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Some Responses of Laying Hens to Induced Arrest of Egg Production1
Some Responses of Laying Hens to Induced Arrest of Egg Productionl S. HURWITZ, S. BORNSTEIN AND Y . LEV Institute of Animal Science, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel (Received for publication June 18, 1974)
POULTRY SCIENCE 54: 415-422, 1975
T
HE onset or arrest of egg production is associated with major disturbances in the homeostatically controlled metabolism of the chicken, brought about by introducing abrupt changes in its protein, energy and mineral needs. The adjustment to the new metabolic state may require some time, during which the animal may be in negative or positive balance of various nutrients. In previous reports (Hurwitz and Bar, 1971; Hurwitz et al., 1971) we described the responses of pullets to the onset of egg production in terms of feed consumption, body weight, egg production, egg weight, shell weight and bone composition. Since these studies were conducted during the natural onset of egg production, the noted responses could not be attributed with certainty to the onset of egg production; they might have been confounded with the age-related processes of maturation. In the present study, several responses of hens to artificially induced arrest of egg
production were studied in an effort to isolate regulatory responses specifically caused by the process of egg formation. Arrest of egg production was achieved either by conventional artificial-molting procedures (starvation, cessation of illumination, etc.), by supplying a low-calcium diet (Douglas et al., 1972; Gilbert, 1973), or by feeding Nicarbazin2 (Hurwitz, 1965). The work also offers a comparison of practical methods for induction of a pause in egg laying. METHODS Trial 1. One hundred and ninety-two White Leghorn hens, 18 months old, with an egg production rate of over 50%, were assigned to this trial. They received a standard layer diet containing 16% protein and 2800 Cal./kg. of metabolic energy. The hens were housed in individual laying cages situated in an open shed. Unless under specific treatment, artificial illumination was provided to extend daylight to 16 hours. The experiment was started on November 20, 1972, and lasted for 193 days.
1. Contribution from the Agricultural Research Organization, the Volcani Center, Bet Dagan, Israel. 1974 Series, No. 141-E. Supported by the Egg and Poultry Marketing Board of Israel.
415
2. 4,4-dinitro-carbanilide-2-hydroxy-4,6 pyrimdine.
methyl-
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on June 22, 2015
ABSTRACT Arrest of egg production was induced by forced-molt (artificial light deprivation and feed deprivation for 10 days followed by 20 days of grain only) and by low-calcium regime in one experiment, and by Nicarbazin in another. Post-arrest production and shell quality significantly surpassed the control in the force-molt but not in the low-Ca treatment. At the onset of production, following the pause, egg weight and shell weight per unit of surface area rapidly increased up to the 9-10th egg. In the second trial, feed intake declined in about one week after the arrest in egg production to a non-layer level. During this week, body weight increased. However, despite the increase in feed intake after the onset of production, pre-arrest levels were not obtained even after 11 days, resulting in a loss of body weight. The separation of flock production into its components, rate of production of the layers, and the proportion of layers in the flock, is proposed.
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S . HURWITZ, S . BORNSTEIN AND Y . LEV
TABLE 1.—Body weight of hens before and after an induced arrest of egg production' Days of experiment 0 30
— 100 137 174 191
Control
Start of treatment End of treatment First egg Laying Laying Laying Laying
2060 ± 33 2 2085 ± 33a 3
— 2165 2157 2231 2161
± ± ± ±
30a 35a 39a 41a
Low-Ca 2060 1919 1961 2215 2252 2359 2233
± ± ± ± ± ± ±
31 52b 28 26b 23b 29b 47b
Force-molt 2102 1531 1977 2133 2196 2315 2235
± ± ± ± ± ± ±
66 33c 27 29a 26ab 26b 27b
treatments, see text.
Means designated by a different letter are significantly (P < 0.05) different within each stage.
The hens were assigned to three treatment lots, each including eight replicate groups of eight hens. Lot 1 was kept as control, and received no treatment. Lot 2 received a diet similar to the control but with no limestone supplement: it contained 0.3% calcium provided mostly by dicalcium phosphate, and was fed for 30 days. In lot 3, molt was induced by discontinuing artificial illumination and by a 10-day fast followed by 20 days of feeding of grain only. At the end of one month of treatment, all hens were returned to the standard diet and lighting conditions. Body weight was measured at the start of the experiment, at the end of the treatments, and four more times, as shown in Table 1. Moreover, in the treatment lots, individual weights were also recorded after each hen had layed her first egg following the treatment. Feed intake was recorded at monthly intervals starting at 70 days after the start of the trial. Egg production was recorded daily for each hen. Production rate was calculated for quarter-month intervals (7-8 days). Any hen which had not produced during such an interval was defined as a non-layer for the respective period. Using this definition the following were calculated for each period and replicate group:
Overall rate of egg production = 100 x (Total eggs layed /Total hens x days) Rate of egg production of layers = 100 x (Total eggs layed/No. layers x days) Percentage of layers = 100 x (No. of layers/No. of total hens) Egg weights and shell weights were obtained from egg collections made during four consecutive days before the start of the experiment, and at monthly intervals during the last four months of the trial. In addition, the first nine eggs layed by treated hens upon the onset of egg production, were collected and weighed. Shell weight was obtained for the first, third and ninth eggs. Egg surface area was calculated by the equation of Mueller and Scott (1940) and used to calculate the shell weight per unit of surface area, as a measure of shell quality. Trial 2. The purpose of this trial was to determine the rate of response of feed intake and body weight to arrest and onset of egg production. Twenty-five hens, all in good production, were fed a standard layer diet containing 0.04% Nicarbazin. Feed intake was measured daily on an individual basis. Body weight was recorded twice weekly. After 20 days, the diet was switched back
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1 For definition of 2 Mean ± SEM. 3
Treatment Stage
417
ARREST OF EGG PRODUCTION
Statistical Methods. Standard errors, analysis of variance and Duncan's multiple comparison test, were computed according to standard procedures (Snedecor and Cochran, 1968).
