Yield and nutritive value of four napier (pennisetum purpureum) cultivars at different harvesting ages - UMS INSTITUTIONAL REPOSITORY

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AGRICULTURE AND BIOLOGY JOURNAL OF NORTH AMERICA

ISSN Print: 2151-7517, ISSN Online: 2151-7525, doi:10.5251/abjna.2016.7.5.213.219

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**Yield and nutritive value of four Napier (Pennisetum purpureum) cultivars at different harvesting ages**

M. Z. Zailan, H. Yaakub, S. Jusoh

Department of Animal Science, Faculty of Agriculture, Universiti Putra Malaysia, 43400, UPM Serdang, Selangor, Malaysia.

Corresponding Author: M. Z. Zailan, Department of Animal Science, Faculty of Agriculture, Universiti Putra Malaysia, 43400, UPM Serdang, Selangor, Malaysia, Tel) +603-8947 4873, Fax) +603-8938 1024, E-mail:

[email protected]

ABSTRACT

An experiment was conducted to assess the yield and nutritive value of four Napier (Pennisetum purpureum) cultivars (Common, Silver, Red and Dwarf Napier) harvested at three different ages (4^th, 6^th and 8^th weeks old). The interaction of cultivars and harvesting ages (P<0.05) was observed on dry matter yield (DMY) and nutritive value. Napier cultivars with the highest nutritive value were observed at the early age of cutting, 4^th weeks old. Consequently, limited DMY obtained at the early age of growth. Dwarf Napier had superior quality (P<0.05), in particular the crude protein (CP) content and in-vitro dry matter digestibility (IVDMD) across the harvesting age.

Red Napier yielded highest DMY (6.1 tonnes/ha/cut) at 8^th weeks old with the highest nutritive value observed among the tall cultivars across the harvesting age. The DMY of Common Napier peaked (5.7 tonnes/ha/cut) as early as 6^th weeks old. Nevertheless, the presence of extensive lignification bound on the structural carbohydrate inhibited the IVDMD. Silver Napier had no advantages in term of DMY and nutritive value over the other cultivars. Therefore, Dwarf Napier could be harvested on 6^th week (maximize CP content) or 8^th week old (maximize DMY) since there was no changed (P>0.05) in IVDMD. Red Napier is suggested to be harvested on 8^th weeks old to maximize the DMY. Common Napier was best harvested at 6^th weeks where the highest DMY can be attained without incur further losses in term of nutritive value.

Key words: Harvesting ages, Napier cultivars, nutritive value INTRODUCTION

Napier grass (Pennisetum purpureum) was first introduced to Malaysia in the 1920’s and several cultivars had been introduced since 1950’s. Napier grass is the most popular fodder used in dairy and feedlot production. Six cultivars grouped as tall type (> 130 cm) cultivars (Common Napier, Red Napier, Taiwan Napier, Indian Napier, Uganda Napier and King Grass) and three cultivars grouped as short types (< 90 cm) cultivars (Dwarf Napier, Dwarf “Mott”, Australian Dwarf) (Halim et al. 2013). The differences of height are due to the length of internodes and the pattern of internodes is influenced by the differentiation of cells of apical meristems (Rodrigues et al. 1986). The leafier structure of short cultivars contributed to high nutritive value than tall cultivars (Ansah et al. 2010). Nevertheless, short types had lower dry matter yield (DMY) compared to tall types.

Apart from morphological characteristics of Napier cultivars, the composition and digestibility of Napier grasses is highly influenced by harvesting age (Lounglawan et al. 2014). The nutritive value of grasses decreased in advanced of maturity. The reduction of digestibility as the harvesting age increased is related to lignin content in the mature plant. As indicated by Chen et al (2006), 80% of variance of in vitro true digestibility (IVDMD) attributable to the effect of harvesting interval.

Generally, the recommended age to harvest Napier is at 6 to 8 weeks of growth, to optimize the DMY and nutritive value (Lounglawan et al. 2014; Manyawu et al. 2003).

Based on previous study conducted by Halim et al.

(2013), Common Napier had the highest DMY with the most lignified structure than other cultivars.

Conversely, the Dwarf Napier was superior in term of

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214 nutritive quality with low DMY. The Red Napier had moderate DMY with the lowest lignin content among the tall cultivars. Aside from that, there is no documented information available regarding Silver Napier. Therefore, these four cultivars were justified and established to provide materials for comparative study on the effect of harvesting age on nutritive value of Napier cultivars. This information is required to select the best harvesting age in optimizing the DMY and nutritive value of Napier cultivars.

