Introduction
Avian nutrition has primarily been studied using chickens or other precocial birds as experimental subjects. Research with altricial birds was begun at the Department of Avian Sciences in 1979. Cockatiels were selected due to their practical size, moderate price, and sexual dimorphism. For the past3years, nutrient requirements of hand—fed chicks have been studied using growth and survival as the criteria for evaluation. The aim of this study was to establish a standard growth curve from parent—fed cockatiel chicks to be used as a basis for comparison with hand—fed birds.
Materials and Methods
To evaluate the growth responses of hand-fed cockatiel chicks, parent-fed chicks were also weighed daily. Growth results from hatch to 35 days are compared in this paper.
Parent-fed Chicks
Breeding pairs of cockatiels, which previously had their eggs removed for artificial Incubation, were allowed to continue to lay, hatch their eggs, and rear chicks. A 20% protein, crumbled diet (Table 1) and water were available to the breeding birds ad libitum. There were twenty-seven parent-fed chicks in this group. Most had food in their crops weighed.
Hand-fed Chicks
Hand-fed chicks were the control birds from 4 nutrient requirement experiments (described here as Trials 1-4, see Table 2). A purified diet containing 20% protein (Grau and Roudybush, 1985) was fed in all trials. Chicks were fed with sterile plastic disposable syringes. For Trial 1, hatch times were recorded from 6 am to 10 pm. Any chicks hatching after 10 pm or before 6 am were recorded as hatching at 6 am. For Trials 2-4, hatch times were recorded around the clock. The diet, consisting of 7% solids and 93% water, was fed every 2 hours from 6 am to 10 pm beginning at hatch. When a change was made to 30% solids and 70% water, feedings were cut back to every 4 hours from 6 am to 10 pm. As the chicks grew and it took longer for their crops to empty, the number of feedings per day was reduced. The crops of birds in Trial 1 wee filled to capacity causing some birds to regurgitate. Birds In Trials 2 and 3 were fed until the crop appeared rounded. The crops of Trial 4 chicks were filled to just below the bend in the neck initially, and then the same as in Trials 2 and 3 (see Table 2 and Fig. 1). Chicks were weighed daily before the morning feeding when their crops were empty.
The chicks from Trial 3 were weighed before and after each feeding to determine daily food intake and body weight gained. The ratio of food consumed to weight gained (feed conversion) was calculated. To evaluate the relative consumption during growth, the ratio of dry food intake to mean body weight was also calculated.
Table 1. Composition of crumbles diet for cockatiels
Ingredients per 1000g diet
Corn, yellow, ground 817.7 g
Soybean protein, isolated,
87% protein 144.6
Calcium carbonate, CaCO3 6.4
Dicalcium phosphate, CaHPO4•2H20 25.7
DL-Methionine 2.6
Mineral mixture (see below) 1.2
Vitamin mixture (see below) 1.8
Total 1000.0 g
Mineral Mixture Vitamin Mixture
Potassium chloride, KC1 990 Vitamin A 2500 EU
Manganese sulfate, MnSO4•H2O 141.2 Vitamin D3 500 RI
Copper sulfate, CuS04•5H20 5.4 Vitamin B12 0.009 mg
Potassium iodate, KIO3 0.6 Vitamin K 0.8 mg
Sodium selenite, Na2SeO3•5H20 0.25 Niacin 30 mg
Zinc oxide, ZnO 39.6 Riboflavin 3 mg
Folic acid 0.3 mg
Total 1177.05 mg Biotin 0.015 mg
Pantothenic acid 7 mg
Choline chloride 1020 mg
Total 1800mg
Table 2
Hand-feeding Trials
Trial n Diet* dilution and feeding schedule Appearance of crop
1 14 7% solids, 93% H 0 from hatch to Day 4; Crops filled until they
30% solids, 70% from morning of Day 4 ballooned outward.
to weaning.
