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Tropical Animal Health and Production

, Volume 45, Issue 2, pp 533–538 | Cite as

Performance of lactating dairy cows fed a diet based on treated rice straw and supplemented with pelleted sweet potato vines

  • Kampanat Phesatcha
  • Metha Wanapat
Regular Articles

Abstract

The purpose of this study was to evaluate the effects of sweet potato vine pellet (SWEPP) in concentrate diets on nutrient digestibility and rumen ecology in lactating dairy cows fed on urea-treated rice straw. Three multiparous Holstein crossbred cows in mid-lactation were randomly assigned according to a 3 × 3 Latin square design, and the treatments were as follows: T1 = control (no supplementation), T2 = supplementation of sweet potato vine pellet with 50 g/kg urea (SWEPP I) at 300 g/head/day, and T3 = supplementation of sweet potato pellet with 100 g/kg urea (SWEPP II) at 300 g/head/day, in concentrate diets, respectively. The result revealed that supplementation of SWEPP did not affect feed intake, ruminal pH, and blood urea nitrogen (P > 0.05). However, apparent digestibilities of organic matter, crude protein, and neutral detergent fiber were higher in SWEPP II than those in others. Furthermore, ruminal ammonia nitrogen (NH3-N) and milk yield were significantly higher (P < 0.05) in animals fed with SWEPP II than those fed with SWEPP I and control, respectively. In addition, there were no differences in purine derivatives and microbial nitrogen supply among all the treatments. Based on this study, it could be concluded that SWEPP is a good source of supplement which resulted in significant improvement in apparent digestibility, rumen fermentation, and milk yield in lactating dairy cows fed on urea-treated rice straw.

Keywords

Sweet potato vine pellet Rumen ecology Urea-treated rice straw Dairy cows Urea Supplementation Urinary purine derivative 

Introduction

Ruminants raised in the tropics largely depend on seasonal feed resources which are relatively low in quality. Hence, the manipulation of rumen efficiency through the use of local feeds would be an advantage (Wanapat 2000). Sweet potato is one of the five most important food crops in developing countries due to the large volume of foliage (stems, leaves, and available amount of noncommercial roots) which is left on the field after harvesting, all of which could be utilized as ruminant feed. Traditionally, sweet potato was grown exclusively by smallholder livestock farmers for the production of the tubers only and the foliage was considered as a residue and therefore underutilized. In developing countries, sweet potato can be grown two to three times per year, and vines, with dry matter (DM) production as high as 4.3–6.0 tons per ha (leaf, petiole, and stem) accounts for approximately 640 g/kg of fresh biomass, are mainly used as an animal feed. The crude protein (CP) content of sweet potato forage ranged from 180 to 300 g/kg DM among different varieties (An et al. 2003), while the crude fiber content is about 180 g/kg DM. The DM digestibility was about 700 g/kg (Foulkes et al. 1997). The value of sweet potato is attributed to high yield, palatability, and digestibility for consumption by ruminants (Etela et al. 2009). However, the use of sweet potato vine in a pellet form has not yet been reported especially in ruminants. Therefore, the purpose of this study was to evaluate the effects of sweet potato vine pellet (SWEPP) supplementation as a protein and mineral source on rumen ecology nutrient digestibility and performance of lactating dairy cows fed on urea-treated rice straw.

Materials and methods

Three multiparous mid-lactation Holstein–Friesian crossbred cows with average body weight of 380 ± 15 kg (about 3 years old) were randomly assigned according to a 3 × 3 Latin square design to investigate the supplementation of SWEPP with urea-treated rice straw (UTRS, 5 kg urea/100 kg rice straw) as a basal roughage. The compositions of concentrate diet and UTRS are shown in Table 1. The dietary treatments were as follows: T1 = control (no supplementation), T2 = supplementation of sweet potato vine pellet with 50 g/kg urea (SWEP I), and T3 = supplementation of sweet potato vine pellet with 100 g/kg urea (SWEP II). Supplementation SWEPP I or II were given at 300 g/head/day. The SWEPP was supplemented in two equal parts for the animals in the morning and afternoon feeding times. The chemical compositions of SWEPP I and II are shown in Table 2.
Table 1

Ingredients and chemical composition of concentrate and urea-treated rice straw used in the experiment (in percent DM basis)

Item

Concentrate

UTRS

Ingredients, g/kg DM

 Cassava chip

600

 

 Rice bran

122

 

 Coconut meal

58

 

 Palm kernel meal

136

 

 Urea

34

 

 Sulfur

10

 

 Mineral mixed

10

 

 Salt

10

 

 Molasses

20

 

