Defining normal: comparison of feed restriction and full feeding of female broiler breeders

Distinct patterns of feed intake and their association with growth performance in broilers

Improving feed utilization is a vital strategy to meet the growing global demand for meat and promote sustainable food production. Over the past few decades, significant improvements in the feed intake (FI) and feed utilization efficiency of broilers have been achieved through advanced breeding procedures, although dynamic changes in FI and their effects on the feed conversion ratio (FCR) have remained unclear. In this study, we measured individual weekly FI and body weight of 274 male broilers to characterize the dynamic FI patterns and investigate their relationship with growth performance. The broilers were from 2 purebred lines and their crossbreed and measurements were collected from 4 to 6 wk of age. Overall, a continuous increase in the weekly FI occurred from 4 to 6 wk of age, whereas the body weight gain (BWG) reached an inflection point in wk 5. The dynamic change in weekly FI was observed to follow 3 distinct FI patterns: pattern 1, a continuous weekly increase in FI; pattern 2, an increase followed by a plateau; pattern 3, an increase followed by a decrease. The prevalence of these patterns was similar in the purebred and crossbred populations: pattern 2 was most frequent, followed by a moderate proportion of pattern 1, and the lowest proportion of pattern 3. Broilers following pattern 1 displayed significantly better growth performance and feed utilization efficiency than those following pattern 3, emphasizing the importance of maintaining good appetite in the last stage of broiler production. In summary, this study has characterized the dynamic patterns of FI and their association with growth performance. Our results offer a new foundation for improving feed utilization efficiency and investigating feeding regulation in broilers.

Effect of energy level of pullet diet and age on laying performance and expression of hypothalamus-pituitary-gonadal related genes in laying hens

Dietary energy density influences feed intake (FI) and development of layer-type pullets. A total of 384 nine-wk-old Hy-Line Brown pullets were randomly assigned to one of 3 dietary treatments: fed a diet with 2,600, 2,750, and 2,900 Kcal metabolizable energy/kg (ME/kg) from 10 to 21 wk of age. The results showed that the 2,900 and 2,600 ME groups had lower feed and ME intake (P < 0.01) from 10 to 21 wk of age. The 2,600 ME pullets had heavier body weight (BW) and longer shank length (P < 0.05) at 21 wk of age than the 2,750 ME group. The eggshell percentage was increased by the 2,600 and 2,900 kcal/kg treatments (P = 0.002). Serum concentration of 17-β-estradiol (E2), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) decreased at 70 wk of age (P < 0.05). Pullet diet and its interaction with age had a significant influence (P < 0.001) on the expression of gonadotropin-releasing hormone 1 (GnRH-1) and gonadotropin-inhibitory hormone (GnIH) in the hypothalamus and of gonadotropin releasing hormone 1 receptor (GnRH-1R) and gonadotropin-inhibitory hormone receptor (GnIHR) in the pituitary. In the hypothalamus, GnRH-1 expression increased from 9 to 40 wk of age and then decreased; however, GnIH expression was highest at 70 wk of age. Follicle-stimulating hormone receptor (FSHR) expression increased (P < 0.001) at wk 40 and decreased at wk 70 compared to wk 21 at various follicular stages. In conclusion, the energy level of pullet diet had no unfavorable influence on feed intake, laying rate, egg mass, and FCR, whereas change egg weight and mortality during the laying period from 21 to 70 wk of age. during the laying period. These results suggest that pullet dietary energy can activate the expression of genes related to reproduction in the hypothalamus, whereas it plays a minor role in the regulation of genes in the pituitary and ovary. Age-induced gene expression in the hypothalamus-pituitary-gonadal (HPG) axis is associated with laying performance in hens.

Energy utilization and requirement of broiler breeders during the production phase

This study aimed to evaluate energy utilization and propose models for metabolizable and net energy requirements in broiler breeders during the egg production phase. Sixty Cobb500 broiler breeders aged between 29 and 65 wk were randomly assigned to 3 feeding levels. At each age, 6 birds were adapted for 8 d to 3 levels of metabolizable energy intake (MEi), established based on the amount of feed allocated: 1) the amount of feed recommended in the guideline, 2) 25% above, and 3) 25% below. The birds were housed in respirometry chambers for 6 d (1 adaptation, 4 feeding state, 1 fasting) to measure oxygen consumption and carbon dioxide production to calculate heat production (HP) and fasting HP (FHP). Daily measurements of feed intake, egg weight, egg production, and total excreta were recorded. Variables of MEi, HP, and retained energy (RE) in the egg were calculated, while RE in the body and its partitioning into fat and protein in the egg and body were calculated from MEi, total HP (THP), and RE in the egg. Statistical analysis involved linear regression of multiple factors with MEi and age (categorical) as the independent variables. Pearson correlation analysis was conducted to investigate the relationship between visceral mass and the evaluated variables. The study proposed mixed models for developing models of energy requirements for both metabolizable (ME) and net systems (NE). The study found that FHP (average 259 ± 20.08 kJ/kg0.75*d) remained constant throughout the production cycle regardless of the MEi level (P > 0.05). The efficiency of energy utilization for depositing protein and fat in the body changed with the bird's age. The lower error model was considered to select ME requirements for maintenance, egg, and gain efficiencies, disregarding the effect of age. The efficiencies were 0.89, 0.78, and 0.80 for maintenance, gain, and egg production, respectively. The NE was unaffected by age and showed a lower error than the ME model. The NE system was found to be more accurate in expressing the energy requirements of broiler breeders.

