Foot ash can replace tibia ash as a quantification method for bone mineralization in broilers at 21 and 42 days of age

Prior research indicated that foot ash determinations were as robust as tibia bone ash determinations in reflecting the degree of bone mineralization in chicks at 14 d of age. In the current research, the relative effectiveness of the 2 procedures was evaluated in 21- and 42-day-old broilers while also evaluating a new dietary phytase supplement. In experiment 1, broilers were fed until 21 d of age a negative control diet with 0.24% available phosphorus, a positive control diet with 0.48% available phosphorus, or the negative control diet supplemented with 300, 500, 1,000, or 2,500 phytase units/kg diet. In experiment 2, broilers were fed until 42 d of age negative control diets having 0.275, 0.250, and 0.225 percent available dietary phosphorus in the starter, grower, and finisher periods, respectively, positive control diets having 0.475, 0.450, and 0.425 percent available dietary phosphorus in the starter, grower, and finisher periods, respectively, or the negative control diets supplemented with 500, 1,000, or 2,500 phytase units/kg diet. At 21 and 42 d of age, broilers fed diets supplemented with the 2 highest doses of phytase had foot and tibia ash values equal to those fed the positive control diet and higher than those fed the negative control diet. At 42 d of age, feed conversion and total breast meat yield values for the broilers fed the highest dose of phytase were superior to the values of the birds fed the positive control diet or the diet containing the lowest dose of phytase. The results indicate that adding levels of this new dietary phytase beyond what is necessary for normal bone mineralization enhances feed conversion and that dried foot and tibia bone ash determinations are both reliable in detecting differences in bone mineralization in 21- and 42-day-old broilers.     

The effect of bone choice on quantification of mineralization in broiler chickens up to 6 weeks of age

An experiment was conducted to assess the most appropriate bone type for measuring bone mineralization in male broiler chicks up to 42 d. A total of 72 male broilers were raised in 0.64 m² pens on a litter floor. The study design included 2 dietary treatments (Control and Low) containing differing levels of total phosphorus (7.8 and 4.4 g/kg for Control and Low diets respectively) and calcium (22.7 and 13.1 g/kg for Control and Low diets respectively) with each fed to 6 replicate pens of 6 birds. Each wk, 6 birds per diet were euthanized and leg bones removed to measure ash percentage. Foot, toe, tibia, and femur ash were compared using the mean of both legs from each bird, via t-tests to separate Control and Low diets. At the end of wk 1, diets could not be separated using any of the bone ash measures. From wk 2 to wk 5, both tibia and foot ash differentiated between the Control and Low diets, and tibia continued to show significant differences between the diets into wk 6. Femur ash did not show any dietary differences until wk 3, but then showed significant differences between the diets until wk 6. Toe ash only differentiated between diets at wk 2, and variation both within and between birds was high, particularly with younger birds. These results suggest that bird age has implications when choosing a bone for assessing possible differences in dietary phosphorus and calcium uptake. Femur ash may be more appropriate for showing differences in broilers aged 6 wk and older. Foot ash provides a comparable alternative to tibia ash in birds aged 2 to 5 wk of age, providing a labor- and time-saving alternative.     

Effects of Broiler Strain,Dietary Nonphytate Phosphorus,and Phytase Supplementation on Chick Performance and Tibia Ash

Three experiments were conducted to study the effects of broiler strain and phytase supplementation on chick nonphytate P (NPP) requirements for growth, feed intake, and tibia ash. The first experiment compared the NPP requirements for 8- to 22-d-old chicks from 2 broiler strains, Ross 308 and 708, that have been selected for differences in early weight gain and performance. The second experiment utilized similar 8- to 22-d-old Ross 308 and 708 chicks but also compared the effects of dietary fungal phytase supplementation (600 U/kg) on broiler NPP requirements. The third experiment utilized a younger starting age, 5 to 23 d old, for Ross 308 and 708 chicks with and without phytase supplementation. Minor differences in chick growth did not affect chick NPP requirements in Experiments 1 and 3, but a substantial and unexplained reduction of growth of the Ross 708 chicks in Experiment 2 resulted in a lower NPP requirement for chick growth and feed intake but not for tibia ash. As expected, supplementation of diets with fungal phytase did result in decreased NPP requirements for growth, feed intake, and tibia ash in both strains used in Experiment 3.     

