日粮中添加植酸酶和锌对断奶仔猪生产性能及其组织锌浓度的影响

通过三个试验测定日粮中植酸酶、过量的锌及两者共同对哺乳仔猪的影响。在所有的试验中,每个处理组有5～7栏,每栏有6～7头猪,当日粮中添加植酸酶时,则日粮中钙和有效磷的水平降低0.1%,锌是通过氧化锌的形式添加,试验日粮中含锌水平均为127mg/kg,本试验的周期为19～21d。在试验1中,试验采用2×3因子试验设计,两个水平的植酸酶(即0和500植酸酶单位/kg)和三水平过量的锌(即0,1000和2000mg/kg)。仔猪(5.7kg和18日龄)被随机分配采食以上日粮。试验表明,平均日增重(ADG)和平均日采食量(ADFI)随日粮中锌含量的增加而线性增加,第一阶段为(P=0.01～0.06),第二阶段为(P=0.02～0.09),整个试验阶段为(P=0.01～0.02),肉料比(G∶F)也随日粮锌含量的增加而线性增加,但仅限于第一阶段(P=0.01)。当仔猪采食1000或2000mg/kg锌时的同时添加植酸酶可降低第二阶段ADG(锌与植酸酶互作;P=0.10),但对整个试验周期内ADFI没有影响(P=0.27～0.62),并可降低第二阶段G∶F(P=0.01),及整个试验周期内G∶F(P=0.07)。随着日粮锌添加量的增加,血浆中锌含量也随之增加(Zn2,P=0.01),并且不受植酸酶添加的影响(P=0.70)。在试验2中,试验采用2×2因子试验设计,两个水平的植酸酶(即0和500植酸酶单位/kg)和两水平过量的锌(即0和2000mg/kg)。仔猪(5.2kg和18日龄)被随机分配采食以上日粮。试验表明,日粮中锌含量的增加可使第二阶段ADG和肉料比增加(P=0.02～0.09)和整个试验阶段的ADG和G∶F增加(P=0.07～0.08),但对第一阶段ADG和整个试验阶段ADFI的变化没有影响。植酸酶的添加可增加第二阶段ADG(P=0.06)和G∶F(P=0.01)。当仔猪采食2000mg/kgZn和植酸酶时,G∶F值最大(锌与植酸酶互作;P=0.01)。骨(20日龄)中锌和血浆锌(7和20日龄)随着日粮中锌的添加量的增加而增加(P=0.01),但不受植酸酶添加的影响(P=0.51～0.90)。在试验3中,仔猪(5.7kg和19日龄)被随机分配采食添加500植酸酶单位/kg的植酸酶或不添加植酸酶的基础日粮或添加500植酸酶单位/kg的植酸酶或不添加植酸酶且钙和有效磷含量降低0.10%的基础日粮。试验表明,植酸酶的添加对仔猪生产性能没有影响(P=0.21～0.81)。降低钙和有效磷的含量,可降低整个试验周期内ADG,ADFI和G∶F(P=0.02～0.08)。这些试验结果表明,日粮中添加过量的锌可增加ADG及血浆和骨中锌的浓度。日粮中植酸酶对血浆和骨中锌的浓度没有影响。     

不同处理方法对美国截叶胡枝子种子发芽的影响

截叶胡枝子(Lespedezacunecta)是原产于亚洲东部的一种多年生的豆科植物,在我国南方地区野生分布很广。它具有耐瘠、耐旱、耐酸、耐热、固土能力强、适应性广等特性,在国外也颇受重视。我国于1983年从美国引种,通过对其生物学和生态学特性、经济性状和栽培技术研究证明,引进的美国截叶胡枝子在人工栽培条件下,表现出良好的经济性状,是南方草地改良的希望种子。但是在生产中,由于其硬实的存在,使得种子的发芽率很低,往往造成出苗困难和草地建植缓慢,甚至出现严重缺苗断垄的现象,直接影响田间产量,限制了它的进一步推广应用。试验采用不同处…     

不同处理方法对美国截叶胡枝子种子发芽的影响

美国截叶胡枝子的硬实率很高,发芽率只有17.3%。经过种子预处理,如采用不同温度下浸种、98%浓硫酸浸泡、机械破皮和机械破皮结合热水浸种等处理,结果表明,机械破皮后用60℃热水浸种处理的效果最好,发芽势和发芽率分别达到64.0%和74.3%;其次是机械破皮,平均发芽率达到50%;浓硫酸浸种可以显著提高种子发芽势,浓硫酸浸种5min效果最好,发芽率达到44.7%;热水浸种的处理效果不佳,最好的90℃热水浸种处理发芽率也仅有26.7%。     

