Voluntary food and calcium intake by the laying hen

Two experiments, each of 40 d duration, are described in which a diet rich in calcium (3.5% Ca) or one deficient in calcium (1% Ca), but with oyster shell offered separately, were fed ad libitum to four laying hens. The voluntary consumption of food and oyster shell was automatically recorded every 2 h. The hourly consumption of the high Ga diet increased during the afternoon while the daily pattern of consumption was modified by the position of the egg in the clutch.

When the low Ca diet was fed with oyster shell, the daily consumption was increased but the effect of the position of the egg in the clutch was reduced. The ingestion of oyster shell was very high between 16.00 and 20.00 h when egg calcification was in progress; after the last oviposition of the clutch this elevated level of intake remained though to a lesser degree. In relation to the stage of egg formation, the voluntary intake of oyster shell increased sharply between 4 and 12 h after the former oviposition.

These results confirm that the laying hen can discriminate between food and calcium intake. It seems that appetite for calcium is firstly related to light‐dark cycles with a modulation of the afternoon peak by ovulation and then egg shell calcification.     

Dietary phosphorus supply, egg-shell deposition and plasma inorganic phosphorus in laying hens

1. In 2 experiments the effects of dietary phosphorus on relationships between plasma inorganic phosphorus concentration (Pi), shell and egg production and depletion states were measured in brown laying hens. 2. In a 12-week experiment dietary phosphorus concentrations from conventionally deficient (1.6 g non-phytate-phosphorus (PNP)/kg) to moderate excess (3.9 g PNP/kg) had little effect on egg and shell production, although there was evidence that plasma Pi concentration, when not influenced strongly by shell formation, reflected dietary phosphorus content. 3. Among birds at each dietary phosphorus concentration there was a negative linear relationship between shell weight of early eggs in the sequence and plasma Pi concentration. The relationship was apparently not affected by dietary phosphorus concentration. 4. Continued feeding of the deficient diet to 61 weeks of age did not have effects on body weight, egg and shell production, other than those associated with age, but plasma Pi and bone measurements indicated marginal phosphorus depletion. 5. In another experiment excessive dietary phosphorus (11.9 g PNP/kg) fed in a cross-over design caused small adverse effects on shell production, increased food intake and body weight and increased plasma Pi content, while there was no relationship between shell weight and plasma Pi concentration. 6. The results are consistent with an indirect effect of plasma phosphorus accumulation on shell formation, probably via an inhibitory effect on skeletal calcium release, in addition to any effect of excess dietary phosphorus on intestinal calcium availability. 7. Phosphorus requirement and status in the laying hen are complicated by the failure to recognise the contribution of digestible phytate-phosphorus to the available phosphorus supply.     

Effects of calcium intake and parity on plasma minerals and bone turnover around parturition

Eight pregnant heifers (primiparous cows) and seven pregnant cows in their second, third and forth pregnancies (multiparous cows) were assigned to two groups and fed either a low calcium (Ca) diet (Ca, 0.46%) or a high Ca diet (Ca, 0.86%) ad libitum from 3 weeks before the expected calving date to 3 days after parturition. All cows were examined for a change in dry matter intake (DMI), plasma minerals and bone turnover around parturition. The dietary Ca level did not affect the DMI in both primiparous and multiparous cows. The DMI of primiparous cows was significantly lower than that of multiparous cows (P < 0.05) in both the low and high dietary Ca groups. The dietary Ca level did not affect the concentrations of plasma Ca, phosphorus, magnesium and parathyroid hormone throughout the experimental period. Plasma phosphorus in primiparous cows was significantly higher (P < 0.05) than that of multiparous cows around parturition. Plasma Ca and magnesium tended to be higher (P < 0.10) in primiparous cows. The dietary Ca level did not affect the plasma osteocalcin (OC) level measured as bone formation or the urinary deoxypyridinoline (DPD) excretion measured as bone resorption before parturition in both primiparous and multiparous cows. After parturition, the plasma OC level was lower than it was before parturition in multiparous cows fed a low Ca diet, and in primiparous cows. There were no significant differences in urinary DPD excretion between each group before and after parturition. Both the plasma OC level and urinary DPD excretion of primiparous cows were significantly higher than those of multiparous cows in both the low and high dietary Ca groups.     

