Effects of exogenous ovine growth hormone on reproduction, serum hormone profiles and milk characteristics in early-postpartum fine-wool ewes nursing single or twin offspring

After parturition (Day 0), 31 mature spring-lambing, fine-wool ewes were randomly allotted to one of six groups. Treatments were lambs suckled (one or two) and ovine growth hormone (oGH; 0, 5 or 10 mg). Growth hormone was administered subcutaneously daily from Days 6 to 25. Milk characteristics were determined on Day 26. Ewes were observed for estrus beginning on Day 27. Serum insulin did not differ (P > 0.10) between suckling intensity before or after oGH treatment on Days 6, 15 or 25. Likewise, no difference (P > 0.10) in serum insulin was detected among ewes receiving 0, 5 or 10 mg oGH. Ewes suckling twins had higher (P < 0.05) serum growth hormone on Day 6 (before beginning oGH treatment) than ewes suckling single lambs. In ewes receiving 0, 5 and 10 mg oGH, serum growth hormone differed (P < 0.01) in a linear fashion 1 h after treatment was initiated on Day 6 and continued through Hour 6. Serum growth hormone on Days 15 and 25 differed among groups both before and after oGH was administered (P < 0.01). Suckling intensity did not affect (P > 0.10) milk or milk protein and fat yields; however, oGH increased (linear, P < 0.05) fat but did not affect milk or protein yields. Interval from parturition to estrus did not differ (P > 0.20) in ewes suckling single or twin offspring. Likewise, no differences (P > 0.20) in interval length were noted in ewes receiving 0, 5 or 10 mg oGH. Suckling intensity and oGH administration for 20 d had little effect on postpartum interval or milk characteristics during the first 30 d after lambing in fine-wool ewes.     

Growth, endocrine profiles and reproductive responses of ewe lambs after medium and long-term treatment with ovine growth hormone

Two experiments were conducted to examine effects of exogenous ovine growth hormone (oGH) on growth and reproductive traits of ewe lambs. In the first trial, 30 Debouillet ewe lambs (4 months old) received either 0 or 2.5 mg, s.c. of oGH (Day 0 = first day of 98-day treatment). Ovarian cyclicity was determined by monitoring serum progesterone. Efficiency of gain (first 50 days of treatment) was more (P < 0.10) desirable in oGH-treated animals, but did not differ (P > 0.20) between groups during the last 48 days of treatment. Serum GH in alternate-day samples was elevated five-fold (P < 0.01). First estrus occurred 10 days earlier (P = 0.14) in oGH-treated ewe lambs. In a second trial, 45 ewe lambs were evenly divided into three groups receiving 0 mg of oGH (CON; 50 injections), 2.5 mg of oGH (GH98, 50 injections) or 25 injections containing 2.5 mg of oGH followed by 25 injections of 0 mg of oGH (GH48) on alternate days for 98 days before a breeding season. Ewe lambs receiving GH48 had higher (P < 0.05) gains the first 24 days than those receiving CON or GH98. Ewes receiving GH48 demonstrated first estrus (P = 0.06) 22 days before control ewes and 28 days before GH98 ewes. Other reproductive traits did not differ (P > 0.25). Serum GH was greatly elevated by injections of exogenous oGH, but neither serum insulin nor prolactin was affected. Short-term elevation of serum GH resulting from exogenous oGH injections marginally enhances reproductive and growth responses, but does not induce major changes in these traits in ewe lambs after 4 months of treatment.     

Growth response, endocrine profiles and reproductive performance of fine-wool ewe lambs treated with ovine prolactin before breeding

Twenty-four 6-mo-old ewe lambs received one of two ovine prolactin (oPRL) treatments 28 d before fall breeding. Beginning on the first day of treatment (Day 0), 12 lambs received a subcutaneous injection (12 ml) of a carrier vehicle (0 mg oPRL) on alternate days for 28 d while 12 lambs received injections containing 5 mg oPRL. On Days 0 and 28, jugular blood was collected from six lambs in each group before treatment and at 30-min intervals for 6 h thereafter. Neither feed intake, efficiency of gain nor animal weights differed (P > 0.20) between groups. One hour after treatment on Day 0, ewe lambs receiving 5 mg oPRL had greater (P < 0.10) serum PRL levels than did controls (121.9 and 61.5 +/- 24.7 ng/ml, respectively). Differences in serum PRL persisted throughout remaining sampling intervals on both Days 0 and 28. Serum samples obtained on alternate days during the 28-d treatment period revealed no differences (P > 0.20) in PRL concentrations between control (48.3 +/- 5.3 ng/ml) and oPRL-treated (55.7 +/- 5.3 ng/ml) ewes. Neither serum insulin nor growth hormone responded (P > 0.05) to exogenous oPRL on either Day 0 or 28. No difference (P > 0.30) in percentage of ewe lambs cycling during treatment or breeding was detected between groups. Subsequent lambing percentages were similar (P > 0.30), with 36.4% of control and 25.0% of oPRL-treated ewes producing offspring. Administering 5 mg oPRL on alternate days for 28 d before breeding did not enhance growth and(or) reproductive performance in virgin ewe lambs.     

