Reproductive performance of Dorset ewes in the Cornell University STAR accelerated lambing program was evaluated. This program consists of five 30-d concurrent breeding and lambing periods per year beginning on January 1 (Sl), March 15 (S2), May 27 (S3), August 8 (S4) and October 20 (S5). Optimally, a ewe could lamb every 7.2 mo beginning at 1 yr of age, Records on 1,084 ewes over 7 yr beginning S1, 1982 Reproductive traits considered were ewe fertility, prolificacy, days to first lambing (DFL) and days between lambing (DBL). Fertility and prolificacy differed (P < .001) by exposure seasons. Exposure during favorable seasons (S1, S4, S5) increased fertility (P < .001) and prolificacy (P < .01) over that observed in unfavorable seasons (S2, S3). On average, first lambing occurred at 476 ± 5 d with ewe lambs first exposed during S1, S4 and S5 lambing at younger ages (P < .001). Ewes had more DBL (P < .001) if initial exposure following lambing occurred during an unfavorable season. A curvilinear relationship of ewe age with fertility (P < .001) , prolificacy (P < .01) and DBL (P < .05) was observed in ewes less than 4 yr old. At first exposure following lambing, fertility was lower (P < .001) than at subsequent exposures and ewes that had nursed lambs were less prolific (P < .01) than those that had not. Prolificacy and nursing status had little effect on fertility or DBL (P > .10). Fertility was transformed to an underlying liability scale based on the expected fertility of ewes of a given age and reproductive history. Variance components were estimated by least-squares (LS) and restricted maximum likelihood (REML) procedures. First-exposure fertility was not heritable. heritabilities for fertility at first post-lambing exposure, first-lambing prolificacy, and second-lambing prolificacy were .191 ± .088 (LS) and .200 ± .132 (REML), .914 ± .091 (LS) and .158 ± .144 (REML), and .168 ± .082 (LS) and .210 ± .137 (REML), respectively. Genetic variation in DFL (P < .01) and DBL (P < .001) was found. Although intrasire ewe variation was detected for prolificacy (P < .001) and DBL (P < .01), repeatability estimates were low and smaller than heritability. / Ph. D.

Expression of membrane-type matrix metalloproteinases (MT) and tissue inhibitors of matrix metalloproteinases (TIMP) was evaluated in sheep embryos and uterus during the pre- and peri-implantation periods. Embryos and uterine samples were surgically collected from ewes on days 9, 11, 13, and 15 of pregnancy (n=3 ewes/day) and of the estrous cycle (n=2 ewes/day). Total RNA was extracted and RT-PCR were performed using primers specifically designed from published human, mouse, and bovine complete cDNA sequences for MT-1, -2, -3, and -5, and TIMP-1, -2 and -3. Multiplex PCR were performed on uterine samples for each gene at optimal cycles and temperatures with 18S rRNA as the internal standard. For embryos, PCR were conducted for 40 cycles at optimal temperatures. MT-1, -2, -3, and -5 were observed in pregnant and nonpregnant uterus during all days of collection. No difference (P>0.10) was observed in MT-1 or -2 expression due to day of collection. However, pregnant uterus expressed more (P=0.096) MT-1 than nonpregnant uterus, whereas expression of MT-2 was greater (P<0.05) in nonpregnant compared to pregnant uterus. No differences (P>0.10) in MT-3 expression were observed due to pregnancy status, however Day 9 and 11 expressed more MT-3 than Day 15. Uterine MT-5 expression was not different (P>0.10) between pregnant and nonpregnant females, however Day 15 uterus expressed less (P<0.05) MT-5 then Day 11 and 13 uteri. TIMP-1 expression was greater (P<0.05) in pregnant compared to nonpregnant uterus, but did not differ (P>0.10) by day of collection. TIMP-2 did not differ (P>0.10) by pregnancy status or day of collection but the interaction was significant (P<0.05). TIMP-2 expression was greatest in Day 9 pregnant uterus and least in Day 9 nonpregnant uterus. No difference (P>0.10) was observed in expression of TIMP-3 due to day of collection or pregnancy status. Embryos expressed MT-3 and -5 during Days 9-15 of development, however, MT-1 and -2 were not detected. The presence of MT and TIMP in the endometrium suggests these proteins may play important roles in regulating extracellular matrix degradation and activating other matrix metalloproteinases for endometrial remodeling and preparation for implantation. Embryonic MT may participate in the processes of embryonic expansion, elongation and attachment. / Graduation date: 2002

