The course of phosphorus excretion in growing pigs fed continuously increasing phosphorus concentrations after a phosphorus depletion.

A balance study was performed in order to quantify the effect of continuously increased phosphorus (P) intake on faecal and urinary P excretion. The aim was to quantify the level of intake where regulatory P excretion becomes relevant for comparative digestibility measurements on P, and when the pig adapts its urinary P excretion to increased P intake. Phosphorus intake of growing pigs was continuously increased on a daily basis starting at a marginal level and P excretion via faeces and urine was continuously followed for 92 days. Two semi-synthetic diets were prepared with different proportions of Na2HPO4 resulting in 2.4 (diet 1) and 6.3 (diet 2) g P/kg DM. Concentration of Ca was adapted to achieve a Ca supply approximately 3.1 fold the digestible P supply. Six castrated male crossbred pigs (31 kg BW) were kept individually in metabolism crates after they had undergone a 14 d P depletion period during which they were fed diet 1 solely. Pigs received 1.04kg of diet 1 per day throughout the experiment, and each day the amount of feed and P supplied to pigs from diet 2 was increased by 12 g and 69 mg, respectively. ME supply was approximately 2.4 fold maintenance and average daily BW gain of pigs during the entire experiment was 690 +/- 30 g. While intake increased linearly, faecal excretion of P and Ca increased non-linearly and could be best described by third order polynomial functions. The proportion of ingested P not excreted via faeces followed a quadratic type of curve with a maximum of 81% at 25 days on experiment and P intake of 4.0 g/d. Thereafter, the proportion decreased continuously. The digestibility of P from diet 2, determined by the slope ratio technique, was constant and not affected by P intake up to a P intake of 5 g/d. Renal P excretion did not exceed inevitable losses until day 60 and increased exponentially thereafter when body P reserves were restored. It is concluded, that an adaptation to surplus P supply occurred earlier on the intestinal than on the renal level. While faecal P excretion appeared regulated depending on the actual requirement for P retention, the regulation via urine depended on the P status of the pig. Once the renal P excretion of growing pigs exceeds a level of 25 mg/d, intake of digestible P cannot be regarded sufficiently low to measure P digestibility as a capacity of the feedstuff.     

Effects of zinc levels on activities of gastrointestinal enzymes in growing rats

The present study investigated the effect of different zinc (Zn) levels on activities of gastrointestinal digestive enzymes of growing rats. Four diets including Zn‐adequate (ZA; 46 mg/kg, control), Zn‐deficient (ZD; 3 mg/kg), high Zn supply (ZH; 234 mg/kg) and pair‐fed in which animals received the ZA diet at restricted amounts reflecting feed intake of the ZD group were fed to rats for 5 weeks. Dietary Zn was supplemented with ZnO. The results showed that Zn deficiency resulted in decreases in body weight, while ZH supply stimulated growth. The activities of sucrase, lactase and lipase were unaffected by dietary Zn levels. Maltase activity, however, was reduced in ZD group and elevated in ZH group. Amylase and protease activities were depressed by zinc deficiency. However, rats fed the Zn‐repletion diet displayed higher activity of pepsin, pancreatic amylase and protease. In particular, ZH supply did have no effect on intestinal hydrolases activities. The present study suggested that zinc deficiency impaired the activities of digestive enzymes and growth of animals. However, ZH supply might improve the digestion of nutrients via increasing activities of gastrointestinal hydrolase and probably enhanced animal health.     

Nano-sized Zinc in Broiler Chickens: Effects on Growth Performance,Zinc Concentration in Organs,and Intestinal Morphology

