Effects of dietary fatty acids and calcium levels on performance and mineral metabolism of broiler chickens

The influence of inclusion of 8% linoleic/oleic, oleic, palmitic, and stearic acids as the major source of fat in the presence of low (.8%) and high (1.2%) calcium in broiler diets was investigated using broiler chicks from day-old to 3 weeks of age. Palmitic and stearic acid caused an increase (P less than .01) in daily feed intake and weight gain with a decrease in feed efficiency compared to oleic and linoleic acid. There was variation (P less than .01) in energy utilization with palmitic and stearic acid being essentially unavailable. An interaction (P less than .05) between type of fatty acid and dietary calcium level was observed with fat retention. Increasing dietary calcium increased fecal soap concentration (P less than .01). Palmitic and stearic acid caused a significant increase in fecal soap formation and decrease in calcium retention. A significant interaction between type of fatty acid and dietary calcium level was observed with magnesium retention. Bone ash and bone calcium level were reduced (P less than .01) in the presence of palmitic and stearic acid while oleic acid had no significant effect on these parameters. A significant interaction of fatty acid type and level of calcium was observed for bone magnesium content, while bone phosphorus was not affected. Plasma calcium level was significantly reduced (P less than .01) by the addition of fatty acids relative to the control diets. Increasing dietary calcium level did not alleviate the decrease in calcium retention and bone calcium content associated with addition of fat.

Effects of dietary levels and types of fat on performance and mineral metabolism of broiler chicks

Two experiments were conducted to investigate the effects of increasing dietary fat level from 0 to 9.0% and sources of supplemental fat (animal-vegetable fat or corn oil) on the performance and mineral metabolism in broiler chicks from day-old to 3 weeks of age. In experiment 1, increasing dietary fat level significantly (P less than .05) increased 3-week body weight and significantly (P less than .01) improved feed efficiency. There was no significant effect of the treatments on bone ash, bone magnesium, phosphorus, manganese, or zinc, although bone calcium content was significantly (P less than .01) reduced with increase in dietary fat level. Plasma minerals were not significantly affected by the diet treatments. In Experiment 2, neither source of fat, dietary calcium, nor vitamin D3 had any significant effect on performance parameters. Calcium and magnesium retention were significantly (P less than .05) reduced by dietary corn oil. Bone ash and magnesium were significantly (P less than .01) reduced when corn oil was the source of dietary fat, and there was a significant interaction between source of fat and dietary calcium level on bone calcium content. Increasing the dietary vitamin D3 from 1600 to 3200 IU/kg significantly (P less than .05) increased bone calcium content. Bone phosphorus, manganese, and zinc content were not significantly affected by the diet treatments. Plasma magnesium, phosphorus, and zinc content were not significantly affected by the diet treatments. It is concluded that increasing dietary fat, although beneficial for growth, was detrimental to calcium retention and bone calcification. Increasing dietary calcium does not seem to alleviate this problem.

Residues of polychlorinated phenols and anisoles in broilers raised on contaminated woodshaving litter

Broilers were raised for 8 weeks on litter made up of woodshavings containing high (700 micrograms/g) levels of contamination with polychlorinated phenols (PCP). The PCP levels declined in the litter over the test period while polychlorinated anisoles (PCA) increased in the highly contaminated litter. Final weights of the birds was only slightly different; however, feed conversion was slightly higher for those birds raised in the highly contaminated pens. Panelists rated the cooked samples from the birds raised on highly contaminated litter significantly lower for flavor and overall acceptability than either of the lower PCP level treatments. Residues of the odiferous pentechloroanisole were present in muscle and fat of the birds raised on the highly contaminated litter; however, residues in muscles of the birds on low level contaminated litter could not be detected. Polychlorinated anisoles were present in the fat of birds raised on normal litter but adjacent to the contaminated pens.

Influence of increasing dietary calcium and magnesium levels on performance, mineral metabolism, and egg mineral content of laying hens

The effects of increasing dietary magnesium level from .17 to .77% and calcium level from 3 to 4.2% for laying hens over a 7-week period was investigated. Increasing either dietary magnesium or calcium level had no significant effect (P greater than .05) on feed consumption, egg production, egg weight, or egg shell deformation. Increasing dietary magnesium level had no significant effect on calcium retention, although there was a significant (P less than .01) reduction in the percentage of magnesium retained. Egg shell calcium content was significantly (P less than .01) reduced and shell magnesium significantly (P less than .05) increased in response to increase in dietary magnesium content. Increasing dietary magnesium level also significantly (P less than .01) reduced bone calcium and zinc contents while concomitantly increasing bone magnesium levels. Bone ash and calcium were significantly (P less than .05) increased and bone magnesium reduced when the calcium content of the diet was increased. Plasma calcium was significantly (P less than .01) increased in dietary calcium level and significantly decreased with increased dietary magnesium. The converse was true for plasma magnesium in response to increases in dietary calcium and magnesium. Significant positive correlations were observed between mineral contents of diet and bone, bone and plasma, and plasma and shell. A negative correlation was observed between shell magnesium level and egg shell quality as assessed by deformation. An antagonistic relationship seems to exist between calcium and magnesium, and this is discussed in relation to skeletal integrity and egg shell quality.