Growth response, reproductive activity, and serum growth hormone in fine-wool ewe lambs treated with triiodothyronine

Forty-four 6-mo-old, fine-wool ewe lambs were randomly allotted to one of three triiodothyronine (T(3)) treatment groups (14 or 15 ewe lambs/group). Treatments (0, 200, and 400 mug T(3)) were administered daily by subcutaneous injection during a 30-d treatment period in September. Following the treatments, ewe lambs were allowed to mate with Debouillet rams during a 34-d breeding season. Animal weights did not differ (P > 0.10) among treatment groups throughout the study. However, ewe lambs receiving 400 mug T(3)/d gained less (P < 0.05) during the treatment period than did those receiving 200 mug T(3)/d or controls. Grease fleece weights (6-mo clip) were similar (P > 0.10) among treatment groups. Serum growth hormone (GH) values in blood samples collected on Days 7 and 28 of the 30-d treatment were similar (P > 0.10) before treatments were administered and on Day 7 after treatments were administered. However, on Day 28 after treatments were administered, serum GH was lower (P < 0.01) in ewe lambs receiving 400 mug T(3)/d (1.5 ng/ml) than in those receiving 200 mug/d (2.1 ng/ml) or controls (2.2 ng/ml). Ovarian cyclicity was determined by monitoring serum progesterone. Forty percent of control ewe lambs were determined to have cycled during treatment compared with 20% of those receiving 200 mug T(3)/day and none of those receiving 400 mug T(3)/d (P < 0.10). Pregnancy rates were lower (P < 0.10) in ewe lambs receiving 400 mug T(3)/d (29%) compared with those receiving 200 mug T(3)/d (60%) or controls (66.7%). Day of conception, lambs born/ewe exposed, lambs born/ewe lambing, and lambs weaned/ewe lambing did not differ (P > 0.10) among treatments. Preweaning performance of offspring was not altered by maternal treatment with 200 or 400 mug T(3)/d (P > 0.10). These data indicate that 200 and 400 mug T(3)/d will not enhance GH production or improve reproductive performance of ewe lambs.     

Serum hormone profiles and return to estrus in early-postpartum spring-lambing ewes treated with somatostatin

After parturition, 10 mature spring-lambing fine-wool ewes producing twins were allotted to one of two treatments. Five ewes received sterile saline (i.v.) twice daily on Days 12 to 15 post partum (PP) while 5 ewes were treated similarly except each injection contained 500 mug somatostatin (SRIF). Jugular blood samples were collected at 15-min intervals for 1 h before to 3 h after morning treatment on Days 12 and 15 PP. Animals were observed twice daily for signs of estrus using vasectomized rams beginning on Day 31 PP and continuing until ewes returned to estrus. Interval from parturition to estrus (mean +/- SEM) was similar (P > 0.40) in ewes receiving SRIF (119 +/- 6.2 d) and in control ewes (113 +/- 6.2 d). Ewes receiving 500 mug SRIF had lower (P < 0.10) serum insulin during the first 45 min after treatment on Day 12 PP; however, on Day 15 PP, serum insulin did not differ (P > 0.40) between treatment groups. Serum growth hormone (GH) did not differ (P > 0.40) between treatment groups 1 h before treatment on Day 12 PP; however, ewes treated with SRIF had lower (P < 0.05) GH levels before treatment on Day 15 PP than control ewes (4.4 and 9.9 +/- 1.5 ng/ml, respectively). After administration of SRIF, serum GH was higher (P < 0.05) in SRIF-treated ewes than in controls (8.2 and 5.3 +/- 2.7 ng/ml, respectively) on Day 12 PP but no differences (P > 0.80) were noted between treatment groups on Day 15 PP. These data indicate that 500 mug SRIF given twice daily from Days 12 to 15 PP neither lowered serum GH nor influenced return to estrus in lactating fine-wool ewes.     

