EFFECT OF REDUCED ENERGY INTAKE ON PITUITARY RESPONSE TO GONADOTROPIN RELEASING HORMONE

Persistent Link:
http://hdl.handle.net/10150/282036
Title:
EFFECT OF REDUCED ENERGY INTAKE ON PITUITARY RESPONSE TO GONADOTROPIN RELEASING HORMONE
Author:
Chipepa, Joseph Augustine Shangosa
Issue Date:
1981
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
An experiment was conducted with Brangus cows to evaluate the effect of loss of body weight and condition on pituitary responsiveness to gonadotropin releasing hormone (GnRH) stimulation during late lactation. The treatment groups were lactating intact (LI), lactating ovariectomized (LO), nonlactating intact (NLI), and nonlactating ovariectomized (NLO). The study was carried out in two separate blocks, each one consisting of 3 periods. During period 1 the cows were fed a ration that supplied 90% and 88% of the NRC recommendations for TDN in lactating and nonlactating cows, respectively. This period lasted 170 in block 1 and 130 days in block 2. During period 2 the TDN was reduced to 55% or 52% for lactating and nonlactating cows, respectively. Period 2 lasted 100 days for cows in block 1 and 63 days for cows in block 2. At the beginning of period 3 TDN was further reduced to 25% or 27% for the lactating and nonlactating cows, respectively. Cows in block 1 were challenged with GnRH 40 days after the beginning of the 1st energy reduction, 30 days later and 7 days after the 2nd energy reduction. The cows in block 2 were challenged with GnRH 30 days after the 1st energy reduction, 30 days later and 25 days after the 2nd energy reduction. At the end of the study body composition parameters and organ gland weights were determined. No significant differences in the weights of the cows among the treatment groups were found. All cows were, however, losing weight through the course of this study. The nonlactating cows maintained higher body condition (P < .05) than lactating cows from 31 days after ovariectomies were performed until the end of the study. The pituitary glands were significantly heavier in the lactating ovariectomized (2.3 g vs. 1.7 g, P < .05) than the nonlactating intact cows. The weight of the adrenals per unit of body weight of LO cows was significantly higher (.057 g/kg vs. .040 g, P < .05) than among NLO cows. The percent of carcass lipid was significantly higher (P < .05) in nonlactating as compared to lactating cows. Percent moisture and protein were higher (P < .05) in lactating cows. Amount of LH released after GnRH stimulation tended to be higher in lactating than nonlactating cows. The magnitude of the LH peak did not differ significantly among the treatment groups at each of the dates GnRN was injected. Ovariectomized cows (LO and NLO) responded more rapidly (P < .05) to GnRH stimulation than intact cows (LI and NLI). Time on reduced TDN did not affect cow's response pattern after GnRH injection.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Dairy cattle -- Feeding and feeds.; Brangus cattle.; Gonadotropin.; Pituitary gland.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Animal Physiology
Degree Grantor:
University of Arizona
Advisor:
Ray, Donald E.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleEFFECT OF REDUCED ENERGY INTAKE ON PITUITARY RESPONSE TO GONADOTROPIN RELEASING HORMONEen_US
dc.creatorChipepa, Joseph Augustine Shangosaen_US
dc.contributor.authorChipepa, Joseph Augustine Shangosaen_US
dc.date.issued1981en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractAn experiment was conducted with Brangus cows to evaluate the effect of loss of body weight and condition on pituitary responsiveness to gonadotropin releasing hormone (GnRH) stimulation during late lactation. The treatment groups were lactating intact (LI), lactating ovariectomized (LO), nonlactating intact (NLI), and nonlactating ovariectomized (NLO). The study was carried out in two separate blocks, each one consisting of 3 periods. During period 1 the cows were fed a ration that supplied 90% and 88% of the NRC recommendations for TDN in lactating and nonlactating cows, respectively. This period lasted 170 in block 1 and 130 days in block 2. During period 2 the TDN was reduced to 55% or 52% for lactating and nonlactating cows, respectively. Period 2 lasted 100 days for cows in block 1 and 63 days for cows in block 2. At the beginning of period 3 TDN was further reduced to 25% or 27% for the lactating and nonlactating cows, respectively. Cows in block 1 were challenged with GnRH 40 days after the beginning of the 1st energy reduction, 30 days later and 7 days after the 2nd energy reduction. The cows in block 2 were challenged with GnRH 30 days after the 1st energy reduction, 30 days later and 25 days after the 2nd energy reduction. At the end of the study body composition parameters and organ gland weights were determined. No significant differences in the weights of the cows among the treatment groups were found. All cows were, however, losing weight through the course of this study. The nonlactating cows maintained higher body condition (P < .05) than lactating cows from 31 days after ovariectomies were performed until the end of the study. The pituitary glands were significantly heavier in the lactating ovariectomized (2.3 g vs. 1.7 g, P < .05) than the nonlactating intact cows. The weight of the adrenals per unit of body weight of LO cows was significantly higher (.057 g/kg vs. .040 g, P < .05) than among NLO cows. The percent of carcass lipid was significantly higher (P < .05) in nonlactating as compared to lactating cows. Percent moisture and protein were higher (P < .05) in lactating cows. Amount of LH released after GnRH stimulation tended to be higher in lactating than nonlactating cows. The magnitude of the LH peak did not differ significantly among the treatment groups at each of the dates GnRN was injected. Ovariectomized cows (LO and NLO) responded more rapidly (P < .05) to GnRH stimulation than intact cows (LI and NLI). Time on reduced TDN did not affect cow's response pattern after GnRH injection.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDairy cattle -- Feeding and feeds.en_US
dc.subjectBrangus cattle.en_US
dc.subjectGonadotropin.en_US
dc.subjectPituitary gland.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineAnimal Physiologyen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorRay, Donald E.en_US
dc.identifier.proquest8202543en_US
dc.identifier.oclc8714077en_US
dc.identifier.bibrecord.b13918746en_US
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