Evaluation of the dietary interaction of calcium and phosphorus in the high producing laying hen

1. In a 6 x 7 factorial experiment using 2688 22-week-old laying hens of the Lohmann-SL strain kept in cages (4 birds/cage), diets containing six calcium (20, 25, 30, 35, 40, 45 g calcium/kg) and seven phosphorus concentrations (3.2, 4.2, 5.2, 6.2, 7.2, 8.2, 16.2 g total phosphorus/kg (Pt)) were combined orthogonally. The resulting 42 treatments were replicated 8 times so that a replicate consisted of a double cage of 2 x 4 hens. The experiment lasted 40 weeks (10 x 28 days). 2. The experimental diets, based on maize and soyabean meals contained 11.5 MJ metabolisable energy/kg and 175 g/kg protein. Different dietary calcium and phosphorus contents were obtained by substituting oat hulls with limestone and dicalcium phosphate. 3. Mortality, egg production, egg weight, egg mass, food intake and food conversion efficiency were determined as well as the breaking strength, thickness of shells and the percentage of eggs with defective shells. 4. All responses measured were significantly influenced by the variance sources (calcium, phosphorus, interaction). Most of the production traits responded asymptotically to increasing dietary phosphorus concentration, the greatest increases or decreases generally being seen between 3.2 and 5.2 g Pt/kg. Further but weaker increases were seen between 5.2 and 8.2 or 16.2 g Pt/kg. 5. Increases in dietary calcium content always resulted in curvilinear responses. In all cases optimal effects were obtained with diets containing 25 g calcium/kg and the worst values at 45 g calcium/kg. The interaction between calcium and phosphorus was recognised by strong performance depressions and a high mortality at combinations of the lowest phosphorus concentration (3.2 g/kg) with high calcium contents (35 to 45 g/kg). These were largely offset by increasing dietary phosphorus. Thus, between 7.2 and 16.2 g Pt/kg and 25 and 45 g Ca/kg a plateau was formed where only small differences in egg production were observed. 6. From the three egg shell characteristics measured, breaking strength and shell thickness responded differently to the percentage of eggs with defective shells. While breaking strength and shell thickness were respectively negatively and positively influenced by increasing dietary phosphorus and calcium contents, both elements affected the proportion of eggs with defective shells.(ABSTRACT TRUNCATED AT 400 WORDS)     

Clinicopathology of gout in growing layers induced by high calcium and high protein diets

1. An experiment was conducted to test the independent and combined effects of high dietary calcium and protein concentrations on the induction of visceral gout in growing birds of a layer strain. 2. One hundred and sixty healthy birds were randomly divided into 4 groups at 35 d of age. The different groups were given 4 diets containing normal or high concentrations of dietary calcium or crude protein in a 2 x 2 factorial experiment for 30 d. The diets contained normal calcium (Ca) and crude protein (CP) (NCNP, 8.5 g Ca/kg and 175g CP/kg), high calcium and normal protein (HC, 36.3 g Ca/kg and 175 g CP/kg), normal calcium and high protein (HP, 8.8 g Ca/kg and 245 g CP/kg) or high calcium and high protein (HCHP, 36.8 g Ca/kg and 242 g CP/kg), respectively. 3. Typical visceral gout was induced by the HCHP diet. The HCHP and HC diet caused severe kidney damage. The HP diet did not cause kidney damage, but significantly increased plasma uric acid and inorganic phosphorus concentrations. 4. The HC diet significantly increased plasma uric acid, calcium and sodium, but significantly decreased plasma inorganic phosphorus, potassium and magnesium concentrations. The HCHP diet significantly increased plasma uric acid, calcium and sodium. 5. Urine volumes were significantly higher on the HCHP and HC diets than on the control. The growers raised on HC and HCHP diets had significantly higher total quantity of 24 h urinary excretion of uric acid, calcium, magnesium, inorganic phosphorus and potassium and a significantly lower 24 h urinary excretion of sodium. The growers fed on the HP diet had a higher 24 h urinary excretion of uric acid and inorganic phosphorus than the control. 6. It is concluded that growing layer birds should not be fed on layer rations.     

