Growth Rate Of Broilers Research Articles

Differential expression of mitochondrial electron transport chain proteins in cardiac tissues of broilers from pulmonary hypertension syndrome-resistant and -susceptible lines

Pulmonary hypertension syndrome (PHS) is a metabolic disease associated with the rapid growth rate of modern broilers. Broilers susceptible to PHS experience sustained elevation of pulmonary arterial pressure leading to right ventricular hypertrophy and ultimately heart failure. Previous studies have shown that mitochondrial function is defective in broilers with PHS; they use oxygen less efficiently than broilers without PHS. In this study mitochondrial electron transport chain (ETC) protein levels were compared in cardiac tissues from PHS resistant and susceptible line broilers using quantitative immunoblots. Seven of 9 anti-mammalian mitochondrial ETC protein antibodies tested exhibited cross-species reactivity. Six ETC proteins were differentially expressed in the right ventricles of broilers raised under simulated high altitude conditions (2,900 m above sea level). Four ETC proteins were present at higher levels in resistant line birds without PHS than in resistant line birds with PHS or in susceptible line birds with or without PHS. One ETC protein was present at higher levels in broilers without PHS than in broilers with PHS in both lines, and one ETC protein was present at lower levels in susceptible line birds without PHS than in susceptible line birds with PHS or in resistant line birds with or without PHS. Interestingly, differential expression of mitochondrial ETC proteins was not observed in the right ventricles of broilers raised at local altitude (390 m above sea level) nor was it observed in the left ventricles of broilers exposed to simulated high altitude. These results suggest that higher levels of mitochondrial ETC proteins in right ventricle cardiac muscle may be correlated with resistance to PHS in broilers.

Hen Mineral Nutrition Impacts Progeny Livability

SUMMARY A concern of nutritionists and live production personnel is to improve early flock livability and growth rate of broilers. Improvements in progeny performance through trace metal supplementation in the hen’s diet may be a method to accomplish this. The focus of this experiment was to evaluate live performance and carcass parameters of progeny from broiler breeders fed diets containing different levels and forms of Zn and Mn. Cobb 500 breeders received a control diet or diets containing supplemental Zn and Mn from inorganic sources, amino acid complexes, or a combination of the two. Body weight gain, feed conversion ratio, livability, percentage carcass without giblets, percentage abdominal fat, and percentage breast meat were measured on the progeny of 37-wk-old breeders. Feeding broiler breeders supplemental Zn and Mn from amino acid complexes improved livability of progeny without affecting growth or carcass characteristics. In conclusion, future research should address progeny carryover of Zn and Mn to improve livability during stress or disease conditions.

Quantitative feed restriction or meal-feeding of broiler chicks alter functional development of enzymes for protein digestion

1. Two experiments were performed on broiler chicks to determine the effect of either quantitative feed restriction (QFR) from 5 to 11 d of age or meal-feeding (MF) from d 5 to 17 on development of activity of enzymes associated with protein digestion. 2. Proteolytic activity of the proventriculus was reduced by QFR but unaffected by MF. 3. General proteolytic and carboxypeptidase A activities of the pancreas were reduced by QFR and MF. 4. Amino- and dipeptidase activities of the small intestine were increased by QFR. Dipeptidase activity was unaffected by MF. 5. Nitrogen retention of QFR chicks was lower immediately following feed restriction but not in the 2 weeks following return to ad libitum access to feed. 6. Feeding regimen alters functional development of the enzymes of protein digestion and may therefore influence growth rate of broilers.

Chemical composition and the nutritive quality of different wheat cultivars for broiler chickens