Effects of energy restriction during growing phase on the productive performance of Hyline Brown laying hens aged 6 to 72 wk

The aim of this study was to assess the effects of energy-restricted feeding during growing phase on the productive performance of Hyline Brown laying hens aged 6 to 72 wk. A total of 720 six-week-old layer chicks were allocated equally to 3 groups with 6 replicates of 40 pullets each, and were fed 1 of 3 diets that were nutritionally similar except for the apparent metabolizable energy corrected for nitrogen (AMEn) content. At the age of 6 to 17 wk, the pullets in the control group were given diet with 2,850 kcal/kg AMEn, and were fed ad libitum. The levels of AMEn in diet of pullets in the experimental groups were 90% (2,565 [2,850 × 90%] kcal/kg) and 80% (2,280 [2,850 × 80%] kcal/kg) of that in control group, and the daily amount of feed was restricted to the absolute quantity of the diet consumed by pullets in control group. At the age of 18 to 72 wk, all the hens were fed with the same diets ad libitum. As energy restriction increased in the growing phase, body weight (BW) dropped at the ages of 12 and 15 to 23 wk (at 23 wk: P = 0.001; at other ages: P < 0.001), but it showed no significant difference at 24 wk (P = 0.071). At 20 wk, restricting energy induced a delay in the development of sexual organs, including the ovary stroma, oviduct, and small yellow follicle (P < 0.05), as well as a delay in sexual maturity (P < 0.05). Consequently, the laying rate in the first and second periods dropped linearly (P = 0.046, 0.030, and 0.038, P < 0.001, respectively). The coefficient of variation (CV) in the BW at 19, 20, and 21 wk (P = 0.040, 0.023, and 0.042, respectively), the CV of age at first egg (P < 0.001), and CV of individual egg number at age 18 to 72 wk (P < 0.001) decreased linearly. There was a linear increase in the laying rate of hens in the later periods (at age 32-72 wk, P < 0.05), as well as in the average total egg number per hen and average laying rate at the age of 18 to 72 wk (P = 0.006). The average egg mass also showed a linear increase with increasing levels of energy restriction (P < 0.001). In summary, although appropriate energy restriction during growing phase delayed sexual maturity and sexual organ development in early-laying Hyline Brown pullets, it improved uniformity of BW, age at first egg laying, and individual egg number, and increased egg number per hen, laying rate, average egg mass, and number of settable eggs from 18 to 72 wk of age.

Intermittent fasting induces chronic changes in the hepatic gene expression of Red Jungle Fowl (Gallus gallus)

Background

Intermittent fasting (IF), the implementation of fasting periods of at least 12 consecutive hours on a daily to weekly basis, has received a lot of attention in recent years for imparting the life-prolonging and health-promoting effects of caloric restriction with no or only moderate actual restriction of caloric intake. IF is also widely practiced in the rearing of broiler breeders, the parent stock of meat-type chickens, who require strict feed restriction regimens to prevent the serious health problems associated with their intense appetites. Although intermittent fasting has been extensively used in this context to reduce feed competition and its resulting stress, the potential of IF in chickens as an alternative and complementary model to rodents has received less investigation. In both mammals and birds, the liver is a key component of the metabolic response to IF, responding to variations in energy balance. Here we use a microarray analysis to examine the liver transcriptomics of wild-type Red Jungle Fowl chickens fed either ad libitum, chronically restricted to around 70% of ad libitum daily or intermittently fasted (IF) on a 2:1 (2 days fed, 1 day fasted) schedule without actual caloric restriction. As red junglefowl are ancestral to domestic chicken breeds, these data serve as a baseline to which existing and future transcriptomic results from farmed birds such as broiler breeders can be compared.

Results

We find large effects of feeding regimen on liver transcriptomics, with most of the affected genes relating to energy metabolism. A cluster analysis shows that IF is associated with large and reciprocal changes in genes related to lipid and carbohydrate metabolism, but also chronic changes in genes related to amino acid metabolism (generally down-regulated) and cell cycle progression (generally up-regulated). The overall transcription pattern appears to be one of promoting high proliferative plasticity in response to fluctuations in available energy substrates. A small number of inflammation-related genes also show chronically changed expression profiles, as does one circadian rhythm gene.

Conclusions

The increase in proliferative potential suggested by the gene expression changes reported here indicates that birds and mammals respond similarly to intermittent fasting practices. Our findings therefore suggest that the health benefits of periodic caloric restriction are ubiquitous and not restricted to mammals alone. Whether a common fundamental mechanism, for example involving leptin, underpins these benefits remains to be elucidated.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08533-5.

In Pursuit of a Better Broiler: Welfare and Productivity of Slower-growing Broiler Breeders during Lay

Current commercial strains of broiler breeders display reproductive dysregulation when fed to satiety, but they can achieve optimal hatching egg production under feed restriction. However, chronic feed restriction in broiler breeders is a welfare concern due to physiological and behavioral signs of hunger, lack of satiety, and frustrated feeding motivation. The purpose of this study was to assess the welfare and productivity of slower-growing broiler breeders during lay. A total of 336 broiler breeders from 5 strains of slower-growing broiler breeders (3 female strains: 100 hens per strain, and 2 male strains: 12 and 24 roosters per strain) were kept in 12 identical pens throughout lay, 4 pens per combination of roosters and hens: A hens with Y roosters, B hens with Y roosters, and C hens with X roosters. According to guidelines, strain B and C hens and X roosters were slower growing strains and strain A hens and Y roosters were intermediate growing strains. Egg production was recorded daily, and settable eggs laid at 30, 40, and 50 wk of age were incubated to hatch. Growth rate, feed and water intake, and welfare indicators (feeding motivation, behavior, and physical assessment: feather coverage, foot and leg health, and keel bone status) were recorded during lay. Additionally, a subsample of 5 hens per pen was dissected for anatomical analyses. Laying rate started and peaked earlier in B hens than in A hens and remained above 70% in both strains, yielding high cumulative egg production (>165 eggs/hen) until 53 wk of age. Until 50 wk of age, fertility and hatched of fertile was high in slower growing broiler breeders, on average, above 95 and 80%, respectively. Compared to A hens, B and C hens had better feather coverage, lower feeding motivation, and lower daily water and feed intake. Results of this study suggest that slower growing broiler breeders show reduced signs of poor welfare and improved productivity during lay although susceptibility to obesity-related problems on laying rate may be strain-specific.

