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Research Reports |
* Department of Agricultural and Biological Engineering, and Department of Poultry Science, The Pennsylvania State University, University Park 16802
2 Corresponding author: vmpuri{at}psu.edu
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SUMMARY |
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 TOP SUMMARY DESCRIPTION OF PROBLEMMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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Key Words: feed segregation • feed trough delivery system • feed nutrient • feed particle size • laying hen performance
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DESCRIPTION OF PROBLEM |
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TOPSUMMARYDESCRIPTION OF PROBLEMMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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Mash feed has a wide range of particle sizes, from well above 3.00 mm to well below 0.10 mm. Various particle sizes are derived from different ingredients and provide different nutrients to the feed. If large particles separate from the small particles during the delivery of the feed to hens’ locations, then the different ingredients and nutrients would separate as well. The phenomenon that larger particles separate from smaller particles in a mixture is called segregation (i.e., segregation leads to nonhomogenous distribution of nutrients along the trough in the direction of feed delivery). Thus, the hens’ daily nutrient requirements may not be met, depending on selection and consumption of large or small particles.
The particle size-related effects of cereals such as corn, wheat, and sorghum (ground, unground, or both) on hen and broiler performance or nutrient composition and uniformity have been investigated over the years by several researchers. For instance, Nir et al. [3] reported that the best performance of young broilers was obtained with a diet prepared from medium corn size of 0.769 mm. Furthermore, young broilers consumed more feed and gained a higher BW when their diets containing the coarser particles [4]. Deaton et al. [5] compared the performance of laying hens fed corn ground to different particle sizes and concluded that no effect on performance was observed over 3 consecutive trials. Literature also shows that if grains are incorporated into mash feeds, fine particle sizes should be avoided [6]. However, little work has been done on the effect of the feed trough delivery system on feed segregation, nutrient composition, or hen performance.
Accordingly, the purpose of this research was to determine the effect of the feed trough delivery system on feed segregation, nutrient composition, bird performance, and egg quality.
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MATERIALS AND METHODS |
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TOPSUMMARYDESCRIPTION OF PROBLEMMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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Sampling Methods
In each house, there were 6 rows, each with 3 decks of cages. Of these, cage row 3 including the top and bottom decks and 6 sampling locations along the feed trough of each deck were selected for study purposes (Figure 1
; i.e., there were 12 sampling locations in each house). The experiment was performed from July 2001 to June 2002. This period covered 1 cycle of production from 21 to 63 wk of age. Sampling dates and times were determined based on the hen’s age, performance, and feed formulation changes. The BW of 1 cage of hens (10 birds/cage) at each sampling location was measured 3 times during the cycle, at 18-wk intervals, from 21 to 63 wk. Egg and feed samples were collected 8 times (once every 6 wk) during the life of the flock, because the feed formulation was modified every 6 wk to meet the hens’ requirements for growth and egg production. There were 144 eggs (12 eggs/sampling location) and approximately 12 kg of feed sample (approximately 1 kg of feed sample per sampling location) collected in each house for 1 time. All the feed samples, egg samples, and BW were collected or measured within 1 or 2 h of feeding at around 0900 to 1100 h. The feed delivery system supplied feed 4 times daily (i.e., birds were fed at 0600, 0830, 1445, and 1830 h, respectively).
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Data Acquisition
All the egg and feed samples were transported to The Pennsylvania State University’s Poultry Education and Research Center for subsequent testing. Egg parameters including egg weight, specific gravity, albumen height, and Haugh units were tested after eggs were stored in a refrigerator at 12°C overnight (around 12 h). A digital scale was used to measure the egg weight, 9 salt solutions were used for the specific gravity determination (from 1.060 to 1.100 in increments of 0.005), and a digital micrometer was used to measure albumen height (mm). After breaking the eggs for albumen height, the remaining liquid inside the eggshells was washed out manually, membranes were removed, and the shells were dried at 21°C for 1 wk before measuring the thickness and weight of eggshells. To obtain the average value of eggshell thickness, 2 points along the egg equator and 2 points at the egg poles were selected for each eggshell.
Feed samples in the layer house were collected using a portable vacuum [8]. Feed particle size was characterized using US standard sieves for each visit. However, due to cost considerations, the feed nutritional parameters such as energy, protein, amino acid, mineral, and vitamin fractions were determined when the birds were 39 wk of age by a commercial laboratory.
Data Analysis for Feed Nutrients
Feed samples for nutrient analysis were collected once when the birds were 39 wk of age for cost considerations at 4 locations including the hopper and trough locations front end (FE), rear beginning (RB), and rear end (RE), as shown in Figure 1
. At each location, feed nutrient analyses were replicated 3 times.