Chemical composition, g/kg DM

 Dry matter

932

576

 Organic matter

907

877

 Ash

93

122

 Crude protein

161

67

 Neutral detergent fiber

244

782

 Acid detergent fiber

115

563

 Total digestible nutrientsa

765

552

UTRS urea-treated rice straw (5 % urea)

aCalculated values

Table 2

Feed ingredients and chemical composition of sweet potato vine pellet used in the experiment

Item

Formula

SWEPP I

SWEPP II

Ingredients, %DM

 Sweet potato vine

865

815

 Molasses

50

50

 Cassava starch

5

5

 Urea

50

100

 Sulfur

10

10

 Mineral mixed

10

10

 Salt

10

10

Chemical composition, g/kg DM

 Dry matter

952

956

 Organic matter

817

814

 Ash

183

186

 Crude protein

289

405

 Neutral detergent fiber

354

331

 Acid detergent fiber

286

278

 Total digestible nutrientsa

705

666

SWEPP I sweet potato vine pellet with 5 % urea, SWEPP II sweet potato vine pellet with 10 % urea

aCalculated values

Cows were housed in individual pens and individually fed with concentrate diets at a ratio of concentrate to milk yield of 1:1.5, twice daily during milking. All cows were fed ad libitum of rice straw as a roughage source while allowing for 100 g/kg refusals. Clean fresh water and mineral blocks were available at all times. Feed intake of concentrates and roughage was measured separately, and refusals were recorded.

Rice straw and concentrates were sampled daily during the collection period. Feeds, fecal, and urine samples were collected during the last 7 days of each period. Each of the three periods lasted for 21 days. Fecal samples were collected by rectal sampling while urine samples were collected by spot sampling. Composited samples were dried at 60 °C, ground (1-mm screen using Cyclotech Mill, Tecator), and then analyzed for DM, ash, and CP contents (AOAC 1997); neutral detergent fiber (NDF) and acid detergent fiber (ADF) (Van Soest et al. 1991); and acid-insoluble ash (AIA). AIA was used to estimate the digestibility of nutrients (Van Keulen and Young 1977).

Milk samples were composited daily, according to yield, for both the morning and afternoon milking, preserved with 2-bromo-2-nitropropane-1,3-diol, and stored at 4 °C until analysis for fat, protein, lactose, total solids, and solids-not-fat content by infrared methods using Milko-Scan 33 (Foss Electric, Hillerod, Demark). Milk urea nitrogen (MUN) was determined using Sigma kits #640 (Sigma Diagnostics, St. Louis, MO).

At the end of each period, rumen fluid and jugular blood samples were collected at 0, 2, 4, and 6 h postmorning feeding. Approximately 200 ml of rumen fluid was taken from the rumen by a stomach tube connected with a vacuum pump at each time. Rumen fluid was immediately measured for pH and temperature after withdrawal. Rumen fluid samples were then filtered through four layers of cheesecloth. Samples were divided into three portions; one portion was used for NH3-N analysis using the micro-Kjeldahl methods and volatile fatty acid (VFA) analysis using HPLC (Samuel et al. 1997). A second portion was fixed with 10 % formalin solution in sterilized 0.9 % saline solution. The total direct count of bacteria, protozoa, and fungal zoospores was made by the methods of Galyean (1989) based on the use of a hemacytometer (Boeco, Singapore). The third portion was for the total viable bacteria count (cellulolytic, proteolytic, amylolytic) and total viable bacteria using the Hungate (1969) roll-tube technique.

A blood sample (about 10 ml) was collected from the jugular vein (at the same time as rumen fluid sampling) into tubes containing 12 mg of EDTA and stored at −20 °C until analysis of blood urea N according to the method of Crocker (1967). Urine samples were analyzed for allantoin and creatinine in urine by HPLC as described by Chen and Gomes (1992). The amount of microbial purines absorbed was calculated from purine derivative excretion based on the relationship derived by Chen and Gomes (1992).

Statistical analysis

The data were analyzed in a 3 × 3 Latin square design by analysis of variance run in the GLM procedure of SAS (SAS Institute Inc. 1998). The results are presented as mean values and standard error of the means. Differences between treatment means were determined by Duncan’s new multiple range test (Steel and Torrie 1980). Differences among means with P < 0.05 were accepted as representing statistically significant differences.

Results and discussions

The chemical compositions of concentrates and roughage diets fed in dairy cows are presented in Table 1. Concentrate diets contained similar concentrations of DM, organic matter (OM), CP, NDF, ADF, and TDN. These values would be expected to support normal performance of these lactating cows according to NRC (1989).

