Carbadox

Abstract

Two experiments using 415 weanling pigs (4.8 ± 0.98 kg and 14 ± 4 d of age) were conducted to determine the effect of increasing dietary niacin on pig performance. Pigs were blocked by BW and randomly allotted to one of five dietary treatments. There were five pigs per pen with seven pens per treatment in Exp. 1, and eight pigs per pen with six pens per treatment in Exp. 2. Diets were fed in four phases (d 0 to 4, 4 to 8, 8 to 22, and 22 to 35). Pigs were fed the control diet with no added niacin or the control diet with 28, 55, 83, or 110 mg/kg of added niacin; data from both trials were combined. From d 0 to 22, increasing niacin had no effect (P>0.10) on growth performance. From d 22 to 35, increasing niacin had no effect (P>0.10) on ADG or ADFI, but improved (linear, P0.10) on ADG or ADFI, but tended to numerically (linear, P

(Key Words: Niacin, Nursery, Pigs.)

Introduction

Niacin has long been accepted as an essential vitamin in swine diets; however, the optimal amount to include has been a matter of considerable debate. Luecke et al. (1947) reported that pigs fed diets low in tryptophan require niacin

supplementation. Even so, niacin deficiency in pigs is unlikely due to the conversion of excess tryptophan to niacin (Firth and Johnson, 1956). Moreover, March (1979) suggested that B vitamins could be synthesized by the microflora of the gut as well. Harmon et al. (1969) reported that supplementing corn-soybean meal diets with niacin for growing pigs did not improve growth performance. Yen et al. (1978) reported no growth benefit when adding niacin to finishing pig diets. Ivers and Veum (1993) reported no benefit when supplementing low protein diets with crystalline niacin in nursery, growing, or finishing pigs. In contrast, Hamilton et al. (1989) observed improvements in growth performance when pigs were fed up to 100 mg/kg of additional niacin.

Although there have been conflicting reports regarding the growth benefits of added niacin, researchers and feed manufacturers continue to support inclusion of niacin in swine diets. A survey of feed manufacturers and university researchers regarding vitamin recommendations showed that average recommended niacin inclusion was 43 mg/kg (BASF, 1997). The average of the 25% greatest inclusion rates was 67 mg/kg, and the average of the least 25% was 25 mg/kg.

Indeed, vitamin requirements are influenced by many factors including health status, previous nutrition, vitamin concentrations, availabilities of ingredients in the diet, and level of metabolic precursors in the diet. However, because of the disparity in inclusion rates recommended by university research and what is used in the commercial feed industry, it is necessary to evaluate the effects on growth across a broad range of niacin inclusion rates. The objective of this study was to determine the influence of several rates of added dietary niacin on weanling pig performance.

Materials and Methods

General. The experimental protocols in these experiments were approved by the Kansas State University Animal Care and Use Committee. Two experiments were conducted to determine the influence of increasing niacin in nursery pig diets on growth performance. The first was conducted at the Kansas State University Segregated Early Weaning Research Facility, and the second was conducted on a commercial farm in Northeast Kansas. Niacin from niacinamide (Lonza, Inc., Fair Lawn, NJ) was added to a basal diet to achieve concentrations of 28, 55, 83, or 110 mg/ kg added dietary niacin. The same diet formulations were used in both experiments, but because of the time interval between the two studies, different batches of ingredients were used. all feed was manufactured at the Kansas State University Feed Mill. Samples of each diet from both experiments were analyzed for total niacin content (University of Missouri Experiment Station Chemical Laboratories, Columbia).

Experiment 1. One hundred seventy-five barrows and gilts (Line C22, PIC, Franklin, KY; initially 4.9 ± 0.91 kg, 16 ± 2 d of age) were housed in the Kansas State University Segregated Early Weaning Facility. The temperature in the nursery was initially 32°C and was reduced no more than 2.5°C each week there after. Pigs were transported from the sow farm immediately postweaning to the research farm. Each pen was equipped with a four-hole stainless steel feeder and a nipple waterer to provide ad libitum access to feed and water. Pigs were blocked by initial BW to seven replicate pens per treatment with five pigs per pen. There were four replications with 3 barrows and 2 gilts per pen and three replications with 3 gilts and 2 barrows per pen. Pens were randomly allotted to one of five dietary treatments (O, 28, 55, 83, or 110 mg/kg of added niacin).

