Physiological attributes as possible selection criteria for milk production 2. Plasma insulin, tri-iodothyronine and thyroxine in bulls

Abstract

Insulin, thyroxine and tri-iodothyronine concentrations were measured in samples of blood from 175 Friesian bulls, aged between 2 and 7 years, which were being progeny-tested for milk production. Least squares regression coefficients were estimated for these hormone levels on time of day and time after feed at sampling and age of bull. Correlations between hormone levels and Improved Contemporary Comparisons of the bull, a measure of his daughters' milk production, did not differ significantly from zero, suggesting that simple spot estimates of levels of these hormones in bulls would not supply useful predictors of daughters' production.

Thyroid hormones and daily gain in cattle. Relationships between plasma total thyroxine, free thyroxine, triiodothyronine and average daily gain during the first year of life in Belgian blue and Friesian cattle

“…In routine use, repeatabilities of our duplicate T 4 and T 3 analyses were similar to those obtained by Osmond, Carr, Hinks, Land and Hill (1981). Since variation in live-weight gain was small, significance of the correlations must necessarily depend on the precision and accuracy of the hormone assays.…”

Growth, hormonal and metabolic response of post-pubertal entire male cattle to trenbolone acetate and hexoestrol

“…Insulin (experiment 1) was assayed by a method similar to that of Osmond, Carr, Hinks, Land and Hill (1981). Ox insulin (24-5 international units per mg; Boots Ltd, Nottingham) was used as standard and 125 Ilabelled insulin (Amersham International Ltd, Amersham) as tracer.…”

Physiological attributes as possible selection criteria for milk production 3. Plasma hormone concentrations and metabolite and hormonal responses to changes in energy equilibrium

“…The concentration of insulin in the samples of plasma was determined by double antibody radioimmunoassay as described by Osmond et al (1981). The following assays were conducted, the samples for each experiment being measured in a group of assays.…”

“…Despite the apparent genetic association between thyroid activity and milk production the correlation between the concentration of T, and T 4 in a single sample of peripheral plasma of an adult bull and the bull's ICC is very low (T,, r = 0-06; T 4 , r = -0-12; Osmond et al, 1981). Further, the use of radioactive compounds to measure degradation rates is not always desired.…”

“…To h o w e v e r < common to both sexes so that, if overcome this sex limitation, cattle breeders t h e y w e r e e x P r e s s e d i n t h e male, and if that progeny test potential replacement bulls e x P r e s s i o n could be measured, it would be before bringing them into general use, and in P o s s i b l e t o P r e d i c t a b u l l ' s 8 e n e t i c m e r i t f o r Britain the Milk Marketing Board of England m i l k Production from measurements taken and Wales evaluates bulls according to their d i r e c t l v o n t h a t b u l L I n t e r m s o f t h e Improved Contemporary Comparison (ICC) e f f i c i e n c y of the breeding programme, computed from first lactation records using a measurements taken on calves would be Best Linear Unbiassed Prediction (BLUP) P r e f e r a b l e to measurements taken on mature bulls. Thyroxine degradation rate is, however, measured after the introduction of 125 I, a procedure which is not appropriate for commercial cattle, and studies of bulls awaiting progeny test indicate that individual estimates of the tonic concentration of thyroxine in peripheral plasma are not correlated with breeding value (Osmond, Carr, Hinks, Land and Hill, 1981). Sri Lanka.…”