EFFECT OF REPLACING CORN AND SOYBEAN MEAL WITH BREWERS RICE AND DRIED DISTILLERS BREWERS YEAST ON PERFORMANCE OF GROWING-FINISHING PIGS

The objective of this study was to determine the ef fect of replacing corn and Soybean Meal (SBM) with Brewers Rice (BR) and Dried Distillers Brewers Yeast (DDBY), respectively, on ADG, G:F, Apparent Total Tract Digestibility (ATTD), fecal DM output and fecal loss of N and P of growingfinishing pigs. Sixty four Yorkshire x Duroc x Hamp shire crosses (BW = 73±5.7 kg) were randomly assigned to corn/SBM (CSM), BR/SBM (RSM), corn/DDBY (CBY) or BR/DDBY (RBY) diets. Compared with pigs finished on corn based diets, pi gs fed BR based diets gained faster (0.868 vs. 0.730 kg.pig; p<0.01) and had better gain to feed ratio (0.30 v s. 0.25; p<0.01). Pigs finished on RBY diet had the least fecal DM output (0.245, 0.352, 0 .575, 0.639 kg.pig ; p<0.001) and greatest ATTD (91.5, 87.8, 80.0, 77.9%; p<0.001) followed by RSM, CBY and CSM pigs, respectively. Pigs finished on RBY diet lost the least (p<0.001) amount of N (0 .010, 0.013, 0.019, 0.021 kg.pig ) and P (0.010, 0.014, 0.016, 0.019 kg.pig ) in the feces followed by pigs finished on RSM, CB Y and CSM, respectively. In conclusion, BR and DDBY can replac e all corn and SBM in swine diets with no negative effects on performance of growing-finishin g pigs.


INTRODUCTION
Swine diets are generally formulated on least cost basis and to obtain optimal nutrient use and minimize excretion of dietary nutrients.However, some nutrients are utilized less efficiently and are excreted in excess through the feces contributing to environmental pollution.Nitrogen and P are the most significant contributors to environmental pollution although other nutrients such as Ca, K, Cu and Zn are also of concern (Schutte et al., 1993).Dietary nutrients are excreted in excess because they are utilized less efficiently or nutrients supplied in the diet exceed the amounts needed by the animal (Lenis and Schutte, 1990;Kerr, 1995).Approximately 50 to 80% of N and 40 to 80% of P consumed is excreted, a substantial amount through the feces (Yano et al., 1999).Surplus N in manure leaches into ground and surface water, resulting in high nitrate levels in ground water and O 2 depletion by O 2 -depleting plants growing in surface water (Aarnink and Verstegen, 2007).
Modifications of swine diets to replace feedstuffs used less efficiently or the more expensive feedstuffs continue to attract considerable research over the years.Other investigations have looked to include only nutrient amounts in diets to match animal needs; reports show a significant reduction in the excretion of nutrients such as N and P when dietary levels were restricted (Sutton et al., 1999;Cole et al., 2003;Aarnink and Verstegen, 2007).In addition, prices of

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traditional feedstuffs in swine diets, corn and Soy Bean Meal (SBM), continue to rise owing to their alternative uses as renewable energy sources.Alternative but effective energy and protein feedstuffs need to be investigated for their optimal utilization by pigs.Brewers Rice (BR), a by-product of rice processing and Dried Distillers Brewers Yeast (DDBY), a byproduct of beer manufacturing, can be suitable and cheaper alternatives to corn and SBM, respectively.Although BR has a lower energy density compared to corn, its starch is more readily available because of a lower amylose to amylopectin ratio (Goddard et al., 1984) and lower Non-Starch Polysaccharides (NSP) and resistant starch (RS; Berry, 1986).These biochemical differences make BR more digestible than corn because rice contains about 20% amylose compared to more than 25% for corn (Rooney and Pflugfelder, 1986;Bjorck et al., 1994).Literature is lacking on the effect of replacing corn and SBM with BR and DDBY, respectively, on pig performance, fecal DM output and fecal loss of N and P by growingfinishing pigs.We hypothesized that replacing corn and SBM with BR and DDBY, respectively, will increase nutrient utilization (G:F and ATTD) and reduce fecal DM output ,and loss of N and P with out any negative effects on pig productivity.The objectives of this research were to determine the effect of; (1) replacing corn and SBM with BR and DDBY, respectively, on fecal DM output and loss of N and P in growingfinishing pigs and (2) replacing corn and SBM with BR and DDBY, respectively, on ADG, G:F and ATTD of growing-finishing pigs.

