Comparative Studies of Lipid Metabolism in Zebu and British Cattle in a Tropical Environment. I. Plasma Lipid Levels of Grazing Cattle

Abstract

SummaryPlasma lipids have been studied in 77 British (Hereford and Shorthorn), 23 Brahman, 63 Brahman X British, 35 Africander, and 182 Africander X British grazing cattle. Cholesterol, phospholipid, and total lipid levels were significantly (P < 0·001) higher in Zebu breeds than in British breeds. The proportion of cholesterol present in the free state was relatively constant and given by the regression equation:where F = amount of cholesterol present in the free state and T is the total amount of cholesterol.Cholesterol and phospholipid levels were significantly higher (P < 0'01) in females than in males. Age was not a primary factor affecting the plasma lipid levels of adult cattle. Highly repeatable differences between animals within breeds were found in cholesterol and phospholipid levels. Estimates of heritability for cholesterol levels from dam-calf regressions were 34± 11 % and 100± 15% at calf ages of 10 and 22 months respectively.In heifers the triglyceride levels in Africander X British and British breeds were significantly higher (P < O· 01) than in the Africander, Brahman, and Brahman X British breeds. Plasma protein. bound iodine was consistently positively associated with cholesterol levels.Within breeds, animals with high plasma cholesterol carried significantly fewer mature cattle ticks (Boophilus microplus).The phospholipid-cholesterol balance for a given cholesterol level was different in males and females.

Relationship Between Resistance to Boophilus Microplus, Nutritional Status, and Blood Composition in Shorthorn X Hereford Cattle

“…The mean number of ticks per animal and the mean percentage change in body weight during treatment were respectively 1797 and +20·1 in the oil-supplemented group and 1921 and +14·0 in the group receiving lucerne hay alone. However, because of the fluctuations in plasma lipids in animals fed saffiower seeds the results of testing the association noted previously (O'Kelly 1968a) between the elevated plasma lipid levels and tick resistance must be considered inconclusive.…”

“…The techniques for the analyses of plasma lipids have been fully described previously (O'Kelly 1968a) and all values are given as milligrams per 100 ml of plasma except the non· esterified fatty acids which are in microequivalents per litre.…”

“…Francis and Ashton (1967) found an association between the distribution of amylase genes and tick burden which reached significance in Droughtmaster but not in B08 taurus cattle. In a study of grazing Zebu and Shorthorn X Hereford cattle in a tropical environment O'Kelly (1968a) found that within breeds, animals with high plasma cholesterol carried significantly fewer mature cattle tick.…”

Comparative Studies of Lipid Metabolism in Zebu and British Cattle in a Tropical Environment. II. Blood Lipid Levels of Cattle on Different Diets

“…In Part I of this series O'Kelly (1968) reported evidence of breed differences and genetic differences within breeds in plasma cholesterol, phospholipid, and total lipid concentrations in cattle grazing at the National Cattle Breeding Station, Belmont, Rockhampton, Qld. An animal's genetic make-up is expressed only after interaction with the environment and, to define a genetic basis for lipid metabolism, it is necessary therefore to separate the genetic differences from associated differences in diet, disease, and other environmental effects.…”

The Concentrations of Lipids in the Adrenal Cortical Tissue of Genetically Different Types of Cattle

“…Since the concentration of cholesterol is higher in the plasma of Bas indicus than in B. taurus cattle (O'Kelly 1968(O'Kelly , 1972) the question was posed whether a similar difference exists in the concentration of cholesterol in the adrenal glands of these breeds. If so, this may be an important factor in the known superior ability of the B. indicus cattle to adapt to the stresses of a tropical environment.…”