Protein supplementation to pregnant heifers and grazing management effects on cow diet quality

Two experiments were conducted in Trial 1 to determine effects of summer grazing date and fall grazing pressure on the CP content and in vitro organic matter digestibility (IVOMD) of the diets of cows grazing fall range in the Nebraska Sandhills. In both experiments, pastures were grazed in June, July, or deferred from summer grazing. The pastures were then grazed the following fall at various levels of grazing pressure, and diets were collected by esophageally fistulated cows as forage was removed. In the first experiment, pastures grazed in June had higher diet CP in the fall than pastures grazed in July. Diet CP and IVOMD declined quadratically with increased grazing pressure. In the second experiment, pastures deferred from summer grazing had higher CP content than pastures grazed in June or July. Fall diet CP and IVOMD did not decline with increased grazing pressure.; Trial 2 was conducted to determine the effects of supplementing pregnant heifers (March-calving) grazing winter range to meet metabolizable protein (MP) requirements versus CP requirements on forage intake and production traits, and to determine effects of hay supplementation during the last two months of gestation. Heifer body weight and body condition score change during the winter were not markedly different between MP and CP supplemented heifers, but hay supplementation reduced body weight and condition score loss. Grazed forage intake was not affected by treatment, but intake declined from November through February.; Trial 3 was conducted to determine effects of supplementing pregnant heifers to meet MP or CP requirements on 2-yr-old pregnancy and profitability. March calving heifers were supplemented from September to February at two locations across 2 yr. Supplementing to meet MP requirements improved pregnancy and profitability in three of four situations.; Grazing system affected fall diet nutrient content. Grazed forage intake of March-calving heifers declined over the winter, and supplementing heifers to meed MP requirements during gestation increased 2-yr-old pregnancy.