Livestock Research for Rural Development 26 (9) 2014 Guide for preparation of papers LRRD Newsletter

Citation of this paper

Growth performance of ruminants fed different proportions of maize and sorghum grain

S Ncube, L R Ndlovu1, B Tavirimirwa, G Tambo, R Mwembe and G B Nyamushamba2

Department of Research and Specialist Services, Matopos Research Institute P Bag k5137, Bulawayo, Zimbabwe
shadreck_ncube@yahoo.com
1National University of Science and Technology, P.O. Box AC 939, Ascot Bulawayo, Zimbabwe
2Faculty of Agriculture, Women’s University in Africa, P O Box MP 1222, Harare, Zimbabwe

Abstract

Two experiments were conducted to determine the effect of combining maize and sorghum grain high in soluble proanthocyanidins (PAs) (3.466 A550/g sample) on steer and wether feed intake, digestibility, growth and feed conversion ratio. The first experiment assessed the effects of combining maize and sorghum grain high in PAs (3.47 A550/g sample) on intake and digestibility of the diets fed to wethers. Twenty five Dorper wethers (mean initial bodymass 37.3 5.3 kg) of 18 months of age were stratified by initial weight then randomly allotted to five diets in a complete randomised design within each body mass group with 5 replicates per group and were fed one of the following diets:100% maize (100M); 75% maize and 25% sorghum (75M:25S); 50% maize and 50% sorghum (50M:50S); 25% maize and 75% sorghum (25M:75S); 100% sorghum (100S). In the second experiment the effect of combining maize and sorghum grain on feedlot performance was evaluated. Thirty steers (12 months old) were allotted to 5 pens. The composition of the diets was as described in Trial 1.

 

 Feed intake of the wethers was not affected by the treatments.  Digestibility of dry matter (DM), organic matter (OM), neutral detergent fibre (NDF) and acid detergent fibre (ADF) ranked 50M:50S>100M>75M:25S>25M:75S>100S.  The feed conversion of the steers was similar on all diets, but those fed the sorghum diet had greater average daily gains than those fed maize. Carcass traits were not affected by grain type. Results from this study indicate that sorghum grain is useful as a source of energy in pen fattening diets.

Keywords: digestibility, feedlot, intake, steers


Introduction

In Zimbabwe the standard high energy diet for pen fattening ruminant animals is based on maize, which is a major expense in livestock finishing rations. The increase in human population coupled with the decrease in maize output, has resulted in increased competition between humans and livestock for maize (Deepak et al 2013). Although sorghum grain is also a source of energy, it has not been routinely used because it has been considered less efficient than maize because of its highly variable chemical composition and feeding value (Manor 1987). The low feed efficiency of sorghum grain has been attributed to environmental factors (Brouk 2010), differences between varieties (Dykes and Rooney 2006) and presence of secondary compounds (mainly condensed tannins) (Rooney et al 2005).

 

The presence of secondary compounds (proanthocyanidin [PAs]) leads to reduced intake, dry matter and protein digestibility of sorghum grain. Sorghum varieties with pigmented testa layer such as brown sorghums (bird resistant) have high tannin compounds compared to non-pigmented varieties ( Dykes and Rooney 2006; Rooney et al 2005). Despite these limitations sorghum grain offers potential to serve as a substitute for maize in high energy diets for ruminants (Brouk 2010). The cereal is more suitable in drought prone areas of the country as it is more drought tolerant than maize. Improved animal performance has been observed when sorghum has been combined with maize in pen fattening diets (Larrain et al 2009; Ncube et al 2001; Smith et al 1992).

 

This research sought to examine the effect of combining maize and sorghum grain high in soluble PAs on steer and wether feed intake, digestibility, growth and feed conversion.


Materials and methods

Two experiments were conducted at Matopos Research Institute. The first assessed the effects of combining maize and sorghum grain high in soluble proanthocyanidins (PAs) (3.47 A550/g sample) on intake and digestibility of the diets fed to lambs. The second evaluated the effect of combining maize and sorghum grain on steer growth performance with the following specific parameters of interest: feed intake, digestibility, growth and feed conversion.

