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Growth response of broilers to spray-dried plasma in pelleted or expanded feed processed at high tem

Abstract
A series of 4 experiments evaluated effects of mash conditioning temperature from a pellet mill or expander on performance of broilers fed pelleted diets containing spray-dried plasma (SDP). All experiments utilized Ross x Ross 308 male broilers randomly assigned to their respective treatments (6 or 10 broilers/pen and 8 or 10 pens/treatment). Treatments in Exp. 1 consisted of a control (0% SDP), SDP coated postpelleting, or SDP blended into the meal prepelleting. Experiment 2 and 3 included the same 3 treatments as in Exp. 1 but with additional treatments of SDP blended into the meal and conditioned at 90 or 95°C before pelleting. In Exp. 4, treatments consisted of a control (0% SDP) or SDP blended into the meal and pelleted (85°C conditioning temperature) or expanded (149°C final effective temperature) and then pelleted.

Corn-soybean meal-based diets were formulated to be equal in lysine and ME in all experiments. Pelleted diets were conditioned for 15 s at 85°C, and expanded diets were conditioned at 95°C, 29.7 MJ/t, 13.95 kg/cm2 cone pressure, exit temperature of 149°C, and then pelleted through a 4 x 32-mm die. In Exp. 1, ADG and feed intake were improved (P < 0.05) for broilers fed SDP from d 1 to 28 of age, with greater BW at d 42. In Exp. 2, both in early (d 1 to 28 of age) phases, and overall (d 1 to 42 of age), broilers fed SDP had improved (P < 0.05) gain and efficiency. In Exp. 3, ADG, feed intake, efficiency of gain, and BW were improved (P < 0.01) for broilers fed SDP from d 1 to 21 of age, regardless of conditioning temperature. In Exp. 4, broilers fed SDP had improved (P < 0.05) gain, BW, and feed intake regardless of processing method. Overall, the results of all of the experiments demonstrated that pellet conditioning temperature from 85 to 95°C and expander temperatures to 149°C did not impair the positive growth effects of SDP in pelleted or expanded broiler feed.

INTRODUCTION
Approximately 80% of nonruminant feed in the United States is pelleted or expanded to take advantage of improvements in rate and efficiency of growth due to improved starch digestibility (Fairfield, 2003). Excessive conditioning temperatures during feed processing may reduce digestibility and functionality of specialty protein ingredients such as enzymes and spray-dried plasma (SDP; Inborr and Bedford, 1994; Steidinger et al., 2000). Spray-dried plasma is commonly added to swine starter diets to increase feed intake and growth (Coffey and Cromwell, 2001; Van Dijk et al., 2001). The growth-enhancing effects of SDP were not observed in swine starter diets conditioned and pelleted at 77°C or greater (Steidinger et al., 2000). Swine starter diets typically contain other heat-sensitive ingredients (dried whey, lactose) besides SDP and are pelleted at lower (<77°C) temperatures to avoid the Mallaird reaction, which results in reduced AA acid digestibility (Payne et al., 1994). However, these heat-sensitive ingredients are not commonly used in poultry feed; thus, poultry feed is pelleted at approximately 85°C or expanded at even greater temperatures to improve starch utilization. In previous experiments, SDP was added postprocessing (Bregendahl et al., 2005) to avoid potential damage to the functional proteins in SDP. However, postprocessing application of ingredients is more expensive and difficult to manage in commercial feed mills with high feed production rates. Therefore, objectives were to determine the performance response and mortality of broilers housed on used litter and fed SDP in feed conditioned at various temperatures and then pelleted or expanded.

MATERIALS AND METHODS
A series of 4 experiments involving 180, 240, 400, and 400 Ross x Ross 308 male broilers (Welp Hatchery, Bancroft, IA) was conducted in a poultry research facility containing 40 pens (56 x 122 cm). Broilers used in the experiments were handled in accordance with published guidelines (FASS, 1999). Broilers (6/pen, Exp. 1 and 2; 10/pen, Exp. 3 and 4) were housed in floor pens. Experiments 1 and 4 were designed with 10 pens/treatment, whereas Exp. 2 and 3 were designed with 8 pens/treatment. Pens contained soiled softwood shavings from previous experiments (approximately 10-cm depth), creating a high-antigen environment. Broilers (1 d of age) were randomly assigned by BW to pens blocked by location within the facility.

From 1 to 3 d of age, feed was offered ad libitum in trays (729 cm2), followed by hanging gravity-flow feeders (Brower, Houghton, IA). The hanging feeders were adjusted regularly to maintain the optimal height for feed consumption. Water was delivered via free-standing, 3.8-L poultry founts. The founts were washed daily and refilled with fresh water. Mechanical ventilation, heaters, and heat lamps were used to maintain mean temperatures at bird level of 32, 29, 27, and 24°C for wk 1, 2, 3, 4, and thereafter, respectively. Broilers were maintained on 23 h of light and 1 h of darkness daily.