Role of magnesium in egg shell formation in the domestic hen

1. The effects of feeding diets containing various amounts of magnesium on plasma concentration of calcium and magnesium in the domestic hen were investigated. 2. Plasma concentrations of calcium and magnesium decreased during shell formation in all birds. 3. Plasma magnesium content and egg shell thickness were severely reduced in birds given diets containing either 207 or 132 mg Mg++/kg. 4. Using electron microscopy, a precise correlation was observed between the normal distributions of magnesium and organic material across the egg shell of the domestic hen.     

Dietary arginine silicate inositol complex during the late laying period of quail at different environmental temperatures

Arginine silicate inositol complex (ASIdagger; arginine 49.5%, silicon 8.2%, inositol 25%) is a novel material which is a bioavailable source of silicon and arginine. ASI offers potential benefits for vascular and bone health. Poor eggshell quality has been a major economic concern to commercial egg producers. Poor egg quality, skeletal abnormalities and architectural deterioration of bone tissue are common problems under hot conditions and in older birds. The effects of ASI supplementation on egg production, egg quality, levels of osteocalcin (OC) and bone mineral content were investigated in heat-stressed Japanese quail during the later part of the laying period. The birds were randomly assigned to six treatment groups consisting of six replicates of five birds each in a 2 x 3 factorial arrangement of treatments (temperatures, ASI levels). The birds were kept in wire cages in a temperature-controlled room at either 22 degrees C (TN) or 34 degrees C (HS) for 8 h/d and fed either a basal (control) diet or the basal diet supplemented with either 500 or 1000 g of ASI/kg. Heat exposure reduced egg production, egg quality and bone mineralisation when the basal diet was fed. ASI supplementation had no effect on feed intake or egg production under TN or HS conditions. However, ASI supplementation increased egg weight, shell thickness, shell weight and Haugh unit in both TN and HS groups during the late laying period. Bone mineral density (BMD) was significantly improved by ASI supplementation in both TN and HS groups. Serum osteocalcin (OC) concentrations and alkaline phosphatase (ALP) activity increased linearly with dietary ASI supplementation during the late laying period. The amount of calcium and phosphorus in the excreta decreased, while ash, mineral content, calcium and phosphorus concentrations in tibia increased in ASI-supplemented quail in both TN and HS groups during the late laying period. ASI supplementation significantly improved egg quality and bone mineralisation in quail during the late laying period and did not affect feed consumption or egg production.     

Plasma 1,25 dihydroxycholecalciferol and its free index are potentiated by ovulation dependent factors and shell formation induced hypocalcemia in the laying hens.

The time-course of the changes in blood ionized calcium, and in plasma 1,25 dihydroxycholecalciferol (1,25(OH)2D3) concentrations and its free index were studied in hens following suppression and resumption of shell formation and throughout the laying cycle in hens laying hard-shelled eggs, in hens fed a low or normal calcium diet and in hens laying shell-less eggs. The respective roles of the calcium needs for shell formation and of the reproductive status in regulation of 1,25(OH)2D3 production were analysed. Plasma 1,25(OH)2D3 decreased 3 hr after suppression of shell formation following premature egg expulsion and remained lower than that of hens laying hard-shelled eggs when premature expulsion of the eggs was continued for several days. Circulating 1,25(OH)2D3 tended to increase progressively when shell formation was resumed. Ablation of the parathyroid glands abolished this increase. In hens laying hard-shelled eggs, the plasma 1,25(OH)2D3 was higher during the period of shell secretion. Feeding hens a low calcium diet (1.2%) caused a marked increase in the plasma 1,25(OH)2D3. Ionized calcium levels tended to show reciprocal changes to plasma 1,25(OH)2D3 decreasing when calcification took place and increasing after its suppression. In hypercalcemic hens laying shell-less eggs and fed a 3.5% Ca diet, the plasma 1,25(OH)2D3 was at a high level 4 hr after ovulation and diminished thereafter. This additive stimulation does not, therefore, involve the parathyroid gland and may involve hormonal changes induced by ovulation. Vitamin D binding protein (DBP) in the plasma was at a high level in mature hens and was not affected by shell formation. Consequently, the free 1,25(OH)2D3 index fluctuated in parallel with total level of this hormone in mature hens. It is concluded that the calcium demand for shell formation modulates, in the short term, plasma 1,25(OH)2D3, via the homeostatic regulation of blood calcium by PTH, but that a large part of its increase is independent of PTH and is associated with the endocrine events concomitant with ovulation.     