Effects of feather cover and insulative jackets on metabolic rate of laying hens

Two experiments were conducted to determine the influence of feather cover and newly-devised insulative jackets on the heat production in Single Comb White Leghorn laying hens at 20 C. An open-circuit calorimeter was used to measure the gaseous exchange of the birds. With ad libitum feeding, birds with clipped back and breast feathers produced 6% more heat than did normally feathered hens. This difference was removed by placing jackets on the defeathered birds. The jackets also decreased the surface temperature of the feather-clipped areas, indicating an effective insulation. When the jackets were applied to naturally poor-feathered hens, fasting heat production decreased significantly, but not to the base level of that of normally feathered hens.

Influence of increasing the calcium and magnesium content of the drinking water on performance and bone and plasma minerals of broiler chickens

Calcium and magnesium contents of drinking water for broiler chicks were adjusted by additions of calcium and magnesium to provide levels of 0, 25, 50, 75, or 100 ppm Mg and 0, 50, or 100 ppm Ca, arranged in a factorial design. During a 3-week trial, increasing the water magnesium concentration significantly (P less than .05) improved feed efficiency and significantly (P less than .05) increased the incidence of swollen hocks and shortened tibia but had no effect on other measures of performance. Bone ash and bone mineral content were not significantly affected by the calcium treatment. However, increasing magnesium level to 100 ppm significantly (P less than .05) increased bone magnesium and phosphorus levels. Plasma minerals were not affected by these same water treatments.

Consequence of increased feed allowance for growing broiler breeder pullets as a means of stimulating early maturity

Two hundred and forty Hubbard X Hubbard breeder pullets, 3 weeks of age, received conventional quantities of feed according to the breeder's recommendation or 5, 10, or 20% extra feed allowance. On reaching an average weight of 2.1 kg, birds were moved to laying cages, subjected to 14 hr of light per day, and offered a breeder diet at the breeder's recommended allowance. Increased feed intake resulted in increased growth rate such that control, +5, +10, and +20% groups reached 2.1 kg liveweight at 20, 18, 18, and 16 weeks, respectively. Total feed intake was significantly less to 2.1 kg liveweight for the younger birds. The early move to the laying house subsequently resulted in early maturity. However, these birds failed to show persistency of production after peak, there being a 10% decline within a 4-week period. Control reared birds, starting production at 23 weeks, exhibited a more conventional and persistent peak egg production. There was an indication that early maturity adversely affected egg size. The significant saving in pullet feed cost warrants further trials aimed at elucidating the mechanisms affecting persistency of production in early maturing broiler breeders.

Effect of dietary protein and energy on broiler performance and production costs

Varying levels of dietary protein (16, 20, 24, 28, 32, 36%) and energy (2600, 2800, 3000, 3200, 3400, 3600 kcal [metabolizable energy] ME/kg) were fed in a factorial arrangement to broilers to determine the effect of alteration in nutrient density on performance and economic traits. Body weight and feed efficiency improved with increased dietary protein or energy. However, a significant interaction between protein and energy indicated the importance of a balanced energy: protein ratio to achieve optimum performance. Sex differences in protein requirements were observed for 49-day body weights. Returns over feed costs remained essentially constant, providing a balance between dietary protein and energy was maintained. However, an increase above 28% crude protein or 3400 kcal ME/kg resulted in reduced returns as did excessive quantities of one nutrient relative to the other. Male broilers were able to accommodate a higher level of dietary protein (24%) than female broilers (20%) before returns were reduced. Regression equations were derived for prediction of performance and economic parameters. Reliable estimates were obtained with the inclusion of protein or energy intake in addition to diet composition.

