Influence of prepubertal dietary regimen on mammary growth of Holstein heifers.
One hundred-sixteen Holstein heifers (mean BW, 175 kg) were randomly assigned to diets of alfalfa silage or corn silage and were fed to gain approximately 725 or 950 g/d in order to study the influence of prepubertal diet and rate of gain on mammary growth and milk production. Blood was collected before puberty for hormone determination, and 8 heifers per group were killed at puberty for evaluation of tissue variables. Serum growth hormone was reduced, and IGF-I was increased, in the group of heifers reared at a high rate of gain on the corn silage diet. Accompanying the decline in growth hormone, total mammary parenchymal DNA and RNA was reduced in heifers reared at a high rate of gain on the corn silage diet. Mammary parenchyma in heifers of the latter group contained a greater volume of adipocytes and a lower volume of epithelial cells than did mammary parenchyma in heifers of other groups. Data are consistent with previous investigations that showed a deleterious effect of prepubertal rapid weight gain on mammogenesis when accompanied by excess body fat deposition. However, this effect did not cause a decline in subsequent milk production.
Capuco
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AV
Livestock and Poultry Science Institute, US Department of Agriculture, ARS, Beltsville, MD 20705, USA.
Smith
J J
JJ
Waldo
D R
DR
Rexroad
C E
CE
D017667:Adipocytes / Q000166:cytology; D000818:Animals; D001835:Body Weight; D002417:Cattle / Q000502:physiology*; D002452:Cell Count; D004032:Diet; D004847:Epithelial Cells; D005260:Female; D013006:Growth Hormone / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007774:Lactation; D008321:Mammary Glands, Animal / Q000166:cytology / Q000254:growth & development*; D000455:Medicago sativa; D011388:Prolactin / Q000097:blood; D011897:Random Allocation; D012741:Sexual Maturation; D012820:Silage; D003313:Zea mays
D007334:Insulin-Like Growth Factor I; D011388:Prolactin; D013006:Growth Hormone