烟酸对热应激奶牛生产性能、血清生化指标的影响

选择健康泌乳后期的中国荷斯坦奶牛3头,采用3×3拉丁方设计,在基础日粮中分别添加0、8、15 g/(头.d)的烟酸,试验期63 d,研究了日粮中添加不同水平的烟酸对热应激奶牛生产性能、血清生化指标的影响。结果表明:烟酸对热应激状态的奶牛直肠温度和呼吸频率影响未达显著水平;日粮中添加8、15 g/(头.d)烟酸奶牛的产奶量分别比对照组提高29.9%、22.0%(P<0.05),4%标准乳产量比对照组分别提高了28.5%和21.5%(P<0.05),且不同添加水平间无显著差异(P>0.05),添加烟酸对奶牛的乳蛋白、乳脂和乳糖含量影响未达到显著水平;2个试验组都能够维持奶牛血清皮质醇水平的基本恒定,降低了胆固醇和甘油三酯的水平,但与对照组相比差异不显著(P>0.05)。综合分析表明,给热应激奶牛补饲烟酸有助于缓解热应激,烟酸适宜添加量为8 g/d。     

保护性蛋氨酸对中国荷斯坦奶牛血浆代谢产物及生产性能的影响

选择25头中国荷斯坦奶牛,分成对照组,试验一组(添加30 g DL-蛋氨酸),试验二组(添加45 g保护性蛋氨酸),试验三组(添加30 g DL-蛋氨酸+50 g L-赖氨酸)和试验四组(添加45 g保护性蛋氨酸+50 g L-赖氨酸)进行饲养试验。试验表明:试验四组和试验二组产奶量显著(P<0.05)高于对照组,分别提高6.31 %和6.73 %,其他组差异不显著(P>0.05);试验四组和试验二组乳脂率显著(P<0.05)高于对照组,分别提高6.25 %和6.55 %;并且试验四组和试验二组乳脂率也显著(P<0.05)高于试验一组。乳蛋白、体细胞数、全脂固形物和非脂固形物各组间差异不显著(P>0.05)。试验四组和试验二组血浆白蛋白和总蛋白显著高于对照组(P<0.05),其它各组差异不显著(P>0.05)。试验二组血浆尿素氮(PUN)显著低于对照组和试验一组(P<0.05),其他各组差异不显著(P>0.05)。血浆游离脂肪酸和总氨基酸浓度各组差异不显著(P>0.05)。由此得出结论:一方面,保护性蛋氨酸(RPMet)的一部分能避免瘤胃微生物的降解,以保护性Met的形式提供给瘤胃后Met;另一方面,保护性蛋氨酸的降解部分改善了瘤胃的发酵,促进瘤胃微生物的合成,这两方面的作用提高了奶牛的产奶量和乳成分。     

Effect of oilseeds rich in linoleic and linolenic acids on milk production and milk fatty acid composition in dairy cows

Nine multiparous cows averaging 93±13 days in milk production (DIM) were used in a triple 3×3 Latin square design to determine the effects of feeding them whole roasted flaxseed, cracked roasted soybean and fresh alfalfa in the diet on milk production, milk fatty acid profiles and the digestibility of nutrients. Each experimental period lasted 30 d and a sample collection was performed during the last 7 d. The cows were fed on the control basal diet (CON) or diets containing whole roasted flaxseed (FLA) or cracked roasted soybean (SOY). All diets were fed as a total mixed ration (TMR) and had similar concentrations of crude protein (CP), Net Energy Lactation (NEL), acid detergent fibre (ADF) and neutral detergent fibre (NDF). The dry matter intake (DMI) was not significantly different (P>0.05), but tended to increase in FLA and SOY diets compared with the control (P>0.05). Cows in all treatments had a similar milk yield, although 4% fat corrected milk (FCM) yield was higher on the FLA and SOY diets than on the CON diet. Milk fat percentage (3.45%) increased in the FLA diet compared with the control (3.31%) and SOY diets (3.39%). Milk protein percentages were similar among the diets (P>0.05). There were similar digestibilities of DM, CP and ADF among the treatments and lower digestibilities of NDF and ether extract in the SOY diet compared with the CON diet. Feeding various oilseeds significantly increased the concentrations of C_18:1, C_18:3 and conjugated linoleic acid (CLA). The FLA diet decreased the ratio of omega-6 to omega-3 fatty-acids in the milk, which would improve the nutritive value of the milk.     

