The amino acid and energy requirements of broiler breeder hens

Dietary methionine source and level affect hepatic sulfur amino acid metabolism of broiler breeder hens

A study was carried out to investigate the effects of dietary methionine source and level on plasma free amino acids patterns and the expression of genes involved in hepatic methionine metabolism in broiler breeders. A total of 2184 broiler breeders were assigned to 13 dietary treatments, with eight replicates per treatment. The 13 treatments included one control group and 12 additional treatments employing two sources and six levels (0.05, 0.10, 0.15, 0.20, 0.25 and 1.00%). Higher plasma methionine concentration was measured for DL-methionine (DLM) treated hens. Plasma alanine concentration was linearly increased as DLM or 2-hydroxy-4-(methylthio) butanoic acid (HMTBA) supplementation level increased. There was a linear increase in concentrations of tyrosine, valine, glycine and serine as dietary DLM supplementation level increased. Hens treated with DLM had higher relative expression of ADA than those fed HMTBA. The expression of MS, ADA, SAHH and MAT2A changed quadratically as HMTBA supplementation level increased, while the expression of GNMT and SAHH changed quadratically as DLM supplementation level increased. In conclusion, the effects of HMTBA on plasma free amino acid patterns and the expression of hepatic genes involved with methionine are different from DLM.

Modeling metabolizable energy utilization in broiler breeder pullets

The objective of this study was to determine models for ME requirements for broiler breeder pullets using the factorial method. The influence of the temperature on maintenance ME requirements was determined by experiments conducted in three environmental rooms with temperature kept constant at 15,22, and 30 degrees C, using the comparative slaughter technique. The energy requirements for weight gain were determined based on the body energy content and efficiency of energy utilization for weight gain. Two ME requirement models for each age were developed using the coefficients for maintenance and weight gain. The models for 3 to 8 wk were ME = W(0.75) (186.52 - 1.94T) + 2.47WG, and ME = W(0.75) (174 - 1.88T) + 2.83WG; for 9 to 14 wk, ME = W(0.75) (186.52 - 1.94T) + 2.69WG, and ME = W(0.75) (174 - 1.88T) + 2.50WG; and 15 to 20 wk, ME = W(0.75) (186.52 - 1.94T) + 2.76WG, and ME = W(0.75) (174 - 1.88T) + 3.24WG. In these equations, W is BW (kg), T is temperature (degrees C), and WG is daily weight gain (g). These models were compared to the breeder's recommendations in a feeding trial from 5 to 20 wk of age. Models 1 and 2 provided energy intakes that promoted BW smaller than the breeder's recommendation. However, all breeder pullets had weights above the standard recommendation. Model 2 gave the smallest ME intake and BW close to the standard recommendation and provided the best prediction of ME requirements.

Effect of dietary protein intake during the pullet-to-breeder transition period on early egg weight and production in broiler breeders

The effects of CP intake on broiler breeder hen performance were evaluated. A flock of pullets was reared in floor pens from 0 d to 20 wk of age. At 20 wk of age, 96 pullets were randomly assigned to one of three feeding regimens with 14, 16, or 18% dietary CP. Daily feed allocation from 20 to 29 wk of age was identical for all three treatments and was based on the BW of the birds fed the 16% CP diet. Photostimulation occurred at 22 wk of age. At 29 wk of age, the hens were killed for determination of carcass characteristics. Dietary protein intake did not influence BW or BW gain throughout the trial. There were no differences in age at sexual maturity among treatments. From 25 to 28 wk of age, the hens on the 16 and 18% CP treatments had a significantly greater egg weight than did hens in the 14% CP group. The 14% CP treatment was unable to sustain as high a level of egg production as the other two treatments at 29 wk of age. The number of settable eggs was also lowest for the 14% CP treatment. The CP level in the diet did not affect the weights of the Pectoralis major or minor. Carcass composition was also not different among the treatments. Increased levels of CP in the prelay and early lay diets increased egg size and production rate although had minimal effect on carcass and ovarian parameters.