The effects of feed restriction, time of day and time since feeding on behavioral and physiological indicators of hunger in broiler breeder hens

Broiler breeder chickens are commercially feed restricted to slow their growth and improve their health and production, however, there is research demonstrating that this leads to chronic hunger resulting in poor welfare. A challenge in these studies is to account for possible daily rhythms or the effects of time since last meal on measures relating hunger. To address this, we used 3 feed treatments: AL (ad libitum fed), Ram (restricted, fed in the morning), and Rpm (restricted, fed in the afternoon) to control for diurnal effects. We then conducted foraging motivation tests and collected home pen behavior and physiological samples at 4 times relative to feeding throughout a 24-h period. The feed treatment had the largest influence on the data, with AL birds weighing more, having lower concentrations of plasma NEFA, and mRNA expression of AGRP and NPY alongside higher expression of POMC in the basal hypothalamus than Ram or Rpm birds (P < 0.001). R birds were more successful at and had a shorter latency to complete the motivation test, and did more walking and less feeding than AL birds in the home pen (P < 0.01). There was little effect of time since last meal on many measures (P > 0.05) but AGRP expression was highest in the basal hypothalamus shortly after a meal (P < 0.05), blood plasma NEFA was higher in R birds just before feeding (P < 0.001) and glucose was higher in Ram birds just after feeding (P < 0.001), and the latency to complete the motivation test was shortest before the next meal (P < 0.05). Time of day effects were mainly found in the difference in activity levels in the home pen when during lights on and lights off periods. In conclusion, many behavioral and physiological hunger measures were not significantly influenced by time of day or time since the last meal. For the measures that do change, future studies should be designed so that sampling is balanced in such a way as to minimize bias due to these effects.

Impact of broiler breeder growth trajectory on plasma corticosterone concentration: a comparison of analytical methods

Blood concentration of corticosterone (CORT) is a measure of welfare in feed restricted broiler breeders. The RIA and ELISA have been routinely used for measuring CORT in blood, excreta, and feather. Due to the presence of some confounding factors in the aforementioned colorimetric enzyme reaction methods, some methodological difficulties have been attributed to those assays. The correlation between broiler breeder plasma CORT concentrations, measured using ELISA and a novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, was the focus of the current study. A total of 36 broiler breeder pullets were used, of which 30 were randomly assigned to one of 10 unique growth trajectories, and 6 were assigned to an unrestricted group. We designed the growth trajectories using a 3-phase Gompertz growth model with 10 levels of BW gain in the prepubertal and pubertal growth phases, ranging from the breeder-recommended target BW (CON) to 22.5% higher (CON+22.5%), in 2.5% increments. The BW trajectories were applied to each individual bird using a precision feeding (PF) system, which collected BW and feed intake data. The birds were classified based on age at first egg (AFE), and 12 birds each having the highest and lowest AFE was selected for the CORT study. Then median photostimulation BW of the candidate birds was used to define the upper (heavy BW) and lower (standard BW) extremes, and plasma CORT levels were evaluated by ELISA and LC-MS/MS methods from their blood collected at 18, 20, 22, 24, and 26 wk of age. Concentrations of plasma CORT measured using ELISA method were highly correlated (r = 0.95; P < 0.001) with values measured using LC-MS/MS method, validating interchangeably usage of both methods to measure plasma CORT in broiler breeders. Plasma CORT levels were not affected by photostimulation BW or breeders' age, indicating same welfare status between the precision fed high and low BW groups.

Effect of feed restriction on the maintenance energy requirement of broiler breeders

Objective

This study aimed to evaluate the effect of the ad libitum and restricted feeding regimen on fasting heat production (FHP) and body composition.

Methods

Twelve Hubbard broilers breeders were selected with the same body weight and submitted in two feeding regimes: Restricted (T1) with feed intake of 150 g/bird/d and ad libitum (T2). The birds were randomly distributed on the treatments in two runs with three replications per treatment (per run). The birds were adapted to the feed regimens for ten days. After that, they were allocated in the open-circuit chambers and kept for three days for adaptation. On the last day, oxygen consumption (VO₂) and carbon dioxide production (VCO₂) were measured by 30 h under fasting. The respiratory quotient (RQ) was calculated as the VCO₂/VO₂ ratio, and the heat production (HP) was obtained using the Brower equation (1985). The FHP was estimated throughout the plateau of HP 12 hours after the feed deprivation. The body composition was analyzed by dual-energy X-ray absorptiometry scanning at the end of each period. Data were analyzed for one-way analysis of variance using the Minitab software.

Results

The daily feed intake was 30 g higher to T2 (p<0.01) than the T1. Also, the birds of the T2 had significatively (p<0.05) more oxygen consumption (+3.1 L/kg^0.75/d) and CO₂ production (+2.2 L/kg^0.75/d). That resulted in a higher FHP 359±14 kJ/kg^0.75/d for T2 than T1 296±17.23 kJ/kg^0.75/d. In contrast, the RQ was not different between treatments, with an average of 0.77 for the fasting condition. In addition, protein and fat composition were not affected by the treatment, while a tendency (p<0.1) was shown to higher bone mineral content on the T1.

Conclusion

The birds under ad libitum feeding had a higher maintenance energy requirement but their body composition was not affected compared to restricted feeding.

Effects of Nutritional Restriction during Laying Period of Fat and Lean Line Broiler Breeder Hens on Meat Quality Traits of Offspring

Simple Summary

The meat quality of livestock products is widely appreciated. Maternal nutrition can affect the deposition of nutrients in eggs, and then change the apparent metabolism, development process, and performance of offspring. Our research indicated that meat quality traits are also affected by maternal nutritional level and are related to the nutritional requirements of different genotypes. Some of the effects disappeared at the end of the growth stage. These situations remind poultry producers to consider the impact of feed restrictions on the quality of meat for future generations.

Abstract

The offspring meat quality of hens undergoing a 25% dietary restriction treatment during the laying period were evaluated in fat and lean line breeder. A total of 768 female birds (384/line) were randomly assigned to four groups (12 replicates/group, 16 birds/replicates). Maternal feed restriction (MFR) and normal started at 27 weeks of age. Offspring broilers were fed ad libitum. The offspring meat quality traits and muscle fiber morphology in different periods were measured. At birth, significant interactions were found on breast muscle fiber morphology (p < 0.05). At 28 days, MFR decreased breast water content and increased thigh crude fat content, and significant interactions were observed on breast crude fat and protein contents (p < 0.05). At 56 days, MFR affected morphology of peroneus longus muscle tissue, and significant interactions were found on thigh redness at 48 h and amino acid contents in breast and thigh muscle (p < 0.05). Overall, MRF may lead to offspring birth sarcopenia. Such offspring grow more easily to deposit fat in a nutritious environment, but they will self-regulate adverse symptoms during growth and development. The two lines respond differently to maternal nutritional disturbance due to different nutritional requirements and metabolic patterns.