饲粮钙磷水平对乌骨鸡生长性能及胫骨灰分含量的影响

为了得到乌骨鸡适宜的饲粮钙磷水平,将2250只乌骨鸡随机分为5组,设置不同饲粮钙磷水平,测定其对乌骨鸡生长性能及胫骨灰分含量的影响。研究结果表明,根据乌骨鸡的生长性能及胫骨灰分含量的数据分析,乌骨鸡饲粮1~25日龄钙水平0.90%、非植酸磷水平0.40%,26~45日龄钙水平0.85%、非植酸磷水平0.36%,46~65日龄钙水平0.80%、非植酸磷水平0.33%已完全满足其生长和骨骼发育的需要,高于此钙磷水平对乌骨鸡骨骼发育和生长性能无明显改善。     

Biological Availability of Phosphorus Sources in Prestarter and Starter Diets for Broiler Chicks

Two of the most widely used phosphate sources for broiler diets are defluorinated tricalcium phosphate (DFP) and dicalcium phosphate (DCP). Reports in the literature have shown that the biological availability of P in DFP for broilers and laying hens is lower than that in DCP. If this difference in bioavailability is even greater in young chicks, it might preclude the inclusion of DFP in prestarter and possibly starter diets. To address this question, 2 experiments were conducted to compare the P bioavailability of DFP and DCP in young broilers during the prestarter (1 to 8 d) and starter (9 to 15 d) periods. In Experiment 1, the first 3 treatments contained DFP, DCP, or raw rock phosphate, which were added to the diets to meet 0.32% available P (AP). Additionally, in 3 other treatments that served as positive controls, K₂ HPO₄ was added to meet AP levels of 0.24, 0.32, and 0.40%. No significant difference was observed at 4, 8, and 15 d of age between the foot ash percentage of chickens fed the DFP and DCP diets, indicating that the biological availability of P in DFP was not significantly inferior to that of DCP. In Experiment 2, chick responses to 2 levels of either DFP or DCP, added to meet AP levels of 0.28 and 0.34%, were compared with those of chicks receiving K₂ HPO₄, which was added to meet 3 AP levels (0.22, 0.28, and 0.34%). Foot ash results at 6 and 15 d of age indicated that the P utilization of chickens fed diets containing DFP was not significantly different to that of chickens fed the DCP diets. The difference in P bioavailability between DFP and DCP at 6 or 15 d of age was not greater than 10%. These results indicate that DFP can be satisfactorily utilized by young chicks during the prestarter and starter period and do not support the view that DFP should be excluded from diets for young chickens.     

饲料中钙、磷水平对4～6周龄肉鸡骨骼生长的影响

选用800只21日龄白羽肉鸡,采用5×4二因子完全随机试验设计,随机分成20组,每组4个重复。在玉米-豆粕型日粮基础上添加5个水平钙(0.6%、0.8%、1.0%、1.2%和1.5%)和4个水平非植酸磷(0.35%、0.45%、0.55%和0.65%),研究饲料中不同钙、磷水平对4～6周龄肉鸡骨骼生长的影响。结果表明:胫骨强度、胫骨灰分及胫骨磷含量和日粮钙、磷水平呈显著正相关(P<0.05),但1.5%钙、0.6%钙和0.35%非植酸磷都显著降低胫骨强度、胫骨灰分及胫骨磷含量(P<0.05)。4-6周龄肉鸡达到最大胫骨强度时的日粮钙、非植酸磷添加水平分别为1.0%和0.45%。。由回归方程得出4-6周龄肉鸡胫骨灰分含量和胫骨强度达最大时的日粮钙、非植酸磷添加水平分别为0.99%、0.55%和1.02%、0.55%。     

High vitamin D3 requirements in broilers for bone quality and prevention of tibial dyschondroplasia and interactions with dietary calcium, available phosphorus and vitamin A

