RESPONSE OF LAYERS TO LOW NUTRIENT DENSITY DIETS

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1 2001 Poultry Science Association, Inc. RESPONSE OF LAYERS TO LOW NUTRIENT DENSITY DIETS S. LEESON 1, J. D. SUMMERS, and L. J. CASTON Department of Animal & Poultry Science University of Guelph, Guelph, ON Canada N1G 2W1 Phone: (519) Ext FAX: (519) Primary Audience: Nutritionists, Layer Managers SUMMARY Two experiments were conducted to test the ability of layers to increase their feed intake when fed diets of reduced nutrient density. Shaver White layers at 19 wk of age were fed diets at 2900 kcal ME/kg and 18.2% crude protein, or 5, 10, or 15% reduced nutrient density. In Experiment 1 reduced nutrient density was achieved by adding a non-nutritive filler. In the same nutrient profiles were achieved by substitution of wheat, barley, and wheat bran for corn and fat. In, diet had no effect on egg production, egg size, or body weight since layers adequately adjusted their feed intake to normalize energy intake. Birds were less successful in adjusting feed intake in, and reasons for this are discussed. It is assumed that as long as nutrient balance is maintained in low nutrient density diets, diet equivalents even as low as 2465 kcal ME/kg and 15.2% CP are adequate to support full-cycle production. Key words: Energy, layer, nutrient density DESCRIPTION OF PROBLEM It is generally assumed that laying hens eat to their energy requirement, meaning that birds will eat less of a high-energy diet and vice versa. Morris [1] indicated that such adjustment to feed intake was not perfect and that layers tend to over-consume energy when fed high-energy diets and vice versa. Thus, if nutrients are tied to energy and diets formulated according to feed intake, proportionally less nutrients should be included in higher energy diets, while low-energy diets may need slightly greater fortification. The situation described by Morris [1] is perhaps of only academic interest today, because he showed that the proportional changes to energy 2001 J. Appl. Poultry Res. 10:46 52 consumption in response to change in diet energy were most pronounced for birds with inherently high energy intake. For example, birds offered a diet of 2,400 vs. 3,200 kcal ME/kg exhibited a 15% reduction in energy intake when normal intake was around 450 kcal/kg. For birds normally eating 280 kcal/day, as is now more common, the decline in daily intake was only 1.7% when the diet of 2,400 vs. 3,200 kcal ME/ kg was allowed. Birds with low body weight, and low inherent feed intake therefore seem to adjust feed intake quite efficiently in response to changing diet nutrient density. There have been few reports on the response of modern strains of layer to varying nutrient density. In many countries high-energy diets are 1 To whom correspondence should be addressed

2 LEESON ET AL.: LAYER NUTRIENT DENSITY 47 not always economical to produce, because of scarcity of high-energy ingredients such as corn and fat. In other situations, even though such ingredients are available, cost per unit of energy may be lower from alternative sources, making low-energy diets more attractive. Today researchers often question the physical ability of modern layer strains to eat more feed when offered such low nutrient-density diets. This problem will be most acute for younger birds because of their low inherent feed intake and the fact that up to the time of peak egg numbers, the bird s feed intake adjustment in response to diet energy is less accurate [2]. There is surprisingly little information available on the response of current layer strains to such varying nutrient density. Often such bird response involves change in only diet energy [3], so feed intake changes could be confounded with variable intake of other nutrients such as amino acids. Birds will increase their feed intake in response to marginal levels of first limiting amino acids, independent of diet energy level [4]. A more logical and practical approach is to study bird response to variable diet nutrient density where all nutrients are changed either by simple diet dilution or by reformulation. Diet dilution, while of less commercial relevance, has the advantage of not changing the balance of any nutrients and thus assuring there will be no confounding factors. Reformulation to achieve low nutrient density diets involves variable ingredient composition, so it is impossible to achieve absolute control on the balance of all nutrients. However, both approaches have been used with layers and other birds, and results are not always similar. Cherry et al. [5] showed a variable response of layers when sand or cellulose were used as diluents. Such effects were ascribed to changes in physical density of the diet, and inability of birds to eat enough of the bulky