Bone Ash Percentage Research Articles

Quantitative evaluation of 1-alpha-hydroxycholecalciferol as a cholecalciferol substitute for broilers

Two experiments were conducted using a corn-soybean meal diet that meets or exceeds the NRC (1984) requirements for all nutrients except cholecalciferol (D3) to determine the effectiveness of 1-alpha-hydroxycholecalciferol (1alpha-OHD3) as a substitute for D3 in the diet of young broilers. Ross × Ross mixed-sex, 1-d-old chicks were reared in Petersime battery brooders not exposed to ultraviolet light with feed and water supplied ad libitum for 16 d. In Experiment 1, D3 was fed at 0, 2.5, 5, 10, 20, and 40 microg/kg and one source of 1alpha-OHD3-(Hoffmann-LaRoche, Inc.; HLR) was fed at 0.625, 1.25, 2.5, 5, and 10 microg/kg of diet. In Experiment 2, the D3 was fed at 0, 2.5, 5, and 10 microg and two sources of 1alpha-OHD3-[HLR and Majestic Research Inc. (MRI)] were fed at 0, 0.625, 1.25, and 5 microg/kg of diet. Slope ratio analysis of data from the measurement of 16-d body weight, plasma Ca, rickets, and bone ash indicated bioavailability of the 1alpha-OHD3 as compared to D3 from 1.88 to 21.2. Percentage bone ash gave the most precise values in both experiments. Considering all the data from both experiments, the 1alpha-OHD3 appears to be approximately eight times as effective as D3 for satisfying the requirements of several criteria in two experiments with broiler chickens.

The effects of replacing dicalcium phosphate with Busumbu rock phosphate on performance and the mechanical properties of bone in growing chicks.

Three hundred, day-old broiler chicks, with an average initial weight of 41.8 +/- 1.79 g, were used in a 15-day study (10 birds per battery cage) to characterize their performance and fluorine status when dicalcium phosphate (DCP) was replaced by Busumbu rock phosphate (BRP) as the source of phosphorus in the chicks' ration. The treatments comprised a standard ration with BRP replacing 0, 25%, 50%, 75% or 100% of DCP. Replacing DCP with BRP significantly reduced the final weight of the chicks (p < 0.01), feed intake (p < 0.01), weight gains (p < 0.01) and dry matter digestibility (p < 0.05) but increased (p < 0.05) the feed-to-gain ratio. True phosphorus absorption and the percentage of phosphorus in the tibia were not affected by increasing amounts of BRP in the diet. Increasing levels of BRP in the diet linearly reduced (p < 0.01) the percentage bone ash, calcium, Ca:P ratio, ultimate breaking force, bending moment, stress, and modulus of elasticity. Leg stiffness, lameness, reduced feed intake, and a decline in general health were recorded in 10-40% of the chicks on 75% and 100% BRP, respectively. These results suggest that excessive ingestion of fluorine from the BRP caused the reduction in the chicks' performance.

Long-term effects of boron supplementation on reproductive characteristics and bone mechanical properties in gilts.

An experiment was conducted to determine long-term effects of dietary boron (B) on reproductive and bone characteristics in gilts. Weanling gilts (n = 50) were allotted to 10 pens based on weaning weight and litter origin. Pens were randomly assigned to receive one of two dietary treatments that consisted of a basal diet low in B (control) and the basal diet supplemented with 5 mg of B/kg diet as sodium borate. Gilts remained on their respective experimental diets throughout the nursery phase, growing-finishing phase, sexual maturity, breeding, gestation, and lactation. The day of first observed standing estrus was defined as puberty, and each pubertal gilt was bred via AI at the second observed standing estrus. Eight randomly selected gilts per treatment were slaughtered at d 35 of gestation for the assessment of embryonic and reproductive characteristics, bone characteristics, and tissue B concentrations. The remaining pregnant gilts (control, n = 11; 5 mg supplemental B/kg diet, n = 10) farrowed, and litter characteristics at farrowing and weaning were determined. Age at puberty was not affected (P = 0.72) by B, and neither were the number of corpora lutea on the ovaries (P = 0.44) or the total number of embryos (P = 0.95) at d 35 of gestation. Boron supplementation increased (P = 0.05) pig weaning weight and tended (P = 0.11) to increase pig birth weight; however, no other litter characteristics were affected (P > 0.12) by B. Extrinsic and intrinsic strength measures of bone were increased (P < 0.09) by B. Fat-free bone ash percentage and bone mineral concentrations were not affected (P > or = 0.19) by dietary B. Supplemental B increased (P < or = 0.06) the B concentrations of the muscle, liver, and reproductive tissues. Serum osteocalcin concentrations tended (P = 0.13) to be increased by dietary B, which may be related to increased bone turnover in B-supplemented gilts. Results indicate that B may have beneficial effects upon reproductive and bone characteristics.