The effects of dietary supplementation of zinc (Zn) sources and concentrations were investigated on growth performance, absorption into tissues, fecal excretion, nutrient retention, and intestinal morphology in broilers fed a corn-soybean meal basal diet. A total of 525 one-day-old chicks (Ross 308) were assigned based on body weight to seven dietary treatments. There were five replicate pens for each treatment and 15 broilers per replicate pen. The dietary treatments included a basal diet (control, without supplementing Zn), and basal diet supplemented with Zn, as inorganic zinc sulfate (ZnS; 110 mg/kg); organic Zn-methionine (ZnM; 110 mg/kg); hot-melt extruded (HME) 25 zinc sulfate (27.5 mg/kg); HME50 zinc sulfate (55 mg/kg); HME75 zinc sulfate (82.5 mg/kg); or HME100 zinc sulfate (110 mg/kg) for 35 days in two phases (d 1–21, phase I and d 22–35, phase II). Bodyweight and feed efficiency of broiler chicks fed diets supplemented with increasing dietary concentrations of HME-Zn improved linearly during the study period (P<0.05). Compared to the control treatment, the ZnS, ZnM, and HME diets increased Zn concentrations in the serum and liver. Inorganic ZnS supply resulted in the highest Zn concentration in excreta. Increasing supplemented Zn content in diets as HME linearly increased Zn concentration in the excreta, serum, liver, and tibia. Broiler chicks fed diets supplemented with increasing concentrations of HME increased villus height (VH; linear and quadratic) of the jejunum and VH of the ileum (linear). Increasing concentrations of dietary Zn supplied as HME resulted in linearly enhanced dry matter, gross energy, and nitrogen retention of broilers on day 21. These results suggest that dietary HME-Zn at a lower level (55 ppm) shows the same growth performance as common ZnSO₄ at 110 ppm.     

Effects of diets supplemented with zinc and manganese on performance and related parameters in laying hens‡

Iron is often found to be of excessive concentrations in laying hens' diets, which may cause antagonistic interactions with other minerals. This study was conducted to investigate how to supplement Zn and Mn in the diets without Fe supplementation. In experiment 1, 420 18‐week Lohmann Brown layers were fed a basal diet or a basal diet supplemented with 30–0, 65–30 and 100–60 mg/kg of Zn and Mn, respectively. In experiment 2, 360 40‐week Lohmann Brown layers were fed a basal diet or a basal diet supplemented with 15–0, 35–0 and 55–15 mg/kg of Mn and Zn, respectively. Minerals were supplemented in the form of sulfate. Egg production was improved by supplementing 30 mg/kg Zn or 65 mg/kg Zn in combination with 30 mg/kg Mn in experiment one. In experiment two, a significant reduction of egg performance occurred with 35 mg/kg Mn supplementation. Mn and/or Zn supplementation increased eggshell thickness in experiment one, and decreased yolk cholesterol in both experiments. Mn and/or Zn supplementation increased Zn and Mn excretion in both experiments. Serum growth hormone (GH), thyroxine (T₄), and insulin levels, or alkaline phosphatase (AP) activity were not affected by treatments; serum estrogen (E₂) and triiodothyronine (T₃) were different but there was no consistency by dietary treatments. This study demonstrates that 30 mg/kg supplemental Zn is necessary to obtain maximal egg production, and there seems to be no need to supply Mn in this type of diet.     

22～42日龄肉鸡铜、铁、锌、锰不同用量组合的研究

本试验旨在研究饲粮中铜、铁、锌、锰含量对22~42日龄肉鸡生长性能和粪中铜、铁、锌、锰排泄量的影响,进而对微量元素的平衡模式进行探讨。选取940只1日龄爱拔益加(AA)肉公鸡,1~21日龄统一饲喂铜、铁、锌、锰含量分别为16.96、166.66、46.01、60.26 mg/kg的玉米-豆粕型饲粮。试验选用22日龄、体况良好、体重接近的AA肉公鸡900只,随机分为15组,每组6个重复,每个重复10只鸡。对照组饲喂基础饲粮,基础饲粮中铜、铁、锌、锰含量分别为8、125、40、60 mg/kg,试验组饲喂在基础饲粮中按照均匀设计原则添加2~8 mg/kg铜、10~35 mg/kg铁、10~40 mg/kg锌、15~60 mg/kg锰组成的14种试验饲粮。测定肉鸡试验期生长性能,并于38~42日龄时采集粪样测定铜、铁、锌、锰含量。结果表明:1)饲粮铜、铁、锌、锰含量在NRC推荐量至2倍NRC推荐量范围时,对22~42日龄肉鸡的平均日增重(ADG)和料重比(F/G)无显著影响(P0.05)。2)由最优解分析得出,粪中铜排泄量最低为23.11 mg/kg时,饲粮铜、铁、锌、锰含量分别为7.15、116.28、82.82、60.95 mg/kg;铁排泄量最低为438.34 mg/kg时,饲粮铜、铁、锌、锰含量分别为14.78、116.81、38.15、63.72 mg/kg;锌排泄量最低为102.60 mg/kg时,饲粮铜、铁、锌、锰含量分别为7.69、127.40、40.70、133.26 mg/kg;锰排泄量最低为159.37 mg/kg时,饲粮铜、铁、锌、锰含量分别为11.07、136.97、46.13、59.05 mg/kg;粪中铜、铁、锌、锰总排泄量最低为218.94 mg/kg时,饲粮铜、铁、锌、锰含量分别为7.36、125.74、38.23、62.76 mg/kg。综上所述,饲粮铜、铁、锌、锰含量在NRC推荐量至2倍NRC推荐量范围时对22~42日龄肉鸡的生长性能无显著影响;粪中铜、铁、锌、锰任一元素的排泄量均受饲粮中其他微量元素添加量的影响,且针对不同元素最低排泄量存在不同的最佳组合;饲粮铜、铁、锌、锰的含量分别为7.36、125.74、38.23、62.76 mg/kg时,能够满足肉鸡微量元素需要量,同时粪中铜、铁、锌、锰总排泄量最小。     