low-energy diet. A mixture of sand and cellulose causes little change in bulk density of feed [5], and this seems the most appropriate diluent for such studies. In the present study, two experiments were conducted with layers wk of age fed diets with 5, 10, or 15% less nutrients per kilogram of diet, achieved by either diet dilution () or reformulation (). MATERIALS AND METHODS used wk-old Shaver White pullets housed in individual cages in a room with environmental control, maintained at 20 C and an imposed photoperiod of 15 hr light/ 9 hr dark. Four experimental mash diets were prepared. Diet 1 was fed as a control standard laying hen diet and the other three diets (2, 4, and 6) were diluted by 5, 10, and 15% respectively, using a 50:50 mix of sand (200µ) and alphafloc cellulose (Table 1). Each diet was fed to eight replicate groups of 4 birds each. Diets were fed through a full laying cycle of twelve, 28-day periods and hen performance characteristics were recorded. There was no visible feed separation, and no sand accumulated in the feed troughs. Egg production was monitored on a daily basis throughout the trial. All eggs were collected at the end (the last two days) of Periods 2, 4, 6, 8, 10, and 12 for measurements of egg weight, egg shell deformation, and, in Periods 6 and 12, albumen height. Feed intake was measured at the end of Periods 2, 4, 6, 8, 10, and 12 and calculated as grams of feed per bird per day. Individual hen body weight was measured initially (19 wk) and at 31, 47, and 61 wk of age. In the set-up and execution were exactly the same as in, using pullets from the same flock. The diet treatment classification for this experiment was based on a percentage reduced nutrient density profile as presented in Table 1. Treatment 1 was the same diet (Diet 1) fed as a control in. Treatments 2, 3, and 4 (Diets 3, 5, and 7) were formulated to provide 5, 10, and 15% reduced nutrient density compared to the control diet. Feed and water were available ad libitum throughout both experiments. STATISTICAL ANALYSIS Each experiment was a completely randomized design and the experimental unit was pen, defined as 4 birds in adjacent cages fed as a unit. A one-way analysis of variance procedure was carried out on all data both collected and calculated. The treatment classification variable was considered to be level of diet dilution or diet nutrient density. Data collected as body weight, feed intake, egg production, egg weight, eggshell deformation, and albumen height were ana-

3 48 JAPR: Research Report TABLE 1. Percentage of diet composition DIET # Wheat Barley Corn Soybean meal (47%) Meat meal (50%) Sand/Alphafloc Wheat bran Limestone Dicalcium PO Animal-vegetable fat Salt DL-Methionine L-Lysine Vitamin-mineral premix Calculated analyses: CP (%) ME (kcal/kg) Ca (%) Av. P (%) Na (%) Methionine (%) Meth + Cys (%) Lysine (%) Tryptophan (%) Analyzed: CP (%) Ca (%) Provided per kg of diet: vitamin A, 8,800 IU; vitamin D 3, 3,300 IU; vitamin E, 40 IU; vitamin K 3, 3.3 mg; thiamine, 4.0 mg; riboflavin, 8.0 mg; pantothenic acid, 15 mg; niaicn, 50 mg; pyridoxine, 3.3 mg; choline, 600 mg; folic acid, 1 mg; biotin, 220 µg; vitamin B 12,12µg; ethoxyquin, 120 mg; manganese, 70 mg; zinc, 70 mg; iron, 60 mg; copper, 10 mg; iodine, 1.0 mg; selenium, 0.3 mg. lyzed. Summary data calculated in terms of total egg numbers, total egg mass, total feed intake, total energy intake, overall feed efficiency, and overall energy efficiency were also analyzed. Means of these response variables that resulted in a significant F-test were further considered using Tukey s test. Significance was accepted as P < RESULTS AND DISCUSSION Feed intake of layers fed the various diets is shown in Table 2. As expected, as the nutrient density of the feed declined, the birds ate more feed. For birds fed the diets diluted with the non-nutritive filler (), adjustment to feed intake was gradual and not really established until 43 wk of age. No explanation is available at this time for the constant feed intake across treatments seen at 35 wk (Table 2). From 43 to 65 wk, feed intake adjustment mirrored fairly closely the degree of diet dilution. In Experiment 2, where low nutrient density was achieved by reformulation, the adjustment to feed intake was more dramatic and more quickly established (Table 2). With these treatments (Experiment 2) birds tended to over-consume feed relative to predicted nutrient density. For example, at 35 wk birds fed the diet formulated to 15% in nutrient density ate 38% more feed than did control birds. At 65 wk these same birds were eating 31% more than the control-fed birds. In, body weight was little affected by diet treatment (Table 3), although there is a consistent trend over time for birds to weigh less as the nutrient density of the diet is reduced.

