J. Anim. Sci. 2004. 82:3049-3057
© 2004 American Society of Animal Science
Use of pet food-grade poultry by-product meal as an alternate protein source in weanling pig diets
C. E. Zier,
R. D. Jones and
M. J. Azain1
Animal and Dairy Science Department, University of Georgia, Athens 30602
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Abstract
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Three experiments were conducted to evaluate pet food-grade poultry by-product meal (PBM) as a replacement protein source for fish meal (FM), blood meal (BM), and spray-dried plasma protein (SDPP) in weanling pig diets. In the first study, 200 crossbred pigs (initial BW = 6.5 kg) were weaned (21 d) and randomly allotted to one of four dietary treatments, which included a control and three test diets where PBM was substituted for FM, blood products, or both. Experimental diets were fed during Phase I (d 0 to 5 postweaning) and Phase II (d 5 to 19), and a common Phase III diet was fed from d 19 to 26. Overall (d 0 to 26), there was no difference in performance of pigs fed PBM in place of the other ingredients. However, during Phase I, BW (P < 0.05), ADG (P < 0.02), and intake (P < 0.001) in pigs fed diets containing SDPP were greater than those fed diets with PBM. In Exp. 2, the performance of pigs (n = 100, initial BW = 6.5 kg) fed diets containing 20% PBM (as-fed basis, replacing SDPP, BM, FM, and a portion of the soybean meal) in all phases of the nursery diet was compared with a group fed conventional diets without PBM. There were no differences in overall performance (d 0 to 26); however, ADG (P < 0.10) and feed intake were higher (P < 0.01) for pigs fed the conventional diet than for pigs fed the 20% PBM diet during Phase I (d 0 to 5). Experiment 3 was a slope-ratio assay to determine the ability of PBM to replace SDPP. A total of 320 pigs (initial BW = 7.32 kg) was weaned (21 d) and allotted to five treatment groups in three trials in a blocked design with product (SDPP or PBM) as the first factor, and lysine level (1.08, 1.28, 1.49%; as-fed basis) as the second factor. Growth rate increased with increasing lysine (P < 0.05), regardless of the source. These results indicate that PBM can be used in nursery diets in place of blood meal and fish meal without affecting performance. Furthermore, although feeding PBM in Phase I diets was not equivalent to SDPP during the first week, there was no overall difference in performance at the end of the nursery phase.
Key Words: Agricultural By-products • Performance • Pigs
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Introduction
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To maximize use of farrowing facilities and sow productivity, pigs are typically weaned before physiological maturity of their digestive tract (Maxwell and Carter, 2001
). As a result, the growth performance of pigs during the first few weeks postweaning is poorer than that seen during the last week of lactation. To circumvent this effect, diets for newly weaned pigs are typically formulated with highly palatable and readily digestible animal protein sources that make the diets in this phase of production relatively expensive. Several typically fed ingredients are whey, fish meal (FM), spray-dried plasma protein (SDPP), and blood meal. Previous investigations have shown that whey is important as a source of both lactose and protein (Tokach et al., 1989; Mahan, 1992; Hansen et al., 1993; Nessmith et al., 1997). The value of FM as a protein source in starter diets has also been documented (Stoner et al., 1990; Kim and Easter, 2001). Since the early 1990s, the pork industry has consistently used spray-dried plasma in Phase I diets because of the product’s ability to stimulate feed intake during the first 1 to 2 wk after weaning (Kats et al., 1994a; Hansen et al., 1993). Blood meal (BM) or blood cells have been utilized in Phase II diets (Kats et al., 1994b; Owen et al., 1995; DeRouchey et al., 2002).
Poultry by-product meal (PBM) may represent an alternative, lower-cost protein source and has been used in other monogastric diets, particularly pet foods (Murray et al., 1997) and poultry diets (El Boushy, 1994; Boling and Firman, 1997). There are, however, a limited number of reports examining the utility of PBM as a protein source for nursery pigs (Veum and Haque, 1994; Seddon and Smith, 1997; Veum et al., 1999; Keegan et al., 2004), none of which has been published in peer-reviewed media. The objective of this series of studies was to test pet-food grade PBM as an alternative protein source for more commonly used animal proteins in swine starter diets. Because the value of whey in starter diets is as both a lactose and protein source, the focus of these investigations was on replacement of the protein sources, FM and blood products (SDPP and BM) with PBM.