Nitrogen metabolism in crossbred steers with varying levels of Brahman using a nitrogen depletion-repletion regimen

Nine N metabolism trials were conducted in a N-depletion-repletion regimen using five breed crosses of steers with 0, 25 or 50% Brahman. Three steers from each breed cross (avg initial wt 239 kg) were standardized for 3 wk on an 18% protein diet and depleted for 5 wk on a 7.5% protein diet and then repleted for 4 wk on the 18% protein diet. Nitrogen balance and blood and urinary N metabolites were monitored to determine changes in metabolic status due to changes in dietary N intake. Reduced N intake during the depletion period almost completely inhibited fiber digestion (P less than .01), while ruminal ammonia concentration fell from an average concentration of 156 during standardization to 22 mg/liter (P less than .01) during depletion. Organic matter digestion was depressed (P less than .05) due to the reduced fiber digestion. Absolute amounts of intake, fecal, urinary, absorbed and retained N were severely depressed during depletion. Apparent digestibility of N was reduced from an average of 68% during standardization to 42% (P less than .05) during depletion, but truly digested N was not affected. Nitrogen retained, as a percentage of intake, or absorbed was reduced only during the first week of depletion. Urea N comprised the major identified urinary fraction during standardization and repletion, whereas creatinine was the major fraction during depletion. Brahman-cross steers excreted more urinary N (P less than .1) and retained less N (P less than .13) during repletion than Angus X Hereford steers. Creatinine excretion was also higher (P less than .01) during depletion for Brahman-cross steers. Blood urea and albumin N concentrations were higher (P less than .05) during both depletion and repletion among Brahman crosses. These experiments suggest that blood measurements were more sensitive than N balance to changes in dietary N state and that faster recharge of blood N measurements in Brahman cattle may help mitigate adverse effects of N depletion stress.     

Influence of different dietary zinc levels on cashmere growth,plasma testosterone level and zinc status in male Liaoning Cashmere goats

The experiment was conducted to investigate the influence of different levels of zinc (Zn) on cashmere growth, plasma testosterone and Zn profile in male Cashmere goats. Twenty‐eight male Liaoning Cashmere goats, 3 years old and body weight at 56.2 ± 2.45 kg, were assigned to four groups. The animals were fed a basal diet containing of 45.9 mg Zn/kg dry matter (DM) basis and supplemented with 0, 20, 40 or 80 mg Zn (reagent grade ZnSO₄·7H₂O) per kg DM for 90 days. There was no significant effect on growth and diameter of cashmere fibre for Zn supplemented in diets. However, the length and growth rate of wool were improved (p < 0.05) with dietary Zn. The length and growth rate of wool were higher (p < 0.05) for the groups supplemented with 40 or 80 mg Zn/kg DM compared with that of 20 mg Zn/kg DM treatment group. Plasma testosterone concentration was increased for Zn supplemented in diets, and the testosterone concentration was higher (p < 0.05) in goats fed on the diet supplemented with 40 or 80 mg Zn/kg DM compared with those fed on basal diet. Plasma Zn concentrations increased (p < 0.05) with increasing dietary Zn and supplemented with 40 and 80 mg Zn/kg DM groups improved plasma Zn concentration (p < 0.05) more than 20 mg Zn/kg DM group. Fibre Zn content was higher (p < 0.05) in groups supplemented with 40 or 80 mg Zn/kg DM compared with control group, but no difference between Zn‐supplemented groups (p > 0.05). The activity of plasma alkaline phosphatase was increased (p < 0.05) due to dietary Zn supplementation; however, no difference was found between supplemented treatment groups (p > 0.05). In conclusion, Zn content (45.9 mg Zn/kg DM) in control diet was insufficient for optimal wool growth performance, and we recommended the level of dietary Zn for such goats is 86 mg/kg DM during the breeding season and cashmere fibre growing period.     