1. Two experiments were carried out to investigate responses in performance and bone compositional and structural characteristics in broilers fed diets containing 4 concentrations of vitamin D3 (5, 20, 125 and 250 microg cholecalciferol/kg) at different concentrations of calcium, available phosphorus and vitamin A. 2. In experiment 1, body weight and tibia breaking strength were maximised at 14d with 250 microg vitamin D3/kg, tibia ash was maximised with 125 microg vitamin D3/kg. A high incidence of tibial dyschondroplasia (TD) was decreased to very low levels with 125 microg vitamin D/kg. 3. At 42d, performance and bone characteristics showed no response to vitamin D3 concentrations above 20 microg/kg. 4. Dietary vitamin A within the range 2-4 to 4.5 mg retinol/kg did not show any interaction with vitamin D3 status at either age. 5. In experiment 2, responses to vitamin D3 were strongly influenced by dietary calcium/available phosphorus. With 13 g calcium and 5 g available phosphorus/kg, performance and bone characteristics responded to vitamin D3 concentrations up to 125 microg/kg but more was needed at less optimal concentrations of calcium and available phosphorus. TD incidence was minimised with 250 microg/kg. 6. This study shows that high dietary concentrations of vitamin D3 can prevent TD. It is concluded that the vitamin D3 requirement of broilers up to 14 d of age at optimal dietary calcium and available phosphorus concentrations may be in the range 35 to 50 microg/kg for cortical bone quality and up to 250 microg/kg for prevention of TD. The vitamin D3 requirement for cortical bone quality after 14 d is not higher than 20 microg/kg. These requirements are much higher than earlier estimates and may be related to higher calcium requirements of modern broiler genotypes. Current regulations limiting maximum vitamin D3 concentrations in broiler starter diets may need to be reviewed.     

Effects of Source of Inorganic Phosphorus and Phytase Supplementation on Performance, Physiological Parameters and Bone Mineralization in Broilers

The objective of this study was to eval- uate the effects of inorganic phosphorus source and phytase addition on performance, nutrient digestibility and bone mineralization in broiler chickens. In Exp. 1,150 two-day old, male broiler chicks were fed a corn-soybean meal basal diet supplemented with phos- phorus provided by dicalcium phosphate, tricalcium phosphate or defluorinated rock phosphate. Five cages containing 10 birds were allotted to each of the three treatments. In Exp. 2,120 three-day old, male broiler chicks were fed the basal diet from Exp. 1 supplemen- ted with 0,250,500 ,or 1,000 P-＇rU phytase per kg of diet. Six cages containing five chicks were allotted to each of the four treatments. In Exp. 1, there was no difference in weight gain, feed intake or feed conver- sion as a result of feeding the different sources of in- organic phosphorus. The digestibility of phosphorus was significantly lower （P =0.01 ） for chicks fed di- ets supplemented with tricalcium phosphate than for chicks fed the other two diets. However, despite the lower digestibility, serum phosphorus levels did not differ among the three treatments. For Exp. 2, feedconversion showed a linear improvement （P = 0.03 ） with increasing levels of phytase inclusion （ days 0 to 33 ）. Phytase supplementation resulted in linear increa- ses in the digestibility of dry matter （P = 0.02 ）, crude protein （ P --- 0.04 ） and energy （ P 〈 0.01 ）. Chicks fed 1,000 FTU/kg phytase had significantly higher bone calcium （ P = 0.05 ） and bone breaking strength （P = 0.04 ） than chicks fed the basal diet on day 33. In conclusion, the results of the current study indicated that the performance of birds fed diets sup- plemented with dicalcium phosphate, tricalcium phos- phate or defluorinated phosphate was similar and therefore production costs could be lowered by choo- sing the cheapest inorganic phosphorus source when formulating diets for poultry. When diets were formu- lated to meet dietary phosphorus requirements, the growth of broilers was not enhanced with phytase sup- plementation. However, increases in feed conversion and bone breaking strength and its potential to impact culling and mortality in broiler operations may be suf- ficient justification for the routine inclusion of phytase in diets fed to broilers.     