1. Different wheat cultivar samples were grown in replicated trials on a single site in three harvest years. A total of 23 wheat samples were harvested. Nutritionally complete, meal-form diets that included each wheat sample at 650 g/kg were used to compare broiler growth performance and determine apparent metabolisable energy (AME). The relationships were examined between these variables of nutritive value for broilers and the chemical composition and tests of quality on the wheat samples. 2. The total starch contents of the wheat samples ranged from 594 to 732 g/kg dry matter (DM). The mean total non-starch polysaccharide (NSP) content was 100 g/kg DM comprising 73·5 g/kg DM of insoluble material. Endosperm hardness ranged between 10 and 77 relative units and Beaver was the softest cultivar in two of the batches of samples. The AME of the wheat-based diets had a maximum range of 0·5 MJ/kg within each of the three batches of wheat that were tested. 3. Endosperm hardness of the wheat grains, within a harvest year, was positively correlated with broiler weight gain and the 1000-grain weight was negatively correlated with feed conversion efficiency (FCE). Starch content and gross energy were positively correlated with determined AME, and DM, 1000-grain weight and water holding capacity were negatively correlated with AME. 4. A step-wise regression technique indicated that endosperm hardness and ash content of the wheat were the explanatory variables that, within harvest years, significantly reduced the unexplained variation in broiler growth rate, feed intake and FCE. The contents of total starch, crude protein and ether extract were the explanatory variables that, within harvest years, significantly reduced the unexplained variation in AME.

Chemical composition and the nutritive quality of different wheat cultivars for broiler chickens

1. Different wheat cultivar samples were grown in replicated trials on a single site in three harvest years. A total of 23 wheat samples were harvested. Nutritionally complete, meal-form diets that included each wheat sample at 650 g/kg were used to compare broiler growth performance and determine apparent metabolisable energy (AME). The relationships were examined between these variables of nutritive value for broilers and the chemical composition and tests of quality on the wheat samples. 2. The total starch contents of the wheat samples ranged from 594 to 732 g/kg dry matter (DM). The mean total non-starch polysaccharide (NSP) content was 100 g/kg DM comprising 73·5 g/kg DM of insoluble material. Endosperm hardness ranged between 10 and 77 relative units and Beaver was the softest cultivar in two of the batches of samples. The AME of the wheat-based diets had a maximum range of 0·5 MJ/kg within each of the three batches of wheat that were tested. 3. Endosperm hardness of the wheat grains, within a harvest year, was positively correlated with broiler weight gain and the 1000-grain weight was negatively correlated with feed conversion efficiency (FCE). Starch content and gross energy were positively correlated with determined AME, and DM, 1000-grain weight and water holding capacity were negatively correlated with AME. 4. A step-wise regression technique indicated that endosperm hardness and ash content of the wheat were the explanatory variables that, within harvest years, significantly reduced the unexplained variation in broiler growth rate, feed intake and FCE. The contents of total starch, crude protein and ether extract were the explanatory variables that, within harvest years, significantly reduced the unexplained variation in AME.

Effect of pelleting and enzyme supplementation on variation in feed value of wheat-based diets fed to broiler chicks

The effect of wheat cultivar, pelleting, and enzyme supplementation was measured with a broiler chick bioassay comparing differences in feed intake, growth, FCR and metabolisable e nergy (ME) level. Samples of two wheat cultivars from each of six classes were ground and were either unpelleted or pelleted and ground before including (80%) in mash diets with or without enzyme (Avizyme 1302). Two common control diets were fed in the two bioassay series required to evaluate the 48 diets. Each diet was fed to four cages of six male broilers from 4 to 17 d of age. Apparent metabolisable energy (AME) was determined on excreta collected at 16 d of age. There was more than a 25% difference in feed intake among the 48 diets; the largest contribution of the variation was due to wheat cultivar. Feed intake was significantly increased by enzyme addition and decreased by pelleting. Variation in feed intake explained more than 70% of the variation in body weight and had only a minor association with determined AME. The AME of all wheat samples, except the two Durum wheats, was increased by both enzyme supplementation and processing. The increase in AME with processing may represent an anomaly of using different bioassay series to measure unpelleted and pelleted wheat samples or it may represent changes in AME of all wheat samples, except Durum wheats, with storage after harvesting. The relative AME and FCR measurements for the 12 wheat samples were similar whether the wheats were pelleted or not. However, there was no relationship between measurements of feed intake when the different cultivars of unpelleted and pelleted wheat were compared. The marked variation in feed intake and growth rate of broilers fed different cultivars of wheat continues to be a concern as it suggests that other factors may limit intake and prevent the broiler from obtaining the required levels of nutrients from the diet. Key words: Wheat, feed processing, enzymes, feed value, broilers

Application of the law of diminishing returns to describing the relationship between metabolizable energy intake and growth rate in broilers