Effect of Supplementation of Two Different Sources of Phytase on Egg Production Parameters in Laying Hens and Nutrient Digestiblity

Hens were fed corn-soybean meal diets containing 0.35, 0.25, 0.15, or 0.10% nonphytate phosphorus (NPP) (40 to 60 wk). Phytases A and B were added at 0.25, 0.15, and 0.10% at 250 to 300 units of phytase (FTU)/kg feed in a 3 × 3 factorial; 0.35% was a control diet. Treatments were replicated with eight cages per treatment (five hens per cage) in a randomized complete block design. Phytase supplementation had a significant effect on several production parameters: feed intake, feed conversion, and egg mass. Results showed nonsignificant effects (P < 0.06) on feed intake when hens were supplemented with phytase A or B and consumed more feed compared to the basal diet at 0.10% NPP. The feed conversion of birds fed 0.10% NPP without phytase was the least efficient compared to the other nine treatments (P < 0.05). Egg mass was significantly greater for hens supplemented with phytases A and B than for hens fed the basal diet at low (0.10%) NPP (P < 0.05). There were no significant differences in egg production, egg weight, specific gravity, Haugh units, wet shell, or dry yolk percentages. Dry shell percentage was higher among basal diets at 0.15 and 0.25% NPP in contrast to phytase, whereas albumen and dry yolk percentages were significantly higher for diets with phytase than for the basal diet at 0.10% NPP. Bone ash percentage was uncharacteristically high in hens fed 0.10% NPP without phytase; however, mortality was 22% in this group. Phytase supplementation improved Ca and P digestibilities to varying degrees. Supplementation of phytase in normal, corn-soybean meal diets improved feed intake, feed conversion, and egg mass and elicited a response in shell quality and egg components at the low (0.10%) NPP.

Effect of dietary boron on growth performance, calcium and phosphorus metabolism, and bone mechanical properties in growing barrows.

An experiment was conducted to evaluate the effects of dietary boron (B) on growth performance, bone mechanical properties, and calcium (Ca) and phosphorus (P) metabolism in pigs. Thirty-six barrows were weaned at approximately 21 d of age and randomly assigned to receive one of three dietary treatments. Treatments consisted of 1) low-B basal diet (control), 2) basal + 5 mg B/kg diet, and 3) basal + 15 mg B/kg diet. Boron was supplemented as sodium borate. Barrows remained on their respective experimental diets throughout the nursery (35 d) and growing (30 d) phases of production. Blood samples were obtained from each barrow at the end of each phase. Following the 30-d growing period, eight barrows per treatment were transferred to stainless steel metabolism crates. Barrows had an adjustment period of 7 d, followed by a 7-d total collection of urine and feces. All barrows were fed at 90% of the previous ad libitum grower intake of the control animals during the adjustment and collection periods. At the end of the 7-d collection period, barrows were killed and femurs and fibulas were harvested for the assessment of bone mechanical properties. During the nursery phase, ADG and ADFI were increased (P < 0.05) by B supplementation. Boron did not affect (P = 0.34) feed efficiency during the nursery phase. During the growing phase, ADG and ADFI were increased (P < 0.05) by B supplementation. Boron did not affect (P = 0.97) feed efficiency during the growing phase. Boron did not affect (P = 0.44) bone ash percentage, but B supplementation increased (P < 0.05) bone ash P. Ultimate shear force of the fibula was increased (P < 0.05) in barrows supplemented with 15 mg B/kg diet compared to barrows fed diets supplemented with 5 mg B/kg diet. Apparent absorption and retention of Ca and P were not affected (P > 0.05) by dietary B. These data indicate that B supplementation to pigs can increase growth and bone strength without greatly affecting Ca and P metabolism.