Dietary cholecalciferol and phosphorus influence intestinal mucosa phytase activity in broiler chicks

1. The role of cholecalciferol and phosphorus in the regulation of intestinal mucosa phytase was investigated in broiler chicks. 2. A total of 144 7-d-old male broiler chicks were grouped by weight into 6 blocks of 4 cages with 6 broiler chicks per cage. Four maize-soybean meal-based mash diets were randomly assigned to cages within each block. The 4 diets consisted of cholecalciferol at 0 or 75 microg/kg and total phosphorus at 3.6 or 7.0 g/kg in a 2 x 2 factorial arrangement. The birds were given the experimental diets for 12 d under conditions which excluded ultraviolet light. 3. Broiler chicks fed on diets with the higher concentration of cholecalciferol had higher Vmax and Km of the mucosa phytase, weight gain, feed intake, feed efficiency and percentage tibia ash, higher ileal digestibility of dry matter, energy, phosphorus (P) and calcium (Ca), and increased retention of dry matter, nitrogen, P, Ca and energy. 4. Broiler chicks receiving diets with the higher P concentration showed lower Vmax and Km of the intestinal mucosa phytase but greater weight gain, feed intake, feed efficiency and percentage tibia ash, higher ileal digestibility of dry matter, energy, P and nitrogen, and increased retention of dry matter, energy, nitrogen and Ca. 5. In conclusion, both dietary P and cholecalciferol influenced the activity of intestinal mucosa phytase.     

Effects of Rice Bran Inclusion on Performance and Bone Mineralization in Broiler Chicks

Rice bran, a by-product of the rice industry, is available for animal feeds. However, it has not been a common part of poultry rations in Argentina. Hydrolytic and oxidative rancidity development, phytate content, enzyme inhibitor, and high fiber content are the most important antinutritive factors cited as limiting factors for its use. An experiment utilizing 1-d-old male broiler chicks was conducted to determine the responses of zootechnical and bone mineralization parameters to diets with different concentrations of rice bran. The feed conversion and tibia ash were more sensitive than weight gain to detect antinutritive factors in rice bran. High concentrations of rice bran (in excess of 20%) produced a significant reduction in body weight. Furthermore, feed conversion and bone mineralization variables were impaired by feeding 10% rice bran diets. The adverse effects of rice bran on weight gain, feed conversion, and mineralization in the current studies suggest that rice bran should be included in broiler diets at a level between 10 and 20% if strategies are not used to decrease the antinutritive activity.     

饲粮添加不同水平维生素D_3对肉仔鸡生长性能和骨磷代谢利用的影响

本试验旨在研究饲粮中添加不同水平维生素D3(VD3)对肉仔鸡生长性能及骨磷代谢利用的影响。试验选用480只1日龄艾拔益加肉公雏,采用2×4双因子完全随机设计,设2个饲粮非植酸磷水平[0.45%和0.23%(实测值为0.44%和0.21%)]与4个VD3添加水平(0、1 000、2 000和4 000IU/kg),共8个组,每组6个重复,每个重复10只鸡。试验期21d。结果表明,与0.21%非植酸磷水平相比,0.44%非植酸磷水平显著提高肉仔鸡平均日增重(ADG)、平均日采食量(ADFI)、胫骨灰分含量和胫骨灰分磷含量(P0.05),显著降低料重比(F/G)和胫骨灰分磷绝对沉积率(P0.05);与不添加VD3相比,饲粮中添加VD3显著提高肉仔鸡ADG、15~21和1~21日龄ADFI、胫骨灰分含量和胫骨灰分磷绝对沉积率(P0.05),显著降低1~21日龄肉仔鸡F/G(P0.05);0.21%非植酸磷水平下,与不添加VD3相比,饲粮中添加VD3显著降低肉仔鸡死亡率(P0.05),显著提高21日龄肉仔鸡胫骨灰分磷重量(P0.05),添加2000IU/kg VD3显著提高14日龄肉仔鸡胫骨灰分磷重量(P0.05);0.44%非植酸磷水平下,与不添加VD3相比,饲粮中添加VD3显著提高肉仔鸡胫骨灰分磷重量(P0.05)。以上结果表明,饲粮中添加VD3可提高肉仔鸡的生长性能并降低死亡率,促进磷在骨骼中的代谢利用。     

Effects of Source of Inorganic Phosphorus and Phytase Supplementation on Performance, Physiological Parameters and Bone Mineralization in Broilers