MATERIALS AND METHODS
The experiment used growing-finishing managed to meet the recommendations of the University of Arkansas at Pine Bluff (UAPB) Institutional Animal Care and Use Committee.

Animals, Housing and Experimental Design
Animals used in this experiment were a mixture of barrows and gilts of approximately ¾ Yorkshire×⅛ Duroc×⅛ Hampshire breeding.The animals weighed 73±5.7 kg −1 on day 0. Sixteen animals were born and raised on the UAPB Farm while forty eight animals of similar breeding were sourced from a nearby private farm.Experimental animals were housed in semi-open concrete floor pens measuring 2.13×6.26m of which 2.13×2.13m portion is open section and a similar area is under roof.All animals were grouped by weight and randomly assigned to four experimental diets.The design of this experiment was a randomized complete block with each pen consisting of four pigs considered the experimental unit.There were four diet treatments in this experiment, replicated four times, for a total of sixteen pens.This study was conducted between November 2, 2012 and November 30, 2012 and lasted 28 days.

Diets
Experimental diets were mixed at the UAPB Farmusing ingredients sourced locally.The treatment diets were: (1) Corn/Soybean Meal (CSM; control); (2) Brewers Rice/Soybean Meal (RSM); (3) Brewers Rice/dried distillers Brewers Yeast (RBY); and (4) Corn/dried distillers Brewers Yeast (CBY).All diets were formulated to contain 14% CP; dietary Ca and P met the National Research Council (NRC, 2012) recommendations for pigs in this class.Feed was weighed and fed manually to the animals daily at 0900 h.Daily feed amounts offered were based on the daily nutrient requirements for growing-finishing pigs following NRC (2012) recommendations.Animals were fed at 3.7% of BW on a DM basis.Feed intake at this level was calculated to supply adequate nutrients to support maintenance and attain more efficient ADG.The feed amounts were adjusted midway through the experimental period, to match changing animal needs due to increased growth.Drinking water was provided at all times via wall mounted nipple drinkers.

Variables Measured
Variables determined included: ADG, G:F, ATTD, fecal DM output and fecal loss of N and P and feed and fecal N and P. To determine ADG, animals were weighed on days 0, 14 and 28.The ATTD of DM, N and P was the calculated percent difference between intake DM, N and P and fecal DM, N and P. The fecal loss of N and P was calculated from average fecal output excreted during the five days of the sampling period.Fecal DM output was determined by multiplying the average total feces collected by the DM percent of each fecal sample.
Feed and fecal samples were dried and ground to pass through a 2 mm screen using the Wiley mill (Thomas Scientific, Swedesboro, NJ).Ground samples from five sampling days were composited into one sample each.Composite fecal and feed samples were analyzed for DM, N, P, Neutral Detergent Fiber (NDF) Acid Detergent Fiber (ADF) and ash.
Samples for P analysis were digested in nitric acid (HNO 3 ) on a hot block heated to more than 60°C for up Science Publications AJAVS to 1½ h with appearance of reddish smoke signaling that initial digestion was complete.Hydrogen peroxide (H 2 O 2 ) was added at this point and further digestion allowed to continue until about 5 mL of sample was left in the tube.The digested solution was diluted to bring the volume to 25 mL.The diluted sample was run through the Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) analyzer for final determination of P concentration.

Sampling Procedures
Animals were weighed at the start (day 0), day 14 and end of the experiment (day 28).Sub-samples of each feed were placed in a bag and stored in a freezer at-20°C, until further lab analysis.Total feces were collected within each pen during the last five days of the experiment.The feces were collected at the same time, in numerical order starting with the same penevery collection day.All feces were gathered and placed in pre-weighed buckets.Once the weight was determined, the feces were mixed within the bucket and a sub-sample prepared for lab analysis.The fecal sub-samples were stored in a freezer at-20°C, awaiting further lab analysis.During the sampling period the pens were not allowed to be washed down to ensure that all the feces excreted by the pigs during the sampling period were collected.

Statistical Analysis
Data was analyzed as a randomized complete block design, with pen comprising of four pigs as the experimental unit and block based on initial pig BW.All data were subjected to Analysis Of Variance (ANOVA) generated using the GLM procedures of SAS (SAS Inst.Inc., Cary, NC).The error term of pen within diet was used to test the effect of treatments on response variables determined.Treatment differences were considered significant at p<0.05.Least significance difference was used to separate means when a significant F-value for treatment means (p<0.05) was observed in the ANOVA.