Influence of dietary soy and phytase levels on performance and body composition of large rainbow trout ( Oncorhynchus mykiss) and algal availability of phosphorus load

A feeding trial was designed to evaluate the influence of partial replacement of fish meal (FM) protein for soy-derived protein in large rainbow trout fed practical, high-energy diets with and without supplemental phytase. A 2×2 factorial arrangement with two soy levels (0% and 69.4% of the dietary protein from soybeans) and two phytase levels (0 and 1200 U kg −1) was used. Soy protein was derived from soy protein concentrate (SPC) and soybean meal (SBM) with a SPC:SBM protein ratio of 4:1. Diets were formulated to contain 36% and 28% crude protein and fat, respectively, and supplemented with lysine and methionine, but not with phosphorus (P). Consequently, the dietary P contents were 10.5 and 6.9 g P kg −1 for diets without and with soy-derived proteins, respectively. Three replicate groups of fish per treatment were hand-fed once daily to apparent satiety for 24 weeks. Fish grew from 0.25 kg to an average of 2.02 kg, with soy-fed fish being significantly larger at the end of the trial. Phytase had no influence on weight gain of fish. Dietary treatments did not affect feed efficiency, which averaged 0.90. Percent bone ash was statistically significantly lower in fish fed soy diets than in fish fed FM diets (means 56.4 and 57.7), but weight performance and whole body composition analyses did not confirm the modest P deficiency in fish fed soy without supplemental phytase. Phytase supplementation did not significantly increase bone ash of fish fed soy diets. P load significantly decreased from 8.5 to 4.6 g P kg −1 weight gain due to the partial replacement of FM protein for soy protein. Algal availability of P was lower with soy-based diet than with FM-based diet (23% vs. 35%), and lower in fecal matter of fish fed soy-based diets than in fish fed FM-based diets (9% vs. 27%). Results from this study show that a significant part of FM can be replaced by soy proteins for low-pollution diets, without compromising weight gain or feed efficiency in large rainbow trout fed practical diets.

Effectiveness of Natuphos phytase in improving the bioavailabilities of phosphorus and other nutrients in soybean meal-based semipurified diets for young pigs.

Crossbred pigs (n = 96, BW = 7.5 kg) were used in a 5-wk trial to determine the effectiveness of supplemental Natuphos phytase in improving the bioavailabilities of P and other nutrients in a semipurified diet with soybean meal as the only P source in the basal diet. Two available P (aP) levels (.05 and .16%) and five phytase levels (0, 350, 700, 1,050, and 1,400 units/kg of diet) were used in a 2 x 5 factorial arrangement of treatments. In addition to the 10 diets, two extra diets were formulated to supply the recommended level of aP (.32%) with 0 and 1,400 units (U) of phytase/kg of diet. Graded levels of phytase resulted in linear increases in ADG (P < .02), ADFI (P < .01 at .16% aP only), and gain:feed ratio (P < .03). Effects of adding phytase to the diet with .32% aP were observed only in the first 14 d of the study with increases in ADG (P < .06) and gain:feed (P < .02) for added phytase. Apparent digestibility (or absorption) coefficients (ADC) of DM, P, Ca, and N were estimated using chromic oxide as an indicator during wk 4 and 5. When phytase and P were added to the low P diet, the ADC of P was increased (P < .01), but only small and variable changes in the ADC of DM, Ca, and N were observed. Fecal P excretion (grams per day) decreased as microbial phytase was added (P < .01) and increased with added P (P < .01). In comparison to the results with the .32% aP diet, fecal P excretion decreased 25 to 50% by the addition of phytase. The addition of phytase to the diet with .32% aP further improved (P < .01) the ADC of P (54.5 vs 61.8%) and decreased (P < .01) fecal P excretion (1.62 vs 1.38 g/d). Characteristics of 4th metacarpals and 10th ribs were consistently improved by increasing dietary levels of both phytase and P. On the basis of an assessment of R2 values from secondorder translog equations, ADG, ADFI, P apparent absorption, bone ash percentage, and bone shear force were sensitive indicators to evaluate phytase efficacy of P availability in diets. Phosphorus equivalency of microbial phytase was calculated by using response equations for ADG and apparent P absorption. The average function of the release of P (Y, grams per kilograms) by microbial phytase (X, units per kilogram of diet) was developed with aP levels of .05 and .16%: Y = 1.546-1.504e-.0015X. The replacement of 1 g of inorganic P would require about 676 U of microbial phytase. This represents 77% of released P from phytate.