Nano-sized zinc addition enhanced mammary zinc translocation without altering health status of dairy cows

This study aimed to evaluate role of nano-sized zinc (Zn) on lactation performance, health status, and mammary permeability of lactating dairy cows. Thirty multiparous dairy cows with similar days in milk (158 ± 43.2) and body weight (694 ± 60.5 kg) were chosen based on parity and milk production and were randomly assigned to 3 treatment groups: basal diet (control, 69.6 mg/kg of Zn adequate in Zn requirement), basal diet additional Zn-methionine (Zn-Met, providing 40 mg/kg of Zn), and basal diet additional nano-sized Zn oxide (nZnO, providing 40 mg/kg of Zn). The study lasted for 10 wk, with the first 2 wk as adaptation. Feed intake, milk yield and the related variables, and plasma variables were determined every other week. Blood hematological profiles were determined in the 8th week of the study. We found that feed intake, milk yield, and milk composition were similar across the 3 groups. The nZnO- and Zn-Met-fed cows had greater milk Zn concentrations in the milk (3.89 mg/L (Zn-Met) and 3.93 mg/L (nZnO)) and plasma (1.25 mg/L (Zn-Met) and 1.29 mg/L (nZnO)) than the control cows (3.79 mg/L in milk and 1.21 mg/L in plasma). The nZnO-fed cows had higher Zn concentrations in plasma but not in milk compared to Zn-Met-fed cows. The Zn appearance in milk was greater in nZnO-fed (area under curve during the first 4 h post-feeding for milk Zn: 16.1 mg/L) and Zn-Met-fed cows (15.7 mg/L) than in control cows (15.0 mg/L). During the first 4 h post-feeding, milk to blood Zn ratio was greater in nZnO-fed animals but lower in Zn-Met-fed cows compared with control cows. Oxidative stress-related variables in plasma, blood hematological profiles, and mammary permeability related variables were not different across treatments. In summary, lactation performance, Zn concentrations in milk and plasma, hematological profiles, mammary permeability were similar in cows fed nZnO and Zn-Met. We therefore suggested that nZnO feeding can improve Zn bioavailability without impairing lactation performance, health status, and mammary gland permeability in dairy cows.     

Effects of dietary zinc and iron supplementation on mineral excretion, body composition, and mineral status of nursery pigs