MATERIALS AND METHODS

Plot establishment: The stem cuttings of four Napier cultivars (Pennisetum purpureum- Common, Silver, Red and Dwarf Napier) cultivars were collected from Malaysian Agricultural Research and Development Institute (MARDI). The stem from mature grass was planted and basal fertilization was applied during grass establishment at the rate of 60 kg N, 60 kg P and 50 kg K ha^-1. The regrowth was harvested after 3 month plot establishment period. The grasses at the age of 4^th, 6^th and 8^th weeks old were harvested to provide materials for this study.

Dry matter yield and leaf-to-stem ratio: The grass was harvested by cutting in the randomly selected 1 m × 1 m quadrate. The grass yield obtained from quadrate sampling was oven-dried at 65°C for 48 h and later calculated as dry matter per hectare.

The fresh sample harvested from each treatment were weighed and separated into leaf (leaf blade) and stem (leaf sheath and stem). The samples were divided into three fractions; stem, leaf and whole plant and put in forced-air oven at 60°C until constant weight was achieved. The samples were weighed and ground to pass 1.5 mm sieve and kept in the container for nutritive value analysis.

Chemical composition: The grass samples were analyzed using standard procedures for chemical composition for dry matter (DM) and crude protein (CP) content according to AOAC (1990) procedure.

Neutral Detergent Fiber (NDF), Acid Detergent Fiber (ADF) and Acid Detergent Lignin (ADL) were measured according to Van Soest’s procedure (Van Soest et al 1991).

Gas production and In-vitro dry matter digestibility: The gas production (GP) and in-vitro dry matter digestibility (IVDMD) of Napier cultivars were measured according to Menke and Steingass (1988) technique. The rumen fluid used as inoculum was collected before morning feeding from 3 rumen- fistulated crossbred goats which fed on mixture fresh grasses and transferred into pre-warmed thermos bottle. The rumen content was composited and strained using two layers of cheesecloth under continuously flushing with CO2.Approximately 0.2 g DM of grounded samples (1 mm) with a 1:2 (v/v) mixture of rumen fluid and buffer medium was placed in a glass syringes (FORTUNA® Optima glass syringe), incubated at 39°C of water bath and being shaken at regular times. Incubation was performed in triplicates. During the incubation period, the GP was recorded at 2, 4, 6, 8, 12, 24, 32, 36 and 48 h. The blanks without substrate and samples were terminated at 48 h incubation period for determination of IVDMD. The residues were filtered using sintered glass crucible (coarse porosity no 1, pore size 100- 160 µm) and oven-dried at 105°C for 48 h to estimate the dry matter disappearance.

Statistical analysis: A 4 x 3 factorial design was performed and analyzed using general linear model (GLM) procedures of SAS 9.3 (Statistical analytical Institute Inc. Cary, North Carolina, USA). The difference between treatment means was measured by the Least Square Means. The level of significance used to determine the differences between treatments is P < 0.05.

RESULTS

Dry matter yield: The DMY increased in advanced of grass maturity (Table 1). All cultivars yielded similar (P>0.05) dry matter productivity at 4^th weeks old ranged from 0.8 to 1.0 tonnes/ha/cut. The DMY of Common Napier rose sharply and reached 5.7 tonnes/ha/cut at 6^th weeks old and no further increase was observed until 8^th weeks old. The DMY of Red Napier shot up dramatically from 6^th to 8^th weeks old from 2.7 to 6.1 tonnes/ha/cut. Both Silver and Dwarf Napier produced similar (P>0.05) DMY between each other throughout the harvesting age.

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Table 1: Dry matter yield of fresh Napier cultivars harvested at 4^th, 6^th and 8^th weeks old

* Refer to significant differences at P<0.05

a, b Within a row, means without a common superscript differ (P<0.05)

y, z Within a column, means without a common superscript differ (P<0.05) Table 2: Chemical composition of fresh Napier cultivars harvested at 4^th, 6^th and 8^th weeks of age

Parameter

(%) Cultivars Harvesting age (week)

SEM Treatment comparison

4 6 8 Treatment Prob.

