锌源和锌水平对断奶应激仔猪血清生化指标的影响

选用(26±2)日龄"杜长大"三元杂交断奶仔猪100头,按体质量和性别随机分成5组,每组20头,分别饲喂基础日粮、基础日粮 2 000 mg/kg氧化锌、基础日粮 3 000 mg/kg氧化锌和基础日粮 250 mg/kg蛋氨酸锌、基础日粮 500 mg/kg蛋氨酸锌。试验期14 d。断奶后于前腔静脉采血,测定部分血清生化指标水平。结果表明,高锌日粮能显著提高断奶应激仔猪体质量(AW)、平均日增重(ADG)和日采食量(ADFI),降低料重比(F/G)和断奶后腹泻率。断奶后仔猪血清总蛋白(TP)、白蛋白(ALB)、球蛋白(GLOB)、总胆固醇(CHL)、碱性磷酸酶(ALP)水平显著或极显著下降(P<0.05或P<0.01),对照组仔猪血清尿素氮(SUN)含量在断奶后7 d极显著升高(P<0.01)。断奶前后,血清谷丙转氨酶(GPT)和谷草转氨酶(GOT)活性无显著差异。添加高锌显著提高断奶仔猪血清ALP水平,降低血清钙(Ca)和血清磷(P)浓度,对上述其他生化指标无显著影响。     

日粮添加丁酸梭菌对断奶仔猪生长性能和腹泻率的影响

为了评价日粮中添加丁酸梭菌制剂对断奶仔猪生长性能和腹泻率的影响,本研究选用120头"杜×长×大"断奶仔猪,添加不同水平丁酸梭菌的玉米-豆粕型日粮为试验日粮,测定猪的生长性能相关指标和腹泻率。结果表明:中剂量试验组(日粮中添加10×10~4 CFU/g丁酸梭菌)断奶仔猪28～42日龄的平均日增重(Average Daily Gain,ADG)比对照组仔猪显著提高7.28%(P0.05),平均日采食量(Average Daily Feed Intake,ADFI)差异不显著(P0.05)。各试验组与对照组相比,料重比(Feed∶Gain,F/G)均显著降低(P0.05)。在43～56日龄阶段,与对照组相比,中剂量试验组断奶仔猪的ADG显著增高,F/G显著降低,ADFI显著增加。在28～56日龄阶段,与对照组相比,各试验组断奶仔猪的ADG和ADFI均显著提高,F/G均显著降低,试验组仔猪的腹泻率显著降低,说明日粮中添加丁酸梭菌能提高断奶仔猪的生长性能,减少断奶仔猪腹泻发生。     

谷氨酰胺对脂多糖应激仔猪生长性能及血清生化指标的影响

本试验旨在研究饲粮中添加谷氨酰胺(Gln)对断奶仔猪不同阶段生长性能的影响,以及其对脂多糖(LPS)诱导肠道损伤后断奶仔猪血清生化指标和生长性能的影响。选用24头28日龄健康的"杜×长×大"三元杂交断奶仔猪,随机分为3组,每组8个重复,每个重复1头猪。对照组和LPS组饲喂基础饲粮,Gln+LPS组饲喂添加了1%的外源性Gln的基础饲粮;在试验第22、25、28、30天,LPS组和Gln+LPS组腹腔注射100μg/kg BW LPS,对照组则注射相同剂量的生理盐水。试验期30 d。结果表明:1)LPS处理前(试验第1~21天),与对照组相比,Gln+LPS组显著提高了试验第1~7天断奶仔猪的平均日采食量(ADFI)和平均日增重(ADG)(P0.05),显著提高了试验第8~14天和第1~21天断奶仔猪的ADFI(P0.05)。2)LPS处理后(试验第22~30天),对照组断奶仔猪的ADFI、ADG、第30天体重均显著高于LPS组和Gln+LPS组(P0.05),Gln+LPS组断奶仔猪的ADFI、ADG、第30天体重均高于LPS组(P0.05)。3)LPS组断奶仔猪的小肠长度显著低于对照组和Gln+LPS组(P0.05),而对照组和Gln+LPS组之间无显著差异(P0.05)。4)与对照组相比,Gln+LPS组断奶仔猪的血清高密度脂蛋白胆固醇(HDLC)含量和碱性磷酸酶(ALP)活性显著降低(P0.05),而Gln+LPS组与LPS组之间无显著差异(P0.05);Gln+LPS组和LPS组断奶仔猪的血清免疫球蛋白M(Ig M)含量显著提高(P0.05)。由此可见,饲粮中添加1%的Gln能够显著提高仔猪断奶后第1~7天的生长性能,之后效果不明显。饲粮中添加1%的Gln能够调节应激仔猪的血清生化指标,改善其生长性能和小肠长度,从而缓解仔猪断奶应激。     

