Kokou Tona

THE DAY-OLD CHICK: A CRUCIAL HINGE BETWEEN BREEDERS AND BROILERS

The quality of the day-old broiler chick is foremost in the minds of many poultry managers. From fertilised ovum to the placement at the broiler farm, some factors such as the characteristics of the incubating eggs, the egg holding conditions, the incubation conditions and the conditions that exist between hatching and placement at the farm and their interactions may affect chick quality. It may be questioned if maximal hatchability is the best indicator for chick quality and/or post-hatching viability, even if optimal hatchability is considered a prerequisite for successful incubation. The environmental conditions during incubation (e.g. the temperature, humidity and ventilation rate (carbon dioxide concentration)) are not set independently from each other, although each may have its own optimum for hatchability and chick quality. These optima for each incubation factor may alter differentially according to the characteristics of the incubating egg. It is concluded that more independent control as well as more control of the variability of the classical physical conditions in the incubator are required in order to improve hatchability and chick quality.

Effects of ad libitum feeding on performance of different strains of broiler breeders

Tolerance to ad libitum feeding was compared in three genotypes of broiler breeder hens: a standard broiler breeder fed ad libitum (SA) or restricted (SR), a slow growing ‘label’ broiler breeder (L) and an experimental dwarf heavy broiler breeder (E). Two similar experiments were conducted in two distinct research centres. Feed intake and body weight were measured every 3 weeks from hatch to 40 to 49 weeks of age. Egg production and egg abnormalities were recorded. The number of yellow follicles in ovaries was counted at the age of 32 weeks. Body weight was stabilised at 2·2, 3·7 and 5·4 kg after 24 weeks of age in L, E and SA hens, respectively. Growth of the SR hens was similar to that of L up to 20 weeks and stabilised at a similar level to that of E hens after 30 weeks of age. Sexual maturity was delayed by 6 weeks in restricted breeders compared to ad libitum fed hens that started to lay at 20 weeks. SA hens had low egg production and a high proportion of defective eggs, which was largely compensated for by feed restriction. However, productivity of SR hens remained lower than that of L breeders. Compared to the low viability and reproductive fitness observed with SA hens, the E dwarf broiler breeder tolerated ad libitum feeding and had better egg production, fewer egg abnormalities and yellow follicles per ovary and a higher egg production. However, laying rate was still lower than that of the SR and L groups. Energy conversion (kJ/g egg) from 32 to 40 weeks of age was much higher in the SA group than in the other three groups. The feasibility of feeding a dwarf broiler breeder ad libitum calls for further research on implications of specific IGF and GH-receptor expression at the level of the ovary in dw chickens.

Detection of early embryonic development in chicken eggs using visible light transmission.

1. In two separate experiments, the possibility of detecting embryonic development in chicken eggs was assessed using the same spectrophotometric method used to detect blood in Table eggs, using a combination of two wavelengths (577 and 610 nm) of the transmission spectrum. 2. In the first experiment, during the first 10 d of incubation, transmission spectra of 30 Hisex White® eggs and 30 Hybro® eggs were measured daily. 3. In the second experiment, 292 Hisex White eggs were incubated. Seven groups were randomly assigned. Six received an injection of sodium azide (NaN 3 ) at different times during incubation in order to stop embryonic development, and during the first 12 d of incubation the transmission spectrum was measured daily. The acoustic resonance analysis method was also used on a group of uninjected eggs. 4. In the first experiment, it was possible to detect embryonic development from 120 h of incubation onwards in fertile eggs. In the second experiment changes in light transmission due to embryonic development were detected from 108 h of incubation. Detection of embryonic development using the acoustic resonance analysis method in the second experiment was possible only from 120 h of incubation. 5. It was concluded that the detection of embryonic development using visible light transmission is not directly linked with the formation of blood, but with the formation of sub-embryonic fluid, which takes place from 72 h of incubation onwards. This fluid makes the yolk sac translucent so that absorption of light at 577 nm can be detected.

Broiler breeder paradox: a project report

A first product of this European project was a tool for scoring chick quality. A link was established between chick quality and embryonic physiological parameters such as heat production. Eggs from broiler breeders that give rise to rapidly growing broilers have a different embryonic development that may need modified incubation conditions. Within genotypes, better chick quality induces better liveability and faster growth in broiler production. Extensive data on broiler breeder production were generated. Feed restriction was necessary to maintain welfare and reproduction at acceptable levels in standard broiler breeders. The dw-experimental genotype (E) was more tolerant to ad libitum feeding. If an alternative to feed restriction had to be found, the use of a dw genotype with less severe feed restriction could be adopted. Fibre per se, or partial feed restriction during the growing period, only compensated to a small extent for the negative effects of early fast growth on later reproduction. The results of the project on behaviour did not support welfare concerns on feed restriction. They confirmed the hypothesis that environmental pecking is a displacement activity rather than a sign of frustration. Factors other than central control by pituitary hormones seem to be involved in the modulation of the laying rate. The local (intra-ovarian) role of growth factors such as Insulin-like Growth Factors (IGFs), Bone Morphogenetic Proteins (BMPs) and leptin are known to modulate the effect of gonadotrophins on ovarian function. For both BMPs and IGFs, feed restriction enhanced the interaction between growth factors and gonadotrophins as well as the proliferation of granulosa cells in vitro. Future genetic selection of broiler breeder production might aim at uncoupling the control of growth factors in the ovary from the selection for rapid growth to maintain or increase the growth rate of chicks without further penalising the already poor reproductive performance of broiler breeders. Putative quantitative trait loci for ovulation rate were identified in the project and may eventually facilitate selection by breeding companies for birds that could be fed enough feed to optimise their welfare.