Experiments were conducted to determine whether endogenous progesterone regulates synthesis and/or secretion of luteal oxytocin (OT). In experiment 1, mature ewes (n=5 per group) were assigned randomly to control or mifepristone (RU 486) treatment groups. Ewes were injected twice daily s.c. with vehicle or 10 mg RU 486 from days 5-7 of the estrous cycle (estrus=day 0). On day 8, following an i.v. prostaglandin F₂α (250 μg cloprostenol) challenge, venous samples were collected at frequent intervals to determine plasma OT concentrations. Plasma OT in RU 486-treated animals did not differ significantly from those of the control animals (P>0.05). In Experiment 2, ewes were injected s.c. daily with vehicle or 175 mg RU 486 from days 2-5 of the estrous cycle followed by a prostaglandin F₂α (250 μg cloprostenol) challenge on day 6. Four of five RU 486-treated ewes exhibited "split-estrus" (estrous behavior through 36 hours and again 84 to 108 hours after the onset of initial estrus). There was no significant difference in mean plasma OT or progesterone levels between treatment groups (P>0.05). Mean mature corpus luteum (CL) weights of control and RU 486-treated ewes on day 6 did not differ (394.8 ± 28.8 vs. 319.5 ± 48.3 mg; P>0.05). Mifepristone-treated ewes contained mature CL, new CL (2 of 4 ewes), and/or preovulatory follicles (≥ 10 mm, 2 of 4 ewes). Average interestrous interval for RU 486-treated ewes was 9 days longer than that of control animals (26.2 ± 2.9 vs. 17 ± 0.5 days; P<0.025). A subsequent study was conducted to determine the effects of gonadotropin-releasing hormone (GnRH)-stimulated release of luteinizing hormone (LH) on luteal OT and progesterone production in beef heifers. Ten heifers with normal estrous cycles were assigned randomly in equal numbers to a control and treatment group. On day 2 of the estrous cycle (estrus=day 0) heifers were injected with either physiological saline or 100 pg GnRH every 4 hours for 56 hours. Samples were collected 0 min pre- and 180 min post-GnRH challenge for progesterone analysis. Sixty hours after the initial injection of GnRH or saline, heifers were challenged with an i.v. injection of 500 pg prostagland in F₂α (cloprostenol) and blood was collected at frequent intervals for OT analysis. Luteal OT synthesis was suppressed (P<0.01) in heifers receiving repeated injections of GnRH compared to saline-treated control animals. Progesterone secretion was significantly greater in saline-treated animals compared to GnRH-treated animals pre- and post-challenge (1.0 ± 0.06 vs. 0.93 ± 0.11 ng/ml and 1.16 ± 0.05 vs. 0.96 ± 0.13 ng/ml, respectively; P<0.05). / Graduation date: 2003

Graduation date: 2003

Graduation date: 1998

Two trials were conducted over consecutive years to examine the effects of ewe body condition and post-mating nutrition on ovulation rates and embryo survival. Trial 1 used 146 Polypay ewes ranging in age from 5 to 8 years in a 3 x 2 factorial array of pre-mating (high-H, low flushed-LF and low unflushed-L) and post-mating nutrition (high and low) treatments. Trial 2 was a 2 x 2 x 2 factorial array of 60 Polypay and 60 Coopworth x Polypay (C x P) three year old ewes, two pre-mating (H and LF) and two post-mating (high and low) treatments. To estimate timing and extent of embryo loss, two methods of embryo detection were employed during Trial 2. Real-time ultrasound was performed on all ewes at 21, 28, 34 and 45 days post-mating. Blood samples were also collected on these days for analysis of Pregnancy-specific Protein B (PSPB) levels. There was no effect of pre-mating treatment or ewe age on ovulation or conception rates for Trial 1. Pre-mating treatment was significant in Trial 2, with H ewes having higher ovulation rates than LF ewes. Pre-mating treatment, post-mating treatment, ewe age (for Trial 1) and genotype (for Trial 2) had no effect on mean litter size in either trial. Analysis of litter size among ewes with twin and triple ovulations showed pre-mating treatment to be significant among triple ovulators in Trial 1, where L ewes had much lower litter size (1.86) than LF (2.37) or H (2.60) ewes. In Trial 2, post-mating treatment was significant among the ewes with triple ovulations, with ewes on low nutrition having lower litter size (2.01) than ewes on high nutrition (2.59). Two-way interactions were significant among twin and triple ovulators in Trial 2. Breed x pre-mating interaction among twin ovulating ewes showed C x P LF ewes to have lower litter size (1.43) than the H ewes (1.87), while the opposite was true for Polypay ewes. Pre- x post-mating treatment interaction among triple ovulators showed LF ewes on low post-mating nutrition had lower mean litter size. This effect is largely due to lower litter size in the C x P triple ovulators on low post-mating nutrition. Data available from the ultrasound diagnosis showed little indication of treatment effects on amount or time of embryo loss. Ewes bearing single or multiple embryos differed in PSPB level at day 45, but not at earlier times. However, there were no differences in PSPB levels in ewes with twin or triple embryos at any of the trial days. Assay for PSPB failed to facilitate detection of the amount or time of embryo loss, as determined by ultrasound. / Graduation date: 1991

