Determination of potential nutritive value of cotton gin trash produced from different feed companies

Abstract

The aim of this study was to determine the potential nutritive value of cotton gin trash obtained from five different companies using chemical composition and in vitro gas production technique. There was considerable variation among cotton gin trash obtained from five different companies in terms of chemical composition and in vitro gas production, metabolizable energy (ME) and organic matter digestibility (OMD). The crude protein (CP) contents of cotton gin trash ranged from 6.59% to 12.55% on dry matter (DM). Neutral detergent fibre (NDF) and acid detergent fibre (ADF) contents ranged from 49.24 to 62.22% on DM and 40.73 to 48.31% on DM respectively. The gas production ranged from 22.91 to 33.51 ml of 200 mg of DM after 24-h incubation. The ME and OMD contents of cotton gin trash ranged from 5.38 to 7.09 MJ/kg DM and 37.44 to 52.69% respectively. In conclusion, chemical characterization of CP, OMD and ME suggests that the cotton gin trash moderate level of CP concentration and was digestible therefore it could be said that cotton gin trash will provide roughage of an acceptable quality for ruminant animals.

Keywords:

• chemical composition
• digestibility
• metabolizable energy
• gas production
• cotton gin trash

1. Introduction

Cotton production and processing are important to the economy in Turkey. Approximately 4.884.963 decares of cotton are grown yearly in Turkey (TUIK 2012). After ginning of harvested cotton, considerable amount of by-products become available. This by-product is more commonly referred to as cotton gin trash or just gin trash. The nutrient composition of gin trash varies depending on the variety of cotton, the region grown and type of harvest method used (Bader et al. 1998). Recently farmers have begun to use the cotton gin trash to meet the energy and protein requirements of ruminant animal in most parts of Turkey during forage shortage as cotton gin trash has been used in ruminant diets in most parts of the world (Brown et al. 1979; Conner & Richardson 1987; Kennedy & Rankins 2008). Cotton gin trash was also used as a silage additive due to its high dry matter (DM) content (Miron et al. 1995). Considering actual raw material cost and consequent food crisis, in general by-products offer advantages. The by-products are generally cheaper than conventional feedstuffs. Therefore farmers can include the by-products into diets of animals provided that the by-products support acceptable animal performance (Meglas et al. 1991; Gaffari et al. 2014). As a result, farmers save money using less expensive by-products. However it is crucial to obtain information about the chemical composition and nutritive value to make full of advantages from by-products. Although there is considerable amount of cotton gin trash production there is no information about chemical composition, digestibility and metabolic energy contents of cotton gin trash produced from different companies in Turkey. Chemical composition, in combination with in vitro gas production, organic matter digestibility (OMD) and metabolizable energy (ME) content were widely used to determine the potential nutritive value of feedstuffs which are previously limited or uninvestigated (Kamalak et al. 2005; Kamalak et al. 2011; Canbolat 2012; Guven 2012). The aim of this study was to determine the potential nutritive value of cotton gin trash produced by different companies using chemical composition and in vitro gas production technique.

2. Material and methods

2.1. Gin trash

Cotton gin trashes were obtained from five different companies [Emeksizler Ltd. Ş, Adana (I), Asmar Efe Ltd. Ş, Kahramanmaras (II), Koza Yem, Kahramanmaras (III), Dok A. Ş, Kahramanmaras (IV) and Celil Süt Ltd. Ş. Kahramanmaras (V)].

2.2. Chemical analysis

Five companies process the cotton gin trash in similar manner. First of all, foreign material is separated from cotton gin trash. Then the cotton gin trash is grounded and extruded. Finally the extruded cotton gin trash is stored in bags with 50 kg capacity for market.

Cotton gin trashes were milled in a hammer mill through a 1 mm sieve for subsequent analysis. DM contents of cotton gin trash were determined by drying the samples at 105°C overnight (method 967.03, AOAC 1990) and ash by igniting the samples in muffle furnace at 525^oC for 8 h (method 923.03, AOAC 1990). Nitrogen (N) contents of cotton gin trash were measured by the Kjeldahl method (method 981.10, AOAC 1990). Crude protein (CP) contents of cotton gin trash were calculated as NX 6.25. Ether extract contents were measured by Soxhlet apparatus (method 920.29, AOAC 1990). Neutral detergent fibre (NDF) contents of cotton gin trash were determined by the method of van Soest and Wine (1967) and acid detergent fibre (ADF) contents of cotton gin trash were determined by the method of van Soest (1963). Lignin content of cotton gin trash was determined by the method of van Soest et al. (1991). All chemical analysis is carried out in triplicate.