华南地区荷斯坦牛泌乳性能在季节、胎次、泌乳时期影响下的变化规律

【目的】分析华南地区季节变化、繁育胎次、泌乳时期对泌乳性状的影响。【方法】采集广州某规模化牛场2015年全年10 450头次的荷斯坦牛的奶牛群改良计划(DHI)测定数据,提取产奶量、乳脂率、蛋白率和脂蛋比等泌乳性状数据,运用统计模型评估季节、胎次、泌乳时期等因素对泌乳性状的影响,分析各性状之间的相关性。【结果】季节、泌乳时期和胎次分别对产奶量和乳成分含量产生极显著的影响(P0.001)。夏季产奶量极显著低于其他季节(P0.01);在乳成分上,夏季的各项指标均为最低值,且极显著低于春冬季节(P0.01),春季各项指标值极显著高于冬季(P0.01);产奶量和乳蛋白率在12月(非气温最低的1月)达到最高值;不同胎次牛的产奶量上,1胎牛在第3个泌乳月份达到泌乳高峰,其他胎次牛则出现在第2个泌乳月且峰值高于1胎牛,但1胎牛产奶量下降速率明显低于其他胎次牛。1胎至2胎牛产奶总量逐渐升高,之后随着胎次的增加而下降;从乳成分的变化来看,各项指标在第1胎次时最高,随着胎次的增加逐步降低,到4和5胎时出现增加。在泌乳时期内,脂蛋比出现前期高后期低的变化规律,且乳脂率和乳蛋白率之间存在极显著的正相关性(r=0.63,P0.01)。【结论】华南地区泌乳牛不仅遭受长期的热应激影响,在冬季同样受到低温冷应激作用而制约其泌乳性能。高胎次(3胎以上)奶牛所占的群体比例较低导致全年泌乳胎次较低,同时当前的日粮营养和饲养水平已严重阻碍高胎次牛在泌乳后期的生产表现。     

Effects of folic acid supplementation on growth performance and hepatic folate metabolism-related gene expressions in weaned piglets

The present study was conducted to evaluate the effects of different folic acid supplemental levels on growth performance, serum biochemical indicators, and hepatic folate metabolism-related gene expressions in weaned piglets. There were 160 piglets with initially average bodyweight of 7.33 kg randomly assigned to diets containing five levels of folic acid: basal diets (C), 0.5 mg·kg⁻¹ folic acid (FS 0.5), 2.5 mg·kg⁻¹ folic acid (FS 2.5), 5.0 mg·kg⁻¹ folic acid (FS 5.0), or 10.0 mg·kg⁻¹ folic acid (FS 10.0). Blood samples were collected from a subset (n = 20; 4 pigs per treatment) of the piglets on day 0, 14, and 28. Liver samples were collected from the blood-taken piglets on day 28 of the experiment. Pigs fed basal diet supplemented with 2.5 mg·kg⁻¹ folic acid grew faster (P<0.05) and consumed more feed (P<0.01) than groups of C, FS 5.0, and FS 10.0 during the last two weeks. Dietary treatment had no effect on F/G throughout the experiment. Pigs in the FS 2.5 group showed greater concentrations of Growth Hormone (GH) (P<0.05) and Insulin-like Growth Factors (IGF-1) (P<0.01) in serum than C and FS 10.0 on day 28. RT-PCR analysis revealed that FS 0.5, FS 2.5, and FS 5.0 had a greater abundance of the mRNA encoding 5,10-methylenetetrahydrofolate reductase than C and FS 10.0 (P<0.01). The mRNA expressions of folate binding protein in FS 0.5 and FS 2.5 were upregulated compared with pigs fed with basal diet (P<0.05). These results demonstrated that folate supplemental level of 2.5 mg·kg⁻¹ significantly enhanced the growth performance of piglets. Folic acid had an impact on folate metabolism and the homocysteine concentrations. No folate supplementation or folate supplemental level of 10 mg·kg⁻¹ could not increase the growth performance to the greatest degree.     

