Effect of pasture allowance and supplementation with maize silage and concentrates differing in crude protein concentration on milk production and nitrogen excretion by dairy cows

Sixty cows (40 multiparous and 20 primiparous) averaging 140 days in milk (DIM) were assigned to five treatments to evaluate the effect of pasture allowance and supplements of a) maize silage b) high crude protein concentrate and, c) low crude protein concentrate on milk production and nitrogen (N) excretion. Two of the treatments (HG and LG) were offered herbage only (allowances of 20 and 15 kg dry matter (DM) per cow/day, respectively) while the remaining three treatments were offered a herbage allowance of 15 kg DM per cow/day plus 4 kg DM per cow/day of maize silage (M), a high CP concentrate (CP concentration of 194 g/kg DM) (HC), or citrus pulp (CP concentration of 69 g/kg DM) (LC). Total DM intake (DMI) was similar for HG, M, HC, and LC but was lower for LG (15.2 kg DM per cow/day) than HC (17.4 kg DM per cow/day). The reduction in pasture DMI per kg of supplement DM ingested was 0.44, 0.45, and 0.54 kg for cows offered maize silage, high CP concentrate, and low CP concentrate, respectively. Milk yield was greater for the supplemented treatments (23.7–24.7 kg/day) than for LG (20.7 kg/day) but not for HG (23.2 kg/day). Milk fat concentration was greater for HC (35.3 g/kg) than for HG, M, and LC but not greater than LG, while milk protein concentration was greater for HG (34.8 g/kg) than for LG and HC but not greater than M and LC. The greatest levels of N and PDIN intake were recorded for HG (662 and 2502 g/day) and HC (654 and 2506 g/day) which were greater than LC but not greater than LG and M. Treatment HC recorded the highest PDIE intake (1743 g/day) which was greater than LG, M and LC but not greater than HG. Output of N in milk was greater on HC (134 g/day) than on LG but was not greater than on HG, M, and LC. Faecal N excretion was greater on HG (171 g/day) than on all other treatments while estimated urinary N excretion was greater on HG and HC than LC (320 g/day). Treatment LC had a higher proportion of N output in milk (0.23) than treatment LG but not higher than HG, M and HC treatments. Urinary N expressed as a proportion of total N excretion was lower for HG (0.68) than all other treatments. The results of this study show that there is a large response in milk production to supplementing cows on a restricted grass allowance and that cows offered low CP supplements had similar levels of production to those offered high CP supplements. Nitrogen utilisation was improved by offering supplements of lower CP content.     

Ammonia dynamics in relation to hatching in Atlantic halibut (Hippoglossus hippoglossus L.)

Total ammonia content (T_Amm) and excretion (J_Amm), and ionic content (K⁺, Na⁺, Cl_-) have been studied in embryos and yolk-sac larvae of Atlantic halibut (Hippoglossus hippoglossus L.) maintained in darkness (6 °C and 34% S) or in light (light-arrested, nonon-hatching embryos). The T_Amm of the eggs increased from 250-300 nmol ind^-1 during the first 5-10 days post fertilization (dPF) to 400-500 nmol ind^-1 at the time of natural hatching in darkness. T_Amm did not start to decrease before 2-5 days after hatch, and yolk-sac larvae had a higher T_Amm compared to the light-arrested embryos of the same age and batch. J_Amm increased exponentially rom about 0.05 nmol ind^-1 h^-1 at 10 dPF to about 3 nmol ind^-1 h^-1 at hatch. Embryos undergoing hatching showed a significantly higher J_Amm than non-hatching, light-arrested embryos of the same age. The content of K+ in distilled water rinsed eggs declined from about 0.85 µmol ind^-1 at 2-4 dPF to about 0.15 µmol ind^-1 at hatch, while that of Cl^- remained constant at about t 0.85 µmol in^-1, and that of Na⁺ increased slowly from 0.10 to 0.20 µmol ind^-1 . Based on the measured ions, there was an anionic deficit in the egg, especially during the first week of development. When exposed to increased ambient total ammonia (0-27 mM NH4Cl), no mortality occurred, and no significant increase was found in the T_Amm of the Atlantic halibut egg before 9.2 dPF despite an estimated large inward diffusion gradient for the un-ionized ammonia species (NH₃). The delayed release of T_Amm comp ared to embryos and yolk-sac larvae of other marine teleosts, may relate to the deep-water spawning of the Atlantic halibut, and the buoyancy regulation of the yolk-sac larvae.     