The calcium and phosphorus requirements of laying hens

Two experiments were carried out with a modern hybrid laying strain to establish the calcium requirement for maximum egg production. The first experiment, with three calcium concentrations of 1.7, 2.8 and 3.9 per cent indicated that with 0.55 Per cent dietary phosphorus the requirement for calcium was between 1.7 per cent and 2.8 per cent. Dietary phosphorus supplements added to the mixed cereal diets containing 0.55 per cent phosphorus were without effect on production or the conclusions reached. In a subsequent experiment with four dietary calcium concentrations between 2.3 and 3.3 per cent there was no significant improvement in egg production above 2.6 per cent calcium.

In both experiments the lower production at the lower levels of calcium concentration was associated with reduced food intake. Measurements made in the first experiment showed an increasing shell thickness round the equator of the egg with increasing dietary calcium. In this experiment also a small practical test concerned with cracking of the egg shell in boiling water, indicated that incidence of cracks did not alter as the laying cycle progressed and that resistance to cracking was greatest at the highest dietary calcium concentration.     

Dietary phosphorus and egg shell thickness in the domestic fowl

The influence of two diets, differing only in their phosphorus content, on egg shell thickness was compared in 24 pullets in a change‐over experiment lasting 8 weeks. The mean shell thickness of the eggs laid on the low‐phosphorus diet (0.46 per cent total phosphorus) was 2 per cent greater than the mean thickness expressed interms of mg./cm.2 on the high‐phosphorus diet (1 per cent total phosphorus), and this difference was statistically significant. It is suggested that the increase in shell thickness on the low‐phosphorus diet was due to increased absorption and retention of dietary calcium, but this suggestion could not be confirmed experimentally in two balance periods of 6 days each owing to the great variations in calcium retention observed both between and within birds. The skeletal weights of birds killed after laying for approximately 11 months on one or other of the two rations showed no correlation between dietary treatment and skeletal weight, percentage egg production or mean shell thickness.     

Supplementation of pig diets in the growth and termination phases with different calcium sources

The aim of this study was to evaluate the effect of supplementation of pig diets in the growth and termination phases with different calcium sources. In experiment I, 36 whole males were distributed in randomized blocks in six groups, with six replications. A basal diet was formulated to meet the animals’ nutritional requirements except for calcium (0.09%), and the sources evaluated (calcitic limestone, monodicalcium phosphate, calcinated bone flour, and oyster flour) replaced the basal diet to provide 0.59% of total calcium. To determine the endogenous calcium, a diet containing low calcium (0.019%) was given simultaneously to another group of animals. Feces and urine were collected for determination the coefficients of apparent and true digestibility. In experiment II, 160 piglets were distributed in randomized blocks in four treatments, with five replications and four animals per experimental unit. Carcass and performance parameters, calcium concentration in bone and serum, and bone parameters were evaluated. The data were submitted to analysis of variance and factorial. The calcium source did not influence the digestibility coefficients determined by total collection (P > 0.05). The digestibility of Ca from oyster flour estimated by collection with an indicator was higher than that from the other sources (P < 0.05). Calcium sources did not interfere in the evaluated parameters (P > 0.05). The sources studied in this work can be used to supplement growing pigs’ diets.     

A comparison of the effects of two low‐calcium diets on egg production in the domestic fowl

1. Hens fed on a diet containing 0–05% calcium virtually ceased egg laying (production <4%) whereas those fed on a diet containing 0–5% Ca maintained production at between 20 and 30%.

2. After a return to a normal diet (3% Ca) egg weight, shell weight, ovarian characteristics and oviduct size were of a similar nature in the two groups, though the differences in egg weight, shell weight and shell calcium were significant at the 1 % level.

3. Bone weight and bone ash did not differ significantly between the groups but after a return to normal rations, bone weight and bone ash became higher in the group that had received the 0.05% Ca diet.