Diets in this experiment were fed and formulated to be similar to a commercial phase feeding program and were fed in four phases. From d O to 4, pigs were fed a complex diet (high in dried whey and other specialty protein sources) formulated to 1.70% total lysine and 0.31% tryptophan (Table 1). From d 4 to 8, pigs were fed a less complex diet containing 1.60% total lysine and 0.29% tryptophan. From d 8 to 22, pigs were fed a diet formulated to 1.40% total lysine and 0.25% tryptophan. Finally, pigs were fed a simple corn-soybean meal-based diet formulated to 1.30% total lysine and 0.26% tryptophan from d 22 to 35. The first three diets contained 55 mg/kg of carbadox, and the last diet contained 28 mg/kg of carbadox. Zinc oxide was added at 3000 mg/kg in the first two diets, and 2000 mg/kg were included from d 8 to 22. The first two diets were conditioned to 6O0C and then pelleted through a 4-mm die; the last two diets were fed in meal form. Pigs and feeders were weighed on d O, 4, 8, 22, and 35 to calculate ADG, ADFI, and gain:feed ratio (G:F).

Experiment 2. Two hundred forty barrows and gilts (initially 4.6 ± 1.05 kg, 12 ± 2 d of age) were housed in three nursery rooms on a commercial farm in Northeastern Kansas. Each room housed two blocks of pigs. Pigs (Line 337 × C22; PIC) were blocked by initial BW to six replicate pens per treatment with eight pigs (four barrows and four gilts) per pen. Pens were randomly allotted to treatments, which were the same as in Exp. 1. Temperature was initially 32°C and decreased no more than 2.5°C weekly. Similar to Exp. I, pigs and feeders were weighed on d O, 4, 8, 22, and 35 to calculate ADG, ADFI, and G:F.

Statistical Analysis. Data from both experiments were analyzed with pen as the experimental unit in a randomized complete block design. No trial × treatment interactions were observed, and the data were pooled. Analysis of variance was performed using the PROC MIXED procedure of SAS® (SAS Inst., Cary, NC) with trial as a random effect. Linear and quadratic polynomials for increasing dietary niacin were also evaluated.

Results and Discussion

Analyzed total niacin concentrations were 20.7, 19.5, 22.6, and 22.8 mg/kg in the basal diets fed from d O to 4, 4 to 8, 8 to 22, and 22 to 35, respectively (Table 2). Luce et al. (1967) reported that niacin in corn is unavailable to pigs, but Yen et al. (1977) reported that niacin in soybean meal is highly available for chicks, and probably just as available for pigs. Assuming 100% bioavailability of niacin in the diet, excluding that from corn, each basal diet would provide 12.8, 10.0, 10.8, and 9.2 mg/kg of available niacin. Furthermore, Firth and Johnson (1956) suggested that pigs could convert every 50 mg of excess tryptophan to 1 mg of niacin. The tryptophan concentrations in our diets (0.30, 0.29, 0.25, and 0.26 in each dietary phase, respectively) were calculated based on NRC (1998) estimates for individual ingredients. The potential niacin synthesis from the excess tryptophan in the basal diet would provide 7.2, 3.6, 2.4, and 10.0 mg/kg of niacin in each phase, respectively. This, along with the available niacin in the basal diet, would provide 19.9, 13.6, 13.2, and 19.2 mg/kg of available niacin in each phase, respectively. The niacin concentrations of the first three diets are similar to the niacin requirement (20.0, 15.0, and 12.5 mg/kg) published by the NRC (1998). The basal diet fed during the final phase was calculated to provide much greater levels of available niacin (19.2 mg/kg) than the requirement estimate suggested by the NRC (1998; 10.0 mg/kg), which is due to the greater amount of soybean meal used in the last phase compared with the earlier dietary phases.

