Y. Pinchasov

Comparison of post‐hatch holding time and subsequent early performance of broiler chicks and Turkey poults

Abstract 1. The effect of a holding period, lasting up to 48 h post‐hatch, on early growth and mortality rate was studied in broiler chicks and turkey poults. 2. After 48 h of food and water deprivation, birds of both species lost about a tenth of their initial post‐hatch weight. Weight loss was more marked in poults subjected to heat stress. Thus, duration of the holding period adversely affected early growth. 3. During the 48‐h holding period, the relative weight of residual yolk decreased in both species by approximately half of its weight in the just hatched chicks and poults. Relative yolk size was much higher in poults than in broilers. 4. On day 1 weight loss was attributed to degradation of the yolk sac, whereas on day 2 only about two‐thirds of the loss could be attributed to residual yolk. Body composition of newly‐hatched broiler chicks did not differ from those held for 24 h despite shortages of energy. However, after 48 h body fat content was markedly reduced compared to newly‐hatched or 24‐h...

Relationship between the weight of hatching eggs and subsequent early performance of broiler chicks

1. The effect of egg weight on the subsequent performance of individual growing chicks was studied. Eggs from commercial broiler breeder hens were collected at 52, 55 and 57 weeks of age and incubated. The chicks were reared for 18 d. 2. Egg weight and hatched chick weight were not affected by the age of the hens during the 52 to 57-week period, but there was a close correlation between egg weight and hatching weight, irrespective of the age of the hens (r = 0.89). Chick:egg weight ratio at hatching was about 0.71 and independent of hen age. One d after hatching, chick weights had decreased by about 1.5 g. 3. The initial high correlation between egg weight and chick weight decreased markedly during post-hatching growth, becoming insignificant 5 d after hatching. At 18 d of age, however, chicks from eggs of older hens tended to be heavier than those from younger birds. The greater 18-d weights appeared to be associated more with higher food intake during that period, than with greater egg weight. 4. It was concluded that, in individual broiler chicks, the advantage of the initially higher weight attributable to a larger egg diminishes rapidly after hatching, and the main factor affecting final body weight is food intake.

Metabolic and anatomical adaptations of heavy‐bodied chicks to intermittent feeding. 2. pancreatic digestive enzymes

1. Activities of digestive enzymes in meat-type chickens under ad libitum or alternate-day feeding were determined from 14 to 83 d of age. 2. Final body weight of intermittently fed birds attained 75% of that of the ad libitum-fed controls. 3. When compared with the ad libitum-fed counterparts, a marked increase in the relative weight of the pancreas and intestinal contents were found on repletion days. On depletion days the relative weights of the pancreas and of the intestinal contents were about half those found in ad libitum-fed birds. 4. The activity of the digestive enzymes in the pancreas, expressed as U/g pancreas or U/kg body weight, was not affected consistently by the feeding regime. In the small intestine a marked increase in relative activity (U/kg body weight) was observed on repletion days and a marked decrease on depletion days as compared with ad libitum-fed controls. The activities per g intestinal contents following food restoration did not differ significantly from those of ad libitum-fed controls except for trypsin, which was higher in the former. On depletion days the activities per g intestinal contents were lowest, lipase excepted.

Efect of intermittent feeding on blood plasma growth hormone and prolactin in chickens of a heavy breed

1. Variations in plasma growth hormone (GH) and prolactin concentrations were determined during growth (at 20, 33, 56 and 83 d of age) in ad libitum (control) and intermittently (alternate days) fed chicks. 2. In each group of birds the concentration of plasma GH was inversely related to age. The mean prolactin concentration was highest in the youngest (20-d-old) birds. 3. The concentration of plasma GH in the intermittently-fed birds deprived of food for 24 h (depleted birds) was significantly higher than that in the controls at 33, 56 and 83 d of age. The mean GH concentration in the intermittently-fed birds 24 h after refeeding (repleted birds) was less than that in the depleted ones. 4. The overall mean concentration of plasma prolactin in the depleted birds was significantly less than that in the control and repleted birds. 5. These results are consistent with the effects of fasting on GH and prolactin secretion and demonstrate that growth retardation in the intermittently-fed birds was not due to impaired GH secretion.

The synthesis in vivo of proteins in various tissues in chickens adapted to intermittent feeding

1. Protein synthesis was estimated in vivo in breast (superficial pectoral) and tibia (gastrocnemius) muscles, liver, kidney, pancreas, crop, duodenum, jejunum and ileum, using L-[U-14C]lysine injection. The effect on incorporation of [14C]lysine 1 and 2 h after injection was examined in five chickens adapted or not adapted to intermittent feeding. 2. Incorporation of [14C]lysine into tissue decreased in magnitude in the following descending order: pancreas greater than jejunum, duodenum greater than ileum, crop, liver greater than kidney greater than tibia, breast muscle and blood plasma. 3. The incorporation of [14C]lysine into muscle protein was higher in chicks after 24 h of refeeding than after 24 h of food deprivation. These differences were higher in adapted than in non-adapted birds. On days of refeeding the rate of incorporation exceeded that found in chickens fed ad lib. 4. Bound 14C from lysine in the intestinal segments was less than in control birds after food deprivation and greater after refeeding in non-adapted chicks only. 5. A negative relation was observed between bound and free 14C in muscles and in other tissues. 6. Short- and long-term adaptations to feeding regimens are discussed.

