Show simple item record

dc.creatorBernal, Alejandroen_US
dc.descriptionDue to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to, referencing the URI of the item.en_US
dc.descriptionIncludes bibliographical references: p. 83-100.en_US
dc.descriptionIssued also on microfiche from Lange Micrographics.en_US
dc.description.abstractMultiparous nonlactacting Brahman cows (n=20) exhibiting normal estrous cycles were randomly assigned within BW and body condition score (BCS) to dietary treatments containing either 0 (C; n=10) or 4 mg/kg BW/d 6-npropyl-2-thiouracil mixed with the concentrate (PTU-n=10). Water, minerals and Coastal bermudagrass hay were available free choice and each animal received 1.8 kg of a 5.-l corn-soybean meal concentrate daily. Dietary treatments began on d 10 of the estrous cycle. Ten d after the second standing estrus, the cows received daily i.m. injections of 25 IU of porcine FSH (Superov') over a 3-d period. Estrus was induced by administration of PGF20C. Artificial insemination was performed at 12 and 24 h after observed estrus. Seven d after insemination, collection of embryos by non-surgical procedures was performed and the ovaries were removed via mid-flank laparotomy. Blood samples were collected on a weekly basis and the d of embryo collection. Serum triiodothyronine and thyroxine (T4) concentrations were lower (P<.05) in PTU than in C by d 28 of treatment and remained low thereafter. Based on T4 concentrations on d 49, five cows were hypothyroid (H-PTU) and four were partially suppressed (P-PTU). Cows in the PTU group had greater (P<.l) average daily gain, greater (P<.05) paired ovarian weights, greater (P<.06) amount of luteal tissue, greater (P<.06) number of large follicles (>4 mm), lower (P<.001) embryo recovery rate, lower (P<.l) percentage of fertilized embryos, and lower (P<.l) percentage of blastocysts collected than those in C. Further, H-PTU cows had a greater (P<.06) number of luteinized follicles and a greater (P<.05) number of corpora lutea than C. Concentration of P4 per g of luteal tissue did not differ (P>.l) between treatments, but the ratio of luteal to serum P4 on d 7 was greater (P<.l) in PTU. Serum concentration of cortisol did not differ (P>.l) between treatment groups. It was concluded that induced hypothyroidism improved weight gain and BCS, did not affect adrenal function and increased ovarian response to FSH in superovulated Brahman cows. Enhanced ovarian response may have affected fertility. Ovulation and P4 release appeared to be impaired in hypothyroid Brahman cows.en_US
dc.publisherTexas A&M Universityen_US
dc.rightsThis thesis was part of a retrospective digitization project authorized by the Texas A&M University Libraries in 2008. Copyright remains vested with the author(s). It is the user's responsibility to secure permission from the copyright holder(s) for re-use of the work beyond the provision of Fair Use.en_US
dc.subjectphysiology of reproduction.en_US
dc.subjectMajor physiology of reproduction.en_US
dc.titleEffects of induced hypothyroidism on ovarian response to superovulation of Brahman (Bos indicus) cowsen_US
dc.typeThesisen_US of reproductionen_US
dc.format.digitalOriginreformatted digitalen_US

Files in this item


This item appears in the following Collection(s)

Show simple item record

This item and its contents are restricted. If this is your thesis or dissertation, you can make it open-access. This will allow all visitors to view the contents of the thesis.

Request Open Access