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Small Ruminant Research 72 (2007) 92–95 Partial replacement of barley grain for corn grain: Associative effects on lambs’ growth performance S.G. Haddad , R.E. Nasr Department of Animal Production, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110, Jordan Received 28 July 2006; received in revised form 5 August 2006; accepted 9 August 2006 Available online 11 September 2006 Abstract Our objective was to study the positive effects of partial replacement of barley grain for corn in high concentrate diets on growth performance of growing lambs, and to determine the minimum amount of corn needed to produce such effects. Thirty-three male Awassi lambs weaned at 60 days of age were divided into three groups of 11 according to their live weight and offered three isonitrogenous diets. The control diet (B) contained 81 and 14% barley grain and wheat straw, respectively (DM basis). Corn grain replaced barley grain at 10 and 20% of dietary DM for low (LC) and high (HC) corn diets, respectively. Barley had a higher (P < 0.05) rate of digestion (11.5%/h) compared with corn (8.3%/h). The in vitro 30-h digestion extent was also higher (P < 0.05) for barley. The digestion rate for the B diet was higher (P < 0.05) compared with the HC diet, whereas the value for the LC diet was intermediate. Lambs fed LC and HC diets consumed more (P > 0.05) DM (average = 855 g/day) compared with lambs fed B diet (757 g/day). DM and CP digestibilities were similar among diets and averaged 67.0 and 64.2%, respectively. Final BW, BW change and average daily gain (ADG) for lambs fed HC were higher (P < 0.05) compared with B and LC. Moreover, lambs that consumed LC tended (P = 0.12) to grow faster than lambs fed B. Feed to gain ratio was lower (P < 0.05) for lambs fed HC (4.6) compared with B and LC (5.2). In summary, positive associative effects of partial replacement of barley with corn in high concentrate diets for fattening sheep were detected. However, a minimum of 20% replacement of dietary DM from barley with corn was needed to positively improve both performance and feed efficiency. © 2006 Elsevier B.V. All rights reserved. Keywords: Corn; Barley; Associative effects; Awassi 1. Introduction Management practices to improve growth perfor- mance of weaned ruminants include manipulating feed so that digestion is neither too rapid, which can result in digestive disorders, nor too slow, which can result in poor feed efficiency (Cheng et al., 1991). Small cereal grains such as barley are more rapidly and thor- oughly fermented in the rumen than corn; which can Corresponding author. Tel.: +962 2 7201000; fax: +962 2 7095069. E-mail address: [email protected] (S.G. Haddad). result in greater microbial protein synthesis (Feng et al., 1995). However, excessive fermentable carbohydrates from barley can also lead to negative associative effects (Mould et al., 1983). Therefore, feeding a mixture of rapidly (e.g., barley) and slowly digested cereal grains (e.g., corn) may reduce the incidence of acidosis and yield a favourable balance of starch digestion in the rumen and postruminal tract to improve feed efficiency as compared with diets based primarily on one type of grain or the other (Mendoza et al., 1990). In the Middle Eastern areas, because of low pasture availability, diets for growing ruminants are based on concentrates. Barley and corn are the main cereal grains 0921-4488/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.smallrumres.2006.08.005

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Small Ruminant Research 72 (2007) 92–95

Partial replacement of barley grain for corn grain:Associative effects on lambs’ growth performance

S.G. Haddad ∗, R.E. NasrDepartment of Animal Production, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110, Jordan

Received 28 July 2006; received in revised form 5 August 2006; accepted 9 August 2006Available online 11 September 2006

Abstract

Our objective was to study the positive effects of partial replacement of barley grain for corn in high concentrate diets on growthperformance of growing lambs, and to determine the minimum amount of corn needed to produce such effects. Thirty-three maleAwassi lambs weaned at 60 days of age were divided into three groups of 11 according to their live weight and offered threeisonitrogenous diets. The control diet (B) contained 81 and 14% barley grain and wheat straw, respectively (DM basis). Corngrain replaced barley grain at 10 and 20% of dietary DM for low (LC) and high (HC) corn diets, respectively. Barley had a higher(P < 0.05) rate of digestion (11.5%/h) compared with corn (8.3%/h). The in vitro 30-h digestion extent was also higher (P < 0.05)for barley. The digestion rate for the B diet was higher (P < 0.05) compared with the HC diet, whereas the value for the LC diet wasintermediate. Lambs fed LC and HC diets consumed more (P > 0.05) DM (average = 855 g/day) compared with lambs fed B diet(757 g/day). DM and CP digestibilities were similar among diets and averaged 67.0 and 64.2%, respectively. Final BW, BW changeand average daily gain (ADG) for lambs fed HC were higher (P < 0.05) compared with B and LC. Moreover, lambs that consumed