Serum thyroid hormones and reproductive characteristics of Rambouillet ewe lambs treated with propylthiouracil before puberty

Twenty-four Rambouillet ewe lambs (average weight=43.7+/-1.2 kg, approximately 6 months of age) were used to examine the effect of thyroid suppression before the onset of puberty on serum thyroid hormones, body weights (BW), and reproductive performance. Beginning in early September, ewe lambs were randomly assigned to three treatments (n=8 lambs/treatment). All animals remained in a single pen (4 x 12 m) with access to salt, water, shade and alfalfa hay (2.5 kg per animal per day) throughout the experiment. Beginning on Day 0 (first day of treatment), all ewe lambs received daily treatments (gavage) for 15 days consisting of 0, 20, or 40 mg 6-N-propyl-2-thiouracil(PTU)/kg BW per day. Beginning on Day 15, the 20 and 40 mg treatments were lowered to 10 and 20 mg PTU/kg BW, respectively. All animals were treated for 28 days. Ovarian cyclicity was determined by twice weekly progesterone (P(4)) analysis. Thyroxine (T(4)) concentrations were similar on Day 0 (61.6, 54.8 and 56.9+/-2.5 ng/ml, P=0.17) in ewe lambs receiving 0, 20 and 40 mg PTU/kg BW, respectively. By Day 7, both PTU-treated groups had T(4) values less than 20 ng/ml (9.0 and 15.4+/-2.5 ng/ml) compared with 78.5 ng/ml in controls (P<0.01). By 7 days after termination of PTU treatment, serum T(4) had risen to 29.1 and 26.9 (+/-2.9)ng/ml in the 20/10 and 40/20 PTU groups, respectively. On Day 66, control ewes had 55.0 ng T(4)/ml compared with 43.1 and 39.0 (+/-2.6 ng/ml) for ewes in the 20/10 and 40/20 groups, respectively (linear, P<0.01). Serum triiodothyronine (T(3)) followed a similar pattern to that observed for T(4). Ewe lamb BW were similar (P>0.50) among groups throughout the treatment period. However, following the treatment, PTU-treated ewes tended (P<0.10) to weigh less than controls. Average Julian day of puberty was also similar (P>0.50) among treatments (286, 288 and 288+/-5 days; control, 20/10 and 40/20, respectively). Control ewes had a pregnancy rate of 75%, while both PTU-treated groups had pregnancy rates of 88% (P>0.20). The administration of PTU resulted in a rapid decline in serum T(4) and T(3) but neither time of puberty nor pregnancy rates were affected by lowered thyroid hormones.     

Effects of long-term consumption of sewage solids on reproductive performance and serum progesterone and estradiol-17beta in mature fine-wool ewes

Eighty-four mature fine-wool ewes were randomly allotted to one of three dietary treatments to examine the influence of dietary sewage solids on reproductive performance. Treatments were a basal diet or basal plus either 3.5% cottonseed meal (CSM) or 7% sewage solids. Serum progesterone and estradiol-17beta measured in blood samples collected through an estrous cycle just before the breeding season of the first and second years were not adversely influenced by sewage feeding. Progesterone concentrations quantified in weekly blood samples collected during gestation and lactation of both years did not differ (P>0.10) among treatments. During the first lambing season, lambing data showed that ewes consuming CSM produced slightly more lambs per ewe exposed (P<0.10) than either basal- or sewage-fed ewes. During the second breeding season, midventral laparotomies revealed that ovaries from ewes receiving CSM contained more (P<0.10) corpora lutea than did those from either basal- or sewage-fed animals. However, at the end of the second lambing season, no differences (P>0.10) among treatments in the number of lambs born or weaned were observed. A third year's lambing data also revealed no difference (P>0.10) among treatments for lambing rates. These data indicate that prolonged consumption of a diet containing 7% sewage solids has little, if any, detrimental effect on reproductive performance of mature fine-wool ewes.     

Influence of suckling status and type of birth on serum hormone profiles and return to estrus in early-postpartum spring-lambing ewes

Twenty-three mature, spring-lambing, fine-wool ewes of Debouillet × Rambouillet breeding were allotted at parturition to one of four treatments which were arranged in a 2 × 2 factorial design with groups representing number of lambs born (i.e., one or two) and suckling intensity (i.e., lambs were weaned at 2 d of age or lambs remained with dams). Beginning at 0900 h on Day 2, 9, 16, 23, and 30 post partum (PP), jugular blood samples were collected from each dam at hourly intervals for the ensuing 6 h. Additional jugular blood samples were collected daily (Days 2 through 30). Animals were observed twice daily for signs of estrus using vasectomized rams. Interval from parturition to estrus (mean ± SEM) was similar (P > 0.15) in ewes nursing their offspring (117 ± 6 d) and those that had their lambs removed (124 ± 6 d). Dams producing single lambs returned to estrus in 126 ± 5 d compared with 116 ± 5 d (P > 0.15) for ewes producing twins. Serum luteinizing hormone and progesterone were low (< 1.7 and 0.5 ng/ml, respectively) in all ewes during the first 30 d PP. Serum insulin did not differ (P > 0.10) between suckled dams and those that had their lambs removed, but ewes giving birth to single offspring had higher (P < 0.05) insulin levels on Days 16 and 30 PP (543 ± 73 and 578 ± 57 pg/ml, respectively) than did dams producing twin lambs (324 ± 73 and 361 ± 57 pg/ml, respectively). Serum growth hormone (GH) did not differ (P > 0.40) between suckling intensity groups on Day 2 PP; however, by Days 16, 23, and 30, ewes in the suckled group had more (P < 0.05) GH than did those producing single offspring (5.4 and 3.6 ± 0.4 ng/ml, respectively). Early removal of lambs in spring-lambing ewes did not shorten the interval from parturition to estrus.     