Two experiments were conducted to evaluate the effects of dietary Zn and Fe supplementation on mineral excretion, body composition, and mineral status of nursery pigs. In Exp. 1 (n = 24; 6.5 kg; 16 to 20 d of age) and 2 (n = 24; 7.2 kg; 19 to 21 d of age), littermate crossbred barrows were weaned and allotted randomly by BW, within litter, to dietary treatments and housed individually in stainless steel pens. In Exp. 1, Phases 1 (d 0 to 7) and 2 (d 7 to 14) diets (as-fed basis) were: 1) NC (negative control, no added Zn source); 2) ZnO (NC + 2,000 mg/kg as Zn oxide); and 3) ZnM (NC + 2,000 mg/kg as Zn Met). In Exp. 2, diets for each phase (Phase 1 = d 0 to 7; Phase 2 = d 7 to 21; Phase 3 = d 21 to 35) were the basal diet supplemented with 0, 25, 50, 100, and 150 mg/kg Fe (as-fed basis) as ferrous sulfate. Orts, feces, and urine were collected daily in Exp. 1; whereas pigs had a 4-d adjustment period followed by a 3-d total collection period (Period 1 = d 5 to 7; Period 2 = d 12 to 14; Period 3 = d 26 to 28) during each phase in Exp. 2. Blood samples were obtained from pigs on d 0, 7, and 14 in Exp. 1 and d 0, 7, 21, and 35 in Exp. 2 to determine hemoglobin (Hb), hematocrit (Hct), and plasma Cu, (PCu), Fe (PFe), and Zn (PZn). Pigs in Exp. 1 were killed at d 14 (mean BW = 8.7 kg) to determine whole-body, liver, and kidney mineral concentrations. There were no differences in growth performance in Exp. 1 or 2. In Exp. 1, pigs fed ZnO or ZnM diets had greater (P < 0.001) dietary Zn intake during the 14-d study and greater fecal Zn excretion during Phase 2 compared with pigs fed the NC diet. Pigs fed 2,000 mg/kg, regardless of Zn source, had greater (P < 0.010) PZn on d 7 and 14 than pigs fed the NC diet. Whole-body Zn, liver Fe and Zn, and kidney Cu concentrations were greater (P < 0.010), whereas kidney Fe and Zn concentrations were less (P < 0.010) in pigs fed pharmacological Zn diets than pigs fed the NC diet. In Exp. 2, dietary Fe supplementation tended to increase (linear, P = 0.075) dietary DMI, resulting in a linear increase (P < 0.050) in dietary Fe, Cu, Mg, Mn, P, and Zn intake. Subsequently, a linear increase (P < 0.010) in fecal Fe and Zn excretion was observed. Increasing dietary Fe resulted in a linear increase in Hb, Hct, and PFe on d 21 (P < 0.050) and 35 (P < 0.010). Results suggest that dietary Zn or Fe additions increase mineral status of nursery pigs. Once tissue mineral stores are loaded, dietary minerals in excess of the body's requirement are excreted.     

Effects of two zinc supplementation levels and two zinc and copper sources with different solubility characteristics on the growth performance,carcass characteristics and digestibility of growing-finishing pigs

The present study was conducted to evaluate the effect of two Zn supplemented levels and two Zn and Cu sources (sulphate and hydroxychloride) on growing-finishing pigs. An in vitro study and an in vivo study were conducted. In the in vitro study, Zn solubility from each source at different Zn supplementation levels was evaluated, as well as the phytic phosphorus (PP) solubility derived from the interaction or not with phytic acid at similar conditions to those found in digestive tract. The most critical interaction of Zn with phytic acid was at pH 6.5 and with Zn sulphate, resulting in the reduction in PP solubility. In the in vivo experiment, a total of 444 pigs ([Duroc × Landrace]×Pietrain; initial BW: 18.7 ± 0.20 kg) were allotted to 36 pens in a randomized complete block design (2 × 2) factorial arrangement with two Zn and Cu sources and two Zn supplemental levels (20 and 80 mg/kg). The Cu supplementation was fixed at 15 mg/kg for all diets. There was no effect of the interaction between mineral source × Zn level or Zn level on growth performance or carcass characteristics (p > .10). Apparent total digestibility of Zn and Cu along with carcass yield was higher for pigs fed hydroxychloride than pigs fed the sulphate counterparts (p < .05). Feeding low levels of Zn decreased Zn (45.5%; p < .0001) and Cu(18.5%; p = .018) faecal excretion. In conclusion, under commercial conditions, feeding growing-finishing pigs with Zn levels below those established by the European Union regulation did not affect growth performance and carcass characteristics. Reducing dietary mineral (Zn and Cu) diet content resulted in a lower faecal mineral excretion. Pigs fed sulphate minerals had an improved performance during grower period, while pigs fed hydroxychloride minerals showed an improved performance during finishing period and a greater carcass yield and mineral digestibility than those fed sulphates.     

