Yolk and serum cholesterol and production traits, as affected by incorporating a supraoptimal amount of copper in the diet of the leghorn hen.

1. An experiment was conducted to investigate the possibility of lowering the yolk cholesterol of the egg by supplementing the diet with supraoptimal amounts of copper (50, 150 or 250 mg/kg) as sulphate or acetate. 2. A significant reduction in egg production and a negative effect on food conversion was found when 250 mg/kg of copper was added compared to the control (no added copper). Acetate seemed significantly less harmful in both cases. 3. A significant linear reduction was found in plasma and yolk cholesterol (20% and 14%) and in plasma and yolk triglycerides (24% and 30%) as the dietary copper content was increased from 0 to 250 mg/kg. 4. Regardless of type or quantity of copper, cholesterol and lipids were decreased linearly as birds remained longer on the treatments. A significant interaction between quantity and period showed a greater reduction at a later time. 5. If slightly lower egg production can be accepted, the addition of 250 mg/kg copper might be beneficial in reducing the cholesterol content of the yolk.

Lack of effect of hormones and inducers of intracellular messengers on plasminogen activator production by bovine embryos in vitro.

Several hormones and inducers of intracellular messengers, known to affect plasminogen-activator (PA) production in other systems, were investigated for putative effects on bovine embryos. Day 8 embryos were cultured for 5 days in a humidified atmosphere of 5% CO2 in air at 37 degrees C in media containing different concentrations of progesterone, oestradiol, dexamethasone, retinoic acid, dibutyryl cyclic AMP (dbcAMP) and phorbol myristate acetate (PMA). At intervals of 24 h, the medium was recovered for PA analysis and overall embryonic diameter was measured. While none of the hormones and agents tested affected PA production (P > 0.05), dimethyl sulfoxide, which was used to dissolve PMA, inhibited PA production during the first 72 h of culture (P < 0.05). PA production was affected by duration of culture (P < 0.05). Concentrations of plasminogen activator in the media were low during the first 48 h, had increased after 72 and 96 h in culture, and either remained high or decreased slightly toward the end of the culture period. With the exceptions of dbcAMP and PMA, the hormones tested in this study did not affect embryonic size. Dibutyryl cAMP caused a progressive decrease in embryonic diameter. PMA resulted in embryo death at high concentrations but at lower concentrations it enhanced overall embryonic diameter throughout the time of culture (P < 0.05). These results suggest that cultured bovine embryos produce PA in a fixed, time-dependent manner, independent of exogenous hormonal regulation.

Animal fat effects on nutrient utilization.

Laying hens were employed to study the effects of carrier on the true metabolizable energy (TME) of tallow using corn, milo, soybean meal, wheat bran, and dehydrated alfalfa meal with tallow at 0, 2, 4, or 6%. In addition to bomb calorimetry measurements on feed and excreta samples, tallow TME values were calculated from absorbability data. Estimates of TME for tallow varied with carrier feedstuff from 7.19 kcal/g in soybean meal to 13.62 kcal/g when wheat bran was fed. For the corn, milo, and soybean meal series only fat retentions were significantly affected by tallow supplementation. Calculated tallow absorbabilities were 101.8% with corn, 95.8% with milo, and 107.3% with soybean meal. Highest tallow TME values were obtained with wheat bran and dehydrated alfalfa meal, apparently due to increase protein retention from wheat bran and to both improved protein retention and starch absorption with dehydrated alfalfa meal.