Induction of lactation by two techniques: success rate, milk composition, estrogen and progesterone in serum and milk, and ovarian effects

Colostrogenesis: Role and Mechanism of the Bovine Fc Receptor of the Neonate (FcRn)

Colostrogenesis is a separate and unique phase of mammary epithelial cell activity occurring in the weeks before parturition and rather abruptly ending after birth in the bovine. It has been the focus of research to define what controls this process and how it produces high concentrations of specific biologically active components important for the neonate. In this review we consider colostrum composition and focus upon components that appear in first milked colostrum in concentrations exceeding that in blood serum. The Fc Receptor of the Neonate (FcRn) is recognized as the major immunoglobulin G (IgG) and albumin binding protein that accounts for the proteins' long half-lives. We integrate the action of the pinocytotic (fluid phase) uptake of extracellular components and merge them with FcRn in sorting endosomes. We define and explore the means of binding, sorting, and the transcytotic delivery of IgG1 while recycling IgG2 and albumin. We consider the means of releasing the ligands from the receptor within the endosome and describe a new secretion mechanism of cargo release into colostrum without the appearance of FcRn itself in colostrum. We integrate the insulin-like growth factor family, some of which are highly concentrated bioactive components of colostrum, with the mechanisms related to FcRn endosome action. In addition to secretion, we highlight the recent findings of a role of the FcRn in phagocytosis and antigen presentation and relate its significant and abrupt change in cellular location after parturition to a role in the prevention and resistance to mastitis infections.

Artificial induction of lactation in cattle: Effect of modified treatments on milk yield, fertility, and hormones in blood plasma and milk

Holsteins were divided into groups CON and IL, each with six dry cows and six heifers. Group CON calved in mid-summer when group IL was treated (kg body weight per day) with (a) progesterone (P; .25 mg) and estradiol-17beta (Ebeta), either .05 mg or .10 mg, for 7 days; (b) continued Ebeta at one-third the initial rate until udders were engorged; (c) then 12 injections (8-hr intervals) of TRH (each 200 mug) or saline; and (d) GnRH during lactation. Milk yield was not affected by Ebeta dose rate, TRH or GnRH. GnRH luteinized the persistent ovarian follicles in group IL, and pregnancy rates were 80% and 83% in groups IL and CON, respectively. Large differences (P < .01) between groups IL and CON were observed in plasma prolactin (IL-low), insulin (IL-high) and growth hormone (IL-low) wherein insulin was correlated (P < .01) negatively with milk yield between days 7 to 49 of lactation. Milk concentrations of P, Ebeta, estrone and estradiol-17alpha in group IL were no higher (P > .10) 14 days after the last injection of P or Ebeta than in group CON or in milk from the herd's bulk tank. The steroids were lowest in milk and plasma from ovariectomized cows. It was hypothesized that high insulin, as well as low prolactin and growth hormone, may contribute to inferior induced lactations.

Mammary growth pattern in goats during pregnancy and lactation

Nine groups of five dairy goats from four breeds, with each breed represented at least once in each group, were in our experiment to measure mammary gland growth. Groups were virgins, days 90 to 100 pregnancy, 5 days prepartum (145 days pregnancy), 1 or 2 days prepartum, and 1 or 2, 5, 10, 15, and 30 days in lactation. Virgins were 19 mo old while all others had one pregnancy and lactation prior to experiment. Indices of mammary growth included untrimmed and trimmed wet weights of udders, dried fat-free tissue weights, deoxyribonucleic acid and ribonucleic acid contents. Each index was in a regression equation best to describe the pattern of mammary growth. These included linear, quadratic, cubic, and exponential model Y = AebX in which Y was the index of mammary growth and X was the day of pregnancy. Total deoxyribonucleic acid was the best index of mammary growth with a correlation of .95 in the exponential model. The predictive equation for total deoxyribonucleic acid in milligram was Y = 167e.019X on a daily basis, and the rate of growth on a monthly basis was .57. Mammary growth in goats continued into early lactation, peaking at day 5. Ribonucleic acid doubled on the day after parturition, which reflected the rapid increase in protein synthesis at this time.