Application of the law of diminishing returns to describing the relationship between metabolizable energy intake and growth rate in broilers

Genotype-by-Environment Interaction with Broiler Genotypes Differing in Growth Rate. 1. The Effects of High Ambient Temperature and Naked-Neck Genotype on Lines Differing in Genetic Background

High ambient temperature (AT) significantly depresses growth rate and meat yield of commercial broilers, thus making it a major factor hindering poultry meat production, especially in hot climates. The effects of high AT were variably moderated when feather coverage was reduced by the naked-neck gene (Na). In this study, the effects of high AT and Na were investigated in broiler progeny of hens from a sire line and two dam lines, differing in growth rate and meat yield due to different breeding histories. Heterozygous naked-neck (Na/na) males were mated with normally feathered (na/na) hens from the three lines. The 500 progeny were segregated for Na/na and na/na genotypes. After brooding, chicks of each maternal background, Na genotype, and sex were equally divided to two similar chambers and were reared on litter to 53 d of age. One chamber was set to normal AT, averaging 25 C; the second chamber was set to high AT, averaging 30 C. The high AT treatment reduced growth and meat yield in the progeny of all three groups. This reduction increased with age and was highest in the broilers produced by hens from a sire line bred for high growth rate and breast meat yield. The two other groups, produced by hens from selected and relaxed dam lines, differed in growth rate but were similarly affected by the high AT. It is suggested that the magnitude of the high AT effect depends not only on differences in potential growth rate but also on differences in overall genetic background. It was also shown that broiler performance in the final weeks could be improved by introducing the Na gene into commercial flocks. The advantage of the Na/na genotype was much more pronounced at high AT and in broilers with genetically higher growth rate and breast meat yield.

A comparison of total and digestible amino acids in diets for broilers and layers

Eleven samples of food ingredients were analysed for their total and true digestible amino acid content, apparent metabolisable energy and other components. Large batches of these ingredients were retained for a broiler and a layer experiment. Four layer diets were formulated at 0.97 and 0.90 of total and digestible amino acid requirements for egg production using the analysed ingredients. Eight broiler diets were also formulated from 1.0 to 0.91 of total and digestible amino acid requirements in starter and finisher diets. Proximate and amino acid analyses and AME values were within the normal range for the 11 foodstuffs. Digestibility of amino acids was high with very few exceptions, e.g. cottonseed meal, meat and bone meal. Diets formulated on a total or digestible amino acid basis gave no differences in egg production parameters or broiler production parameters with no effect of level of inclusion. However, the main effects showed that diets formulated on a total compared to a digestible amino acid basis gave better growth rate and feed conversion efficiency in broilers. It was concluded that nutrient specifications for layers and broilers are not sufficiently precise to be able to differentiate between 1.97 and 0.90 of requirement for egg production or 1.0 and 0.91 for broiler growth. The use of digestible amino acids may be justified in diet formulations only when unusual protein concentrates with low amino acid digestibility values are used in large amounts.

The effects of naked neck genotypes, ambient temperature, and feeding status and their interactions on body temperature and performance of broilers

The effect of ambient temperature (AT) and feeding status on body temperature (BT) were investigated in broilers of the three naked neck genotypes (Na/Na, Na, na, and na/na). From 29 to 49 d of age, chicks were reared in a temperature-controlled chamber, where AT alternated daily between 24 and 32 C. At Day 47, all birds were deprived of feed for 12 h at 32 C, followed by 12 h of ad libitum intake at 24 C, then 12 h of ad libitum intake at 32 C, and finally feed deprivation for 12 h at 24 C. Body temperature was measured at the end of each of these 12-h periods. Body weight, feed consumption, feather coverage, and breast yield were determined. The Na/na and Na/Na birds had 20 and 40% less feather mass than the na/na birds. The three genotypes had similar BW at Day 49, but the naked neck birds had a higher breast yield. At high AT, BT was positively associated with feather mass of the three naked neck genotypes. The highest BT was exhibited by the fully feathered birds, and the lowest by the homozygous naked neck birds. The feeding status also affected BT of all birds, but to a larger extent in the normally feathered than in the naked neck birds. It appears that the lower negative effects of high AT on growth rate and meat yield in naked neck broilers can be attributed to their lower BT. Thus, it is suggested that measuring BT of broilers can be used as an indicator of the level of stress imposed on them by high AT.

