REPRODUCTIVE RESPONSE OF DAIRY HEIFERS TO CHRONIC SUBMAINTENANCE ENERGY RATIONS.

Persistent Link:
http://hdl.handle.net/10150/187766
Title:
REPRODUCTIVE RESPONSE OF DAIRY HEIFERS TO CHRONIC SUBMAINTENANCE ENERGY RATIONS.
Author:
ELHASSAN, YASSIN MOHAMED.
Issue Date:
1984
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 to study the effect of prolonged nutritional stress on the reproductive performance of twelve Holstein dairy heifers. Energy intake was reduced to 60% NE(m). The animals lost 20% of their body weight during energy restriction (97 days) and gained 29% during the high energy feeding (44 days). Estrous cycles were irregular, delayed, or ceased completely. The conception rate was only 25% during energy reduction. Cycles were reestablished and conception rate improved (67%) during the high energy feeding. Heifers were designated as fertile or infertile according to their success or failure to conceive during the energy reduction period. Serum thyroxine (T₄) levels were slightly decreased (P > .05) while triiodothyronine (T₃) levels were significantly depressed (P < .01) during energy restriction in both fertile and infertile heifers. Serum thyroxine levels were slightly increased (P > .05) in the fertile heifers, but significantly increased (P < .01) in the infertile heifers during high energy feeding. Serum triiodothyronine levels were significantly increased during high energy feeding in both fertile (P < .05) and infertile (P < .01) heifers. Concentrations of blood cortisol were relatively higher in the fertile than in the infertile heifers during the ad libitum and energy restriction periods. This suggests that the fertile heifers possessed elevated adrenal activity that the infertile heifers did not have. Concentrations of blood progesterone of the infertile heifers were severely depressed (P < .01) during the submaintenance feeding while those of the fertile group were not affected (P > .05). Blood glucose levels were significantly reduced during energy reduction and significantly increased during high energy feeding in both groups of heifers (P < .01 for infertile heifers). Blood glucose levels of the infertile heifers at time of insemination (period of energy restriction) were as low as their average levels of the period. Glucose levels of the fertile heifers at time of breeding (period of energy restriction) were greater than their mean concentration during that period and were similar to the mean levels of glucose during the ad libitum period. Low progesterone levels are indicative of ovarian inactivity under such stressful conditions. Adrenal inactivity, (as reflected by low cortisol secretion) and low blood glucose levels at time of insemination of the infertile heifers are probably associated with infertility during submaintenance feeding in dairy heifers.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Dairy cattle -- Reproduction.; Dairy cattle -- Feeding and feeds.; Animal nutrition.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Animal Physiology; Graduate College
Degree Grantor:
University of Arizona

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleREPRODUCTIVE RESPONSE OF DAIRY HEIFERS TO CHRONIC SUBMAINTENANCE ENERGY RATIONS.en_US
dc.creatorELHASSAN, YASSIN MOHAMED.en_US
dc.contributor.authorELHASSAN, YASSIN MOHAMED.en_US
dc.date.issued1984en_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 to study the effect of prolonged nutritional stress on the reproductive performance of twelve Holstein dairy heifers. Energy intake was reduced to 60% NE(m). The animals lost 20% of their body weight during energy restriction (97 days) and gained 29% during the high energy feeding (44 days). Estrous cycles were irregular, delayed, or ceased completely. The conception rate was only 25% during energy reduction. Cycles were reestablished and conception rate improved (67%) during the high energy feeding. Heifers were designated as fertile or infertile according to their success or failure to conceive during the energy reduction period. Serum thyroxine (T₄) levels were slightly decreased (P > .05) while triiodothyronine (T₃) levels were significantly depressed (P < .01) during energy restriction in both fertile and infertile heifers. Serum thyroxine levels were slightly increased (P > .05) in the fertile heifers, but significantly increased (P < .01) in the infertile heifers during high energy feeding. Serum triiodothyronine levels were significantly increased during high energy feeding in both fertile (P < .05) and infertile (P < .01) heifers. Concentrations of blood cortisol were relatively higher in the fertile than in the infertile heifers during the ad libitum and energy restriction periods. This suggests that the fertile heifers possessed elevated adrenal activity that the infertile heifers did not have. Concentrations of blood progesterone of the infertile heifers were severely depressed (P < .01) during the submaintenance feeding while those of the fertile group were not affected (P > .05). Blood glucose levels were significantly reduced during energy reduction and significantly increased during high energy feeding in both groups of heifers (P < .01 for infertile heifers). Blood glucose levels of the infertile heifers at time of insemination (period of energy restriction) were as low as their average levels of the period. Glucose levels of the fertile heifers at time of breeding (period of energy restriction) were greater than their mean concentration during that period and were similar to the mean levels of glucose during the ad libitum period. Low progesterone levels are indicative of ovarian inactivity under such stressful conditions. Adrenal inactivity, (as reflected by low cortisol secretion) and low blood glucose levels at time of insemination of the infertile heifers are probably associated with infertility during submaintenance feeding in dairy heifers.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDairy cattle -- Reproduction.en_US
dc.subjectDairy cattle -- Feeding and feeds.en_US
dc.subjectAnimal nutrition.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineAnimal Physiologyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.identifier.proquest8424921en_US
dc.identifier.oclc691415352en_US
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