[Truncated abstract] Reproductive activity is affected by external factors such as photoperiod, social cues, stress and nutrition, all of which can alter the pulsatile activity of the GnRH neurons, which is the major neuroendocrine system used by the brain to control gonadal function. In the male Merino sheep, nutrition is one of the most powerful factors that affect pulsatile LH secretion, used commonly to bioassay GnRH neuronal activity. More accurately, the reproductive system responds to “metabolic status”, rather than “nutrition”, and the three factors that contribute to metabolic status are food intake, the amount of body reserves and the rate of energy expenditure ... In this thesis, I tested the general hypothesis that the metabolic hormones and hypothalamic neuropeptides that are known to control food intake also mediate the effect of metabolic status on the activity of the GnRH neurons ... In conclusion, the results from my experiments provide some insight into the mechanisms by which metabolic status affects reproductive activity in male sheep. Plasma insulin, which changes with alterations in metabolic status, appears to play a critical role in the regulation of GnRH neuronal activity. The level of leptin seems to have a permissive role only in lean animals. Orexins acting via OX2 receptors could be involved in the activation of reproductive function following an acute increase in nutrition. However, the neuropeptidergic systems can not be ruled out because they might be involved in very early steps of responses to nutrition.

Made available in DSpace on 2014-06-11T19:28:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-07-31Bitstream added on 2014-06-13T20:58:04Z : No. of bitstreams: 1 stradiotto_mm_me_botfmvz.pdf: 530763 bytes, checksum: e4530e5d16068efeff8131c5fdeac6fc (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Universidade Estadual Paulista (UNESP) / No Brasil, muito pouco se conhece sobre o leite ovino, pois a maioria das raças brasileiras são especializadas para a produção de carne ou lã, mas é possível encontrar animais com aptidão leiteira. O presente trabalho teve o objetivo de avaliar o efeito da gordura protegida na composição do leite, duração do anestro pós-parto, resposta às infecções parasitárias e desempenho dos cordeiros, em ovelhas da raça Bergamácia. Utilizou-se 77 ovelhas distribuídas em 2 grupos por ordem de parição e idade, em dois tratamentos: dieta Controle (C): silagem de milho e concentrado; e dieta com Gordura Protegida (GP): a mesma de C e adição de gordura ruminalmente protegida (35 g/ovelha/dia) ao concentrado. As dietas foram isoenergéticas e isoprotéicas, contendo 70% NDT e 16% PB com base na matéria seca. Os cordeiros permaneceram com suas mães até 45 dias de idade, quando foram desmamados. As ovelhas, 48 horas pós-parto, foram ordenhadas mecanicamente uma vez ao dia, às 7h 00, com produção de leite mensurada diariamente pelo período de 60 dias. Amostras de leite foram coletadas semanalmente para análise da composição centesimal e teor de caseína. O tratamento GP apresentou maior produção de leite média diária após a desmama (0,531 vs 0,489 kg/cab/dia), entretanto, a produção de todo o período experimental não foi diferente entre os tratamentos (0,453 vs 0,468 kg/cab/dia, para C e GP, respectivamente). Não foram observadas diferenças entre tratamentos para os teores de gordura do leite até a 6ª semana de lactação, sendo verificadas apenas após a desmama. Ambos teores de alfa e beta caseínas apresentaram diferenças entre tratamentos (30,00 vs 18,50 Kda para alfa caseína e 32,48 vs 25,65 Kda para beta caseína, para os tratamentos C e GP respectivamente). O sistema de produção utilizado provavelmente foi uma variável importante nos resultados... / Little is known about sheep milk in Brazil because the majority of Brazilian breeds are for meat production or wool, but is possible to find some type milk animals. The present work aimed to evaluated the effect of protected fat on milk composition, time to estrus regress after lambing, gastrointestinal nematodes infections and lamb performance of Bergamasca ewes. It were used 77 ewes allocated in 2 homogenous groups by parity and age. Diet control (C): corn silage and concentrate; diet with protected fat (GP): same of C and protected fat added (35 g/ewe/day) to the concentrate. Diets were isoenergetic and isonitrogenous with 16% of CP and 70% of TDN on dry matter basis. In both groups, lambs were kept with their mothers in pasture during the day, being separated at night. After morning milking, lambs were returned to their mothers, being weaned at 45 days of age. Ewes from both groups were mechanically milked for 60 days. Treatment GP presented higher daily average milk productionafter lambs weaning (0.5351 vs 0.489 kg/head/d), horewer, average milk production of the whole period was not different (0.453 vs 0.468 kg/head/d for C and GP, respectively). There was no found difference between treatments for fat content milk until 6th week of lactation. Alfa e beta casein content has presented differences between treatment (30,00 vs 18,50 Kda for alfa casein and 32,48 vs 25,65 Kda for beta casein, for C e GP respectively). The production system used probably was an important variable in that results due to lamb presence during a moment in the day induced milk retention during ewe machine milking.