Effect of breed, sex and birth parity on growth, carcass and meat quality in pigs

The effects of breed, sex and birth parity on the traits of growth, carcass and meat quality were investigated in three different breeds including Swedish Landrace, British Large White and an indigenous Chinese breed — Tongcheng pigs. The results indicated that the Swedish Landrace and the British Large White had advantages over the Tongcheng pigs in growth rate, feed conversion rate (FCR) and carcass traits, but had disadvantages in meat quality. In contrast to the British Large White, the Swedish Landrace had higher average daily gain during the trial (ADG2) (877.04 g·day⁻¹ vs. 813.95 g·day⁻¹, P < 0.05), and marbling score (MS) (2.48 vs. 2.02, P < 0.01), larger eye muscle area (EMA) (41.80 cm² vs. 35.14 cm, P < 0.01) and more efficient feed conversion rate (FCR) (3.06 vs. 3.29, P < 0.05), lower muscle shear force (MSF) (4.20 kgf (1 kgf = 9.80665 N) vs. 4.93 kgf, P < 0.05) and backfat thickness (BF) (all P < 0.01) including live backfat thickness (LBF), average backfat thickness at 3 points in the carcass (ABF), backfat thickness between 6th and 7th ribs (6–7 th BF) and backfat thickness at 10th rib (10 th BF). There was a difference (P < 0.05) only inMS between castrated females (CF) and castrated males (CM). Birth parity affected ADG2 (P < 0.05), some carcass characteristics and meat quality, including CL₁ (P < 0.001), CL₂ (P < 0.05), BF (ABF, 6–7th BF and 10th BF, all P < 0.001), EMD (P, 0.001), EMA (P < 0.001), percentage of leaf and caul fat (PLC) (P < 0.05), proportion of lean and bone of the ham (PLBH) (P < 0.05), muscle drip loss percentage (DL) (P < 0.05) and intramuscular fat content (IMF) (P < 0.05). The breed-sex interaction only impacted the average daily gain from birth to marketing (ADG1) and DL (both P < 0.05). However, there was no significant effect of sex-parity interaction on all the traits tested.     

不同水平甘蔗糖蜜酵母发酵浓缩液对奶牛生产性能和血清生化指标的影响

为研究不同水平甘蔗糖蜜酵母浓缩液(CMS)对奶牛生产性能和血清生化的影响,采用单因素试验设计,选用60头体况、胎次、泌乳天数和产奶量相近的健康荷斯坦奶牛随机分为4组,每组15头.对照组(CON)饲喂基础日粮,试验组在对照组日粮的干物质基础上分别添加1％、3％和5％的CMS,即CMS1组、CMS2组和CMS3组.预试期1...     

Research on Yucca schidigera extract feeding on the rumen ecology, protozoal populations and serum chemistries of sheep

