In pursuit of a better broiler: walking ability and incidence of contact dermatitis in conventional and slower growing strains of broiler chickens

Light intensity preferences of broiler chickens is affected by breed, age, time of day and behaviour

Light is an important aspect of broiler husbandry and management as it influences behaviour and welfare. However, a lot remains unknown regarding broiler preferences for light intensities, especially for slower-growing broilers which are increasingly used in broiler production systems in the EU. We identified preferences of fast (F)- and slower (S)-growing broilers for intensities in relation to behaviour, age and time of day. Broilers were housed in pens with four sections, each having one intensity (0.2, 20, 50 or 1000 lx). Both breeds showed more active behaviours at higher intensities and more inactive behaviours at lower intensities. They preferred higher intensities when young and lower intensities when older, with S broilers preferring the lowest intensity more when older. They preferred higher intensities at the end and start of the light period, with F broilers preferring the highest intensity more when young and S broilers more when older. Thus, light intensity could be used to create functional zones within a broiler house for specific behaviours and light intensity programs could be adapted to age and time of day, taking into account breed differences. Furthermore, broilers were always present at each intensity, suggesting individual preferences and offering a choice might be beneficial for broiler welfare.

Effects of Standardized Natural Citrus Extract on Growth, Gut Health, Carcass Quality, and Welfare of Broiler Chickens

This study aimed to investigate the effects of a Standardized Natural Citrus Extract (SNCE) on broiler chickens' growth performance, gut health, carcass quality, and welfare. A total of 756 one-day-old Ross 308 males were randomly assigned to two groups: a control group (CTL) fed with a standard diet, and a citrus group (SNCE) fed with the same standard diet supplemented with 250 g/ton of feed of SNCE. Growth performance was recorded weekly until d 35, while mortality was recorded daily. The feed conversion ratio (FCR) and European Efficiency Index (EEI) of broiler chickens were also calculated weekly. At day 35, 10 birds per group were randomly selected for slaughter performance. In parallel, broiler chickens' welfare was assessed according to the Welfare Quality Assessment Protocol. Caecal digest was also collected post mortem for short-chain fatty acids (SCFA) analyses, and jejunum samples were collected for ex vivo gut permeability assay. SNCE dietary supplementation enhanced broiler chickens' performance, i.e., final bodyweight and EEI, compared to the CTL group. The carcass weight was also significantly higher in the SNCE group. In addition, the fat percentage was lower in the SNCE group. Regarding broiler chickens' welfare and gut health parameters, Footpad Dermatitis (FPD) and gate score were also lower in birds supplemented with SNCE. The SCFA measurement showed a lower concentration of iso-butyric acid, iso-valeric acid, and total putrefactive SCFA in the SNCE group. The differences in gut permeability measured as TEER value indicate that using citrus extract lowered the risk of gut inflammation. This study provides valuable insights into the mechanisms of action that may underlie the observed effects of SNCE on performance, as demonstrated in this study and others. These effects could potentially be attributed to the reduction in inflammation and the enhanced utilization of nutrients. Further studies are needed to confirm these results.

Impact of Growth Rate on the Welfare of Broilers

Selection for the more efficient production of broilers has resulted in rapid growth rates. The aim was to review the existing knowledge on the effect of growth rate on broiler welfare. Genotypes with faster growth rates consistently demonstrate poorer gait scores and increased prevalence of disorders affecting their legs than slower-growing genotypes. Reduced mobility places faster-growing broilers at an increased risk of developing contact dermatitis, as they spend increased durations sitting in contact with litter. Poor walking ability, heavy body weights, and conformational differences such as proportionally larger breast muscle in genotypes with faster growth can impact a bird's ability to walk and navigate the environment, making it difficult to access resources and express natural behaviors. Faster growth has also been associated with poor cardiovascular health, increased susceptibility to heat stress, increased prevalence of mortality, ascites, as well as multiple breast muscle myopathies. Feed restriction, a practice associated with hunger and frustration, may be used to control the growth of broiler breeders, with birds having higher growth potential typically experiencing higher restriction levels. Overall, there is strong evidence that fast growth rates negatively impact welfare, and that slower-growing genotypes show significantly improved welfare. Furthermore, some evidence suggests that even minor reductions in growth rate can lead to welfare improvements.

Overview of the various methods used to assess walking ability in broiler chickens

BACKGROUND

Walking ability is a highly important animal-based indicator of welfare in broilers that warrants monitoring across commercial production.

METHODS

A review of the technical and scientific literature on existing methods for assessing walking ability in broilers was conducted, and the reliability, validity and feasibility of the different methods were assessed when relevant information was available.