普通日粮添加小肽螯合锌对断奶仔猪生长性能和血液指标的影响

试验选用杜长大28日龄断奶仔猪90头,随即将仔猪分为3个处理,每个处理6个重复。试验所用基础日粮中的锌含量为100 mg/kg,锌以Zn SO4·H2O的形式加入,对照组饲喂基础日粮,其他2组分别在基础日粮中添加100mg/kg小肽螯合锌(以锌计)和3 000 mg/kg氧化锌(以锌计),研究小肽螯合锌对断奶仔猪生长性能和血液指标的影响。试验结果表明:与Zn SO4比较,添加小肽螯合锌和高氧化锌组显著提高了ADG和ADFI(P0.05);血清锌浓度小肽螯合锌组与硫酸锌组差异极显著(P0.01);小肽螯合锌对血清Ig G含量和血清ALP活性较硫酸锌组有显著性提高(P0.05)。因此,日粮中添加低剂量的小肽螯合锌能够达到与添加高剂量的氧化锌相同的效果。     

酵母蛋白饲料和鱼粉对断奶仔猪生产性能影响的比较研究

试验采用单因子设计,在保证营养水平相同的情况下,共设5种日粮,其中包括对照组(基础日粮)、鱼粉组(基础日粮+2.5%鱼粉)、酵母组(基础日粮+2.5%酵母)、酵母去酶组(基础日粮+2.5%酵母并扣除酶制剂)和酵母去药组(基础日粮+2.5%酵母并扣除抗生素)。选用28日龄断奶的DLY三元杂交仔猪60头,试验期为28d。试验主要考察平均日采食量(ADFI)、平均日增重(ADG)和料肉比(F/G)。结果表明,从整个试验期来看,添加酵母组和鱼粉组都能提高仔猪的生产性能,尤以酵母组的提高幅度最大,酵母组的ADG、ADFI分别较对照组提高14.9%(P<0.05)、4.2%,料肉比降低了9.5%(P<0.05);ADG、ADFI分别较鱼粉组提高10.6%、5.4%,料肉比降低4.7%(P<0.05)。通过比较对照组、鱼粉组、酵母去酶组、酵母去药组这4组全期生产性能指标,发现对照组虽然采食量较高,但ADG和料肉比仍是最差,其中料肉比明显高于酵母去酶组和鱼粉组(P<0.05);酵母去酶组较对照组ADG提高6.4%,料肉比降低11.9%(P<0.05);酵母去药组较对照组ADG提高1.7%,料肉比降低2.0%,差异不显著(P>0.05)。试验结果说明,酵母代替鱼粉的效果是肯定的,同时具有替代酶制剂的潜力,另外,酵母饲料作为一种绿色的饲料来源,在一定条件下代替抗生素也是可行的。     

酵母核酸对断奶仔猪生产性能的影响

本试验旨在考察酵母核酸对断奶仔猪生长性能的影响.选用健康断奶仔猪96头,分为两个处理组(即对照组和试验组),每个处理组4个重复,每个重复1栏,每栏12头.对照组饲喂基础日粮,试验组在基础日粮中额外添加0.5％福邦酵母核酸,试验期28 do试验结果:试验组显著提高了断奶仔猪的平均日增重(ADG)(P＜0.05),平均采食量(ADFl)也有明显的提高趋势;与对照组相比,试验组ADG和ADFI分别提高了8.78％和5.27％,同时降低了仔猪饲料系数3.33％.结果提示,饲粮中额外添加0.5％酵母核酸能够增加断奶仔猪采食量,提高生长速度.     