Effect of salinity on survival, growth, oxygen consumption and ammonia-N excretion of juvenile whiteleg shrimp, Litopenaeus vannamei

In this study, we tested the lower salinity tolerance of juvenile shrimps (Litopenaeus vannamei) at a relatively low temperature (20 °C). In the first of two laboratory experiments, we first abruptly transferred shrimps (6.91 ± 0.05 g wet weight, mean ± SE) from the rearing salinity (35 000 mg L^?1) to salinities of 5000, 15 000, 25 000, 35 000 (control) and 40 000 mg L^?1 at 20 °C. The survival of L. vannamei juvenile was not affected by salinities from 15 000 to 40 000 mg L^?1 during the 96‐h exposure periods. Shrimps exposed to 5000 mg L^?1 were significantly affected by salinity, with a survival of 12.5% after 96 h. The 24‐, 48‐ and 96‐h lethal salinity for 50% (LS₅₀) were 7020, 8510 and 9540 mg L^?1 respectively. In the second experiment, shrimps (5.47 ± 0.09 g wet weight, mean ± SE) were acclimatized to the different salinity levels (5000, 15 000, 25 000, 35 000 and 40 000 mg L^?1) and then maintained for 30 days at 20 °C. Results showed that the survival was significantly lower at 5000 mg L^?1 than at other salinity levels, but the final wet weight under 5000 mg L^?1 treatment was significantly higher than those under other treatments (P<0.05). Feed intake (FI) of shrimp under 5000 mg L^?1 was significantly lower than those of shrimp under 150 00–40 000 mg L^?1; food conversion efficiency (FCE), however, showed a contrasting change (P<0.05). Furthermore, salinity significantly influenced the oxygen consumption rates, ammonia‐N excretion rates and the O/N ratio of test shrimps (P<0.05). The results obtained in our work provide evidence that L. vannamei juveniles have limited capacity to tolerate salinities <10 000 mg L^?1 at a relatively low temperature (20 °C). Results also show that L. vannamei juvenile can recover from the abrupt salinity change between 15 000 and 40 000 mg L^?1 within 24 h.     

高盐胁迫对黄边糙鸟蛤(Trachycardium flavum)呼吸排泄和免疫酶活性的影响

为了探讨急性高盐胁迫对黄边糙鸟蛤(Trachycardium flavum)生理代谢和免疫酶活性的影响,分析了盐度自31骤升至37后2、12、24、48和72 h黄边糙乌蛤耗氧率、排氨率和不同组织Na+/K+-ATP酶、超氧化物歧化酶(SOD)、酸性磷酸酶(ACP)和碱性磷酸酶(ALP)的活性.结果显示,处理后2h耗氧率先降低,然后逐渐升高,在24和72 h显著高于对照组(P＜0.05);排氨率在2h极显著降低(P＜0.01),且在各时间点均低于对照组.外套膜、肝胰腺中Na+/K+-ATP酶活力在12 h显著降低(P＜0.05),肌肉和鳃中活力与对照组无显著差异.外套膜、肝胰腺和鳃中SOD活力在24 h达到最高值,显著高于对照组(P＜0.05),其后逐渐降低;肌肉中SOD活力在48 h达到最高值后降低.外套膜和鳃中ACP活力先升高后降低,肝胰腺中ACP活力显著降低(P＜0.05)后逐渐升高,肌肉中ACP活力与对照组无显著差异.肝胰腺和鳃中ALP活力先降低后显著升高(P＜0.05),与对照组相比,外套膜和肌肉中ALP活力无显著差异.结果表明,急性高盐胁迫对黄边糙鸟蛤的代谢水平和免疫酶活性均有显著影响且表现出时间效应性,高盐胁迫对免疫酶活性的影响具有组织特异性.     

