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1.
The objectives of this study were to determine whether a new progesterone (P4)-releasing intravaginal insert would induce fertile estrus and whether FSH combined with the insert would increase prolificacy in anestrous ewes introduced to rams. Ewes of mixed breeding on six farms were assigned to four randomized treatments: control (C), n = 73; 12 d P4 (polycapralactone [PCL] insert with 0.82 g P4), (P12), n = 73; 12 d P4 plus i.m. FSH (Folltropin, 55 mg NIH-FSH-P1 equivalent) in propylene glycol, 24 h before insert removal, (P12F), n = 71; and 5 d P4 plus FSH (P5F), n = 77. Growth and ovulation of follicles were observed ultrasonographically in 20 ewes at four farms (five/treatment) at insert removal and 36, 48, 72, and 96 h later. Intact rams (1:15 ewes in multiple-sire groups) were joined at insert removal, and raddle marks were observed every 12 h for 5 d. On d 26 to 30, rams were removed; ewes were examined for pregnancy then and 20 d later. Percentage of ewes marked by rams was greater in P4-treated (66 to 79%) than in C (12%; P < 0.01) ewes and in P5F (79%) than in P12F (66%; P < 0.05). Diameters of largest follicles at insert removal were greater (P < 0.05) in P4-treated (5.5 +/- 0.2) than in C ewes (4.8 +/- 0.2). Progesterone increased numbers of follicles > 3 mm (P < 0.01) or ovulated (P < 0.05; 2.6 +/- 0.6 vs 1.3 +/- 0.6 in C ewes) and FSH increased number of follicles > 3 mm (P < 0.05). In FSH-treated ewes, ovulation rate tended to be greater after treatment with P4 for 5 than for 12 d (P = 0.09, 3.3 +/- 0.6 and 2.2 +/- 0.4, respectively). More P4-treated than C ewes lambed (P < 0.01) to the first (38 to 45 vs 0%) or both (63 to 66 vs 41%) service periods. Prolificacy (first service) did not differ between FSH-treated ewes (P12F + P5F; 1.8 +/- 0.1) and ewes treated with P4 only (P12; 1.6 +/- 0.1). However, FSH increased prolificacy to first service (1.8 +/- 0.1) over prolificacy to second service (C ewes 1.5 +/- 0.1; P < 0.05, and all ewes 1.4 +/- 0.1; P < 0.01). Pregnancy retention did not differ among treatments but was greater (P < 0.01) in ewes that conceived at the first (90.9 +/- 3.7) than at the second (72.5 +/- 3.3) service period. In conclusion, a PCL insert in combination with ram introduction at insert removal was more effective than ram introduction alone to induce synchronized estrus and ovulation and to yield pregnancy after one or two service periods. Treatment with P4 for 5 d was as effective as for 12 d to induce fertile estrus in FSH-treated anestrous ewes.  相似文献   

2.
Ninety-nine multiparous Brahman-influenced (1/4 to 3/8 Brahman) cows were managed to achieve low (BCS = 4.3 +/- 0.1; n = 50) or moderate (BCS = 6.1 +/- 0.1; n = 49) body condition (BC) to determine the influence of bovine somatotropin (bST) on estrous characteristics, reproductive performance, and concentrations of serum GH and plasma NEFA. Beginning 32 d postpartum, cows within each BC were assigned randomly to treatment with or without bST. Non-bST-treated cows received no treatment, and treated cows were administered bST (Posilac, 500 mg s.c.) on d -35, -21, and -7 before initiation of the breeding season. On d -7, all cows received an intravaginal, controlled internal drug-releasing (CIDR) device. On d 0 (initiation of the 70-d breeding season), the CIDR were removed and cows received prostaglandin F2alpha (PGF2alpha). Blood samples were collected from the median caudal vein of the cows at each bST treatment and at d -28 and 0. Estrous behavior was monitored by radiotelemetry during the first 30 d of the breeding season. Growth hormone was increased (P < 0.05) in low and moderate BC cows treated with bST. The percentage of cows detected in estrus during the first 30 d of the breeding season was decreased (P = 0.05) for low BC (64%) compared with moderate BC (82%) cows. The interval to first estrus tended (P = 0.07) to be shorter in low BC-bST-treated cows (3.7 +/- 1.9 d) than in moderate BC-bST-treated cows (9.6 +/- 1.8 d). During the first 30 d of the breeding season, cows in low BC had a decreased (P = 0.02) number of mounts received and increased (P = 0.001) quiescence between mounts compared with cows in moderate BC. The number of mounts received was reduced (P = 0.04) in bST-treated cows. More (P = 0.02) cows treated with bST became pregnant during the first 3 d of the breeding season compared with non-bST-treated cows. The cumulative first-service conception rate tended (P = 0.07) to be greater for bST-low BC cows than non-bST-treated cows in low or moderate BC. On d 0, NEFA were greater (P < 0.05) in bST-treated vs. non-bST-treated cows. Low BC and bST reduced the intensity of behavioral estrus in postpartum Brahman-influenced cows. However, bST increased the first-service conception rate during the first 30 d of breeding and pregnancy rates during the first 3 d of breeding in postpartum Brahman-influenced cows.  相似文献   