含胆囊收缩素抗体卯黄粉对断奶仔猪生产性能及养分消化率的影响

本试验旨在研究含胆囊收缩素(CCK)抗体卵黄粉对断奶仔猪生产性能、日粮养分消化率及血清CCK浓度的影响.90头(30±2)日龄断奶约克仔猪[平均体重(7.05±0.20)kg]随机分为5个处理,分别饲喂基础日粮和基础日粮中添加100、200、300 mg/kg和400 mg/kg含CCK抗体卵黄粉的试验日粮,每个处理6个重复,每个重复3头仔猪.试验期28 d.结果表明,与基础日粮组相比,添加含CCK抗体卵黄粉可提高仔猪全期平均日增重(ADG)和平均日采食量(ADFI),降低料内比(F/G),其中200 mg/kg组ADG提高12.14%(P＞0.05),ADFI提高6.92%(P＞0.05),F/G降低4.62%(P＞0.05).同时,日粮粗蛋白质消化率随含CCK抗体卵黄粉添加量的增加呈二次曲线变化(P=0.044).添加含CCK抗体卵黄粉后,仔猪血清CCK浓度下降,200 mg/kg组降低35.6%(P＞0.05).综合来看,添加200 mg/kg 含CCK抗体卵黄粉组效果最好.     

酵母提取物对断奶仔猪生产性能的影响

试验考察了酵母提取物对断奶仔猪生长性能的影响.试验选用21日龄断奶仔猪80头,随机分为对照组和试验组两个处理组,每组4个重复,每个重复1栏,每栏10头.对照组饲喂基础日粮,试验组在基础日粮中额外添加0.5%啤酒酵母提取物,饲喂期28 d.结果显示,日粮中额外添加酵母提取物试验组显著提高了断奶仔猪平均日增重(ADG)(P<0.05),同时平均日采食量(ADFI)有明显的提高趋势.与对照组相比,添加酵母提取物试验组ADG和ADFI分别提高11.98%和5.85%,同时仔猪腹泻率降低了40.10%,仔猪料肉比(F/G)降低5.40%.试验结果表明,饲粮中额外添加0.5%酵母提取物能够增加断奶仔猪采食量,提高生长性能.     

博落回提取物对断奶仔猪生长性能、血清免疫指标及抗氧化指标的影响

本试验旨在研究博落回提取物对断奶仔猪生长性能、血清免疫指标及抗氧化指标的影响,选择120头35日龄的健康杜×长×大三元杂交断奶仔猪,按体重相近、性别比例相同原则随机分成2组,每组5个重复,每个重复12头猪,预饲期5d,试验期30d,对照组饲喂基础日粮,试验组饲喂添加0.1%博落回提取物的基础日粮。试验期间,测定每组仔猪的平均日增重(ADG)、平均日采食量(ADFI)及料重比(F/G);在试验结束时,每个重复选取2头仔猪采血测定血清免疫指标及抗氧化指标。结果显示:(1)添加博落回提取物组断奶仔猪ADG较对照组提高3.89%(P0.05),F/G下降4.32%(P0.05),且腹泻率较对照组有显著降低的趋势(P=0.076)。(2)日粮中添加博落回提取物显著提高了断奶仔猪血清中免疫球蛋白G(IgG)和肿瘤坏死因子-α(TNF-α)的含量(P0.05),血清IgA及IgM含量分别较对照组提高了4.59%和4.60%(P0.05)。(3)日粮中添加博落回提取物可显著降低断奶仔猪血清中丙二醛(MDA)含量(P0.05),同时显著提高总超氧化物歧化酶(T-SOD)活性(P0.05)。综上所述,在日粮中添加0.1%博落回提取物可降低断奶仔猪腹泻率,并提高机体免疫力及抗氧化能力,且对断奶仔猪生长性能无不良影响。     

酵母提取物替代喷雾干燥血浆蛋白粉对断奶仔猪生长性能的影响

试验旨在研究酵母提取物(yeast extract,YE)部分或全部替代喷雾干燥血浆蛋白粉(spray-dried plasma protein,SDPP)对断奶仔猪生长性能和腹泻指数的影响。试验选用160头体重[(8.32±0.50)kg]和日龄[(30±2)d]相近的PIC断奶仔猪。采用单因子完全随机试验设计,分为4个处理,每个处理5个重复,每个重复8头仔猪,分别饲喂基础日粮(处理1)、含3%SDPP的日粮(处理2)、含1.5%SDPP+1.5%YE的日粮(处理3),含3%YE的日粮(处理4)。试验期14 d,所有仔猪自由采食和饮水。结果表明:试验第1周,饲喂含1.5%SDPP+1.5%YE日粮的仔猪平均日采食量(average dai-ly feed intake,ADFI)显著高于对照组仔猪(15%,P0.05),平均日增重(average daily gain,ADG)显著高于对照组和3%SDPP组仔猪(12%~22%,P0.05);料肉比(the ratio of feed to body weight gain,F/G)显著低于对照组和3%SDPP组仔猪(6%~8%,P0.05)。试验全期,饲喂含1.5%SDPP+1.5%YE日粮的仔猪ADFI和ADG显著高于对照组和3%YE组仔猪(P0.05),且料肉比显著低于对照组和3%SDPP组仔猪(5%~6%,P0.05);同时,3%YE组仔猪ADFI和ADG与对照组及3%SDPP组仔猪差异不显著。因此,本试验条件下,采用3%酵母提取物替代3%喷雾干燥血浆蛋白粉并不会影响仔猪生长性能,且部分替代喷雾干燥血浆蛋白粉有改善仔猪采食量、日增重和料肉比的效果。     