The objective of this study was to evaluate the effects of inorganic phosphorus source and phytase addition on performance, nutrient digestibility and bone mineralization in broiler chickens. In Exp. 1, 150 two-day old, male broiler chicks were fed a corn-soybean meal basal diet supplemented with phosphorus provided by dicalcium phosphate, tricalcium phosphate or defluorinated rock phosphate. Five cages containing 10 birds were allotted to each of the three treatments. In Exp. 2, 120 three-day old, male broiler chicks were fed the basal diet from Exp. 1 supplemented with 0, 250, 500, or 1,000 FTU phytase per kg of diet. Six cages containing five chicks were allotted to each of the four treatments. In Exp. 1, there was no difference in weight gain, feed intake or feed conversion as a result of feeding the different sources of inorganic phosphorus. The digestibility of phosphorus was significantly lower (P = 0.01) for chicks fed diets supplemented with tricalcium phosphate than for chicks fed the other two diets.  However, despite the lower digestibility, serum phosphorus levels did not differ among the three treatments. For Exp. 2, feed conversion showed a linear improvement (P = 0.03) with increasing levels of phytase inclusion (days 0 to 33).  Phytase supplementation resulted in linear increases in the digestibility of dry matter (P = 0.02), crude protein (P = 0.04) and energy (P < 0.01).  Chicks fed 1,000 FTU/kg phytase had significantly higher bone calcium (P = 0.05) and bone breaking strength (P = 0.04) than chicks fed the basal diet on day 33. In conclusion, the results of the current study indicated that the performance of birds fed diets supplemented with dicalcium phosphate, tricalcium phosphate or defluorinated phosphate was similar and therefore production costs could be lowered by choosing the cheapest inorganic phosphorus source when formulating diets for poultry. When diets were formulated to meet dietary phosphorus requirements, the growth of broilers was not enhanced with phytase supplementation.  However, increases in feed conversion and bone breaking strength and its potential to impact culling and mortality in broiler operations may be sufficient justification for the routine inclusion of phytase in diets fed to broilers.     

Body weight of young broilers fed with declining calcium and phosphorus contents during the starter period is irresponsive to changes in the skeleton

To evaluate the effect of reduced calcium (Ca) and available P (aP) levels in starter diets on growth performance and tibia, sternum and serum characteristics, and to assay the association between Ca and P (aP) intakes and these variables, 600 one-day-old broiler chicks (Ross 308) were used in a 21-days trial. Broilers were randomly allotted to five treatments with five replicate pens. Chicks were fed on one of the five starter diets that were formulated with a 10% reduction in the Ca and aP contents, starting from the control diet and hence, named as C (0.96% Ca, 0.45% aP), L1 (0.85% Ca and 0.42% aP), L2 (0.77% Ca and 0.38% aP), L3 (0.68% Ca and 0.34% aP) and L4 (0.61% Ca and 0.31% aP). Declining dietary Ca and aP levels did not affect body weight and levels of Ca, P and alkaline phosphatase in serum, but reduced linearly feed intake, the feed conversion ratio and the bone weight and ash content. The Ca and aP intakes and Ca:aP ratio displayed a positive correlation with both tibia and sternum weights, and the mass of the bones were equally sensitive to dietary Ca and aP levels. In conclusion, the body weight of young broilers was irresponsive to changes in the skeleton when exposed to early dietary Ca and aP restrictions (up to 0.61% Ca and 0.31% aP) and the mechanostat had limits due to the association between Ca and aP intakes, and bone properties.     

Influence of phytate level on broiler performance and the efficacy of 2 microbial phytases from 0 to 21 days of age