of the lot, however, was obtained only 4 weeks after the end of the treatment, due mainly to a corresponding rate of increase in the number of producers and the fact that hens which started to lay at the end of each period were defined as layers. From then on, the number of producers was maintained between 85 and 90%, but the production rate of the producers declined at a steady rate, resulting in a steady decline in the total egg production. It should be noted that peak production obtained by this lot was only slightly (P > 0.05) above that of the control, but later on the pattern of production was approximately parallel in both lots. In the conventionally force-molt birds production rate decreased to nil after two weeks of treatment. Total egg production, number of layers, and rate of production of the layers increased sharply to reach a peak five weeks
RESULTS Trial I. During treatment 6% of the hens of the low-Ca lot had to be eliminated due to severe osteoporosis. During that period there was no mortality in any of the other lots. Egg production parameters are shown in Fig. 1. Egg production started at about 60% with all hens in lay (due to the selection). In the control, total egg production declined steadily throughout the experimental period at a rate of 3-4% per month. This decline was in part due to a reduction in the number of layers in the flock, and in part to a decline in egg production by the layers. In the low-calcium lot, total egg production declined to about 5% in two weeks, with 25% of the group as producers laying at a rate of about 20%. A sharp increase in production, due both to increase in the number of producers and increased rate of production by the producers, followed immediately after the end of the treatment. Peak total production
20
40
60
80 DAYS
100 OF
120 140 EXPERIMENT
160
180
200
FIG. 1. Egg production in hens before, during and after arrest of egg production by a low-Ca diet • by force-molting (A) and by control hens in which no treatment was given (%): trial 1.
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to a standard diet not containing any Nicarbazin. All hens which had not stopped producing within eight days of treatment, and those which had not resumed their production within two weeks of the return to the normal diet, were eliminated from the experiment. The data then represent averages from nine birds. Body weight and feed intake were calculated by aligning all data to correspond to the last egg as if laid on a single day (day 8). This time scale was interrupted at day 28, and the data were realigned as if the first post-arrest egg of all hens had been laid on day 29. Days 8 and 29 were the average time interval for arrest and onset of egg production, respectively.
418
S . HURWITZ, S . BORNSTEIN AND Y . LEV
the force-molt birds. Here, however, body weight was much more depressed after the force-molt treatment as compared with the low-Ca treatment (P < 0.01). The magnitude of reduction in body weight by the treatment is too large to be accounted for by the weight of the reproductive system. At first egg and later on, the pattern was almost identical in both lots. All three lots showed a decline in body weight with the onset of higher temperatures in May. Feed intake (Table 2) of the control hens remained similar throughout the experiment except for a decline in the last month (with a rise in temperature during May). After return to peak production, feed intake was higher in both treatments but significantly
TABLE 2.—Feed consumption during the four final months of trial 1 after the treatment lots had reached peak egg production' Days of experiment
Control 113 119 113 104
73-100 101-131 132-161 162-193
± ± ± ±
3a 5a la la
Treatment Low-Ca g. /day /bird 123 ± 3b 125 ± 3ab 117 ± 4ab 115 ± 8b
Force-molt 128 ± 128 ± 121 ± 112 ±
lb lb 2b lb
'See footnotes, Table 1. TABLE 3.—Feed conversion during the four final months of trial I' Days of experiment 73-100 101-131 132-161 162-193
Control 200 ± 250 ± 243 ± 236 ±
11a 22a 14a 15a
Treatment Low-Ca g.feed/egg 216 227 256 231
± ± ± ±
11a 10a 25a 29a
Force-molt 164 ± 171 ± 180 ± 170 ±
6b 8b 5b 6b
'See footnotes, Table 1. TABLE 4.—Egg weight, trial I: initial weight and weight during the four final months of the trial' Treatment
Days of experiment -3-0 97-100 128-131 158-161 190-193
'See footnotes, Table 1.
Control 64.8 65.9 ± 67.4 ± 67.3 ± 68.5 ±
0.7 1.7 0.9 0.8
Low-Ca g65.4 68.6 + 68.5 ± 67.9 ± 67.0 ±
0.6 0.5 1.0 0.8
Force-molt 63.7 66.3 ± 66.0+ 66.5 ± 66.5 ±
1.0 1.3 0.6 1.0
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after the end of treatment. At this stage total egg production of this lot significantly exceeded (P < 0.01) that of the other two lots, due mainly to a higher production rate of the producers, although the number of layers was also slightly higher (P > 0.05) in this lot than in the others. Body weight (Table 1) increased slightly in the control lot during the experiment. The low-calcium hens lost some weight during the low-Ca treatment; their weight increased slightly at the time of laying the first egg, followed by an increase to weights higher than the initial weight and than the control (p < 0.05). These changes could be associated with the weight of the reproductive system. A similar pattern could also be observed for
419
ARREST OF EGG PRODUCTION
2
3
4
5 6 7 EGG NO.