2 14 7% solids, 93% H20 from hatch until 48 hrs Crops filled until the
after 1st meal. 30% solids, 70% H20 wrinkles in them
from 48 hrs to weaning. disappeared.
3 10 Same as Trial 2. Same as Trial 2.
4 8 Same as Trial 2. Crops filled to below
the bend in the neck for 9 days, then as in trial 2.
* Grau and Roudybush, 1985.
Figure 1. Crop appearance of cockatiel chicks after hand feeding.
Results
The growth of parent-fed chicks differed from Trial 1 hand-fed chicks (Fig. 2) in two ways. First, during the initial 4 days, parent-fed birds tripled their weights while hand-fed birds only increased their weights by 50%. Second, peak body weights of parent-fed birds exceeded their five-week weights by 12%, whereas peak weights of hand-fed birds exceeded their five-week weights by 50%. By 34 days of age both groups of birds reached approximately the same mean weights.
Chicks that were fed 30% solids at 48 hours of age (Trial 2) showed a 15% increase in weight from day 2 to 3. Chicks being fed 7% solids at 48 hours of age (Trial 1) only increased their weight by 7.8% (see Fig. 3 inset).
Figure 4 shows feed conversion and dry food intake/body weight ratios for Trial 3 birds. For days 1 and 2 the ratio of dry food intake to body weight was low, feed conversion was poor, and birds did not grow. Increased dry food intake and improved feed conversion resulted in a period of rapid body weight gain during days 4 to 13.
During the rapid growth phase, Trial 2 birds showed more fluctuations in growth than Trial 1 birds (Fig. 3). Additionally, Trial 2 birds did not exhibit the high peak weights seen in Trial 1.
The initial cautious feeding during Trial 4 while a new feeder gained experience resulted in slow growth until day 9 when relative meal sizes were increased (Fig. 5). After the increase in meal size, growth increased and paralleled that of the parent-fed birds. Body weights of Trial 4 chicks and parent-fed chicks were similar at 35 days.
Discussion
Utilization of food eaten by a growing animal can be partitioned into two components: 1) food used to maintain body functions - the maintenance requirement and 2) food above the maintenance requirement that can be used for growth. Feed conversion (the ratio of food intake to body weight gain) measures the efficiency of food utilization by the animal.
When the feed conversion value is low, food utilization is efficient. As food intake increases, maintenance requirements are met and food becomes available for growth. This happened on day 2 of Trial 3. There was an increase in the ratio of food intake to body weight caused by the increase in dietary solids from 7% to 30%. Food became available for utilization beyond maintenance and growth occurred.
Prior to day 2, food intake was low and feed conversion values were high. This indicates that when birds are fed 7% solids, they are only receiving enough energy for maintenance and limited growth. Unfortunately, the level of solids cannot be increased prior to two days of age because levels greater than 10% have been shown to cause mortality in young chicks (Roudybush and Grau, 1983).
Two ways to increase dry food intake would be to feed more frequently than every two hours or feed through the night until the level of solids can be increased.
The high peak weights of Trial 1 birds may have been due to overfeeding. When crops are overfilled, birds sometimes regurgitate. Chicks from Trial 1 after about 3 weeks of age would often regurgitate food; other times they would attempt to regurgitate unsuccessfully. Because less food was fed per meal, weight overshoot and regurgitation did not occur in Trial 2.
Growth rates may differ due to feed intake variations even if groups of chicks are fed the same diet. This was demonstrated by the fluctuations in rapid growth rate shown in Trial 2. These birds were fed by 2 people, feeding different amounts, in contrast to birds in Trial 1 which were fed by a single person. The growth curve for Trial 1 birds showed a smoother slope during the period of rapid growth than the growth curve for Trial 2 birds (Fig. 3)
Although birds from Trial 4 grew very slowly for 9 days, growth was increased by increasing meal size. Trial 4 chick body weights eventually met those of the parent-fed birds. This indicates that slow initial growth, if recognized and corrected, does not necessarily affect body weights at 35 days of age. | 