Determination of true absorption and fecal endogenous loss of zinc in goats

We determined the true absorption and endogenous fecal loss of zinc (Zn) in goats using its stable isotope. Three goats were fed with the diet containing 50 mg/kg Zn twice a day for 17 days. In the morning of day 11, the goats were given a meal labeled by ⁶⁷Zn as the tracer with dysprosium as the unabsorbed marker. Then the goats were given unlabeled diet as the rest of the morning feed. We measured dietary and fecal Zn concentration, ⁶⁷Zn abundance and dysprosium concentration in feces. The excretion pattern of the tracer Zn into feces differed from that of dysprosium. Therefore, we directly calculated the true absorption of Zn from Zn concentration and ⁶⁷Zn abundance in fecal samples collected after the labeled diet was given. The apparent absorption of Zn was –0.009 ± 0.016 mg/kg bodyweight (fractional absorption, ?1.07 ± 1.85%). The true absorption of Zn was 0.162 ± 0.018 mg/kg bodyweight (fractional absorption, 18.25 ± 2.01%). The endogenous fecal loss of Zn was 0.172 ± 0.004 mg/kg bodyweight and the intestinal secretion of Zn was 0.210 ± 0.009 mg/kg bodyweight. The present experiment indicates that stable isotopic Zn is a powerful tool for examining Zn metabolism in ruminants.     

Effect of dietary zinc content and sources on the growth, body zinc deposition and retention, zinc excretion and immune response in chickens.

1. In areas of intensive animal production heavy metals such as zinc (Zn), which is present at high concentrations in poultry excreta in relation to plant requirements, may be at the origin of soil phytotoxicity This study was conducted in order to determine the effect of decreasing dietary Zn content on growth, plasma, tibia and whole body Zn concentrations, immune function, enzyme activity, Zn body retention and Zn concentration in excreta in broilers. 2. Two experiments were carried out using 160 and 80 1-day-old chicks. Broilers received diets with increased Zn contents of 20 to 190 mg/kg. In experiment 1, two sources of zinc methionine were compared to zinc sulphate. 3. A dietary Zn concentration of 45 mg/kg was sufficient to obtain normal broiler performance at 21 d of age. 4. Tibia and plasma Zn concentrations increased linearly with Zn dietary content and reached a plateau at 75 mg/kg, whereas the whole body Zn was saturated when the dietary Zn content was 90 mg/kg. 5. Antibody titres in response to SRBC injection and plasma alkaline phosphatase activity were not affected by dietary zinc concentration. 6. When the dietary Zn content was decreased from 190 to 65 mg/kg, body Zn retention was increased from 8% to 20% and Zn concentration in broiler manure was reduced by 75%. 7. Zn sources had no effect on the parameters measured in this study. 8. A nutritional approach, that is by lowering dietary Zn supplementation may reduce the risks of phytotoxicity in the soil resulting from excessive Zn concentration in manure.     

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.     

Apparent zinc absorption and zinc status of weanling rats fed moderately zinc‐deficient diets enriched with beef tallow or sunflower oil

The aim of the study was to compare apparent Zn absorption and Zn status of weanling rats fed diets that differed in Zn level, fat level and fat source. Semi‐synthetic diets, which were about isoenergetic and contained 3% soyabean oil, were supplemented with 7 or 100 mg Zn/kg to create a mild Zn deficiency (LZ) or a high Zn supply (HZ) and with 0 (LF), 22% beef tallow (BT) or 22% sunflower oil (SF) according to a 2 × 3 factorial design of treatments. They were fed ad libitum to 6 × 8 rats for 28 days. Energy intake and growth rates were comparable among the HZ groups. Weight gains in the LZ‐LF, LZ‐BT and LZ‐SF groups averaged 5.54, 4.95 and 4.15 g/day, and apparent Zn absorption averaged 79.4, 60.3 and 48.0 μg Zn/day, respectively, whereas faecal Zn excretion was comparable among these groups. Apparent Zn absorption, and plasma and femur Zn concentrations were lower in the high‐fat groups than in the LF group, possibly due to the high cellulose content of the BT and SF diets. Plasma Zn concentrations were higher in the animals fed the BT‐based than in the SF‐based diets, whereas femur and soft tissue Zn concentrations were comparable among these groups. The differences between the LZ‐BT and LZ‐SF groups in growth rate, Zn absorption rate and Zn status were confirmed in a second experiment. The results indicate that moderately Zn‐deficient diets enriched with SF in relation to BT affect Zn metabolism of weanling rats by a yet unknown mechanism.     