4. There were no clinical signs of bone demineralisation during the experiments.     

Effect of dietary calcium and phosphorus concentrations on retention of these nutrients by caged layers

1. A 5 3 factorial experiment was carried out with caged White Leghorn hens with 5 concentrations of calcium (26.0, 29.0, 32.5, 36.0, 39.0 g/kg) and 3 concentrations of phosphorus (4.3, 5.0 and 6.0 g/kg) for 120 d. Variables observed were hen day egg production, food consumption, shell weight, shell weight per unit surface area (SWUSA) and egg content. 2. 36.0 g calcium (Ca) and 4.3 g phosphorus (P) kg were found to be the dietary concentrations that resulted in optimal hen day egg production, shell weight, SWUSA and egg content. 3. Lack of a significant interaction between the effects of calcium and phosphorus on production parameters showed that the dietary Ca: P ratio is not of great importance for the laying hen. 4. Absolute retentions of Ca and P were inversely related to percentage retentions. 5. A balance study of calcium and phosphorus also showed optima at 36.0 g Ca and 4.3 g P per kg. 6. It was inferred that 36.0 g Ca and 5.0 g total P per kg are the optimal concentrations in diets for caged layers in a tropical climate.     

Influence of bone meal degelatinisation and calcium source and particle size on broiler performance,bone characteristics and digestive and plasma alkaline phosphatase activity

1. The current experiment was performed to elucidate the effects of degelatinised bone meal (DBM) in combination with different particle sizes of limestone or oyster shell on broiler performance, bone characteristics and digestive and plasma alkaline phosphatase (ALP) activity.

2. Treatments were applied as a 3 × 3 factorial arrangement with three sources of P (DCP, bone meal and DBM) and three particle sizes (50, 100 and 200 µm) of limestone. Chickens were given either DCP or DBM with oyster shell (523 µm), resulting in a total of 11 treatments with 5 replicates of 8 chicks.

3. Performance criteria were measured weekly. Tibia strength, ash, calcium (Ca) and phosphorus (P) content and plasma P and Ca concentration along with plasma and intestinal alkaline phosphatase (ALP) activity and P digestibility were measured on d 14 and 28.

4. Body weight and FCR were improved in chicks which were fed DBM or oyster shell in comparison to the DCP and limestone respectively (P ≤ 0.05). Performance was influenced (P ≤ 0.05) by particle size; with coarser particles BW and feed intake were increased (P ≤ 0.05). Tibia shear force and P content were reduced (P ≤ 0.001), whereas tibia shear energy, length, ash and Ca content were increased by substitution of DCP with DBM or bone meal (P ≤ 0.001; P ≤ 0.05). A significant difference was observed in the tibia length between the chicks fed oyster shell or limestone with different particles (P ≤ 0.05). Plasma P concentration was reduced in chicks were fed with DBM, bone meal and lower limestone particle size. Intestinal ALP activity was increased (P ≤ 0.001) in chicks which were fed DBM, bone meal, oyster shell or coarse particles of limestone. The P digestibility in chicks fed bone meal was lower than that of those fed DBM or DCP (P ≤ 0.01). Overall, gelatin removal from bone meal improved broiler bone characteristics through the P digestibility and intestinal ALP activity enhancement.     

Excessive cholecalciferol in a layers diet: decline in some aspects of reproductive performance and increased bone mineralisation of progeny

Feeding hens a diet containing 5,000 micrograms (200,000 ICU)/kg of cholecalciferol for four 28-d periods had no adverse effect on hen-day egg production or hatchability. Egg weight, shell quality, food consumption and fertility were significantly decreased in hens fed 5,000 micrograms/kg. of cholecalciferol compared with those fed 24 micrograms (960 ICU) cholecalciferol/kg diet. Plasma calcium increased significantly as the concentration of cholecalciferol was increased in the diet. However, no histologically detectable changes in the viscera or changes in the proportion of bone ash were observed with any concentration of the vitamin. Chicks hatched from dams receiving excessive doses of cholecalciferol (5,000 micrograms/kg) and maintained on a rachitogenic diet for 4 weeks had a significantly higher proportion of tibial ash but there was no effect on either body weight or tibial calcium.     