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Materials and Methods
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The experimental protocols used in this study were approved by the Animal Care and Use Committee of the University of Georgia (UGA). Pet food-grade PBM was provided by American Proteins, Inc. (Cumming, GA). An analysis of the PBM used for these experiments is listed in Table 1. Lot 1 of PBM was used for Phase I diets in Exp. 1 and 2; Lot 2 was used for all other experimental diets.
Experiment 1
A total of 200 (100 gilts, 100 barrows) crossbred pigs (DRU sires [International Boar Semen, Eldora, IA] [Hamphire x Landrace x Large White females]; initial BW = 6.5 kg) from two consecutive farrowing groups at the UGA Swine Center was weaned (21 d) and randomly allotted to four dietary treatments to determine the effects of replacing blood products (SDPP in Phase I and BM in Phase II) with PBM and fish meal with PBM. Barrows and gilts were penned separately. The study was conducted at the Large Animal Research Facility, UGA Animal Science Complex, in an environmentally controlled room with continuous artificial lighting, woven-wire flooring and pull-plug waste pits. Pens were 0.94 m wide x 1.83 m long. The temperature was maintained at 26 to 27°C. In each trial of 20 pens, pigs were allotted five pigs per pen, based on sex, weight, and litter. There was a total of 40 pens, with five pens of barrows and five of gilts on each of the dietary treatments. The Phase I diets (1.5% lysine) included a basal diet containing both FM (5%) and SDPP (3%), and three test diets in which PBM replaced either FM (Diet 2), SDPP (Diet 3), or both (Diet 4). Phase II diets (1.375% lysine) included a control diet with 2.5% BM and 2.5% FM and three other diets replacing FM, BM, or both with PBM. Phase I and II diets were formulated to contain equivalent levels of lysine, sulfur AA, Ca, and total P. Levels of all other essential AA were at or above the NRC (1998) recommendations. The Phase I pelleted diets were fed for 5 d (d 0 to 5); the Phase II pelleted diets were fed for 14 d (d 5 to 19), and a common Phase III ground diet (1.25% lysine) was fed for 7 d (d 19 to 26). Diet composition and nutrient content are summarized in Table 2. Test diets and water were available to the pigs ad libitum via five-hole self feeders and nipple waterers. Animals were monitored daily. Pigs were weighed at weaning and again at 5, 12, 19, and 26 d postweaning. Feed intake was determined at these same intervals. The two pigs closest to the average weight (based on d 12 weights) of the pen were bled from the jugular vein on d 13 of the study (0800 to 1000) to determine serum urea N concentrations (Sigma Diagnostics, St. Louis, MO).
Experiment 2
In this experiment, performance by pigs fed the control diets (as in Exp. 1) was compared with that of pigs fed diets with 20% PBM in all three nursery phases. The objective was to determine whether there were detrimental effects of high levels of PBM. In the Phase I diet, PBM replaced 50% of the soybean meal and all of the SDPP and FM. In the Phase II diet, PBM replaced 70% of the soybean meal and all of the BM and FM. Approximately 80% of the soybean meal in Phase III diets (Table 3) was replaced with PBM. There was a total of 20 pens (five pigs per pen), with five pens of barrows and five pens of gilts in each dietary group. Pigs were weighed and allotted as in Exp. 1. Blood samples were obtained on d 13 (0800 to 1000) by venipuncture from the two pigs closest to the average weight (based on d 12 weights) for determination of effects of diet on serum urea N concentration.
Experiment 3
A total of 360 crossbred pigs (initial BW = 7.32 kg) from the UGA Swine Center was weaned (21 d) and randomly allotted to five treatment groups in three trials of 120 pigs each. This study was conducted at the UGA Swine Center nursery in a blocked design to test nutrient availability from PBM relative to the more established product, SDPP, using a slope-ratio design (Sato et al., 1987; Kim and Easter, 2001). Relative feeding values were obtained by comparing the slopes of the growth performance regression lines (Lindemann et al., 2000). Temperature was maintained at 27°C. Continuous artificial lighting was maintained. The pens were 1.22 m wide x 2.84 m long with woven-wire flooring. Feed and water were provided ad libitum via five-hole self feeders and nipple waterers. Both feed and piglets were weighed weekly. In each trial, pigs were placed into 15 pens (three pens per diet) with eight pigs per pen (four gilts and four barrows), based on weight, and litter.