Phytate is an antinutrient in animal feeds, reducing the availability and increasing the excretion of nutrients. Phytases are widely used to mitigate the negative influences of phytate. This trial was designed to compare the efficacy of 2 Escherichia coli-derived phytases on broiler performance and bone ash as influenced by dietary phytate level. A total of 1,024 Arbor Acres male broilers were used with 8 replicate pens of 16 birds/pen. Experimental diets were based on low available phosphorus (avP; 1.8 g/kg) with low (6.40 g/kg) or high (10.65 g/kg) phytate. The low-avP diets were then supplemented with mono-dicalcium phosphate to increase the avP level to 4.5 g/kg, 500 phytase units/kg of phytase A, or 500 phytase units/kg of phytase B to create 8 experimental diets. Feed intake, BW gain, FCR, and livability were influenced by a P source × phytase interaction. Feed intake, BW gain, and livability were reduced and FCR was higher in broilers fed low-avP diets, particularly in the presence of high phytate. Phytase A or phytase B improved feed intake, BW gain, and FCR, particularly in the high-phytate diet. However, broilers fed phytase A ate more and were heavier than broilers fed phytase B. Tibia ash was lowest in broilers fed the low-avP diet and highest in broilers fed the diet supplemented with mono-dicalcium phosphate. Phytase increased tibia ash, and broilers fed phytase A had an increase in tibia ash compared with broilers fed phytase B. In conclusion, high dietary phytate reduced broiler performance. Phytase A and phytase B improved bone ash and growth performance, especially in the high-phytate diets. However, phytase A was more efficacious than phytase B, regardless of the level of phytate.     

0～21和22～42日龄黄羽肉鸡可消化蛋氨酸需要量的研究

试验一和试验二分别选用1日龄和22日龄岭南黄鸡各2 000只和1 600只,按性别和体重分成10处理组(公、母鸡各5组),每组4重复栏,每栏50(试验一)和40只鸡(试验二)。2个试验均采用5(饲粮蛋氨酸水平)×2(性别)两因子试验设计,试验一和二分别设0.35%、0.40%、0.45%、0.50%和0.55%以及0.30%、0.35%、0.40%、0.45%和0.50%5个饲粮蛋氨酸水平。结果表明:随着饲粮蛋氨酸水平提高,0～21日龄和22～42日龄公、母鸡每日总蛋氨酸摄入量和真可消化蛋氨酸摄入量呈线性或二次曲线升高(P<0.05);0～21日龄公、母鸡的日增重呈二次曲线升高(P<0.05),0～21日龄和22～42日龄公、母鸡的饲料增重比呈二次曲线降低(P<0.05或0.1)。可见,在基础饲粮中添加适量蛋氨酸改善了黄羽肉鸡的生产性能。根据二次回归模型估测黄羽肉鸡获得最佳生产性能95%处的总蛋氨酸需要量和真可消化蛋氨酸需要量,0~21日龄母鸡为0.433%~0.435%和0.404%~0.406%,公鸡为0.445%~0.454%和0.416%~0.425%,22～42日龄母鸡为0.463%和0.437%,公鸡为0.375%和0.349%。     

Which source and level of dietary sodium is appropriate for broiler chickens reared in a high‐altitude area?

This study investigated effect of increasing level of dietary sodium using sodium bicarbonate or sodium chloride on growth performance, mortality, characteristics of carcass, organs and tibia, calcium and phosphorus of serum in broilers reared in a high‐altitude area (1,700 m above sea level). A total of 588 Ross 308 male broiler chicks were used in seven treatments, six replicates per treatment of 14 birds per each from 1 to 38 d of age. Seven dietary treatments consisted of a basal diet (with 0.16% sodium and 0.23% chloride), top‐dressed for six diets to give three supplementary levels of sodium (0.07%, 0.14% and 0.21%) from sodium bicarbonate (respectively by 0.26%, 0.52% and 0.78%) or sodium chloride (respectively by 0.18%, 0.36% and 0.54%), resulting in seven diets with total sodium and chloride levels of 0.16% and 0.23%, 0.23% and 0.23%, 0.30% and 0.23%, 0.37% and 0.23%, 0.23% and 0.33%, 0.30% and 0.44%, 0.37% and 0.55% respectively. Increasing sodium level improved feed conversion ratio (FCR) linearly and quadratically. However, when FCR was calculated without adjusting for feed intake of mortalities, the enhanced sodium level did not improve this parameter. Increasing sodium level via sodium chloride enhanced ascites mortality, total mortality, relative weight of heart and right ventricle linearly. Increasing sodium level reduced serum calcium and enhanced serum phosphorus linearly; however, there was a linear tendency to increase tibia ash when sodium level was enhanced by sodium bicarbonate (p = 0.08) or sodium chloride (p = 0.07). Increasing sodium level via sodium bicarbonate tended (p = 0.08) to reduce tibia strength linearly. In conclusion, a diet with 0.16% sodium and 0.23% chloride is enough for broiler chicken reared in a high‐altitude area, and increasing dietary sodium level via sodium chloride has detrimental effect on survivability of broiler in such condition.     