Metabolism of some essential minerals in ponies fed high levels of aluminum

The effect of dietary aluminum on the absorption, retention and pathways of excretion of calcium, phosphorus, magnesium, zinc, iron and copper was studied in balance trials in mature ponies in a three by three latin square experiment. A basal diet consisting of one third each of oats, beet pulp and a commercial pelleted, complete horse ration and containing 336 ppm aluminum was supplemented with AlC1(3) . 6H2O. The middle and high level aluminum diets contained 1370 and 4500 ppm aluminum respectively. There was little difference in effect between the middle level aluminum and basal diets. The ponies were in negative phosphorus balance when fed the high level aluminum diet because phosphorus absorption was suppressed. Calcium absorption was unaffected by aluminum intake but the ponies were in negative calcium balance when fed the high aluminum diet due to the greater urinary excretion of calcium by the ponies. Presumably, calcium was excreted in urine because it was not utilized in the formation of bone crystal due to the lack of phosphate. Plasma calcium was elevated and plasma phosphorus was depressed when ponies were fed the high aluminum diet. Plasma hydroxyproline concentration was increased suggesting that bone turnover was increased due to aluminum effects on phosphorus and calcium metabolism. Magnesium, zinc, iron and copper metabolism were unaffected by aluminum intake.     

Effects of time‐limited calcium meal upon food and calcium ingestion and egg quality

Food and calcium intake and egg shell strength were measured for 24 d with 40 laying hens fed on a daily ration of either 120 g of an all‐mash diet containing 3.25% Ca or 111 g of a 0.6% Ca diet plus 8.7 g of oyster shell. The additional calcium source was offered for a 3¼‐h period beginning at 09.00, 14.00 or 17.15 h.

Consumption of oyster shell was lowest in the morning. When the calcium meal was offered at this time, the hens slightly increased their calcium ingestion on oviposition days. However, calcium intake was higher on ovulation days when oyster shell was offered after 14 h. In each case, actual requirements seemed to be one of the main factors for determining calcium appetite.

Variations of food intake in relation to laying cycle were evident with the control diet but disappeared when oyster shell was offered separately in the afternoon. Consumption of low Ca diet was greater than that of control diet only when oyster shell was given in the late afternoon of days without ovulation.

The best egg shell quality was obtained by offering oyster shell between 14.00 h and 17.15 h but the difference with control was rarely significant. Practically it is recommended that oyster shell is given at least 3 h before light extinction.     

The effects of meal feeding of calcium,protein and energy on production and calcium status of laying hens

1. Laying birds were allowed free access to a basal diet (treatment 1) or were restricted to either early morning and late afternoon access to the basal diet (treatment 2) or a high‐energy diet in the morning and a high‐protein, high‐calcium diet in the afternoon (treatment 3). The sum of the components fed in treatment 3 was equivalent to the basal diet. These diets were fed for 5 weeks. In the next phase of the experiment, which lasted for 3 weeks, the compositions of the diets for treatments 2 and 3 were altered so that the intakes of dietary components approached those of birds on treatment 1.

2. In both experimental phases birds on treatment 3 produced significantly fewer eggs of smaller mean weight and shell weight. Plasma calcium, inorganic phosphorus concentrations and alkaline phosphatase activity were indicative of decreased calcium status.     

Food,calcium and water intakes by hens lit continuously from hatching

1. Five individually caged Leghorn hens, reared from hatching under continuous light and having their ovipositions uniformly scattered throughout the 24‐h period, were used to study voluntary intakes of a diet low in calcium, oyster shell and water.

2. Food intake was high just after ovulation, decreased during the first 16 h of egg formation, rose transiently 20 to 22 h after ovulation and was minimal just before oviposition.

3. Oyster shell intake was characterised by three peaks, two coincided with those of food diet but the third, occurring between 8 and 12 h after previous oviposition, could be related to the immediate calcium need of shell formation.

4. Water intake followed a similar pattern to food intake but there was an independent rise during albumen plumping (6 to 8 h after previous oviposition).     

Effect on shell strength of feeding supplemental sources of calcium to adult laying hens given insoluble grit during the rearing period

1. An experiment was conducted to determine the separate and combined effects of giving insoluble grit during the rearing period and small or large particle size (0.3 mm and 3 to 8 mm in diameter) limestone or oyster shell, as extra sources of calcium, during the laying period. 2. For the entire laying period the extra sources of calcium resulted in improved shell strength but, overall, grit-supplements during the rearing period did not affect either egg shell strength or other performance traits. 3. An analysis for interactions however revealed that limestone of larger particle size coupled with rearing period-grit resulted in improved egg-shell strength during the last quarter of the laying period.