4 LEESON ET AL.: LAYER NUTRIENT DENSITY 49 TABLE 2. Feed intake of layers fed diluted diets () or diets formulated to low nutrient density (Experiment 2) FEED INTAKE (g/bird/day) 35 wk 43 wk 51 wk 59 wk 65 wk 1. Control b 103 bc 97 b 103 b 2. 5% dilution b 103 bc 97 b 103 b 3. 10% dilution a 113 a 112 a 109 ab 4. 15% dilution a 111 ab 116 a 115 a ± SD Significance NS ** ** ** ** 1. Control 94 c 99 c 99 b 96 b 97 c 2. 5% lower density 105 bc 109 bc 106 b 103 b 105 bc 3. 10% lower density 116 ab 120 ab 121 a 123 a 117 ab 4. 15% lower density 130 a 131 a 123 a 123 a 127 a ± SD Significance ** ** ** ** ** a,b,c Means within columns with no common superscripts are significantly different, NS = non-significant (P > 0.05); ** = significant (P < 0.01). The same situation occurred in, although in this situation significant differences were seen after 31 wk of age (Table 3). Egg production was little affected by diet dilution using either method of diet preparation (Table 4), and in general production levels met or exceeded standards for the Shaver White bird. In there was a trend for birds fed the lowest nutrient density diet to produce the fewest eggs, and this effect was significant (P < 0.01) at 35 wk of age. Egg weight data are shown in Table 5. As nutrient density declined, there was a trend for reduced egg size, but the effects were quite small and significant (P < 0.05) only at isolated measurement times. As a generalization, it seems as though the diet dilution or reduced nutrient density causes a loss in egg size of 1 2 g, and most of this occurs at the TABLE 3. Body weight of layers fed diluted diets () or diets formulated to low nutrient density () BODY WEIGHT (g) 19 wk 31 wk 47 wk 61 wk 1. Control % dilution % dilution % dilution ± SD Significance NS NS NS NS 1. Control a 1622 a 1766 a 2. 5% lower density a 1657 a 1758 a 3. 10% lower density a 1561 ab 1692 ab 4. 15% lower density b 1503 b 1636 a ± SD Significance NS ** ** ** a,b,c Means within columns with no common superscripts are significantly different, NS = non-significant (P > 0.05); * = significant (P < 0.05); ** = significant (P < 0.01).