2.3. In vitro gas production

This experiment was approved by the Animal Experimentation Ethics Committee of University of Kahramanmaras Sutcu Imam, Faculty of Agriculture (Protocol No. 2013/3-10). Cotton gin trash milled was incubated in vitro with rumen fluid in calibrated glass syringes following the procedures of Menke et al. (1979). Rumen fluid was obtained from one-year-old and approximately 50 kg of three fistulated Awassi rams after one-week adjustment period of a diet. Fistulated Awassi rams fed twice daily with a diet containing alfalfa hay (60%) and barley (40%). Rumen fluid was collected before morning feeding and squeezed through four layers of cheesecloth. The rumen fluid was flushed with CO₂. The rumen fluid was added to buffered mineral solution in the ratio of 1:2 respectively. Buffered mineral solution were prepared mixing 474 ml distilled water, 0.12 ml micro mineral solution, 237 ml buffered solution, 237 ml macro mineral solution, 50 ml reduction solution and 1.22 ml Resazurin solution. Approximately 0.200 g dry weight of cotton gin trash samples was weighed in triplicate into calibrated glass syringes of 100 ml. The syringes were prewarmed at 39°C before the injection of 30 ml rumen fluid–buffer mixture into each syringe followed by incubation in a water bath at 39°C. Four bottles (blank) containing only 30 ml rumen fluid–buffer mixture was also incubated. Gas production was recorded at 24 h after incubation and corrected for blank incubation. The experimental design was a completely randomized design.

The ME and OMD values of cotton gin trash were estimated using equation of Menke and Steingass (1988) as follows:

2.4. Statistical analyses

One-way analysis of variance was carried out to determine the effect of companies on the chemical composition, gas production kinetics, ME and OMD of cotton gin trash. Significance between individual means was identified using the Tukey's multiple range tests. Mean differences were considered significant at P < 0.05.

3. Results and discussion

The chemical composition of cotton gin trash was given in Table 1. The origin of cotton gin trash had significant effect on the chemical composition of cotton gin trash. There were considerable variations in chemical composition of cotton gin trash obtained from different companies. However the variation was very high in ash and CP contents of cotton gin trash. The ash and CP contents of cotton gin trash ranged from 8.95 to 17.67% and 6.59 to 12.55% on DM respectively. The cotton gin trash from Company II had significantly higher ash and CP contents than the others. Although there were significant variations in cell wall contents of cotton gin trash, the variations were small when compared with that in ash and CP of cotton gin trash. The NDF and ADF contents ranged from 49.24 to 62.22% and 40.73 to 48.31% on DM respectively. The cotton gin trash from Companies II and V had significantly lower NDF contents than the others. The cotton gin trash from Company I had significantly higher ADF contents than the others.

Table 1. The chemical composition of cotton gin trash obtained from different companies on a dry matter basis.

	Companies
Composition	I	II	III	IV	V	SEM	P
DM	95.84^b	95.65^b	97.29^a	96.90^a	95.55^b	0.252	**
Ash	8.95^e	17.67^a	10.81^d	12.88^c	15.47^b	0.263	**
CP	6.59^c	12.55^a	6.96^c	8.08^b	12.44^a	0.177	**
EE	4.07^b	3.61^b	3.35^b	6.13^a	4.47^b	0.324	**
NDF	62.22^a	50.69^b	58.73^a	60.44^a	49.24^b	1.304	**
ADF	48.31^a	41.58^b	42.13^b	42.34^b	40.73^b	0.679	**
Lignin	16.89^a	16.77^a	13.78^b	15.46^ab	14.68^ab	0.812	*

Note: ^a–^cRow means with common superscripts do not differ (P > 0.05).

SEM, standard error mean; P, significance level; DM, dry matter%, CP, crude protein, NDF, neutral detergent fibre, ADF, acid detergent fibre.

* P < 0.05, **P < 0.001.