Two experiments determined the effects of flaxseed supplementation on reproductive parameters in sheep. In experiment one, 240 multiparous Rambouillet ewes were assigned to one of two treatments: basal ration alone or basal ration with a Flaxlic® Sheep Tub offered over 35 days. Serum was collected weekly for progesterone (P4). Flaxseed supplementation did not improve progesterone concentration or reproductive parameters (P ≥ 0.26). In experiment two, 120 Rambouillet ram lambs were assigned to one of two treatments: basal ration alone or basal ration with a Flaxlic® Sheep Tub offered over 112 days. Scrotal circumference measurements, serum for testosterone, and semen were collected on day 84 and 112. Day effects were found for select semen measurements, testosterone, weight, and scrotal circumference (P ≤ 0.05). There was no effect of treatment on testosterone concentration (P = 0.99) or any semen quality characteristics (P ≥ 0.33). Overall, tub supplementation did not alter reproductive ability.

The present studies were conducted to check the effects of acute ram introduction into a flock of anestrus ewes in Virginia. Ewes were bled via jugular venipuncture twice weekly and serum samples were radioimmunoassayed for progesterone (P4) content as an indicator of estrous activity. All rams were fitted with crayon equipped marking harnesses for use as an indicator of mating behavior in ewes. The first study tested the effects of introduction of vasectomized rams into a flock: of' 50 Dorset (D) and 50 Hampshire (H) purebred ewes in either May or June. More D ewes ovulated (96% vs 72% for H ewes) and mated (80% vs 20% for H ewes) in May. Of ewes which mated in May 65% D but no H ewes continued to cycle in June after removal of rams. Of ewes exposed to rams in June no difference among breeds was observed in percentage of ewes ovulating but more D ewes (72%) mated than H ewes (44%). Twenty-four percent of D but no H ewes cycled continuously throughout the 68 d or the study. Lambing date significantly affected mating behavior in H but not D ewes. The second study tested the effects of ram breed on incidence of mating and subsequent lambing in Rambouillet x Q Suffolk ewes In June and July of 1984 and 1985. Ewes were Q pre-exposed to either confined Suffolk (S) or Dorset (D) Q yearling rams or no (N) ram for 2 wk prior to breeding by Q either S or D rams. Lambing date was significantly affected by breeding treatment in 1984 and by pre-exposure treatment in 1985. Sixty-three percent of the ewes lambed in 1984 while 65% lambed in 1985. / Master of Science