8
9
FIG. 2. Egg weight of the first eggs laid after low-Ca ( | ) and force-molt (A) treatments; trial 1. (P < 0.05) only in the force molt one, compared with the control, with no significant difference between the former (P > 0.05). Feed conversion (Table 3) during the four final months was similarly poor for the control and the low-calcium treatment; it was significantly (P < 0.01) improved in the force-molt birds at any one period, reflecting the higher production of the latter. Egg weight (Table 4) increased gradually with time in the control lot. In both treatment lots egg weight increased considerably following treatment, but the differences between lots were not significant (P > 0.05). When
Trial 2. Results of this trial are presented in Figure 3 as "jumping" averages. During the Nicarbazin treatment egg production fluctuated with no particular tendency until it abruptly ceased. Following the pause, egg production immediately reached
TABLE 5.—Shell weight per unit of surface area, trial 1: initial weight and weight during the last months of the trial' Days of experiment -3-0 97-100 128-131 158-161 190-193
'See footnotes, Table 1.
Control
Treatment Low-Ca
Force-molt
73.6 71.0 ± 0.9a 72.4 ± 0.8a 70.2 ± 0.8a 69.7 ± 1.5a
mg./cm.2 72.1 74.8 ± 1.0b 74.1 ± 1.5a 73.1 ± 1.7a 72.4 ± 1.8a
74.3 79.5 ± 0.5c 78.5 ± 0.5c 76.7 ± 0.8b 75.2 ± 0.7b
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1
egg weights of the first nine post-treatment eggs are arranged in order of their lay, at onset of production (Fig. 2), a marked increase is apparent up to egg No. 8-10. The pattern of this increase is almost identical for both lots. Shell weight per unit of surface area (Table 5) somewhat declined in the control lot during the experiment. The low-Ca treatment caused a slight improvement in shell quality which was significant (P < 0.05) only during the first period. The relatively large variation (note standard error) of this lot is also of importance, indicating that in some birds shell quality was markedly improved by the treatment while it was markedly reduced in others. The force-molt treatment resulted in a marked improvement of shell quality to a very high level (P < 0.01). Shell quality remained considerably higher than that of the control even four months after treatment, in spite of the onset of warmer weather during May. Shell weight per unit of surface area at the onset of egg production (Table 6) increased from egg No. 1 to egg No. 9 in both lots: however, it was consistently better (P < 0.01) in the force-molt than in the high-Ca lot.
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S . HURWITZ, S . BORNSTElN AND Y . LEV
TABLE 6.—Shell weight per unit of surface following an induced pause in egg production (trial 1)
days prior to the onset of egg production feed intake declined to 81-82 g./day. Immediately following onset of production, feed intake started to increase but still failed to reach the pre-treatment level as late as 11 days later. This was accompanied by a marked reduction in body weight.
Treatment Low-Ca Force-molt mg./cm.2 75.1 75.5 75.3 79.5 81.5 83.0
Egg No. 1 3 9
DISCUSSION
i s
i -1 2
4
6
i 8
i
i
i
10 12 14
i i i i i i .J i i i i i i 16 18 20 22 24 26 28 30 32 36 36 38 40 DAYS OF EXPERIMENT
FIG. 3. Body weight, feed consumption and egg production of hens in which egg production had been arrested by Nicarbazin feeding (trial 2). Averages of 9 hens. For method of presentation, see text.
*
Also similar to the young pullet, the maximal egg production rate in the older hens is reached within one week following a pause in egg production (trial 2). As in the previous trial (Hurwitz and Bar, 1971), this effect can be observed only if the data are aligned according to the date of the first egg. Since
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Several traits observed in previous studies (Hurwitzand Bar, 1971; Hurwitz et al., 1971) for pullets at the onset of egg production have also been observed in old hens following an artificially induced pause in egg production. Remarkable is the decrease in feed consumption a few days prior to onset of production and the rather gradual increase in feed consumption (trial 2), following the onset of egg production. In the pullets of the previous study (Hurwitz etal., 1971), feed intake increased until it stabilized after one month of production. In the present study, feed intake was far from pre-arrest levels after 11 days. Another similarity lies in the pattern of egg weight. In both the pullets of the previous study and the old hens of this study (trial 1), egg weight increased rapidly up to egg No. 10, although its initial value was higher in the old birds than in the young birds (of the earlier study). Since the pattern was identical also for both treatment lots, it is suggested that such an increase is typical for onset of egg production. It may also be speculated that egg weight does not reach its maximum value immediately at the first egg, due to a negative energy balance which results from insufficient feed intake. Such a negative balance is manifested by a decline in body weight (trial 2).
a level similar to that preceding the pause. Feed consumption declined slightly at the start of the experiment; it stabilized at about 113 g./day before the last egg was laid. The arrest of egg production was immediately followed by a drop in feed consumption and some increase in body weight; however, it took about one week for feed intake to reach a low level of about 90-92 g./day. It continued to be low, with wide fluctuations. A few
421
ARREST OF EGG PRODUCTION
production before the end of the laying year is to improve these aspects of layer performance, and comparisons of methods must take into account primarily these parameters. As seen in Fig. 1, the force-molt birds reached a high level of production following treatment with shells of high quality. Despite the decline with time, good shell quality was sustained during the four months of full egg production. These results are in good agreement with those of Bell (1965) and Noles (1966), and point to an important economic potential of the force-molt procedure. On the other hand, the low-Ca treatment resulted in only a slight compensational response of egg production and shell quality, the former in agreement with the original results of Gilbert (1973), although the treatment was not as adverse as suggested by Nevelainen(1969). Furthermore, a considerable number of hens in the lowCa lot had to be eliminated due to severe osteoporosis. The previous workers (Douglas et al., 1972; Gilbert, 1973) emphasized that the method of low-calcium diets should not be used as a means of force-molting birds on a commerical scale, yet some popular poultry magazines have taken up this theme. These authors came to this conclusion, even without comparison with the conventional method of force-molting birds—to which many individuals and the laws of some countries object as basically cruel. The results of the present study together with the above quoted ones shed some doubt on the economic use of the low-Ca treatment for the control of egg production. REFERENCES Bell, D., 1965. Characteristics of force-molted flocks. Feedstuff s, 37 (17): 46-48. Douglas, C. R., R. H. Harms and H. R. Wilson, 1972. The use of extremely low dietary calcium to alter the production pattern of laying hens. Poultry Sci. 52 : 2015-2020. Gilbert, A. B., 1973. The use of calcium-restricted diet to control egg production in the domestic fowl. 4th Europ. Poultry Conf., London: 69-76.