Effects of energy-restricted feeding during rearing on sexual maturation and reproductive performance of Rugao layer breeders

The aim of this study was to assess the effects of energy-restricted feeding during rearing on the sexual maturation and reproductive performance of Rugao layer breeders. A total of 2,400 8-wk-old Rugao layer breeders were randomly assigned to one of 5 groups (480 pullets per group) with eight replicates and were fed one of 5 diets that were nutritionally similar with the exception of apparent metabolizable energy corrected for nitrogen (AME_n) content (2,850, 2,750, 2,650, 2,550, and 2,450 kcal AME_n/kg) from 8 to 18 wks of age. The daily amount of feed was restricted to the absolute quantity of the diet consumed by laying hens fed 2,850 kcal AME_n per kg diet ad libitum (control). From 18 to 52 wks of age, all hens were fed basal diets ad libitum. The body weight of layer breeders at 18 wks of age decreased linearly with increasing energy restriction (P < 0.001), but caught up within 3 wks of ad libitum feeding (P = 0.290). The coefficient of variation of the body weight of the hens at 18, 21, and 24 wks of age decreased linearly (P = 0.010, 0.025, and 0.041, respectively) with increasing energy restriction during rearing. Energy-restricted feeding delayed sexual organ development at 18, 20, and 22 wks of age, including the number of large yellow follicles, oviduct length, oviduct length index, oviduct index, and ovary stroma index (P < 0.05), and delayed sexual maturity, including the age at laying the first egg and the age at 5% and 50% egg production (P = 0.042, 0.004, and 0.029, respectively). Consequently, egg number from 5% to 50% egg production decreased linearly as the degree of energy restriction increased (P = 0.001) and egg production of hens in the energy-restricted feeding groups was lower than that of hens in the ad libitum feeding group (6.36, 6.43, 6.4, and 4.61% vs. 14.29%; P < 0.05) from 18 to 20 wks of age. Furthermore, egg weight increased linearly as energy restriction increased (P < 0.001) and laying hens in the most severe energy-restricted feeding group had more setting eggs (normal eggs weighing >40 g) than hens in the ad libitum feeding and lighter energy-restricted feeding groups (149.57 vs. 144.34, 142.66, 143.63, and 141.78; P < 0.05). No significant differences were observed in fertility, hatchability of fertile eggs, and hatchability of setting eggs (P = 0.381, 0.790, and 0.605, respectively). In conclusion, moderate energy restriction (85.97%, 2,450 vs. 2,850 kcal AME_n/kg) from 8 to 18 wks of age increased egg weight as well as the production of setting eggs in native layer breeders throughout the laying period, without adverse effects on productive performance from 18 to 52 wks of age, or fertility and hatchability at 52 wks of age.

Feeding, feed-seeking behavior, and reproductive performance of broiler breeders under conditions of relaxed feed restriction

Broiler breeders are feed restricted to optimize reproductive performance. A randomized controlled study was conducted to investigate the effect of increasing female broiler breeder BW on feeding, feed-seeking behavior, and reproductive performance. It was hypothesized that a greater BW would decrease feeding and feed-seeking behavior, and reduce reproductive performance. Ross 708 female broiler breeders (n = 36) were fed using a precision feeding system from 2 to 42 wk of age. Ten BW trajectories were created from a multiphasic Gompertz growth model that increased growth from 0 to 22.5% in the prepubertal and pubertal phases of growth, in 2.5% increments. Six unrestricted birds were not limited to a maximum BW. Body weight was evaluated as a 2-way ANOVA. Two linear regression analyses were conducted, one which included all birds and one which excluded the unrestricted birds. For the regression analyses, BW at photostimulation (22 wk of age) was used as the continuous independent variable to represent the degree of variation between trajectories. Differences were reported at P ≤ 0.05. Body weight increased as trajectory-specific BW targets increased from 6 to 28 wk of age. Differences of BW between BW trajectories decreased during the laying period, which was a result of individual bird variation within BW trajectories. Station visit frequency decreased per kilogram increase in BW for all birds during rearing and lay, and within feed-restricted birds during lay only. The number of meals and ADFI increased with age, which reflected nutrient intake to support maintenance, growth, and reproductive requirements. Mean egg weight (EW) of all birds increased by 0.72 g per kilogram increase in BW from 22 to 41 wk of age. From 22 to 29 wk of age, mean EW of feed-restricted birds increased by 2.78 g per kilogram increase in BW. For every kilogram increase in BW, age at first egg comparing all birds decreased by 10.83 d. Two unrestricted birds came into lay before photostimulation. In contrast with the hypotheses, BW increased up to 22.5% above the recommended target did not reduce feeding and feed seeking behavior, or negatively impact reproductive performance.

Effect of Qualitative Feed Restriction in Broiler Breeder Pullets on Stress and Clinical Welfare Indicators

The feed restriction applied during rearing of broiler breeders inflicts chronic hunger, and frustration due to unfulfilled behavioural needs for feeding. To alleviate the welfare problems associated with feed restriction, qualitative feed restriction allows a larger amount of feed to be provided without increasing the energy intake. In the present study, the aim was to investigate the effect of scatter-fed qualitative feed restriction on a range of welfare indicators in broiler breeders at the end of the rearing period. In total, 1,200 female breeder chicks of the genotype Ross 308 were housed in 24 pens: six pens of initially 50 birds per dietary treatment. The treatments were: (1) standard feed (Control), (2) standard feed diluted with oat hulls (Insoluble), (3) standard feed diluted with oat hulls and sugar beet pulp (Mixed), and (4) standard feed plus maize silage (Roughage). At 15 weeks of age, a blood sample was taken from 40 birds (10/treatment) five times within 24 h. The plasma was analysed for corticosterone concentration. At 19 weeks of age, a clinical welfare assessment was performed on all birds before they were sacrificed. From each bird, three feathers were plucked and macroscopically examined for the presence of fault bars. Feather length and weight were also recorded. Mortality was registered on occurrence throughout the rearing period. Treatment affected the plumage condition, footpad dermatitis, plumage dirtiness, vent pasting, and number of severe fault bars (P ≤ 0.05) but not plasma corticosterone concentration, hock burns, hyperkeratosis and mortality (P ≥ 0.17). There was an effect of the interactions between treatment and feather type on the total number of fault bars per feather, average position of the fault bars relative to the base of the feather, and growth rates of feather mass and length (P < 0.0001). Overall, the results showed improved welfare of Roughage birds and reduced welfare of Mixed birds, whereas the welfare of Insoluble birds did not seem to differ noticeably from that of Control birds. We recommend to further develop a feeding strategy that includes daily allocation of roughage to broiler breeders during the rearing period.