The compositions of diets used in Exp. 3 are shown in Table 4. The basal diet was formulated with no SDPP or PBM and 1.08% total lysine, which is below the NRC (1998) requirement for 10- to 20-kg pigs. Other AA were at levels that represented at least an ideal pattern relative to lysine (Fuller, 1994). The basal diet (1.08% lysine) included 6% cornstarch as a nonprotein ingredient. Test diets were formulated with 3 or 6% SDPP or PBM at the expense of cornstarch. Crystalline lysine, methionine, and threonine were added to maintain ideal protein patterns (Fuller, 1994). The calculated total lysine content of diets with 3 and 6% of the test ingredients was 1.28 and 1.49%, respectively. Pigs in each treatment group were fed the same diet for 3 wk.
Statistical Analyses
All data was analyzed using the GLM procedure of SAS (SAS Inst., Inc., Cary, NC). Pen was considered the experimental unit in all experiments. Experiments 1 and 2 were conducted in two trials; thus, trial and the interactions with diet and gender were also tested. Experiment 1 was analyzed as a 4 x 2 design with main effects of diet and gender and their interactions. In addition, orthogonal comparisons were used to determine the effects of replacing PBM for blood products (Diets 3 and 4 vs. 1 and 2) and PBM vs. FM (Diets 2 and 4 vs. 1 and 3). The effects of diet (conventional vs. 20% PBM) and gender were tested in Exp. 2. In Exp. 3, contrast statements were used to compare performance of the pigs fed the basal diet to all others, to compare SDPP to PBM, and to compare 3 and 6% levels within these ingredients. To evaluate the slope of the regression line in Exp. 3, lysine dose and source (PBM or SDPP) were fitted to a linear model to obtain regression equations that related ADG to lysine level (DeRouchey et al., 2002; Kim and Easter, 2001). The model also included trial. Results for all experiments are reported as least squares means.
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Results
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Experiment 1
Six pigs (out of 200) across treatments were removed due to lameness, illness, or death. There were no effects of gender on performance and no gender x treatment interactions in Exp. 1, thus results were pooled across gender (Table 5). In Phase I (d 0 to 5), BW (P < 0.03), ADG (P < 0.02), and intake (P < 0.01) were less in pigs fed diets with PBM. The negative effects were greatest in Diet 4, where PBM replaced both SDPP and FM. There were no differences in the contrast of PBM for FM for BW (P = 0.24), ADG (P = 0.19), or intake (P = 0.15). However, pigs fed either of the diets with PBM (Diet 3 and 4) in place of SDPP (Diet 1 and 2) had decreased BW (P < 0.01), ADG (P< 0.01), and intake (P < 0.01). Pigs were switched to the Phase II diets on d 5, and by d 12, BW was similar across treatments. Gain from d 5 to 12 was greater (P < 0.04) in pigs fed diets with PBM (Diets 3 and 4) compared with those fed diets with BM (diets 1 and 2). Gain:feed tended to be less (P < 0.11) in pigs fed diets without SDPP during Phase I, but this was compensated for by a trend for improved (P < 0.12) efficiency during the first week of Phase II. Overall (d 0 to 26), there were no differences (P 
0.83) in performance of pigs fed PBM in place of SDPP and BM. Substitution of PBM for FM in Phase I or II had no effect on performance. Serum urea N concentrations (determined on d 13) were not affected by diet.
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Table 5. Effect of replacing fish meal, spray-dried plasma protein (SDPP)/blood meal, or both with poultry by-product meal (PBM) on nursery performance (Exp. 1)a
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Experiment 2
One pig from the 20% PBM group was removed on d 5 due to lameness. There were no significant effects of gender and no gender x diet interactions; thus, results were pooled for the barrows and gilts (Table 6). Body weight (P < 0.09) and feed intake (P < 0.01) during Phase I were greater for pigs fed the control diet compared with pigs fed the 20% PBM diet. During Phase II, there were no differences in BW, ADG, feed intake, or feed efficiency; however, in Phase III, both ADG (557 vs. 451 g/d, P < 0.01) and G:F (0.75 vs. 0.67, P < 0.06) were improved in pigs fed the control compared with the PBM diet. Overall (d 0 to 26), there were no significant differences in performance between pigs fed PBM when compared with those fed more traditional starter diets. Serum urea N concentrations were not significantly different between treatments.