Effect of estrogen on egg production, shell quality and calcium metabolism in molted hens

Force-molted White Leghorn laying hens were implanted with 0.25, 0.5, 1 and 3 Compudose 200 pellets (24 mg 17β estradiol/pellet). Plasma estradiol increased with increasing E 2 dosages in a linear manner and decreased over time in a quadratic manner ( P < 0.01). E 2 treatment had a nonlinear effect on total plasma calcium. Oviduct weight, shell thickness and egg weight were not significantly affected by exogenous estradiol whereas tibial bone ash percentage was increased at only one dose ( P < 0.05:0.5 pellet group). Physiological supplementation with estradiol does not improve shell quality.

Effect of calcium source, dietary calcium concentration, and gestation phase on various bone characteristics in gestating gilts.

Sixty gravid crossbred gilts were allotted to a 2 x 3 x 2 factorial arrangement of treatments: two Ca sources (sun-cured alfalfa meal and CaCO3), three dietary concentrations of Ca (50, 75, and 100% of NRC requirements), and two phases of gestation (55 and 105 d). The objectives were to determine the effect of Ca source, dietary Ca concentration, and gestation phase on bone characteristics (bone breaking strength, bone ash percentage, bone density, and bone ash density in the rib, thoracic, and coccygeal bones), to correlate bone responses to determine relative bone activity, and to determine reliability of the coccygeal bones as indicators of Ca status in the body. At 55 d, rib strength and coccygeal ash content were lower (P < .01) than at 105 d of gestation. A gestation phase x Ca concentration (P < .05) interaction occurred. As Ca concentration increased, thoracic strength and rib ash responded quadratically during each gestation phase, for which at 55 d a minima and at 105 d a maxima was produced at 75% of NRC. A Ca source x Ca concentration (P < .05) interaction occurred. Gilts fed alfalfa had the lowest rib bone and ash density when fed 75% of NRC for Ca, whereas gilts fed CaCO3 were highest at this level of Ca compared with the other concentrations. Generally, all bones were positively correlated with respect to their response to dietary Ca concentration. Few negative correlations were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Possible Relationship Between Bone Strength and Rib Breakage: A Case Study

Reduced bone strength was thought to be a contributing factor to a high incidence of rib breakage noted at a commercial broiler processing plant. In two studies, percent bone ash determinations were made on birds exhibiting either intact or broken ribs. No indication was found that reduced bone strength was associated with the broken ribs, which clarified the overall review of possible causes.The approach employed in this study might be considered in similar situations where bone weakness is suspected as a single or contributing cause of a field problem.

The Relative Biological Value of the Phosphorus in Samples of Poultry Meal

Two experiments were conducted to determine the relative biological value (RBV) of phosphorus in two samples of poultry meal (PM 1 and PM 2) and to determine feeding value of these two products when incorporated into broiler diets. In Experiment 1 the phosphorus in defluorinated phosphate (DFP), the reference standard, was assigned a BV of 100 for comparative purposes. Using percentage bone ash as the criterion of response, the RBV of PM 1 and 2 were 100 and 107 and were not statistically different from that of DFP. Using a triple response method with body weight, gain:feed ratio, and percentage bone ash as the criteria of response, the RBV of PM 1 and 2 were 106 and 109, which were different (P<.05) from that of DFP. In Experiment 2, chicks were fed diets containing 5% of either Propak®, PM 1, or PM 2. Chicks fed the diet containing PM 1 grew faster than those fed diets containing Propak® or PM 2. No differences occurred in feed conversion and percentage bone ash among chicks fed the three diets.