CP Common 11.5^ax 8.01^bz 6.44^by

0.43

Cultivar 0.001

Silver 11.2^ax 12.5^ax 8.76^bx Harvesting age 0.001

Red 10.8âx 10.6ây 9.97âx Cultivar x

Harvesting age interaction 0.001 Dwarf 20.2^aw 15.6^bw 11.9^cw

NDF Common 69.0^cx 72.7^bw 76.7^aw

0.83

Cultivar 0.001

Silver 73.2^aw 69.2^bx 73.2^ax Harvesting age 0.001

Red 67.0âx 68.3âx 68.0ây Cultivar x

Harvesting age interaction 0.003 Dwarf 62.0^by 64.6^ay 66.3^ay

ADF Common 33.6^cw 47.^bw 53.5^aw

1.25

Cultivar 0.001

Silver 34.1^cw 39.3^bx 45.5^ax Harvesting age 0.001

Red 36.4^cw 40.1^bx 45.5^ax Cultivar x

Harvesting age interaction 0.001 Dwarf 26.8^bx 30.1^by 37.1^ay

ADL Common 3.53^cw 12.6^bw 17.8^aw

1.21

Cultivar 0.002

Silver 5.60^bw 8.65^abwx 12.0^ax Harvesting age 0.001

Red 5.03^bw 5.67^abx 9.19^axy Cultivar

x Harvesting age interaction 0.03

Dwarf 3.04^bw 6.67^abx 7.14^ay

CP refer to Crude protein; NDF: Neutral detergent fiber, ADF: Acid detergent fiber, ADL: Acid detergent lignin

a, b, c Within a row, means without a common superscript differ (P<0.05)

w, x, y, z Within a column, means without a common superscript differ (P<0.05) Leaf to stem ratio: The leaf-to-stem ratio (LSR) was

significantly affected by cultivar and harvesting age, respectively. The LSR of Napier cultivars was illustrated in Figure 1. Dwarf Napier was the leafier cultivars (P<0.05) where the leaf fraction was approximately 4 times heavier than the stem fraction.

The Red cultivars had the highest LSR among the tall cultivars. Based on the result obtained, all cultivars had higher leaf fraction than stem fraction. The LSR of Napier grasses decreased as the harvesting age increased (Figure 2). The leaves fraction was decreased significantly at 6^th weeks old and remained unchanged at 8^th weeks old.

Chemical composition: The results of crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL) were significantly (P<0.05) affected by the interaction of cultivars and harvesting ages as illustrated in Table 2.

Crude protein content: The CP decreased with increasing of plant maturity. Dwarf Napier had the highest CP content (P<0.05) among the cultivars and gradually decreased throughout the harvesting age.

The CP content of Silver, Red and Common were similar (11%) at 4^th week old. The CP content of Red Napier was unchanged (P>0.05) with the increasing of harvesting age. In spite of quality changes, the CP content obtained was above the critical level (> 7%

CP) in sustaining the rumen microflora (Minson, 1990) except for Common Napier at 8^th weeks old (6.44%).

Neutral detergent fiber: The NDF content tend to increase in advanced of grass maturity. Dwarf Napier had the lowest NDF content than other cultivars across the harvesting age. Both Common and Dwarf Napier increased gradually and it peaked at close to Parameter Cultivars Harvesting age (week)

4 6 8 Treatment Prob.

Dry matter yield (ton/ha/cut)

Common 0.79^by 5.69^ay 6.00^ay

0.56

Cultivar 0.072

Silver 0.94^by 3.27^az 3.89^az Harvesting age 0.001

Red 1.06^by 2.66^bz 6.09^ay Cultivar x

Harvesting age 0.025

Dwarf 0.80^by 2.85^az 3.87^az

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216 77% and 66%, respectively at 8^th weeks old. Silver and Red Napier had similar NDF content at 6^th week old. The NDF of Silver reached the highest level of 73% at 8^th week old whilst the Red Napier remained unchanged until 8^th weeks old.

Acid detergent fiber: The ADF content in Common, Silver and Red were highest (P<0.05) regardless of

the harvesting age compared to Dwarf Napier. The ADF of tall cultivars exceed 39% after 6^th weeks of harvesting age. The ADF content of Dwarf Napier remained unchanged (P>0.05) until 6^th weeks and shot up to 37% at 8^th weeks old.

Fig. 1. The leaf to stem ratio of Napier cultivars

c c

b

a

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Common Silver Red Dwarf

Leaf to stem ratio (g/g DM)

Cultivars

Common Silver Red Dwarf

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AGRICULTURE AND BIOLOGY JOURNAL OF NORTH AMERICA

ISSN Print: 2151-7517, ISSN Online: 2151-7525, doi:10.5251/abjna.2016.7.5.213.219

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Fig 2. The leaf to stem fraction of fresh Napier at 4^th, 6^th and 8^th weeks old

Acid detergent lignin: The ADL content showed a direct relationship to the grass maturity A similar (P<0.05) ADL content shown among cultivars (3 to 6%) at 4^th weeks old. The ADL content of Common Napier shot up at 6^th week old and continued to increase to 18% at 8^th weeks old. The ADL content of

Silver Napier increased gradually (6 to 12%) throughout the harvesting age. A moderate increment of ADL content observed in Red (5 to 9%) and Dwarf Napier (3 to 7%) as the harvesting age prolonged from 4^th to 8^th weeks old.

