M C Lucy

..The slower fetal development may predispose lactating cows to fetal loss if developmental milestones are not reached...

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..Future studies of GH should focus on its direct effects on the follicle as well as its indirect effects mediated by shifts in nutrient metabolism, insulin sensitivity, IGF1 and IGFBP...

..Collectively, these data demonstrate that NFKB activation may occur during the period of uterine receptivity in both the cyclic and pregnant endometrium...

..Understanding the mechanisms through which metabolic hormones control ovarian function may lead to improved reproductive management of both pigs and cattle because lactation and post-partum reproduction are closely tied in both species...

..The long-term prognosis for genome science is good but advances will take time. Genetic selection in the genome era will be different because DNA sequence analysis may replace traditional methods of genetic selection...

..The current crisis in dairy reproduction will be permanently solved, however, when the genetics for dairy reproduction are improved through a balanced genetic selection strategy...

..Solutions to postpartum reproduction will probably arise from a variety of approaches that include traditional physiology as well as more modern genomic and proteomic technologies...

..Improved estrus synchrony led to greater pregnancy rates for beef cows and beef heifers but failed to improve pregnancy rates for dairy heifers...

..Fundamental research into anestrous, the hormonal control of the estrous cycle, and early pregnancy detection should elucidate new methods that can be used to strengthen reproductive programs on dairy farms...

..Functional components of the somatotropic axis differed for the respective strains and were consistent with strain differences in milk production, BCS, and feed allowance...

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..For this to occur, research funding must be increased above its current level and a renewed emphasis must be placed on solving the emerging crisis of infertility in dairy cows...

..Future studies of ST and IGFs should focus on the hormones, receptors, and binding proteins as well as the metabolic requirements for normal ovarian function in dairy cattle...

..We concluded that DMI partially controls GHR 1A mRNA expression in early postpartum dairy cows and that the decrease in GHR 1A in response to feed restriction persisted for at least 1 wk after ad libitum feeding was restored...

..Differences between cows (independent of their BCS and milk production) accounted for a major portion of the variation that we observed...

..This study suggests that follicular competence is likely related to steroidogenic capacity of the follicle and the endocrine environment under which growth and subsequent ovulation of the dominant follicle occurs...

..Both protocols provide opportunities for beef producers to utilize AI and potentially eliminate the need to detect estrus...

..In contrast, liver quantities of mRNA differed relative to pregnancy status. These data provide evidence that liver indices of metabolic state may be indicative of pregnancy success...

..01) compared with T2. In summary, CIDR Select improved (P < 0.01) the synchrony of estrus and ovulation compared with Select Synch + CIDR...

..Rapid changes in placental and ovarian steroids before parturition were coincident with changes in GHR 1A mRNA...

..Treatment with GnRH 1 in the earlier part of the estrous cycle (on or before d 10) increased the proportion of dominant follicles that were large enough to respond to GnRH 2 (>/=10 mm) and increased ovulatory response after GnRH 2...

..Small follicles at weaning cannot undergo compensatory growth and require additional time to reach a preovulatory size...

..Greater IGF-I (indicative of an increased GH response) may be a consequence of greater GHR 1A expression in the liver...

..01) corresponded to a decrease in postpartum interval of 0.13 d. Based on the results of this study, the inclusion of UIP in diets for primiparous heifers and its effects on postpartum interval warrant further evaluation...

..Cattle of normal size had at least 1 copy of the normal GH allele. Threonine 200 in bovine GH is required for normal growth in cattle...

..Therefore, mechanisms that are independent of maternal IGF-I or placental contact area may control early fetal growth under crowded uterine conditions...

..Further studies are needed to define production systems in which the MGA Select protocol is warranted for use in beef heifers...

..This protocol may offer potential for the fixed-time insemination of replacement beef heifers...

..Independent genetic selection in 2 dairy breeds seemingly exploited a similar mechanism, reduced GHR1A expression, to decrease blood IGF1 and increase blood GH, a key hormone involved in nutrient partitioning...

..We concluded that although PGPG can be used for TAI, a simpler TAI protocol that includes the last 2 injections (PGF(2alpha), 2 d; GnRH and TAI) would be equally effective...

..Reduced GHR in liver likely contributes to a decrease in liver IGF-I production and reduced concentrations of IGF-I in blood of periparturient cows...

..In addition to reduced GHR 1A, increased SOCS-2 mRNA after parturition, perhaps because of increased E(2), may further uncouple GH signaling in the liver of the transition dairy cow...