Effect of post-mating GnRH analogue (buserelin) treatment on PGF2alpha release in ewes and ewe lambs

The objectives of this study were to determine the effects of buserelin or saline treatment on ovarian function (Experiment 1), plasma PGFM concentrations and oxytocin stimulated prostaglandin F(2alpha) (PGF(2alpha)) release (Experiment 2) in ewe lambs and ewes. Welsh Halfbred ewes (n=26) and ewe lambs (n=24) were mated to vasectomised rams at synchronised oestrus and on Day 12 post-mating each animal was injected intramuscularly either normal saline or 4 microg buserelin. In Experiment 1, plasma progesterone and oestradiol concentrations were determined in samples collected by jugular venepuncture 1h before and at 0, 2, 4, 6, 8, 24, 48 and 72 h after treatment (n=7 per treatment group). Progesterone concentrations increased (P<0.05) from 2 to 8h after buserelin treatment and returned to basal levels after 72 h, whereas oestradiol concentrations were maximal at 2h post-treatment and returned to basal levels after 24h (P<0.05). Oestradiol concentrations were lower (P<0.05) in buserelin-treated animals than controls at 72 h post-treatment. Basal and post-treatment progesterone concentrations were greater (P<0.05) in ewes than in ewe lambs but oestradiol levels were similar for both age groups. Ovulation rate, determined by laparoscopy on Day 14, was similar for both age groups (ewes 1.1; ewe lambs 1.0). Buserelin treatment induced accessory corpora lutea in ewes (4/7; 57%) but not in ewe lambs (0/7; 0%). In the Experiment 2, plasma PGFM concentrations were determined in samples collected at 20-min intervals for 6h on Day 14 and at 20-min intervals for 1h before and at 10-min intervals for 1h and then at 20-min intervals for a further 3h period after an intravenous injection of oxytocin (1IU/kg body weight) on Day 15 post-oestrus. In this experiment there were five ewe lambs and six ewes per treatment group. There was no effect of buserelin treatment or age on basal PGFM concentrations on either Day 14 or 15. Although peak PGFM concentrations tended to be lower in buserelin-treated animals, the difference was not significant (P>0.05). However, peak duration following oxytocin challenge on Day 15 post-mating was shorter (P<0.05) in control ewes compared with control ewe lambs. In conclusion, buserelin treatment given on Day 12 post-oestrus enhances luteal function more in ewes than ewe lambs and after a transitory increase, reduces oestradiol concentrations in both ewes and ewe lambs. However, buserelin treatment does not significantly attenuate the luteolytic signal.     

The effects of GnRH analogue (buserelin) or hCG (Chorulon) on Day 12 of pregnancy on ovarian function, plasma hormone concentrations, conceptus growth and placentation in ewes and ewe lambs

The objectives of this study were to determine the effect of GnRH analogue (buserelin) or human chorionic gonadotrophin (hCG, Chorulon) treatment on Day 12 of pregnancy on ovarian function, plasma hormone concentrations, conceptus growth and placentation in ewes and ewe lambs. After oestrus synchronization with progestagen sponges and eCG, all the animals were mated with fertile rams. Both ewes and ewe lambs (20 per treatment group) were given either normal saline or 4 microg GnRH or 200 IU hCG on Day 12 post-mating. Pre- and post-treatment plasma hormone concentrations were determined in seven pregnant animals per treatment group in samples collected 1h before and 0, 2, 4, 6, 8, 24, 48 and 72 h after treatment. Overall mean progesterone concentrations were higher (P<0.001) in ewes as compared with ewe lambs in saline-treated controls. GnRH or hCG treatment increased (P<0.001) mean plasma progesterone concentrations in both age groups, however, post-treatment concentrations were significantly (P<0.05) higher in ewes than in ewe lambs. Oestradiol concentrations were similar in the two control groups. In ewes, but not in ewe lambs, both GnRH and hCG treatments significantly (P<0.05) increased the mean oestradiol concentrations above pre-treatment levels. Moreover, post-treatment oestradiol concentrations in GnRH- and hCG-treated animals were significantly (P<0.05) higher than those in the saline-treated controls. LH release in response to GnRH treatment was greater (P<0.05) in ewes than in ewe lambs, whereas FSH release in ewes was less (P<0.05) than that of ewe lambs. The effects of GnRH or hCG on conceptus growth and placentation was determined at slaughter on Day 25. In ewes, GnRH treatment increased (P<0.05) luteal weight, amniotic sac width and length, and crown-rump length compared with controls, but had no effect on these parameters in ewe lambs. In ewes, hCG treatment also enhanced (P<0.05) luteal weight, amniotic sac width and length, crown-rump length, embryo weight and number of placentomes as compared with controls. In ewe lambs, there was no difference (P<0.05) between hCG and control groups in luteal weight, embryo weight and amniotic sac width but crown-rump length, amniotic sac length and the number of placentomes forming the placenta were greater (P<0.05). In conclusion, GnRH or hCG treatment on Day 12 of pregnancy can increase ovarian function, conceptus growth and placental attachment in ewes. However, these treatments were less effective in ewe lambs.     