Impact of an alternate feeding program on broiler breeder pullet behavior, performance, and plasma corticosterone

Broiler breeders are commonly feed restricted using some variation of skip-a-day feeding to prevent excessive body weight (BW) gain and poor flock uniformity that results in lower production levels. However, the level of feed restriction has increased leading to negative effects on broiler breeder welfare. Research needs to be conducted to evaluate alternative feeding programs to diminish the negative impact of restricted feeding on bird welfare. This research examined pullets that were fed soybean hulls (alternate day feeding, ATD) on the off day of a traditional skip-a-day feeding program in comparison to the standard skip-a-day program (SAD). The 2 dietary feeding treatments each had 3 replicate pens of 210 pullets each and were fed from wk 5 to 21 of age. Nitrogen-corrected true metabolizable energy and digestible amino acid coefficients of soybean hulls were determined. Body weight in the ATD feed program was significantly higher (P < 0.001) than the birds on the SAD feed program until 16 wk of age. Feed allocations for the SAD feeding program was increased at 11 wk of age to achieve similar BW prior to photo stimulation. The ATD feed program significantly improved BW uniformity of the birds for weeks 8, 12, 16, and 20. Hens fed on the SAD feed program had a lower mean egg production than the hens fed on the ATD program. There were significant differences on plasma corticosterone concentrations between the feeding days (24 or 48 h after feeding) in both feed programs. There was a shift in the behavior of the birds with significant differences in the feeding, foraging, and comfort behaviors between the feeding programs on the same feed day. Overall, feeding the ATD females soybean hulls on the off feed day improved the BW uniformity and egg production, but further research will be needed to determine potential differences in nutrient utilization or behavior of the pullets that positively impacted this flock performance.

Effect of age at photostimulation on sexual maturation and egg-laying performance of layer breeders

The objective of this study was to determine the effect of age at photostimulation on sexual maturity and performance of layer breeders. A total of 192 fourteen-wk-old White Leghorn (WL) breeder hens were randomly allocated to 4 treatments of 48 birds each, with 2 replicates per treatment. The birds were photostimulated at 16 (PS16), 18 (PS18), 20 (PS20), and 22 (PS22) wk of age. Four birds per treatment were randomly selected to evaluate sexual organ development at 1 D before photostimulation and 2, 4, and 6 wk after photostimulation. The ovary weight, large yellow follicles number (LYF), oviduct weight, and oviduct length of PS18 increased sharply after photostimulation. Conversely, the increase in PS16 was not observed until 2 wk after photostimulation. There was no difference in age at sexual maturity between treatments (P > 0.05). The PS16 had the longest interval (28 D) from photostimulation to 5% egg production, while PS22 reached 5% egg production 7 D before photostimulation. The PS22 had lower peak production (P = 0.02) and less egg production (P = 0.02) than other treatments. The PS16 had more broken and abnormal eggs (P = 0.01) and lower hatchability (P = 0.04) than other treatments. In conclusion, photostimulation at 16 and 22 wk of age decreases hatchability and egg production, respectively, and photostimulation at 18 wk is appreciated for the WL breeder hens.

Effect of different feed restriction programs on the performance and reproductive traits of broiler breeders

The current experiment evaluated the effect of different feed restriction programs applied during rearing on the performance and reproductive traits of broiler breeder pullets reared on floor pens, isolating the birds' weight effect from the analysis. At 4 wk of age, 1,400 breeder pullets were distributed in a completely randomized design with 4 treatments: daily restriction (DAILY-every day feeding), skip-a-day restriction (SKIP-every other day feeding), 4/3 restriction (4/3-4 days feeding and 3 nonconsecutive fasting days) and 5/2 restriction (5/2-5 days feeding and 2 nonconsecutive fasting days), and 8 replicates. At 11, 18, 25, 32, and 39 wk of age, body weight, feed intake, feed conversion ratio, carcass composition, organs relative weight (liver, fat, oviduct, and ovary stroma), egg production, and egg weight were accessed. At 32 and 39 wk, 12 eggs by experimental unit were collected and incubated to determine hatchability and fertility parameters. Body weight, carcass EE, and FCR were higher for SKIP birds when compared to other feed restriction programs. SKIP birds also showed the lowest number of eggs per bird (NEB) and % of egg production when compared to 4/3 feeding schedule, which provided higher values. Feed conversion ratio per egg mass (FCEM) was also higher in 4/3 schedule in relation to SKIP birds. In regard to incubation parameters, 5/2 treatment showed higher values for hatchability (HAT) and fertility (FERT), similar to results of 4/3 and DAILY treatments, while SKIP birds showed the lowest. In conclusion, 4/3 and 5/2 feeding programs showed best results and should be used by broiler breeder producers to control pullets' body weight. Therefore, the higher number of eggs produced with less feed and statistically not different fertility and hatchability between programs obtained in this study suggest the 4/3 program could be more efficient than 5/2 program. Body weight'|'s effect isolation was important to analyze the effect of feed restriction program per se, and should be applied in future approaches.

