Development and evaluation of a model for prediction of fecal and urinary nitrogen excretions in cattle

The reduction of nitrogen (N) excretion in animal production is crucial in intensive farming systems particularly in the developed countries. In this study, a model to predict N excretion in cattle was developed based on existing feeding standards and evaluated using independent N balance experiments for Holstein steers and lactating cows and Japanese Black (JB) steers. Although model predictions for fecal and urinary N excretions appeared to be close to observed values in plot figures, statistical analysis showed that the model tended to over-predict both fecal and urinary N excretions, especially in Holstein lactating cows. This was because body weight changes of cows during lactation period were not considered in the model due to the lack of information (i.e., body weight gain or loss) available in the experimental data for evaluation. There were large mean bias and small line bias for urinary N prediction, but reverse results were obtained for fecal N prediction. The largest mean square prediction errors for both N excretions were due to random variation in all cases. When all data were pooled (combined), the accuracy for predictions for fecal N excretion was considerably high (r² = 0.94), indicating that the model may predict fecal N excretion beyond breeds, sexes and physiological states (growing and lactating). More information and accumulated data will be required to predict urinary N excretion under a wide range of genotype and environmental situation.     

3H—萱草根素在小鼠体内吸收分布,排泄和代谢的初步观察

本文应用放射性同位素示综技术,初步观察了~3H-萱草根素在小鼠体内吸收分布、排泄和代谢的全过程。~3H-萱草根素口服后0.5小时,小鼠血液中放射性即达到高峰,并以低浓度维持96小时以上;其随血液循环分布于各组织器官,以胃肠组织含量最高,其次是肝脏和脾脏。萱草根素有蓄积性;一次给药和以同等剂量分次(每天一次,三天)投药后的相同时间,各组织中~3H-萱草根素的含量差异不显著。主要排泄途径是粪便,其次是尿液。经有机溶剂处理后的尿液分为水、脂二相,其放射性测量和薄板层析放射自显影结果均表明:~3H-萱草根素在体内经过代谢后结构发生了变化,从尿液中排出的不是萱草根素原形,而是其代谢产物。     

A preliminary study of the role of ducks in the transmission of Newcastle disease virus to in-contact rural free-range chickens

The role of ducks in the transmission of Newcastle disease virus (NDV) to free-range village chicken was investigated experimentally. Newcastle disease (ND) seronegative ducklings reared in a pen were infected oronasally with velogenic NDV of intracerebral pathogenicity index (ICPI) 1.8 isolated from outbreaks in village chickens in Uganda. A first group of 3-week-old ND seronegative chicks was mixed with the ducks and they were kept together for 7 days. Both ducks and chicks were observed for ND clinical signs and any mortality, and they were bled and their sera were tested for ND antibodies by haemagglutination inhibition (HI) test. The chicks were removed, euthanized and examined for any ND lesions, while the ducks were transferred to a fresh pen and a second group of chicks was introduced and observed and treated as above. The ducks and the chicks tested positive for ND antibodies 7 days post infection and contact, respectively, but showed no clinical signs, post-mortem lesions or mortality. The mean ND antibody titre of the second group of chicks was lower than for the first group. This study has shown that although ducks can be infected with velogenic NDV, they do not show clinical signs but are able to transmit NDV to in-contact chicks. Further investigations are needed of the lack of clinical signs in the in-contact chicks and how long the ducks remain infective.     

福寿螺对水体环境与水体微生物的影响

福寿螺为首批入侵中国的16种危害最大的外来物种之一,它适应性强、食性广泛、繁殖速度快,近年来对稻田等水体生态系统造成了较大危害。本研究通过室内养殖试验,探讨了福寿螺对水体环境,以及福寿螺养殖液对水体放线菌和酵母菌的影响效应。结果发现,与对照处理相比,养殖福寿螺的水体呈弱酸性,水体的浊度、总氮、总磷等含量随着养殖时间的延长而增大。同时,福寿螺养殖液使水体中总细菌的数量显著增加,对酵母菌的生长有促进效应,但不同密度福寿螺的养殖液对酵母菌和放线菌的生长均无显著差异。本研究表明,福寿螺入侵可能会导致水体富营养化和水质恶化等环境问题。这些研究结果可为福寿螺入侵的生态危害及风险评价提供参考依据。     

INGESTIONANDEXCRETIONOFSEVERALANTIBACTERIALDRUGSBYTHEBRINESHRIMP（ARTEMIAPARTHENOGENETICA）1．TOXICITYT

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The effect of dicyandiamide on rumen and blood metabolites,diet digestibility and urinary excretion

The excretion of urine by dairy cows provides a source of nitrogen (N) to pasture. Excess N from urine patches can be lost through nitrate (NO₃⁻) leaching and nitrous oxide (N₂O) emissions. Dicyandiamide (DCD) inhibits nitrification in the soil and is usually applied to the pasture by blanket spreading the entire field. This study assessed the potential of pulse-dosing cows with DCD so that the DCD will be excreted in the urine and deposited directly onto the urine patches. The objective of this study was to measure the recovery of DCD in urine and faeces and to assess the effects of DCD on rumen and blood metabolites and diet digestibility. Eight non-lactating Holstein–Friesian dairy cows fitted with rumen cannulae were assigned to two treatments in a Latin square design over two periods. The two treatments used were (1) control (CON) consisting of 500 ml distilled water and (2) DCD consisting of 0.1 g DCD per kg liveweight (LW) suspended in 500 ml distilled water. Both treatments were pulse-dosed into the rumen daily for 6 days with half the volume dosed in the morning and the remainder in the afternoon. The administration of DCD into the rumen had no effect on rumen and blood metabolites, and diet digestibility when compared to the control treatment, as all were not significantly different from the control treatment and were within the normal biological range. During 6 days of dosing with DCD the average recovery of the dosed DCD in urine was 82.3%, with a further 2.1% recovered in the faeces. No DCD was recovered in the urine and faeces 10 days following the cessation of dosing. These results could provide the basis for a novel mitigation strategy to reduce NO₃⁻ leaching and N₂O emissions from urine patches in grazed grassland.     

