安普霉素对仔猪内分泌的调控作用及血液生化指示的影响

采用单因子试验设计 ,28日龄大长北三元杂交断奶仔猪72头随机分为3组 ,研究饲料中添加不同剂量的安普霉素 (0、20、90mg/kg)对仔猪内分泌的调控作用及血液生化指标的影响。试验期为4周。结果表明 :仔猪日粮中添加90mg/kg的安普霉素可促进机体与生长有关的内分泌活动 ,提高内源激素 (生长激素、胰岛素、甲状腺激素T3)水平 (P<0.05),从而促进肌肉蛋白沉积 ;并具有显著降低血液中氨、尿素氮含量和提高血糖水平的作用 (P<0.05) ,表明安普霉素对仔猪具有增加氮沉积 ,促进蛋白质合成、抑制蛋白质分解的作用     

金霉素与赖氨酸和蛋氨酸交互作用研究

采用3×2×2因子饲养试验和2×2×2因子代谢试验,研究金霉素与赖氨酸和蛋氨酸的交互作用对肉仔鸡生产性能的影响,及金霉素对两种氨基酸代谢的影响。金霉素在饲料中添加150 mg/kg时,对0-3周肉仔鸡具有显著的促生长作用（P<0.01）;并显著提高肉仔鸡的饲料采食量和饲料转化率（P<0.01）,促进氮沉积（P<0.01）。对4-6周肉仔鸡的生产性能无显著影响（P>0.05）;金霉素、赖氨酸和蛋氨酸存在显著的互作关系（P<0.05）。金霉素的促生长效果受饲料中赖氨酸和蛋氨酸含量的影响,当日粮中赖氨酸水平为1.3％,蛋氨酸水平为0.6％时,肉仔鸡的生长性能最高。金霉素对赖氨酸的利用率没有显著影响（P>0.05）,对蛋氨酸和胱氨酸的表观利用率具有显著抑制作用（P<0.05）。研究结果表明持续低剂量金霉素与蛋氨酸和赖氨酸具有交互作用,这种互作关系影响彼此对肉仔鸡生产性能的作用效果,金霉素具有提高肉仔鸡赖氨酸需要量的作用。     

The possible role of methionine in the detoxification of faba bean (Vicia faba L.) tannins in chick diets

1. A metabolism trial was designed to investigate the role of methionine as a specific detoxifying agent of the condensed tannins present in faba beans (Vicia faba L.).

2. A 5 x 5 factorial approach was employed where 5 concentrations of dietary methionine were obtained (ranging from 3.9 to 12.15 g/kg diet dry matter) by the addition of DL‐methionine, and 5 concentrations of condensed tannins (ranging from 0.5 to 19.7 g/kg diet dry matter) by altering the ratio of tannin‐free and tannin‐containing faba bean hulls added to a basal diet.

3. The intake of condensed tannins had a significant, depressive effect on apparent available nitrogen (P< 0.001) and nitrogen corrected apparent metabolisable energy (AME_n ) (P< 0.001). There was no interaction between methionine and tannin (P>0.05). Thus the depressive effect of tannin was independent of methionine levels in the diet.

4. Methionine does not act as a specific detoxifier of faba bean condensed tannins.     

Some currently available insecticides and their comparative efficacy on louse-infested, long-woolled sheep

The comparative efficacy of 13 of the sheep dips currently registered in New Zealand was investigated using sheep infested with the louse Bovicola ovis and carrying wool which was about 10 cm long at the shoulder. With the exception of one synthetic pyrethroid pour-on formulation, all products were able to effect a significant reduction in louse populations, relative to untreated controls, for 37 days after treatment. Only four products proved capable of eradicating lice and preventing their re-establishment up to 37 days after treatment. Variations in manufacturers' recommendations relating to the length of wool at dipping, and mode of application of dips are discussed in relation to the results.     

An evaluation of two cypermethrin-based pour-on formulations on sheep infested with the biting louse, Bovicola ovis

Two synthetic pyrethroid (cypermethrin) based pour-on insecticide formulations, with high cis/trans isomer ratios (80:20) but differing in their respective active ingredient concentrations and solvent component(s), were applied to sheep infested with the biting-louse, Bovicola ovis. All treated sheep were penned with louse-infested sheep 9,12 and 15 weeks after the insecticide was applied. The 2% cypermethrin formulation achieved a higher level of control than the 1.25% cypermethrin formulation at each challenge interval when applied 12 weeks after shearing. The 2% cypermethrin formulation provided 97-100% control of lice from 4 to 16 weeks after application on sheep shorn 6 or 12 weeks prior to treatment. The 1.25% cypermethrin formulation provided 85% control of lice 4 weeks after application on sheep shorn 12 weeks prior to treatment, the level of control increasing to a maximum of 100% by week 9, and declining thereafter. The 2% cypermethrin formulation may provide a better level of control in long-woolled sheep than 1.25% cypermethrin, by compensating for the diluent effect of lipid.     

Effects of Confluent, Roscovitine Treatment and Serum Starvation on the Cell-cycle Synchronization of Bovine Foetal Fibroblasts

The present study was designed to examine the effects of cell-cycle synchronization protocols, such as confluent, roscovitine treatment and serum starvation, in bovine foetal fibroblasts on synchronization accuracy at G0/G1, viability, apoptosis, necrosis and ploidy for use as a nuclei donor. The cells in 5-10 passages were randomly allocated into three treated groups. Cells were cultured either in Dulbecco's modified Eagle's medium (DMEM) + 10% foetal bovine serum (FBS) until 90% confluent (group 1, confluent), in DMEM + 10% FBS + 30 microM roscovitine for 12 h (group 2, roscovitine), or in DMEM + 0.5% FBS for 5 days (group 3, serum starvation). Most of the cells (>80%) in all groups were arrested at the G0/G1 stage. Although the rates did not differ, cells in group 1 showed an increased cell population arrested at the G0/G1 phase. Significantly (p < 0.05) higher rates of apoptosis occurred in group 3 than in group 1 and 2 (10% vs 6% and 6%, respectively). No differences in chromosomal abnormality were observed among groups. However, by increasing the number of cell culture passages up to 15, significantly (p < 0.05) higher chromosomal abnormality was observed than in 5 and 10 passages (39% vs 28% and 23%, respectively) in group 1. The results clearly indicated that bovine foetal fibroblasts could be effectively synchronized at G0/G1 stages by all the three different treatments, confluent, roscovitine and serum starvation. However, cells in confluent showed reduced apoptosis and necrosis when they underwent 5-10 passages, exhibiting increased percentage of cells with stable chromosome diversity. Hence, cells in confluent merit further studies before they could be used as nuclear donors.