猪日粮中的非抗生素饲料添加剂(一)

非抗生素饲料添加剂有助于提高猪的免疫系统,并降低断奶和其他环境应激带来的负面影响。最常用的饲料添加剂包括酸化剂、锌铜、益生菌、直接饲喂微生物、酵母类产品、核苷酸和植物提取物。研究表明添加药理水平的锌铜、特定酸化剂和部分植物提取物可以改善猪的性能或提高其免疫功能。使用益生菌、直接饲喂微生物、酵母类产品、核苷酸也有可能对猪的性能产生有利影响,但因研究结果缺乏一致性,因此仍需进一步研究。     

Oxidant‐Antioxidant Status in the Blood of Horses with Symptomatic Recurrent Airway Obstruction (RAO)

Background

Systemic oxidative stress in horses with recurrent airway obstruction (RAO) is poorly characterized.

Objectives

The goal of this study was to investigate whether equine RAO is associated with systemic disturbances in the oxidant‐antioxidant equilibrium.

Animals

Seven healthy horses and 7 horses with symptomatic RAO.

Methods

A prospective study. Healthy and RAO‐affected horses were exposed to a 48‐hour challenge with moldy hay and straw to induce clinical exacerbation of RAO. Venous blood was collected and the activities of the superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR) in equine erythrocyte lysates were measured. The concentration of thiobarbituric acid‐reactive substances (TBARSs) was assessed both in erythrocyte lysates and in plasma.

Results

A significant increase in the activities of GPx and SOD was detected in RAO‐affected horses compared with the control animals. There was no significant difference between groups in terms of the erythrocyte lysate activities of CAT, GR, or TBARs or the plasma concentration of TBARs.

Conclusion and Clinical Importance

Our results support the hypothesis that RAO in horses is associated with systemic oxidative stress. Future studies are needed to assess whether horses suffering from RAO can benefit from antioxidant supplementation.     

Relative resistance of potato cultivars to bacterial wilt

Fifty-one potato cultivars were evaluated for reaction to infection byPseudomonas solanacearum Sm. under high disease pressure in a field plot near Tifton, Georgia during the spring of 1978 and 1979. Plots were infested by clipping beds of thickly seeded tomato plants with a rotary mower contaminated with the wilt baterium in 1975, 1976, 1977 and 1978. The plants were incorporated into the soil following disease development. In addition to the use of infested soil, one stem on each potato plant was inoculated in late May by cutting with a knife blade dipped in a bacterial suspension. Most of the cultivars evaluated were highly susceptible to bacterial wilt. Ontario was the only cultivar highly resistant to the disease, with only 1% and 8% dead or dying plants in 1978 and 1979, respectively. Based on tuber infection, Ontario and Snowchip were the most resistant, with 9% and 14% infection, respectively, in 1978 and both 4% in 1979. Saco, Green Mountain and Sebago also showed some resistance.     

Engineering needs for potato production from true seed

Potatoes grown from true potato seed (TPS) are generally small and nonuniform in size and shape, compared to the ones produced conventionally from seed tubers. Potato production from TPS would be considerably less expensive than from seed tubers because of the negligible storage and handling costs of the TPS. Potato production from TPS would therefore have the greatest potential in the developing countries. In developed countries, this production method would have some potential in commercial production as well as in home gardening. Research related to the TPS potato production has been mostly directed toward investigating suitable cultural practices, screening breeding lines for higher yield and warm climate adaptability, weed control in the field, and other similar production areas. Research concerning mechanization of TPS potato production has been limited. Engineering input to the TPS potato production, handling and storage needs considerable attention to develop practical and economical practices. This paper highlights some research areas which the authors believe are worth investigating. Engineering research that is conducted at the Coastal Plain Experiment Station related to the TPS potato production has been outlined along with future plans.     

Effect of storage temperature and duration on quality and survival of potato transplants

Potato transplants (Solanum tuberosum) were harvested and stored at 1.7, 7.2, 12.8, 15.6 and 18.3°C between 4 and 8 days. The transplants were evaluated after storage for leaf color and drop, wilt, tuberization, and stolonization. After transplanting, the plants were evaluated for survival. At 1.7 and 7.2°C storage, the leaves were greener with less drop than at the higher temperatures. During storage above 7.2°C, the development of tubers and stolons continued. Plant survival was generally higher at 1.7, 7.2 and 12.8°C than at 15.6 and 18.3°C.     

To jump or not to jump? Strategies employed by leisure and sport horses

Show jumping is one of the most popular equestrian disciplines although strategic jumping per se is seldom used by free-living horses when negotiating obstacles that they might otherwise avoid. To establish if horses are naturally motivated to jump, we examined horses in a free-choice situation when negotiating various obstacles under test conditions. Eighteen leisure horses (LHs) and 16 sport horses (SHs) participated in a number of 2-choice tests. First, horses were presented with 2 optional routes during a “free-choice test” to reach a food stimulus. The choices were a shorter route (over an obstacle) or a longer route (around the obstacle). During 8 consecutive trials, the horses encountered an increase in obstacle height on every second trial as follows: 0, 20, 35, and 50 cm. In the “ridden test” after an initial conditioning period, the horses were tested with a Y-maze formation during 3 consecutive trials, where one element of the maze contained an obstacle arm (OA). The horses walked or trotted over the obstacle most frequently (59.9%) and jumped the obstacle in only 10.7% of the cases. For both the LH and SH groups, the horses' motivation to traverse the obstacle decreased as the obstacle height increased and only 44.1% of horses actually negotiated the 50-cm obstacle as compared with the 20-cm obstacle (85.3%). The LH group preferred to go around the obstacle significantly more often than the SH group (24 trials, 16.7% vs. 9 trials, 7.0%, for SH and LH, respectively; χ² = 6.81, N = 33, P = 0.0090). The LH group used a jumping strategy to clear the obstacle far less frequently (6 trials, 4.2%) than the SH group (23 trials, 18.0%; χ² = 9.96, N = 29, P = 0.0023). In the Y-maze trials, the LH group exhibited preference (40 per 54 trials, 74.1%; χ² = 12.5, P < 0.0001), and the SH group failed to exhibit any preference (20 per 48 trials; χ² = 1.33, P = 0.3123). There was no evidence of any correlation between the motivation to clear the obstacle and total number of OA choices in either the LH group (r_s = 0.13, P = 0.9594) or the SH group (r_s = ?0.25, P = 0.3492). The findings from the present study indicate that SHs are motivated and willing to jump obstacles more often than are LHs under similar conditions. However, the apparent reluctance of the horses overall to continue jumping as the obstacle height increases suggests that, in general, many horses could easily encounter excessive demands (overfacing) in sport. This issue should be carefully monitored in terms of equine training, competition, and welfare.