Haematological and tissue abnormalities in chicks caused by acute and subclinical folate deficiency

Folic acid requirements of broilers

1. Dietary folic acid requirements of broilers were studied in three experiments using wheat- and maize-based practical diets. Requirements were assessed on the basis of performance and metabolic criteria. 2. Growth and food conversion efficiencies were optimised with supplements of 1.5 mg folic acid/kg added to basal mash starter diets. The dietary folic acid requirement of broilers was estimated to be in the range of 1.7 to 2.0 mg/kg. 3. Red blood cell phosphoribosylpyrophosphate concentrations and dihydrofolate reductase activities did not show consistent changes over the range of dietary folate concentrations studied but plasma folate concentrations responded markedly to dietary folate supplementation. 4. Adding choline to diets in amounts greater than the normal requirement did not spare the requirement for folic acid. 5. It is suggested that minimum folic acid supplements for pelleted practical diets should be in the order of 2.5 to 3 mg/kg.

Haematology and histopathology of seven-week-old broilers after early food restriction

The haematology and histopathology of seven-week-old broilers were examined after periods of early food restriction, for six, 10 or 14 days from six days old. After several weeks on an ad libitum diet the birds failed to compensate for the weight lost during early food restriction. Immediately after the periods of food restriction, the birds demonstrated significantly increased heterophil/lymphocyte ratios, reduced eosinophils and slightly raised basophil counts. At seven weeks old, a significant reduction was seen in red and white blood cells and thrombocyte numbers together with significant increases in mean cell haemoglobin and mean cell volume. The haematological profile demonstrated a macrocytic normochromic anaemia caused possibly by a folic acid deficiency as a result of the food restriction. Histopathological lesions were seen in the heart, lungs and liver from birds on all diets but there were more lesions the longer the food had been restricted. Lung disease was more marked where there was inadequate ventilation. Cartilaginous and osseous lung nodules were significantly fewer after food restriction. It was postulated that the increase in pathological lesions in the food-restricted birds may be associated with a stress response.

Relation between some folate-dependent metabolic pathways and dietary folate content in chicks

Responses of several folate-metabolizing pathways to dietary folic acid were studied in 2-week-old chicks. Oxidation of a histidine load to carbon dioxide was impaired in folate-deficient chicks. There was a curvilinear relation between oxidation and dietary folate, and maximum oxidation occurred with 2 mg supplemental folic acid/kg. Hepatic activities of glutamic acid formiminotransferase (EC 2.1.2.5) and glycine N-methyltransferase (EC 2.1.1.20) were not affected significantly (P greater than 0.05) by dietary folic acid. The activity of dihydrofolate reductase (EC 1.5.1.3) in erythrocytes was elevated in folate-deficient chicks. These studies show that the activities of two folate-dependent pathways can be used as biochemical criteria of folate status in chicks.