H. M. Edwards

The response of broilers to the feeding of mash or pelleted diets containing maize of varying particle sizes.

1. The effects of maize particle size and steam pelleting on growth and nutrient utilisation were studied with broiler chicks. 2. The presence or absence of 10 μg/kg of 1,25 dihydroxycholecalciferol in diets adequate or deficient in phosphorus was also investigated. Food efficiency was superior with the fine maize diets but calcium retention and phytate phosphorus retention were greatest with the coarse maize diets. Pelleting improved food efficiency and growth in both experiments while phytate phosphorus utilisation was decreased. 3. Addition of 1,25-dihydroxycholecalciferol to the diet increased 16-d body weight, bone ash, plasma dialysable phosphorus and retentions of total phosphorus and phytate phosphorus while decreasing phosphorus deficiency rickets and tibial dyschondroplasia. 4. There were significant interactions between maize particle size and food form. The improvement in calcium retention observed with the coarse maize diets was reduced when the diets were pelleted. When fed as a mash, coarse maize diets resulted in increased plasma dialysable phosphorus levels but when the diet was pelleted this response was eliminated. 5. There was also a significant interaction between particle size and phosphorus concentration in that chicks given diets deficient in phosphorus had improved bone ash when fed coarse maize as compared to fine maize. However, this response was eliminated when the diets were adequate in phosphorus. 6. In one experiment, fine maize diets had higher metabolisable energy values and there was a significant interaction between maize particle size and food form as pelleting improved the metabolisable energy value of coarse maize diets but not fine maize diets. In another experiment only pelleting of the factors studied improved the metabolisable energy value of the diets.

The analysis for inositol phosphate forms in feed ingredients

Limited data are available on the content of inositol phosphates in feed ingredients. The doubtfulness over the identity and literature values of the inositol hexaphosphate (phytate) analysed in feed ingredients by the classical iron precipitation method prompted the analysis for inositol phosphates in some feed ingredients using a modified high-performance liquid chromatography method. The inositol phosphates analysed were inositol triphosphate (IP3), inositol tetraphosphate (IP4), inositol pentaphosphate (IP5) and inositol hexaphosphate (IP6). At least 97% of the inositol phosphates in grains occurred as IP6 and the remainder as IP5. In milled products the relative percentage of IP5 was higher (up to 14·5% in wheat bran) but the overall IP6 relative percentage was still high (more than 82%). IP3 and IP4 were not present in grains, and their amounts were very low when present in their milling or processed fractions. The absolute IP6 content was highest in rice bran and wheat bran at 68·31 and 47·63 g kg−1, respectively. The results indicate that processed plant products may contain hydrolysis products of IP5 and IP6. These products contain greater percentages of IP3, IP4 and IP5 than in grains or milling products.

The Effect of Several Organic Acids on Phytate Phosphorus Hydrolysis in Broiler Chicks

Supplementation of some organic acids to a P-deficient diet has been shown to improve phytate P utilization. Two experiments were conducted from 0 to 16 d in battery brooders to determine the effect of various organic acids supplementation on phytate P utilization. In both experiments, birds were fed P-deficient corn and soybean meal-based diets. In experiment 1, citric acid, malic acid, fumaric acid, and EDTA were supplemented. Experiment 2 had a 2 x 2 factorial design with 2 sources of Met, 2-hydroxy-4-(methylthio) butanoic acid (HMB) and dl-Met, with or without 500 U/kg of phytase. In experiment 1, the addition of citric, malic, and fumaric acids increased percentage of bone ash, but only the effect of citric acid was significant. The addition of citric and malic acids also significantly increased the retention of P and phytate P (P<0.05). In experiment 2, the addition of phytase to the diet significantly increased 16-d BW gain, feed intake, percentage of bone ash, milligrams of bone ash, phytate P disappearance, and decreased the incidence of P-deficiency rickets. Methionine source did not affect 16-d BW gain, feed intake, feed efficiency, milligrams of bone ash, or P rickets incidence. However, the birds fed HMB had a higher percentage of bone ash and phytate P disappearance compared with the groups fed dl-Met only when phytase was added to the diets. The additions of citric acid and HMB improved phytate P utilization. However, the reason why some organic acids are effective whereas others are not is not apparent.