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trial 1 was not analyzed in the same way, this is not readily observed. The increase in egg shell quality at the start of production (Fig. 2) was noted also for pullets of the previous study (Hurwitz and Bar, 1971). Again, the relatively low shell thickness at the start of production may be related to a negative calcium balance due, mainly to insufficient calcium intake. Thus, responses of production rate, feed intake, egg weight and shell quality noted in the previous study in young pullets may be related directly to metabolic changes induced by egg production per se. Regulation of feed intake is a complex process involving neural, endocrine and neuroendocrine action (Hervey, 1971). The chicken is unique in that its energy needs are changed abruptly at the onset or arrest of egg production. Thus, experiments with hens may indicate the response time to such changes. Results of trial 2 indicate that the response to such change is rapid, within one day. However, at least one week is required for the bird to move from one steady state to another. With conventional methods of representing egg production it is not possible to determine whether changes in flock production involve arrest of laying of some of the birds or a general change in the production rate of the layers in the flock. An attempt to make such a separation has been made in the present study (trial 1). It is of interest to note that in hens which had been selected as layers, egg production declined with age with little change in the relative number of layers. This analysis also shows that the force-molt treatment results in a true physiological response of all layers, since production rate of the layers was markedly improved by treatment. The main disadvantages of hens laying for periods longer than about six months is the decrease in rate of production and of shell quality with age. The purpose and justification of an artificially induced pause' in egg
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S. HURWITZ, S. B0RNSTE1N AND Y . LEV
Hervey, G. R., 1971. Physiological mechanisms for the regulation of energy balance. Proc. Nutr. Soc. 30: 109-116. Hurwitz, S., 1965. Calcium turnover in different bone segments of laying fowl. Am. J. Physiol. 208: 203-207. Hurwitz, S.,and A. Bar, 1971. The effect of pre-laying nutrition on the development, performance and mineral metabolism of pullets Poultry Sci. 50: 10441055. Hurwitz, S., S. Bornstein and Y. Lev, 1971. Some observations on the development of the pre-laying
pullet and young hen. Poultry Sci. 50: 1889-1890. Mueller, C. D., and H. M. Scott, 1940. The porosity of the egg-shell in relation to hatchability. Poultry Sci. 19: 163-166. Nevelainen, T. J., 1969. The effect of calcium-deficient diet on the reproductive organs of the hen. Poultry Sci. 48: 653-659. Noles, R. H., 1966. Subsequent production and egg quality of forced molted hens. Poultry Sci. 45: 50-57. Snedecor, G. W., and W. G. Cochran, 1968. Statistical Methods, 6th ed. Iowa State Univ. Press, Ames, Iowa.
B. L. R E I D AND C. W . WEBER
Poultry Science Department, University of Arizona, Tucson, Arizona 85721 (Received for publication June 25, 1974).
ABSTRACT Four dietary energy levels ranging from 2.64 to 3.08 kcal. M.E./g. were formulated with the supplements of 5, 10 and 15% added fat. These diets, containing 17.7% protein, were fed to laying hens under two housing conditions for a period of 280 days. Birds housed in an evaporatively cooled house exhibited a significant decrease in egg production rate with the feeding of 15% added fat (3.08 kcal. M.E./g.). Those housed in a conventional cage house did not show a significant change in egg production rate as a result of fat supplementation. Regression analyses indicated significant improvements in feed conversion for only the birds housed in the conventional cage houses. Feed intake was significantly reduced with increasing dietary energy under both conditions. Metabolizable energy consumptions were significantly increased with the feeding of higher levels of dietary fat. POULTRY SCIENCE 54: 422-428, 1975
INTRODUCTION T has been known for many years that an increase in the energy of poultry diets results in a decrease in feed intake provided other dietary nutrients are adequate. The use of added fat as a concentrated source of energy has thus been fashionable for many years. Jackson et al. (1969) fed diets with up to 28.25% added tallow at constant calorie: protein ratios. Feed conversion measured as kg. feed required per dozen eggs, decreased with increased dietary fat. However, the efficiency of metabolizable energy utilization decreased with added tallow. The average
I
Arizona Agricultural Experiment Station Journal Article 2333.