Vaccinations at prehatch were one-half dose of Mareks (Merial Select Inc., Gainsville, GA) and one-half dose of Newcastle-Bronchitis (B1 B1, Merial Select Inc.) at the hatchery before shipping. At 7 d of age, all birds were vaccinated with Bursal Disease vaccine (Merial Select) via the water, and at 14 d of age they were vaccinated with Newcastle-Bronchitis vaccine (B1 B1, Merial Select) by coarse spray.

Treatments in Exp. 1 consisted of a control (0% SDP), SDP (1.0, 0.5, and 0.25%, phase 1, 2, and 3, respectively) coated postpelleting, or SDP blended into the meal prepelleting. All feeds were conditioned for 15 s at 85°C and then pelleted through a Master Model HD 1000 series California Pellet Mill (California Pellet Mill Co., Crawfordsville, IN) equipped with a die of 4 x 32 mm. Experiment 2 and 3 included the same 3 treatments as in Exp. 1 but with additional treatments of SDP blended into the meal and conditioned at 90 or 95°C before pelleting. In Exp. 4, treatments were arranged as a 2 x 2 factorial with 2 levels of SDP (0 or 1%) and 2 processing procedures (not expanded or expanded at 149°C final effective temperature before pelleting at 85°C conditioning temperature).

The feeding program for Exp. 1 and 2 consisted of 3 phases: starter from 1 to 14 d of age, grower from 15 to 28 d of age, and finisher from 29 to 42 d of age (Tables 1and 2). Dietary treatments for Exp. 3 and 4 (Table 3) consisted of a starter diet fed to 21 d of age. Spray-dried plasma (AP 920 in Exp 1, 2, and 3, or Appetein in Exp 4; APC Inc., Ankeny, IA) was produced according to standard manufacturing procedures and was included in the starter, grower, and finisher diets at 1.0, 0.5, and 0.25%, respectively. Feed was manufactured at Kansas State University (Manhattan, KS) utilizing formulas in Tables 1, 2, and 3. In Exp. 1 and 2, 1% of the supplemental fat source was added to the meal before pelleting, and the remaining fat was sprayed on postpelleting, whereas in Exp. 3 and 4 all the fat was sprayed on postpelleting.

All starter diets were crumbled. Pelleted diets were processed at their respective conditioning temperatures (Table 4) with a retention time of 15 s and pelleted through a 0.4 x 3.175-cm die. Expanded feeds (Exp. 4) were conditioned at 95°C, with a calculated exit temperature of 149°C (Farahmand and Lucht, 1998). Expander net energy use was 31.68 and 27.72 MJ/t, and the cone pressure was 12.33 and 13.95 kg/cm2 for 0 and 1% SDP diets, respectively. Production rates were 1,633, 1,588, 907, and 816 kg/h for Exp. 1 to 4, respectively. Pellet durability was assessed on all diets except starter diets, which were crumbled, according to published guidelines (ASABE, 2005).

Feed intake and mortality were measured daily. Pen weights were measured daily from d 1 to 7 and weekly thereafter. Individual BW was measured on d 0, 21 (Exp. 3 and 4 only), and 42.

Experiments 1, 2, and 3 were analyzed as a randomized complete block design using the GLM procedures of SAS (SAS Inst. Inc., Cary, NC). Pen was the experimental unit, and placement within room of the facility was the blocking criterion. Experiment 4 was analyzed as a randomized complete block design with a 2 x 2 factorial arrangement of treatments (process and SDP) using GLM procedures. Orthogonal contrasts were used to determine linear and preplanned relationships among treatments. Means were considered significantly different if P < 0.05, whereas trends were reported when P = 0.05 to 0.10.

RESULTS AND DISCUSSION
Thermal processing (pelleting, roasting, expansion, and extrusion) of animal feeds is common as a way to improve growth rate, efficiency of gain, nutrient digestibility, and to improve feed handling (Hussar and Robblee, 1962; Skoch et al., 1983; Fairfield, 1994). Thermal processing has been shown to reduce effectiveness of functional protein ingredients such as enzymes and less stable nutrients such as vitamins (Inborr and Bedford, 1994; Coelho, 2001; Dozier, 2002). Steidinger et al. (2000)demonstrated that pelleting SDP containing pig starter diets at temperatures greater than 77°C resulted in the loss of improvements in performance that was obtained by the addition of SDP to the diets. Spray-dried plasma applied postpelleting or included in the drinking water has been shown to improve growth performance and breast meat yield of broilers (Campbell et al., 2003, 2004; Bregendahl et al., 2005). There are no data evaluating effects of pelleting or expanding broiler feeds on the response to SDP. Objectives of these experiments were to evaluate effects of pelleting temperatures (85, 90, and 95°C) and expanding on the growth response of broilers to dietary SDP.