Effect of insulin on feed intake and reproductive performance of well-nourished nulliparous ewes

Eighty-four nulliparous ewes were used to examine the effect of short-term insulin treatment on feed intake and reproductive performance. Following estrus synchronization, ewes were observed for estrus (= Day 0) and were penned individually beginning on Day 7. Ewes were fed twice daily and feed intake was recorded. On Days 9 through 13, ewes were treated s.c. with 1 IU/kg BW insulin (n = 44) or an equivalent volume of saline (n = 40). On Day 14, ewes were placed with fertile rams and number of ewes in estrus (bred) was recorded. Thirty days post-breeding, ewes were checked for pregnancy via ultrasonography. Feed intake and percentage of ewes in estrus did not differ between saline- and insulin-treated ewes. Similarly, neither pregnancy rate (69 +/- 8.7% vs. 80 +/- 8.1%, respectively) nor lambing rate (61 +/- 8.9% vs. 78 +/- 8.4%, respectively) differed between treatments. The number of lambs born per ewe was, however influenced by a breed-group effect (P < 0.0002). Romanov ewes had more (P < 0.001) lambs than the other breed groups in the study. Therefore, treating well-nourished, nulliparous ewe lambs with insulin did not increase reproductive efficiency, possibly because the ewes were already at a maximal nutritional and/or reproductive state.     

Semen characteristics, mating performance and serum testosterone in rams fed sewage solids

Two months before beginning an autumn breeding season, ten 18-month-old Debouillet rams were randomly allotted to one of two dietary treatments. Five rams were offered a complete pelleted diet containing 3.5% cottonseed meal (CSM) and five were fed a similar diet containing 7% undigested, irradiated (1 Mrad gamma-irradiation) sewage solids (SS, Las Cruces, NM, municipal sewage) during the ensuing nine-month period. Ram body weights did not differ (P>0.10) between treatments nor was grease fleece weight (six-month clip) influenced by dietary SS. Analysis of serum constituents did not reveal any treatment effects. Neither quantity nor quality of sperm was influenced by treatment. Rams were mated to both CMS- and SS-fed ewes and dietary SS did not adversely influence (P>0.25) ram or ewe reproductive performance. Paternal sewage consumption did not alter (P>0.10) preweaning performance of lambs; however, ewes consuming SS produced lambs that weighed less (P<0.05) at weaning. Neither paternal nor maternal treatments influenced (P>0.10) lamb weights or gains during an 84-day postweaning feedlot trial. When each ram was challenged with 50 mug gonadotropin releasing hormone, both groups responded with a similar testosterone surge. These data suggest that a diet containing 7% SS does not impair reproductive function, testosterone production, offspring performance or health of fine-wool rams.     

Behavioral and endocrine responses of hair sheep ewes exposed to different mating stimuli around estrus

Hair sheep ewes were used to evaluate the influence of various levels of mating stimuli on the duration and timing of estrus and LH concentrations around estrus. Ewes were treated with PGF2alpha (15 mg, im) 10 d apart. At the time of the second PGF2alpha treatment (Day 0) ewes were placed in groups and exposed to different types of mating stimuli. One group of ewes (n = 16) was exposed to an epididymectomized ram (RAM), a second group of ewes (n = 16) was exposed to an epididymectomized ram wearing an apron to prevent intromission (APRON) and a third group of ewes (n = 17) was exposed to an androgenized ovariectomized ewe (T-EWE). Jugular blood samples were collected from ewes at 6-h intervals through Day 5. Plasma was harvested and LH concentration was determined by RIA. The ewes were observed at 6-h intervals to detect estrus. A ewe was considered to be out of estrus when she no longer stood to be mounted by the teaser animal. There was no difference (P > 0.10) in the proportion of ewes expressing estrus (79.6%) or having an LH surge (85.7%) among the treatments. Neither the time to estrus nor the duration of estrus were different (P > 0.10) among APRON, RAM or T-EWE groups (41.6+/-3.8 vs 43.6+/-3.6 vs 46.1+/-3.6 h, respectively, and 26.5+/-2.2 vs 24.8+/-2.3 vs 30.5+/-2.2 h, respectively). The time to LH surge was similar (P > 0.10) among APRON, RAM and T-EWE groups (51.2+/-4.5 vs 51.2+/-4.7 vs 52.7+/-4.5 h, respectively). The magnitude of the LH surge was similar (P > 0.10) in the T-EWE, APRON and RAM ewes (99.7+/-4.9 vs 87.2+/-4.9 vs 85.8+/-5.0 ng/mL, respectively). The time from estrus to the LH surge was not different (P > 0.10) among APRON, RAM or T-EWE ewes (10.1+/-2.2 vs 9.8+/-2.3 vs 11.6+/-2.3 h, respectively). These results show that the expression and duration of estrus are not influenced by different types of mating stimuli in hair sheep ewes. In addition, the timing and the magnitude of LH release does not appear to be influenced by mating stimuli around the time of estrus.     