Genetic-economic evaluation of traits in a goose meat enterprise

1. Goose can be considered as an additional and inexpensive meat source, provided that the marketing age does not exceed 8 weeks. Using the ability of geese to eat grass may reduce the intake of concentrated food up to 30%. 2. According to an equation developed, growth rate accounts for about 58% of the annual breeding gains, egg number 28%, feather yield 10%, fertility and mortality about 2%. These values are about the same for a wide range of food prices. 3. Employing realistic values for expected annual genetic gains reveals that the customary practice of keeping breeders for 5 to 6 years should be replaced by a much shorter cycle of 3 years because the economic gain from the shorter generation interval of selection exceeds the replacement costs.

Lysine: Amino acid requirements of broiler breeders

Because feed intake is controlled in broiler breeders, amino acid supply is determined by the composition of the feed and the level of feed intake. Controlling amino acid supply during the laying cycle can be facilitated by the use of a model for calculating requirements. A possible model is outlined and the various components discussed. Typical calculations suggest that the model can provide a useful basis for practical feeding decisions. Model elements include: levels of animal performance; utilization of amino acids for egg production, maintenance, and tissue growth; population structure; and the variation of feed intake and the covariance between feed intake and requirements.

Re-evaluation of the methionine and protein requirements of the broiler breeder hen

Three experiments were conducted to study the Met and protein requirements of Arbor Acres broiler breeder hens. Broken line regression analysis in Experiments 1 and 3 indicated the Met requirement was 335 and 323 mg/d, respectively, with a production of a daily egg content (EC) of 42.3 or 43.0 g. A broken line could not be fitted to the data in Experiment 2. Therefore, this procedure could not be used to calculate a requirement. An average of 7.83 mg Met was required to produce 1 g of EC. Using this value, the requirement for the three experiments would be 344 mg at the level of EC produced in these experiments. The requirement would be higher with either a higher rate of lay or with larger eggs.

A re-evaluation of the protein and lysine requirement for broiler breeder hens

An experiment was conducted with 32-wk-old Arbor Acres broiler breeder hens to determine their requirement for Lys and protein. Diets were fed with Lys levels ranging from .545 to .380% and with protein levels ranging from 11.46 to 8.90%, respectively. A daily intake of 845 mg of Lys per hen per d was required for maximum egg production, egg mass, and egg content. A daily intake of 18.07 g protein was required with a corn-soybean meal diet containing no supplemental amino acids. However, when Met and Lys were added to the diet, daily protein intakes of 15.53 and 16.37 g supported performance that was not significantly different from performance of hens receiving higher levels of protein.

Daily energy allotments and performance of broiler breeders. 2. Females

Arbor Acres broiler breeder hens, 21 to 61 wk of age, were given the daily ME level recommended by the primary breeder for their age and level of production (100% AA) or were given 94 or 88% of that amount. The reduction in daily energy allotment had no effect on age at 50% or age at peak production, but there was a highly significant linear decrease in the eggs per hen from 165 +/- 2.8 in hens given 100% AA to 149 +/- 3.2 and 141 +/- 3.8 in hens given 94 and 88% AA. The percentage of nonlaying hens between 44 and 60 wk of age was substantially increased as daily energy allotment was reduced. The percentage settable eggs was significantly lower in the 100% AA group, but no differences in fertility or hatchability were seen. Chicks per hen fell from 123 +/- 2.4 to 116 +/- 2.4 to 102 +/- 2.6 as energy allotment was progressively reduced. Dietary energy allotment had no effect on egg weight, shell weight, shell characteristics, or proportion of albumen and yolk. Chick weight was unaffected but chicks' liver weight increased with increasing dam energy intake. Percentage lipid in hens' carcasses increased with increasing energy intake and percentage protein and percentage ash decreased.

Energy requirement of feed-restricted broiler breeder pullets

The energy requirements for growth and maintenance of broiler pullets were studied during a 17-wk growing period. Four flocks of commercial broiler replacement pullets, housed in conventional poultry houses, received a restricted amount of feed on 4 or 5 days a week, and pullet growth was recorded. The energy needs for maintenance and body weight gain under a feed restriction regimen was calculated using a model based on metabolic body weight and weight gain described by Hurwitz and coworkers. Average daily body weight gain for the entire experimental period was 13.7 g; the daily energy intake increased with age from 114 kcal/day at 3 wk of age to approximately 270 kcal/day at 20 wk. The estimated daily metabolizable energy requirement for maintenance was 1.57 kcal/g of body weight67 and for growth, .71 kcal/g of body weight. It was concluded that the energy requirement for birds under a feed restriction regimen is considerably lower than those under ad libitum feeding.