Effects of organic forms of zinc on growth performance,tissue zinc distribution,and immune response of weanling pigs

This study was conducted to determine the effect of zinc level and source on growth performance, tissue Zn concentrations, intracellular distribution of Zn, and immune response in weanling pigs. Ninety-six 3-wk-old crossbred weanling pigs (BW = 6.45 +/- 0.17 kg) were assigned to one of six dietary treatments (four pigs per pen, four replicates per treatment) based on weight and litter origin. Treatments consisted of the following: 1) a corn-soybean meal-whey diet (1.2% lysine) with a basal level of 80 ppm of supplemental Zn from ZnSO4 (control; contained 104 ppm total Zn); 2) control + 80 ppm added Zn from ZnSO4; 3) control + 80 ppm added Zn from Zn methionine (ZnMet); 4) control + 80 ppm added Zn from Zn lysine (ZnLys); 5) control + 40 ppm added Zn from ZnMet and 40 ppm added Zn from ZnLys (ZnML); and 6) control + 160 ppm added Zn from ZnSO4. Zinc supplementation of the control diet had no effect on ADG or ADFI. Gain efficiency was less (P < 0.05) for pigs fed 80 ppm of Zn from ZnSO4 than for control pigs and pigs fed 160 ppm of Zn from ZnSO4. Organ weights, Zn concentration, and intracellular distribution of Zn in the liver, pancreas, and spleen were not affected (P = 0.12) by Zn level or source. Skin thickness response to phytohemagglutinin (PHA) was not affected (P = 0.53) by dietary treatment. Lymphocyte proliferation in response to PHA was greater (P < 0.05) in pigs fed ZnLys than in pigs fed the control diet or the ZnML diet; however, when pokeweed mitogen was used, lymphocyte proliferation was greatest (P < 0.05) in pigs fed the ZnMet diet than pigs fed the control, ZnLys, ZnML, or 160 ppm ZnSO4 diets. Antibody response to sheep red blood cells was not affected by dietary treatments. Supplementation of 80 ppm of Zn from ZnSO4 or ZnMet and 160 ppm of Zn from ZnSO4 decreased (P < 0.05) the antibody response to ovalbumin on d 7 compared with control pigs, but not on d 14. Phagocytic capability of peritoneal exudate cells was increased (P < 0.05) when 160 ppm of Zn from ZnSO4 was supplemented to the diet. The number of red blood cells ingested per phagocytic cell was increased (P < 0.05) in pigs fed the diet supplemented with a combination of ZnMet and ZnLys and the diet with 160 ppm of Zn from ZnSO4. Results suggest that the level of Zn recommended by NRC for weanling pigs was sufficient for optimal growth performance and immune responses, although macrophage function may be enhanced at greater levels of Zn. Source of Zn did not alter these measurements.     