Effects of dietary calcium, available phosphorus and vitamin D on growth rate, food utilisation, plasma and bone constituents and calcium and phosphorus retention of commercial broiler strains

1. The effects of different dietary concentrations of calcium (Ca), available phosphorus (AP) and vitamin D (D) on 5- to 16-day growth performance, and aspects of calcium and phosphorus (P) metabolism of chickens from three commercial strains were studied in two experiments. 2. Increasing dietary Ca reduced weight gain, tibia Ca and P content and increased plasma total Ca, Ca consumption and excretion, whilst dietary Ca at 32 g/kg increased tibia Ca:P ratio, plasma ionized calcium and reduced plasma P, tibia ash, P excretion, excreta moisture and Ca retention. 3. Increasing dietary AP reduced plasma total and ionized Ca and excreta moisture and increased P consumption and excretion, plasma P and tibia ash. 4. The addition of vitamin D increased plasma total and ionized Ca, tibia Ca:P ratio and reduced plasma sodium and P concentrations. 5. Strains differed in their tibia contents of Ca and Ca:P ratios, in response to Ca, AP and vitamin D diets whilst they differed in Ca excretion and excreta moisture caused by feeding either dietary Ca or AP. 6. It was concluded that dietary Ca, AP, vitamin D and strain of broiler chickens influenced the metabolism of Ca and P and that, as a consequence, the tolerance to high dietary Ca. A lean strain of chickens tolerated high dietary calcium better than its fat counterparts.     

Study on Relative Bioavailability of 1α-Hydroxycholecalciferol to 25-Hydroxycholecalciferol in Broiler Chickens

The study was conducted to determine the relative bioavailability (RBV) of 1α-hydroxycholecalciferol (1α-OH-D₃) to 25-hydroxycholecalciferol (25-OH-D₃) in Ross 308 broiler chickens from 1 to 42 days of age.300 one-day-old Ross 308 broilers were randomly assigned into 6 groups with 5 replicates per group and 10 chicks per replicate.The six groups were fed with basal diets in which 2.5,5.0,10.0 μg/kg 25-OH-D₃ and 1.25,2.5,5.0 μg/kg 1α-OH-D₃ were added,respectively.The RBV of 1α-OH-D₃ to 25-OH-D₃ was determined by the slope ratio method.The results showed that average body weight gain (ABWG),feed to gain ratio (F/G),plasma phosphorus (P) were improved with the 1α-OH-D₃ and 25-OH-D₃ addition and the tibia and femur weight,length,and ash weight were linearly increased with the levels of 1α-OH-D₃ or 25-OH-D₃ increasing (P< 0.05).Using ABWG,F/G,and plasma P as the criteria,RBV of 1α-OH-D₃ to 25-OH-D₃ were 2.16,2.56,and 2.77.Using tibia weight,length,width,and ash weight as the criteria,RBV of 1α-OH-D₃ to 25-OH-D₃ were 1.80,1.88,2.42,and 2.04.Using femur weight,length,and ash weight as the criteria,RBV of 1α-OH-D₃ to 25-OH-D₃ were 1.89,1.98,and 2.18.These results indicated that the activity of 1α-OH-D₃ was approximately 2.17 times higher than that of 25-OH-D₃ in promoting growth performance and bone mineralization in broiler chickens from 1 to 42 days of age.     

Relative bio-availability and utilisation of phosphatic fertilisers as sources of phosphorus in broilers and layers