Effects of age on fasting-induced changes in insulin, glucose, urea nitrogen, and free fatty acids in sera of sheep

The hypothesis that prepubertal ewe lambs are metabolically different from postpubertal ewes was tested. Ovariectomized ewes (4 years of age; n = 4) and lambs (6 months of age; n = 4) were fasted for 72 hr. Serum concentrations of insulin, glucose, urea nitrogen, and free fatty acids (FFA) were measured in blood samples taken at 6-hr intervals between 30 hr before and 72 hr after feed removal. Serum concentrations of urea nitrogen and glucose were not different (P greater than 0.20) between age groups before fasting. Serum concentrations of insulin in ewes increased toward the end of the prefast period whereas those in lambs did not (age x time, P less than 0.01). Serum concentrations of FFA in ewes tended to be lower (P less than 0.07) than those in lambs prior to fasting. During fasting, concentrations of insulin decreased (P less than 0.02) over time in ewes and lambs and did so in a similar manner (age x time, P greater than 0.70). Urea nitrogen increased (P less than 0.0001) in both fasted ewes and fasted lambs in a comparable manner (age x time, P greater than 0.20). Concentrations of glucose during fasting were not significantly affected (P greater than 0.90) by age. There was a tendency (P = 0.08) for concentrations of glucose to change over time but the pattern did not appear to be related to fasting. During fasting, concentrations of FFA tended to be higher (P less than 0.07) in lambs than in ewes and increased (P less than 0.0001) in both groups in a similar fashion (age x time, P greater than 0.10). The findings herein suggest that turnover of FFA in lambs may be slightly greater than that in ewes during the fed and fasted states.     

Serum luteinizing hormone, growth hormone and insulin-like growth factor-I after releasing hormone challenge in prepubertal ewe lambs selected for twinning

Two studies evaluated hormonal markers as indicators of the onset of puberty in Debouillet sheep selected for twinning. In Trial 1, 29 ewe lambs (50 +/- 0.5 kg, 159 to 187 d of age) were given 10 microg GnRH (i.v.) on September 15 and blood was collected at 30 min intervals after the injection for 2 h. Additional samples were taken twice weekly and progesterone (P4) was measured. The day that serum P4 was greater than 1 ng/mL for 2 consecutive sampling days was classified as the day of puberty. Average day of puberty was October 12 (average age at puberty was 199 d) and ewes with values less or greater than the average were classified as early or late, respectively. Average weight at GnRH challenge was 50 kg and ewes weighing less or more were classified as light or heavy, respectively. Early ewes weighed more (P = 0.01) and reached puberty sooner (P = 0.01) than late ewes. Heavy lambs reached puberty earlier, weighed more at GnRH challenge, and had more LH area under the curve (AUC, P < 0.05) than light ewes. In Trial 2, we gave 27 ewe lambs (54 +/- 0.9 kg, 173 to 189 d of age) a single i.v. injection of 10 microg GnRH and 10 microg GHRH on September 17. Average day of puberty was October 13, average weight was 54 kg, and average age at puberty was 208 d. Categories were designated as described for Trial 1. Early lambs reached puberty sooner (P = 0.01) and weighed more (P = 0.01) than late lambs, but the puberty groups had similar LH AUC (P = 0.64) and GH AUC (P = 0.75), whereas IGF-I was greater (P = 0.01) in early puberty ewes than in late puberty ewes. Heavy lambs reached puberty earlier (P = 0.06), weighed more (P = 0.01), and tended (P = 0.11) to have more GH AUC than light ewes. No difference was observed in LH AUC or IGF-I between weight groups (P > 0.15). Results suggest that serum LH after GnRH is not a reliable indicator of the onset of puberty in ewe lambs selected for twinning, but heavier ewes tended to produce more GH after a GHRH challenge and reach puberty earlier than lighter ewe lambs.     