Embryonic exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin in chickens: effects of dose and embryonic stage on hatchability and growth

Chicken embryos (Gallus domesticus) were injected with 0, 8, 20 or 50 ng tetrachlorodibenzo-p-dioxin (TCDD) per egg at embryonic day (ED) 4, 8 or 12 to investigate the effects of differential periods of sensitivity to TCDD exposure. At hatch, all chicks were weighed, sexed and examined macroscopically to identify possible malformations. Liver, bursa, heart and spleen masses were recorded from a number of chicks. The remaining chicks were raised until 6 weeks of age and body and organ masses, plasma concentrations of thyroid hormones, triglycerides and glucose were measured. Dose and stage during embryonic development at which injection was performed affected hatchability. Fifty nanogram of TCDD was highly toxic for 4-day-old chicken embryos. TCDD was less toxic for chicken embryos of 8- and especially 12-days old. One-day-old chick and organ weights were not different between TCDD doses at all injection days. However, injection performed at ED4 or ED8 with 20 and 50 ng, respectively, significantly depressed post-hatch body mass gain. Moreover, body mass gain in males was more depressed than in females. The delayed growth in TCDD treated chickens was accompanied by changes in T(3)/T(4) ratio that at some ages were significantly higher compared to control animals. No pronounced changes in plasma triglycerides or glucose concentrations during postnatal life were observed. Absolute and relative organ masses of 6-week-old chickens showed no remarkable changes.

Effects of strain, hen age and transferring eggs from turning to stationary trays after 15 to 18 days of incubation

1. A total of 39,000 eggs (260 incubation batches) produced by Hybro, Cobb and Ross were studied. They were transferred from incubators to hatchers at day 15, 16, 17 or 18 of incubation. 2. Hatchability increased in proportion to the day of transfer and it was higher when the transfer occurred at day 18, whereas the differences between hatchability for days 15, 16 and 17 were not significant. 3. The hatchability of the Hybro eggs was more affected by the transfer time, as were the eggs of the older flock (51 weeks and more). 4. The percentage of unhatched embryos increased with the age of the breeders and decreased with the day of transfer. In addition, the percentage of unhatched embryos was affected by the strain of hen. 5. It was concluded that transfer time has to be considered in order to optimise hatchability and chick quality, especially if the eggs from older flocks are incubated.

Effect of delayed feed access on production and blood parameters of layer-type chicks

A total of 684 Hisex Brown day-old chicks were studied. The chicks were randomly assigned into three groups as follows: (1) chicks with immediate feed access; (2) chicks with 48 h delay in feed access, and (3) chicks with 72 h delay in feed access. For each group, chicks were assigned into 4 replications of 57 birds each. Prior to feed access, the chicks were weighed. Samples of chicks were used to weigh yolk sac at 1, 3 and 7 days and to collect blood at 1, 3, 7, 14 and 56 days. Also, reared chicks were weighed weekly. The results indicated that chick weights decreased during the holding period. Yolk sac utilisation was similar between groups, while morbidity and mortality increased linearly with the duration of delay in feed access. At 56 days, chicks having delayed access to feed were lighter than those without delay in feed access. Serum concentration of glucose up to 14 days and of total protein and triglycerides until 56 days decreased with the increasing duration of delay in feed access. It can be concluded that delayed feed access is detrimental to the juvenile performance of layer-type chicks and has a negative age-related effect on the serum concentrations of glucose, triglycerides and total protein.

Current situation of fish farming in Togo

In Togo, fish farming is faced with several problems which oblige farmers to develop local production techniques that explain the low level of production. To assess the current situation, a survey was conducted to collect information on this activity in 91 Togolese fish farms located in the five regions of the country. The survey has shown the existence of two production systems, namely the extensive majority system (87.91%) practiced in ponds and water reservoirs and the semi intensive system (12.09%) implemented in tanks and ponds. The lack of accurate data has made it difficult to estimate production. Nevertheless, eight fish species are found in these environments in which tilapia ( Oreochromis niloticus ) and the African cat fish ( Clarias gariepinus ) represent 80% of farmed species. Feed, representing over 50% of fish production cost, remains the major constraint on the development of this activity. However, agro-industrial by-product resources were available depending on region and are recoverable for use as fish feed. This is the case for palm kernel meal which was abundant and little studied in Togo. Sociologically, fish farming was more a matter of group (61.54%) than individual (38.46%) activity. The extensive fish farming system deserves to be improved and agro-industrial by-products analyzed and valued for the promotion of fish farming in Togo. Keywords : Fish, food, fish farming infrastructure, agro-industrial by-products, palm kernel meal.