High-yield Broilers Research Articles

Optimizing broiler performance using different amino acid density diets: What are the limits?

SUMMARY Broiler responses of economic interest, such as BW gain, FCR, and breast meat yield (BMY), can be optimized by increasing amino acid (AA) concentrations, improving the AA balance, or both. The AA requirements to maximize a response are lowest for BW gain, increased for FCR, and highest for BMY. A maximum performance response is reached when the response plateaus, whereas an optimal response is the one providing the highest return per input. These are usually not the same. Strategies used in linear feed formulation differ in how dietary AA are included in the diet; therefore, understanding how these strategies affect broiler responses is necessary to compare ultimate potential benefits. Minimum CP restrictions are still used even when TSAA, Lys, and Thr restrictions are set simultaneously, and AA requirements are presently expressed as either total or digestible. The use of ratios of essential AA to Lys is more popular now that synthetic Thr has become commercially available, and it will likely have an increase in use when l -valine and l -isoleucine have competitive prices. The present-day high-yield broiler has an increased responsiveness to AA density, especially for Lys, which contrasts with published requirements still in use. Increasing Lys and other AA at the beginning of the bird's life has been shown to have some positive carryover effects on performance in later periods; however, increasing the Lys and essential AA in broiler diets in the last phases of production allows compensation for BMY because of the continuous high allometric growth rate of breast muscle. Gains in performance are expected to result from increases in dietary AA density; however, the decision regarding what AA density to use will depend on the cost of feed relative to the market price of meat.

Effect of incubation temperature on nutrient transporters and small intestine morphology of broiler chickens

This study evaluated the effects of elevated incubation temperature on posthatch nutrient transporter gene expression, integrity of the intestinal epithelium, organ development, and performance in Ross 308 broiler chickens. Ross × Ross 308 fertile eggs (n = 900) were incubated at different eggshell temperatures during development. From embryonic day (ED) 1 to ED12, all eggs were incubated at 37.1°C, whereas from ED13 to ED21, the eggs were divided into 2 groups for incubation at 37.4°C (S) or 39.6°C (H). Performance characteristics were measured at day of hatch (DOH) and d 7, 14, 21, 30, and 42. Small intestine and residual yolk sacs were collected at DOH and d 2, 4, 6, and 10 and weighed individually. Intestinal samples from the duodenum, jejunum, and ileum were evaluated for mucosal morphology and relative nutrient transporter gene expression. No significant differences were found in performance or organ weights. The intestinal morphology results showed a temperature × age interaction in duodenum villus height (P = 0.02) and crypt depth (P = 0.05) and in ileum villus height-to-crypt depth ratios (P = 0.02). There was a main effect of temperature, resulting in deeper crypts (P = 0.02) in the jejunum of chicks incubated at H compared with S. In the nutrient gene expression evaluation, peptide transporter (PepT1) showed a temperature × age interaction. On DOH and d 2, 4, and 10, PepT1 expression was similar between chicks incubated at S and H. However, on d 6, chicks incubated at S had significantly higher expression of PepT1 than those incubated at H. This study presents the effects of elevated incubation temperature on small intestine morphology and relative expression of nutrient transporter mRNA in high-yield broiler chicks, which can be important for the availability of nutrients and distribution of energy.

Lysine and threonine responses in Ross TP16 male broilers

SUMMARY Today’s economy requires minimal feed cost for poultry producers to maintain a profit. Two experiments were performed to evaluate Lys (2 levels) and Thr (4 levels) factorial responses in Ross TP16 (Test Product 16) high-yielding male broilers from 14 to 28 d and 28 to 42 d of age. From 14 to 28 d (experiment 1), digestible Lys was fed at 1.12 and 1.18% of the diet. The basal diets contained digestible Thr at 0.69, 0.73, 0.77, and 0.81% of the diet, and l-Thr was added to achieve supplemented Thr diets. From 28 to 42 d (experiment 2), the basal test diet contained 1.00% digestible Lys and 0.60% digestible Thr. Additions of crystalline Lys and Thr yielded additional digestible levels of Lys (1.05% of diet) and Thr (0.64, 0.68, and 0.72% of diet). Live performance measurements in experiment 1 did not differ among treatments. In experiment 2, increasing Lys and Thr in the diet improved some live performance parameters, but 1.05% Lys may have been too high to estimate a Thr-to-Lys ratio, as indicated by significant BW gain and feed intake interactions. We conclude, based on the 28- to 42-d interactions, that a Thr-to-Lys ratio of 68 supports adequate growth in birds fed the 1.00% digestible Lys.