Biotin requirements of broiler breeders fed diets of different protein content and effect of insufficient biotin on the viability of progeny

Production of eggs or normal chicks was depressed when practical diets containing 168 g or 137 g of crude protein (CP)/kg were not supplemented with synthetic biotin. Overall egg production and hatchability of fertile eggs was significantly (P less than 0.05) higher with the diets containing 137 g CP/kg. Biotin requirement was higher with the diet containing 168 g CP/kg and was estimated to be about 100 micrograms of available biotin/kg, equivalent to a daily intake of 16 micrograms for food-restricted hens. Biotin concentrations in egg yolk and chick plasma were related to maternal intake and increased with maternal age. The minimum yolk biotin concentration indicative of adequate maternal status was about 550 micrograms/g. Chicks from young hens fed insufficient biotin had the poorest biotin status at hatching and their growth potential and viability were reduced.

[Protein utilization as well as crude protein and amino acid requirements of broiler hens]

After N-balance experiments with broiler hens in the top laying period and the feeding of soybean coarse meal/fish meal protein the protein utilisation values were calculated. The PNu curve and the PEW curve could be described as utilisation values from the N-retention curve (e-function). At an intake of N at which the hen neither decomposed nor retained protein, the utilisation (PNu) for maintenance and egg production was 55.3% and the utilisation of feed protein for egg production 49.4%. Maximum PEW 34.3% could only be ascertained at an N-intake/LW0.67kg of 1500 mg. The corresponding crude protein quota of 18.7 g recommended as crude protein requirement is calculated from this N-quota (xm) and a live weight of the broiler hen of 2804 g. For the same N-quota (xm) and the same live weight of the hens this results in a necessary quota of S-AA of 694 mg per hen and day. Provided the daily feed intake is 145 g and thus the intake of crude protein 18.7 g and that of S-AA 694 mg per hen, the necessary crude protein content of the feed is 130 g per kg original substance and an S-AA concentration which is equivalent to 3.7% of the crude protein (in g/16 g N).

Body weight and/or fatness as potential determinants of the onset of egg production in broiler breeder hens

In four trials during consecutive years individually-caged birds were weighed at first egg, and in the first two trials they were then killed to determine abdominal and skin fat, in order to establish whether there is a minimal body weight and/or body fat pool required for the start of egg production in broiler breeder hens. There were negative correlations ranging from significant to negligible between body weight and age at first egg. For birds of the same strain on a conventional food restriction regimen, the average weight range at first egg in the four trials was 3.3 to 3.7 kg, which may be a strain characteristic. In spite of severe food restriction, all birds were very fat at first egg. The correlations between fat concentration and age at first egg were negative. In mature pullets a minimum concentration of stored, easily mobilised fat may be essential for yolk formation and ovulation.

Genetic-economic evaluation of traits in a broiler enterprise: the relative genetic-economic values

Selection for growth rate and food utilisation (assuming annual genetic gains of 3 and 1.5% respectively) have about the same economic value and account for 94.3% of the annual potential economic savings in the production costs of an integrated broiler enterprise. Selection for more hatching eggs (annual genetic gain of 1.7 eggs) accounts for only 4.2% and selection for fertility, hatchability and reduced mortality have a value of less than 1% each. The introduction of the dwarf gene (dw) has a questionable economic value. Even if growth rate and fertility are not reduced by using dwarf females, the economic importance will equal no more than two generations of selection for growth rate. As egg production increases, the relative economic value of growth rate and food utilisation will increase, while the advantage of using dwarf females will decrease. Both body weight and body fat content (which are correlated with food utilisation) are moderately heritable and if body fat can be measured reliably in live birds, this may aid breeding for economic advantage.