3.
Mature pregnant crossbred ewes (n = 90) were used in a randomized complete block design and assigned to 1 of 3 winter-feeding systems differing in primary feed source: haylage (HL), limit-fed corn (CN), or limit-fed dried distillers grains (DDGS). Effects of these winter-feeding strategies on ewe and lamb performance were determined. Diets were formulated to meet or exceed NRC (1985) nutrient requirements during gestation and were fed from about d 60 of gestation until parturition. All ewes were fed a common diet postpartum. Every 2 wk during gestation, BW and BCS were collected and diets were adjusted to maintain similar BW gain for ewes fed CN and DDGS vs. HL. At 80 and 122 d of gestation, jugular blood samples were collected at 0, 3, 6, and 9 h postfeeding to measure plasma glucose, insulin, NEFA, and blood urea nitrogen concentrations. At birth, 6 lambs per treatment were killed to measure body composition. At 28 ± 2 d postpartum, milk yield was measured. Lambs were weaned at 61 ± 4 d of age. During mid gestation (d 60 to 115), BW gain of ewes was similar among treatments; however, at d 115 of gestation ewes fed HL had a smaller (P = 0.04) BCS than ewes fed DDGS or CN. Plasma glucose concentrations were greater (P ≤ 0.004) in ewes fed CN than in those fed HL or DDGS just before feeding on d 80 and 122 of gestation, whereas ewes fed DDGS vs. CN or HL had greater (P ≤ 0.04) plasma insulin concentrations at 3 h postfeeding. At parturition, ewe BW was greatest for DDGS, least for HL, and intermediate for CN (P ≤ 0.003). Ewes fed CN and DDGS had greater BCS at parturition than those fed HL, but by weaning, ewes fed DDGS had greater BCS (P ≤ 0.05) than those fed CN or HL. Birth BW tended (P = 0.09) to be heavier for lambs from ewes fed CN and DDGS than from those fed HL prepartum, but there was no difference (P = 0.19) due to ewe gestation diet on lamb BW at weaning. At birth, lamb muscle, bone, organ, and fat measures were not affected (P > 0.13) by treatment. Ewe milk production and lamb preweaning ADG were also similar (P > 0.44) among treatments. Prepartum dam winter feed source did not have detrimental effects on pre- or postpartum ewe performance, but altered prepartum maternal nutrient supply during gestation, which affected birth weight but not preweaning growth or mortality.  相似文献   

4.
Objectives of this study were to determine whether feeding high-linoleic safflower seed to gestating ewes increases cold tolerance and survival in lambs, and whether brown adipose tissue (BAT) stores in lambs are affected by prepartum safflower seed supplementation. In Trial 1, 234 gestating ewes (122 in yr 1 and 112 in yr 2; 75.5 and 81.2 +/- 0.6 kg initial BW for yr 1 and 2, respectively) were allotted randomly to one of two dietary treatments (four pens*treatment(-1)*yr(-1)). Ewes were fed alfalfa-based diets containing (DM basis) either 2.8 (LF) or 5.7% (HF) dietary fat beginning 55 (yr 1) and 42 (yr 2) +/- 1 d prepartum. In Trial 2, 40 Rambouillet cross ewes gestating twins (82.9 +/- 1.7 kg BW) were used in 2 yr (20/yr) and were fed diets containing (DM basis) either 1.9 (LF) or 4.9% (HF) dietary fat beginning 53.4 +/- 1.4 d prepartum. The basal diet was 37.5% each of grass and alfalfa hays and 25% corn silage (DM basis). Cracked safflower seeds (18% CP, 32% fat, 25.6% linoleic acid; DM basis) were used as the supplement in HF, whereas safflower meal and corn were used as the supplement in LF for both trials. At parturition, one lamb from each ewe was selected randomly for slaughter. Perirenal (PR) and pericardial (PC) BAT was excised and weighed, and the carcass was frozen for compositional analysis. In Trial 1, more lambs from HF 0.03; 15.4 vs. 5.8 +/- 2.8%), and dams survived (P = 0.03; 88.4 vs. 78.3 +/- 2.9%), fewer died due to starvation (P = there was a tendency for fewer to die due to pneumonia (P = 0.07; 0.0 vs. 1.7 +/- 0.6%). Ewes fed HF tended to wean more lambs per ewe (P = 0.09; 1.4 vs. 1.2 +/- 0.06) but had similar lamb weight weaned per ewe (P = 0.51; 23.1 +/- 1.22 kg). In Trial 2, prepartum ewe plasma NEFA and glucose concentrations increased with advancing gestation (P < 0.001). Lamb rectal temperature tended (P = 0.08) to be higher in LF lambs and tended (P = 0.06) to increase following parturition. Perirenal BAT weight did not differ among treatments (33.01 +/- 1.66 g; P = 0.28; 0.62 +/- 0.30% BW; P = 0.60). Lambs from LF dams tended (P = 0.08) to have greater PC BAT weight; however, the effect was not significant when expressed as a percentage of BW (0.13 +/- 0.007; P = 0.98). High-linoleic safflower seeds fed during the last 45 d of gestation may be beneficial in improving lamb survivability. Our data do not indicate this response was a result of increased BAT stores. More research is necessary to determine mechanisms that enhance lamb survival when high-linoleic saf-flower seed is fed during gestation.  相似文献   