Table 3: Gas production and in-vitro dry matter digestibility of fresh Napier cultivars harvested at 6^th and 8^th weeks of age of 48 hours ruminal in-vitro fermentation period

Parameter Cultivars Harvesting stages (week)

6 8 Treatment P-Value

Gas production (ml/g DM)

Common 209^az 214^az

2.15

Cultivar 0.001

Silver 259^by 268^ay Harvesting age 0.001

Red 255^by 294^ax Cultivar x

Harvesting age interaction 0.001

Dwarf 283^bx 314^aw

IVDMD (%)

Common 59.6^ay 49.7^by

1.28

Cultivar 0.001

Silver 66.3^ax 52.9^by Harvesting age 0.001

Red 70.6^aw 62.1^bx Cultivar x

Harvesting age interaction 0.023

Dwarf 77.1^aw 73.9^aw

IVDMD refer to in-vitro dry matter digestibility

*, refer to significant differences at P < 0.05

a, b Within a row, means without a common superscript differ (P < 0.05)

w, x, y, z Within a column, means without a common superscript differ (P < 0.05)

Gas production and In-vitro dry matter digestibility: The results of gas production and in- vitro dry matter digestibility were depicted in Table 3.

The gas production (GP) of Napier cultivars

increased (P<0.05) in advanced of maturity except for Common Napier where the GP was similar (P>0.05) throughout the harvesting age. Regardless of harvesting age, Dwarf Napier had the highest GP a

b

0 0.5 1 1.5 2 2.5 3 3.5 4

4 6 8

Leaf to stem ratio (g/g DM)

Harvesting age (weeks)

4 6 8

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218 and IVDMD followed by Red Napier, Silver Napier and lowest in Common Napier. Nevertheless, the IVDMD of Dwarf Napier remained unchanged (P>0.05) until 8^th week old. The IVDMD of Red, Silver and Common Napier tend to fall significantly (P<0.05) until reached the lowest point at 8^th weeks old.

DISCUSSION

The highest nutritional quality of Napier cultivars was indicated at the early age of growth, 4^th weeks of age.

Nevertheless, the DMY of Napier cultivars were too low. The frequent cuttings limit the productivity by disrupting the photosynthesis process to replenish the losses of energy levels for regenerative activity (Trujillo et al 1996). Due to the economic reasons, thus the treatment of 4^th weeks harvesting age was disregard for IVDMD analysis.

Generally, the cell content decreased in advanced of grass maturity. The reduction of cell content, in particular CP content is suppress by the accumulation of structural carbohydrates in advanced of plant maturity (Van Soest 1982). Nevertheless, the results obtained in this current study indicated that the growth rate, degree of lignification and accumulated structural carbohydrate differed between cultivars as the harvesting age increased.

The DMY of Common Napier was peaked as early as 6^th weeks old and showed highest DMY among cultivars. Nevertheless, the extensive lignification of Common Napier resulted in poor IVDMD and this is related to stemmy structure of Common Napier compared to other cultivars.

The Red Napier yielded the highest DMY at 8^th weeks old. In spite of that, the unchanged of NDF content resulted in a similar CP content throughout this study. A significant increase in ADF and ADL contents reduced the IVDMD of Red Napier at 8^th weeks old. Though, the Red Napier showed the highest IVDMD within tall cultivars.

Silver and Dwarf Napier yielded the lowest DMY throughout the harvesting age. Silver Napier had no advantages in term of nutritive quality compared to Dwarf Napier. Dwarf Napier had the highest cell content (lowest NDF) and CP content than other cultivars throughout the harvesting age. This was influenced by the major leaf fraction presence in Dwarf Napier than the others. At 6^th weeks old, the CP content of Dwarf Napier was closed to 16% which is required in optimizing the milk output of lactating

animals (Imaizumi et al 2010). In spite of that, the CP content was surpassed the minimum requirement of 15% for lactation and growth (McDonald et al 2002).

The IVDMD of Dwarf Napier was the highest (> 70%

IVDMD) than other cultivars and the IVDMD was not affected by the age of harvesting.

CONCLUSION

 Dwarf Napier is superior in term of nutritive quality. It is recommended to harvest at 8^th weeks old to maximize the DMY since there was no changed in IVDMD. It could be harvested at 6^th weeks old to yield higher CP content (16%) with losses of 1 tonnes DM/ha/cut incur compared to 8^th weeks old.

 Red Napier is suggested to be harvested at 8^th week old in order to maximize the DMY due to no significant losses of CP occurred. Red Napier had the highest quality among the tall cultivars.

 Common Napier could be harvested at 6^th weeks old where the DMY could be maximized without incurred further losses in the nutritive quality (CP and IVDMD).

 Silver Napier had no advantages to other cultivars. The DMY was similar as Dwarf Napier whilst the nutritive quality was poor than Dwarf Napier.

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