Zinc-amino acid complexes for swine

Two experiments were conducted to determine the effect of sources of dietary zinc on gain, feed conversion and blood and bone traits of swine. In the first experiment 96 pigs were used in a 28-d study. The pigs were fed diets with no supplemental Zn or with either 9 or 12 ppm supplemental Zn from zinc sulfate (ZnSO4), zinc methionine (ZnMet) or zinc methionine with picolinic acid (ZnMet w/PA), each with or without 5% added corn oil. There were differences (P less than .05) in average daily gain (ADG) and average daily feed intake (ADFI) between the pigs fed the two organic Zn sources, with those fed ZnMet w/PA showing the better gains and feed conversion. However, neither organic Zn source resulted in pig performance that was different from either the diet with no supplemental Zn or the diets supplemented with Zn from ZnSO4. In the second experiment the same dietary Zn sources and treatments were fed as in Exp. 1 except that corn oil was deleted as a variable. No differences in ADG, ADFI, feed/gain (F/G) or in changes in serum Zn or Cu were observed among treatments during either the 21-d nursery or the 56-d growing periods. During the subsequent 56-d finishing period ADG and ADFI were greater (P less than .01) for pigs fed the Zn-supplemented diets than for those fed the diets without supplemental Zn. There were no differences among treatments in F/G during the finishing period. Zn content of bone ash was lower (P less than .01) in the non-Zn-supplemented pigs. These data suggest that the Zn sources used are of similar biological value and do not support the theory that picolinic acid aids Zn absorption.     

Growth and intestinal morphology of pigs from sows fed two zinc sources during gestation and lactation

An experiment was conducted to compare the effects of organic (Zn AA complex, ZnAA) and inorganic Zn (ZnSO4) sources on sows and their progeny during gestation and lactation and on the pigs during the nursery period. The dietary treatments were 1) a corn-soybean meal diet with 100 ppm Zn from ZnSO4 (control); 2) diet 1 + 100 ppm additional Zn from ZnSO4; and 3) diet 1 + 100 ppm additional Zn from ZnAA. Dietary additions were on an as-fed basis. Thirty-one primaparous and multiparous sows were allotted to the treatment diet beginning on d 15 of gestation and continuing through lactation. At weaning (d 17 of age), 202 pigs (63, 55, and 84 pigs for treatments 1 to 3, respectively) were allotted to the same dietary treatment as their dam. The pigs were fed a 3-phase diet regimen during the nursery period: d 0 to 7 (phase I); d 7 to 21 (phase II); and d 21 to 28 (phase III). At weaning and at the end of phase III, 1 gilt per replicate was killed, and the left front foot, liver, pancreas, and entire small intestine were removed. Diet had no effect (P > 0.10) on any response during gestation. During lactation, there was an increase (P < 0.10) in litter birth weight in sows fed ZnAA compared with those fed the control or ZnSO4 diets. The sows fed ZnAA nursed more pigs (P < 0.10) than sows fed the ZnSO4 diet, and they weaned more pigs (P < 0.05) than sows fed the control diet. Jejunal villus height of the weaned pigs from sows fed ZnSO4 was increased (P < 0.05) compared with those from the sows fed the control diet. During the nursery period, growth performance was not affected (P > 0.10) by diet. Pigs fed ZnSO4 had greater duodenal villus width (P < 0.05) than those fed ZnAA, and pigs fed ZnSO4 or the control diet had greater ileal villus width (P < 0.05) than those fed ZnAA. Pigs fed ZnSO4 or ZnAA had more (P < 0.05) bone Zn than those fed the control diet. Liver Zn concentration was greatest in pigs fed ZnSO4, followed by those fed ZnAA, and then by those fed the control diet (P < 0.05). Pancreas Zn was increased (P < 0.05) in pigs fed ZnSO4 compared with those fed the control diet. These results suggest that 100 ppm Zn in trace mineral premixes provides adequate Zn for optimal growth performance of nursery pigs, but that 100 ppm additional Zn from ZnAA in sow diets may increase pigs born and weaned per litter.     

不同锌源对猪早期生长及其相关基因表达的影响

利用不同的锌源饲喂早期断奶仔猪,研究其对仔猪早期生长的影响,并从激素水平及基因表达上探讨其可能的作用机制。选取28d断奶的猪45头,随机分为3组,每组设3个重复,每重复5头,对照组饲喂基础日粮（含锌101mg／kg）,另外2组分别添加硫酸锌组（ZnSO4）、蛋氨酸锌组（Zn—Met）使日粮含锌240mg／kg。结果表明：日粮中添加不同形式的锌,均能显著提高仔猪日增重和胰岛素生长因子-Ⅰ（IGF—Ⅰ）基因表达量（P〈0．05）,蛋氨酸锌组IGF—ⅠmRNA表达量显著高于硫酸锌组（P〈0．05）;而对猪血浆生长激素（GH）水平及其生长激素受体（GHR）表达影响均不显著。表明添加锌可以通过IGF—Ⅰ对生长的调控作用而影响机体生长发育。     

Evaluation of the importance of centrifugation as a component of zinc sulfate fecal flotation examinations

Fifty canine fecal samples were evaluated by five flotation procedures to compare the sensitivity of the zinc sulfate (ZnSO4) centrifugation flotation test with ZnSO4 flotation tests using benchtop incubation during the flotation period. One or more parasite species were detected in 40 samples. Results showed that centrifugation with ZnSO4 solution was significantly more likely to detect a positive sample than benchtop procedures. The difference in procedures was due primarily to increased detection of Trichuris eggs and Giardia cysts by centrifugal flotation. No significant difference was seen in the ability of benchtop procedures to detect positive samples when tests sat either for 5 or 10 minutes before examination.     