5.
The postpartum (PP) period in the Pelibuey ewe was studied. Laparotomies were performed on 14 ewes in the first year at d 10, 20 and 30 PP, and at d 10 and 20 PP in the second year on 17 ewes. Progesterone concentrations were determined in serum taken daily, from 4 to 7 d after parturition until estrus. Temporal fluctuation of luteinizing hormone (LH) was determined in samples taken at 30-min intervals for 4 h weekly. The mean interval from lambing to first ovulation was longer (P less than .001) in 1980 (59 +/- 4.9 d) than 1979 (26 +/- 3.1 d), the mean interval from lambing to first estrus was also longer (P less than .001) in 1980 (91 +/- 5.6 d) than 1979 (51 +/- 5.5 d). Follicles were present on the ovaries of the majority of the ewes at d 10. The mean diameter of the largest follicles on each ovary was reduced (P less than .025) in ewes in 1980 (6 mm) compared with 1979 (7.7 mm). Corpora lutea (CL) occurred in 67 and 75% of the ewes by d 20 and 30, respectively in 1979; no CL were found by d 20 in 1980. Progesterone profiles suggested that the PP period was composed of a period of anestrus, and a period of cyclic ovarian activity with one, two or three ovulations without behavioral estrus. In some ewes, the first cycle was of shorter duration, and its CL secreted less progesterone (P less than .05) relative to CL of silent and regular estrous cycles. Luteinizing hormone peaks were recorded as early as 6 d PP. When progesterone concentrations were elevated to luteal phase levels, the frequency, but not magnitude, of LH peaks per 4-h bleeding period was reduced (P less than .05) relative to anestrus. It is concluded that there are periods of anestrus and of silent cycles, which precede the first postpartum estrus in Pelibuey ewes.  相似文献   

6.
This study utilized maternal undernutrition from early to midgestation in the ewe to determine the impact(s) of intrauterine growth restriction on postpartum growth of male offspring and the potential mechanisms involved. Multiparous ewes were fed 50% (nutrient-restricted) or 100% (control-fed) of their nutrient requirements (NRC, 1985) between d 28 and 78 of gestation, and then all ewes were fed 100% of the NRC requirements from d 79 through lambing. Male lambs born to nutrient-restricted (n = 9) and control-fed (n = 9) ewes exhibited similar BW (5.8 vs. 6.0 +/- 0.3 kg) and crown-rump lengths (53.8 vs. 55.4 +/- 1.0 cm) at birth. At 63 and 250 d of postnatal age, wether lambs were subjected to a glucose tolerance test, in which a bolus of glucose was administered i.v. to evaluate changes in glucose and insulin concentrations. After i.v. glucose administration at 63 d of age, lambs from nutrient-restricted ewes exhibited a greater area under the curve for glucose (AUCg; 6,281 vs. 5,242 +/- 429; P < 0.05) and insulin (AUCi; 21.0 vs. 8.6 +/- 1.9; P < 0.001) than lambs from control-fed ewes. After glucose administration at 250 d of age, lambs from nutrient-restricted ewes had greater AUCg (7,147 vs. 5,823 +/- 361; P < 0.01) but a lower AUCi (6.4 vs. 10.2 +/- 1.9; P = 0.05) than lambs from control-fed ewes. Lambs from nutrient-restricted ewes were heavier (26.6 vs. 21.8 +/- 2.3 kg; P < 0.05) and had more backfat (0.30 vs. 0.21 +/- 0.03 cm, P < 0.05) by 4 mo of age than the lambs from control-fed ewes. At slaughter at 280 d of age, lambs from nutrient-restricted ewes remained heavier than lambs from control-fed ewes, had greater (P < 0.05) amounts of kidney and pelvic-area adipose tissue, and tended (P < 0.10) to have reduced LM and semitendinosus muscle weights as a percentage of HCW. These data demonstrate that a bout of maternal undernutrition during early to midgestation in sheep increased BW and fat deposition during adolescence and dysregulated glucose uptake in the absence of any change in birth weight.  相似文献   