体重和温度对方斑东风螺耗氧率和排氨率的影响

用室内实验生态学方法研究不同规格和温度对方斑东风螺(Babyloniaareolata)耗氧率(O)和排氨率(N)的影响。实验所用方斑东风螺规格为壳高(3 147±0 115)～(6 862±0 237)cm,软体部分干重(2 0145±0 12)～(11 0636±0 36)g。结果表明:(1)个体大小、温度以及二者的综合效应均对其耗氧率和排氨率有极显著的影响(P<0 01)。在实验温度范围内(13～33℃),不同规格的方斑东风螺耗氧率的总平均值为1 413mg/(h·g),排氨率的总平均值为217 05μg/(h·g)。(2)在实验条件下,方斑东风螺的软体部分干重(W)与耗氧量(R)之间的回归关系符合幂函数方程R=aWb,其中a的取值范围为0 9984～3 0128,平均值是1 7894;b值的范围为0 7692～0 8985,平均值为0 8430。在13～28℃温度范围内,不同规格的方斑东风螺的耗氧率随着温度的升高而增加,当温度升高到33℃时,耗氧率反而下降。(3)实验温度下,W与排氨量(A)也可用幂函数方程A=cWd表示,c值的范围为277 4091～405 3933,平均值为326 6857;d值的范围是0 4519～0 8864,平均值是0 6683。随着温度的升高方斑东风螺的排氨率呈上升趋势。(4)实验证实,高温将进一步提高方斑东风螺蛋白质的代谢水平,耗氧率和排氨率与温度(T)、W的二元线性回归方程分别为:O=-0 521-0 038W+0 050T、N=-152 640-10 581W     

温度对黄金鲈(Perca flavescens)耗氧率和排氨率的影响

在不同水温(15、20、25和30℃)下,对体重(46.1±4.5)g黄金鲈(Perca flavescens)的耗氧率和排氨率进行了测定与分析。结果显示:黄金鲈的耗氧率和排氨率均随温度的升高而显著增加(P<0.01);耗氧率和排氨率与温度的关系可用指数方程拟合,其方程分别为:RO=0.0682 e0.0633t,R2=0.9879;RN=2.4593 e0.0904t,R2=0.9703;随着温度的升高氧氮比(O:N)逐渐降低;耗氧Q10值和排氨Q10值均在20~25℃之间最小。结果表明:在各温度水平下黄金鲈基础代谢消耗底物主要均以蛋白质为主,脂肪其次,然而随着温度的升高,黄金鲈利用糖类和脂肪供能的比例逐渐下降,而蛋白质供能的比例逐渐增加。黄金鲈的最适生长温度为20~25℃。     

Physiological responses of pink abalone Haliotis corrugata (Gray, 1828) exposed to different combinations of temperature and salinity

Physiological responses of pink abalone Haliotis corrugata were determined under different temperature and salinity conditions. Oxygen consumption rate was not affected by temperature and salinity. Ammonium excretion of pink abalone was inversely related to salinity. The O:N ratio indicated that abalone maintained in lower salinities had an interval of 4.9–7.7, which is indicative of a protein‐dominated metabolism, whereas the O:N in 35‰ was 28.8–35.5 for both temperatures, suggesting that carbohydrates were used as energy substrate. Haemolymph osmolality of abalone exposed to 20 and 24 °C was slightly hyperiso‐osmoconformic in salinity ranges of 20–35‰. The results of this study suggested that for optimized culture, pink abalone should be cultivated at 24 °C at a salinity of 35‰.     