Season by genotype interaction related to broiler growth rate and heat tolerance

A study was conducted to evaluate the effect of genotype by environment (G x E) interaction on the performance of commercial broilers. Temperate and hot environments were established by making use of the natural climatic differences between spring and summer in western Turkey. The experimental population was produced by a full-pedigree, randomly assigned mating scheme consisting of 29 sires and five dams per sire. The sires were considered genotypes, and the G x E interaction was evaluated by regressing sire breeding values in summer on those estimated from their spring offspring. The correlation between the two seasons for weight gain from 0 to 4 wk of age was r = 0.26, significantly lower than rho = 1 (the expectation when there is no G x E interaction). This correlation was even negative (although not significantly lower than rho = 0) for weight gain (WG) from 4 to 7 wk of age and BW at 7 wk of age. Genotype by season ANOVA also revealed highly significant G x E interaction effects on all traits. These interactions suggest the presence of substantial genetic variation in the magnitude of heat tolerance. It appeared that this variation was not random, but rather related to growth potential, where genotypes that gain more weight in the spring tended to gain less weight under the hot conditions of summer.

Responses of growing broilers and laying hens to the dietary inclusion of leaf meal from Alchornia cordifolia

Studies were carried out to determine the nutrient composition of the leaf meal of the tropical browse plant, Alchornia cordifolia, and its value as a feed ingredient and colouring agent in broiler and layer diets. A. cordifolia leaf meal ( ACLM) contained (DM basis): 186.8 g crude protein, 164.3 g crude fibre, 50.1 g ether extract, 24.2 g ash, 574.6 g nitrogen free extract and 19.31 MJ gross energy kg −1. At dietary level of 75 g kg −1, ACLM significantly ( P<0.05) depressed feed intake and growth rate of broilers but was able to turn the skins, shanks and beaks of the birds conspicuously yellow in white maize-based diets. Regression analysis showed significant relationships between the level of ACLM and feed intake, growth rate, feed/gain ratio and body colour intensity ( P<0.05). At dietary levels of 0 g, 25 g, 50 g, 75 g and 100 g kg −1, the skin and shank colour scores on Roche colour fan were 0, 4.5, 5.2, 6 and 6.5, respectively. Laying hens tolerated ACLM up to 50 g kg −1 dietary level. Regression analysis showed no significant treatment effects in feed intake, egg production and feed efficiency ( P>0.05). Egg yolk colour was increased from a score of 0.8 on Roche yolk colour fan for the control to 5.2 at 25 g kg −1 dietary level, 11 at 50 g kg −1 dietary level, and 13.2 at 75 g kg −1 dietary level in white maize-based diets.

Minimum Ventilation for Modern Broiler Facilities

New functions for whole-house broiler heat production as a function of bird age using modern straight run broiler growth rates are presented and compared to values in the literature. The approximations are based on field measurements of environmental conditions in modern broiler housing, using a technique that matches predicted to actual fuel use to estimate partitioning between latent and sensible heat. Development of a program utilizing these approximations to compute ventilation and heating requirements for temperature and humidity control in broiler housing is described. The program utilizes steady-state heat and moisture balances commonly used for design purposes, with hourly or daily time steps. Data input includes bird weight and numbers, house data including overall R-value and size, inside and outside temperature, and relative humidity. The program estimates ventilation for temperature and moisture control, minimum ventilation rate, and supplemental heat required. Example predictions are provided.

Defatted Rice Bran to Restrict Growth Rate in Broiler Chickens

Implementation of bulky, high-fiber diets to delay early growth in broilers is limited by the availability of a suitable low-cost diluent. Two experiments examined the use of defatted rice bran (DRB) as a low energy diluent for use in delaying the early growth rate of broilers. Levels of up to 60% DRB were used in diets fed beginning at 3 or 7 days of age and fed for 7 or 14 days. After a period of DRB feeding, birds received diets varying in energy content to market weights at 49 or 56 days of age. Inclusion of high levels of DRB resulted in significant reduction of body weights at 21 day; at 49 or 56 days of age there were no significant differences in body weight related to early growth restriction. Initiation of DRB restriction at 3 vs. 7 days had no significant effect on live performance; however, birds fed the DRB diets for 14 days were smaller than those fed the DRB diets for 7 days. Dietary treatments did not consistently affect the incidence of mortality. The effect of imposing early nutrient restriction through using DRB under environment and managerial conditions conducive to development of ascites is yet to be determined.