Sample Size Required for Various Methods of Assessing Bone Status in Commercial Leghorn Hens

A study was conducted to determine the appropriate sample size required for various methods used to assess tibial bone status in commercial Leghorn hens. The methods used were in vivo bone mineral content (BMC), in vivo bone density (BD), in vitro BMC, in vitro BD, tibia bone breaking strength (TBS), and percentage bone ash (BA). Dietary total P levels of .4, .45, .5, .55, and .7% were used as treatment source of variation. Twenty hens were sampled randomly to represent each dietary treatment. The CV for each bone status comparison method was estimated and was used in a procedure to estimate the sample size requirement for detecting a difference of δ between treatments.The sample size required to detect the difference between treatment means varied depending on 1) the method used to compare bone status; 2) the difference between the treatment means to be detected as significant (δ); and 3) the level of significance (α) assumed. The sample size required for various methods are tabulated at .01, .05, and .1 level of significance and for 2.5, 5, 7.5, 10, 15, and 20% δ. To detect an actual difference of 5% from the mean to be significant, at the .05 level of significance, a sample size of 44, 22, 31, 23, 47, and 85 hens per treatment would be necessary for in vivo BMC, in vivo BD, in vitro BMC, in vitro BD, TBS, and BA methods, respectively. The estimated sample size values would help researchers in designing experiments that involve bone status comparison of commercial Leghorn hens.

Computerized Early Feed Restriction Programs for Various Strains of Broilers

Two trials were conducted with broiler chickens in a nested design of two feeding programs [ad libitum (AL) or restriction (R)] and two strains of chicks. The Trial 1 R program was 50% AL rate from 6 to 14 days of age fed to Strains A and B. The trial 2 R program was 65% AL rate from 8 to 14 days of age fed to Strain B and C. A computer-controlled feeding system was used to regulate the R program in each trial. Broilers on R programs exhibited compensatory growth at 21, 35, and 45 days of age equivalent to that of AL programs in both trials. Feed efficiency was not affected in Trial 1 by broilers fed R (1.68) versus AL (1.73) at 42 days but was significantly affected at 63 days (R = 2.15 and AL = 1.93). Trial 2 showed no significant effect of R (1.89) versus AL (2.01) on feed efficiency. Strain effects on carcass yield was determined only at 42 days in Trial 1. Feeding program did not affect percentage carcass fat (Trial 1) or abdominal fat pad size (Trial 2). Feed restriction did significantly improve percentage bone ash in Trial 2.

Effects of zeranol and two dietary levels of calcium and phosphorus on performance, carcass and bone characteristics, and calcium status in growing lambs.

Seventy-two crossbred wether lambs (average initial weight, 25.1 kg) were used to determine the interaction between zeranol treatment and two dietary levels of Ca and P (.8 and .6% vs .4 and .3% Ca and P, respectively) in a 2 x 2 factorial arrangement on performance, carcass and bone characteristics, and serum concentrations of parathyroid hormone (PTH) and Ca. Lambs were implanted on d 0 and 56 with 12 mg of zeranol. Lambs had ad libitum access to feed for 105 d. On d 99, blood samples were collected. Implanted lambs had 12% greater (P less than .01) daily feed intake, 26% greater (P less than .10) ADG, and a 12% improvement in (P less than .10) feed efficiency compared with nonimplanted lambs. Zeranol-treated lambs had increased (P less than .05) bone cortical area, breaking load, and width of the metacarpal compared with nonimplanted lambs. Lambs fed the .8% Ca and .6% P diet had a higher (P less than .05) percentage of bone ash than lambs fed the .4% Ca and .3% P diet. However, there were no differences (P greater than .05) in the percentage of Ca, P, Mg, or Zn in metacarpal bones due either to higher dietary Ca and P or to implant treatments. Serum concentration of PTH was greater (P less than .10) in lambs fed .8% Ca and .6% P than in those receiving .4% Ca and .3% P. Serum concentrations of PTH and Ca pooled across treatments were greater (P less than .05) before feeding than at 1 h after feeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of Calcium, Phosphorus, and Energy on the Incidence of Weak Legs in Heavy Male Broilers