Early transition of the digestive system to exogenous nutrition in domestic post-hatch birds

The effect of early transition of the digestive system to exogenous nutrition was examined in three experiments with growing birds. A nutrient mixture (0.5 ml) of glucose, starch and oil (1:1:0.5, by vol) was orally administered immediately after hatch to turkey poults (Meleagris gallopavo) having immediate or delayed access to feed (Expt 1). Increasing amounts (0, 0.25 and 0.5 ml) of this mixture were administered immediately after hatch to turkey poults (Expt 2), or to broiler chicks (Gallus domesticus; Expt 3). The relative weights of the gastrointestinal tract (GIT) and its ingesta content, and the amylolytic capability of the pancreas were examined during the immediate post-hatch period (to 30 h). Oral administration of nutrients immediately after hatching only slightly influenced the growth of the pancreas and its amylolytic activity, but significantly increased GIT weight in both species, in a dose-dependent manner. It is suggested that early post-hatching exposure of the digestive system by the forced administration of nutrient mixture induces anatomical and metabolic changes in the digestive system slightly earlier than in birds with late access to feed. This increases GIT content and plasma glucose levels, resulting in enhanced feed consumption and growth promotion.

The possible prediction of fatness in broiler chickens by biochemical measurements on adipose tissue.

1. The possible prediction of fatness in 6-week-old broiler chickens was examined by measuring lipoprotein lipase (LPL) activity and lipid content in the abdominal adipose tissue. 2. Fat pad weight, as representing the degree of fatness in broiler chickens, was moderately well correlated (r = 0.54) with lipid content (g/100 g pad) and negatively correlated with LPL activity (r = 0.13). 3. It was concluded that the measurement of lipid content in samples from adipose tissue can be indicative of fatness of birds, while enzymic measurements are less valuable.

Muscle growth and composition in heavy and light breed chickens adapted to intermittent feeding

1. The effect of intermittent feeding in chickens of heavy breed (HB; meat type) and light breed (LB; egg type) on skeletal muscle growth and composition was studied in adapted and non-adapted chickens. 2. Food intake, relative to body-weight, was similar in both breeds but was higher in ad lib.-fed than in intermittently fed birds. 3. On repletion days the relative growth rate was similar in both breeds, while on depletion the LB chickens lost more weight than the HB chickens. In both breeds, the relative growth was higher in the intermittently fed birds during days of food restoration than in those fed ad lib. 4. The relative weight of the breast muscle was higher in HB birds than in LB birds, but deposition rate on the day of food restoration was similar in both breeds. This growth was more pronounced in chickens adapted to alternate feeding than in chickens exposed to this feeding regimen for one cycle. 5. Protein concentration in breast muscle was not affected by age and was slightly higher in LB chickens than in HB chickens. Soluble protein was markedly reduced on days of repletion, and more at 46 d than at 18 d of age. 6. The RNA:DNA ratio was higher in HB than in LB chickens, and lower on days of food deprivation than on days of food restoration. After repletion this ratio returned to the level of the ad lib.-fed chickens. While in LB chickens cell size (as estimated by DNA concentration) remained constant on repletion and depletion days, in the HB chickens it decreased. 7. The rapid growth of breast muscle in HB chickens was attributed to the higher rate of protein synthesis (estimated by RNA:DNA ratio) compared with LB chickens. This may also explain why the breast muscle of LB chickens was less sensitive to intermittent feeding than that of HB chickens.

Water intake and water concentration in the body and gastrointestinal tract of intermittently fed broiler chickens

The relationship between water intake and water concentration in the body and in the gastrointestinal contents was studied in meat-type chickens fed either intermittently or ad libitum, as controls. In experiment 1, male broilers were reared from 12 to 33 d of age and were fed every second day or ad libitum. The water consumption of the intermittently-fed birds on days of food removal was 31% of the consumption of the control group. On days of food restoration their water consumption exceeded that of the controls, by 27%. No significant differences in water:food ratios were found between birds fed intermittently or the controls on days of food restoration. The restricted birds had a lower fat and a higher protein concentration in the body. No relationship was found between water:food ratio and body composition. In experiment 2, birds were kept on the same feeding regimes from 12 to 46 d of age. The water content of the pancreas increased after food restoration compared with ad libitum feeding or food deprivation. The amount of water in the gastrointestinal contents increased progressively from crop to ileum. The feeding regimens had no effect on the water content of the intestine.