Growth response of cottonwood roots to varied NH4:NO3 ratios in enriched patches

Maximization of short-rotation forest plantation yield requires frequent applications of nutrients, especially nitrogen (N). Whole-plant growth is known to be sensitive to the proportion of ammonium to nitrate (NH4:NO3). However, the extent to which N form affects root growth, branching and morphology is poorly understood, and these variables may have substantial impacts on plant nutrient and water acquisition. We used rooted cuttings of cottonwood (Populus deltoides Bartr. ex Marsh.) to investigate the effect of various NH4:NO3 ratios on root growth in N-enriched patches. A sand culture study with split-root systems was carried out in which 1-3% of the total root system of each cutting was supplied with 2 mM N at NH4:NO3 ratios of 0:100, 20:80, 40:60, 60:40, 80:20 and 100:0 (molar basis), with the rest of the plant supplied with 0 mM N, resulting in the whole plant becoming N deficient. During the experiment, whole-plant growth was unaffected by the treatments. Of the NH4:NO3 ratios tested, greatest total root length, specific root length, and root N concentration of roots in enriched patches occurred in the 20:80 NH4:NO3 treatment. The largest response of roots in enriched patches was third- and fourth-order root production. We conclude that N form has a profound effect on root development and morphology in enriched patches.     

Effect of dry period length on the effect of an intramammary teat sealant on the risk of mastitis in cattle treated with antibiotics at drying off

AIM: The aim of this study was to evaluate, under farm conditions, the use of a teat sealant in addition to whole herd dry cow antibiotic therapy on the risk of clinical mastitis in dairy cattle at pasture, and to evaluate the impact of dry period length on that risk and the impact of the teat sealant on that risk.

METHODS: Dairy cows in three herds which used routine whole herd antibiotic therapy were randomly assigned to receive either treatment with an internal teat sealant (n=322) or no additional treatment (n=313) at drying-off between March and May 2010. All clinical mastitis cases during the dry period and to the end of the subsequent lactation were recorded by farm staff; factors affecting risk of clinical mastitis were then analysed using a Cox proportional hazards model.

RESULTS: Median duration of the dry period was 112 days with >25% of cows having a dry period >130 days. The incidence risk of mastitis during lactation for cows treated with teat sealant was 9.9 (95% CI=6.9–13.7) cases per 100 cows compared with 17.9 (95% CI=13.8–22.6) cases per 100 cows for cows treated with antibiotic alone. The addition of a teat sealant to dry cow antibiotic therapy decreased the risk of clinical mastitis only in the first 33 days after calving (Hazard risk 0.24 (95% CI=0.12–0.48)). Length of dry period did not significantly affect the risk of clinical mastitis, or the effect of adding teat sealant to dry cow antibiotic therapy on the risk of clinical mastitis.

CONCLUSIONS: In these herds where, based on the mastitis history, whole herd antibiotic therapy had been recommended, the use of a teat sealant significantly reduced the risk of clinical mastitis. This effect was limited to the first 33 days after calving; subsequently there was no significant effect of treatment. There was no effect of dry period length on risk of clinical mastitis, nor any significant interaction with treatment.

CLINICAL RELEVANCE: Combination therapy with teat sealant and antibiotic was effective under New Zealand conditions in herds using whole herd antibiotic treatment at drying off. Teat sealant reduced risk of clinical mastitis in cattle with dry periods substantially longer than 100 days, and there was no evidence that this effect changed as dry period length increased.     

Primary anconeal fracture in a boxer

A 14-month-old speyed female Boxer was presented with acute non-weight-bearing lameness in the right forelimb. Radiography revealed separation of the anconeal process, which was thence surgically removed. Histological examination of the anconeal process confirmed a primary fracture. Isolated unilateral anconeal process fracture in the dog is rare and this report includes histopathological findings of a primary anconeal fracture.     

化药防治羊硬蜱病试验

将1150只感染有草原革蜱和森林革蜱的绵羊分为3个组,分别为驱蜱项圈组（400只）、灭蜱灵组（550只）和对照组（200只）。项圈组在治疗后0、7、15、28、45、60、75、95天,羊只平均染蜱数分别为10.3、0.9、0.7、0.3、0.4、0.5、0.5、0.1只;而对照组分别为10.2、9.2、13.6、10、9.2、6.4、8.8、4.2只。灭蜱灵组在治疗后0、18、33、48、68天,羊只平均染蜱数分别为9.8、0.5、0.7、0.5、0.1只,而对照组分别为10、9.2、6.4、8.8、4.2只,表明两个防治组保护效果均较好。     

几种旋毛虫抗原PAPS诊断液的效果比较试验

将几种旋毛虫抗原以同一浓度（0.6mg/mL）与PAPS微球交联,制成诊断试剂,进行旋毛虫阳性血清检测效果比较试验。结果显示,成虫、成虫ES、新生幼虫、肌幼虫B峰4川抗原均出现非特异性反应,而肌幼虫、肌幼虫ES、肌幼虫A峰抗原具有很高的敏感性,三者效价均达1:640。将此3种抗原所制得的诊断试剂对几种寄生虫阳性血清进行交叉试验,显示肌幼虫ES抗原对血吸虫、锥虫、弓形虫、肺吸虫、牛肝片吸虫、羊肝片吸虫阳性血清均不出现交叉反应,而肌幼虫A峰抗原、肌幼虫抗原对牛、羊肝片吸虫均出现交叉反应,对其他血清则不出现。表明肌幼虫ES抗原效果最佳,特异性最好,有很高的应用价值。     

免疫调节剂与抗球虫药联合应用的抗球虫效果

为探讨免疫调节剂对鸡球虫病的免疫反应调节作用,设计并进行了免疫调节剂与抗球虫药合用的效果的研究。试验结果以抗球虫指数的测定来判定抗球虫药与免疫调节剂合用的效果。结果表明,免疫调节剂与抗球虫药合用状态下,抗球虫指数检测显示免疫调节剂卡介苗和黄芪多糖可明显提高抗球虫指数、改善球虫感染鸡的临床症、提高增重速度等,为控制球虫病提供了新的途径。     

四种剂型阿维菌素对肉用犬疥螨病的疗效试验

四种剂型阿维菌素 (粉剂、片剂、注射剂、浇注剂 )以 0 .2 mg/kg剂量治疗肉用犬疥螨病 ,间隔 7天重复用药 1次 ,治愈率均为 1 0 0 %,且安全无副作用。     

樟树种源/家系苗期性状变异分析

为了解樟树遗传变异的来源和规律,进行了樟树苗期种源／家系两水平试验研究。结果表明,樟树的遗传变异存在于种源和家系两个层次。樟树苗高、枝下高、冻害性状在种源层次的变异远大于家系层次的变异,地径则相反。方差分析表明,樟树苗期种源间在苗高、地径、枝下高、冻害性状上有极显著差异;家系之间在苗高、地径、冻害性状上有极显著差异,在枝下高性状上无显著差异,种源内大多数家系间各性状的差异达不到显著水平。苗高、枝下高、冻害各性状值,高于富阳种源（Ｃｋ）的家系分别有１２５、９５、８８、１０８个,低于富阳种源（Ｃｋ）的分别有５６、８６、９３、７３个。苗高与种源纬度显著负相关,与年均温、１月均温、绝对低温显著相关;冻害与纬度极显著负相关,与年均温、１月均温、绝对低温显著相关;枝下高与纬度显著相关,与年均温、１月均温、绝对低温显著负相关;苗高与冻害极显著相关,与地径显著相关。