LC tended (P = 0.12) to grow faster than lambs fed B. Feed to gain ratio was lower (P < 0.05) for lambs fed HC (4.6) comparedwith B and LC (5.2). In summary, positive associative effects of partial replacement of barley with corn in high concentrate dietsfor fattening sheep were detected. However, a minimum of 20% replacement of dietary DM from barley with corn was needed topositively improve both performance and feed efficiency.© 2006 Elsevier B.V. All rights reserved.

Keywords: Corn; Barley; Associative effects; Awassi

1. Introduction

Management practices to improve growth perfor-mance of weaned ruminants include manipulating feedso that digestion is neither too rapid, which can resultin digestive disorders, nor too slow, which can result

in poor feed efficiency (Cheng et al., 1991). Smallcereal grains such as barley are more rapidly and thor-oughly fermented in the rumen than corn; which can

∗ Corresponding author. Tel.: +962 2 7201000; fax: +962 2 7095069.E-mail address: [email protected] (S.G. Haddad).

0921-4488/$ – see front matter © 2006 Elsevier B.V. All rights reserved.doi:10.1016/j.smallrumres.2006.08.005

result in greater microbial protein synthesis (Feng et al.,1995). However, excessive fermentable carbohydratesfrom barley can also lead to negative associative effects(Mould et al., 1983). Therefore, feeding a mixture ofrapidly (e.g., barley) and slowly digested cereal grains(e.g., corn) may reduce the incidence of acidosis andyield a favourable balance of starch digestion in therumen and postruminal tract to improve feed efficiencyas compared with diets based primarily on one type of

grain or the other (Mendoza et al., 1990).

In the Middle Eastern areas, because of low pastureavailability, diets for growing ruminants are based onconcentrates. Barley and corn are the main cereal grains

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3. Results and discussion

The experimental diets were isonitrogenous (Table 1).Although ME concentration is higher for corn, replacing

Table 1Ingredient and chemical compositions of the experimental diets

Item Diet

B LC HC

Ingredient (% of DM)Wheat straw, chopped 14.0 14.0 14.0Corn graina, coarsely ground 0.0 10.0 20Barley grainb 81.4 71.2 61Sodium bicarbonate 1.0 1.0 1.0Salt 0.9 1.0 1.0Limestone 0.5 0.5 0.5Urea 1.7 1.8 2.0Mineral and vitamin mixc 0.5 0.5 0.5

Chemical compositionDry matter (%) 93.0 92.7 92.4Nitrogen (% of DM) 2.6 2.6 2.6Neutral detergent fiber (% of DM) 25.8 25.1 24.4Metabolizable energy (Mcal/kg)d 2.74 2.74 2.75

Cost ($/t) 118 126 134

a Cost = 165$/t; based on the average market price for 6 months priorto this experiment.

b Cost = 105$/t; based on the average market price for 6 months prior

S.G. Haddad, R.E. Nasr / Smal

n the diets of growing ruminants. The price of corn isypically 50–80% greater than that of barley because allorn is imported and barley is produced locally. There-ore, using diets with high proportions of corn will note economically competitive with diets high in barleyHarb and Habbab, 1989).

Much research conducted dealing with mixtures ofifferent cereal grains to enhance feed efficiency hasealt with relatively high proportions of the grain addedr substituting rather the minimal amount needed toroduce the desired associative effect. Therefore, ourbjective was to study the positive effects of partialeplacement of barley grain with corn in a high con-entrate diet on growth performance of growing lambs,nd to determine the minimum amount of corn neededo produce such effects.

. Materials and methods

.1. Animals and diets

Thirty-three male Awassi lambs weaned at 60 days of ageere divided into three groups of 11, according to their liveeight, housed in individual pens (1.5 m × 0.75 m) and offered

hree isonitrogenous experimental diets. Lambs were allowedweek for adjustment before receiving the experimental diets.he control diet (B) contained 81 and 14% whole barley grainnd chopped wheat straw, respectively (DM basis). Coarselyround corn grain replaced barley grain at 10 and 20% ofietary DM for low corn (LC) and high corn (HC) diets, respec-ively, as shown in Table 1.