The effects of heat distress environment, vitamin, and trace mineral supplementation on performance, blood constituents, and tissue mineral concentrations in broiler chickens

An investigation was carried out to determine the effects of heat distress environment and dietary vitamin and/or trace mineral supplementation on broilers from 28 to 49 days of age. Variables monitored included production criteria, serum metabolites, and gastrocnemius muscle and spleen Na, Ca, Mg, Fe, and Zn concentrations. Heat distress reduced (P<.05) weight gain, feed efficiency, serum total protein, albumin, triglyceride, uric acid, and it did not (P>.1) affect muscle and spleen trace mineral concentrations, but it increased (P<.05) serum glucose concentration. Broiler weight gain and feed efficiency decreased (P<.05) with trace mineral supplementation only. While, weight gain and feed efficiency numerically increased (P≥.1) with vitamin supplementation only, and significantly increased (P<.05) with vitamin plus trace mineral supplementation. Serum total protein and albumin decreased (P<.05) with trace mineral and/or vitamin supplementation. Other variables were not affected (P>.1) with the dietary treatments. In conclusion, optimal broiler growth rate and feed efficiency depends on certain trace mineral by vitamin interactions.

Broiler Farm Labor Efficiency Analysis of the 1950 to 1990 Period in Georgia

The purpose of this research was to evaluate the improvements in broiler farm labor efficiency by periods as the broiler industry evolved from small farm flock production to large commercial size operations from 1950 to 1990. Published results from studies made during the early years of this period showed labor requirements as great as 53 h per 1,000 birds in 1956 and 25 h per 1,000 birds in 1968. Farm labor requirements and production rates obtained by personal interview surveys during the period from 1975–1990 showed average labor requirements as low as 2.6 h per 1,000 birds by 1990 on large farms equipped for high efficiency in 1990. These results reflected faster broiler growth rates to heavier market weights combined with faster work rates from labor-saving mechanical equipment and efficiencies from large farms. This allows one person to operate flocks of 100,000 to 200,000 per batch with only part-time assistance rather than the 50,000 to 60,000 maximum of the 1970s.

Effect of growing season on growth rate and body fluid compartments of broilers

Effect of growing season on growth rate and body fluid compartments of broilers

A role for sodium bicarbonate supplements for growing broilers at high temperatures

The food intake and growth rate of broilers kept at high temperatures can be improved by supplementing the diet or the drinking water with sodium bicarbonate. The response appears to be due to the ...

Diet selection of Cockerels and the Feeding Value of Wheat

Different wheat samples can cause variation of up to 15% in the growth rate of broilers (March and Biely 1973). There is a poor relationship between the chemical composition, or the determined ME of the wheat, and it's subsequent feeding value. The diet selections of cockerels change when they are given a choice between a different wheat sample and a balancer feed (Rose and Parker 1990). An objective of this study was to determine whether wheat variety changed diet selections. A second objective was to examine any relationship between selection of wheat by cockerels and it's feeding value for broiler chickens.Six wheat varieties were grown in 1990 at sites in Yorkshire and Humberside. The samples were produced from randomized block experiments at each site. Diets that contained 70% of each of the 12 wheat samples were fed to 7-day old broilers for 14 days (Rose et al 1992). Excreta were collected for the last 4 days of the feeding trial.

The Effect of Meal Feeding on Small Intestine Weight

Two trials were conducted using feed forms of pellets and mash to determine whether parts of the digestive tract (small intestine) were enlarged by meal feeding. Results obtained show that meal feeding of broilers significantly increases small intestine weight for both mash and pellet broiler groups when compared with continuously fed broilers. The body weight, feed conversion, and mortality did not differ between the continuous-fed versus meal-fed groups. Pelleting the diet during the growing period (3 to 6 wk of age) significantly improved both growth rate and feed conversion of broilers.