma progesterone concentrations in twice-open heifers but not in control or twice-open cows. Progesterone was unaffected by the GnRH treatment. Systemic progesterone concentrations were higher in control than in twice-open females but did not differ between pregnant and nonpregnant females of Days 3, 6, 9 and 12 after mating. Enhanced gonadotropin stimulation at estrus by injection of either HCG or GnRH did not increase pregnancy rate or systemic progesterone concentrations (except in HCG-treated twice-open heifers) in low- or high-fertility females. Lower pregnancy rates in twice-open females were not associated directly with the lower systemic progesterone concentrations.     

Inducing ovulation with hCG improves the fertility of dairy cows during the warm season

This study was designed to assess the effects of human chorionic gonadotrophin (hCG), given within a timed artificial insemination program, on plasma progesterone concentrations and subsequent fertility in lactating dairy cows during the warm and cold seasons of the year. Cows were treated intramuscularly with GnRH-agonist (Day 0) and PGF₂ (Day 7) followed by either GnRH-agonist (GPG treatment; 60 animals) or hCG (GPH treatment; 60 animals) on Day 9. All cows were fixed-time inseminated (TAI) 16–22 h after the end of treatment. To determine plasma progesterone levels, blood was withdrawn from all animals on Days 3, 6, 9, 12 and 15 after TAI. During the warm period, the pregnancy rate recorded at TAI was similar for the GPG and GPH groups (20% vs. 23%) while the cumulative pregnancy rate within 30 days of TAI was lower (P < 0.05) for the GPG than the GPH group (36% vs. 63%). No differences were observed during the cold period. During the warm period, embryo losses between Days 28 and 45 after TAI were greater (P < 0.05) for the GPG group compared to the GPH group (36% vs. 5%) while again no differences emerged during the cold period. Mean plasma progesterone levels were higher (P < 0.05) in the GPH group than GPG group on Days 3, 6 and 9 post-insemination. Our findings indicate that the use of hCG to induce ovulation in a timed artificial insemination protocol increases plasma progesterone levels and improves fertility in dairy cows during the warmer period of the year.     

Effect of steroid implants on sexual behavior of beef calves

The sexual behavior of 53 beef heifers and 66 beef steers was observed and recorded for 7 days following insertion of subcutaneous ear implants at 2 months of age. Thirty-five of the heifers were implanted with Synovex S (200 mg of progesterone and 20 mg of estradiol benzoate). Forty-four of the steers were implanted with Synovex H (200 mg of testosterone and 20 mg of estradiol benzoate). The remaining 18 heifers and 22 steers served as nonimplanted controls. Synovex S treatment increased the incidence of mounting (P < 0.005) and mounting receptivity (P < 0.005) of heifers, while Synovex H treatment had only slight effect, if any, on the mounting behavior (P < 0.25) and mounting receptivity (P < 0.25) of steers. Both steers and heifers mounted heifers more frequently than steers (P < 0.005). Heifers were mounted with similar frequencies by both heifers and steers (P < 0.90), while steers were mounted only by heifers (P < 0.15).     

Intrauterine Neospora caninum inoculation of heifers and cows using contaminated semen with different numbers of tachyzoites

OBJECTIVE: To investigate the potential of different Neospora caninum tachyzoite doses to infect heifers (experiment 1) and cows (experiment 2) when administered in utero by artificial insemination via contaminated semen. METHODS: In experiment 1, five groups of 5, 7, 8, 9, and 5 cyclic heifers were hormonally synchronized and artificially inseminated with semen containing 0 (A, controls), 10(2) (B), 5 x 10(3) (C), 5 x 10(4) (D), and 5 x 10(5) (E) live N. caninum NC-1 isolate-tachyzoites, respectively. Experimental infection was followed for 100 days. Parasitaemia and specific serum IgG, and interferon-gamma (IFN-gamma) responses were studied. In experiment 2, four groups of 9, 10, 9, and 9 adult multiparous cows with confirmed infertility problems of diverse aethiology were hormonally synchronized and artificially inseminated with semen containing 0 (a, controls), 10(2) (b), 5 x 10(3) (c), and 5 x 10(5) (d) live N. caninum NC-1 isolate-tachyzoites, respectively. Experimental infection was followed for 63 days. Parasitaemia and specific serum IgG responses were studied. RESULTS: In experiment 1, parasitaemia was detected in 1, 2, and 3 heifers from groups B, C, and D, respectively, between 9 and 23 days after insemination. Persistent specific serum antibody responses were detected in 2 and 3 heifers from groups D and E, respectively. Transient specific serum antibody responses were detected in 2, 1 and 1 heifers from groups C, D, and E, respectively. In addition, 1 heifer from group B showed a serum-specific antibody level higher than cut off value at 21 days post-insemination. Heifers seroconverted between 23 and 47 days after insemination. Specific IFN-gamma levels were detected in 1, 4, 6, and 3 heifers from groups B, C, D, and E, respectively, between 9 and 55 days after insemination. Pregnancy rate in the control group (60%) was higher than those observed in inoculated heifers (0-42.9%). Pregnancy rates in inoculated heifers were lower when the tachyzoite dose was increased (B 42.9%, C 12.5%, D 11.1%, and E 0%). In experiment 2, no Neospora DNA in blood nor specific serum IgG to N. caninum were detected in any of the cows studied, except in one cow inoculated with 5 x 10(5) tachyzoites (group d) which showed a relative index x100 (RIPC) values of 9.4, 18.9, and 18.1 at 42, 56, and 63 days after insemination, respectively. CONCLUSIONS: This study provides evidence that the intrauterine infection via contaminated semen using 5 x 10(4) and 5 x 10(5) tachyzoites caused persistent serum-specific antibody responses in some heifers. On the basis of serological data, a dose-response effect was also observed. In addition, N. caninum would be a probable cause of early foetal death in inoculated heifers. In contrast, results obtained in a similar experiment with cows showing confirmed infertility indicate that higher doses, such as of 5 x 10(5) tachyzoites, were necessary to induce seroconversion in at least one animal.     