Effects of dietary sewage solids on second-generation ewes fed an experimental diet from weaning through two reproductive cycles

Eighteen fine-wool ewe lambs produced by mature, conventionally fed dams and 21 similar offspring from sewage-fed ewes were randomly allotted at weaning to one of two groups. Half of the lambs from each maternal diet group received a conventional (18% protein) diet during the growing phase while the remainder was fed the conventional diet plus 7% undigested, irradiated sewage solids (18% protein). At the end of the 147-day growing period and just before a fall breeding season, conventionally fed ewe lambs were switched to a control diet (12% protein) suitable for mature ewes and sewage-fed ewe lambs began receiving the control diet plus 7% sewage solids. Animals received these diets for two years. Maternal sewage consumption did not influence performance of F₁ ewe lambs. By the beginning of the first breeding season, controls were heavier (P<0.01) than were animals receiving sewage solids (51.7 and 44.5 kg, respectively). Similarly, only 75% of sewage-fed ewe lambs exhibited estrus during their first breeding season compared with 94.7% of controls (P<0.10). Conception rate (40.0 and 84.2%, respectively) and lambs born per ewe exposed (0.4 and 0.89, respectively) were also lower (P<0.05) in animals receiving sewage solids than in controls. During the second reproductive cycle, conception rate as well as lambs born per ewe exposed was comparable (P>0.10) between the two groups. Offspring from the sewage-fed ewe lambs, however, weighed less (P<0.05) at weaning than did lambs produced by control animals. Results indicate that a diet containing 7% sewage solids may not be suitable for preparing ewe lambs to go into the breeding flock; once mature size is attained, however, reproductive performance is not hampered by sewage feeding.     

Effects of restricted feeding of prepubertal ewe lambs on reproduction and lactation performances over two breeding seasons

The aim of this study was to determine the effects of restricted feeding before puberty on reproduction, lactation and offspring growth performance in replacement ewe lambs over two breeding seasons. At weaning, 41 Dorset ewe lambs were assigned to one of three diets: an ad libitum control diet with medium-quality forage (MQF; 13.3% crude protein (CP), 1.81 Mcal metabolizable energy per kg, 42.8% ADF; diet A-MQF); a restricted diet with the same forage as A but less feed concentrate (diet R-MQF); or a high-quality forage (HQF) diet (14.8% CP, 2.15 Mcal ME/kg, 34.7% ADF; diet F-HQF). The quantity of concentrate offered to the group R-MQF and F-HQF ewe lambs was adjusted to obtain 70% of the control ewe lambs' growth rate. The diets were offered for 75 days following weaning to cover the allometric phase of mammary gland development. Prepubertal restriction did not affect (P > 0.10) the gestation rate, number of lambs born or the body weight and body condition score of ewes at lambing or at the end of lactation. Ewes from groups R-MQF and F-HQF tended to produce more milk during their first lactation compared to those from group A-MQF (P = 0.07). During the second lactation, groups R-MQF and F-HQF had better standardized milk production than group A-MQF (P < 0.05), and group R-MQF produced more milk than group F-HQF (P < 0.05). Milk fat and protein content were not affected by treatments (P > 0.10) Fat and protein yield were affected by treatments only at the second lactation (P < 0.10 and P < 0.05, respectively). Lamb birth and weaning weights were not affected by prepubertal restriction of feeding in their mother (P > 0.10). However, the average daily gain of second breeding season lambs was higher for the R-MQF group than the F-HQF group (P < 0.05), and a similar trend was observed for total gain (P < 0.10). Restricted feeding before puberty does not impair future reproductive performance; however, it has a positive impact on lactation and on lambs' growth performance.     

The effects of pasture availability for twin- and triplet-bearing ewes in mid and late pregnancy on ewe and lamb behaviour 12 to 24 h after birth

