Effects of varying levels of dietary free gossypol in whole cotton seed on physiological responses of growing-fattening lambs

Abstract

Effects of increasing concentrations of free gossypol in diets containing up to 30% whole cottonseed on blood metabolites were studied using 32 Karagouniko male lambs in a 4 × 3 factorial arrangement with treatments of four whole cottonseed levels and three times of sampling. The diets used were isocaloric (12.5–13.1 MJ metabolisable energy kg−1 dry matter) with 163–186 g crude protein kg−1 dry matter containing 0%, 5–10%, 10–20% and 15–30% whole cottonseed and were fed ad libitum for 54 days. Blood samples were taken at the beginning, middle and end of the experiment. The blood parameters examined were: haematocrit, haemoglobin, mean corpuscular haemoglobin concentration, erythrocyte sedimentation rate, plasma glucose, urea, total protein, albumin and globulin concentrations and serum total and free cholesterol, cholesterol esters and inorganic K concentrations. In addition, the serum enzyme activities of glutamate pyruvate transaminase, γ-glutamyl transpeptidase and lactate dehydrogenase, as indicative of liver and heart muscle damage, and the concentrations of the major elements Ca, Mg and K and also of the trace elements Fe, Cu and Zn in liver, kidneys and heart of slaughtered lambs were estimated. This study was also made to determine the effect of whole cottonseed diets on the accumulation of free gossypol in some organs of growing lambs. Most of the blood components evaluated were affected by the diet fed. Blood haematocrit and erythrocyte sedimentation rate were higher at the beginning of the experiment, but haemoglobin and mean corpuscular haemoglobin concentrations were higher at day 28 of the experimental period; plasma total protein, urea, albumin and globulin concentrations and also serum total and free cholesterol and inorganic K concentrations were higher at day 54 of the experiment. The serum enzyme activities of glutamate pyruvate transaminase, γ-glutamyl transpeptidase and lactate dehydrogenase were all higher at day 54 of the experimental period. However, there were significant differences between treatments and between times of sampling in the three enzyme activities measured. Liver, kidneys and heart examination showed significant differences for all organs in NPN, fat, fat/protein ratio and the major elements Ca, Mg and K among the four treatments. However, of the trace elements examined, differences were significant for Fe in liver, Cu in heart and Zn in liver and heart. The greatest free gossypol accumulation was observed, as expected, in liver, followed by kidneys and lastly by heart. There was an indication of possible gossypol toxicity in these growing lambs as a result of the marked elevations of the activity of lactate dehydrogenase and possibly of the increase in plasma urea concentration. © 1999 Society of Chemical Industry