 

Composition of the diets                                  

 

Nitrogen (N) content was similar for all treatments (Table 1). Acid-detergent fibre (ADF) was greatest with sorghum-based diets. Proanthocyanidins were generally low in all treatments compared to literature values (Boren and Waniska 1992). The calculated metabolizable energy (ME) was similar across treatments.

 

Trial 1

 

Animals, housing and treatments

 

Twenty four Dorper wethers (mean initial bodymass 37.3 5.3 kg) of  18 months of age were stratified by weight then randomly allocated to the five diets in a complete randomised design within each body mass group with 5 replicates per treatment, except for one treatment which had four replicates due to damage of the crate. The five treatments consisted of the following diets based on differing proportions of maize and sorghum grain containing soluble PAs  of 3.47A550/g sample:

 

100M: 100 per cent maize based diet

75M:25S: 75 per cent maize and 25 per cent sorghum

50M:50S: 50 per cent maize and 50 per cent sorghum

25M:75S: 25 per cent maize and 75 per cent sorghum

100S: 100 per cent sorghum based diet

 

The composition of the diets is shown in Table 1.  The sorghum grain (cultivar Mutode) was grown at Matopos Research Institute, while maize (variety, SC501) was sourced from one farmer.

 

Feed was offered ad libitum twice a day, at 0800 and 1400 hours. Wethers were housed individually in metabolism crates so each animal was considered an experimental unit (replication). Intake, digestibility and N retention were measured over seven days following a 21-day adjustment period. Total collection of faeces was made to enable measurement of the digestibility of DM, OM, NDF and ADF. Daily collection of faeces was weighed, mixed thoroughly and a 10 per cent subsample taken and stored at -200C pending analysis. Total urine collection was also done for nitrogen retention determination. Urine was collected daily, sub-sampled and stored at -200 C pending analysis. Urine was preserved with 20 millilitres of 25 % sulphuric acid (3:1 H2O: H2SO4, v/v).

 

Trial 2

 

Animals, housing and feeding

 

Thirty crossbred steers (mean initial bodymass 24315.9 kg) of about 12 months of age were randomly allocated to five treatments in a complete randomized design (CRD) with six replicates per treatment. The compositions of the diets were as described in Trial 1.

 

The steers were housed individually and each was considered an experimental unit. The pens had concrete floors, asbestos roofing and the sides were made of wooden rails. There was a permanent feed trough at one end and a water trough at the other end of each pen. The steers were fed ad libitum for 60 days, but feed was offered twice a day, at 0800 and 1400 hours, to allow about 20 per cent refusals. Water was available at all times.

Table 1: Dietary components (g/kg) and chemical composition (g/kg DM) and metabolizable energy of five  sorghum and maize grain based diets

 

100M

75M:25S

50M:50S

25M:75S

100S

  Cottonseed meal

  63

  63

 63

  63

  63

  Wheat feed

155

155

155

155

155

  Maize grain

500

375

250

125

    0

  Sorghum grain

    0

125

250

375

500

  Molasses

120

120

120

120

120

  Veld hay

150

150

150

150

150

  Limestone flour

    9

    9

 9

    9

    9

  Salt

    2

    2

 2

    2

    2

  Vitamins/minerals

    1

    1

1

    1

    1

Composition, % of DM        

  Organic matter

942

958

966

951

954

  Crude protein

22.4

22.6

22.3

22.3

22.3

  NDF

252

249

214

252

223

  ADF

109

110

96

147

139

  Soluble PAs ,gA550/gDM

0.170

0.340

0.510

0.730

1.88

  Insoluble PAs A550/mgNDF

0.004

0.005

0.006

 0.008

 0.011

ME, MJ/kg DM#

12.04

 12.04

12.01

 11.98

11.96

#Calculated using Equation 73, Ministry of Agriculture, Fisheries and Food(UK) (1984)

Measurements

 

Feed offered and refused was recorded daily.  Both fresh feed and refusals were analyzed to detect any tendency towards diet selection. Animals were weighed once per fortnight.  A starved (24 hours) bodyweight was obtained at the beginning and end of the 60-day feeding period.  At the end of the feeding trial the steers were slaughtered, and the standard grading and carcass assessment was made (Cattle Producers Association 1998).