Effects of u.v. irradiation of very young chickens on growth and bone development

Six experiments were conducted to study the effects of exposure of young chickens to u.v. radiation. Chickens were fed a cholecalciferol (D3)-deficient diet and exposed to u.v. radiation from fluorescent lights giving total radiance (285-365 nm) at 0.15 m of 99.9 mJ/s per m(2). In Expt 1, chickens had increased body weight, bone ash and plasma Ca and decreased incidence of rickets and tibial dyschondroplasia (TD) when exposed to fluorescent light radiation 24 h per d, 24 h every 2 d, or 24 h every 3 d starting with exposure on day 1 after hatching. However, when not exposed on day 1, but on days 4, 7, 10, 13 and 16, the bone ash was reduced, and the incidence of TD and rickets was increased, compared with chickens exposed on day 1 after hatching. When chickens were exposed at 1 d of age to radiation from two lamps, each of which gave a radiance (285-365 nm) at 0.26 m of 856 mJ/s per m(2), both the length of time of radiation and location of the lamps (above or below the chicken) influenced the response as measured by body weight, bone ash, plasma Ca and incidence of rickets. When chickens that received a TD-inducing diet were exposed to 30 min u.v. radiation from below at 1 d of age they developed significantly less TD than did those not exposed when fed either 27.5 or 55.0 microg D3/kg diet.

Effects of ascorbic acid and 1, 25‐dihydroxycholecalciferol on alkaline phosphatase and tibial dyschondroplasia in broiler chickens

1. The effects of graded amounts of dietary ascorbic acid with or without 10 micrograms/kg dietary 1,25-dihydroxycholecalciferol on performance, blood and bone variables were measured in broiler chicks. 2. 1,25-Dihydroxycholecalciferol prevented the tibial dyschondroplasia and rickets caused by feeding a low calcium diet. Gain:food was decreased, but body weight was not affected by feeding 10 micrograms/kg 1,25-dihydroxycholecalciferol. Phytate phosphorus retention was increased by dietary 1,25-dihydroxycholecalciferol. 3. Dietary ascorbic acid did not influence the incidence of tibial dyschondroplasia, but did reduce the incidence of rickets at a dietary concentration of 250 mg/kg. Gain:food was increased when 250 or 500 mg ascorbic acid/kg diet were added along with 10 micrograms/kg 1,25-dihydroxycholecalciferol in one of two experiments. 4. Alkaline phosphatase activity and plasma 1,25-dihydroxycholecalciferol were not affected by the dietary treatments. Plasma 25-hydroxycholecalciferol concentration was decreased by dietary 1,25-dihydroxycholecalciferol. 5. Ascorbic acid had no synergistic effects with 1,25-dihydroxycholecalciferol on the blood and bone variables investigated in broiler chickens at the dietary concentrations of 1,25-dihydroxycholecalciferol used in this work.

Calcium and phosphorus requirements of the very young Turkey as determined by response surface analysis

The first experiment was a central composite rotatable design with calculated calcium levels of 6.2, 7.0, 9.0, 11.0, and 11.8 g/kg diet and total phosphorus levels of 5.2, 6.0, 8.0, 10.0, and 10.8 g/kg diet (2.8 g phytin-P/kg by analysis). This design involved three replicates for each rotatable point and fifteen replicates of the central point. The second experiment was a 4 x 4 factorial design with calculated Ca levels of 8.0, 10.0, 12.0, and 14.0 g/kg diet and calculated total P levels of 7.0, 9.0, 11.0, and 13.0 g/kg diet (2.5 g phytin-P/kg by analysis). There were four replicates for each treatment. In both 16 d experiments maize-soya-bean diets were used and each replicate consisted of one pen containing 10-d-old broad-breasted, white tom turkeys. The Ca and total P requirements for optimum growth were estimated to be 12.5 and 10.0 g/kg diet respectively. Bone ash was adequate at these levels of Ca and total P, but maximum bone ash was not achieved until much higher levels of Ca and total P were employed. At the required levels of Ca and total P for growth the incidences of Ca- and P-deficiency rickets were very low. There were no treatment effects on feed efficiency. Increasing dietary Ca decreased the incidence of the Ca-deficiency lesion. There was a quadratic response due to dietary total P on both P-deficiency rickets and plasma dialysable P; intermediate levels of dietary P resulted in low incidence of the P-deficiency lesion and high levels of plasma dialysable P. There was a strong negative correlation between the incidence of P-deficiency rickets and plasma dialysable P. Percentage retention was very low at high levels of dietary P and low levels of Ca which corresponded with slightly higher P-deficiency rickets and low plasma dialysable P. No such obvious relationships existed between Ca retention, incidence of Ca-deficiency rickets, and plasma Ca. The incidence of tibial dyschondroplasia was very low in the present study. There were pronounced dietary treatment effects on phytin-P retention; at 14 d percentage phytin-P retention treatment means ranged from 18 to 46 in Expt 1 and from 0 to 40 in Expt 2 with the highest retention of phytin-P at low levels at both Ca and total P.