5 50 JAPR: Research Report TABLE 4. Egg production of layers fed diluted diets () or diets formulated to low nutrient density () EGG PRODUCTION (%) 27 wk 35 wk 43 wk 51 wk 67 wk 1. Control % dilution % dilution % dilution ± SD Significance NS NS NS NS NS 1. Control a % lower density a % lower density ab % lower density b ± SD Significance NS ** NS NS NS a,b Means within columns with no common superscripts are significantly different, NS = non-significant (P > 0.05); ** = significant (P < 0.01). lowest level of dilution. Egg shell deformation, as a measure of shell quality, and albumen height were measured at the same time as egg weights. There were no treatment differences (P > 0.05) for any of these egg quality parameters related to diet treatment, and data are not shown. Table 6 summarizes production data from 19 to 67 wk of age. Egg number was not affected by diet treatment, and even with 15% dilution in, birds still produced over 300 eggs. There was an indication of lower egg numbers for birds fed the diet formulated to 5% diet dilution, although these numbers were not different (P > 0.05) from those seen with other birds in this trial. Total egg mass was similar for most birds in (Table 6), although birds fed a diet diluted to 5% produced less mass than did birds fed the control or 10% TABLE 5. Egg weight of layers fed diluted diets () or diets formulated to low nutrient density (Experiment 2) EGG WEIGHT (g) 27 wk 35 wk 43 wk 51 wk 65 wk 1. Control a % dilution b % dilution ab % dilution b 62 ± SD Significance NS NS NS * NS 1. Control a % lower density ab % lower density b % lower density b ± SD Significance NS ** NS NS NS a,b Means within columns with no common superscripts are significantly different, NS = non-signficant (P > 0.05); * = significant (P < 0.05); ** = significant (P < 0.01).

6 LEESON ET AL.: LAYER NUTRIENT DENSITY 51 TABLE 6. Overall performance of layers at wk when fed diluted diets () or diets formulated to low nutrient density () TOTAL EGG TOTAL FEED EFFICIENCY Feed Energy kg Mass intake intake Feed/kg Mcal/kg Number (kg) (kg) (Mcal) egg Egg 1. Control a 33.9 b b % dilution b 34.3 b a % dilution a 37.1 a a % dilution ab 37.1 a a 5.3 ± SD Significance NS ** ** NS ** NS 1. Control a 32.4 b 94.0 b 1.89 c 5.4 b 2. 5% lower density a 35.4 b 97.8 ab 2.02 bc 5.6 b 3. 10% lower density a 39.9 a a 2.29 b 5.9 b 4. 15% lower density b 42.6 a a 2.80 a 6.8 a ± SD Significance NS * ** ** ** ** a,b,c Means within columns with no common superscripts are significantly different, NS = non-significant (P > 0.05); * = significant (P < 0.05); ** = significant (P < 0.01). diluted diet. Birds fed the 15% diluted diet produced an intermediate egg mass not different from that of all other birds. In, the diet with 15% reduced density resulted in a significant (P < 0.05) reduction in egg mass, and all other birds produced at the same level. In both experiments, as diet nutrient density declined, birds ate more feed, and this effect was significant for birds fed 10 or 15% reduced density vs. 5% reduced density or the control diet (P < 0.01). Because of changing diet energy level, diet dilution in resulted in no change (P > 0.05) in energy intake over the wk period. In, use of lower nutrient-density diets in fact resulted in an increase (P < 0.01) in energy intake. Classical feed efficiency was always optimum for the control birds, and as nutrient density declined, efficiency deteriorated. However, calculation of energy efficiency (Mcal intake/kg egg mass) shows that all birds in have equal conversion of diet energy to egg mass, with a clear trend for improved efficiency as the energy level of the diet declined. The converse occurred in Experiment 2, where energy efficiency continually declined as the diet was further reduced in nutrient density. Mortality averaged 3% in Experiment 1 and 1.5% in, and was not related to diet treatment. Birds did adjust their feed intake in response to changing diet nutrient levels, and this is likely a response to change in diet energy [1, 3, 5]. However, the bird s adjustment of energy was different according to the method of diet presentation. With sand/cellulose dilution, the feed intake adjustment was very precise, resulting in consistent energy intake and energy intake:egg mass. With simple diet dilution, the relative balance of all nutrients is maintained, and under this idealized situation birds respond well. The sand/cellulose filter did not seem to limit physical intake as sometimes occurs with cellulose alone. In, using reformulation, the adjustment is less precise, and birds over-consume both feed and energy. This adverse response may occur because inadequate control over formulation creates a marginal deficiency of some nutrient. However, with increased feed intake, this situation should be nullified. In the 15% nutrient dense diet, however, there is significant emphasis on wheat and barley to supply amino acids in this low-protein diet, and perhaps their contribution was overestimated. As previously suggested, even marginal deficiencies of amino acids can lead to increases in feed intake [4]. An alternate theory to account for feed intake results seen in is that diet energy