Evaluation of the mineral status of cattle on communal grazing in the North West Province of South Africa

Twenty five cattle were randomly selected from a herd of animals grazing communally around Mogosane village in the North West Province to evaluate their mineral status based on blood and faecal analysis. Mean faecal phosphorus (P) concentration was curvilinear, increasing from July (0.99 mg/g) to December (3.63 mg/g) and decreasing to 1.29 mg/g in June. Mean P concentration in grass was also curvilinear, increasing from July (0.87 mg/g) to January (1.8 mg/g) and decreasing to 0.9 mg/g in June. There was a high correlation (r2 = 0.89) between faecal and grass P concentrations. Faecal:grass P ratios suggest that the animals were conserving P by reducing faecal P excretion during times of low dietary P. Animals maintained consistent but very low serum inorganic P (SiP) throughout the year (range 1.33-1.95 mg%) and SiP was not correlated with either faecal or grass P. Mean faecal and grass calcium (Ca) concentrations followed a similar pattern to P. There was also a positive correlation (r2 = 0.95) between grass and faecal Ca concentrations. Faecal:grass Ca ratios indicated a conservation of Ca by reducing faecal Ca when dietary Ca was low. Animals were better able to conserve dietary Ca by reducing losses in the faeces than they were P, based on a higher faecal:grass P ratio (1.56) compared with Ca (1.18). Magnesium (Mg) was lost through the faeces during times of high dietary Mg concentrations but was conserved when grass Mg was low.     

Antioxidant status of faeces of captive black rhinoceros (Diceros bicornis) in relation to dietary tannin supplementation

In context with the frequent observations of excessive iron (Fe) storage in captive black rhinoceroses (Diceros bicornis), it has been suggested that both an excessive dietary Fe content and a lack of dietary Fe-chelating substances, such as tannins, is the underlying cause. Therefore, studies on the effects of tannin supplementation to captive diet are warranted. Six captive rhinoceroses were fed their normal zoo diet (N), and a similar diet supplemented with either tannic acid (T, hydrolysable tannin) or quebracho (Q, condensed tannins), and the total antioxidant capacity (TAC) was measured as mmol Trolox equivalents per kg fresh faeces. The TAC values on diets N (1.24 +/- 0.39 mmol/kg fresh faeces) and T (1.34 +/- 0.33 mmol/kg fresh faeces) were similar, but significantly higher on diet Q (2.32 +/- 0.61 mmol/kg fresh faeces). In contrast to expectations, faecal TAC increased with increasing faecal Fe, possibly as a result of the fact that the faecal Fe content was positively correlated to the proportion of concentrate feeds in the diet, which also contain antioxidants, such as vitamin E, in addition to Fe. Increased antioxidant status caused by the use of tannin substances could have a beneficial effect on animal health, but if tannins should be incorporated in designed diets, other tannin sources, such as grape pomace should be tested.     

饲粮粗蛋白质水平对中国荷斯坦奶牛产奶性能、氮利用及血液激素的影响

本试验旨在研究饲粮粗蛋白质（ＣＰ）水平对中国荷斯坦奶牛产奶性能、氮利用及血液激素的影响。采用重复 ４×４拉丁方设计,８头经产中国荷斯坦奶牛随机分为 ４个处理。４个处理的饲粮 ＣＰ水平分别为 １２．５６％、１３．９６％、１５．５３％和 １６．９３％。试验分为 ４个周期,每个周期１８ｄ。在 ４ｄ收集期内,全量收集粪、尿,每天测量产奶量、乳成分和干物质摄入量（ＤＭＩ）,并在收集期最后 １ｄ采集血样。结果表明：４个饲粮处理的 ＤＭＩ基本相同（Ｐ＞０．０５）;饲粮 ＣＰ水平１２．５６％的产奶量和能量校正奶（ＥＣＭ）明显低于饲粮 ＣＰ水平 １３．９６％至 １６．９３％（Ｐ＜０．０５）,饲粮 ＣＰ水平 １３．９６％至 １６．９３％的产奶量和 ＥＣＭ 基本相同,其中饲粮 ＣＰ水平 １３．９６％和１６．９３％的产奶量分别为２８．１８和２８．７２ｋｇ／ｄ,ＥＣＭ分别为３２．６４和３２．０４ｋｇ／ｄ;乳成分中仅乳蛋白率随着饲粮 ＣＰ水平增加而提高（Ｐ＜０．０５）;饲粮 ＣＰ水平 １２．５６％和 １３．９６％的乳氮效率明显高于饲粮 ＣＰ水平 １５．５３％和 １６．９３％（Ｐ＜０．０５或 Ｐ＜０．０１）;随着饲粮 ＣＰ水平的提高,尿氮排出量不断增加,乳氮排出量也缓慢上涨,体内氮沉积显著增加（Ｐ＜０．０５或 Ｐ＜０．０１）,只有饲粮 ＣＰ水平 １６．９３％的粪氮排出量明显增加（Ｐ＜０．０５）;饲粮 ＣＰ水平 １２．５６％的血液瘦素浓度最高（Ｐ＜０．０５）,催乳素（ＰＲＬ）、生长激素（ＧＨ）、胰岛素样生长因子 １（ＩＧＦ １）、血糖、非酯化脂肪酸（ＮＥＦＡ）和 β－羟丁酸（ＢＨＢＡ）浓度较高;而饲粮 ＣＰ水平 １６．９３％的血浆尿素氮（ＰＵＮ）浓度最高（Ｐ＜０．０１）,胰岛素和 ＧＨ浓度较高,ＩＧＦ １浓度较低。由此可见,饲粮 ＣＰ水平１３．９６％适合中国荷斯坦奶牛产奶量２８ｋｇ／ｄ或 ＥＣＭ３２ｋｇ／ｄ的泌乳性能、氮利用和内分泌调节。     