The influence of excessive levels of 1α-hydroxycholecalciferol on the growth and tissue appearance of market weight chickens

SUMMARY An experiment was conducted to demonstrate the growth and histological effects of feeding 1α-OH vitamin D3 (1α-OH-D3) at 0, 1, 3, and 5 times the level necessary to reduce the incidence of tibial dyschondroplasia and improve phytate P utilization in broiler chickens (0, 5, 15, and 25 µg/kg). High-yield broiler chicks were fed corn- and soybean meal-based diets and raised in floor pens to 42 d of age. The overall growth rate of birds in this trial was excellent, with 3.10-kg males and 2.63-kg females at 42 d of age. Feed efficiency was also excellent, at 1.55 and 1.70 kg of feed/kg of BW gain for males and females, respectively. Feeding 25 μg/kg of 1α-OH-D3 significantly decreased feed consumption, growth rate, and FCR. Growth depression was greater in males than in females. No gross lesions or abnormalities were observed in the heart, kidney, bursa of Fabricius, pancreas, eye, intestine, liver, spleen, lungs, or skin tissue of control birds or broilers fed 1α-OH-D3 at any level. Mild to moderate kidney mineralization occurred when broilers were fed 15 µg/kg of 1α-OH-D3.

Evaluation of the bacterial community and intestinal development of different genetic lines of chickens

The gastrointestinal tract (GIT) of each animal species provides a unique niche for specialized intestinal bacterial communities to thrive, and in poultry this is no exception. However, little is known about how the bacterial community varies among these different genetic lines of chickens, especially of those with various growth rates. Therefore, an experiment was conducted to observe and evaluate the changes in the bacterial community and GIT development of a modern multipurpose strain, high-yield strain, and a historic strain, Athens Canadian Random Bred (ACR), of broilers. All birds were fed a standard nonmedicated corn-soybean meal broiler starter diet ad libitum from 0 to 35 d of age. Intestinal measurements and bacterial analysis of the ileum were conducted at 4, 8, 14, 21, and 35 d of age. Bacterial DNA was isolated from the digesta, and the distribution of bacterial 16S rRNA sequence polymorphisms was analyzed by a combination of denaturing gradient gel electrophoresis and terminal restriction fragment length polymorphisms. The multipurpose chicks performed the best from 0 to 14 d of age; however, overall performance was similar for the multipurpose and the high-yield broilers. The ACR birds had the poorest performance at all periods measured. The overall relative weight of the jejunum and ileum was not different between the 3 genetic lines, but the ACR birds had the longest relative jejunum and ileum lengths. Furthermore, the multipurpose birds had the longest villi height, whereas the ACR birds had the shortest villi height in the jejunum and ileum at all measuring periods. Based on denaturing gradient gel electrophoresis, the multipurpose and high-yield broilers had similar bacterial communities at all ages. Regardless of the genetic line of broiler, the bacterial community changed with age. Performance, GIT measurements, and bacterial community of the ACR differed compared with the modern broilers. The results indicate that the different genetic lines of broilers have varying rates of intestinal development, which may affect performance and the bacterial community.

Incubation conditions affect leg health in large, high-yield broilers

SUMMARY Leg problems are observed in every flock of broilers, and they occur more frequently in heavy, fast-growing broilers. Factors such as genetics, growth rate, stressors, nutrition, and lighting programs can contribute to and change the prevalence of these problems in broiler production. Our previous research has shown that elevated incubation temperatures and oxygen concentrations below 21% during the last days of embryo development can negatively affect thyroid hormones, relative asymmetry and normal development of leg bones, and development of other tissues and organs that influence leg health and locomotion in broilers. This project evaluated the effects of incubation profiles on leg health of high-yielding broilers at 8 wk of age under commercial conditions. Eggs from the same breeder flocks were incubated in either single-stage or multistage machines. Hatchlings were placed in paired houses on the same farms, and at 56 d of age, leg health was evaluated. There was variability among farms and hatches: leg problems such as footpad dermatitis were more closely related to farm conditions, whereas valgus and especially hock burns were influenced by incubation conditions within each farm. However, this fieldwork demonstrated that proper incubation conditions improve broiler performance, especially in females (1.2%); may reduce leg health problems such as crooked toes; and may even improve locomotion.