A percentage difference approach was used to analyze feed nutrient changes from their starting point at the hopper. The rationale for this approach was due to the fact that the feed nutrients, including vitamins, mineral elements, energy, protein, fiber, fat, carbohydrate, and various amino acids, are expressed in different units. Thus, direct comparisons of numbers are not meaningful. Herein, the percentage difference of the nutrient components was used to measure the degree of the effect of feed trough location on feed nutrient distributions. For instance, to examine the difference in vitamin A content at the hopper vs. along the feed trough for the DC house, the average quantity of the vitamin A at locations FE, RB, and RE [designated by variable X, i.e., X = (FE + RB + RE)/3, locations shown in Figure 1] minus the quantity of vitamin A at the hopper (designated by variable Y), then (X – Y)/Y x 100 gives the percentage difference. For instance, a value of 167% means that the vitamin A content along the feed trough is 1.67 times higher than that in the hopper.
A similar calculation was done to analyze the effect of location within the feed trough on nutrient distributions. To examine the difference in vitamin A contained at the middle of the feed trough (i.e., locations FE and RB shown in Figure 1) vs. the end of the feed trough (location RE), the quantity of vitamin A at location RE (designated by variable P) minus the average quantity of vitamin A at locations FE and RB [designated by variable Q, i.e., Q = (FE + RB)/2], then (P – Q) divided by the quantity of vitamin A at the hopper (Y) and multiplied by 100 gives the percentage difference. For instance, a value of 19% implies that the difference in vitamin A at the end of the feed trough vs. the middle of the feed trough is nearly one-fifth of the vitamin A content at the hopper.
Data Analysis for Hen Performance
All hen performance-related measurements were analyzed through ANOVA with respect to 3 factors: hen age, feed delivery system, and hen location along the feed delivery system [9]. A Tukey’s test with a significance level of 
= 0.05 was utilized for multiple means comparison of each variable [9].
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RESULTS AND DISCUSSION |
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TOPSUMMARYDESCRIPTION OF PROBLEMMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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Feed Particle Size Distribution and Segregation
Effects of Both Feed Trough and Hen Selection.
From either the bird’s selection or feed segregation potential, a particle size of 1,180 µm is selected as a critical value to evaluate the particle size variation in the feed trough [10, 11]. Thus, the factors that affect feed quality, including feed delivery devices and bird selection, are compared and identified through determination of the percentage of particle sizes < 1,180 µm. For feed particle sizes < 1,180 µm, segregation phenomena are not as critical as for larger particles.
The percentage of feed particle sizes < 1,180 µm (61.7%) for the average DC trough sample was significantly higher than that at the hopper (45.8%; Table 1). This indicated that the hens consumed a major portion of particle sizes >1,180 µm delivered by the DC. Similarly, the average portion (60.2%) of finer particle sizes (< 1,180 µm) in the AU trough was significantly higher than at the hopper (46.8%). These results showed that the birds consumed a predominant proportion of feed particles >1,180 µm in both delivery systems. These data also confirmed that with either DC or AU delivery systems, hens preferred to eat particles >1,180 µm.
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, the percentages of fine particles < 1,180 µm are not significantly different (P > 0.05) between the DC and AU delivery systems. From this result, it can be inferred that, after hens ate a significant number of larger particles, the remaining fines accumulated in the feed trough as a result of several cycles of operation of the feed delivery system.
Effects of Only Feed Trough Delivery System.
It was determined that the feed delivery system did not significantly affect feed particle size distribution. When the hens were not present to select feed particles, the mean percentage of particle sizes < 1,180 µm in the DC feed trough was 40% and not different (P > 0.05) than that in the feed hopper at 43% (Table 1). A similar phenomenon occurred for the AU delivery system, with 40% of particle sizes < 1,180 µm and not different than in the feed hopper (42%; P > 0.05). This shows that neither the DC nor AU had a significant effect on feed segregation (i.e., after the delivery system cycled for several times, segregation phenomena were not significantly different). Actually, within a cross-section of the feed trough, segregation still occurred (see next subsection, "Feed Particle Segregation Patterns"). Furthermore, the AU system had less effect on particle size segregation than the DC system due to its helical structure, which promotes some feed remixing. The AU system has better performance than the DC system. This observation was consistent with the result obtained by Zeigler [2]. A similar conclusion was also drawn from the perspective of bird performance, which is given in the "Hen Performance" section of this paper.
Feed Particle Segregation Patterns.
Feed particle segregation patterns were observed and analyzed when there were no birds in the house. Two segregation patterns occurred while mash feed was delivered through the DC feed trough. One pattern is top-to-bottom segregation, or percolation, sieving segregation, or both [12, 13] (i.e., fine and dense particles percolated to the bottom of the trough, whereas larger and less dense particles rose to the top). The second pattern, side-to-side segregation, is when larger particles moved to the 2 sides of the feed trough, whereas smaller particles stayed at the center of the trough. In other words, finer particles were segregated from the mixture and deposited along the way as the DC moved forward. This type of segregation occurs due to the relative larger dimension of the DC trough bottom [11]. These 2 segregation patterns constantly present the larger feed particles on the surface to the hens for their selection and consumption.