RESULTS

Visual gait scoring has high validity, minimal equipment needs and is relatively quick to perform; however, this method is subjective and requires extensive training. Due to this, more objective tests, such as the latency to lie test, have been developed, although more validation of these tests is required. Other identified methods, such as obstacle courses, the rotarod test and kinetic and kinematic approaches, require considerable amounts of equipment, making them impractical for use during on-farm inspections. Automated methods that rely on movement or activity data have potential for future development but currently lack the resolution of traditional gait scoring and require equipment such as cameras or accelerometers.

CONCLUSIONS

Objective, seemingly valid, repeatable and feasible options exist for the assessment of walking ability that would facilitate the monitoring of commercial broiler welfare; however, more validation of these methods is required, especially in commercial farm settings.

Leg disorders in broiler chickens: a review of current knowledge

Ensuring improved leg health is an important prerequisite for broilers to achieve optimal production performance and welfare status. Broiler leg disease is characterized by leg muscle weakness, leg bone deformation, joint cysts, arthritis, femoral head necrosis, and other symptoms that result in lameness or paralysis. These conditions significantly affect movement, feeding and broiler growth performance. Nowadays, the high incidence of leg abnormalities in broiler chickens has become an important issue that hampers the development of broiler farming. Therefore, it is imperative to prevent leg diseases and improve the health of broiler legs. This review mainly discusses the current prevalence of broiler leg diseases and describes the risk factors, diagnosis, and prevention of leg diseases to provide a scientific basis for addressing broiler leg health problems.

Growth Rate Distribution and Potential Non-Linear Relationship between Body Weight and Walking Ability in Turkeys

The aim of this study was to investigate the potential non-linear relationship between growth and walking ability (WA). The phenotypic data included body weights at 12 and 20 weeks and WA at 20 weeks of age measured on 276,059 male turkeys. The growth rate at three age periods (0 to 12, 12 to 20 and 0 to 20 weeks) was calculated. Each bird was assigned to one of the quartiles of the growth rate distribution for each age period. Between the first and fourth quartiles, the incidence of score 1 (bad WA) increased by 31, 18, and 33% for the first, second, and third age periods, respectively. For good WA (scores 4, 5, and 6), the incidence decreased by 55, 66, and 72% between the first and fourth quartiles for the first, second, and third age periods, respectively. Estimates of heritability of WA ranged between 0.18 and 0.26. The genetic correlations between adjacent growth rate quartiles were high and decayed as the interval between quartiles increased. The magnitude of the variation in the incidence of walking scores and genetic correlations across the growth rate quartiles point towards a non-linear relationship between growth and mobility suggesting other factors may affect walking ability.

Fast growing broiler production from genetically different pure lines in Turkey. 2. Broiler traits: growth, feed intake, feed efficiency, livability, body defects and some heterotic effects

The aim of the this study was to reveal the trends in body weight (BW), feed intake (FI), feed conversion ratio (FCR), livability, and body defects (foot pad dermatitis (FPD), hock burn (HB), and breast burn (BB)) in offspring of ANADOLU-T pure lines (PLs), their 12 four-way hybrids and ROSS-308 hybrid, and the observed heterosis values for some performance and body defect traits. A total of 2736 (1368 broilers each) broiler chickens from ANADOLU-T pure lines, their hybrids, and commercial ROSS-308 hybrid were hatched from breeder eggs at 32 and 52 weeks of age and reared for 42 days in 2 experiments. The PL eggs were generally heavier than hybrid eggs (P < 0.001) and day-old BWs (P < 0.001) were also higher in PL chicks (ranging between 44.5 and 45.8 g). The males of ROSS-308 hybrid were heavier than others at 42 d of age (P = 0.035), and the lowest BW values were determined for A1, A2, and A3 line chickens (P < 0.001). ROSS-308 (4453.8 g) showed similar 42-d FI with all of four-way ANADOLU-T hybrids except (B1 × B2) × (A1 × A2) and (B1 × B2) × (A3 × A1). The 42-d FCR was 1.473 for the ROSS-308, while it ranged between 1.654 and 1.715 for the four-way ANADOLU-T hybrids (P < 0.001). The 42-d livability of four-way ANADOLU-T hybrids and ROSS-308 ranged between 92.0 and 100.0%. All ANADOLU-T hybrids, except two, showed higher 42-d livability than ROSS-308. While both genotype and sex were important for HB and BB, only the genotype effect was significant for FPD (P < 0.001). All ANADOLU-T hybrids showed low to moderate and positive heterosis for BW after 28 d. From 14 to 42 d, the magnitudes of heterosis for FCR decreased. Heterosis for livability from 7 to 42 d were not significant between genotypes. Percentages of heterosis for resistance to FPD (- 1.56 to 1.44%), HB (- 37.03 to 18.75%), and BB (- 12.70 to 1.02%) defects were not significant among genotypes. It was concluded that mating of B1 × B2 males with A1 × A2 and A3 × A2 females seems more favorable in terms of higher chick and meat production. However, the fact that the overall performance of ANADOLU-T hybrids is lower than ROSS-308 clearly indicates that genetic selection must be maintained for enhanced body weight and feed efficiency.