In a completely randomized block design experiment, 16 ruminally cannulated male sheep with body weights of (40 ± 2.1) kg were fed twice daily (8:00 and 16:00) with concentrate and forage (50:50 on dry matter (DM) basis). Dietary treatments were supplemented with intraruminal doses of powdered Yucca schidigera extract (YSE) at the levels of 0 (control), 100, 200 and 300 mg · kg⁻¹. On days of 15, 16 and 17 after feeding, ruminal content was sampled at 0, 2, 4, 6 and 8 h after dosing (8:00), and blood samples were collected at the end of experiment (the days 18 and 19 after feeding). Results showed that the treatment groups’ acidity was not affected (P = 0.13) by YSE. Comparing to the control, the ruminal propionate concentration was increased by YSE addition in a dose-dependent manner by up to 29.8% (P < 0.05), and the acetic concentration was decreased by up to 17.5% (P < 0.05). The ruminal ammonia concentration 2 hours after feeding was higher (P < 0.05) in sheep fed without YSE (increased by 17.57 mg· 100 mL⁻¹) than those fed with YSE at 200 mg · kg⁻¹ (6.77 mg · 100 mL⁻¹ increase in NH₃) and at 300 mg · kg⁻¹ (6.50 mg· 100 mL⁻¹ increase in NH₃). Protozoal populations in the rumen were lower (P < 0.05) with the YSE feeding dose at 300 mg · kg⁻¹ than the control. The serum chemistries were not different among treatments (P > 0.05) and were within the normal physiological ranges for sheep 19 days after feeding. The study indicated that 200 mg· kg⁻¹ and 300 mg· kg⁻¹ YSE groups had particular suppressing effects on ruminal ammonia concentration, ammonia-N concentrations and protozoal populations. The effect of YSE on ruminal fermentation could be attributed to the selective inhibitory effect on rumen microbial species. High level (300 mg · kg⁻¹) YSE as feed additives resulted no negative impact on sheep in our tests.     

Effects of dietary squid viscera meal on growth and cadmium accumulation in tissues of large yellow croaker, Pseudosciaena crocea R.

Cadmium (Cd) is a toxic environmental pollutant with a long biological half-life and can produce both hepatic and renal injuries in mammals and fish. Squid viscera meal (SVM), an effective attractant for aquatic animals, is widely used as an ingredient in aquafeeds. However, SVM is rich in Cd and its complexes. A study was conducted to evaluate the effects of dietary SVM on the growth and Cd deposition in the tissues of large yellow croaker, Pseudosciaena crocea R. Three practical diets were formulated to contain a 0, 50 and 100 g · kg⁻¹ SVM diet, correspondingly containing a 0.21, 7.26 and 12.08 mg Cd · kg⁻¹ diet. Each diet was randomly assigned to triplicate groups of 100 juveniles of large yellow croaker (mean initial weight, 9.75 ± 0.35 g) in floating sea cages (1.0 m × 1.0 m × 1.5 m). Fish were fed twice daily (05:00 and 17:00) to satiation for 8 weeks. The results showed that there were no significant differences in fish survival among the three dietary treatments, but significant higher specific growth rates (SGR) were observed in the fish fed diets with 50 or 100 g · kg⁻¹ SVM diet compared to the control group (P < 0.05). The cadmium concentrations in fish tissues (muscle, liver, kidney and gill) were significantly influenced by the dietary SVM. The cadmium concentrations in all tissues significantly increased with increasing dietary Cd levels (P < 0.05). In all the dietary treatments, the highest Cd level was always observed in the kidney, followed by the liver and the gill. Fish fed diets with 50 and 100 g · kg⁻¹ SVM had significantly higher Cd accumulations in the kidney (2.65, 4.44 mg · kg⁻¹), liver (0.58, 0.93 mg · kg⁻¹) and gill (0.35, 0.53 mg · kg⁻¹) compared with the control group (0.42, 0.26 and 0.12 mg · kg⁻¹, respectively). The Cd level in fish muscle, however, was undetectable in all treatments. Therefore, based on these results, accumulation of Cd in edible tissue (muscle) of farmed large yellow croaker is not a food safety issue. However, long-term feeding of diets with SVM may result in accumulation of Cd in the kidney, liver and gills of fish.     

Effects of supplemental energy sources and <Emphasis Type="Italic">trans</Emphasis>-10, <Emphasis Type="Italic">cis</Emphasis>-12 conjugated linoleic acids (CLA) on milk yield and composition in lactating Holstein cows