Another type of segregation pattern for the AU was top-to-bottom segregation. The segregation potential was decreased because of the helical structure of the AU, which helped the feed within the trough to partially remix as the AU moved forward. Based on observations, the percolated fine particles not only filled in the voids between the AU and the surface of the feed trough, but also served as a lubricant to prevent particles from further fragmentation. Thus, not only was the attrition not as significant in the first cycle of feed through the AU trough, but also segregation appears to occur to a very limited degree due to the percolated fines from the first run that already occupied most void spaces. Therefore, repeated cycling of the feed delivery system is an effective approach to study and quantify segregation.
Feed Nutrient Analysis
If it is assumed that percentage nutrient differences >10% are considered to be important, one might conclude that the DC house nutrients, including vitamin A (167%), vitamin D (37%), Ca (13%), Na (86%), P (17%), total amino acids (14%), CP (18%), and ash (30%), at the feed trough are notably higher than those in the hopper (Table 2). This analysis implies that other nutrients such as carbohydrates, N-free extract (NFE), and gross energy (e.g., large-particle corn) were consumed in quantities such that the vitamin A, vitamin D, Ca, and other nutrients were concentrated in the feed. If birds do not consume these nutrients in their required amounts, they may be at risk for nutrient deficiencies.
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; i.e., these nutrients were effectively consumed by the birds). Similar trends in nutrient distribution can be seen from the AU house for vitamins, amino acids, CP, NFE, and carbohydrates. The above observations are further explained in terms of the feed particle size distributions. Generally, the large particles were mostly corn and contained primarily carbohydrates, NFE, calories, and other nutrients. The other dietary nutrients such as vitamins, minerals, and amino acids from protein sources were contained in the small particles. Due to bird selection, segregation, and attrition, these fine particles continuously accumulate along the feed trough after several feeding events. Thus, the percentage of these nutrients along the feed trough is much higher than that at the hopper. This explanation was verified further by the correlation of the feed nutrients to particle size distributions.
Similarly, if it is assumed that percentage changes >10% because of feed trough location are considered important, then for the DC house, the location effect is important for vitamin A (19%), riboflavin (25%), vitamin D (20%), Ca (21%), Mn (20%), Na (71%), and ash (12%; Table 2). Similar calculations performed for the AU house indicated the feed trough location effect on nutrient distribution was not as great as in the DC house.
The percentage change in nutrients at the hoppers for the 2 houses indicated the concentrations at the hopper in the DC house were much higher than in the AU house (Table 2). For instance, vitamins A, D, riboflavin, and the minerals Ca, Mn, and Na in the hopper of the DC house were as much as 61% greater than those in the AU house. Although nutrient formulations for the 2 flocks in the DC and AU houses at 39 wk of age were the same, the nutrients were not.
Hen Performance
The 3 main effects of hen age, delivery system, and trough location and their interactions are shown in Table 3. It can be concluded that hen age affected all measurements significantly (P < 0.001). The delivery system was only significant for egg specific gravity and BW (P < 0.05). Trough location had a significant effect on albumen height, Haugh unit, and shell thickness (P < 0.05).
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). Furthermore, the relationships with the hen age, weight, egg weight, and eggshell weight exhibited a positive relationship, whereas the relationships between the specific gravity, albumen height, Haugh units, and eggshell thickness vs. bird age exhibited an inverse relationship (i.e., the egg quality parameters exhibit a decreasing trend with bird age). These results appear to match the natural physiological trends in egg quality associated with hen age. However, results of the feed nutrient distribution and segregation analysis given in the preceding section indicated that not all nutrients are maintained at their desired levels to meet the requirements of the hen to maintain egg quality (i.e., the natural decline in egg quality might be postponed if hens were consuming the intended dietary formulations).
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). However, the general trend was that the AU system had a more positive effect on egg quality than the DC. Specifically, the AU-fed birds had significantly better egg specific gravity compared with those hens fed with the DC (Table 4). This observation was consistent with the AU delivery system, providing greater levels of Ca and vitamin D for better eggshell quality. Hens in the DC house averaged significantly higher BW than those in the AU house (Table 4).
Feed Trough Location Effect.
Statistically, there were significant (P < 0.05) effects of hen location along the feed trough on egg quality parameters such as albumen height, Haugh unit, and shell thickness, whereas there were no significant effects on egg weight, eggshell weight, or bird weight (Tables 3 and 4). For instance, eggshell thickness was linearly correlated with feed trough location, with the greatest thickness at the beginning near the hopper and thinnest shells at the end. Also, the relationships between the albumen height and Haugh unit vs. feed trough locations had a decreasing trend to the end of the trough.