The effects of SWEPP in concentrate on voluntary feed intake and nutrient digestibility in lactating dairy cows are presented in Table 3. Urea-treated rice straw intake, concentrate intake, and total DMI were not significantly affected (P > 0.05) by SWEPP; however, apparent digestibilities of OM, CP, and NDF were significantly different (P < 0.05) among treatments with the greatest values for dairy cows fed SWEPP II in the concentrate. Higher digestibility of the experimental diets could be due to better activity of fiber fermentation. However, apparent digestibilities of DM and ADF were not affected by treatments (P > 0.05).
Table 3

Effects of sweet potato vine pellet on daily feed intakes and nutrient digestibility in lactating dairy cows

 

Dietary treatment

SEM

P value

Control

SWEPP I

SWEPP II

DM intake, kg/h/day

 UTRS

6.0

6.1

6.2

0.36

0.71

 Concentrate

6.7

6.9

7.6

0.21

0.63

Total

12.7

13.0

13.8

1.83

0.92

%BW

3.1

3.2

3.3

0.63

0.42

Apparent digestibility coefficients, g/kg DM

 Dry matter

653

661

665

4.61

0.33

 Organic matter

695 a

711 a, b

722 b

14.35

0.02

 Crude protein

622 a

629 a, b

635 b

11.78

0.04

 Neutral detergent fiber

553 a

564 a, b

585 b

3.56

0.04

 Acid detergent fiber

408

420

424

12.09

0.98

Means in the same row with different lowercase letters differ (P < 0.05)

SWEPP I sweet potato vine pellet with 5 % urea, SWEPP II sweet potato vine pellet with 10 % urea, UTRS urea-treated rice straw (5 %urea)

Rumen pH and temperature were not different among treatments, and the values were stable at pH 6.8 to 6.9 and temperature of 39.4 to 39.6 °C in normal ranges, which have been reported as optimal for microbial digestion of fiber (pH 6.5 to 7.0 and temperature of 39.0 to 41.0 °C) (Firkins 1996 and Wanapat 1990). Blood urea nitrogen concentration was 12.1–13.0 mg/dl and was similar with that reported by Abeni et al. (2000), while ruminal NH3-N concentration was higher (P < 0.05) in SWEPP II than SWEPP I and control, respectively. The average values of NH3-N in this study were 11.8 to 15.1 mg/dl. The optimal ammonia nitrogen concentration in ruminal fluid for microbial growth ranges from 5.0 to 25.0 mg/dl (Preston and Leng 1987), 15 to 30 mg/dl (Wanapat and Pimpa 1999), and 8.5 to over 30 mg/dl (McDonald et al. 1996). Concentrations of blood urea N are highly correlated to the concentration of NH3-N production in the rumen (Wanapat et al. 2008). Production of total VFA, acetic acid (C2), propionic acid (C3), butyric acid (C4) proportions, C2/C3 and C2 + C4/C3 ratios is shown in Table 4. There were no significant differences in VFA concentrations (P > 0.05), except propionic acid (C3) which was the highest in SWEPP II (P < 0.05). Total VFA concentrations in all treatments ranged from 113.1 to 114.9 mM and were similar to those reported by Wanapat (2008). However, dietary supplementation did not affect methane production. Moreover, viable cellulolytic bacteria were significantly different among treatments (P < 0.05) and were greatest in SWEPP II supplementation.
Table 4

Effects of sweet potato vine pellet on ruminal pH, NH3-N, blood urea nitrogen, microbial population, and volatile fatty acid concentrations in lactating dairy cows

 

Dietary treatment

SEM

P value

Control

SWEPP I

SWEPP II

Ruminal parameters

 pH

6.9

6.9

6.8

0.07

0.19

 Temp., °C

39.4

39.6

39.6

0.18

0.76

 NH3-N, mg/dl

11.8 a

12.1 b

15.1c

0.67

0.04

 Blood urea nitrogen, mg/dl

12.1

12.5

13.0

1.21

0.42

Total direct count, cell/ml

 Bacteria, ×109

3.5

3.7

3.9

0.54

0.63

 Protozoa, ×105

2.8

2.7

2.9

0.46

0.47

 Fungal zoospore, ×105

2.1

2.1

2.3

0.03

0.54

Total viable bacteria, CFU/ml

 Proteolytic bacteria, ×108

1.3

1.4

1.4

0.88

0.31

 Cellulolytic bacteria, ×109

1.1 a

1.7 b

2.4c

0.06

0.03

 Amylolytic bacteria, ×107

1.8

1.5

1.7

1.43

0.33

Total VFA, mmol/l

113.1

114.2

114.9

0.20

0.07

VFA, mol/100 mol

 Acetic acid (C2)

70.2

67.9

67.2

1.82

0.29

 Propionic acid (C3)

18.4 a

22.2 b

22.8b

0.76

0.04

 Butyric acid (C4)

8.4

8.8

9.1

1.48

0.86

 C2:C3

3.8

3.1

2.9

0.06

0.15

 C2 + C4/C3

4.3

3.5

4.2

0.20

0.61

CH4, mol/100 mola

29.9

28.0

27.6

0.91

0.24

Means in the same row with different lowercase letters differ (P < 0.05)