Energy partitioning by broiler breeder pullets in skip-a-day and precision feeding systems

An empirical nonlinear mixed model was derived to describe metabolizable energy (ME) partitioning in Ross 308 broiler breeder pullets. Its coefficients described ME used for total heat production (HP) and growth. A total of 630 pullets were randomly and equally assigned to 2 treatments: precision feeding (PF) and conventional skip-a-day feeding (CON) from 10 to 23 wk of age. The PF system allowed birds to enter voluntarily at any time, weighed them, and provided access to feed for 60 s if their BW was less than the target BW. Birds in the CON treatment were fed as a group on alternate days. Energetic efficiency of pullets was evaluated using residual total heat production (RHP), defined as the difference between observed and predicted total HP. Additionally, ME intake (MEI), ADG, HP, and cumulative feed conversion ratio (FCR) were calculated for the entire experimental period. The energy partitioning model (P < 0.05) predicted MEI = (120+u)BW0.68 + 1.52(ADG) + ε. Total HP was (120 kcal/kg0.68 + u); the energy requirement for each g of BW gain was 1.52 kcal/d. The random variable u ∼ N (0, σu2) indicated a pen level HP standard deviation σu = 12.1 kcal/kg0.68. Over the experimental period, for CON and PF treatments, respectively, MEI was 194 and 174 kcal/d (P < 0.001); ADG was 15.3 and 15.4 g/d (P = 0.94); HP was 129 and 111 kcal/kg0.68 (P < 0.001); FCR was 4.888 and 4.057 (P < 0.001); and RHP was 0.12 and -0.12 kcal/kg0.68 (P = 0.73). The CON pullets had similar ADG, but higher MEI relative to PF, consistent with levels of heat production predicted by RHP. The PF pullets had lower cumulative FCR compared to CON pullets. The PF pullets lost less energy as heat, likely because they were fed continuously, reducing the need to store and mobilize nutrients compared to CON pullets. Thus, increased feeding frequency likely increased PF pullet efficiency.

Impact of Skip-a-Day and Every-Day Feeding Programs for Broiler Breeder Pullets on the Recovery of Salmonella and Campylobacter following challenge

The impact of restrictive feeding programs on Salmonella and Campylobacter colonization and persistence after challenge was investigated for broiler breeder pullets housed in an experimental rearing facility. Pullet-chicks were placed on litter in 3 feeding program rooms and each room contained 2 replicate pens. The feeding programs were: (1) Skip-a-day in trough feeders (SAD); (2) Every-day in trough feeders (EDT); (3) Every-day on the pen litter (EDL). On d 1, an additional group of hatchmate chicks were housed in a separate room and gavaged with Salmonella Typhimurium, to later serve as seeder chicks. After seeders were confirmed Salmonella-positive at wk 4, at wk 5 seeders were placed into each feeding program pen to commingle with 135 penmates. At 7, 9, 11, 17, 18, and 20 wk the litter surface in each pen was sampled using intermittently stepped-on drag-swabs. At 8, 12, 16, and 20 wk of age the ceca were sampled from 10 penmates/pen and 2 pooled spleen samples/pen were collected. SAD litter remained Salmonella-positive through 20 wk of age while EDL and EDT pens had no detectible litter Salmonella recovery by 18 and 20 wk. EDL fed pens had no direct (<102 cfu/mL) litter Salmonella recovery during the entirety of the experiment. Salmonella prevalence for ceca from SAD pullets was significantly (P < 0.05) higher at 8 wk (70%) compared to EDT (40%) and EDL (30%). At wk 12, SAD pullets for both on and off-feed sampling days had significantly higher Salmonella recovery (40%), compared to EDT and EDL (both at 5% recovery). By 16 and 20 wk, only the SAD pullets on the on-feed day (48 h without feed) had recovery of Salmonella at 20%. Salmonella recovery in pooled spleen samples did not appear associated with feeding treatments (22% positive). The remaining pullets challenged with Campylobacter at 21 wk produced similar trends as was seen for Salmonella. SAD program pullets had significantly higher Campylobacter from ceca (80 to 100%) compared to pullets on EDL (30 to 60%) or EDT (40 to 95%). These results suggest that using a Skip-a-Day feeding program for broiler breeder pullets contributes to persistently higher Salmonella and Campylobacter ceca colonization and litter prevalence.

The Quest for Welfare-Friendly Feeding of Broiler Breeders: Effects of Daily vs. 5:2 Feed Restriction Schedules

Restricted feeding of broiler breeders is required for improved long-term health and welfare. Because feeding frustration and hunger are major welfare concerns during rearing, many suggestions have been made to decrease the negative feelings of hunger while maintaining suitable growth rates and reproductive health. Non-daily ("skip-a-day") feeding schedules are commonly used around the world to increase portion sizes at meal times while restricting intake but these practices are prohibited in many countries due to welfare concerns on fasting days. We compared birds raised on a non-daily feeding schedule (2 non-consecutive fasting days per week, 5:2), previously suggested as a welfare-friendlier non-daily alternative, to birds raised on daily feed restriction. We found signs of increased physiological stress levels in 5:2 birds, including elevated heterophil to lymphocyte ratios (1.00 for 5:2 vs. 0.75 for daily fed at 12 weeks of age), increased adiposity (0.21% lean body weight [LBW] for 5:2 vs. 0.13% LBW for daily fed), and reduced muscle growth (pectoral muscle 5.94% LBW for 5:2 vs. 6.52% LBW for daily fed). At the same time, 5:2 birds showed signs of lower anxiety before feeding times (activity was reduced from 10.30 in daily fed to 4.85) which may be a result of the lower feed competition associated with larger portion sizes. Although we found no difference in latency to first head movement in tonic immobility between the treatments (136.5 s on average for both groups), 5:2 birds generally showed more interest in a novel object in the home pen which indicated increased risk taking and reduced fear while fasting. The 5:2 birds in this study showed no signs of learning the feeding schedule, and this unpredictability may also increase stress. Taken together, the effects of 5:2 vs. daily feed restriction on the welfare of broiler breeder pullets remain inconclusive and differ between feeding and fasting days. In addition to reducing stress by minimizing the number of fasting days, we suggest that a shift to more predictable schedules may help improve the welfare of broiler breeder pullets.