Association of brook trout and Oncorhynchus spp. with large wood jams in a Lake Superior tributary in a northern old‐growth watershed

Wood in streams functions as fish habitat, but relationships between fish abundance (or size) and large wood in streams are not consistent. One possible reason for variable relationships between fish and wood in streams is that the association of fish with wood habitat may depend on ecological context such as large‐scale geomorphology. We studied the relationship between salmonid assemblages and large wood jams (LWJ) in four settings that differed geomorphically at the scale of the stream corridor along a tributary to Lake Superior in old‐growth conifer–hardwood forest in northern Michigan. The focal fish species of this study were brook trout (Salvelinus fontinalis), which were wild in the stream. Relocation efforts for coaster brook trout (an adfluvial life history variant of brook trout) were ongoing in the study stream. We measured fish abundance and length in pairs of pools of similar size and substrate, but varying in the presence of LWJ; this allowed us to evaluate associations of fish simply with the presence of LWJ rather than with other channel or flow‐shaping functions of LWJ. The length of Oncorhynchus spp. and young introduced brook trout was not strongly correlated with LWJ presence; however, the presence of LWJ in pools was positively correlated with larger wild brook trout. We also found that the correspondence of LWJ with the abundance of salmonids appears to be moderated by the presence of alternative habitat in this relatively natural, old‐growth forest stream.     

The role of antibody in protection against African swine fever virus

Intraperitoneal immunization of pigs with anti-African swine fever virus (ASFV) antibody protected them against the effects of challenge with ASFV. This protection, which was exemplified by a reduction in pyrexia and viraemia plus an increased survival time, appeared to be mediated through the effects of complement-dependent antibody-mediated cytotoxicity (CDAC) or antibody dependent cell mediated cytotoxicity (ADCC). Experiments suggested that the reduction in viraemia was associated with complement lysis whereas protection was conferred by ADCC.     

Gastric emptying of liquids in the dog: serial test meal and modified emptying-time techniques

A serial test meal technique was used in the dog to evaluate the gastric emptying of a liquid test meal. On separate days, a phenol red test meal was placed in the stomach and completely aspirated at different times. A composite representation of the gastric emptying pattern was obtained for each dog, and a set of normative data was generated. Three emptying determinants (emptying time, half-life, and starting index) were calculated. The basic pattern of canine gastric emptying was linear and declined exponentially or as a function of the square root of the gastric volume. A modified emptying-time technique (METT) correlated well with the serial test meal and a set of normative values was determined. The METT was performed by aspirating test meal from the stomach 30 minutes after instillation. The METT was a simple and inexpensive technique that could be performed in 1 short testing period. With the METT, the half-life of gastric emptying was calculated, using the log of the percentage of retention of test meal; gastric emptying time was calculated, using the square root of the percentage of retention of test meal. Acetylpromazine was shown not to alter gastric emptying of a liquid test meal.     

Extraocular myositis in the dog.

Extraocular myositis is a rare condition in the dog and is poorly reported in the peer-reviewed veterinary literature. This case series and review are designed to be of value to those veterinary ophthalmologists seeking to investigate the disease further and also to veterinarians outside the specialty, for whom this may be their first introduction to the disease.     

Contribution of White Clover Varieties in High-Productivity Systems under Grazing and Cutting

Two medium leaf size varieties of white clover (Trifolium repens L.) were grown in mixture with a range of grass species and varieties in a field experiment conducted over 4 years. The clovers were grown singly or as a blend in swards with a tetraploid perennial ryegrass (Lolium perenne L.), a diploid Italian ryegrass (Lolium multiflorum L.) or tetraploid hybrids between these two species (Lolium x boucheanum Kunth). These grasses were also grown in monoculture. Swards were managed in a regime involving two periods of sheep grazing, two periods of cattle grazing and a silage cut in the same year for 4 years. The objectives of this experiment were 3‐fold: (1) to examine the yield and persistency of white clover in highly productive systems with modern perennial, hybrid and Italian ryegrasses; (2) to compare the performance of white clover varieties grown singly in mixture with grasses with their performance together as a blend, and (3) to examine the persistency of new Italian ryegrass varieties, exemplified by AberComo. The clover content of the sward remained high throughout the experiment, with a mean of 31 % overall. Differences in clover yield between plots were largely attributable to the effects of companion grasses. Total yields were very similar in plots containing different clover varieties and in plots where these varieties had been grown singly or as a blend. Grass yields in mixture were greater than those in monoculture but showed similar relative rankings. The diploid Italian ryegrass variety AberComo showed an unexpectedly high yield in the 4th year of the experiment. The implications of these results for strategies for productive, sustainable agriculture using modern white clover and ryegrass varieties are discussed.