7 52 JAPR: Research Report level was not as high as expected. We could have overestimated the energy contribution of barley and wheat, and/or their net energy yield is less than for corn. Layers fed the lower nutrientdensity diets were smaller, and in Experiment 2, this situation occurred even though calculated energy intake was increased. Increased energy intake is usually associated with obesity and increased body weight [6] rather than the converse situation, and so this supports the theory that birds in fact did not achieve the energy intakes calculated for these diets. All birds produced a surprisingly similar egg mass. Classical feed efficiency therefore favored the control diet. However, energy intake:egg mass was unaffected by diet treatment in Experiment 1, while deterioration in energy efficiency CONCLUSIONS AND APPLICATIONS 1. Low nutrient density layer diets may be considered economical in certain regions depending on the relative value of available ingredients. However, there is doubt concerning the ability of modern layer strains to eat enough feed when offered such diets. 2. In this study birds were offered a control corn-soybean diet providing 2,900 kcal/kg and 18.2% CP or this nutrient profile diluted by 5, 10, or 15%. When such diets were prepared by using an inert filler, birds were able to adjust their feed intake and maintain a constant energy supply from 19 to 67 wk. Using reformulation involving ingredients such as wheat, barley, and bran, birds performed less efficiently, even though energy intake was not apparently compromised. 3. As long as normal nutrient balance is achieved with low nutrient density diets, modern layer strains seem to do well with diets providing as little as 2,465 kcal/kg and 15.5% CP used throughout a complete laying cycle. 4. Problems with low nutrient density diets used by the common method of reformulation are likely a consequence of inadequately predicting nutrient supply from substituted high-fiber ingredients. 1. Morris, T.R., The effect of dietary energy level on the voluntary calorie intake of laying birds. British Poultry Sci. 9: Summers, J.D., and S. Leeson, Influence of diets varying in nutrient density on the development and reproductive performance of White Leghorn pullets. Poultry Sci. 72: Parson, C.M, K.W. Koelkebeck, Y. Zhand, X. Wang, and K.W. Leeper, Effect of dietary protein and added fat levels on performance of young laying hens. J. Appl. Poultry Res. 2: Boarman, K.W., Regulation of protein and amino acid intake. Pages in: Food Intake Regulation in Poultry. K.W. Boarman, and B.M. Freeman, eds. Br. Poultry Sci., Edinburgh, UK. in is due to apparent over-consumption of energy. There are few other reports of energy efficiency of layers fed diets of variable nutrient density. In conducting such studies one is aware of the limitations for immediate industry application. These trials were conducted with only one strain of bird, and these pullets were at the Shaver White target weight at 19 wk (1400 g). Previous data have shown no strain differences in response to diet nutrient density [7, 8], although such data may need to be re-evaluated for pullets that are underweight at sexual maturity. Also, the present trials were conducted at ambient temperatures around 20 C, and the bird s ability to regulate intake according to diet nutrient density seems to diminish as environmental temperature increases [9]. REFERENCES AND NOTES 5. Cherry, J.A., D.E. Jones, D.F. Calabotta, and D.J. Zelentca, Feed intake response of mature White Leghorn chickens to change in feed density. Poultry Sci. 62: Leeson, S., and J.D. Summers, Commercial Poultry Nutrition. 2nd Edition Publ. Univ. Books, Guelph, Ont., Canada. 7. Doran, B.H., J.H. Quisenberry, W.F. Krueger, and J.W. Bradley, Response of thirty egg-type stock to four layer diets differing in protein and caloric levels. Poultry Sci. 59: Latshaw, J.D., G.B. Havenstein, and V.D. Toell, Energy level in the laying diet and its effects on the performance of three commercial Leghorn strains. Poultry Sci. 69: Pell, A.S., and R.W. Polkinghorne, Effect of dietary nutrient concentration on the performance of hens beginning lay in early summer. Australian J. Exp. Agric. 26: