1. Evaluating the economic costs-benefits of a particular selection or breeding decision. By following the flow of genes through a population as a result of a particular breeding decision, it is possible to estimate the net economic cost-benefits of that breeding decision. For example, when looking at the value of the use of a particular bull in a dairy herd, we can note that each replacement h...

The concentration of ivermectin in the serum of Hereford heifers treated with a single Ivomec SR bolus reached a maximum of 8.8 +/- 0.9 ppb at 2 wk post-treatment. The single bolus treatment resulted in <10% mortality of adult horn flies feeding on the blood of the treated animals over the 21-wk trial. Bioassays of the manure from treated cattle showed complete inhibition of development of imma...

Heritability of 2-yr-old heifer calving difficulty score was estimated in nine purebred and three composite populations with a total of 5,986 calving difficulty scores from 520 sires and 388 maternal grandsires. Estimates were 0.43 for direct (calf) genetic effects and 0.23 for maternal (heifer) genetic effects. The correlation between direct and maternal effects was -0.26. Direct effects were ...

Four Hereford X Angus heifers (379 +/- 11 kg) with indwelling hepatic portal vein, iliac artery and mesenteric vein catheters were used in a switchback design to measure net portal absorption of leucine at two levels of energy intake, 130 and 260 kcal metabolizable energy.(kg.75.d)-1. Nine hourly measurements were made through two consecutive 4-h feeding periods on each heifer at each intake le...

We developed a precise, remote (up to 300m) observation system to record animal location and behaviour that requires no animal handling or disruption of the normal environment. Our system, combining a survey laser and a laptop, also allows recording of observed animal behaviour from seconds to hours, with accuracy of 1m or better. Up to one individual per second can be located, which supports d...

This study was carried out to determine the prevalence and type of renal lesions in cattle that were slaughtered at the Ghaem (Shahriar) and Ziaran (Ghazvin) abattoirs. A total number of 405 clinically normal cattle were randomly selected and renal samples were taken for histopathological study. The cattle were divided into two groups according to sex, and female groups were divided into two ag...