Experiment 3
Five pigs (out of 360) across treatments were removed due to lameness, illness, or death. Initial weight was less in pigs assigned to the SDPP diets compared with those fed PBM (7.34 vs. 7.48 kg; P < 0.01). Because of this difference, subsequent weights were covaried for the initial BW (Table 7). During the first week, pigs fed the 3 and 6% SDPP diets (135 g/d) had greater rates of gain than those fed the control (58 g/d) or the PBM diets (74 g/d; P < 0.001). Overall (d 0 to 21), the SDPP diets supported greater ADG than the PBM diets (250 vs. 229 g/d; P < 0.06). During the first, second, and third weeks, and overall, pigs fed SDPP or PBM had greater ADG than those fed the basal diet. There was a step-wise increase in final weight and ADG in pigs fed 0, 3, and 6% SDPP. With the exception of feed efficiency, which was greater for pigs fed 6% PBM than for those fed 3% (0.70 vs. 0.63; P < 0.02), there were no differences in performance between the levels of PBM. During the first week postweaning, ADG per unit of lysine intake was greater (P < 0.01) for pigs consuming diets with SDPP (47.3 g/g) compared with pigs fed the basal (24.1 g/g) or PBM-containing diets (28.4 g/g), which did not differ from each other. During the second and third weeks, differences in ADG were accounted for by the level of lysine in the diet and were independent of the source of lysine. Thus, there was a stepwise increase in ADG from the basal to the 3 and 6% levels of SDPP or PBM, but there was no difference between SDPP or PBM. When ADG over the 3-wk study was corrected for intake, there were no differences across treatments nor between products (SDPP or PBM).
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Table 7. Growth performance of pigs fed spray-dried plasma protein (SDPP) vs. poultry by-product meal (PBM, Exp. 3)a
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Comparing the slope of the regression line for overall ADG with dietary lysine demonstrates that there was a linear effect of increasing dietary lysine concentration on ADG in the nursery (Figure 1). The resulting linear model indicated the lines were different from zero (P < 0.005), but the slopes of the two lines were not different (P = 0.17) from each other. The equations for overall gain (y, in g/d) in response to addition of either ingredient (x, as a % of the diet) were as follows: SDPP, y = 186.3 + 14.5x; and PBM y = 186.3 + 8.9x (SEM 2.8; P = 0.17; Figure 1).
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Figure 1. Average daily gain in pigs fed diets containing 3 or 6% spray-dried plasma protein (SDPP) or pet-food grade poultry by-product meal (PBM). Symbols represent individual pen averages for basal (•, 1.08% dietary lysine), PBM ( ,1.28%;  ,1.49% lysine), and SDPP ( , 1.28%;  , 1.49% lysine) diets. Pigs were weaned at 21 d of age (7.3 kg) and fed test diets for 3 wk. The equations for overall gain (y, in g/d) in response to addition of either ingredient (x, as a % of the diet) were as follows: SDPP, y = 186.3 + 14.5x and PBM, y = 186.3 + 8.9x (SEM 2.8; P = 0.17).
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Discussion
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This series of experiments examined the use of pet food-grade PBM in nursery diets to replace higher-cost ingredients. Blood products, FM, and whey represent the relatively higher-cost sources of protein and energy in nursery diets. Because of the established role of whey as both a source of AA and lactose, its levels were held constant in these studies, and blood product and FM levels were altered. The diets were balanced for energy, Ca, P, lysine, and methionine, resulting in slight adjustments in levels of other ingredients in the diets.
Standard PBM consists of the viscera, head, undeveloped eggs, and the feet from poultry slaughter that are then rendered, dried, and ground into a meal (Miller et al., 1994). The pet food industry, however, demands a product of higher quality and uniformity. Pet food-grade PBM has more protein (65 vs. 60%) and lysine (3.9 vs. 3.4%), less ash (13.5 vs. 17.0%), and is less variable than the standard product (American Proteins; Griffin Industries, Cold Spring, KY). Compared with the ingredients in the present studies, PBM tends to have lower CP and lysine content relative to the blood products and similar CP but lower lysine content relative to FM. In addition to providing essential AA, PBM is also a good source of Ca (4.46%) and fat (12.6%; NRC, 1998).