Marginality and Needs of Dietary Valine for Broilers Fed Certain All-Vegetable Diets

Valine is likely the fourth limiting amino acid in most diets based on corn and soybean meal (C/SBM). However, the exact needs for Val are not well known, and information regarding it is sparse. A series of studies was conducted to validate the limitation of Val in all-vegetable diets fed to broilers, and subsequently to quantify an adequate ratio to Lys in high-yield late-developing broilers (Ross × Ross 708) from 21 to 42 d. A preliminary study was designed to evaluate the supplementation of different amino acids likely to be fourth limiting on a C/SBM-based diet, where Lys, TSAA, and Thr were supplemented but no other critical amino acids were given minimums in the formulation. Results obtained for BW gain, abdominal fat weight, and abdominal fat percentage showed that birds were more responsive (P < 0.05) to l-Val supplementation. A follow-up study using a corn-peanut meal (C/PM)-based diet formulated to be deficient in Val validated (P < 0.05) a Val deficiency based on poor growth performance and resulted in an immediate return to good performance when this amino acid was supplemented. Furthermore, the C/PM diet was compared with a nutritionally similar C/SBM diet, and no difference was observed in the performance of broilers fed these diets, thus validating the ability of the C/PM-based diet to support adequate growth of these broilers. This C/PM-based diet was used to feed gradual concentrations of Val, from levels that would be considered deficient (0.59% digestible) up to adequate (0.84% digestible Val). Results indicate that a ratio of Val to Lys of 78, or a minimum dietary value of 0.74% digestible Val (0.82% total Val), should be adequate for this high-yield broiler grown from 21 to 42 d of age.

Influence of Egg Shell Embryonic Incubation Temperature and Broiler Breeder Flock Age on Posthatch Growth Performance and Carcass Characteristics

A study was conducted to examine the posthatch growth performance of high-yielding broilers when eggs were incubated at 3 different embryo temperatures from 2 flocks of breeders at different ages (different egg size). Two thousand, four hundred eggs from 2 broiler breeder flocks (29 and 57 wk of age) of the same high-yielding strain (Cobb x Cobb) were incubated in the same incubator for 16 d at 37.5 degrees C. Following candling, the eggs from the 2 flocks were transferred into 3 hatcher cabinets at starting temperatures of 36.5 degrees C (low, L), 37.6 degrees C (middle, M), and 38.7 degrees C (high, H) and adjusted to achieve a shell temperature of 37.5 degrees C (L), 38.6 degrees C (M), and 39.7 degrees C (H) using an infrared thermometer. All chicks were taken off at 21 d of incubation, randomized into floor pens, and reared for 44 d. Body weights, feed intake, and feed conversion were determined at 21, 35, and 44 d of age. Body weight of birds from the H treatment was significantly less at 21, 35, and 44 d compared with the M birds. Birds in the L group weighed significantly less at 35 and 44 d compared with the M birds. Progeny from the older breeder flock had significantly greater BW at 1, 21, and 35 d of age, but had only numerically greater BW at 44 d when compared with birds from the younger flock. Feed conversion for the H birds was significantly higher from 0 to 21 d of age compared with the M and L birds. Broilers from the 29-wk-old breeder flock had lower cumulative feed conversion values than the birds from the 57-wk-old flock. No significant differences in mortality were observed. Posthatch performance appears to be affected by hatcher environment as determined by embryo shell temperature.