The effects of supplemental energy sources (corn or saturated fatty acids) and trans-10, cis-12CLA on milk yield and composition were investigated in the present study. Four multiparous Holstein cows (560±31 kg BW, 98±10.5 DIM) were designated to a 2×2 factorial 4×4 Latin Square experiment. Treatments were isoenergetic supplementation of corn or calcium salt of saturated fatty acids (CaFA) with or without calcium salt of CLA. Both milk yield and composition were affected by sources of supplemental energy. Compared to CaFA supplementation, corn supplementation increased the milk yield, the lactose yield, and the content and yield of milk protein but decreased the yield and content of milk fat. Plasma insulin was higher, plasma glucose tended to be higher, and plasma non-esterified fatty acid (NEFA) was lower when corn rather than CaFA was supplemented. CaCLA supplementation did not affect milk yield and the yield of measured milk components, but increased the content of milk protein and decreased the content of total solids. Plasma glucose was decreased by CaCLA supplementation. Content and yield of short and medium chain fatty acids (⩽16 carbon atoms) in milk fat increased or remained unchanged while those of long chain fatty acids (> 16 carbon atoms) decreased or remained unchanged by corn supplementation. CaCLA supplementation failed to increase the content and yield of trans-10, cis-12CLA in milk fat, which explained the unobserved depression of milk fat synthesis by CaCLA supplementation. Yields of de novo synthesized fatty acids in the mammary gland were increased rather than decreased by corn supplementation. The decreased milk fat yield by corn supplementation could be exclusively attributed to reductions in preformed fatty acids, which might be a result of depressed lipolysis by stimulated insulin secretion.     

大豆异黄酮和抗生素对文昌鸡生长性能、肉品质和血浆抗氧化指标的影响

【目的】对比大豆异黄酮和抗生素对文昌鸡生长性能、肉品质及血浆抗氧化指标的影响,为大豆异黄酮在文昌鸡生产中的实际应用提供参考。【方法】选用1日龄文昌鸡母雏540只。试验分3组,包括空白对照组、抗生素组和大豆异黄酮组,每组4个重复,每个重复45羽。分小鸡、中鸡和大鸡3个阶段进行试验。【结果】生长性能结果显示,1~30日龄小鸡各组之间的平均日增质量、平均日采食量和料重比均无显著差异(P0.05);31~80日龄阶段,大豆异黄酮组的平均日增质量显著高于对照组(P0.05);81~120日龄阶段,大豆异黄酮组的平均日采食量显著高于对照组(P0.05)。肉品质结果显示,各组的肉色L*、a*、b*和pH差异均不显著(P0.05);与对照组相比,大豆异黄酮组的熟肉率显著提高(P0.05)。血浆抗氧化指标结果显示,31~80日龄阶段,大豆异黄酮组的总抗氧化能力(Total antioxidant capacity,T-AOC)活性显著高于抗生素组(P0.05);81~120日龄阶段,大豆异黄酮组的肌酸激酶(Creatine kinase,CK)活性显著低于抗生素组,谷胱甘肽(Glutathione,GSH)含量显著高于抗生素组,抗生素组和大豆异黄酮组的T-AOC活性显著高于对照组(P0.05)。【结论】中鸡阶段饲粮中添加20 mg·kg~(–1)大豆异黄酮可以提高鸡日增质量和抗氧化水平;大鸡阶段饲粮中添加15 mg·kg~(–1)大豆异黄酮能够提高鸡采食量、熟肉率和抗氧化水平。     