Influence of Dietary Menhaden Oil on Growth Rate and Tissue Fatty Acids of the Chick

Using purified diets containing 2 sources of protein, an essential fatty acid deficiency was produced in chicks that was characterized by poor growth and a high quantity of eicosatrienoic acid in the liver lipid. The feeding of corn oil caused an increase in the eicosatetraenoic acid and a decrease in the eicosatrienoic acid content of the liver. The feeding of menhaden oil did not change the eicosate traenoic acid content of the liver lipid, but caused a complete disappearance of eicosatrienoic acid. Eicosapentaenoic acid, docosapentaenoic acid and docosahexaenoic acid were present in the liver only when menhaden oil was fed. The data indicate that the feeding of fish oil with its high content of long-chain polyunsaturated fatty acids inhibits the synthesis of eicosatrienoic acid in the chicken. When menhaden ou was fed with corn oil, the level of arachidonic acid present in the liver and heart fat was decreased from levels resulting when corn oil is fed alone. Some interpreta tions of these observations are discussed. Marine oils contain large amounts of long-chain polyunsaturated fatty acids

Ethylenediaminetetraacetic Acid and 65Zn Binding by Intestinal Digesta, Intestinal Mucosa and Blood Plasma

Summary The mechanisms of zinc absorption and the effect of EDTA (ethylenediaminetetraacetic acid) on zinc absorption were studied at the intestinal digesta, intestinal mucosa, and blood plasma levels. Dialytic and gel nitration studies showed complexing of 65Zn with free amino acids or EDTA-14C in the intestinal digesta. The EDTA-14C:65Zn complex was bound to a zinc binding protein in the intestinal mucosa (mol wt 14,000-18,000) and to a plasma protein (mol wt 65,000-70,000), that had a greater affinity for zinc than the mucosal protein. The ratios obtained for the cpm EDTA-14C:cpm 65Zn in the main peaks eluted from gel filtration columns (1.10 in intestinal digesta preparation, 1.26 in mucosa soluble fractions, and 1.26 in blood plasma) indicated strong binding of the EDTA-zinc complex. When EDTA was not present in the diet, 65Zn complexed with amino acids in the intestinal digesta and with the same mucosal and blood proteins.

Physiological Responses to Divergent Selection for Phytate Phosphorus Bioavailability in a Randombred Chicken Population

An investigation was conducted to study insulin-like growth factor (IGF)-I, IGF-II, insulin, glucagon, leptin, triiodothyronine (T(3)), and thyroxine (T(4)) levels in a chicken population divergently selected for P bioavailability (PBA). There were differences in growth and feed efficiency between the 2 lines. Concentrations of IGF-I, IGF-II, and T(3) were significantly greater in the high PBA line compared with the low PBA line, whereas the reverse was true for glucagon. There were no correlations between IGF-I and II and PBA in either line, suggesting that the line differences may be the result of factors other than PBA. Glucagon and IGF-I have different relationships with feed conversion ratio in the high PBA line compared with the low PBA line. There was a significant correlation between PBA and T(3) in the low line and between PBA and T(4) in the high PBA line. Thyroid hormone levels may be an indirect indicator of PBA in growing chickens. The genes in the thyroid hormone pathway may be key in the identification of genes associated with PBA.

Modelling the relationships of egg weight, specific gravity, shell calcium and shell thickness

1. The relationships between egg weight, egg specific gravity, shell weight, shell calcium and shell thickness of 800 eggs from 8 treatments were expressed using mathematical models. 2. The equations describing the relationships were on the basis of any two independent variables predicting the remainder. 3. Of 10 possible models, 4 had high co-efficients of determination (R2 greater than 0.80) for each predicted dependent variable. 4. The two independent variables in each of these 4 models were, in turn, egg weight and specific gravity, egg weight and shell weight, egg weight and shell thickness, and specific gravity and shell weight. 5. The best model was that having egg weight and specific gravity as independent variables, with R2 values of 0.94, 0.88, and 0.85 for predicted shell weight, shell calcium, and shell thickness, respectively. Moreover, egg characteristics can be measured non-destructively by this model, whereas the other three require destruction of the egg.