..Shortened resynchronization protocols that do not require estrus detection may improve reproductive efficiency in dairy cattle...

..86; P<0.05), but not CTL cows (r=0.43; P>0.1). Insulin appears to be a key metabolic signal in coupling the GH-IGF axis, thus orchestrating a marked elevation in circulating IGF-I concentrations...

..Synchrony of estrus, defined as the variance in the interval to estrus from PG, however, was improved following treatment with the 7-11 Synch protocol...

..Therefore, our hypothesis that LDPP increases the expression of GHR 1A mRNA in the bovine liver is rejected...

..In summary, treating cows with PGF(2α) at CIDR removal increased the percentage of cows with all tail paint removed but did not increase percentage of pregnant cows after TAI...

..Epinephrine treatment did not affect the amount of GHR 1A or IGF-I mRNA. We conclude that the decrease in feed intake at parturition may be partially responsible for the decrease in IGF-I but may not cause the decrease in GHR 1A...

..The observations in the present study suggest that GHR expression in the bovine may be controlled by translational mechanisms in addition to complex transcriptional mechanisms...

..The GHR 1B mRNA was the major GHR mRNA in pig liver before 77 d of age. The GHR 1A mRNA increased after 42 d of age and tended to undergo specific down-regulation in response to rpST in pregnant gilts...

..Older cows have a lesser response that reduces the sensitivity of the ISG test on or before d 18...

..We conclude that a cervical insemination with low spermatozoa concentration may not result in acceptable fertility even when precisely timed relative to ovulation...

..Within the experimental model for the present study, a GnRH infusion increased follicular growth in lactating sows but follicles could not be sustained beyond the end of GnRH infusion...

..Conclusions were that the 14dCIDR_TAI program achieved acceptable FSCR (48%) and overall AI pregnancy rates (64%), but did not surpass a control program that used AI after observed estrus (61 and 70%, respectively)...

..Collectively, these observations suggest that the liver-enriched transcription factor HNF-4 plays a role in the expression of GHR 1A mRNA in bovine liver...

..Data demonstrate that in well-managed milk-fed calves the somatotropic (GH/IGF-I) axis is functionally coordinated and sensitive to nutrient intake and GH...

..0 ± 0 and 27.5 ± 2.1 d). The conclusion is that a TAI resynchronization can be programmed within 21 d of previous TAI when a d 18 pregnancy test and a rapid resynchronization are used...

..Furthermore, production factors (i.e. parity and BCS) known to influence interval to ovulation were associated with differences in follicular growth within the first 3 days after weaning in sows...

..The results of this study indicate that a short-term increase in PUN can exert direct effects on the uterine environment by decreasing uterine pH...

..These results demonstrate that GH is required for normal reproductive function in ruminant as well as nonruminant species...

..In transfected cells, the P2 promoter served as an enhancer for the P3 promoter. Existence and co-regulation of two ubiquitous promoters may be a mechanism for achieving a high level of expression of the GHR gene in multiple tissues...

..The accuracy of the test was not different for dairy and beef cattle. In conclusion, the rapid ELISA pregnancy test based on PAG was highly sensitive and specific for pregnancy detection in dairy and beef cattle...

..Other adult and fetal bovine tissues expressed 1B somatotropin receptor mRNA with a predicted protein sequence that was similar to the 1A somatotropin receptor...

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..Results indicate complex and tissue-specific regulation of the uterine IGF system components by exogenous bST. Some of those biological responses to bST may be important in early development of bovine embryos...

..Adding ECP to PGP (PGPE(1)) enhanced the expression of oestrus and increased ovulation percentage. The combination of PGP and ECP is potentially a new method to routinely synchronise oestrus and ovulation in dairy cows...

..This review highlights many fruitful directions for research, aimed at the development of strategies for nutritional management of reproduction in the high-producing subfertile dairy cow...

..30 +/- 3 h). We concluded that substituting ECP for GnRH resulted in more cows in estrus and slightly fewer ovulating...

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..We conclude that superovulatory response and pregnancy rates (respectively) are similar to control for rbST-treated cows undergoing repeated superovulations and rbST-treated recipient heifers treated at the time of embryo transfer...

..The physiological implications of these changes on maternal immune function are as yet unknown; however, they do provide a unique opportunity to identify bred, nonpregnant, cows 18 d after insemination in dairy cattle...