Experimental diets were mixed manually on a weekly basisnd sampled upon mixing. The experiment lasted for 12 weeks.ambs were offered the experimental diets twice daily at 09:00nd 15:00 h in amounts to ensure 10% orts. Amounts of feedffered and refused were recorded daily. Animals were main-ained at ambient temperature and natural daylength. Cleanrinking water was available in plastic buckets.

At day 70 of the experiment, 15 lambs (five lambs/reatment) were selected randomly for the digestibility deter-

ination. Total fecal collection was carried out for 6 days usingecal bags. Total fecal output for each animal was weighed and20% sample was removed for further analysis. Samples of

ndividual ingredients, diets and feces were oven dried at 60 ◦C,round through a 1 mm screen and analyzed for nitrogen byrocedures of AOAC (1990) and neutral detergent fiber (NDF)ccording to Van Soest et al. (1991). Metabolizable energyME) contents of the experimental diets were calculated usingabular values (NRC, 1985).

.2. In vitro digestive kinetics

In vitro digestion kinetics of barley and corn grains as wells the experimental diets were measured using the procedurehat was modified from Tilley and Terry (1963) as described

ant Research 72 (2007) 92–95 93

by Harris (1970). Grains and diets were ground through a 2-mm screen. Samples (0.5 g) were incubated at 38 ◦C in tubescontaining 30 ml of McDougal’s buffer and 7 ml of ruminalfluid. Tubes were placed in a chamber incubator and swirledevery 4 h. Ruminal fluid was collected from a ruminally fis-tulated dairy cow fed a 50% forage and 50% concentratediet. Triplicate tubes for each grain and diet and one blanktube at each time were incubated for 0, 2, 4, 6, 9, 12, 18, 24and 30 h.

Microbial fermentation was stopped by cold-shocking thetubes in ice water for 30 min. Tubes were centrifuged at 500 × gfor 15 min, and the supernatant was decanted and dried in aforced-air oven at 60 ◦C. Digestion kinetics estimates werecalculated according to Bowman and Firkins (1993). The pro-cedure was replicated three times.

2.3. Statistical analysis

Means for diet effects were analyzed as a completely ran-domized design using the general linear model procedureof SAS (1991). Differences among treatment means weredetected by least significant difference (LSD) of SAS (1991).

to this experiment.c Supplies per kilogram of feed: 4.9 mg of Zn, 4.05 mg of Mn,

0.45 mg of Cu, 0.075 mg of I, 0.1 mg of Se, 2500 IU Vitamin A, 400 mgof Vitamin D, 2.5 IU Vitamin E.

d Calculated using tabular values (NRC, 1985).

94 S.G. Haddad, R.E. Nasr / Small Ruminant Research 72 (2007) 92–95

Table 2In vitro digestive kinetics of barley and corn grains and the experimen-tal diets

Lag time(h)

Digestionrate (%/h)

30-h digestionextent (%)

GrainBarley 1.2 b 11.5 a 72.5 aCorn 2.0 a 8.3 b 60.4 bS.E. 0.1 1.3 1.7

Diet1

B 1.4 10.3 a 63.5 aLC 1.5 9.8 a,b 60.8 bHC 1.7 9.2 b 59.9 bS.E. 0.2 0.4 1.2

Table 3Nutrient intake and digestibility and growth performance of Awassilambs fed on the experimental diets

Diet1

B LC HC S.E.

Intake (g/day)Dry matter 757 b 857 a 854 a 24Crude protein 121 b 137 a 137 a 14Neutral detergent fiber 196 215 210 16Metabolizable energy(Mcal/day)

2.08 b 2.40 a 2.40 a 0.2

Digestibility (%)Dry matter 68.0 65.3 67.7 2.0Crude protein 64.4 62.5 65.7 2.7Neutral detergent fiber 38.1 b 45.2 a 43.5 a 2.5

Initial body weight (kg) 18.7 18.5 18.7 0.6Final body weight (kg) 31.1 b 32.2 b 34.3 a 1.1Weight change (kg) 12.4 b 13.7 b 15.6 a 1.0Average daily gain (g/day) 148 b 164 b 186 a 6.2Feed to gain ratio 5.2 a 5.2 a 4.6 b 0.3Feed cost/kg weight gain

($)0.61 0.65 0.61

S.E.: standard error; a and b: means in a column with different lettersdiffer (P < 0.05, grain type).

barley with corn by 10 and 20% of the diet DM did notgreatly affect the diet ME concentration. However, thisreplacement increased the cost of the diets as shown inTable 1.