7.
Multiparous Suffolk and Suffolk-cross ewes were randomly allotted to treatments within breed and year to measure effects of ram exposure, during transition from anestrus to breeding activity, on reproductive performance. Treatments were: 1) ewes joined with two mature vasectomized Rambouillet rams for 15 d before breeding (DC), 2) ewes maintained across a net wire fence from two vasectomized rams for 15 d before breeding (FC) and 3) ewes maintained approximately 400 m away from rams (NC). At the end of the 15 d, all ewes were placed in one pasture and mated to three fertile Suffolk rams during a 34-d breeding season. A total of 96 Suffolk and 177 Suffolk-cross ewes was utilized during the 3-yr experiment. A greater (P less than .05) prebreeding ovulation percentage was observed in DC and FC than in NC ewes. Mating and lambing occurred approximately 6 d earlier for DC or FC ewes than for NC ewes. A similarly designed experiment was conducted using Suffolk and Suffolk-cross ewe lambs allotted to treatments within breed and year to measure effects of ram exposure during the natural breeding season, but prior to breeding. Treatment differences were not detected (P greater than .05) for date of first observed estrus, date of lambing, percentage of ewes lambing in the first 17 d of the lambing season, number of lambs born per ewe lamb exposed or number of lambs born per ewe lamb giving birth.  相似文献   

8.
Performance of 1/2-Suffolk, 1/2-Rambouillet (Western) and 1/2-Suffolk, 1/4-Rambouillet, 1/4-Finnsheep (1/4-Finn) ewes was compared in three different lamb production systems over 3 yr. System 1 (56 ewes) involved late fall lambing over 84 d. System 2 (51 ewes) involved January and February lambing for 60 d. System 3 (47 ewes) involved March and April lambing for 45 d. Pregnancy rates for yearling ewes were lower in System 1 in yr 1 (50.7% vs 87.4% for Systems 2 and 3) but differed little among systems for older ewes or in remaining years. Average pregnancy rates for 2-yr-old and older ewes were 89.5, 94.0 and 85.7% for Systems 1, 2 and 3, respectively. When the pregnancy rate was adjusted to a 45-d lambing season, means for older ewes were 78.6, 89.5 and 85.7% for System 1, 2 and 3, respectively. Ewe breeds did not differ in their pregnancy rates. Prolificacy (lambs born per ewe lambing) was higher for 1/4-Finn ewes (1.83 +/- .06 vs 1.55 +/- .07) and was higher in System 3 (1.86 +/- .06) than in Systems 1 (1.60 +/- .07) or 2 (1.63 +/- .05). Body weight at breeding in postyearling ewes was less in System 3 (64.3 kg); than in Systems 1 or 2 (average of 73.1 kg). Breeds did not differ in weight at 1 or 2 yr of age, but Western ewes were 2.1 +/- 1.1 kg heavier as 3-yr-olds.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

9.
Fifty-two Targhee twin-bearing ewes were used in a factorial arrangement of treatments to investigate the role of supplemental vitamin E (vit E); 0 (NE) vs 400 IU of vit E x ewe x (-1)d(-1) (E) and parainfluenza type 3 (PI3) vaccination; none (NP) vs PI3 vaccination (P) in immune function. Parainfluenza type 3 vaccination was used to evoke an immune response. Ewes receiving PI3 were vaccinated at 49 and 21 d before the expected lambing date. Ewes receiving vit E were orally dosed daily, 32 to 0 d before lambing. Blood was collected from ewes at the time of the initial PI3 vaccination and 4 h postpartum. Blood was collected from lambs (n = 104) at 3 d postpartum. Ewe and lamb sera were analyzed for anti-PI3 antibody titers, immunoglobulin G (IgG) titers, and vit E concentrations. Colostrum was collected 4 h postpartum and analyzed for IgG. The model for ewe and lamb analysis included the main effects of vit E and PI3, sex (lambs model only), and their interactions. No interactions were detected (P > 0.20) for any ewe or lamb variables. Serum anti-PI3 titers were greater (P < 0.01) in P ewes and their lambs than NP ewes and their lambs. Serum vit E concentrations were greater (P < 0.01) in E ewes and their lambs than NE ewes and their lambs. Colostral IgG titers and serum anti-PI3 titers did not differ (P > 0.20) between E and NE ewes. Serum IgG titers in E ewes and their lambs did not differ (P > 0.15) from IgG titers in NE ewes and their lambs. Lamb anti-PI3 titers did not differ (P = 0.76) between lambs reared by E and NE ewes. These results indicate that, although supplemental vit E to the ewe increased lamb serum vit E concentration, it had no effect on measures used in this study to assess humoral immunity in the ewe or passive immunity to the lamb.  相似文献   