1. Different concentrations of non-phytate phosphorus (NPP, 2.5, 3.0, 3.5, 4.0 and 4.5 g/kg diet) were given to broilers (8 to 42 d of age) to establish regressions between dietary NPP concentration and body weight gain and tibia ash content. Second and third experiments were conducted to study the feasibility of utilisation of different phosphatic fertilisers [ammonium phosphate (AP), ammonium polyphosphate (APP), single super phosphate (SSP), NPK (17:17:17, NPK) and NP (28:28:0, NPK)] in commercial broilers (8 to 42 d) and White Leghorn layers (252 to 364 d). 2. Phosphatic fertilisers were incorporated both in broiler (10 g calcium and 4.5 g NPP/kg) and layer (35 g calcium and 3.5 g NPP/kg) diets by replacing dicalcium phosphate (DCP) in toto. 3. The logarithmic curves obtained for predicting the body weight gain and tibia ash content at different levels of NPP used in experiment 1 were Y = 156.27 + 2,468.8 logX (r2= 0.958) and Y = 530.82 + 144.26 log X (r2 = 0.916), respectively. 4. Body weight gain and food intake in broilers given APP- or NP-supplemented diets were comparable to these in the DCP-fed group. Feeding of NPK, AP or SSP resulted in significant depression in weight gain and food intake and high excreta moisture content. Food/gain, Ca and P contents in tibia ash and serum were not influenced by the use of phosphatic fertilisers as P sources in broiler diets. 5. Tibia ash content in broilers fed on diets containing fertilisers was either similar to or significantly higher than that in the DCP-fed group. Broilers on AP or SSP retained more P and had higher tibia ash content than those on DCP. AP, SSP or NPK caused degenerative and necrotic changes in liver, kidney and intestine of broilers. 6. Relative bio-availability of P from APP or NP was better for body weight gain than AP, SSP or NPK, while the reverse was true for bone calcification. 7. APP and NP gave hen-d egg production similar to that of DCP-fed layers. Food intake was significantly reduced in layers fed on diets containing fertilisers. However, food/egg mass, egg weight and serum Ca and inorganic P contents were not influenced by inclusion of fertilisers in layer diets. 8. Except for AP, inclusion of fertilisers in layer diets reduced shell weight and shell thickness compared with the DCP-fed group. However, no apparent eggshell defects were found which could be attributable to diet. 9. Results of these experiments suggest that APP and NP can be used as the sole source of P both in broiler and layer diets, replacing DCP in toto. However, when utilising these P sources in layers, due attention should be given to shell quality. Fertilisers containing high F (AP and SSP) or K (NPK) reduced performance in broilers and layers and caused microscopic changes in liver, kidney and intestine in broilers.     

维生素A过量对肉鸡早期骨骼钙磷代谢的影响

试验通过研究维生素A过量对肉鸡早期骨形成生化指标及组织中碱性磷酸酶（ALP）和骨钙素（BGP）基因表达的影响,旨在为深入研究日粮维生素A过量对肉鸡骨骼钙磷代谢产生负面影响的机理提供理论基础。采用完全随机试验设计,将450只1日龄健康爱拔益加（AA）肉鸡（公母各半）称重后随机等分为5个处理组,每个处理6个重复,每个重复15只鸡。各处理组日粮分别在基础日粮中添加3 000、6 000、15 000、30 000和60 000 IU/kg维生素A。试验期28 d,分别于试验第14、28天从每个重复中随机抽取1只鸡,翅静脉采血制备血清后随即宰杀,在冰浴上迅速分离右侧肝脏、十二指肠、空肠、回肠、胫骨组织,-80℃保存备用。试验结果表明,随日粮维生素A添加剂量的升高,肉鸡血清BGP浓度、ALP活性和骨特异性碱性磷酸酶（BAP）活性及胫骨、肝脏及小肠组织中ALP、BGP mRNA相对表达量均呈显著（P<0.05）或趋于显著的一次线性或一元二次（P<0.10）降低,通过回归分析得出：维生素A水平在42 766~47 185 IU/kg时,肉鸡14 d胫骨和肝脏ALP mRNA相对表达量、肝脏BGP mRNA相对表达量,28 d的血清ALP活性及肝脏ALP mRNA相对表达量、胫骨和回肠的BGP mRNA相对表达量最低。综合试验结果,维生素A线性降低了肉鸡早期血清BAP活性;日粮维生素A以剂量依赖模式影响肉鸡早期血清BGP浓度、ALP活性及其在组织中的基因表达,42 766~47 185 IU/kg维生素A对上述指标的降低作用较大,提示日粮维生素A过量可抑制肉鸡早期骨形成相关生化指标的活性,并下调胫骨、肝脏及小肠组织中ALP、BGP mRNA的相对表达量。