有机锌源对肉鸡生长性能和胫骨软骨症的影响

采用玉米－豆饼型饲粮研究有机锌源对肉鸡生长性能和胫骨软骨症（ＴＤ）的影响。结果表明,有机锌源与硫酸锌对肉鸡生长和饲料采食量均无显著影响,锌的补加提高了胫骨,中趾骨,胰Ｚｎ含量,有机锌源的补加并不影响骨灰含量,胫骨长度,不诱导肉鸡ＴＤ发病率上升。     

Effects of supplemental zinc concentration and source on performance, carcass characteristics, and serum values in finishing beef steers

Three studies were conducted to examine the effects of zinc concentration or source in diets of finishing beef steers. In Exp. 1, 108 (British x Continental) beef steers were supplemented with concentrations of added zinc (as ZnSO4) at 20, 100, or 200 mg/kg of dietary DM. No differences (P > 0.10) were noted among treatments for ADG or gain:feed for the 112-d finishing period. However, a linear (P < 0.10) decrease was noted in daily DMI with increasing zinc concentrations for the overall finishing period. No differences (P > 0.10) were noted in hot carcass weight; dressing percentage; longissimus muscle area; percentage of kidney, pelvic, and heart fat; or marbling score. There were, however, quadratic increases in s.c. fat thickness (P < 0.05) and yield grade (P < 0.01) with added zinc. In Exp. 2, 12 beef steers were used to examine effects of added dietary zinc on serum concentrations of cholesterol and fatty acid profiles. No differences (P > 0.10) were observed in cholesterol or fatty acids among the supplemental zinc levels. In Exp. 3, 84 Brangus- and Angus-sired steers were fed a steam-flaked corn-based diet containing 30 mg of supplemental zinc per kilogram of dietary DM from one of the following sources: 1) ZnSO4, 2) Zn amino acid complex, or 3) a zinc polysaccharide complex. No differences (P > 0.10) were noted for the overall 126-d trial for ADG, DMI, or gain:feed ratio. Percentage kidney, pelvic, and heart fat was increased (P < 0.10) in steers supplemented with ZnSO4 vs the average of Zn amino acid and Zn polysaccharide complexes. However, s.c. fat thickness was greater (P < 0.10) in steers supplemented with Zn amino acid and Zn polysaccharide complexes vs ZnSO4. Serum zinc concentration did not differ (P > 0.10) among zinc sources. Supplemental zinc concentration in finishing diets did not seem to influence feedlot performance and had a minimal impact on carcass quality. Either the organic or inorganic source can be included in finishing diets without affecting feedlot performance.     

Zinc bioavailability in feed-grade sources of zinc

Chick bioassays were used to assess bioavailability of zinc (Zn) from inorganic Zn sources. A soy isolate-dextrose diet containing 13 mg Zn/kg diet was supplemented with feed-grade sources of ZnSO4.H2O (ZnSO4) or ZnO and fed for 2 wk after a 7-d Zn-depletion protest period. Bioavailability of Zn in ZnO relative to ZnSO4 (set at 100%) was determined by multiple regression slope-ratio methodology, using both growth and tibia Zn accumulation in chicks fed graded levels of ZnO and ZnSO4. Linear responses for gain and tibia Zn occurred at dietary Zn levels (ZnSO4.7H2O) between 13 mg/kg (basal) and 33 mg/kg (gain) or 53 mg/kg (total tibia Zn). Therefore, two bioavailability assays were conducted using supplemental Zn levels of 0, 7.5 and 15 mg/kg from each Zn source. When weight gain was regressed on supplemental Zn intake, bioavailability of Zn in ZnO was only 61.2% (P less than .01) that of ZnSO4. When total tibia Zn was regressed on supplemental Zn intake, bioavailability of Zn compared with ZnSO4 (set at 100.0%) was 44.1% (P less than .001) for ZnO. With chicks fed soy-based diets, bioavailability of Zn from ZnO was less than that of ZnSO4.     

