Search Results

You are looking at 1 - 2 of 2 items for

  • Author: J. B. HOLTON x
  • Refine by Access: All content x
Clear All Modify Search
Free access

G. L. FOSS, J. B. HOLTON, and F. J. W. LEWIS

Oral contraceptives containing oestrogen and progestagen in high dosage may produce many undesirable side effects. The risk of thrombo-phlebotic episodes (Vessey & Doll, 1969) has caused much concern, but the possible long-term effects of the numerous metabolic changes have also to be considered. Amongst the latter, impaired glucose tolerance (Wynn & Doar, 1969) and increased levels of serum glutamic—pyruvate transaminase (SGPT) have been reported (Larsson-Cohn, 1965).

The use of norgestrel alone, given continuously in low dosage of 50 μg, is slightly less effective as a contraceptive than conventional combinations of oestrogen and progestagen (Foss, Svendsen, Fotherby & Richards, 1968) and 22% of cycles are shorter than 23 days in the women on this regimen, but the incidence of side effects is much lower (Foss, 1968). With the elimination of the

Restricted access

Zachary K Seekford, Dylan B Davis, Mackenzie J. Dickson, Lucas Melo Goncalves, Samir Burato, Matthew P. Holton, Julie Gordon, Ky G. Pohler, G. Cliff Lamb, Timothy D. Pringle, Robert L. Stewart, Maria S. Ferrer, Pedro Fontes, and John J Bromfield

Bulls used in cattle production are often overfed to induce rapid growth, early puberty and increase sale price. While the negative consequences of undernutrition on bull sperm quality are known, it is unclear how a high gain diet influences embryo development. We hypothesized that semen collected from bulls fed a high gain diet would have a reduced capacity to produce blastocysts following in vitro fertilization. Eight mature bulls were stratified by body weight and fed the same diet for 67 d at either a maintenance level (0.5% body weight per day; n = 4) or a high gain rate (1.25% body weight per day; n = 4). Semen was collected by electroejaculation at the end of the feeding regimen and subjected to sperm analysis, frozen, and used for in vitro fertilization. The high gain diet increased body weight, average daily gain, and subcutaneous fat thickness compared to the maintenance diet. Sperm of high gain bulls tended to have increased early necrosis and had increased post-thaw acrosome damage compared with maintenance bulls, but diet did not affect sperm motility or morphology. Semen of high gain bulls reduced the percentage of cleaved oocytes that developed to blastocyst stage embryos. Paternal diet had no effect on the number of total or CDX2 positive cells of blastocysts, or blastocysts gene expression for markers associated with developmental capacity. Feeding bulls a high gain diet did not affect sperm morphology or motility, but increased adiposity and reduced the ability of sperm to generate blastocyst stage embryos.