Growth curve and diet density affect eating motivation, behavior, and body composition of broiler breeders during rearing

The aim of this work has been to assess the effect of diet density [control (CON) or 15% diluted (DIL)] and growth curve [recommended by the genetic line (RBW) or 15% heavier (HBW)] and their interaction on BW uniformity, feeding motivation, behavior, and body composition of broiler breeder pullets. A total of 3,000 one-day-old female breeders Ross 308, distributed in 20 pens, was randomly assigned to each treatment. Feed allowance was weekly adjusted to reach the desired BW. Feed was provided as pelleted (zero to 3 wk) and crumble (4 to 19 wk). Time eating was measured at 7, 11, and 19 weeks. A feeding rate test was performed after 11 weeks. Behavior was observed at 9 and 15 wk, by visual scan. At 6, 13, and 19 wk of age, one bird/pen was slaughtered for weighing different organs and analyzing the composition of empty whole bodies. Treatments did not affect BW uniformity; relative weights of the ovary, oviduct, or gizzard; or protein content of empty BW. Time eating varied with the growth curve at 19 wk (P < 0.05), HBW pullets spent 19 more min eating than RBW pullets. DIL led to 4 and 8 more min eating at 19 wk for pullets of RBW and HBW (P < 0.05), respectively. Pullets fed DIL consumed 30% (P < 0.05) less during the feeding rate test when kept on a restricted regimen, and they had lower compensatory energy intake after ad libitum feeding than those fed CON, indicating lower feeding motivation. Behavior was affected by the age and by the time of the d measured, but it did not change with the treatments. Birds spent most time pecking objects (50%), feeding (28%), and drinking (17%). Pullets fed DIL had 8% lower breast yield at different ages and higher empty digestive tracts at 6 weeks. Body composition varied with age; fat content increased from 12.7 to 15.9 to 19.8% for 6, 13, and 19 wk, respectively. The lowest body fat was observed for RBW pullets fed DIL (P = 0.003) at 19 weeks. Feeding DIL diets to HBW pullets could be done to increase the time spent eating and reduce their feeling of hunger without negative effects on body composition. However, its influence on behavior and BW uniformity was not proved.

Measuring motivation for appetitive behaviour: food-restricted broiler breeder chickens cross a water barrier to forage in an area of wood shavings without food

Broiler breeders (parents of meat chickens) are selected for fast growth and become obese if fed ad libitum. To avoid this and maintain good health and reproductive ability, they are feed restricted to about 1/3 of what they would eat ad libitum. As a result, they experience chronic hunger and exhibit abnormal behaviour patterns that may indicate stress and frustration. One approach to measuring hunger is to observe how much birds will work, such as pecking a key, for access to more or different types of food. However, the sight, smell, and feedback from consumption of the feed reward changes the context and may artificially raise feeding motivation. To avoid this, we tested broiler breeders in an apparatus in which they could work for access to a wooden platform covered in wood shavings by crossing a water runway which increased in length and depth in 8 successive tests. In the wood shavings area, they could perform exploratory and foraging behaviour (the appetitive phase of feeding) but were never rewarded with feed. Sixty birds were divided into three feed quantity treatments: commercial restriction (R), and twice (2R) or three times (3R) this amount. Overall, birds fed R worked harder to reach the wood shavings area (reached it in a larger number of tests) than 2R and 3R birds (P<0.001). More restricted birds took less time to reach the area (P<0.001, R<2R<3R) and spent more time foraging while there (P<0.001, R>2R>3R). This indicates that restricted-fed birds were hungry and willing to work for the opportunity to forage even though food was never provided, suggesting that their motivation to perform the appetitive component of feeding behaviour (foraging/food searching) was sufficient to sustain their response. Thus food restriction in broiler breeders is a welfare concern. However these methods could be used to test alternative feeding regimes to attempt to find ways of alleviating hunger while still maintaining healthy growth and reproduction in these birds.

Effect of crossbreeding on fertility, hatchability and embryonic mortality of Nigerian local chickens

A total of 970 eggs were collected from matings involving three genotypes of Nigerian local chickens (Normal-feathered, Frizzle-feathered and Naked neck) and one exotic broiler breeder strain (Anak Titan) to evaluate the effect of crossbreeding on fertility, hatchability and embryonic mortality. Mating was achieved through artificial insemination. Sire genotype significantly (P < 0.05) affected percent fertility and percent dead-in-shell. Naked neck sire genotype had the highest dead-in-shell (19.5%) with the least being 7.5% for Frizzle-feathered chickens. Frizzle-feathered sire genotype had the highest fertility (90.5%) and hatchability (91.4%). Dam genotype had a significant effect (P < 0.01) on fertility and hatchability, with Anak Titan dam having the highest fertility and hatchability of 88.2% and 94.6%, respectively. Fertility and hatchability were significantly (P < 0.05) influenced by the interactive effect of sire and dam genotypes with Frizzle-feathered × Anak Titan having 98.5% fertility and 96.8% hatchability. Both straight and reciprocal crosses involving Frizzle-feathered genotype and Anak Titan resulted in higher mean values for fertility and hatchability when compared to crosses involving the other two local chicken genotypes. This result suggests that the use of the Frizzle-feathered genotype appears to be more desirable in fertility and hatchability trials.

A twice-a-day feeding regimen optimizes performance in broiler breeder hens

To evaluate the effects of different methods of feed allocation on performance, plasma hormone concentration, and ovarian morphology, an experiment was conducted using 32 Cobb 500 broiler breeder hens. The experiment was started at 27 wk and lasted to 39 wk of age. Feeding regimens included: i) hens with an ad libitum feeding program, ii) hens that received their restricted feed once a day, iii) hens that received their restricted feed twice a day, and iv) hens that received their restricted feed 3 times a day. Each hen was assumed as an experimental unit and treatments were replicated 8 times. Daily egg production, BW, and egg and yolk weights were measured. Two blood samples were taken 3 and 6 h after the first feed allocation every 2 wk. Plasma samples were assayed for glucose, triacylglycerol (TAG), cholesterol, as well as leptin-like concentration, glucagon, triiodothyronine, thyroxine, progesterone, estradiol, and testosterone. Liver, abdominal fat pad, and ovary were collected at necropsy. Ovaries were weighed and follicles were characterized as large yellow follicles, small yellow follicles, and large white follicles. Results showed inferior egg production in ad libitum-fed birds along with high levels of plasma glucose, TAG, cholesterol, leptin-like concentration, and testosterone. Twice-a-day-fed birds produced more egg in the entire production period than once-a-day-fed birds. Better performance of twice-a-day-fed hens was associated with lower plasma glucose, TAG, and leptin-like concentration, whereas their estradiol and glucagon were higher than once-a-day-fed hens. Results obtained in our study suggest that allocation of restricted feed 2 times a day may alleviate or delay lipotoxicity development and improve reproductive performance in broiler breeder hens.