Two feeding trials were conducted to study the effects of calcium, phosphorus, and energy on the incidence of weak legs in broilers grown to 8 weeks of age. Chicks with a stilted gait and those reluctant to move or refusing to walk were considered to have weak legs. Trial 1 consisted of three treatments in which chicks were fed corn-soybean meal-based diets containing different levels (Treatment 1 < 2 < 3) of available phosphorous (aP) and calcium (Ca). No differences occurred in body weights and feed efficiency through 6 weeks. During the 6 to 8-week period, chicks in Treatment 1 gained less (P < .05) than chicks in Treatments 2 and 3. Percentage bone ash and circumference of the middle of the bone shaft were not different among treatments. Normal chicks had longer (P < .05) bones than chicks with weak legs. Chicks with weak legs had greater bone volume (P < .05) and a higher percentage of crooked bones (P < .50) than normal chicks. A deficiency of aP and Ca was not the cause of the weak legs in these heavy male broilers.Trial 2 consisted of three treatments in which chicks were fed diets containing varying levels of metabolizable energy (ME)/kg during the starting and growing periods. Body weight and feed efficiency were unaffected by any treatment during any period of the trial. The number of chicks with weak legs at 8 weeks was unaffected by diet. Chicks with weak legs had a greater bone volume (P < .06) and a higher percentage of crooked bones (P < .05) than normal chicks.

The Effect of Varying Bone Meal Sources on Phosphorus utilization by 3-Week Old Broilers

Three experiments were conducted to determine phosphorus utilization from bone meals of chicken, catfish, swine, cattle (bovine) and an equal mixture of each of those bone meals in order to compare them with phosphorus utilization from dicalcium phosphate. In Experiment I and II, chicken bone meal was prepared from tibial bones and screened into three particle sizes, coarse, granular and fine. In Experiment III, bone meals were prepared using catfish bones and leg bones of chicken, swine, and cattle. Diets were formulated to contain .6 or .7% total phosphorus. In all experiments, birds were fed diets for 3 weeks and phosphorus utilization was assessed in terms of feed consumption, weight gain, feed conversion, bone weight, bone breaking strength and percent bone ash. Results indicated that phosphorus from the various bone meals was utilized sufficiently for broiler growth and feed efficiency; however, it was inadequate at the given levels to support maximum bone growth and development. It was found that phosphorus from dicalcium phosphate was utilized to a greater extent for broiler bone development than was phosphorus from the various bone meal sources.

The effect of dietary sodium fluoride on internal organs, breast muscle, and bones in captive American kestrels (Falco sparverius).

In 1982, 29 7-day-old American kestrel (Falco sparverius) chicks from captive stock were randomly assigned to one of three dietary regimens: (1) 10 birds were fed daily with cockerel mash (0 ppm of F-: control birds); (2) 10 birds were fed daily with cockerel mash containing 1,120 ppm of F-; (3) 9 birds were fed daily with cockerel mash containing 2,240 ppm of F-. Growth of the kestrels was not significantly affected by NaF in their diet. No significant differences were found among the 3 groups for length of duodenum, jejunum and ileum. Rectum was longer as more fluoride was added to the diet. Weights of adrenals, brain, gizzard, spleen, heart, kidneys, liver, pancreas, and pectoral muscle were not significantly affected by treatment, although kidneys, spleen and adrenals tended to become lighter. Percent bone ash was significantly (P less than 0.05) increased, while bone breaking strength was significantly (P less than 0.05) decreased by treatment.

Comparison of the Effects of Synthetic and Natural Zeolite on Laying Hen and Broiler Chicken Performance