SWEPP I sweet potato vine pellet with 5 % urea, SWEPP II sweet potato vine pellet with 10 % urea

aCalculated according to Moss et al. (2000); CH4 production = 0.45(acetate) − 0.275(propionate) + 0.4(butyrate)

The effects of SWEPP on the excretion of urinary purine derivatives and microbial crude protein supply in lactating dairy cows are presented in Table 5. The excretions of creatinine and allantoin concentrations in urine were not affected in all the treatments. Microbial protein synthesis in the rumen provides the majority of protein supplied to the small intestine of ruminants, accounting for 500 to 800 g/kg of total absorbable protein (Firkins et al. 2007). In the present study, microbial crude protein flows from the rumen as calculated from purine derivative excretion using an equation (Chen and Gomes 1992; Galo et al. 2003) ranged from 496.1 to 881.3 g/day.
Table 5

Effect of sweet potato vine pellet on nitrogen balance, excretion of purine derivatives (PD), and microbial nitrogen supply in lactating dairy cows

 

Dietary treatment

SEM

P value

Control

SWEPP I

SWEPP II

Purine derivatives, mmol/day

Allantoin excretion

165.4

173.6

179.8

1.98

0.78

Allantoin absorption

134.3

142.1

147.7

1.05

0.61

Urine creatinine

21.5

20.9

20.1

0.95

0.45

 MCP, g/daya

564.9

592.9

611.0

2.10

0.22

 EMNS, g/kg OMDRb

13.4

13.8

14.2

0.62

0.85

Means in the same row with different lowercase letters differ (P < 0.05)

SWEPP I sweet potato vine pellet with 5 % urea, SWEPP II sweet potato vine pellet with 10 % urea

aMicrobial crude protein (MCP) (g/day) = 3.99 × 0.856 × mmol of purine derivatives excreted (Galo et al. 2003)

bEfficiency of microbial N synthesis (EMNS), grams per kilogram of OM digested in the rumen (OMDR) = [(MCP (g/day) × 1,000) / DOMR (g)], assuming that rumen digestion = 65 % of digestion in total tract

The effects of sweet potato vine pellet on milk yield and composition in the lactating dairy cows are presented in Table 6. Milk yield was significantly higher (P < 0.05) with supplementation of SWEPP II than SWEPP I and control, respectively. MUN concentrations were not different among the treatments and were similar to those of Schroeder (2002) who reported that cows with MUN levels less than 10 to 12 mg/dl and higher than 16 to 18 mg/dl could result in higher feed costs, reduced health, lower productive performance, and low milk production.
Table 6

Effects of sweet potato vine pellet on milk yield and composition in the lactating dairy cows

 

Dietary treatment

SEM

P values

Control

SWEPP I

SWEPP II

Production

 Milk yield, kg/day

10.1 a

10.5 a

11.8 b

0.04

0.02

 3.5 % FCM, kg/daya

10.3 a

11.7 a

13.2 b

0.09

0.03

Milk composition, g/kg DM

 Fat

3.7

4.2

4.2

0.27

0.62

 Protein

2.9

3.0

3.4

0.02

0.22

 Lactose

4.6

4.6

4.6

0.01

0.88

 Solids-not-fat

8.3

8.2

8.6

0.12

0.63

 Total solids

11.0

12.8

12.9

1.20

0.76

Milk urea N, mg%

12.8

13.0

13.3

2.13

0.95

Means in the same row with different lowercase letters differ (P < 0.05)

SWEPP I sweet potato vine pellet with 5 % urea, SWEPP II sweet potato vine pellet with 10 % urea

a3.5 % fat-corrected milk (FCM) = 0.432 (kg of milk/day) + 16.23 (kg of fat)

Conclusions and recommendations

Based on this study, it could be concluded that SWEPP is a good source of protein supplement and SWEPP II was more efficient than SWEPP I on apparent digestibility, rumen fermentation, and milk yield in lactating dairy cows. Therefore, SWEPP II was formulated to contain high CP (405 g/kg); hence, it is recommended to be used as protein sources supplement for lactating dairy cow. Further research on the use of other protein source such as soy bean meal as a SWEPP II replacement could be conducted.

Notes

Acknowledgments

The authors would like to express their most sincere thanks to all who have assisted and supported this study, particularly the Tropical Feed Resources Research and Development Center (TROFREC), Department of Animal Science, Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand; the Royal Golden Jubilee Ph. D. Scholarship Program; and the Dairy Promotion Organization of Thailand (DPO), Northeast Region, for their active collaborations and support.

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Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  1. 1.Tropical Feed Resources Research and Development Center (TROFREC), Department of Animal Science, Faculty of AgricultureKhon Kaen UniversityKhon KaenThailand

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