The possible reason could be due to the BW-related nutrients that were distributed uniformly along the feed trough, whereas the egg quality-related nutrients were not uniformly distributed. The feed nutrients and particle size distribution tests given in the "Correlation of Particle Size and Feed Nutrient Distribution and Effect on Performance" section show that the distribution of large particles containing the majority of gross energy and CF was not different at different feed locations. However, the distribution of the small particles mainly containing nutrients such as vitamin D and minerals differ significantly along the feed trough. In other words, those nutrients related to egg quality decreased along the feed trough, or the birds’ consumption of these nutrients was not sufficient.
Interaction Effect Between Hen Age and Delivery System.
The interaction effects between bird age and delivery system were significant for egg specific gravity, albumen height, Haugh unit, eggshell weight and thickness, and BW (P < 0.001; Table 3). Because the degree of feed mixing is different between the AU and DC systems, further information was gained from hen BW and egg specific gravity measurements herein. The largest BW were in the DC house at 57 wk. However, the eggshell specific gravity in the AU house was significantly better than that in the DC house for nearly the entire study. The above results further indicated that although the hens in the DC house had higher BW, they may not always produce the highest quality eggs, in part due to hen ingredient selection and segregation.
Interaction Effect Between Hen Age and Location.
The interaction effect between bird age and feed trough location was significant for the interior egg quality parameters albumen height and Haugh unit (P < 0.001). Egg Haugh units were not affected significantly when hens were < 45 wk old. However, Haugh units decreased along the feed trough when hens were 51 wk old and older.
Interaction Effect Between Delivery System and Location.
The interaction of delivery system and feed trough location was significant for egg weight, eggshell weight, and eggshell thickness (P < 0.001; Table 3). For the AU system, the egg weight at 2 ends of the feed trough (FB, FE, RB, and RE locations; Figure 1) was similar and higher than that at the 2 middle points of the feed trough (FM and RM locations). A completely opposite result was obtained for the DC delivery system. The other 2 measurements, eggshell weight and thickness, showed similar results as the egg weight. These results implied that the corners of the DC delivery system may have negatively affected the shell weight and thickness. Also FM and RM were negatively affected in AU. Some considerations with this theory might be: 1) FE and RE would not benefit from corner mixing in the AU or DC houses; and 2) there may be other end vs. middle house factors such as air quality and temperature that could affect egg quality.
Correlation of Particle Size and Feed Nutrient Distribution and Effect on Performance
The data showed that egg quality decreased with advancing bird age. This is consistent with the observation that most of the nutrients along the feed trough are higher in concentration than at the hopper (i.e., birds might not consume sufficient nutrients from the feed to produce the same quality eggs). In other words, the natural decline in egg quality might be postponed were hens consuming the intended dietary formulations. In addition, it was observed that egg quality from birds fed by the AU system was slightly better than those from the DC system and is generally consistent with the results that the nutrient concentrations of remaining feed from the DC were relatively higher than those of the AU. The fact that egg quality decreases with the hen location is consistent with the observation that nutrients at the end of the feed trough were higher than at the middle locations for the DC house. Trough nutrient analysis for the AU house determined nutrients affecting egg quality at the middle location are generally equal to those at the end, although there are some nutrients that vary with this statement (vitamin A, riboflavin, and Ca and Na). Dietary calories, carbohydrate, and fat were more concentrated at the feed hopper compared with locations FE, RB, and RE.
Other nutrients including CP, amino acids, vitamins A and D, and some minerals were measured at lower levels at the hopper compared with further down the feed trough. Hen BW, egg weight, and shell weight increased linearly with age, whereas egg specific gravity, albumen height, and Haugh units decreased (P < 0.05). Egg specific gravity was greater for the AU-fed hens, whereas, BW was greater for the DC-fed birds. Shell thickness decreased from the FB location to the end of the trough (RE location). The same trend was observed for albumen height and Haugh units from the FM location to the end. Bird feeding activity (selection) resulted in larger feed particles being consumed early, whereas smaller, more dense particles accumulated continuously, leading to greater levels of fines at the bottom (attributed to segregation and attrition). Selection and segregation of the feed resulted in an effect on the egg quality parameters including shell thickness, albumen height, and Haugh units.
In summary, particle size distribution results indicated that, because of particle segregation and bird selection, smaller particles remained and accumulated at the bottom of the feed trough. Nutrient analysis results indicated that birds did not consume sufficient nutrients provided in the feed formulas (i.e., the bird’s daily nutrient requirements were not met because the nutrients contained in smaller particles were not consumed by birds in sufficient quantity).
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CONCLUSIONS AND APPLICATIONS |
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TOPSUMMARYDESCRIPTION OF PROBLEMMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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REFERENCES AND NOTES |
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TOPSUMMARYDESCRIPTION OF PROBLEMMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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