10.
From calving through first estrus, 30 Brangus females were assigned equally to one of three diets to study the effect of postpartum nutrient intake and body condition on the ability of the pituitary to release luteinizing hormone (LH) and on the postpartum interval to estrus (PPI). The postpartum diets were calculated to achieve a 1) low [90% of the National Research Council (NRC) recommendations], 2) maintenance (100% of the NRC recommendations), or 3) high (110% of the NRC recommendations) level of nutrient intake. The females were group-fed within a treatment and calves were allowed to suckle ad libitum. Cow weight, body condition score and calf weight were recorded 24 h aftercalving, d 20 postpartum and at first behavioral estrus. On d 21 postpartum, blood samples were collected via jugular cannulae at 15-min intervals for 4 h, followed by a 100-micrograms im injection of gonadotropin-releasing hormone (GnRH) and continued sampling at 15-min intervals for an additional 6 h to determine serum LH. Although there was a significant decrease in PPI with increasing levels of nutrient intake (low = 57.5 +/- 8.8 d; maintenance = 40.3 +/- 6.6 d; high = 34.7 +/- 5.1 d), there were no differences in any of the observed LH characteristics (or variables) due to treatment. There were, however, marked differences in both the PPI and LH characteristics when data were analyzed on the basis of ability to maintain body condition from calving through 20 d postpartum, regardless of calculated dietary treatments. Cows that maintained body condition (MBC) had a shorter PPI [MBC, 31.7 +/- 2.8 vs lost (LBC) 60.0 +/- 7.5 d; P less than .01], higher basal levels of endogenous LH (MBC, .83 +/- .09 vs LBC, .61 +/- .04 ng/ml; P less than .025), higher GnRH-induced peak LH concentration (MBC, 58.99 +/- 11.15 vs LBC, 38.86 +/- 8.37 ng/ml. P less than .10), higher LH levels throughout the GnRH-induced LH surge (P less than .001), and greater release curve areas for the endogenous (MBC, 124.6 +/- 13.3 vs LBC, 91.7 +/- 5.6 units; P less than .025), GnRH-induced (MBC, 4370.8 +/- 699.5 vs LBC, 3039.7 +/- 683.3 units; P less than .10) and total (MBC, 4510.7 +/- 706.7 vs LBC, 3141.9 +/- 684.7 units; P less than .10) LH release.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   

11.
This study evaluated the effect of microencapsulated LHRH agonist (D-Trp6-LHRH) on gonadotropin release and occurrence of estrus in early postpartum beef cows. Angus cows (n = 54) were assigned randomly to two treatment groups at d 5 postpartum. Group 1 received a single i.m. injection of D-Trp6-LHRH (LHRH-A) encapsulated in poly-DL-lactide-coglycolide, calculated to release 15 micrograms of LHRH-A per day for 30 d (n = 23). Group 2 received vehicle only (control, n = 31). Blood samples (15-min intervals for 6 h) were obtained on d 5, 10, 20, 30, and 40 postpartum for evaluation of LH and FSH concentrations (n = 12 per group). Days to first postpartum estrus were reduced by treatment with LHRH-A (Group 1, 43.7 +/- 4.2 d vs Group 2, 55.9 +/- 4.7 d; P < .05). However, days to conception were similar between groups (68.9 +/- 7.9 vs 76.7 +/- 6.7 d, respectively). On the day of treatment, cows treated with LHRH-A had higher mean concentrations of LH and FSH than did controls (8.3 +/- 1.4 vs 2.0 +/- .4 ng/mL for LH and 211.0 +/- 8.6 vs 51.2 +/- 2.7 ng/mL for FSH (P < .05). There were no differences in mean concentrations of LH or FSH between treatment groups on d 10, 20, 30, and 40 postpartum. Cows given LHRH-A had more (P < .05) LH pulses on d 10 and 30 postpartum than did controls. This study demonstrated that microencapsulated D-Trp6-LHRH reduced the postpartum anestrous interval in suckled beef cows.  相似文献   

