Introduction
Lysine may be the single most important amino acid that affects the protein nutrition of captive birds fed practical diets. It is the essential amino acid most often limiting in cereals and other seeds which comprise the main sources of nutrition for many caged birds. A deficiency of lysine in the diet of young domestic birds such as chickens, quail and turkeys results in poor growth and in failure to deposit the normal dark melanin pigments of feathers. Because body size and feather color are important considerations when assessing the value of caged birds, lysine nutrition had a high priority among problems that needed study.
This project was designed to determine the quantitative lysine requirement of young cockatiel chicks, based primarily on growth. Feather pigmentation was also studied. The basic approach was to feed newly hatched chicks diets in which the amino acids were provided by mixtures of pure amino acids in place of protein. The lysine content of the diet could thus be varied from low to high levels and the effects on growth and feathering determined.
Materials and Methods
The management techniques used here were virtually Identical with those we developed to determine solids requirements (Roudybush and Grau, 1983). The basal diet, presented In Tables 1,2, and 3, did not include lysine, which became the single variable in two feeding trials with groups of cockatiel chicks.
Table 1: Lysine Diets Experiment 1
Ingredient g/kg Lysine (%)
Soybean Oil 37.5 0.1 0.4 l.0 2.0
Cellulose 50.0 Basal 978.0g 78.0g 978.0g 978.0g
CaCO3 10.0 Lysine HCl 1.1 4.4 11.0 22.0
CaHPO4•2H2O 30.0 Starch 20.9 17.6 11.0 0.0
Vitamin Mix1 1.25 1000.0g l000.0g 1000.0g 1000.0g
Mineral Mix2 12.3
Choline Chloride (6O%) 4.2 Experiment 2
Amino Acid Mix3 239.0 Lysine (%)
Corn Starch 458.35 0.2 0.4 0.6 0.8 1.2
Instant Clear Jel4 130.0 Basal 988.0g 988.0g 988.0g 988.0g 988.0g
Na2C03 15.0 Lysine 2.0 4.0 6.0 8.0 12.0
NaCl 0.4 Starch 10.0 8.0 6.0 4.0 0.0
Total 988.0 1000.0g 1000.0g 1000.0g 1000.0g 1000.0g
1 Grau and Roudybush 1985
2 See Table 2 for mineral mixture.
3 See Table 3 for amino acid mixture.
4 Instant Clear Jel-Food Starch-Modified. National Starch and Chemical Co.
Bridgewater, NJ 08607.
Table 2: Mineral Mixture Table 3: Amino Acid Mix
Ingredient mg/Kg diet Ingredient g/kg diet
Manganese sulfate MnS04•H2O 297.00 L-Arginine1 11
Cupric sulfate CuSO4•5H20 97.00 Glycine 6
Colbaltous acetate Co(C2H302) • 4H20 20.00 L-Serine 3
Potassium iodate KIO3 9.00 L-Histidine1 5
Magnesium carbonate MgCO3 2752.70 L-Leucine 11
Dibasic potassium phosphate K2HPO4 4950.00 L-Methionine 5
Sodium molybdate Na2MoO4•2H2O 9.00 L-Cystine 3
Sodium selenite NaSe03•5H20 0.66 L-Phenlalanine 6
Zinc acetate Zn(C2H302)2 323.70 L-Threionine 7
Ferrous sulfate FeS04•7H20 644.00 L-Tryptophan 2
L-Valine 8
Total 12,271.06 L- Glutamic acid 127
L-Alanine 11
L-Aspartic acid 11
L-Proline 11
L-Isoleucine 7
L-Tyrosine 5
Total 239
1 Supplied as the hydrochloride in experiment 1, but
as the free base in experiment 2.
The levels of L-lysine added to the dry basal diet varied from 0.1% to 2.0%. Each group of 12-17 chicks was fed its diet from hatching to 14 days of age or longer. One of these experiments was concluded at 14 days, but then the chicks were fed either the same diets or were shifted to alternatives in order to observe recovery or, in the case of one group, the effects of imposing a deficiency half way through the growth period. Each bird was weighed each day before the first feeding at 6 a.m. Observations of feather pigmentation of all chicks were made from the time juvenile feathers could first be seen through the skin at 10 days until the experiments were concluded at fledging.