宁夏地区荷斯坦牛乳成分及相关指标的非遗传因素、体细胞评分变化规律

目的 阐明非遗传因素对宁夏地区荷斯坦牛乳成分及相关指标的影响。方法 基于宁夏地区荷斯坦奶牛DHI测定数据,利用SAS 9.2软件GLM过程分析胎次、泌乳时期和产犊季节对9项泌乳性状的影响,并探究泌乳性状在不同体细胞评分中的变化规律。结果 胎次、泌乳时期、产犊季节、泌乳时期×产犊季节对9项泌乳性状的影响均达到显著水平(P<0.05)。对不同胎次进行比较,乳脂率和乳固形物含量在第2胎后显著下降(P<0.05),乳蛋白率和高峰奶量在第3胎后显著下降(P<0.05);日产奶量第4胎后稍有降低;乳糖率则呈现先下降后上升的趋势,在第3胎达到最低(P<0.05),为4.84%。体细胞评分随着胎次的增加逐渐上升,泌乳高峰日在第1胎次最晚出现(94.07 d),第4胎次最早(67.33 d)。对不同泌乳时期进行比较,日产奶量和乳糖率在第2、3胎随着泌乳时期的延长逐步下降(P<0.05),而乳蛋白率、乳固形物含量、体细胞评分和乳脂率呈上升趋势(P<0.05)。对不同产犊季节进行比较,1~3胎乳脂率和第1胎乳固形物含量春季至冬季均逐步下降;第1胎日产奶量和乳糖率呈上升趋势,到第2、3胎时在夏季分别处于最低水平;1~3胎乳蛋白率、体细胞评分、泌乳高峰日和高峰奶量春季至冬季均呈先升高后降低的趋势,且各性状不同胎次均在夏季达到最高水平。随着体细胞评分增高,乳糖率、日产奶量及高峰奶量整体上逐渐下降,乳脂率和乳蛋白率呈缓慢上升趋势,乳固形物含量和泌乳高峰日在体细胞评分分别为4和5时达到最高水平。结论 本研究结果为提高宁夏地区荷斯坦奶牛泌乳性能及生鲜乳质量提供了理论依据。     

木薯渣对奶牛产奶量和奶品质的影响

试验选用30头体重约400kg、健康无病、胎次相同,且处于泌乳中期,产奶量相近（P〉0.05）的荷斯坦奶牛,随机分为2组：对照组10头,用产奶期正常饲料饲喂;试验组20头,每头牛在对照组日粮基础上投5kg木薯渣替代5kg苜蓿干草,研究木薯渣对奶牛产奶量及奶品质的影响。结果表明：在产奶期日粮中添加木薯渣对奶牛的产奶量没有显著影响（P〉0.05）;从乳成分分析统计数据看,其对奶牛的乳成分影响不明显,乳脂、乳蛋白、乳糖、乳固形物和非脂固形物均无显著差异（P〉0.05）。     

Effects of Bupleurum extract on blood metabolism,antioxidant status and immune function in heat-stressed dairy cows

This experiment was conducted to evaluate the effects of Bupleurum extract(BE) on blood metabolites, antioxidant status, and immune function in dairy cows under heat stress. Forty lactating Holstein cows were randomly assigned to 1 of 4 treatments. The treatments consisted of 0, 0.25, 0.5, and 1.0 g of BE kg–1 dry matter. Supplementation with BE decreased(P0.05) blood urea nitrogen(BUN) contents and increased blood total protein(TP) and albumin(ALB) levels compared with control cows, but it had no effects(P0.05) on blood glucose(GLU), nonesterified fatty acid(NEFA), total triglyceride(TG), low-density lipoprotein cholesterol(LDL-C), and high density lipoprotein cholesterol(HDL-C). Compared with control cows, cows fed BE had higher(P0.05) superoxide dismutase(SOD) and glutathione peroxidase(GSH-Px) activity. However, supplementation with BE had no effect(P0.05) on total antioxidant capacity(T-AOC) or malondialdehyde(MDA) levels. The immunoglobulin(Ig) A and G contents increased(P0.05) in cows fed 0.25 or 0.5 g of BE kg–1. Interleukin(IL)-2 and IL-4 levels were higher(P0.05) in cows fed 0.5 and 1.0 g of BE kg–1, and IL-6 was significantly elevated(P0.05) in cows fed 0.5 g of BE kg–1. There were no treatment effects(P0.05) on the CD4+ and CD8+ T lymphocyte ratios, CD4+/CD8+ ratio, or tumor necrosis factor-α(TNF-α) level among the groups. These findings suggest that BE supplementation may improve protein metabolism, in addition to enhancing antioxidant activity and immune function in heat-stressed dairy cows.     