RESULTS
Compared to pigs finished on corn based diets, pigs finished on brewers rice based diets gained faster (p<0.01); the protein source had no negative effect on pig ADG (Table 2).Fecal loss of dietary N was reduced (p<0.001) the most for pigs finished on RBY diet and reduced the least for CSM and CBY pigs, RSM pigs were intermediate (Table 3).Response to dietary P was somewhat different; pigs finished on RBY diet had the least (p<0.001)loss of dietary P followed by RSM, CSM and CBY in that order.Consequently, digestibility of dietary N and P was greater (p<0.001) for BR based diet compared with corn based diets.

DISCUSSION
Possible reasons why pigs fed BR based diets had a significant reduction in fecal DM output was probably due to lower NDF and ADF (fiber) levels (Table 1) compared to corn based diets.Fiber has a negative correlation with digestibility and this inverse relationship probably explains why corn with higher fiber content was less digested compared with BR.Greater ATTD for BR based diets meant that less feces was excreted compared to corn based diets.These findings compare favorably with our previous work (Gekara et al., 2013) and those of Yano et al. (1999), although the latter group used chickens in their studies.
Greater ATTD for RBY pigs followed by RSM, CSM and CBY, in that order, may have been due to differences in the concentration of NSP, mainly the cell wall carbohydrates, RS to amylase digestion and other complexes (Englyst et al., 1992;Gallant et al., 1992;Brown, 1996).Brewers rice based diets probably had a lower amylose (Goddard et al., 1984), NSP and RS (Berry, 1986) concentration making BR more digestible than corn based diets.Regular rice contains about 20% amylose compared to more than 25% for corn (Bjorck et al., 1994;Rooney and Pflugfelder, 1986).
The significant reduction in the fecal loss of N and P may have been due to differences in ATTD and dietary NDF and ADF.Brewers rice based diets had a greater N and P digestibility and lower levels of NDF and ADF compared with corn based diets.Fiber (mainly ADF) and digestibility are negatively correlated, thus, the significantly lower ADF levels in RBY and RSM diets compared with CSM and CBY diets probably explains the corresponding differences in animal response.Furthermore, a probable more favorable N to P ratio (Bjorck et al., 1994;French, 1973) in BR based diets compared with corn based diets may have resulted in greater digestibility and lower excretion of N and P in the feces.Additional research should determine the extent of N and P bound to NSP and how this affects availability of N and P in corn and BR relative to utilization in swine.

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A better gain to feed ratio for pigs fed BR based diets compared with corn can be attributed to greater ADG since feed intake was the same across diets.Although intake of N and P was greater for pigs fed BR based diets, pigs fed corn based diets excreted more N and P in the feces.Diet modification BR and replaced corn and SBM, respectively, may have resulted in greater N and P digestibility and reduced excretion in the feces.

Implications
Results of this study further confirm that diet modification to include highly digestible plant based feedstuffs remains a viable option that can reduce excessive excretion of feed nutrients, notably N and P. Furthermore, significant reduction in fecal N and P is a boon and adds value to efforts aimed at reducing environmental pollution caused by manure generated through intensive swine and poultry operations.

CONCLUSION
Brewers rice and dried distillers brewers yeast can replace all corn and soybean meal, respectively, in diets for growing-finishing pigs and reduce fecal DM output and fecal loss of N and P with no negative effects on animal growth and productivity.In this study, brewers rice/dried distillers brewers yeast based diets may have provided animals with highly digestible nutrients and less manure, contributing to reduced environmental pollution.However, the superior performance of brewers rice and dried distillers brewers yeast over corn and soybean meal, respectively, may need further investigation to determine the effect of diet on carcass quality and other characteristics including eating attributes.

Table 2 .
Average daily gain, fecal output, apparent total tract digestibility and feed efficiency ofgrowing-finishing pigs Treatment 1

Table 3 .
Intake and digestibility of N and P in growing-finishing pigs Treatment 1 Treatments: CSM = Corn/Soybean Meal; RSM = brewers Rice/Soybean Meal; CBY = Corn/dried distillers Brewers Yeast; RBY = brewers Rice/dried distillers Brewer's Yeast a-d; Means within a row with different superscripts differ (p<0.05)