daily M.E. consumption of birds fed the high tallow diet was 354 kcal. in comparison with 250 kcal. for those fed a comparable diet without added fat with equivalent egg production and average egg weights. Studies by Kurnick et al. (1961) employed glucose monohydrate to provide productive energy levels of 2.12, 1.90 and 1.68 kcal./g. of diet. Under these conditions, at a constant dietary protein level of 17%, the calculated energy intakes were essentially the same at all dietary energy concentrations. Waring et al. (1968) have also reported that the feeding of substantial amounts of tallow improved feed efficiency, but that the efficiency of metabolizable energy utilization was decreased in hens fed the high tallow diets. Recently, Reid and Weber (1973) in
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Supplemental Dietary Fat and Laying Hen Performance
POULTRY SCIENCE 54: 415-422, 1975
T
HE onset or arrest of egg production is associated with major disturbances in the homeostatically controlled metabolism of the chicken, brought about by introducing abrupt changes in its protein, energy and mineral needs. The adjustment to the new metabolic state may require some time, during which the animal may be in negative or positive balance of various nutrients. In previous reports (Hurwitz and Bar, 1971; Hurwitz et al., 1971) we described the responses of pullets to the onset of egg production in terms of feed consumption, body weight, egg production, egg weight, shell weight and bone composition. Since these studies were conducted during the natural onset of egg production, the noted responses could not be attributed with certainty to the onset of egg production; they might have been confounded with the age-related processes of maturation. In the present study, several responses of hens to artificially induced arrest of egg
production were studied in an effort to isolate regulatory responses specifically caused by the process of egg formation. Arrest of egg production was achieved either by conventional artificial-molting procedures (starvation, cessation of illumination, etc.), by supplying a low-calcium diet (Douglas et al., 1972; Gilbert, 1973), or by feeding Nicarbazin2 (Hurwitz, 1965). The work also offers a comparison of practical methods for induction of a pause in egg laying. METHODS Trial 1. One hundred and ninety-two White Leghorn hens, 18 months old, with an egg production rate of over 50%, were assigned to this trial. They received a standard layer diet containing 16% protein and 2800 Cal./kg. of metabolic energy. The hens were housed in individual laying cages situated in an open shed. Unless under specific treatment, artificial illumination was provided to extend daylight to 16 hours. The experiment was started on November 20, 1972, and lasted for 193 days.
1. Contribution from the Agricultural Research Organization, the Volcani Center, Bet Dagan, Israel. 1974 Series, No. 141-E. Supported by the Egg and Poultry Marketing Board of Israel.
415
2. 4,4-dinitro-carbanilide-2-hydroxy-4,6 pyrimdine.
methyl-
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on June 22, 2015
ABSTRACT Arrest of egg production was induced by forced-molt (artificial light deprivation and feed deprivation for 10 days followed by 20 days of grain only) and by low-calcium regime in one experiment, and by Nicarbazin in another. Post-arrest production and shell quality significantly surpassed the control in the force-molt but not in the low-Ca treatment. At the onset of production, following the pause, egg weight and shell weight per unit of surface area rapidly increased up to the 9-10th egg. In the second trial, feed intake declined in about one week after the arrest in egg production to a non-layer level. During this week, body weight increased. However, despite the increase in feed intake after the onset of production, pre-arrest levels were not obtained even after 11 days, resulting in a loss of body weight. The separation of flock production into its components, rate of production of the layers, and the proportion of layers in the flock, is proposed.
416
S . HURWITZ, S . BORNSTEIN AND Y . LEV
TABLE 1.—Body weight of hens before and after an induced arrest of egg production' Days of experiment 0 30
— 100 137 174 191
Control
Start of treatment End of treatment First egg Laying Laying Laying Laying
2060 ± 33 2 2085 ± 33a 3
— 2165 2157 2231 2161
± ± ± ±
30a 35a 39a 41a
Low-Ca 2060 1919 1961 2215 2252 2359 2233
± ± ± ± ± ± ±
31 52b 28 26b 23b 29b 47b
Force-molt 2102 1531 1977 2133 2196 2315 2235
± ± ± ± ± ± ±
66 33c 27 29a 26ab 26b 27b
treatments, see text.
Means designated by a different letter are significantly (P < 0.05) different within each stage.
The hens were assigned to three treatment lots, each including eight replicate groups of eight hens. Lot 1 was kept as control, and received no treatment. Lot 2 received a diet similar to the control but with no limestone supplement: it contained 0.3% calcium provided mostly by dicalcium phosphate, and was fed for 30 days. In lot 3, molt was induced by discontinuing artificial illumination and by a 10-day fast followed by 20 days of feeding of grain only. At the end of one month of treatment, all hens were returned to the standard diet and lighting conditions. Body weight was measured at the start of the experiment, at the end of the treatments, and four more times, as shown in Table 1. Moreover, in the treatment lots, individual weights were also recorded after each hen had layed her first egg following the treatment. Feed intake was recorded at monthly intervals starting at 70 days after the start of the trial. Egg production was recorded daily for each hen. Production rate was calculated for quarter-month intervals (7-8 days). Any hen which had not produced during such an interval was defined as a non-layer for the respective period. Using this definition the following were calculated for each period and replicate group:
Overall rate of egg production = 100 x (Total eggs layed /Total hens x days) Rate of egg production of layers = 100 x (Total eggs layed/No. layers x days) Percentage of layers = 100 x (No. of layers/No. of total hens) Egg weights and shell weights were obtained from egg collections made during four consecutive days before the start of the experiment, and at monthly intervals during the last four months of the trial. In addition, the first nine eggs layed by treated hens upon the onset of egg production, were collected and weighed. Shell weight was obtained for the first, third and ninth eggs. Egg surface area was calculated by the equation of Mueller and Scott (1940) and used to calculate the shell weight per unit of surface area, as a measure of shell quality. Trial 2. The purpose of this trial was to determine the rate of response of feed intake and body weight to arrest and onset of egg production. Twenty-five hens, all in good production, were fed a standard layer diet containing 0.04% Nicarbazin. Feed intake was measured daily on an individual basis. Body weight was recorded twice weekly. After 20 days, the diet was switched back
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on June 22, 2015
1 For definition of 2 Mean ± SEM. 3
Treatment Stage
417
ARREST OF EGG PRODUCTION
Statistical Methods. Standard errors, analysis of variance and Duncan's multiple comparison test, were computed according to standard procedures (Snedecor and Cochran, 1968).