Effect of dietary protein and energy on broiler carcass composition and efficiency of nutrient utilization

Day-old broilers were offered diets varying in dietary protein (16, 20, 24, 28, 32, 36%) and energy (2600, 2800, 3000, 3200, 3400, 3600 kcal [metabolizable energy] ME/kg) to 49 days of age to determine the effect of alteration in nutrient density on carcass composition and efficiency of nutrient utilization. Abdominal and total carcass fat contents responded similarly to alterations in dietary protein and energy, whether expressed on a percentage or absolute weight basis. However, maximum protein deposition occurred with the 20% crude protein diet, in contrast to the increase in percent carcass protein observed above this level. Although percent carcass protein decreased throughout the energy range tested, absolute carcass protein remained constant regardless of the dietary energy level. Dietary protein exerted similar effects on both absolute and percent carcass moisture. However, an increase in dietary energy resulted in a decrease in percent carcass moisture and an increase in absolute carcass moisture. Protein utilization decreased with each increment of dietary protein but increases in dietary energy resulted in small increases in protein utilization throughout the range tested. Changes in dietary protein and energy resulted in small differences in efficiency of energy utilization. Regression equations derived for carcass composition demonstrated that although diet composition is inadequate as a predictor of carcass parameters, the addition of carcass moisture (%) to the equation improves the reliability of the estimate. Equations for the prediction of nutrient utilization from diet composition are also presented.

Use of single-stage low protein diets for growing Leghorn pullets

Two experiments were conducted in which growing White Leghorn pullets were fed single-stage 14% CP diets from 0 to 19 weeks. In the first trial, diet treatments were 1) conventional step-down protein, 2) reverse-protein, 3) 14% CP single-stage with methionine and lysine adjusted to 2 and 5% of CP, respectively, 4) as per 3 to 12 weeks followed by 14% CP with no amino acid constraints to 19 weeks. Each treatment was tested with 14 replicated cages each of 11 commercial strain Leghorn pullets. Single-stage 14% CP diets reduced pullet weight to 16 weeks relative to conventionalLy fed birds, although after this time no significant (P greater than .05) effect was observed. Pullets fed the reverse-protein diets were significantly (P less than .01) smaller than birds from all other treatments. During a subsequent 52-week laying period, rearing treatment had no significant effect on egg production, egg weight, shell deformation, feed intake, or Haugh units. A second trial was conducted to note the effect of energy level on the birds' response to low-protein diets. Diets of 14.4% CP were formulated to provide either 2610 or 3164-kcal ME/kg. A third treatment allowed for self-selection of two diets providing concentrated sources fo protein or energy. Each treatment was tested with nine replicate cages of 10 commercial strain White Leghorn pullets. Dietary energy had little effect on pullet development. Although birds offered the low-energy diets consistently consumed more protein, diet had no effect on body weight or carcass composition at 18 weeks. The data indicate that single-stage low-protein diets are suitable for growing pullets to maturity. Compared to a conventional step-down protein program, the single-stage 14% CP diet does not control body weight but does give comparable laying performance, albeit at reduced protein intake during rearing. The simplicity of the program is discussed relative to industry needs.

Performance of laying hens subjected to intermittent lighting initiated at 24 weeks of age

Leghorn pullets of a commercial strain were subjected to a conventional light program of constant photoperiod or an intermittent programming involving, during the house of conventional "lights-on", 45 min light (L): 15 min dark (D) from 24 to 27 weeks of age; 30 min L:30 min D from 28 to 35 weeks; and 14 min L:45 min D from 36 weeks to the duration of the trial. Each light treatment was tested with 12 replicate groups of 14 individually caged birds housed in adjacent rooms, with all birds fed a standard 15% crude protein, 2750 kcal ME/kg diet. Intermittent lighting resulted in a significant (P less than .05) reduction in feed intake and a consistent but nonsignificant (P less than .05) reduction in egg production. Egg size, egg shell quality, and albumen quality, as assessed by Haugh units, were not affected by light treatment. Due to the effect on egg production, it is concluded that intermittent lighting programs should not be initiated close to time of peak egg production.

Effect of blending and level of inclusion on the metabolizable energy of tallow and tower rapeseed soapstocks

Experiments were conducted with prime tallow (PT) and Tower rapeseed soapstocks (TSS) to determine the possible synergism between these fats by the total collection and chromic oxide (Cr2O3) apparent metabolizable energy (AME) methods as well as the true metabolizable energy (TME) assay and to examine the effect of inclusion level on the metabolizable energy (ME) values of fats. Graded levels of 0, 3, 6, and 9% of each of PT, TSS, and a 1:1 blend of the two were fed to groups of adult roosters, and the ME values of the test fats and the mixture were evaluated from a linear regression of the ME of the diets and the levels of fat inclusion. The total collection and Cr2O3 methods gave essentially the same AME values for PT as well as for TSS when these fats were fed separately. The 1:1 blend of these fats gave a somewhat higher value with the index method than with the total collection procedure. A positive synergistic effect of blending PT with TSS was observed in all three methods. Increases in the observed ME of the mixture over the calculated ME were 3.94, 5.26, and 5.72%, respectively, for the total collection, Cr2O3, and TME assays. When calculated by difference, the ME values of the two fats and the blend varied widely with inclusion level in all three assay procedures. The implications of use of a single level assay to determine the ME content of fats are discussed.