In Exp. 1, pigs fed PBM had equivalent performance to those fed FM, indicating that PBM could be substituted in Phase I and II diets. However, in all three experiments, pigs fed PBM in place of SDPP in Phase I diets had decreased feed intake and slower growth rates during the first week postweaning. In general, the growth advantage conferred by feeding SDPP during Phase I was lost during the time the Phase II diets were fed. This intake response to SDPP relative to other ingredients has been observed in numerous other studies (Hansen et al., 1993; Kats et al., 1994a; Grinstead et al., 2000), and is a characteristic of SDPP that continues to make it attractive despite its cost. Previously, de Rodas et al. (1995), Hansen et al. (1993), and Kats et al. (1994a) have reported an increase in ADG and intake when SDPP was included in Phase I diets at the expense of dried skim milk or soybean meal. However, when one considers the entire nursery period, there is no long-term advantage to using SDPP. Similarly, in the present work, despite the poorer performance of pigs fed PBM in place of SDPP during the first week postweaning, overall growth and intake was not different. Differences between SDPP and PBM in Exp. 3 are accounted for by the failure of pigs fed 6% PBM to perform differently than those fed 3% PBM. At the 3% level, overall performance was not different between SDPP and PBM. Additional studies that include various combinations of SDPP and PBM in Phase I diets are warranted.
In Exp 1, the Phase I diet was fed for the first 5 d, and then pigs were switched to the Phase II diet. The Phase I diets contained SDPP and the Phase II diet contained BM. Pigs fed SDPP-containing diets had greater ADG than those fed PBM during the first 5 d postweaning, but reduced ADG during the subsequent week. Thus, the recovery of BW in pigs fed PBM-containing diets (Exp 1) during the second week could be compensatory gain in response to the poorer performance during the first week, or could be due to a difference in response to BM vs. PBM. In Exp. 3, the same diet was fed for the duration of the study. Pigs fed diets containing SDPP gained more than those fed diets with a similar lysine content from PBM during the first week postweaning (Table 7
). There was no difference in ADG in subsequent weeks. Thus, it would seem that the lower ADG of pigs fed PBM relative to those fed SDPP during the first week and the subsequent recovery during the second week seen in Exp. 1 is due to the switch to BM in place of SDPP rather than to a compensatory response. The slope-ratio study indicated that the slopes of the line for gain vs. lysine content were not different (P = 0.17) for SDPP and PBM. However, the ratio of slopes was 0.62, indicating PBM has 62% of the value of SDPP. This difference in ratios is largely due to lower growth by pigs fed PBM at the 6% inclusion level. At 3% inclusion, the ingredients were equivalent. It should be noted that in Exp. 2, which was conducted under more practical conditions, much higher levels of PBM were fed for the entire nursery period, and no negative effects were observed. Further research at different levels of inclusion is needed to determine whether the decreased performance observed in Exp. 3 is due to palatability or some other factor. Correcting ADG for differences in calculated lysine intake indicates that per gram of lysine intake, there was no difference between ingredients (Table 7). Gain was approximately 50 g/g of lysine consumed, regardless of its source. Feeding 20% PBM in Phase I and II had no significant effect on overall performance (Table 6).
Despite differences in ADG during the first week postweaning, overall, in all three studies, there were no differences in performance of pigs fed PBM in place of blood products. These results indicate that PBM can be used in nursery diets in place of BM and FM without affecting performance, but may not be equivalent to SDPP in Phase I diets. The basis for the reduced ADG during Phase III in pigs fed 20% PBM in Exp. 2 is not clear. These results are consistent with Veum and Haque (1994), who compared spray-dried PBM to SDPP in nursery diets and reported that during the first week, SDPP-fed pigs had a higher ADG and intake than the pigs fed the PBM, but overall there was not a significant difference in piglet performance. It should be noted that spray-dried PBM is different from conventionally rendered PBM. It has been speculated that compensatory gain and feed intake occurs following environmental or nutritional insults (Mahan and Lepine, 1991), possibly including postweaning "lag." This would in part account for the improvements in feed intake and ADG seen during the second week of all three experiments.
Collectively, these experiments show that PBM is an effective replacement for higher-cost ingredients. It is concluded that based on growth performance during the first week postweaning, PBM cannot fully replace SDPP in Phase I diets. Nonetheless, use of PBM under practical feeding conditions in nursery diets seems to be an equivalent substitute for SDPP based on final nursery weights. There was no loss of performance when PBM was substituted for BM in Phase II or for FM in either phase.
1 Corresponding author—phone: 706-542-0963; fax: 706-542-0399; e-mail: mazain{at}arches.uga.edu.
Received for publication February 13, 2004.
Accepted for publication June 15, 2004.
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Abstract
Introduction