Bioavailability of zinc in several sources of zinc oxide, zinc sulfate, and zinc metal.

Three zinc depletion-repletion assays were carried out with chicks to determine Zn bioavailability in five sources of ZnO, three sources of ZnSO4.H2O, and two sources of Zn metal. A standard 23% CP corn-soybean meal diet was fed during the first 3 d posthatching, after which it was replaced with a Zn-deficient soy concentrate diet (13.5 mg Zn/kg) until d 7. On d 8 after an overnight period of feed withdrawal, chicks were fed for 12 d the Zn-deficient basal diet containing 0, 4.76, and 9.90 (Assay 1); 0, 5.06, or 10.12 (Assay 2); or 0, 4.73, or 9.13 (Assay 3) mg/kg supplemental Zn from analytical grade (AG) ZnSO4.7H2O (22.7% Zn) to generate a standard response curve. The AG and feed-grade (FG) Zn sources being evaluated were then provided at a level that would fall within the standard curve. Weight gain (Assays 1, 2, and 3) and total tibia Zn (Assay 1) responded linearly (P<.01) to Zn supplementation from ZnSO4.7H2O. Weight gain regressed on supplemental Zn intake gave standard-curve equations with fits (r2) ranging from .94 to .97. In Assay 1, regression of total tibia Zn (Y, in micrograms) on supplemental Zn intake (X, in milligrams/12 d) gave the equation Y = 13.2+6.74X (r2 = .90). Standard-curve methodology was used to estimate relative Zn bioavailability (RBV), with RBV of Zn in the ZnSO4.7H2O standard set at 100%. Four sources of FG ZnO were evaluated: Source 1 (78.1% Zn, hydrosulfide process, U.S.), Source 2 (74.1% Zn, Waelz process, Mexico), Source 3 (69.4% Zn, China), and Source 4 (78.0% Zn, French process, Mexico). Analytical-grade ZnO (80.3% Zn) was also evaluated. Feed-grade ZnO Sources 1 and 4 as well as AG ZnO produced average RBV values that were not different (P>.10) from the standard, but average RBV values for FG Source 2 and FG Source 3 were only 34 (P<.05) and 46% (P<.05), respectively. All sources of ZnSO4.H2O, which included two FG sources (source 1, 36.5% Zn; source 2, 35.3% Zn) and one food-grade source (36.5% Zn), were not different (P>.10) in RBV from the ZnSO4.7H2O standard. Two Zn metal products, Zn metal dust (100% Zn) and Zn metal fume (91.5% Zn), were also evaluated, and they were found to have Zn RBV values of 67 (P<.05) and 36% (P<.05), respectively. Feed-grade sources of ZnO vary widely in color, texture, Zn content, and Zn bioavailability.     

Assessment of dietary zinc requirement of weaned piglets fed diets with or without microbial phytase

Fifty-four pigs, weaned at 26 days of age at an average body weight of 7.74 kg were used in a 26-day experiment to assess the zinc requirement of piglets, using diets based on maize and soybean meal, with or without microbial phytase. The nine experimental diets were the basal diet containing 33 mg of zinc/kg supplemented with 10, 25, 40, 60 or 80 mg of zinc as sulphate (ZnSO(4), 7H(2)O)/kg and the basal diet supplemented with 0, 10, 25 or 40 mg of zinc as sulphate/kg and 700 units (U) of microbial phytase (Natuphos)/kg. Pigs were fed the basal diet for a 7-day adjustment period prior to the 19-day experimental period. Microbial phytase enhanced plasma alkaline phosphatase (AP) activity, plasma zinc and bone zinc concentrations. These parameters increased linearly with zinc intake, with a similar slope with and without phytase. The response of bone zinc-to-zinc added did not plateau. Without microbial phytase, plasma AP activity and zinc concentration were maximized when dietary zinc reached 86 and 92 mg/kg respectively. With microbial phytase they were maximized when dietary zinc concentration reached 54 and 49 mg/kg respectively. Accounting for a safety margin, the recommended supply of zinc for weaned piglets up to 16 kg fed maize-soybean meal diets supplemented with zinc as sulphate is thus of 100-110 mg/kg diet. This supply may be reduced by around 35 mg if the diet is supplemented with 700 U of microbial phytase.