12.
A study was done to test whether ovulatory follicles destined to form subfunctional corpora lutea differed from normal ovulatory follicles in steroidogenic function. Twenty-five ewes were treated with prostaglandin F2 alpha on d 11 of the estrous cycle, then unilaterally ovariectomized before (n = 13) or after (n = 12) the surge of luteinizing hormone (LH) at the induced estrus to collect "control" follicles, which would have produced normal corpora lutea. In 15 ewes, the second ovary was removed 63 to 84 h later to collect "treated" follicles before (n = 7) or after (n = 8) the second expected surge of LH. Five ewes (control) were allowed to ovulate from the remaining ovary at first estrus and another five (treated) at the second estrus (3 to 4 d later). Treated ewes had lower serum progesterone than control ewes during the ensuing cycle (P less than .05). Treated follicles contained less estradiol in the theca (4.4 +/- .6 vs 10.0 +/- 2.5 ng; P less than .05), less androstenedione (.1 +/- .1 vs 1.0 +/- .2 ng) and estradiol (.5 +/- .1 vs 2.9 +/- 2.2 ng) in the granulosa (P less than .05) and less progesterone in the follicular fluid (.8 +/- .4 vs 3.3 +/- .8 ng; P less than .05) than control follicles, when removed before the surge of LH. Follicles removed after the surge of LH did not differ. In conclusion, ovulatory follicles with low steroidogenic function became corpora lutea that secreted lower-than-normal quantities of progesterone.  相似文献   

13.
The interaction among exogenous estradiol-17 beta, naloxone and gonadotropin releasing hormone (GnRH) in the control of luteinizing hormone (LH) secretion was studied in intact postpartum ewes nursing their offspring. One-half of 30 fall-lambing ewes were implanted subcutaneously with an estradiol-17 beta containing Silastic capsule between postpartum d 1 and 12 which doubled their serum concentrations of estradiol (16.0 +/- .1 vs 8.4 +/- .1 pg/ml). Blood samples were collected from implanted and non-implanted ewes at 15-min intervals for 5 h on d 3, 8, 13, 20 and 28 postpartum. Pre-injection samples were collected for 1 h, and ewes were injected with saline, naloxone (NAL;1 mg/kg) or GnRH (100 micrograms/ewe). When averaged across all days and implant groups, serum LH in the three post-NAL samples was higher (P less than .05) than in the three pre-NAL samples (3.6 +/- 1.2 vs .6 +/- .2 ng/ml). Post-GnRH concentrations of serum LH were lower (P less than .05) in estradiol-implanted ewes than in non-implanted ewes on d 8 and 13, but there were no differences in any LH characteristics on d 20 and 28 after implant removal on d 12. In non-implanted ewes, serum LH responses to GnRH increased (P less than .05) eightfold from d 3 (3.8 +/- 1.4 ng/ml) to d 8 (31.6 +/- 1.4 ng/ml), remained elevated through d 20, but declined by d 28 (10.8 +/- 1.4 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

14.
Neonatal lamb mortality is a major factor affecting profitability in the sheep industry, and lamb thermogenesis is a key element in neonatal lamb survival. Increased lamb vigor has been reported when ewes were supplemented during late gestation with algae-derived docosahexaenoic acid (DHA); however, the effects of DHA on lamb thermogenesis and immunocompetence have not been investigated. Eighty twin-bearing Targhee ewes (ages 2 to 5 yr; 68.5 ± 3 kg) were assigned randomly to 1 of 2 supplement treatments to determine the effects of feeding DHA to ewes during late gestation and early lactation on lamb thermogenesis, serum metabolites and hormones, and lamb growth. Supplement treatments were 12 g·ewe(-1)·d(-1) of algae-derived DHA (DHA Gold Advanced Bionutrition Corp., Columbia, MD; algae-derived DHA); and no algae-derived DHA (control). Supplements were individually fed daily during the last 30 d (±7 d) of gestation and pen fed (6 pens/treatment with 6 or 7 ewes/pen) during the first 38 d (±7 d) of lactation. One hour after lambing and before nursing, twin-born lambs were weighed, blood sampled via jugular puncture, and placed in a dry cold chamber for 30 min (0°C), and rectal temperatures were recorded every minute for 30 min. Lambs were removed from the cold chamber, blood sampled, warmed for 15 min, and returned to their dam. Ewes were blood sampled, and colostrum samples were collected 1 h postpartum. Ewe and lamb sera were assayed for glucose, NEFA, cortisol, and leptin. Lamb rectal temperature, glucose, NEFA, cortisol, leptin, and birth weights did not differ between treatments. The BW at 38 d was greater (P = 0.03) for lambs born to control ewes than for lambs born to algae-derived DHA-supplemented ewes; however, the colostrum of algae-derived DHA-supplemented ewes had a greater specific gravity (P = 0.05) than for control ewes. Overall, despite a potentially positive effect on ewe colostral IgG concentrations, supplementation of algae-derived DHA during late gestation and early lactation had a negative effect on lamb BW and did not affect indices of lamb thermogenesis.  相似文献   