Barley had a higher (P < 0.05) rate of digestioncompared with corn (Table 2). This is consistent withthe findings of many researchers (Kung et al., 1992;Hadjipanayiotou, 2004). The digestion rate of barleywas similar to that observed by Surber and Bowman(1998). The in vitro 30-h digestion extent was also higher(P < 0.05) for barley. This is consistent with Feng et al.(1995) who observed similar differences in 32-h in vivoDM disappearance between corn and two different vari-eties of barley.

The digestion lag time was similar (P > 0.05) amongthe three diets (Table 2). However, the digestion rate forB was higher (P < 0.05) compared with HC, whereas thevalue for LC was intermediate. The 30-h digestion extentfor LC and HC diets was lower (P < 0.05) than observedfor B.

Lambs fed the LC and HC diets consumed more(P < 0.05) DM, CP and ME compared with lambs fed B(Table 3). Effects of mixing grains with different rates ofdigestion in high concentrate diets on DM intake havenot been consistent. For example, Stock et al. (1987)observed a positive response in DM intake for steers bymixing high moisture corn and dry rolled corn comparedwith high moisture corn alone. High moisture corn diges-tion rate is 200% faster than dry rolled corn (Mendozaet al., 1990). On the other hand, no differences in DMintake were observed in beef cattle fed high concentrate

diets based on corn or barley (Martin-Orue et al., 2000)or their mixtures (Surber and Bowman, 1998). A com-mon sign of acidosis with high concentrate diets is areduction in DM intake (Mendoza et al., 1999). In the

S.E.: standard error; a and b: means in a row with different letters differ(P < 0.05).

current study, the inclusion of corn grain as low as 10%of the diet DM may have improved ruminal conditionsand thereby improved DM intake.

Dry matter and CP digestibilities were similaramong diets and averaged 67.0 and 64.2%, respectively(Table 3), although the in vitro 30-h digestion extent washigher for the B diet. Likewise, Surber and Bowman(1998) observed lower ruminal starch digestion for cornthan for barley. However, differences among diets inthe current experiment in the amount of starch escapingruminal fermentation would have been relatively smallbecause of the low levels of corn being substituted forbarley.

The NDF digestibility for the LC and HC diets washigher (P < 0.05) than for B (Table 3). This differencewas probably due to the less favorable ruminal conditionswith B, such as pH, for optimum fiber digestion. In thisregard, ruminal VFA concentration was higher in steersfed high barley diets compared with ones based on cornwith lower ruminal pH for barley (Surber and Bowman,1998). Haddad et al. (1995) observed an increased lagtime and decreased rate of digestion of wheat straw fiberwith low ruminal pH. Grant (1994) examined the inter-actions of starch fermentatability and pH on kinetics and

apparent extent of ruminal NDF digestion using differentforage sources and concluded that the higher the starchfermentability the lower the rate of NDF digestion of theforages studied.

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Final BW, BW change and average daily gain (ADG)or lambs fed the HC diet were higher (P < 0.05) thanor B and LC (Table 3). Moreover, lambs that consumedhe LC diet tended (P = 0.12) to grow faster than lambsed the B diet. Feed to gain ratio (DM consumed to liveeight gained) was lower (P < 0.05) for lambs fed theC diet compared with lambs fed the B and LC diets.lthough the factors responsible for improved perfor-ance with the HC diet were not specifically addressed

n this experiment, the most likely ones are elevateduminal pH (McCarthy et al., 1989) and greater rumi-al outflow of starch (Mendoza et al., 1999).

. Conclusion

Positive associative effects of partial replacement oforn for barley in high concentrate diets for fatteningheep were detected. A minimum of 20% replacementf dietary DM from barley with corn was needed to pos-tively improve both performance and feed efficiency.

cknowledgement

The help of the farm staff at the Jordan University ofcience and Technology is greatly appreciated.

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