Effect of hen age, body weight, and age at photostimulation. 2. Embryonic characteristics of commercial turkeys

The effects of genotype on embryonic development in eggs from divergent turkey genotypes

Unique turkey genotypes and reciprocal crosses of these lines were used to study the relationship between egg size, posthatch growth potential, and selected aspects of embryonic development. A line of turkeys selected for increased egg production (E), its randombred control line (RBC1), a line selected for increased 16-wk BW (F line), and its randombred control line (RBC2) were the pure lines used in each of 2 experiments. In experiment 1, a sample of E-line hens were mated to either E line (E/E) or RBC1 toms (RBC1/E), and RBC1 hens were mated to RBC1 toms (RBC1/RBC1). Egg weight at set and at 25 d of incubation was significantly lower in the E/E and RBC1/E crosses compared with that of the RBC1/RBC1 eggs. On d 21 and 25 of incubation and at hatch, the yolk-free wet embryo weights of E/E and RBC1/E embryos were similar, and both weighed significantly less than the RBC1/RBC1 embryos (P ≤ 0.001). Similar observations were observed for the residual yolk sac weight at each of those developmental ages. In experiment 2, embryos from the F line, RBC2, RBC1, E, and 2 reciprocal crosses (RBC1/E, E/RBC1) were compared at various time points during the course of incubation. Egg weight was consistently highest in the F line and lowest in the E line and intermediate in the RBC1 and RBC2 lines. Egg weight followed the maternal genotype in the E/RBC1 and RBC1/E reciprocal crosses. On embryonic d 19, 23, and 26, the order of yolk-free weight embryo weights followed closely the pattern observed for egg weight. In summary, egg weight and embryonic development is largely controlled by the maternal genotype. This should be considered when making inference to posthatch selection effects on embryonic development.

Comparative development of the small intestine in the turkey poult and Pekin duckling

Turkey poults and Pekin ducklings hatch from eggs of similar weights and have the same incubation periods and body weights at hatch. The male Pekin duckling, however, can attain a market weight of 3.2 kg in approximately 6 wk, whereas at the same age, male turkeys only weigh approximately 2.1 kg. For this study, fertile turkey eggs (n = 400, mean weight: 87.2 g, range: 85 to 89.9 g) and Pekin duck eggs (n = 565, mean weight: 88.6 g, range: 85 to 92.0 g) were weighed and incubated. Embryos and hatchlings were sampled during the last week of incubation, at hatch, and through 7 d of age. Yolk-free BW of poults were 2.7 g heavier than ducklings at hatch. Yolk-free BW of ducklings, however, were greater than poults at 1 d of age (P > or = 0.06), and by 7 d of age ducklings were 140 g heavier (P < or = 0.01). Yolk sac weight was similar at 21 and 25 d of incubation, yet was significantly lower in ducks at hatch, 1, and 2 d of age (P < or = 0.05). In the duckling, jejunum and ileum weights (3.7x heavier), length (1.6x longer), and density (g/cm; 2.3x more dense) were consistently heavier than in the turkey from hatch through 7 d (P < or = 0.01). Histological sections of the distal jejunum revealed more rapid villus growth in the duck from 0 to 3 d of age. The combination of increased intestinal growth (weight and length) and maturation (villus length) allowed ducks to achieve an additional 143 g of BW gain during the critical hatch through 7 d of growth.

Effect of turkey (Meleagridis gallopavo) breeder hen age and egg size on poult development. 1. Intestinal growth and glucose tolerance of the turkey poult

Three experiments were conducted to determine if turkey (Meleagridis gallopavo) hen age and egg weight affect poult intestinal development and glucose tolerance during the first week after hatching. Differences in glucose tolerance were not consistent across the experiments. In experiment 1, 4-day-old poults from the younger hens and lightest egg weight class had significantly greater fasting plasma glucose concentrations (P < 0.04) and were also higher at 30 and 60 min post-injection of 250 mg glucose. In experiment 2, egg weight class had no significant effects on plasma glucose concentrations of 4-day-old poults (after injection of 2.5 mg glucose/g body weight). In experiment 3, plasma glucose concentrations were not different between groups at 0 or 30 min post-injection (3.75 mg glucose/g body weight), however, poults from the younger hens had 79-90 mg/dl higher plasma glucose concentrations 60 min post-injection versus poults from the older hens. Neither egg weight class or hen age consistently affected small intestinal weight, length, or density (g/cm) measures across experiments.