Results
In the first experiment, the groups were fed the four levels of lysine to 14 days, at which time the results of feeding the diets were clear. The lowest level of lysine (0.1%) permitted only poor growth and survival, but 0.4% permitted much better growth, as shown in the growth curve of figure 1. The groups fed 1.0% or 2.0% lysine grew well but not as rapidly as similar chicks fed 20% protein from isolated soybean protein supplemented with methionine, as presented in the report of our first study (Roudybush and Grau 1983).
After 14 days, when the group fed 2.0% lysine was shifted to the diet containing 0.4% lysine, growth continued at approximately the same rate for 8 days, essentially in the same pattern as the group fed 1.0% lysine for the whole period. Meanwhile the group that was shifted from O.4%lysine to the 20% protein diet grew rapidly and continued to gain up to the weight expected by fledging (80-90 grams).
The levels of lysine that had been chosen for the second experiment were based on the results of the first study. The lowest level (0.2%) permitted only slow growth (figure 2), but was better than 0.1% lysine in experiment 1. Groups fed higher levels grew faster until the level of 0.8% lysine was reached and when maximum growth was obtained. As in the first experiment, body weight at 14 days of age was used as the criterion for determining the lysine requirement, as shown in figure 3.
None of the groups fed the amino acid-containing diets grew as well as those fed the protein-based diet. No observable differences accounted for this effect.
With regard to feather pigmentation, no white or light feathers or parts of feathers were observed in areas that are normally dark. These observations were made in birds in which growth was responding to wide variations in the lysine concentrations of the diets.
Discussion
Until the experiments reported here were performed no data were available on the qualitative or quantitative requirements of cockatiels or other altricial birds for any amino acid. The results obtained with respect to growth effects are similar to those obtained with poultry and rats, with cockatiels apparently unable to synthesize lysine and thus completely dependent on the diet to supply it. After feeding several dietary levels to groups of cockatiels and noting the minimum concentration in the diet that permitted maximum growth, it was concluded that cockatiel chicks require 0.8% lysine in the solids portion of the diet when that diet contains approximately 20% protein. This fairly high requirement is not easily met by seeds alone, thus lysine is a nutrient that is marginal in many diets for breeding cockatiels that are feeding chicks.
The lack of effect of lysine deficiency on feather pigmentation is in marked contrast to that documented in turkeys, chickens and quail, in all of which lysine deficiency results in formation of feathers that lack melanin pigment. In those birds, abnormal white feathers are a diagnostic sign of lysine deficiency. When we began the lysine study we fully expected to see some effect of lysine deficiency in feathers, so the lack of effect was indeed surprising. Because so may different dietary levels of lysine were fed and such wide differences in growth were obtained, we believe it unlikely that any other level would have resulted in white feathers. At the lowest lysine level, feather growth, of survivors was poor, but at moderate levels while growth was slow feathers did develops and all appeared to have normal pigment.
The growth obtained with the amino acid based diet was less than that when soybean protein was fed, but this is not different from observations with other young birds. In order to achieve good growth in chicks, careful balancing by trial and error of the various amino acids was required, and even then the intact protein produced better growth.
Summary
The lysine requirement of cockatiel chicks that were hand—fed from hatching was found to be 0.8% of the dry portion of the diet. This diet, which contained amino acids equivalent to 20% crude protein, was fed at 7% solids for 3 days, then 30% solids to weaning. Poor growth was obtained with low levels of lysine, but feather pigmentation was normal at all lysine levels, and thus the effects of lysine deficiency on the melanin formation in cockatiels appear to differ strikingly from turkeys, quail, and chickens. It is concluded that satisfying the lysine requirement of young cockatiel chicks may be difficult with breeding diets based primarily on seeds.
1. Grau, C.R. and T.E. Roudybush. 1985. Protein requirement of growing cockatiels. Proc. 34th Western Poultry Disease Conference, Davis, CA March 4-6, 1985 in press.
2. Roudybush, T.E. and C. R. Grau. 1983. Solids in diets for hand raising cockatiels. Proc. 32nd Western Poultry Disease Conference, Davis, CA. Feb. 8-10, 1983, pp. 94—95.
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