Identification of factors associated with increased excretion of foot-and-mouth disease virus

We investigated which variables possibly influence the amount of foot-and-mouth disease virus (FMDV) shed in secretions and excretions by FMDV infected animals, as it is likely that the amount of FMDV shed is related to transmission risk. First, in a separate analysis of laboratory data, we showed that the total amount of FMDV in secretions and excretions from infected animals is highly correlated with maximum titres of FMDV. Next, we collected data from 32 published scientific articles in which FMDV infection experiments were described. The maximum titres of FMDV reported in different secretions and excretions (the response variable) and the experimental conditions in which they occurred (the explanatory variables), were recorded in a database and analyzed using multivariate regression models with and without random effects. In both types of models, maximum titres of FMDV were significantly (p < 0.05) associated with types of secretions and excretions, animal species, stage of the disease and days post infection. These results can be used to prioritize biosecurity measures in contingency plans.     

Effect of dietary inclusion of benzoic acid on mineral balance in growing pigs

The objective of this study was to determine the effect of dietary inclusion of benzoic acid on utilization of the macrominerals Ca, P, Mg, K, Na, and Cl in growing pigs. Eighteen barrows, initial BW of 28 ± 1.7 kg, were assigned to 3 diets: a basal diet based on barley, wheat, soybean meal, corn, and field pea and formulated to contain 9.31 MJ NE kg^− 1 and 8.84 g^− 1 kg standardized ileal digestible lysine, or the basal diet containing 10 or 20 g kg^− 1 benzoic acid by replacing tapioca starch. The pigs were fed the experimental diets a rate of 2.7 times the maintenance requirement for ME for 21 days. Faeces and urine were collected quantitatively from days 11 to 21, and blood and plasma was collected on days 1, 10, and 21. On day 21, the pigs were killed and the left femur was removed. Benzoic acid linearly decreased (P = 0.001) the urine pH from 7.32 to 5.32, and quadratically increased (P < 0.05) blood pH on day 21. Benzoic acid linearly increased (P < 0.05) the apparent total tract digestibility (ATTD) of Ca, P, and Na from 65 to 72%, 46 to 55%, and 78 to 90%, respectively, linearly decreased (P < 0.05) the ATTD of Cl from 94 to 93%, and did not affect the ATTD of Mg and K. Benzoic acid linearly increased (P < 0.05) the retention of Ca, P, and K from 58 to 67%, 46 to 54%, and 31 to 38%, respectively, linearly decreased (P < 0.05) the retention of Na and Cl from 57 to 48% and 75 to 44%, respectively, and did not affect retention of Mg. On day 21, benzoic acid linearly increased (P = 0.001) plasma P and quadratically increased (P < 0.05) plasma K or tended to increase (P = 0.05) plasma Na. Benzoic acid linearly reduced (P < 0.05) the concentration of ash in femur but not the amount of ash, reduced (P < 0.05) the concentration of Ca and Cl in femur ash, and linearly increased (P < 0.05) the concentration of P in femur ash. In summary, benzoic acid increased the utilization of dietary Ca, P, and K, did not affect the utilization of dietary Mg, and reduced the utilization of dietary Na and Cl. During swine feed formulation, effects of benzoic acid on macromineral utilization should be considered to ensure that macromineral requirements are met and not exceeded following benzoic acid supplementation.     

卤虫对几种抗菌药物的摄入与排出Ⅱ水不溶性药物的摄入与排出

本文研究了卤虫（Ａｒｔｅｍｉａｐａｒｔｈｅｎｏｇｅｎｅｔｉｃａ）对下述３种药物的摄入与排出：磺胺嘧啶（ＳＤ）、土霉素（ＯＴＣ）及无味红霉素（ＥＲＹ－Ｅｓ）。当摄取药物１小时（药物用海水配制成混悬液）时，卤虫（幼体或成体）消化道充满了白色的药物颗粒；经测定此时初孵无节幼体内药物含量为１７μｇ／１０只，成体内为２０３μｇ／只（体长６５ｍｍ）及３６２μｇ／只（体长９２ｍｍ）。药物颗粒大小、摄取时间及卤虫体长对药物摄入量有明显影响。但卤虫对３种药物的摄取量无明显差异。当将载药卤虫放入海水中３小时时，仅有５０％的药物被排出。     

菲律宾蛤仔和栉孔扇贝的呼吸与排泄研究

对菲律之后人蛤仔和栉孔扇贝的呼吸与排泄进行了实验研究。结果表明：温度和贝体重对两种贝类的耗氧率的氨排泄率都有明显的影响，且两者间存在着交互作用。菲律宾蛤仔的耗氧率（Ｑｏ，ｍｇ／ｇ／ｈ）和氨排泄率（ＱＮ，μｇ／ｇ／ｈ）与温度（Ｔ，℃）（Ｗ，ｇ）存在下列关系：Ｑｏ＝０．３０７Ｗ＾－０．７３８ １．００４＾Ｔ，ＱＮ＝７．８４１Ｗ＾－０．９１９ ０．９９０＾Ｔ；栉孔扇贝的耗氧率和氨排泄率与温度、湿重存在下