 

Animal health

 

The lambs were drenched against internal parasites with Ridafluke« (3% suspension) a broad spectrum remedy for the treatment of wireworm, liver fluke and nasal worm at the rate of 2.5 ml per 10 kg body mass. Cattle were drenched 1ml per 5 kg body mass of 2.265 per cent Oxfendazole m/v Systamex« fluid against internal parasites with at the start of the experiment.

 

Metabolizable energy calculations

 

The metabolizable energy of feeds was calculated from their proximate analysis according to Equation 1 (Ministry of Agriculture Fisheries and Foods (1984), Equation 73):

 

ME (MJ/kg DM) = 12 + 0.008CP + 0.023EE – 0.018CF – 0.012ASH         (1)

 

Chemical analysis

 

Feed and refusals were analyzed for concentrations of N and ash (AOAC, 1990), NDF and ADF (Van Soest et al 1991).  Urine was analysed for total nitrogen.  Insoluble proanthocyanidins were estimated by the butanol-HCl method (Reed et al 1982). Soluble PAs were estimated by the butanol-HCl method (Hagerman 2011). Urine was analysed for total nitrogen content.

 

Statistical analysis

 

Analysis of variance was carried out using the General Linear Model procedure of SAS (SAS 2000).  For the two trials, the weekly intake data were analysed using General Linear Model for repeated measures. Where F values were significant (P ≤ 0.05), differences among treatment means were tested by Student's t-test at alpha error level at 0.05. The relationship between PAs, intake, digestibility and feed conversion ratio was obtained using Pearson correlation analysis. The model used was:

 

            Yijk= m + Ti + Wj + TWij + ijk

Where:

 

            Yijk= is the measured response variable for the ith treatment in the jth week;

            m = is the overall population mean;

            Ti = is the effect of the ith dietary treatment;

            Wj = is the effect of the kth week on intake;

            TWij = is the treatment x week interaction;

            ijk = is the random residual error associated with Yijk.


Results

Trial 1

 

Intake and digestibility of feedlot diets fed to lambs

 

Feed intake (g/kg0.75) was not affected by the treatments (P > 0.05). Treatments ranked 50M: 50S>100M>75M: 25S>25M: 75S>100S (P ≤ 0.05) for dry matter digestibility and organic matter digestibility (Table 2).The N intake was similar across treatments. Faecal N output was lowest with 100M and highest with 100S, with the intermediate diets not differing from each other (Table 3). Urinary N output on the other hand decreased (P ≤ 0.05) with increase of sorghum grain in the diet. N retention was however not affected by treatments (P > 0.05).

 

Trial 2

 

Feedlot performance of steers

 

Intake and growth performance of the steers is shown in Table 4. Treatments ranked 100S>25M: 75S>100M>50M: 50S>75M: 25S (P ≤ 0.001) for feed intake (Figure 1, Table 4). Although not significantly different average daily gain of the animals was highest (P > 0.05) with 50M: 50S and 100S diets. Body mass changes decreased with time and were greatest (P ≤ 0.05) for the 100% maize based diet (Figure 2). Treatments ranked 50M: 50S >100M>100S>25M: 75S>75M: 25S (P ≤ 0.05) for feed conversion ratio. There was an interaction (P ≤ 0.001) between treatment and weekly intakes.

 

Carcass traits are shown in Table 5. There were no initial carcass weights, because of the breakdown of the slaughter facilities. Carcass weights, dressing proportions, fat score and carcass length were similar for all treatments.