Dietary self-selection and use of reverse-protein diets for developing broiler breeder pullets

Broiler breeder pullets of a commercial strain were allowed a free-choice of diets providing concentrated sources of protein (46.3% CP, 2487 kcal ME/kg) or energy (8.6% CP, 3218 kcal ME/kg). Three replicate floor pen groups of 22 birds each were compared with control birds consuming a regular diet ad lib. Diet self-selection had no effect on growth rate (P greater than .05), while calculation of nutrient intake indicated a dietary equivalent consumed of some 18% CP 0 to 4 weeks, some 13% CP 4 to 16 weeks, and 17% CP from 16 to 20 weeks. This pattern is discussed relative to previous findings with Leghorn pullets. In a second trial birds were fed a reverse protein program, with the following diets being provided ad lib: 0 to 12 weeks, 12% CP, 3080 kcal ME/kg; 12 to 16 weeks, 16% CP, 2974 kcal ME/kg; and 16 to 20 weeks, 19% CP, 2972 kcal ME/kg. Control birds received a regular feeding program, involving a restricted feeding schedule as recommended by the breeding organization. Each diet was tested with six replicate cages of 10 birds each. Up to 8 weeks-of-age reverse protein fed birds were smaller in body size than conventionally restricted birds. However, after this time, the converse was true.

Dietary salt and pullet development

White Leghorn pullets were fed corn-soybean meal diets containing .25 (control), .175, or .1% supplemental salt to 20 weeks of age, followed by a regular laying diet to 36 weeks of age. Body weight and feed intake of the growing pullet was significantly reduced with .1% salt compared to other treatments, while in early production these same birds produced fewer eggs compared with birds fed .25% salt during rearing. It is concluded that manipulation of dietary salt levels may be used to delay sexual maturity.

Efficacy of salinomycin and stenorol against various species of Eimeria and effect on chick performance

Three experiments were designed to test the efficacy of salinomycin and stenorol against infection by various Eimeria species on cage reared broiler type chicks. Efficacy was based on a coccidial index. Sixty parts per million salinomycin alone or in combination with 50 ppm 3 nitro significantly improved the index over basal treatments or when 3 nitro was used alone. The differences in index values recorded for coban and salinomycin were not significant. Stenorol significantly improved the index and appeared to be a most effective anticoccidial product. Broiler chickens reared in floor pens to 8 weeks showed a significant reduction in weight gain when the diet contained salinomycin +3 nitro or coban. Stenorol at 3, 6, or 9 ppm reduced body weight, with linear regression for this effect being highly significant (P less than .01). No coccidiosis was observed.

Leg bone abnormalities and histopathology of caged and floor reared broilers fed diets devoid of selected vitamins and minerals

Summers et al., 1978, described an experiment in which performance and leg conditions of birds fed diets devoid of synthetic biotin, choline, folic acid, manganese, and miacin were observed and recoreded. This is a report on birds from the same experiment. Dyschondroplasia of the tibia was documented and the distal end of each tibia examined histologically. Metatarsal length and condyle depth of the distal tibia were also determined. Metatarsal length was influenced by vitamin deficiencies as well as the type of floor on which binds were raised. The depth of the intercondyle space was affected more by a manganese deficiency than by vitamin deficiencies and, in this case, was greater on plastic and litter as opposed to wire floors. There did not appear to be a correlation between the space depth and slipping of the tendons; however, a large number of birds should be examined to provide more data. Dyschondroplasia was more prevalent in choline deficient birds, particularly those birds raised on litter or plastic floors. Histology changes in relation to nutrient deficiencies were comparable to those reported previously.

Effect of thyroxine and thiouracil additions to diets containing rapeseed meal, on chick growth and carcass composition

Experiments have been conducted to study the hypothyrotic status of chicks fed rapeseed meal. Protamone supplementation did not correct growth depression due to feeding rapeseed meal although inclusion levels up to 0.1% may have induced a hyperthyrotic condition which in itself leads to a growth depressing effect. Changes in liver and carcass composition were observed when diets containing rapeseed and soybean meal were supplemented with protamone and thiouracil. It is concluded that although birds fed rapeseed meal are abnormal with respect to thyroid metabolism, it is likely that factors other than a simple reduction in serum thyroxine concentration are responsible for the growth depression observed for such birds.