This experiment was conducted to evaluate the effect of offering ewes two different feeding levels, during mid and late pregnancy, on ewe and lamb behaviour 12 to 24 h after birth. Romney ewes, bearing twin (n = 80) or triplet foetuses (n = 56), were allocated to a pasture sward height of 2 or 4 cm between 70 and 107 days of pregnancy. In late pregnancy (day 107 to 147), half of the ewes were reallocated the alternate sward height, which produced four treatments: 2-2, 2-4, 4-2 and 4-4. Ewes were weighed on days 65, 92, 107 and 130 of pregnancy and lamb live weights were recorded 12 to 24 h after birth. Twelve to 24 h after birth the maternal behaviour score (MBS) of the ewes were determined, whilst their lambs were tagged. After the lambs were released, the behaviour of each ewe and her lambs was observed for 5 min. Ewe treatment and litter size had no effect on ewe MBS. However, as MBS increased (ewes stayed closer to lambs during tagging), ewes bleated less in a high-pitch and were quicker to make contact with their lamb. During the observation period, ewes in the 4-4 treatment had a greater percentage of their bleats in a low pitch (P < 0.05) than ewes in the 2-2 and 4-2 treatment (61.3% v. 41.3% and 38.8% low bleats, respectively) and more lambs born to 4-4 ewes (95%) bleated than lambs born to 2-2 ewes (84%; P < 0.05). However, lambs born to ewes in the 2-2 treatment bleated earlier than lambs in all other treatments (P < 0.05). Lambs born to 4-4 ewes were less likely (P < 0.05) to move towards their dam in order to make contact than lambs born to 2-2 or 4-2 ewes (3.1% v. 16.9% and 16.7%, respectively). These findings suggest that under the conditions of the present study, ewe nutrition had little effect on maternal behaviour. However, lambs born to ewes offered 2 cm pasture sward heights during mid and/or late pregnancy (2-2, 2-4 and 4-2 treatments) displayed behaviour that demonstrated greater 'need' whereas lambs born to ewes offered 4 cm during mid and late pregnancy sought less attention from their dam.     

Exogenous growth hormone improves the number of transferable embryos in superovulated ewes.

The application of pGH (porcine Growth Hormone) to superovulated ewes was studied with the aim of improving the embryo yield. Thirty-seven ewes were superovulated with pFSH for 3 d and 18 of them were cotreated the third day with 0.50 mg of pGH. Embryos were surgically recovered on Day 7 after sponge withdrawal. Then, 102 morphologically healthy embryos were immediately transferred in pairs to 51 synchronized recipient ewes. The GH treatment did not significantly affect the percentage of ewes in estrus, the time of estrus onset or the ovulation rate. However, it improved synchronization by grouping estrus in a narrower range (12 h) in comparison to the control group (24 h); (16 to 28 h after sponge withdrawal vs 12 to 36 h; P < 0.05). The total amount of LH released during the preovulatory surge was lower in the GH than in the control group (P < 0.05). No differences were found between groups for other LH-related parameters such as basal levels, peak values or peak time from sponge removal. The proportions of unfertilized oocytes and degenerate embryos recovered were lower in the GH cotreated group (P < 0.05 and P < 0.01, respectively). This resulted in higher rates of transferable embryos and lambs born per donor ewe in the GH than in the untreated group (3.9 vs 1.7 and 2.28 vs 0.84, respectively; both, P < 0.05). These beneficial effects of GH would likely be due either to a direct action on oocyte maturation or to an indirect action on the oviductal environment.     

Progesterone administration reduces the behavioural and physiological responses of ewes to abrupt weaning of lambs

Abrupt weaning, a usual management in sheep productive systems, may provoke behavioural and physiological responses indicative of stress in ewes and lambs. Progesterone (P4) has anxiolytic and sedative effects through the union of its metabolites that contain 3α-hydroxyl group to the γ-aminobutyricacid_A receptor. Our first aim was to determine whether P4 administration reduces the behavioural and physiological responses of ewes to abrupt weaning of lambs. A complementary aim was to determine whether P4 treatment affects the milk yield and composition of ewes, and the BW of their lambs. In experiment 1, seven ewes received P4 treatment for 32 days (group E1-P4), and eight ewes remained as an untreated control group (group E1-C). BW of the lambs was recorded during P4 treatment. Lambs were weaned at 59 days (Day 0 = weaning). The main behaviours of the ewes before and after weaning were recorded using 10 min scan sampling. The ewes’ serum total protein, albumin and globulin concentrations were measured before and after weaning of the lambs. In experiment 2, milk yield and composition were determined in two different groups of six ewes treated with P4 (group E2-P4) for 16 days and in five untreated controls (group E2-C). The BW of lambs increased with time (P = 0.001) in both groups and did not differ. The percentage of observations in which the ewes were seen pacing on Day 0 was greater in the E1-C group than in the E1-P4 group (P = 0.0007). Similarly, the percentage of observations in which the ewes were recorded vocalizing on Day 0 was greater in the E1-C group than in the E1-P4 group (P = 0.04). The percentage of observations in which E1-C ewes were recorded lying did not change from Days 0 to 1; however, it increased in E1-P4 ewes. Total serum protein concentration did not change in E1-P4 ewes from Days 0 to 3, although a decrease was seen in E1-C ewes (P = 0.04). Serum globulin concentration was greater in E1-P4 ewes on Day 3 than in E1-C ewes (P = 0.0008). In experiment 2, there were no differences between E2-P4 and E2-C ewes in terms of milk yield, protein, fat and lactose content. Progesterone administration reduced the behavioural and physiological responses of ewes to abrupt weaning of lambs, and this effect was not mediated by changes in milk yield and composition, or by lambs’ BW.