Effect of turkey (Meleagridis gallopavo) breeder hen age and egg size on poult development. 2. Intestinal villus growth, enterocyte migration and proliferation of the turkey poult

Villus growth, enterocyte migration and proliferation were measured in the small intestine of poults (Meleagridis gallopavo) to determine if hen age and/or egg size influences these characteristics during the first week after hatching. At hatching, distal jejunal villi were 22.8 microns longer in poults from the older (48 weeks) versus the younger (34 weeks) hens (P < 0.05). Similarly, labeled enterocytes in distal jejunal sections from poults from the older hens had migrated 28 microns (10%) farther along the crypt-villus axis at hatching, as compared to poults from the younger hens (P < 0.05). Villus growth differences and enterocyte migration were not consistently affected by hen age or egg weight class in poults from 1 to 7 days old. These results suggest that even though intestinal villi may be more advanced developmentally at hatch in poults from the older hens, however post-hatch growth of the intestine or the poult is not affected by hen age or egg weight class.

Effect of hen age on intestinal development and glucose tolerance of the Pekin duckling

Two experiments were conducted to determine whether hen age affects intestinal development and glucose clearance in Pekin ducklings after hatching. In Experiment 1, 85- to 92-g eggs were collected from 32- and 44-wk-old hens. The eggs from older hens contained proportionately more yolk, which resulted in a greater mass transfer of yolk sac DM and lipid from 21 to 25 d of incubation, and ducklings from older hens were heavier at hatching (P < or = 0.0001). Although the ducklings from the older hens were heavier at hatch, BW, feed consumption, and feed efficiency were not significantly different from 7 to 35 d of age. During the first wk after hatching, the age of the hen had no consistent effect on duodenum or lower small intestinal measurements (weight, length, or density). Hen age did not significantly affect plasma glucose concentrations at 0, 30, or 60 min post-injection of glucose (2.5 mg per g BW) in 3- or 6-d-old feed-deprived ducklings. In a second experiment, 85- to 90-g eggs were collected from 33- and 48-wk-old hens to determine whether differences in hen age caused a differential response to a challenge with a higher glucose dosage at 3 d of age. No differences between hen ages were apparent in plasma glucose concentrations at 0 or 30 min postinjection (3.75 mg glucose/g BW). At 60 min postinjection, however, the ducklings from the younger hens had 100.6 mg/dL greater plasma glucose concentrations than the ducklings from the older hens (P < or = 0.02). The glucose tolerance results suggest that differences in metabolism exist between ducklings from the younger hens, even though measurable BW differences did not exist.

Effect of hen production age on egg composition and embryo development in commercial Pekin ducks

At 26, 31, 36, and 42 wk of age, eggs were collected from the same duck breeder flock to study the effects of hen production age on egg composition and embryo development. At each hen age, yolk and albumen measurements were made on a random subsample of unincubated eggs. Embryo and yolk sac measurements were made at 20, 22, 24, 26, 27, and 28 d of incubation. Egg weight was significantly affected by hen production age, but most of the observed age effects occurred between 26 and 31 wk with minimal age differences thereafter due to a quantitative feed restriction for egg weight. Yolk weight increased significantly with hen production age, with the largest increase, 6.6 g, also occurring between 26 and 31 wk of age. Yolk-free duckling weight increased with hen production age at 27 d of incubation. The yolk sacs of embryos from the 31-, 36-, and 42-wk-old hens were heavier at 20 and 22 d, before the differentiation in embryo weight. Differences in yolk sac weight were not consistently affected by hen production age between 26 and 28 d of incubation. The eggs from the 42-wk-old hens weighed 3.3 g less than those from the 31-wk-old hens, but yolk-free duckling weight at 27 d was 2.9 g heavier from the 42-wk-old hens.