15.
Milk production and lamb growth were characterized in 118 multiparous, 3- to 7-yr-old Rambouillet, Columbia, Polypay, and Suffolk ewes under spring sage range and high mountain meadow grazing from 28 to 98 d postpartum. Daily milk yield as measured by the lamb suckling weight differential technique did not differ (P greater than .05) among breeds, although milk production of Suffolk ewes tended to be higher than that of the other three breeds. Within the Rambouillet, Columbia, and Polypay breeds, total estimated yield of ewes with twins was 13 to 17% higher than that of ewes with singles, whereas in the Suffolk breed, suckling twins increased total milk yield 61% over that of ewes with singles. Twin lambs induced a larger differential in dam milk production in late lactation (70 to 98 d) than in earlier lactation (28 to 70 d). Number of lambs did not influence milk protein, Ca, or P content (P greater than .05). Fat levels in colostrum and 4-d milk were elevated 14 and 20%, respectively, in ewes suckling twins compared with ewes suckling singles. Under range conditions, Suffolk ewes suckling single or twin lambs lost more BW (12 and 21% of 4-d postpartum body weight, respectively) than Rambouillet (4 and 7%), Columbia (5 and 8%), or Polypay (8 and 8%) ewes. Correlation coefficients of milk production and lamb growth rate were positive and significant (P less than .05) up to 56 d of age. Growth rate was less closely associated with milk production for twin than for single lambs.  相似文献   

16.
Seventy-seven multiparous beef cows (Hereford and Angus x Hereford) with thin to moderate BCS at calving were used to evaluate the effects of body condition at parturition and BW change after calving on duration and occurence of luteal activity before and after first estrus. Blood samples were collected twice weekly after parturition to determine the occurrence of the first postpartum luteal activity (LA, progesterone > or = 0.5 ng/mL). Weight changes and BCS were determined at 2-wk intervals. Cows were exposed to bulls and observed twice daily for behavioral estrus. Luteal activity was classified as normal if plasma concentrations of progesterone were > or = 0.5 ng/mL for at least 11 d, or short if concentrations of progesterone were > or = 0.5 ng/mL for 10 d or less. The interval from parturition to first normal LA was shorter (P < 0.001) for moderate condition (BCS > or = 4.5) than for thin (BCS < or = 4) cows (58.3 +/- 3.2 vs. 93.3 +/- 5.1 d, respectively). Interval to first estrus also was shorter (P < 0.001) for moderate than for thin cows (53.3 +/- 3.7 vs. 89.3 +/- 5.6 d, respectively). Before the first normal LA, 78% of cows had an increase in progesterone for < 11 d. Postpartum weight change and BCS at calving did not influence the incidence of estrus associated with first normal LA. After the first estrus, 72% of cows had normal LA, 16% had a short luteal phase, and 12% lacked LA. Postpartum weight change and BCS did not influence the length of LA associated with the first estrus. Cows with normal LA had increased (P < 0.05) maximal concentrations of progesterone compared with cows that had a short luteal phase. When a transient increase in progesterone occurred before first behavioral estrus, 81% of cows had normal luteal function after estrus. We conclude that when beef cows are in thin to moderate body condition at calving, postpartum BW change and BCS at calving do not influence the duration of luteal activity before or after the first postpartum estrus.  相似文献   

17.
The objective of this study was to compare rebreeding activities of spring- vs fall-lambing Polypay, Dorset, St. Croix and Targhee ewes that either suckled their lambs for 40 d or had lambs weaned at birth. Seasonal effects of male fertility were reduced by utilizing an excess number of fertile rams in the spring. Plasma concentrations of progesterone were monitored to assess days to the first normal ovulation, days to conception and estrous vs anestrous activity. Breed, season and lactation affected the rebreeding performance. Dorset ewes had similar conception rates between spring and fall but a shorter interval from lambing to first ovulation in the fall. Polypay and Targhee ewes were the opposite; they had higher conception rates in fall than in spring matings with no seasonal influence on postpartum interval. Postpartum ewes in the fall had higher conception rates, and fewer of these ewes became anestrous or had estrous cycles of abnormal duration than of those ewes lambing in the spring. Ewes that suckled for 40 d in the spring had delayed estrous activity, but when these ewes became estrual they had higher conception rates than ewes whose lambs were weaned at birth. Lactation had no inhibitory affect on the postpartum interval of fall lambing ewes. These data suggest that the response of different breeds to various components of postpartum fertility varies with season and management of the flock.  相似文献   

