Effect of biotin and niacin on lipid content of livers in the laying hen

Response of laying hens to supplemental niacin

Two experiments were conducted to investigate the effect of supplemental niacin on laying hen performance and liver fat and egg cholesterol content. In Experiment 1, 16 replicate groups of four adjacently caged birds were fed corn and soybean meal diets calculated to contain 22, 44, 66, or 132 mg supplemental niacin/kg (23.2, 38.7, 57.0, and 143 mg/kg niacin by analysis). Egg production, egg weight, feed intake, and eggshell quality were assessed each 28 days through a 364-day trial period. After 280 days, cholesterol content on three eggs per replicate was measured. At the end of the study, one bird per replicate was killed for subjective scoring of liver fat content. In Experiment 2, 24 birds from the control treatment (22 mg/kg supplemental niacin) of Experiment 1 were retained and fed for a subsequent 28-day period. Over this time, eight birds were each fed diets containing 22, 522, or 1,022 mg/kg supplemental niacin. Egg cholesterol content was measured in eggs collected on the last 3 days of the study. In Experiment 1, birds fed 66 or 132 mg/kg supplemental niacin/kg produced more eggs (P less than .05) than birds fed 22mg/kg. Niacin supplementation affected shell quality (P less than .05). Dietary niacin level had no effect on egg cholesterol content of liver lipid evaluation. In Experiment 2, supplementary niacin levels up to 1,022 mg/kg, which more closely stimulates therapeutic levels used for humans, again failed to affect egg cholesterol content.

The effects of increased levels of niacin supplementation on growth rate and carcass composition of broiler chickens

Four experiments were conducted to examine the response of broiler chickens to different levels of niacin. Practical-type diets, calculated to contain from 20.7 to 23.7 mg niacin per kg from intact ingredients, were fortified with a complete vitamin mixture which provided 33 mg supplemental niacin per kg of diet, in excess of the National Research Council (1977) suggested requirement of 27 mg per kg through 6 weeks of age. A niacinamide supplement was used to provide additional levels of 0, 33, or 66 mg per kg. Diets differed in content of added fat and energy levels in two of the experiments and in the presence or absence of animal protein sources in two others. The addition of niacinamide at 33 and 66 mg per kg to a diet already supplemented with 33 mg per kg from a complete vitamin premix, calculated to exceed the present NRC suggested requirement, resulted in improved body weight gains with sex differences noted in some experiments. Feed utilization was improved in some studies. There was no effect on the amount of abdominal fat or carcass dressing percentage. The results of these studies indicate that the modern rapidly growing broiler chick may require niacin levels greater than those generally recommended by the National Research Council (1977), which are based largely on studies where performance was considerably lower than obtained with the modern strains of broilers.

Reduction of hepatic lipid deposition in laying hens by dietary selenium-yeast interaction

Experiments were conducted to study the effect of chromiun and selenium on liver lipid deposition and incidence of liver hemorrhage in caged layers. Commercial strains of layers were fed ad libitum equicaloric and isonitrogenous diets. Corn-torula dried yeast diets containing added selenium (.1 microgram/g) with or without supplementary chromium (10 microgram/g) significantly reduced total liver lipid and liver hemorrhage. The effects of protein source (soybean meal vs. yeast) and selenium were separated in a factorial experiment which showed that the hepatic lipid response to selenium results from an interaction of selenium with an unidentified factor in torula yeast. The addition of selenium to diets with each protein source significantly elevated glutathione peroxidase (GSHPx) activity. Inclusion of 5% brewers yeast in the corn-soy diet or vitamin E (50 IU/kg) to the corn-torula dried yeast reduced liver lipid similar to that seen in birds fed the torula-yeast diet containing .1 microgram Se/g. Comparison of oral glucose tolerance of birds fed corn-soy and corn-soy brewers yeast diets showed no significant difference. None of the dietary treatments significantly altered body weight, egg production, egg weight, or feed consumption. The results indicate that the metabolic role of selenium in relation to its role in hepatic lipid metabolism is mediated through an interaction with a dietary factor(s) present in yeast.

Liver lipid accumulation and performance of hens as affected by cage density and initial body weight

Hens housed in individual cages (25 46 cm.) laid significantly more eggs, consumed significantly more feed and had significantly larger livers with a higher lipid content than hens housed three to a cage in two experiments. Body weight gain was significantly higher for individually housed birds in experiment 1, but not in experiment 2. No difference was observed in mean egg weight or kg. feed per dozen eggs. In experiment 2 hens housed two to a cage laid slightly fewer eggs and accumulated slightly less liver fat but the differences were not significantly different fromthose housed individually. Hens socially dominant in three bird pens had higher liver fat accumulation than hens lower on the peck order but liver fat accumulation for the dominant hens still averaged less than hens housed either two or one per cage. Comparison of two strains in experiment 1 revealed a significant difference in rate of egg production and feed efficiency but no difference in liver fat accumulation. Pullets placed in four body weight classes prior to the start of the experiment did not differ significantly in liver fat accumulation per unit of body weight or percentof dry matter of the liver at the end of the experiment. Rate of egg production and feed efficiency were also not significantly different among the body weight classes.