Early growth and environmental implications of dietary zinc and copper concentrations and sources of broiler chicks

1. Environmental accumulation of zinc and copper is becoming a concern in areas having intensive animal production. This study examined performance and excretion of broiler chicks given diets supplemented with graded concentrations of zinc and copper from three different sources. 2. Two experiments were conducted, each utilising 570 1-d-old chicks. In Experiment 1, chicks were given diets containing supplemental zinc concentrations from 40 to 120 mg/kg supplied as zinc sulphate, a zinc amino acid complex (Availa Zn), or a combination of zinc sulphate and Availa Zn with each contributing one-half of the total supplemental zinc. In Experiment 2, broiler chicks were given diets with graded concentrations of supplemental copper ranging from 4 to 12 mg/kg from copper sulphate, a copper amino acid complex (Availa Cu), or a combination of copper sulphate and Availa Cu with each contributing one-half of the total supplemental copper. 3. During the 17-d experimental period, mineral concentration or source did not influence body weight, feed conversion, or the incidence of mortality from 1 to 17 d. 4. Decreasing dietary zinc concentration from 120 to 40 mg/kg reduced zinc excretion by 50%. 5. Copper excretion was decreased by 35% as supplemental copper was reduced from 12 to 4 mg/kg. 6. Reducing dietary zinc and copper concentrations can potentially decrease the accumulation of heavy metals in the environment without compromising bird performance.     

Responses of broilers to dietary zinc concentrations and sources in relation to environmental implications

1. Since high concentrations of zinc are associated with reduced crop yields, environmental concerns are emerging regarding zinc accumulation in areas where poultry production is prevalent. This study investigates growth performance and zinc utilisation during the life cycle of broilers when diets were supplemented with various concentrations of zinc from two different sources. 2. A total of 740 Cobb 500 1-d-old male broiler chicks was randomly distributed into 88 battery cages. Excreta were collected over a 48-h period on d 10, 17, 24, 31, 38, and 45 to measure zinc excretion on a dry matter basis. 3. During the 45-d experimental period, broilers were given a maize-soybean meal basal diet (30 mg/kg zinc) supplemented with 0, 20, 40, and 80 mg/kg of zinc from zinc sulphate, Availa Zn amino acid complex, or an equal combination of zinc sulphate and Availa Zn amino acid complex. 4. Progressive additions of zinc to the basal diet significantly increased body weight gain of broilers, but did not affect feed conversion or mortality. Optimum body weight gain was achieved at 80 mg/kg supplemental zinc, which exceeds the NRC recommendations of 40 mg/kg. 5. During each excreta collection period, increased supplemental zinc concentrations significantly increased zinc excretion. However, the zinc source did not influence zinc utilisation. 6. As compared with zinc sulphate supplementation, the cumulative zinc excretion data indicate that adding zinc to the basal diet in the form of Availa Zn amino acid complex decreased zinc excretion.     

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.