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K. J. Stewart
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Summary. The present observations of wild gorillas demonstrate that lactation has a major influence on birth spacing. The frequency of suckling declined as infants matured, from >1/h during the first year to about 1/2 h by 30–36 months when mothers usually resumed sexual cycling. In contrast, the length of suckling bouts remained relatively constant throughout lactation, averaging between 2·6 and 3·2 min per bout. Within infant age categories, suckling frequencies of ≤0·5 bouts/h were associated with mothers who had resumed cycling, whereas higher frequencies were associated with mothers who were still anoestrous. These results complement those obtained from studies of breast-feeding in humans, and support the suggestion that the frequency of suckling is a critical factor in the contraceptive effects of lactation.

Keywords: gorilla; lactational anoestrus; interbirth intervals; suckling frequency

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Zachary K Seekford Department of Animal Sciences, University of Florida, Gainesville, Florida, USA

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Dylan B Davis Department of Animal and Dairy Science, The University of Georgia, Athens, Georgia, USA

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Mackenzie J Dickson Department of Animal Sciences, University of Florida, Gainesville, Florida, USA

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Lucas Melo Gonçlaves Federal University of Uberlandia, Uberlandia, Minas Gerias, Brazil

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Samir Burato São Paulo State University, Botucatu, São Paulo, Brazil

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Matthew P Holton Department of Animal and Dairy Science, The University of Georgia, Athens, Georgia, USA

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Julie Gordon College of Veterinary Medicine, The University of Georgia, Athens, Georgia, USA

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Ky G Pohler Department of Animal Science, Texas A&M University, College Station, Texas, USA

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G Cliff Lamb Department of Animal Science, Texas A&M University, College Station, Texas, USA

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Timothy D Pringle Department of Animal and Dairy Science, The University of Georgia, Athens, Georgia, USA

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Robert L Stewart Department of Animal and Dairy Science, The University of Georgia, Athens, Georgia, USA

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Maria S Ferrer College of Veterinary Medicine, The University of Georgia, Athens, Georgia, USA

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Pedro L P Fontes Department of Animal and Dairy Science, The University of Georgia, Athens, Georgia, USA

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John J Bromfield Department of Animal Sciences, University of Florida, Gainesville, Florida, USA

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In brief

Paternal high-gain diet reduces blastocyst development following in vitro fertilization and embryo culture but does not affect gene expression or cellular allocation of resultant blastocysts.

Abstract

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 days 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.

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