of the lot, however, was obtained only 4 weeks after the end of the treatment, due mainly to a corresponding rate of increase in the number of producers and the fact that hens which started to lay at the end of each period were defined as layers. From then on, the number of producers was maintained between 85 and 90%, but the production rate of the producers declined at a steady rate, resulting in a steady decline in the total egg production. It should be noted that peak production obtained by this lot was only slightly (P > 0.05) above that of the control, but later on the pattern of production was approximately parallel in both lots. In the conventionally force-molt birds production rate decreased to nil after two weeks of treatment. Total egg production, number of layers, and rate of production of the layers increased sharply to reach a peak five weeks
RESULTS Trial I. During treatment 6% of the hens of the low-Ca lot had to be eliminated due to severe osteoporosis. During that period there was no mortality in any of the other lots. Egg production parameters are shown in Fig. 1. Egg production started at about 60% with all hens in lay (due to the selection). In the control, total egg production declined steadily throughout the experimental period at a rate of 3-4% per month. This decline was in part due to a reduction in the number of layers in the flock, and in part to a decline in egg production by the layers. In the low-calcium lot, total egg production declined to about 5% in two weeks, with 25% of the group as producers laying at a rate of about 20%. A sharp increase in production, due both to increase in the number of producers and increased rate of production by the producers, followed immediately after the end of the treatment. Peak total production
20
40
60
80 DAYS
100 OF
120 140 EXPERIMENT
160
180
200
FIG. 1. Egg production in hens before, during and after arrest of egg production by a low-Ca diet • by force-molting (A) and by control hens in which no treatment was given (%): trial 1.
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to a standard diet not containing any Nicarbazin. All hens which had not stopped producing within eight days of treatment, and those which had not resumed their production within two weeks of the return to the normal diet, were eliminated from the experiment. The data then represent averages from nine birds. Body weight and feed intake were calculated by aligning all data to correspond to the last egg as if laid on a single day (day 8). This time scale was interrupted at day 28, and the data were realigned as if the first post-arrest egg of all hens had been laid on day 29. Days 8 and 29 were the average time interval for arrest and onset of egg production, respectively.
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S . HURWITZ, S . BORNSTEIN AND Y . LEV
the force-molt birds. Here, however, body weight was much more depressed after the force-molt treatment as compared with the low-Ca treatment (P < 0.01). The magnitude of reduction in body weight by the treatment is too large to be accounted for by the weight of the reproductive system. At first egg and later on, the pattern was almost identical in both lots. All three lots showed a decline in body weight with the onset of higher temperatures in May. Feed intake (Table 2) of the control hens remained similar throughout the experiment except for a decline in the last month (with a rise in temperature during May). After return to peak production, feed intake was higher in both treatments but significantly
TABLE 2.—Feed consumption during the four final months of trial 1 after the treatment lots had reached peak egg production' Days of experiment
Control 113 119 113 104
73-100 101-131 132-161 162-193
± ± ± ±
3a 5a la la
Treatment Low-Ca g. /day /bird 123 ± 3b 125 ± 3ab 117 ± 4ab 115 ± 8b
Force-molt 128 ± 128 ± 121 ± 112 ±
lb lb 2b lb
'See footnotes, Table 1. TABLE 3.—Feed conversion during the four final months of trial I' Days of experiment 73-100 101-131 132-161 162-193
Control 200 ± 250 ± 243 ± 236 ±
11a 22a 14a 15a
Treatment Low-Ca g.feed/egg 216 227 256 231
± ± ± ±
11a 10a 25a 29a
Force-molt 164 ± 171 ± 180 ± 170 ±
6b 8b 5b 6b
'See footnotes, Table 1. TABLE 4.—Egg weight, trial I: initial weight and weight during the four final months of the trial' Treatment
Days of experiment -3-0 97-100 128-131 158-161 190-193
'See footnotes, Table 1.
Control 64.8 65.9 ± 67.4 ± 67.3 ± 68.5 ±
0.7 1.7 0.9 0.8
Low-Ca g65.4 68.6 + 68.5 ± 67.9 ± 67.0 ±
0.6 0.5 1.0 0.8
Force-molt 63.7 66.3 ± 66.0+ 66.5 ± 66.5 ±
1.0 1.3 0.6 1.0
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after the end of treatment. At this stage total egg production of this lot significantly exceeded (P < 0.01) that of the other two lots, due mainly to a higher production rate of the producers, although the number of layers was also slightly higher (P > 0.05) in this lot than in the others. Body weight (Table 1) increased slightly in the control lot during the experiment. The low-calcium hens lost some weight during the low-Ca treatment; their weight increased slightly at the time of laying the first egg, followed by an increase to weights higher than the initial weight and than the control (p < 0.05). These changes could be associated with the weight of the reproductive system. A similar pattern could also be observed for
419
ARREST OF EGG PRODUCTION
2
3
4
5 6 7 EGG NO.