Effect of repeated injections of GnRH on reproductive parameters in postpartum anestrous dairy cows

To induce cyclicity in dairy cattle with prolonged postpartum anestrous, repeated dosages of gonadotrophin releasing hormone (GnRH) were administered. Twenty-one (21) Holstein dairy cows and heifers calving between October 1, 1989, and January 1, 1990, at the Louisiana State University Dairy were used in the study. The animals were defined as anestrous if their plasma progesterone remained < 1.0 ng/ml until 32 to 36 days post partum. They were randomly assigned to one of two treatment groups. Group 1 (n=6) received two injections 1 hour apart of a GnRH analogue (50 mug) (i.m.). The treatment was repeated twice weekly at 3- to 4-day intervals. Group 2 controls (n=6) received saline (1 ml, i.m.) on the same schedule as Group 1. A maximum of 12 to 13 treatments were given. Cattle that had plasma progesterone >1.0 ng/ml by 32 to 36 days post partum were identified as Group 3, or cyclic contemporaries (n=9). Postpartum anestrous in the herd was 46.2% (18 39 ). Cows in Group 1 had significantly fewer days to first plasma progesterone > 1.0 ng/ml than those in Group 2 (P < 0.05), but more days than Group 3. Cows in Group 1 also had significantly fewer treatments to induce plasma progesterone > 1.0 ng/ml than those in Group 2 (P < 0.05). There were no significant differences among treatment groups in the number of days from calving to first observed estrus or the number of days open (P > 0.05).     

Peripheral plasma concentrations of oestradiol, progesterone, cortisol, LH and prolactin during the oestrous cycle in the cow, with emphasis on the peri-oestrous period

Interrelationships of circulating hormone levels and their implications for follicular development were studied throughout the oestrous cycle with emphasis on the perioestrous period in heifers and cows. The oestradiol level showed a major peak (45 pmol/1) before and coinciding with oestrus, and a second peak (27 pmol/1) around day 5–6 (day 0: day of first standing oestrus); it was low during the luteal phase of the cycle when progesterone was higher than 14 nmol/1 from day −12 to day −2. Large antral follicles, which had developed during the luteal phase, did not secrete significant amounts of oestradiol, degenerated after luteolysis, and were replaced by a newly developing follicle which became preovulatory. Parallel with this development the oestradiol level increased from the onset of luteolysis to reach a plateau about 26 h before the onset of oestrus. The interval between the onset of luteolysis and the onset of oestrus was 58 h; luteolysis proceeded at a slower rate in heifers than in cows. At 4.6 h after the onset of oestrus the maximum of the LH surge was recorded; the LH surge appeared to be postponed in the period October–December in comparison to the period August–September. The maximum of the LH surge was higher in heifers (45 μg/l) than in cows (30 μg/l), but its duration was similar (8.0 h). The oestradiol level decreased significantly from 6 h after the maximum of the LH surge, and standing oestrus (duration 18 h) was terminated almost at the same time as the return to basal values of oestradiol. Cortisol and prolactin levels did not show a peak during the peri-oestrus period. Cortisol fluctuated irrespective of the stage of the oestrus cycle and prolactin was significantly higher during the luteal phase.

The results of this study indicate that development of the preovulatory follicle starts in the cow at the onset of luteolysis, about 2.5 days before the preovulatory LH surge, and that oestradiol secretion by this follicle is possibly inhibited by the LH surge.     

Behaviour of Merinos divergently selected for multiple rearing ability in response to external stimuli

Data of Merino sheep descended from two divergent selection lines for (H line) and against (L line) multiple rearing ability were collected in three different trials to compare response to stressful situations between lines. Trial 1: the behaviour of 138, 20-month-old sheep born in 2001 and 124, 8-month-old sheep born in 2002 were observed in an arena test. Experimental animals amounted to 111 and 101 for the H line in the respective years. Corresponding numbers for the L line were 27 and 23, respectively. Progeny born in 2001 were accustomed to handling, as the tests were performed shortly after routine performance recording. Lambs born in 2002 were unaccustomed to handling when tested. Progeny from the H line born in 2002 allowed a smaller (P < 0.01) minimum distance between them and the human operator seated between them and a group of similar aged sheep than L line contemporaries. Progeny born in the L line during 2002 defecated more (P < 0.05) frequently than H line contemporaries. No line differences were found in progeny born during 2001. Trials 2 and 3 were designed to test whether the putative line difference in stress response would impact on physical meat quality. Trial 2: a total of 103, 18–20-month-old progeny from the two selection lines were slaughtered during 2001, 2002–2003. Mean slaughter weight, dressing percentage and carcass weight of H line animals were between 5 and 13% higher (P < 0.05) than that of L line animals. There were no differences in cooking loss, drip loss and tenderness between the two lines. As pertaining to the meat colour, L line progeny had less vivid red meat, as seen by their lower (P < 0.05) a* colour reading and chroma values. The L line animals had lower (P < 0.01) initial pH values as measured in the Musculus longissimus dorsi. These results are indicative of susceptibility to acute, short-term stress. Trial 3: 20 progeny of the two selection lines were slaughtered and their muscle pH measured at 11 intervals from 45 min to 48 h post slaughter. As in Trial 1, the initial pH of the L line animals were lower (P < 0.05) than that of H line animals. An opposite tendency was observed by 48 h post slaughter. The obtained results support a hypothesis that divergent selection for ewe multiple ability resulted in adaptations to cope with unfamiliar conditions.