18.
One hundred ewes were utilized to determine the effects of interferon supplementation on the number of ewes pregnant and embryonic survival. Ewes were checked twice daily (0700 and 1600) for estrus using fertile rams. On d 12 through 16, ewes received twice-daily i.m. injections of either recombinant bovine interferon alpha I1 (2 mg IFN) or vehicle. Ewes remained penned with rams and were observed for subsequent estrous activity for at least 35 d after mating. To determine the number of fetuses and corpora lutea, all ewes were subjected to one surgery during mid-pregnancy (d 45 to 80). More (P less than .05) ewes were pregnant after treatment with IFN vs vehicle (45 of 49, 92% vs 37 of 49, 76%, respectively). The interestrous interval for ewes that were treated with IFN and did not conceive was longer (P less than .05) than for ewes given vehicle (26 +/- 1 vs 17 +/- 2 d, respectively). Embryonic survival (98.2 vs 87.9%; P less than .05), calculated as the number of fetuses present at the time of laparotomy and expressed as a percentage of the ovulation rate, and percentage of ewes with 100% fetal survival (96 vs 76%; P less than .05) were greater after treatment with IFN. It was concluded that supplementation of IFN increased both the number of ewes pregnant and embryonic survival.  相似文献   

19.
Spring-calving, crossbred (1/4 to 3/8 Brahman) primiparous (n = 56) and multiparous (n = 102) beef cows were used to evaluate the effects of progesterone, delivered via a controlled internal drug-releasing (CIDR) device, and prostaglandin F(2alpha) (PGF(2alpha)) on estrous behavior, synchronization rate, initiation of estrous cycles, and pregnancy rate during a 2-yr period. To determine luteal activity, weekly blood samples were collected 3 wk before initiation of a 75-d breeding season. Treated cows received a CIDR for 7 d beginning on d -7 of the breeding season. On d 0, CIDR were removed, and cows receiving CIDR were administered PGF(2alpha); control cows received no treatment. Cows were exposed to bulls, and estrous activity was monitored using a radiotelemetry system for the first 30 d of the breeding season. Treatment with CIDR-PGF(2alpha) increased (P < 0.05) the number of mounts received (22.5 +/- 3.0 vs. 13.7 +/- 3.9 for CIDR-PGF(2alpha) vs. untreated control cows, respectively) but did not influence duration of estrus or quiescence between mounts. Number of mounts received and duration of estrus were greater (P < 0.05) in multiparous compared with primiparous cows. Synchronization of estrus was greater (P < 0.05) in cows treated with CIDR-PGF(2alpha) (56%) compared with control cows (13%) during the first 3 d of the breeding season. More (P < 0.05) anestrous cows treated with CIDR-PGF(2alpha) than anestrous control cows were in estrus during the first 3 d (59 vs. 12%) and 30 d (82 vs. 63%) of the breeding season. Treatment with CIDR-PGF(2alpha) decreased (P < 0.05) the interval to first estrus after treatment during the first 30 d of the breeding season compared with control cows (5.5 +/- 1.1 vs. 9.0 +/- 1.4 d). First service conception rate was greater (P < 0.05) in CIDR-PGF(2alpha)-treated cows compared with control cows. Cyclic cows at initiation of the breeding season had an increased (P < 0.05) 75-d pregnancy rate compared with anestrous cows, and the pregnancy rate tended (P = 0.10) to be greater in multiparous compared with primiparous cows. We conclude that treatment of Brahman-influenced cows with progesterone via a CIDR for 7 d, along with administration of PGF(2alpha) at CIDR removal, increases the number of mounts received, improves synchronization and first service conception rates, decreases the interval to first estrus after treatment, and may be effective at inducing estrous cycles in anestrous cows.  相似文献   

20.
Two winter feeding trials (1985-86; 1986-87) were conducted to evaluate the productivity of gestating ewes fed lasalocid (L) and two supplement levels while grazing Montana winter range. Five hundred range ewes were randomized within age and breed each year and allotted to .15 or .23 kg hd-1.d-1 of a 20% CP supplement and either no L or L at 70 mg hd-1.d-1. Feed treatments began on 18 Dec. approximately 100 d before the first expected lambing date and continued for 84 d. Ewes fed .23 kg of supplement per day gained more (P less than .01) total weight (4.9 vs 4.0 kg) during the 84-d experiment and had higher (P less than .05) grease fleece weights (4.2 vs 4.0 kg) than those fed .15 kg of supplement. Lasalocid had no effect (P greater than .05) on ewe weight change or grease fleece weights. Supplement level had no effect (P greater than .05) on reproduction, lamb mortality and lamb performance. Ewes fed L had a greater (P less than .05) percentage of lambs born per ewe than those not fed L (120.7 vs 112.1%); lamb performance was similar (P greater than .05) between treatments. However, because a greater percentage of lambs were born per ewe starting the experiment, ewes fed L produced more (P less than .05) kilograms of weaned lamb than those not fed L (25.9 vs 23.4 kg). In conclusion, ewes fed L and grazing winter range weaned more kg of lamb than did controls because of an improved lambing percentage.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

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