Total Daily Feed Intake Research Articles

Production and Physiological Responses of Dairy Cows to Varying Dietary Potassium During Heat Stress

Objectives were to study influences of heat stress and dietary potassium content on production and physiological responses of 8 Jersey and 10 Holstein cows blocked by breed and assigned randomly to no shade or shade environments. Each cow received a different dietary potassium treatment (.66, 1.08, and 1.64% of dry matter) in each of three 30-day periods. Rates of potassium loss from skin were almost five times greater for no shade as for shade cows during the hottest part of the day (1300 to 1500h). Overall, cows with no shade ate 56% less during the daytime (0800 to 1600h), 19% more during nighttime (1600 to 0800h), and 13% less total feed than cows with shade. Interactions of environment and breed with dietary potassium treatment suggest differences in feed intake and milk yield responses to increasing dietary potassium content. Total daily feed intake and milk yield of cows with no shade responded in curvilinear fashion to increasing dietary potassium, whereas responses in shade were small. Largest responses in no shade were as dietary potassium increased from .66 to 1.08%. Milk yield of Holsteins increased with increasing dietary potassium, but yield of Jerseys did not. Combined effects of elevated potassium loss from skin and reduced potassium and dry matter intake during heat stress suggested that lactating dairy cows may benefit from supplemental potassium.

Evaluation of a role for prolactin in growth and the photoperiod-induced growth response in sheep.

An experiment was conducted to determine whether prolactin is involved in growth or in mediating the photoperiod-induced growth response in sheep. Prolactin was manipulated by im injections of 2-Br-alpha-ergocryptine (CB154) or sc injections of ovine prolactin (oPRL) and by two light:dark regimens (16L:8D and 8L:16D). Fifty-six wether lambs (two/pen) were allotted to one of four treatments for a 9-wk growth study. Treatments were: 1) 16L:8D, placebo injections; 2) 16L:8D, CB154 injections; 3) 8L:16D, placebo injections and 4) 8L:16D, oPRL injections. Daily injections of CB154 (.1 mg/kg body weight.75), oPRL (.8 mg/kg body weight.75) or placebo were in 1 ml volume. Animals were fed ad libitum a complete mixed diet. At wk 8, plasma prolactin concentrations at 3 to 6 h postinjection were 214, 3, 90 and 228 ng/ml for treatments 1, 2, 3 and 4, respectively. Pattern of feed intake, measured at 8-h intervals for a 48-h period, was affected by photoperiod. Animals exposed to the 16L:8D photoperiod consumed 40.0, 42.4 and 17.6% of their total daily feed intake during the first 8 h of light, second 8 h of light and 8 h dark interval, respectively. Those exposed to the 8L:16D regimen consumed 55.2, 22.2 and 22.6% during their 8-h light interval, first 8 h of dark and second 8 h of dark, respectively. Both cumulative gain and feed intake were greater in 16L:8D control animals than in those animals receiving CB154.(ABSTRACT TRUNCATED AT 250 WORDS)

Induced Fatty Liver-Hemorrhagic Syndrome (FLHS) and Accumulation of Hepatic Lipid in Force-Fed Laying Chickens

Weights of the liver components (water, lipid and non-lipid dry weight) were increased in adult female chickens proportional to the amounts of feed force-fed for 21 days at daily amounts up to 50 percent more than ad libitum fed control birds. Despite being force-fed, all force-fed chickens consumed feed, ad libitum, at amounts inversely proportional to the rate of force-feeding.Hepatic hemorrhages characteristic of Fatty Liver-Hemorrhagic Syndrome (FLHS) were induced in these force-fed birds and the hemorrhagic score, in particular, as well as, the hemorrhagic incidence were directly related to the total daily feed intake and to hepatic fatty metamorphosis. The excellent reproducibility of the experimental data from three experiments using gradient doses of force-feeding suggests that the force-feeding technique is adaptable to an assay procedure.

Effects of Dietary Protein and Changes in Energy Levels on the Laying House Performance of Egg Production Stocks

IMPROVEMENTS in breeding, feeding, housing, and disease control have greatly reduced the pounds of feed required for a dozen two-ounce eggs. Less of the total daily feed intake is now required for maintenance. With these changes, readjustment of the dietary nutrient balance is required if maximum feed efficiency is to be obtained. Protein and energy sources make up the greatest bulk and cost of laying rations. The present study compares the effects of 13, 15, and 17% dietary protein on the major economic performance traits of egg-type chickens, and the effects of dietary energy increases after three and five months of production respectively on these same traits. The authors have observed in previous experiments that birds peak in production during the third or fourth month of lay and at this same time tend to lose body weight. The purpose of increasing the energy level of the diets in the present …