复合生物预混剂对奶牛生产性能和乳品质的影响

为探讨相同日粮条件下添加复合生物预混剂对奶牛生产性能和乳品质的影响,选取 20 头年龄、胎次、泌乳日龄、妊娠期、产奶量、体重基本相似且身体健康的荷斯坦奶牛随机分为2组,每组10头。分别饲喂对照组（普通型预混剂）和试验组（项目组研制的5%的复合生物预混剂）日粮,两种日粮基础配方相同,含预混剂不同,经74 d试验期显示：整个试验期对照组与试验组每头日平均产奶量差异显著（P<0.05）;随着泌乳期的延长,试验组乳脂肪率增加125%,显著高于对照组（P<0.05）;两组乳蛋白率和乳中总固形物含量有增加趋势,差异不显著（P＞0.05）。表明奶牛日粮中添加复合生物预混剂可以显著提高奶牛产奶性能、改善乳品质。     

Effects of Chinese herbal formula Heat-stress-releasing on antioxidant function in dairy cows

In order to investigate the effects of a Chinese herbal formula Heat-stress-releasing on the antioxidant function in dairy cows, ten dairy cows were randomly divided into the control group and the experimental group, with five cows in each group. All the cows were fed with a basal diet. The animals in the experimental group were given with 220 g of herbs per day in addition to the basal diet. The trial was conducted for 14 days. Blood samples were taken from the vena cava at day 0, day 7, and day 15, respectively. The antioxidant statuses were examined. The results are as follows. (1) Heat-Stress-releasing formula can significantly increase the milk yield of dairy cows under heat stress. Compared with the control group, the milk yield of the herb-treated group increased by 14.01% (P<0.05), 14.32% (P<0.05) and 15.01% (P<0.05) in prophase, metaphase and anaphase of the test, respectively. (2) Heat-Stress-releasing formula can increase significantly the antioxidant status of the heat stressed dairy cows. Compared with the control group, the superoxide dismutase (SOD) activity increased by 45.93% (P<0.01) at day 7 and by 54.40% (P<0.01) at day 15. The Glutathioneperoxidase (GSH-PX) activity of the test group increased by 17.99% (P<0.05) at day 7 and 25.98% (P<0.01) at day 15. The total antioxidant capacity (T-AOC) of the test group increased by 43.64% (P<0.01) at day 7 and 46.35% (P<0.01) at day 15. The malondaldehyd (MDA) content of test group declined by 23.88% (P<0.01) at day 7 and 25.32% (P<0.01) at day 15.     

大豆黄酮对产奶量和牛奶品质的影响

为研究大豆黄酮对奶牛日产奶量、乳脂率及乳蛋白含量的影响,选用24头中国荷斯坦奶牛,按产奶量、泌乳月及胎次配对随机分成3组（n=8）,试验组在日粮中分别添加30mg／kg（DA1）和60mg／kg（DA2）的大豆黄酮。于第1,10,20天,测定产奶量、乳脂率及乳蛋白含量。结果表明：与对照组相比较,最终试验组平均Et奶产量分别提高7．62％（DA1,P〈0．05）和15．18％（DA2,P〈0．01）。乳脂率3组间没有明显差异,而乳蛋白含量DA2组比对照组增加20．07％,差异显著（P〈0．05）。     

Adventitious shoot regeneration from the leaves of some pear varieties (Pyrus spp.) grown in vitro