Table 2: Voluntary feed intake and digestibility in sheep fed five  sorghum and maize grain based diets

 

100M

75M:25S

50M:50S

25M:75S

100S

SED

Prob

Feed intake (gDM/day)

1630

1753

1770

1731

1936

115

0.171

 Fed intake (g/kg0.75)

108

116

 118

121

132

9.6

0.129

Digestibility (g/kgDM)

 

 

 

 

 

 

 

   Dry matter

730ab

720abc

736a

704bc

695c

13.1

0.001

   Organic matter

752a

739ab

753a

719bc

709c

12.4

0.012

  Acid-detergent fibre

253bc

221c

304b

452a

313b

42.1

0.045

abc Means in the same row with different superscripts are different (P 0.05).

SED = Standard error of difference

100M=100% maize based diet; 75M:28S= 75% maize and 25% sorghum; 50M:50S=50% maize and 50% sorghum; 25M:75S=25% maize and 75% sorghum, 100S=100% sorghum based diet 


Table 3: Nitrogen intake, faecal, urinary and N retention in sheep fed five sorghum and maize grain based diets.

 

100M

75M:25S

50M:50S

25M:75S

100S

SED

Prob

Intake N(g)

36.5

41.5

39.9

38.7

43.6

2.31

0.639

Faecal N(g)

10.5c

16.8b

17.1b

17.9b

23.1a

1.66

0.023

Urinary N(g)

10.4a

  7.4ab

  4.2b

  4.3b

3.3b

1.87

0.038

Retained N(g)

15.6

17.3

18.6

16.4

17.2

2.08

0.831

abc Means in the same row with different superscripts are different (P0.05).

SED = Standard error of difference

100M=100% maize based diet; 75M:28S= 75% maize and 25% sorghum; 50M:50S=50% maize and 50% sorghum; 25M:75S=25% maize and 75% sorghum, 100S=100% sorghum based diet


Table 4: Feedlot performance of steers fed different sorghum and maize grain based diets*

 

100M

75M:25S

50M:50S

25M:75S

100S

SED

Prob

Daily intake

 

 

 

 

 

 

 

  Dry matter (kg)

8b

7.21c

7.4bc

8.5ab

8.9a

0.322

0.0001

  ME (MJ)

96.6

86.8

88.3

102

106

9.79

0.236

Live weight changes

 

 

 

 

 

 

 

   Initial weight  (kg)

247

243

240

242

242

-

0.961

   Final weight   (kg)

342

317

338

334

340

-

0.578

   Daily gain      (kg)

1.56

1.21

1.61

1.52

1.61

0.191

0.236

Feed conversion ratio

 

 

 

 

 

 

   kg DM/kg gain

5.21b

6.29a

4.64b

5.7ab

5.55ab

0.494

0.036

   ME MJ/kg DM gain

62.8b

75.8a

55.7b

68.2ab

66.4ab

5.95

0.035

*Grain portion of diet was 50 % of total diet as fed

abc Means in the same row with different superscripts are significantly different (P≤ 0.05).

SED = Standard error of difference

ME = metabolizable energy ; MJ/kg= mega joules per kilogram

100M=100% maize based diet; 75M:28S= 75% maize and 25% sorghum; 50M:50S=50% maize and 50% sorghum; 25M:75S=25% maize and 75% sorghum, 100S=100% sorghum based diet


Figure 1: Effect of grain type on body mass of steers over the experimental period

100M=100% maize based diet; 75M:28S= 75% maize and 25% sorghum; 50M:50S=50% maize and 50% sorghum;
25M:75S=25% maize and 75% sorghum, 100S=100% sorghum based diet


Table 5: Carcass characteristics of steers fed five maize and sorghum grain based diets

 

 

100M

75M:25S

50M:50S

25M:75S

100S

SED

Prob

Carcass weight (kg)

185

172

177

180

183

8.11

0.574

Dressing proportions (g/kg)

539

545

523

540

538

10.9

0.357

1Fleshing grade

5.67

6.33

6

5.83

5.50

0.65

0.746

2Fat score

2.17

1.67

2

1.83

1.67

0.245

0.215

Carcass length (cm)

116

113

114

114

114

1.49

0.644

1Fleshing grade was coded: A+ = 1, A- = 2, B+ = 3, ------E+ = 9, E- = 10, where 1 = very well fleshed and 10 = very poorly fleshed (Cattle Producers Association 1998).

