Thermal manipulations during broiler incubation alter performance of broilers to 70 days of age.

Recent decades have seen significant progress in the genetic selection of fast-growing broiler chickens. Whereas in many countries the average marketing age is 5 to 6 wk, the US, French, and other markets demand heavier broilers (~4 kg) that require a longer posthatching growing period. With greater age and greater BW, the ability to cope with hot weather conditions deteriorates, which can result in increased economic losses during periods of hot weather. Recent studies have demonstrated a long-lasting effect of intermittent thermal manipulation (TM) during embryogenesis, when it was applied for 12 h/d between embryonic (E) days E7 and E16, which was shown by improved thermotolerance during acute posthatching heat stress as well as improved feed conversion ratio (FCR) and breast muscle yield. The present study was designed to elucidate the effect of TM during embryogenesis on Cobb 500 broiler performance up to 70 d of age. Hatchability and male BW were not affected by TM, but TM females demonstrated a lower (P = 0.024) BW during the entire 70-d posthatching study. However, following embryonic TM, both sexes exhibited lower (P = 0.028 and P = 0.018 for males and females, respectively) feed intake and body temperature accompanied by improved FCR and greater breast muscle weight. In light of the present and previous studies, it was concluded that intermittent TM during broiler embryonic development had a long-lasting effect on energy balance that led to improved FCR and breast muscle yield.

Hatching egg characteristics, chick quality, and broiler performance at 2 breeder flock ages and from 3 egg weights.

The objective of this study was to determine the effects of flock age and egg weight on hatching egg characteristics, fertility, hatchability, salable chick production, and broiler performance using a commercial Cobb 500 broiler breeder flock. Hatching eggs from the same breeder flock in 3 weight categories (light, average, and heavy) were obtained from a commercial hatchery when the birds were 29 and 59 wk of age. One group of eggs per age and weight category was selected to assess specific gravity and was broken open to weigh egg components. Another group of eggs was incubated for 21.5 d and incubation parameters were measured. At hatching, all salable chicks were individually weighed and placed in floor pens, where they were grown out for 41 d. Daily mortality, weekly feed consumption, and individual BW at 21 and 41 d were recorded. Irrespective of flock age and egg weight, all eggs had a specific gravity lower than 1.080, the commercial set value. Eggs from the young flock age had a smaller proportion of yolk and a greater proportion of albumen. Age affected fertility, with a lower value observed at 29 wk of age. Chicks from the flock at 59 wk hatched earlier than chicks from the flock at 29 wk, and light eggs hatched earlier than both average and heavy eggs. Broilers from the 29-wk-old breeders had a lower final BW than broilers from the 59-wk-old breeders. The smaller proportion of yolk in eggs from 29-wk-old broiler breeders may be associated with the low final BW observed in their offspring. This could mean that chicks hatching from young broiler breeders, which produce eggs with small yolks, may be at a disadvantage when reared under the same conditions as chicks produced by older broiler breeders whose eggs have larger yolks.

Assessment of embryonic growth in chicken eggs by means of visible transmission spectroscopy.

During this work, it was investigated whether spectral measurements can be used to monitor embryonic growth. An experiment was conducted in which both the transmission spectra and embryonic weight were determined on 240 eggs (Cobb, 37 weeks) between Day 5 and Day 10 of incubation. The spectral data were linked to embryonic weight by means of a partial least squares analysis. Different preprocessing procedures were compared during this work, that is, smoothing, multiplicative scatter correction (MSC), and first- and second-order derivative. Compared to the remainder of the preprocessing procedures, MSC leads to a considerable improvement of the prediction capability of the embryonic weight. The ratio of performance to deviation obtained for the MSC spectra equaled 4.5 indicating that a very accurate prediction of embryonic weight is feasible based on the VIS/NIR transmission measurements. Important regions for the prediction are situated around 685-740 nm. It is suggested that the spectral changes in these spectral regions result from the displacement of carotenoids from the yolk into the blood circuitry.

Cost of growth and maintenance in chicken embryos during normoxic or hypoxic conditions.

During a large portion of embryonic development oxygen consumption (V(O2)) is mainly needed for maintenance (including organ function) and for growth. In an attempt to evaluate their relative contribution, we followed the assumption that the former is proportional to embryo's weight (W) and the latter to growth rate (GR), as V(O2)=aW+bGR, a and b being the respective proportionality coefficients. Fertile chicken eggs were incubated at the normal temperature (38 degrees C) and at various low-temperature conditions, which invariably decreased GR. At a few days intervals over the embryonic ages E9-E18, the W and V(O2) of the embryos were measured and GR computed from the age-W relationship. These simultaneous sets of W (g), GR (g/day) and V(O2) (ml/day) were used to solve the equation; a averaged 14.7 ml O(2) g(-1) day(-1) and b averaged 41.1 ml O(2) g(-1). Hence, over the period of incubation studied, the cost of growing 1g of tissue averaged about 3 times the cost of maintaining it. These coefficients were not significantly different whether computed during normal growth at 38 degrees C or during incubation at low temperatures, indicating that cooling only decreased GR and the cost required by it. Embryos incubated in hypoxia (15% O(2)) had low V(O2) originated not only by the decreased GR but also by a drop in the cost of maintenance, especially in the youngest embryos.

[Assessment of marbling in the eggs of local beeds of chickens]. / Otsenka mramornostta u kokoshi iaitsa ot mesni porodi.

A test was worked out to evaluate the presence of marbling in hen eggs, modifying Koulikov's method. Its use with a total of 26,011 eggs of hens, belonging to local breeds, revealed the presence of weakest, weak, and moderate marbleness as most frequently occurring (32.72; 48.53; 15.57 per cent); strong, and very strong marbling occurred least frequently, and third ranked the lack of marbling 1.92; 0.76; 0.48 per cent, respectively. The incubation of eggs of the same breeds showed that strong and very strong marbling affected adversely the results of hatching. The test can be applied in the productional and diagnostic control on hatcheries.