The pear (Pyrus spp.) is one of the most important temperate fruit crops. A complete protocol for adventitious shoot regeneration was developed from the leaves of four pear varieties grown in vitro: Abbe Fetel, Yali, Packham’s Triumph and Aikansui, and the Chinese rootstock variety Duli. Shoot explants were collected from the field and cultured in vitro in Murashige and Skoog (MS) media supplemented with 1.0 mg·L⁻¹ 6-benzylaminopurine (BA) and 0.1 mg·L⁻¹ indole-3-butyric acid (IBA). After four weeks, leaf explants of all 5 varieties grown in vitro were excised and cultured in MS media supplemented with 0.0 mg·L⁻¹, 0.2mg·L⁻¹, 0.5 mg·L⁻¹, 1.0 mg·L⁻¹ and 2.0 mg·L⁻¹ naphthaleneacetic acid (NAA) and 5.0 mg·L⁻¹ BA or with 1.0 mg·L⁻¹, 2.0 mg·L⁻¹ and 4.0 mg·L⁻¹ thidiazuron (TDZ). The cultures were maintained in darkness for 21 days for shoot induction in the shoot induction medium (IM), then transferred to the shoot expression medium (EM) in 1.0 mg·L⁻¹ TDZ without any auxins and kept in a growth room at (25±2)°C under a 16/8 h light/dark photoperiod regime for 8 weeks. Finally, the shoots were transferred to the MS shoot elongation medium (SEM) supplemented with 0.2 mg·L⁻¹ BA, 0.1 mg·L⁻¹ IBA and 0.2 mg·L⁻¹ gibberellic acid (GA₃). A combination of TDZ and NAA had a significant effect on the number of shoot regenerations in all 5 tested varieties. The maximum mean number of shoots and maximum number of shoots per leaf obtained from Yali variety were 11.8 (P⩽0.001) and 22, followed by Aikansui with 6.6 (P⩽0.001) and 4.6, and Duli with 8 (P⩽0.001) and 12, all arising from the combination of 0.2 mg·L⁻¹ NAA with 1.0 mg·L⁻¹ TDZ. For Packham’s Triumph and Abbe Fetel, the maximum mean number of shoots and maximum number of shoots per leaf were 5.6 (P⩽0.001), 4.8 and 8 (P⩽0.001), and 11, respectively, from the combination of NAA (1.0 mg·L⁻¹) and TDZ (2.0 mg·L⁻¹). Abbe Fetel was the only variety which produced significantly higher adventitious shoots from the two different combinations of 1.0 mg·L⁻¹ NAA and 5.0 mg·L⁻¹ BA (P⩽0.05), and 2.0 mg·L⁻¹ NAA and 5.0 mg·L⁻¹ BA (P⩽0.01). Some of the most prominent problems associated with shoot proliferation and regeneration were also observed and discussed in this paper.     

Effect of extracts of Chinese pine on its own seed germination and seedling growth

The allelopathic potential of Chinese pine (Pinus tabulaeformis Carr.) against its own seed germination and seedling growth was tested with aqueous extracts (0.01, 0.02, 0.05, and 0.10 g·mL⁻¹) obtained from different organs (roots and litter needles) at different individual ages (12, 52, and 110 years old). The results showed that root and litter extracts had different effects on seed germination and seedling growth, and the effects varied with the concentrations, the organs, and the tree age of extracts. The strongest stimulatory effect on seed germination of Chinese pine was exposed to 0.02 g·mL⁻¹ root extract from the 110 years old Chinese pine trees and exposed to 0.02 g·mL⁻¹ litter extract from the 12 years old Chinese pine trees. Meanwhile, the strongest stimulatory effect on growth of Chinese pine seedlings was exposed not only to 0.01 g·mL⁻¹ root extracts from the 110 years old Chinese pine but also to 0.01 g·mL⁻¹ litter extract from the 12 years old Chinese pine. The promoting effect of the extracts of root on seed germination and seedling growth increased in the order of 12, 52, and 110 years old. The promoting effect of the extracts of litter on seed germination and seedling growth increased in the order of 110, 52, and 12 years old. Our results suggested that litter leachates or root exudates of Chinese pine may influence the natural regeneration within Chinese pine stands via the release of allelochemicals into the environment.     

Effects of different selenium sources and levels on serum biochemical parameters and tissue selenium retention in rats

A total of 54 femaleWistar rats were allotted to nine treatments by weight and fed basal diet or diets containing Se of 0.05, 0.10, 0.15, or 0.20 mg·kg⁻¹ diet provided with either Se yeast or sodium selenite for 10 days. The results showed the following: (1) Selenium yeast had better effects compared with sodium selenite on increasing serum superoxide dismutase activities (P<0.05). Addition of Se yeast or sodium selenite increased the activities of serum gluthathione peroxidase (P<0.01); (2) According to slope ratio assay, the bioavailability of Se from Se yeast was 132.1%, 205.7%, 140.0%, and 107.2% of that from sodium selenite when glutathione peroxidase activities and Se contents in serum, kidney, and liver were used as indicators. It is concluded that Se from Se yeast has higher bioavailability than Se from sodium selenite.