Age and sex related changes in fattening performance, dermatitis, intestinal histomorphology, and serum IgG level of slow- and fast-growing broilers under the intensive system

Due to consumers' concerns about broiler welfare, slow-growing broilers (SGB) have also been used in production. Fast-growing broilers (FGB) reach slaughter weight earlier the slow growing. This study was aimed to determine the sex-related changes in fattening performance, dermatitis, intestinal histomorphology, and serum IgG level of SGB and FGB under the intensive system during the 10 weeks. A total of 336 one-day-old broilers were distributed into four equal groups (FGB-female, FGB-male, SGB-female, and SGB-male) consisting of a 2 × 2 factorial design. The main factors were genotype (FGB and SGB) and sex (female and male). Each treatment had 6 duplicates consisting of 14 broilers. They were placed on the litter pens. The experiment lasted 10 weeks. The body weight, body weight gain, feed consumption, and feed-to-gain ratio were determined weekly during the experiment. One broiler close to the average body weight from each pen (6 broilers in the group) has been slaughtered each week and intestinal histomorphology was determined. Additionally, IgG levels in the blood and dermatitis were determined. While the period in which the body weight gain was the highest in the FGB was up to 6 week of age, this period lasted until the 7 week of age in the SGB (P < 0.001). It has been determined that FGB have the best feed efficiency ability during both 6 weeks of fattening period and 10 weeks of fattening period (P < 0.001). The difference between the sex in terms of the feed efficiency appeared after the age of 4 weeks and this difference continued until the age of 9 weeks (P < 0.01). It was determined that villus height, crypt depth, and the ratio of villus height to crypt depth in the jejunum region were higher in FGB from the age of 1 week than in SGB (P < 0.05). It was observed that the incidence of dermatitis increased in the FGB (P < 0.001). It has been determined that the genotype (P < 0.01) and period (P < 0.001) were effective according to the IgG level. These results indicate that 7 and 8 weeks can be considered important periods in terms of economic efficiency in SGB and FGB reared for 10 weeks under the same management systems and it was observed that both genotypes would be more susceptible to diseases at the age of 6 weeks.

In pursuit of a better broiler: tibial morphology, breaking strength, and ash content in conventional and slower-growing strains of broiler chickens

This study was conducted to determine the differences in bone traits in 14 strains of broiler chickens differing in growth rate. The strains encompassed 2 conventional (CONV; ADG_0-48 >60 g/d) and 12 slower-growing (SG) strains classified as FAST (ADG_0-62 = 53-55 g/d), MOD (ADG_0-62 = 50-51 g/d), and SLOW (ADG_0-62 <50 g/d), with 4 strains represented in each SG category. A total of 7,216 mixed-sex birds were equally allocated into 164 pens (44 birds/pen; 30 kg/m²) in a randomized incomplete block design, with each strain represented in 8 to 12 pens over 2-3 trials. From each pen, 4 birds (2 males and 2 females) were individually weighed and euthanized at 2 target weights (TWs) according to their time to reach approximately 2.1 kg (TW1: 34 d for CONV and 48 d for SG strains) and 3.2 kg (TW2: 48 d for CONV and 62 d for SG strains). Tibiae samples were dissected, and length and diameter were recorded. Left tibiae were used for tibial breaking strength (TBS) at both TWs and tibial ash at TW2. At TW1, CONV birds' tibiae were narrowest and shortest (P < 0.001), yet had similar TBS compared to the other categories (P > 0.69). At TW2, category (P > 0.50) had no effect on tibial diameter, yet CONV birds had the shortest tibiae (P < 0.001). The CONV birds had greater TBS:BW ratio than FAST and MOD birds at both TWs 1 and 2 (P < 0.039) and similar ash content as the other categories at TW2 (P > 0.220). At 48 d of age, CONV birds had the greatest absolute TBS (P < 0.003), yet lower TBS:BW ratio than SLOW birds (P < 0.001). Tibiae from CONV birds were longer than MOD and SLOW birds, and thicker in diameter than the other categories, yet CONV birds had the lowest dimensions relative to BW (P < 0.001) at 48 d, indicating a negative association between accelerated growth and tibial dimensions. These results indicate that differences in functional abilities among categories may be due to differences in morphometric traits rather than differences in bone strength and mineralization.