8
9
FIG. 2. Egg weight of the first eggs laid after low-Ca ( | ) and force-molt (A) treatments; trial 1. (P < 0.05) only in the force molt one, compared with the control, with no significant difference between the former (P > 0.05). Feed conversion (Table 3) during the four final months was similarly poor for the control and the low-calcium treatment; it was significantly (P < 0.01) improved in the force-molt birds at any one period, reflecting the higher production of the latter. Egg weight (Table 4) increased gradually with time in the control lot. In both treatment lots egg weight increased considerably following treatment, but the differences between lots were not significant (P > 0.05). When
Trial 2. Results of this trial are presented in Figure 3 as "jumping" averages. During the Nicarbazin treatment egg production fluctuated with no particular tendency until it abruptly ceased. Following the pause, egg production immediately reached
TABLE 5.—Shell weight per unit of surface area, trial 1: initial weight and weight during the last months of the trial' Days of experiment -3-0 97-100 128-131 158-161 190-193
'See footnotes, Table 1.
Control
Treatment Low-Ca
Force-molt
73.6 71.0 ± 0.9a 72.4 ± 0.8a 70.2 ± 0.8a 69.7 ± 1.5a
mg./cm.2 72.1 74.8 ± 1.0b 74.1 ± 1.5a 73.1 ± 1.7a 72.4 ± 1.8a
74.3 79.5 ± 0.5c 78.5 ± 0.5c 76.7 ± 0.8b 75.2 ± 0.7b
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1
egg weights of the first nine post-treatment eggs are arranged in order of their lay, at onset of production (Fig. 2), a marked increase is apparent up to egg No. 8-10. The pattern of this increase is almost identical for both lots. Shell weight per unit of surface area (Table 5) somewhat declined in the control lot during the experiment. The low-Ca treatment caused a slight improvement in shell quality which was significant (P < 0.05) only during the first period. The relatively large variation (note standard error) of this lot is also of importance, indicating that in some birds shell quality was markedly improved by the treatment while it was markedly reduced in others. The force-molt treatment resulted in a marked improvement of shell quality to a very high level (P < 0.01). Shell quality remained considerably higher than that of the control even four months after treatment, in spite of the onset of warmer weather during May. Shell weight per unit of surface area at the onset of egg production (Table 6) increased from egg No. 1 to egg No. 9 in both lots: however, it was consistently better (P < 0.01) in the force-molt than in the high-Ca lot.
420
S . HURWITZ, S . BORNSTElN AND Y . LEV
TABLE 6.—Shell weight per unit of surface following an induced pause in egg production (trial 1)
days prior to the onset of egg production feed intake declined to 81-82 g./day. Immediately following onset of production, feed intake started to increase but still failed to reach the pre-treatment level as late as 11 days later. This was accompanied by a marked reduction in body weight.
Treatment Low-Ca Force-molt mg./cm.2 75.1 75.5 75.3 79.5 81.5 83.0
Egg No. 1 3 9
DISCUSSION
i s
i -1 2
4
6
i 8
i
i
i
10 12 14
i i i i i i .J i i i i i i 16 18 20 22 24 26 28 30 32 36 36 38 40 DAYS OF EXPERIMENT
FIG. 3. Body weight, feed consumption and egg production of hens in which egg production had been arrested by Nicarbazin feeding (trial 2). Averages of 9 hens. For method of presentation, see text.
*
Also similar to the young pullet, the maximal egg production rate in the older hens is reached within one week following a pause in egg production (trial 2). As in the previous trial (Hurwitz and Bar, 1971), this effect can be observed only if the data are aligned according to the date of the first egg. Since
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Several traits observed in previous studies (Hurwitzand Bar, 1971; Hurwitz et al., 1971) for pullets at the onset of egg production have also been observed in old hens following an artificially induced pause in egg production. Remarkable is the decrease in feed consumption a few days prior to onset of production and the rather gradual increase in feed consumption (trial 2), following the onset of egg production. In the pullets of the previous study (Hurwitz etal., 1971), feed intake increased until it stabilized after one month of production. In the present study, feed intake was far from pre-arrest levels after 11 days. Another similarity lies in the pattern of egg weight. In both the pullets of the previous study and the old hens of this study (trial 1), egg weight increased rapidly up to egg No. 10, although its initial value was higher in the old birds than in the young birds (of the earlier study). Since the pattern was identical also for both treatment lots, it is suggested that such an increase is typical for onset of egg production. It may also be speculated that egg weight does not reach its maximum value immediately at the first egg, due to a negative energy balance which results from insufficient feed intake. Such a negative balance is manifested by a decline in body weight (trial 2).
a level similar to that preceding the pause. Feed consumption declined slightly at the start of the experiment; it stabilized at about 113 g./day before the last egg was laid. The arrest of egg production was immediately followed by a drop in feed consumption and some increase in body weight; however, it took about one week for feed intake to reach a low level of about 90-92 g./day. It continued to be low, with wide fluctuations. A few
421
ARREST OF EGG PRODUCTION
production before the end of the laying year is to improve these aspects of layer performance, and comparisons of methods must take into account primarily these parameters. As seen in Fig. 1, the force-molt birds reached a high level of production following treatment with shells of high quality. Despite the decline with time, good shell quality was sustained during the four months of full egg production. These results are in good agreement with those of Bell (1965) and Noles (1966), and point to an important economic potential of the force-molt procedure. On the other hand, the low-Ca treatment resulted in only a slight compensational response of egg production and shell quality, the former in agreement with the original results of Gilbert (1973), although the treatment was not as adverse as suggested by Nevelainen(1969). Furthermore, a considerable number of hens in the lowCa lot had to be eliminated due to severe osteoporosis. The previous workers (Douglas et al., 1972; Gilbert, 1973) emphasized that the method of low-calcium diets should not be used as a means of force-molting birds on a commerical scale, yet some popular poultry magazines have taken up this theme. These authors came to this conclusion, even without comparison with the conventional method of force-molting birds—to which many individuals and the laws of some countries object as basically cruel. The results of the present study together with the above quoted ones shed some doubt on the economic use of the low-Ca treatment for the control of egg production. REFERENCES Bell, D., 1965. Characteristics of force-molted flocks. Feedstuff s, 37 (17): 46-48. Douglas, C. R., R. H. Harms and H. R. Wilson, 1972. The use of extremely low dietary calcium to alter the production pattern of laying hens. Poultry Sci. 52 : 2015-2020. Gilbert, A. B., 1973. The use of calcium-restricted diet to control egg production in the domestic fowl. 4th Europ. Poultry Conf., London: 69-76.