The Effect of Increased Protein Intake During the Starter and Prebreeder Periods on Reproductive Performance of Ultra High Yield Broiler Breeder Hens

This study evaluated the provision of additional protein to broiler breeder pullets during the starter and prebreeder phases and its effect on production. The effect of lower body weight during rearing was also evaluated. Pullets were fed to reach breeder recommended target weights (H) or to be approximately 90 g smaller (L) than targets. Groups of H pullets were fed starter rations (19% CP) for one (H5) or two (H6) extra weeks and then according to breeder guidelines. Separate groups of H pullets were fed a 17% CP (HHP) or 14% CP (HLP) prebreeder diet from 16 to 21 weeks. Groups of L pullets were fed a 17% CP (LHP) or 14% CP (LLP) prebreeder from 16 to 21 weeks. Frame size and carcass protein was increased and carcass fat reduced in H5 and H6 during early rearing but differences dissipated. By the onset of lay no differences existed in carcass fat, protein or ash percentages. Egg production at 65 weeks of H5 and H6 groups was marginally improved as was HHP and LHP, although none differed significantly from H. Egg production of LLP was lowest (P<0.05). H and HHP groups had the highest egg weights with L and LLP the lowest. Early stimulation of growth and frame size by providing additional protein gave moderate improvements in performance as did higher protein prebreeder diets. Lower than normal protein intake during the prebreeder phase resulted in reduced performance. L hens performed equivalently to H hens in all areas but egg size.

Increasing Amino Acid Density Improves Live Performance and Carcass Yields of Commercial Broilers

It has been a tendency for broiler integrators in the US to reduce dietary nutrient density to lower overall input costs of broiler production. Dietary nutrient density is routinely scrutinized because feed represents over half of the live production costs. Numerous nutritionists and researchers from the supplier side of poultry production are arguing that the reduced dietary nutrient density regimen currently employed by some integrators is not an effective means of increasing profitability, especially when producing large, high-yield broilers for markets geared toward saleable white meat. This research evaluates nutrient density in various phases throughout life in Ross 508 male and female broilers to better understand the impact of reduced dietary nutrient density, mimicking the reduced dietary cost scenarios used by some broiler integrators.Diets were provided to broilers in 4 phases from 1 to 14, 15 to 28, 29 to 35, and 36 to 49 d of age, in which treatments of high (H), medium (M), and low (L) amino acid densities were used. The combinations of nutrient density and feeding phases resulted in treatments of 1) HHHH, 2) HHML, 3) HHLL, 4) HMML, 5) HMLL, 6) HLLL, 7) MMMM, and 8) LLLL. Male broilers were more sensitive to amino acid density reductions than females. Reduction of nutrient density in the early feeds was detrimental for most parameters tested. High nutrient density throughout life (HHHH) optimized breast meat yield, whereas reductions in nutrient density reduced growth and breast meat yield and increased corrected feed conversion and leaf fat.Integrators feeding slow-maturing, high-yield broilers with low and moderate nutrient dense diets may produce broilers with suboptimal growth and breast meat yield, although moderate diets may result in good feed conversion.

Tryptophan Requirements of Different Broiler Genotypes

Two experiments were conducted with broiler chicks in battery brooders from 1 to 18 d of age to determine Trp requirements and to evaluate the performance of different genotypes (classic vs. high yield and male vs. female). Experiment 1 was a 6 × 2 factorial experiment, with six levels of Trp (0.09, 0.12, 0.15, 0.18, 0.21, and 0.24% of the diet) and two broiler chicken strains (male Arbor Acres Classic and Arbor Acres High Yield). Experiment 2 was a 6 × 2 factorial design with the same levels of Trp as in Experiment 1 and two sexes (males and females); Ross × Ross 308 birds were used. Both experiments had four replicate pens of eight birds each per treatment. The basal diet was based on corn (70.79%), corn gluten meal (17.44%), and gelatin by-product and poultry fat (23% of CP and 3.34 kcal/g of ME). At 18 d of age, three birds per replicate were killed, and livers and fat pads were removed. The broken-line linear model was used to estimate the chicks Trp requirement. Liver or liver fat and fat pad weights (as a percentage of body weight) were affected by dietary Trp level. In Experiment 1, the Trp requirements differed little; for gain they were 0.18 ± 0.002% and 0.17 ± 0.002%, and for feed conversion they were 0.16 ± 0.004% and 0.16 ± 0.002%, for the Classic and High Yield broilers, respectively. In Experiment 2, the Trp requirement of males was 0.17 ± 0.003% for BW and 0.17 ± 0.003% for feed conversion, and that of females was 0.17 ± 0.003% for body weight and 0.16 ± 0.001% for feed conversion. There was no apparent difference in the Trp requirement of young broilers due to genetic stock or gender (P > 0.05).