Reproductive Efficiency and Metabolism of Female Broiler Breeders as Affected by Genotype, Feed Allocation, and Age at Photostimulation. 1. Pullet Growth and Development

A 3 x 4 x 2 factorial design was carried out to determine the effect of 3 broiler breeder strains, 4 target BW profiles, and 2 photostimulation ages on pullet growth and development. A total of 560 pullets from each strain (Hubbard Hi-Y, Ross 508, and Ross 708) were reared on BW profiles that separated at 4 wk and converged at 32 wk of age as follows: standard (mean target BW profile of the 3 strains used), low (12-wk BW target = 25% lower than standard followed by rapid gain to 32 wk), moderate (12-wk BW target = 150% of standard followed by lower rate of gain to 32 wk), and high (12-wk BW target = 200% of standard followed by minimal growth to 32 wk). Birds were photostimulated at 18 (18WK) or 22 wk (22WK). During the prephotostimulation phase (2 to 18 wk of age), 4 birds were killed for each of the 12 interactions at 14-d intervals to characterize changes in carcass traits. After 18 wk (wk 20, 22, and 24), 4 birds from each of the 24 interactions were killed and dissected (n = 768). Growth rate restricted frame size (e.g., 18-wk shank length: low = 101.8; standard = 105.6; moderate = 109.5; and high = 112.3 mm). At 24 wk of age, the 22WK birds had similar amounts of breast muscle compared with 18WK birds, whereas the later photostimulated hens had heavier abdominal fat pads. Early photo-stimulation resulted in increased 24-wk liver weights in all strains, but the difference was greatest in Ross 708 birds. The 22-wk ovary weight was influenced by age at photostimulation in high (18WK = 17.3; 22WK = 1.6 g) and moderate (18WK = 14.1; 22WK = 1.1 g) birds. The more extensive feed restriction of LOW birds before 12 wk of age appeared to limit breast muscle and fat pad growth and slow reproductive tract development following photostimulation. Pullets on heavier BW profiles respond to early PS by developing the reproductive system at the expense of breast muscle and fat pad growth. Genetic strain modulates some of the effect of very different target BW profiles.

Reproductive Efficiency and Metabolism of Female Broiler Breeders as Affected by Genotype, Feed Allocation, and Age at Photostimulation. 2. Sexual Maturation

A 3 x 4 x 2 factorial design trial was conducted to determine the effect of 3 broiler breeder strains, 4 target BW profiles, and 2 photostimulation ages on sexual maturation traits. A total of 560 pullets from each strain (Hubbard Hi-Y, Ross 508, and Ross 708) were housed in 24 pens. The BW profiles diverged at 4 wk and subsequently converged at 32 wk of age as follows: standard (approximate mean target BW profile of the 3 strains), low (12-wk BW target = 25% lower than standard followed by rapid gain to 32 wk), moderate (12-wk BW target = 150% of standard followed by lower rate of gain to 32 wk), and high (12-wk BW target = 200% of standard followed by minimal growth to 32 wk). Birds were photostimulated at 18 (18WK) or 22 (22WK) wk. Eight birds per interaction (n = 192) were killed and dissected at sexual maturity (first oviposition). Body weight profile affected timing of sexual maturity with the 18WK but not the 22WK treatment. There was no effect of BW profile on initial egg weight. Mean BW at sexual maturity was 3.40, 3.21, 3.01, and 2.84 kg for high, moderate, standard, and low birds, respectively. This affected shank and keel length, indicating differences in frame size. Ovary weight at sexual maturity was 6 g heavier in the low treatment (55 g) compared with other BW profiles. This was related to recent feeding level, which was highest at sexual maturity in the low treatment. Arrangement of ovarian large yellow follicles (LYF) changed with photostimulation age. Birds that were photostimulated at 18WK had 1.33 LYF hierarchies, compared with 1.22 in 22WK birds. The 18WK-high birds had increased excess LYF production (55% paired) compared with other BW profiles, whereas both small yellow follicle number and atresia were increased. Feeding profiles affected growth and conformational traits, with little effect on reproductive morphology at sexual maturity.

The effects of feed restriction on plasma biochemistry in growing meat type chickens (Gallus gallus)

The effect of feed restriction on plasma hormones (triiodothyronine - T(3), thyroxine - T(4), and corticosterone), protein, lipid, carbohydrate, and mineral metabolism and activity of plasma enzymes (creatine kinase, alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase) were studied in meat type female chickens (Gallus gallus). Ad libitum fed birds were compared with those subjected to severe and moderate quantitative feed restriction from 16 to 100 days of age. Feed restriction elevated plasma T(4) and corticosterone levels and reduced T(3). A feed restriction-induced decrease was observed for plasma protein and albumin concentrations, but not for uric acid and creatinine. Total plasma lipids, triacylglycerols, cholesterol, high density lipids, and calcium were lower for the feed restricted chickens, in particular during the latter phase of the experiment. Concentrations of glucose and phosphorus were not altered by feeding treatment. Activity of alkaline phosphatase was significantly increased in restricted chicks from day 58. Significant changes of plasma biochemical parameters induced by severe and moderate quantitative feed restriction illustrate that limiting feed intake poses an intensive stress on meat type chickens during the rapid growth period. However, activities of creatine kinase, aspartate aminotransferase, and alanine aminotransferase were significantly higher in ad libitum fed chickens during this period. This elevation in enzymatic activity may be in response to tissue damage, indicating potential health and welfare problems also in ad libitum fed meat type chickens, resulting from selection for intensive growth.