In Exp. 1, SDP was added to the feed before or after pelleting to determine if pelleting would affect the improvement in growth response associated with SDP as observed in previous research (Campbell et al., 2003, 2004; Bregendahl et al., 2005). Based on comments from a number of nutritionists in the broiler and turkey industry, a pellet conditioning temperature of 85°C was chosen as representative of a typical processing temperature. Spray-dried plasma improved (P < 0.05) growth rate and feed intake for the first 2 phases (1 to 14 d of age, and 15 to 28 d of age; Table 5). There was a tendency (d 15 to 28 of age) for the increase in feed intake associated with SDP to be reduced when SDP was added to the feed before pelleting. Body weight at d 28 of age was improved with addition of SDP (P < 0.01), whereas method of addition (pre- or postpelleting) had no effect on this response. In general, addition of SDP did not affect growth performance beyond d 28, and by d 42 of age, the response to SDP was not significant. Through d 28 of age, the response to SDP (increased daily gain, daily feed intake, and BW) was improved (P < 0.05), and pelleting did not result in consistent loss in the SDP effect.

The second experiment was designed to more closely evaluate the effect of pellet conditioning temperature on the SDP response. In this experiment, pellet conditioning temperatures included 85, 90, and 95°C. In contrast to the data in Exp. 1, the response to SDP was more consistent throughout d 42 of age (Table 6). Overall, SDP improved final BW (P = 0.01), growth rate (P = 0.004), feed intake (P = 0.026), and tended to improve efficiency of gain (P = 0.099). Addition of SDP to the feed before pelleting resulted in improved final BW (P = 0.01) and overall daily gain (P = 0.021). The response to SDP was not affected by increasing pellet conditioning temperatures.

Addition of fat (1%) to the feed before pelleting improves pelleting efficiency as demonstrated by greater production rates (Table 4) observed in the manufacturing of feed of Exp. 1 and 2 compared with those manufactured for Exp. 3 and 4. Presumably, added fat in mash lubricates the pellet die, thus increasing throughput rate but may reduce the effective temperature by reducing friction (Ziggers, 2004). In commercial feed milling varying amounts of fat can be added to mash before pelleting. Therefore, Exp. 3 was designed to maximize the effective pellet conditioning temperatures by adding all supplemental fat postpelleting. In the first 2 experiments, the response to SDP was consistently observed by 21 d of age. Therefore, to simplify the study, Exp. 3 was designed as a 21-d experiment. Pellet conditioning temperatures were 85, 90, and 95°C. Improved (P < 0.001; Table 7) growth rate, feed intake, efficiency of gain, and final BW of broilers fed SDP were noted in Exp. 3. Performance of controls was lower in Exp. 3 compared with other experiments as a result of greater environmental challenge. The SDP response was consistent when added before or after pelleting. Increasing pellet conditioning temperature did not affect the response to SDP even when maximal friction heat was generated by adding all fat postpelleting.

Expanding feed before pelleting improves pellet quality (Fairfield, 1994) and had been shown to further improve growth rate and efficiency of gain (Smith et al., 1995; Fancher et al., 1996). However, exit feed temperatures from an expander are greater than those of a pelleter (Fairfield, 1994). Exp. 4 (21-d study; Table 8) was designed to evaluate the effect of expanding on the response to dietary SDP. In this experiment, treatments were arranged as a 2 x 2 factorial with SDP addition (0 vs. 1%) and feed processing (pelleting vs. expansion followed by pelleting). Addition of SDP to either the pelleted or expanded feed improved daily gain (P = 0.019) and feed intake (P = 0.045). Final BW was improved by expanding the feed (P = 0.046) and by SDP addition (P < 0.001). The only interaction observed was on BW (d 7 of age) when the response to SDP was greater in the pelleted feed compared with that in the expanded feed (P = 0.013).

In summary, thermal processing of feeds typically reduces the effectiveness of functional protein ingredients such as enzymes or less stable nutrients such as vitamins (Inborr and Bedford, 1994; Coelho, 2001; Dozier, 2002). Spray-dried plasma is recognized as a functional protein ingredient (Nelssen et al., 1999; Coffey and Cromwell, 2001). The response to SDP is greater in a high antigen environment compared with a low antigen environment (Coffey and Cromwell, 1995). Steidinger et al. (2000)reported that pellet conditioning temperatures in excess of 77°C in pig starter diets resulted in a loss of SDP-associated improvements in growth performance. In the current experiments pellet conditioning temperatures to 95°C or expansion (to 149°C) of poultry diets (primarily corn and soybean meal diets) did not ameliorate the response to SDP. This demonstrates that the protein(s) in SDP responsible for the improved growth performance in poultry are more resistant to thermal heat processing than other functional protein ingredients or less stable nutrients in the diet matrix. Results of all experiments indicate that neither pellet conditioning temperatures from 85 to 95°C nor expansion processing conditions to 149°C impaired the positive growth-enhancing effects of SDP for broilers fed pelleted or expanded broiler feed.

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Tags · Growth · Broilers · Spray-dried plasma · Pellets · Expanded feed ·

15.02.2008. 13:22