2Fat score was coded: 1, 2 and 3, where 1 = lean (0-2 mm), 2 = minimum (3-7 mm) and

3 = Optimum (8-15 mm) (Cattle Producers Association 1998).

SED = Standard error of difference

100M=100% maize based diet; 75M:28S= 75% maize and 25% sorghum; 50M:50S=50% maize and 50% sorghum; 25M:75S=25% maize and 75% sorghum, 100S=100% sorghum based diet


Discussion

Organic matter digestibility of sorghum diet (100S) was 94.8% of maize diet (100M) while digestibility greater than that of the maize diet (100M) was observed in the maize and sorghum mixed diet (50M:50S). This supports the notion that the presence of PAs in the grain decreases nutritive value by complexing protein, carbohydrates and minerals (Nyachoti et al 1997). Larrain et al (2009) observed lower feed efficiency for DM, OM, crude fibre and N digestibility for sorghum grain compared with maize grain and attributed the findings to high PAs in sorghum grain comparison to maize grain. However a mixture of high-tannin sorghum and maize grain has been shown to improve animal performance (Larraine et al 2009). The improved animal performance of the sorghum with condensed tannins may have been due to dilution effect in the feedlot diets, as sorghum was combined with maize.

 

The improved performance of sorghum grain may also be attributed to tannins protecting protein from deamination in the rumen (Barry and Duncan 1984). Barry and Manley (1986) observed increased nitrogen retention in sheep fed high tannin than low tannin Lotus pedunculatus. This is attributed to an increased supply of amino acids entering small intestines as rumen undegradable dietary proteins (RUDP) as a result of high tannin levels in the brown sorghum grain. Although reports from early studies generally indicated poor ruminant performance for sorghum grain based diets when compared to maize grain (Hill et al 1996), in the current experiment sorghum grain diet (100S) had a feeding value almost similar to that of maize based diet (100M). This can be attributed to the fact that sorghum grain is very comparable to maize grain in terms of energy (Brouk 2010) and is high in protein content (National Research Council 1996).

 

Sorghum grain used in the experiment had a brown testa layer, which have been reported to have higher tannin content than red or white sorghums (Rooney et al 2005; Streeter et al 1991) which have lower digestibility (Brouk 2010). Amira (1992) recommends a maximum of 30% of brown sorghum inclusion and no upper limit or restriction for white sorghums in pen finishing diets. The grain inclusion in this experiment, at 50 per cent was higher than the rate recommended by Amira (1992). The high intake observed on 100% sorghum diet compared to the other diets was possibly to compensate for the lower feeding value of the sorghum grain. The grain had average tannin concentration of 26.9 g/kg DM. Tannins less than 40 g/kg DM have been shown to have no adverse effects on animal performance (Waghorn 1990).

 

The greatest faecal N and the lowest urinary N were observed with the 100% sorghum diet. The trend observed is similar to findings from other studies which reported that in feeds high in PAs, N excretion is mainly in the faeces (Reed and Soller 1987; Tanner et al 1990). Hill et al (1996) observed greater faecal N output in sorghum grain diets and no differences in urinary N output compared to maize diets.

 

The feed conversion ratio, although slightly greater with 50M:50S, was similar across treatments. Ncube et al (2001) observed similar results when steers were fed sorghum grain (variety DC75) high in PAs (61.6g/kg DM). This observation indicate that maize-sorghum diet with up to 50% sorghum inclusion does not adversely affect the digestibility of protein in ruminant livestock. Owen et al (1997) concluded that feeding sorghum resulted in similar average daily gains as maize when fed to feedlot animals however more emphasis should be on the processing of the grain as other studies have noted that in pigmented sorghum varieties, feed efficiency can be reduced by 10 to 30% compared to non-tannin sorghums (Rooney et al 2005)


Conclusion


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Received 22 May 2014; Accepted 17 August 2014; Published 5 September 2014

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