From d O to 8 and 8 to 22, increasing dietary niacin had no effect (P>0.10) on ADG, ADFI, or G:F (Table 3). From d 22 to 35, again there were no differences (P>0.10) in ADG or ADFI among treatments. However, increasing added dietary niacin increased (linear, P0.10) on ADG or ADFI. However, increasing dietary niacin tended (linear, P

Hamilton et al. (1989) reported improvements in growth performance when feeding up to 100 mg/kg of added dietary niacin to nursery pigs. The authors fed diets formulated to the requirement estimates published by the NRC (1988) at 0.14% tryptophan. Based on data evaluating the tryptophan requirement of 6- to 16-kg pigs (0.19%; Burgoon et al., 1992), there should have been very little conversion of niacin from tryptophan. Ivers and Veum (1993) reported no benefits in growth performance when adding crystalline niacin to low protein diets. Recently, Real et al. (2002) observed 28 to 55 mg/kg of added niacin to improve growth performance of growingfinishing pigs, and 110 to 550 mg/ kg to improve longissimus pH, drip loss, and color scores.

There have been several studies that reported improvements in growth performance when adding several B vitamins (niacin, riboflavin, pantothenic acid, and vitamin B12) to nursery pig diets (Wilson et al., 1991, 1993; Stahly et al., 1996). However, conclusions cannot be drawn as to which of these vitamins elicited the response or whether or not niacin had a role in the responses observed.

Diets high in dried whey and other specialty protein sources fed immediately after weaning appear to provide enough niacin to support maximum growth performance in early weaned nursery pigs. However, it appears that as pigs are switched to less complex, corn-soybean meal-based diets, added niacin is needed to maximize G:F. Assuming none of the niacin from corn is available to the pig, in our diets approximately 50% of the niacin is provided by soybean meal, and 50% is provided form the conversion of tryptophan. Because the basal diet fed from d 22 to 35 was calculated to contain approximately twice the pig's niacin requirement, this may suggest that the niacin availability in soybean meal is less than previously estimated and(or) perhaps we did not have as much excess tryptophan based on NRC (1998) estimates. The linear improvements in G:F we observed from d 22 to 35 appear to be the result of numerically (P>0.10) increased ADG and decreased ADFI of pigs fed 83 and 110 mg/kg of added niacin. The linear improvement in G:F observed during the final 2 wk of the study was also large enough to result in a tendency for an overall (d O to 35) improvement in G:F.

Implications

Increasing added dietary niacin had no effect on ADG or ADFI in early weaned pigs. However, in the late nursery phase (d 22 to 35 after weaning), adding up to 110 mg/kg of niacin linearly improved G:F. This improvement in G:F corresponds to when pigs were switched from diets containing dried whey and other specialty protein sources to a corn-soybean meal-based diet. Therefore, it would appear that although calculated to be adequate to meet the pig's requirement estimate, added niacin up to 110 mg/ kg was necessary to maximize G:F.

1 Contribution no. 02-2-J from the Kansas Agric. Exp. Stn., Manhattan 66506.

2 The authors thank Lonza, Inc. (Fair Lawn, NJ) for partial financial support as well as for providing the niacin used in these experiments. The authors also thank Eichman Bros. Farm (St. George, KS) for use of their facilities and animals used in Exp. 2.

Literature Cited

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D. E. REAL*, J. L NELSSEN*, M. D. TOKACH*, R. D. GOODBAND*,3, PAS, S. S. DRITZ,* J. M. DEROUCHEY,* B. W. JAMES,* and E. ALONSO[dagger]

* Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506-0201 and [dagger] Lonza, Inc., Fair Lawn, NJ 07410

3 To whom correspondence should be addressed: Coodband@ksu.edu

Copyright American Registry of Professional Animal Scientists Aug 2004
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