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trial 1 was not analyzed in the same way, this is not readily observed. The increase in egg shell quality at the start of production (Fig. 2) was noted also for pullets of the previous study (Hurwitz and Bar, 1971). Again, the relatively low shell thickness at the start of production may be related to a negative calcium balance due, mainly to insufficient calcium intake. Thus, responses of production rate, feed intake, egg weight and shell quality noted in the previous study in young pullets may be related directly to metabolic changes induced by egg production per se. Regulation of feed intake is a complex process involving neural, endocrine and neuroendocrine action (Hervey, 1971). The chicken is unique in that its energy needs are changed abruptly at the onset or arrest of egg production. Thus, experiments with hens may indicate the response time to such changes. Results of trial 2 indicate that the response to such change is rapid, within one day. However, at least one week is required for the bird to move from one steady state to another. With conventional methods of representing egg production it is not possible to determine whether changes in flock production involve arrest of laying of some of the birds or a general change in the production rate of the layers in the flock. An attempt to make such a separation has been made in the present study (trial 1). It is of interest to note that in hens which had been selected as layers, egg production declined with age with little change in the relative number of layers. This analysis also shows that the force-molt treatment results in a true physiological response of all layers, since production rate of the layers was markedly improved by treatment. The main disadvantages of hens laying for periods longer than about six months is the decrease in rate of production and of shell quality with age. The purpose and justification of an artificially induced pause' in egg
422
S. HURWITZ, S. B0RNSTE1N AND Y . LEV
Hervey, G. R., 1971. Physiological mechanisms for the regulation of energy balance. Proc. Nutr. Soc. 30: 109-116. Hurwitz, S., 1965. Calcium turnover in different bone segments of laying fowl. Am. J. Physiol. 208: 203-207. Hurwitz, S.,and A. Bar, 1971. The effect of pre-laying nutrition on the development, performance and mineral metabolism of pullets Poultry Sci. 50: 10441055. Hurwitz, S., S. Bornstein and Y. Lev, 1971. Some observations on the development of the pre-laying
pullet and young hen. Poultry Sci. 50: 1889-1890. Mueller, C. D., and H. M. Scott, 1940. The porosity of the egg-shell in relation to hatchability. Poultry Sci. 19: 163-166. Nevelainen, T. J., 1969. The effect of calcium-deficient diet on the reproductive organs of the hen. Poultry Sci. 48: 653-659. Noles, R. H., 1966. Subsequent production and egg quality of forced molted hens. Poultry Sci. 45: 50-57. Snedecor, G. W., and W. G. Cochran, 1968. Statistical Methods, 6th ed. Iowa State Univ. Press, Ames, Iowa.
B. L. R E I D AND C. W . WEBER
Poultry Science Department, University of Arizona, Tucson, Arizona 85721 (Received for publication June 25, 1974).
ABSTRACT Four dietary energy levels ranging from 2.64 to 3.08 kcal. M.E./g. were formulated with the supplements of 5, 10 and 15% added fat. These diets, containing 17.7% protein, were fed to laying hens under two housing conditions for a period of 280 days. Birds housed in an evaporatively cooled house exhibited a significant decrease in egg production rate with the feeding of 15% added fat (3.08 kcal. M.E./g.). Those housed in a conventional cage house did not show a significant change in egg production rate as a result of fat supplementation. Regression analyses indicated significant improvements in feed conversion for only the birds housed in the conventional cage houses. Feed intake was significantly reduced with increasing dietary energy under both conditions. Metabolizable energy consumptions were significantly increased with the feeding of higher levels of dietary fat. POULTRY SCIENCE 54: 422-428, 1975
INTRODUCTION T has been known for many years that an increase in the energy of poultry diets results in a decrease in feed intake provided other dietary nutrients are adequate. The use of added fat as a concentrated source of energy has thus been fashionable for many years. Jackson et al. (1969) fed diets with up to 28.25% added tallow at constant calorie: protein ratios. Feed conversion measured as kg. feed required per dozen eggs, decreased with increased dietary fat. However, the efficiency of metabolizable energy utilization decreased with added tallow. The average
I
Arizona Agricultural Experiment Station Journal Article 2333.
daily M.E. consumption of birds fed the high tallow diet was 354 kcal. in comparison with 250 kcal. for those fed a comparable diet without added fat with equivalent egg production and average egg weights. Studies by Kurnick et al. (1961) employed glucose monohydrate to provide productive energy levels of 2.12, 1.90 and 1.68 kcal./g. of diet. Under these conditions, at a constant dietary protein level of 17%, the calculated energy intakes were essentially the same at all dietary energy concentrations. Waring et al. (1968) have also reported that the feeding of substantial amounts of tallow improved feed efficiency, but that the efficiency of metabolizable energy utilization was decreased in hens fed the high tallow diets. Recently, Reid and Weber (1973) in
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Supplemental Dietary Fat and Laying Hen Performance