Effects of phytase pretreatment of soybean meal and phytase-sprayed in diets on growth, apparent digestibility coefficient and nutrient excretion of rainbow trout (Oncorhynchus mykiss Walbaum)

Rainbow trout were fed a diet containing phytase-sprayed and phytase-pretreated soybean meal with different phytase levels. The single factor random block design was used to analyze the effects on rainbow trout of dietary phytase supplementation on growth performance, nutritional ingredient digestibility and nutrient excretion. After 90 days, the results showed that feed conversion ratio (FCR) and protein efficiency ratio (PER) were significantly improved and specific growth rate (SGR) was not affected by spraying phytase, but SGR, FCR and PER were not significantly improved by phytase pretreatment. A digestibility trial conducted after the feeding trial showed that apparent digestibility coefficient (ADC) of diet protein and minerals was increased with phytase supplementation. However, there was a negative effect of phytase on the ADC of lipid. The excretion experiment showed that the supplementation of phytase resulted in decreased nutrient excretion in feces, but lipid excretion was slightly increased with phytase supplementation. In addition, the results of P excretion and ADC of P analyzed by t-test showed that phytase pre-treatment method should be a more rational method than the spraying method. The results of SGR, ADC of P and P excretion analyzed by quadratic regression indicated that 2,000–3,000 U/kg levels by the spraying method could be a rational range of phytase supplementation, and about 1,000 U/kg should be an optimal level by the pretreatment method. Thus, use of phytase in rainbow trout feeds can have economic and environmental benefits.     

盐度胁迫对泥蚶能量代谢的影响

在水温(26.4±0.79)℃、盐度11、14.5、18、21.5、25和28.5下,将壳长27~28mm泥蚶饲养在流水系统中24h,每一盐度梯度设置3个平行和3个空白对照,以研究盐度对泥蚶摄食、代谢、碳收支及能量代谢的影响。试验结果显示,随着盐度的升高,泥蚶的滤水率、摄食率、吸收率和O∶N均先升后降,而耗氧率与排氨率先降后升,在盐度18~21.5时显著达到极值(P0.05),但盐度对泥蚶的耗氧率、排氨率和O∶N影响不显著(P0.05)。泥蚶代谢所需要的能量主要由脂肪和碳水化合物提供,盐度18~21.5为泥蚶的适宜盐度范围,此时的能量代谢方程分别为:100C=26.12F+30.75R+5.78U+37.35P;100C=25.06F+32.03R+5.15U+37.76P。     

复合酵母培养物对奶牛产奶性能、氮排放及血液生化指标的影响

为研究饲料中添加复合酵母培养物对奶牛产奶性能、氮排放及血液生化指标的影响,选取年龄、体重、产奶量及泌乳期相近(135±15) d的荷斯坦奶牛24头,随机分为4组,每个处理6个重复,对照组和3个试验组的复合酵母培养物添加量分别为精料浓度的0,0.8%,1.0%,1.2%,随精料饲喂,测定产奶量、乳成分、氮排放及血液生化指标,结果表明,1)试验2组日均产奶量显著高于对照组(P<0.05),各试验组分别比对照组提高8.48%,10.05%,8.97%。2)复合酵母培养物能显著提高乳脂和乳蛋白率(P<0.05),显著降低牛奶体细胞数(P<0.05),以试验2组最低。3)在氮排放量上,试验2组显著低于对照组(P<0.05),各试验组比对照组分别降低8.47%,12.01%,9.36%。4)在血液生化指标方面,复合酵母培养物能提高血清中总蛋白、球蛋白、血糖、胰岛素水平(P<0.05),降低尿素氮水平(P<0.05)。由此可见,本试验条件下,综合考虑产奶量、乳成分、氮排放及血液生化指标,复合酵母培养物的最佳添加量为精料浓度的1.0%。