Three experiments were conducted to investigate the effect of zeolites on laying hens (Experiments 1 and 2) and broiler chickens (Experiment 3). Each experiment used corn and soybean meal-based practical diets. Experiment 1 was a 90-day trial and used 200 40-wk-old laying hens. The basal diet contained 2.75% calcium and .7% total phosphorus. The dietary treatments were the basal diet and the basal diet plus 1.5% synthetic zeolite (SZ; Ethacal®). Experiment 2 was a 56-day trial and used 360 36-wk-old laying hens. The dietary treatments were .12, .22, .32, and .42% nonphytin phosphorus with and without 1.0% SZ and 1.0% natural zeolite (NZ; Zar-Min®). All diets contained 3.5% calcium. Experiment 3 utilized 240 broiler cockerels from 1 to 16 days. The dietary treatments were two calcium levels (.65 and 1.0%) with and without 1.0% supplementary SZ and NZ.In Experiment 1, egg specific gravity was significantly increased with SZ supplementation. Egg weight and egg production were unaffected. Phytin phosphorus retention and plasma dialyzable phosphorus were significantly reduced by SZ. In Experiment 2, egg specific gravity was not affected by SZ or NZ. Egg weight, egg production, plasma dialyzable phosphorus, and the retention of phosphorus and phytin phosphorus were significantly reduced by SZ with the effect on egg weight and egg production being the most severe at the lower levels of dietary nonphytin phosphorus. Natural zeolite had no effect on egg weight, egg production, plasma calcium, plasma phosphorus, or on the retention of calcium, phosphorus, and phytin phosphorus. In Experiment 3, weight gain and percentage tibia bone ash were significantly reduced by SZ. The SZ had no effect on the incidence and severity of tibial dyschondroplasia. Weight gain, feed efficiency, and the incidence and severity of tibial dyschondroplasia were significantly reduced and the percentage bone ash significantly increased by 1.0% calcium. Natural zeolite significantly improved feed efficiency and had no effect on any other parameter measured.

Effect of Dietary Boron Supplementation on Egg Production, Shell Quality, and Calcium Metabolism in Aged Broiler Breeder Hens

Three experiments were conducted using aged broiler breeder hens (>60 wk) to investigate the effects of supplemental B on egg production (EP), shell quality, and Ca metabolism. Experiment 1 had a 2 × 2 factorial arrangement of treatments: 1) high Ca (3.5%); 2) high Ca plus B; 3) low Ca (1.5%); and 4) low Ca plus B; using 32 60-wk-old hens. The B levels were basal and 100 ppm supplemental for the first 2 wk of the experiment and reduced to 60 ppm for the remaining 3 wk. Egg production, shell thickness (ST), and egg specific gravity (SG) were recorded weekly. In Experiment 2, 40 60-wk-old hens were divided into two groups: high and low shell quality. Each group was further divided into two subgroups and fed a low-Ca basal diet with or without supplemental B. The level of B supplementation and the experimental period was the same as in Experiment 1. In Experiment 3, 52 75-wk-old hens were force-molted. After molting, 36 hens were fed a commercial layer diet with the remaining 16 hens fed the control diet supplemented with 100 ppm B. Blood samples were taken during the nonlaying and laying periods, respectively.The results showed that B significantly (P<.05) depressed EP in Experiment 1 but not in Experiments 2 and 3. Supplemental B decreased plasma Ca when hens were fed a diet containing high Ca levels (3.5%). Supplemental B did not affect SG, ST, or Ca retention, but did significantly increase tibial bone ash percentage (P<.05). The results of these studies indicate mat pharmacological B supplementation of laying diets is not warranted.

Effects of a deficient magnesium supply during the dry period on bone turnover of dairy cows at parturition

The bone activity and bone mineral content in rib bones resected from 33 dairy cows between 3 and 8 h after parturition were measured, and the effects upon them of a deficient supply of dietary magnesium (Mg) during the last seven weeks of pregnancy were studied. The cows were fed a diet containing either 0.22% magnesium (low Mg) or 0.82% magnesium (high Mg) in the dry matter (DM), and the potassium content of both rations was increased to approximately 4.1% in the DM to reduce the absorption of magnesium. In the cows fed the low-Mg diet a fall in plasma Mg concentration was observed. In the low-Mg, low-parity cows the plasma Mg concentrations at parturition were higher than in the low-Mg, high-parity cows, i.e. 0.83 mmol/l and 0.54 mmol/l, respectively. After parturition four cows in the low-Mg, high-parity group showed clinical signs of hypocalcaemia but none of the other groups did so. The bone formation in low-parity cows was significantly (P less than 0.05) affected by Mg supply, with higher percentages of both trabecular surface covered by osteoid and osteoid volume in the low-Mg group. In the high-parity cows no significant differences in bone formation were found between the low- and high-Mg groups. An inadequate Mg supply resulted in a significantly (P less than 0.05) higher Ca content in the bone ash of low-parity cows and a significantly (P less than 0.05) higher bone ash percentage in the bone of high-parity cows.