Effects of altering dietary cation-anion difference on calcium and energy metabolism in peripartum cows.

Our objective was to determine the effects of varying dietary cation-anion differences (DCAD: meq[(Na + K) - (Cl + S)]/100 g of dry matter) in prepartum diets on Ca, energy, and endocrine status prepartum and postpartum. Holstein cows (n = 21) and heifers (n = 34) were fed diets with varying amounts of CaCl2, CaSO4, and MgSO4 to achieve a DCAD of +15 (control), 0, or -15 meq/100 g of dry matter for the last 24 d before expected calving. Dietary Ca concentration was increased (by CaCO3 supplementation) with decreasing DCAD.

Effects of diet and injection of bovine somatotropin on prepubertal growth and first-lactation milk yields of Holstein cows.

To determine effects of rapid prepubertal growth on first-lactation milk production, Holstein heifers were randomly assigned to one of three treatments. Thirty-five heifers were fed a standard diet to meet NRC recommendations and produce 0.8 kg of body weight (BW) gain/d (standard).

Insemination of Holstein heifers at a preset time after estrous cycle synchronization using progesterone and prostaglandin.

Two experiments were conducted to study estrous cycle control regimens that combine progesterone administration via an intravaginal device ( PRID ) with a single injection of prostaglandin F2 alpha (PG). In Exp. I, 242 Holstein heifers were assigned randomly to one of three treatment groups at 14 to 18 mo of age.

Use of artificial light and day length to alter the life cycles of mink.

Mink (Mustela vison) that had been raised on a farm were abruptly changed from ambient light at 42 degrees N latitude to an artificial light regimen corresponding to 45 degrees S latitude. The study was continued for 3 years and included three generations of mink. Animals were raised in a light-controlled room with partial temperature control that kept the temperatures between -3 and 26 C.

Advanced implantation in mink (Mustela vison) treated with medroxyprogesterone acetate during early embryonic diapause.

Adult and pubertal female mink mated on 4 March were administered 2.5 mg medroxyprogesterone acetate (MPA) or control vehicle on 9-11 March. Pregnancies were shorter (P less than 0.