There were significant variations in the chemical compositions of cotton gin trash produced from different companies. The NDF contents of cotton gin trash produced from Companies I and IV were comparable with those values reported by Kennedy and Rankins (2008) and Holt et al. (2003) who reported that the NDF contents of cotton gin trash were 69.2% and 64.45% on DM respectively. However the ADF contents of cotton gin trash produced from five companies in Turkey were considerably lower than those reported by Kennedy and Rankins (2008) and Holt et al. (2003) who reported that the ADF contents of cotton gin trash were 60.8% and 58.85% on DM respectively.

The CP contents of cotton gin trash produced from Companies II and V were in agreement with that reported by Kennedy and Rankins (2008) who found that the CP content of cotton gin trash was 12.4% on DM. The CP contents of cotton gin trash produced from Companies I and III were in agreement with that reported by Pordesimo et al. (2005) who found that the CP content of cotton gin trash was 7% on DM. The CP content of cotton gin trash produced from Company IV was in agreement with that reported by Holt et al. (2003) who found that the CP content of cotton gin trash was 9.1% on DM.

The ash contents of cotton gin trash produced from companies in Turkey were significantly lower than those reported by Kennedy and Rankins (2008) and Holt et al. (2003) who reported that the ash contents of cotton gin trash were 26.6% and 32.1% on DM respectively, whereas the ash contents of cotton gin trash produced from companies in Turkey were comparable with that reported by Pordesimo et al. (2005) who found that the ash contents of cotton gin trash were 10% on DM.

In the current study, ash contents were the most variable component of gin trash. The discrepancy in terms of chemical composition among studies were possibly associated with differences in variety, growing conditions, type of harvest method applied (Bader et al. 1998). It was very difficult to say precisely why some of gin trash obtained in the current study had higher ash contents since cotton comes for gin from different areas. However ash content of gin trash was affected by the amount of sand in the gin trash; therefore, cotton grown sandy soil or harvested by stripper would produce gin trash with higher ash content (Baker et al. 1994). Therefore the high ash content of gin trash analyzed in the current study might be attributed to sandy soil and harvester.

In the current study, CP was the second most variable component of gin trash. Lalor et al. (1975) reported that the CP contents of cotton gin trash depend on both the amount of immature seed remaining in the gin trash and weather condition during the growing and harvesting periods. The CP contents of cotton gin trash produced by Companies II and V were comparable with those proposed as the minimum requirements for lactation (12% of DM) and growth (11.3% of DM) in ruminants (ARC 1984). Therefore cotton gin trash produced by Companies II and V has the potential for ruminant animals to meet the protein requirements during the critical periods when there is a shortage of high-quality forages. The cotton gin trash produced by Companies I, III and IV should be supplemented with protein sources to meet the requirements of lactation and growth of ruminants.

The gas productions, ME, OMD of cotton gin trash were presented in Table 2. The origin of cotton gin trash had significant effect on the gas production, ME, OMD of cotton gin trash.

Table 2. Gas production, metabolizable energy and organic matter digestibility of cotton gin trash from different companies.

	Companies
Parameters	I	II	III	IV	V	SEM	P
GP	22.91^d	32.23^b	26.98^c	23.26^d	33.51^a	0.395	*
ME	5.38d^e	6.53^b	5.74^c	5.69^c	7.09^a	0.028	*
OMD	37.44^e	51.87^b	42.06^c	39.38^d	52.69^a	0.108	*

Note: ^a–^cRow means with common superscripts do not differ (P < 0.05).

SEM, standard error mean; P, significance level; GP, gas production (mL/200 mg of DM) at 24 h, ME, metabolizable energy (MJ /kg DM); OMD, organic matter digestibility%.

* P < 0.001.

There were also significant variations in cotton gin trash produced by different companies in terms of gas production and estimated parameters such as OMD and ME contents of cotton gin trash. The gas productions of cotton gin trash from Companies II and V were significantly higher than the others. The gas production ranged from 22.91 to 33.51 ml of 200 mg of DM after 24-h incubation. The ME and OMD contents of cotton gin trash ranged from 5.38 to 7.09 MJ/kg DM and 38.80 to 51.28% respectively. The ME and OMD of cotton gin trash from Companies II and IV were significantly higher than the others.

The variation in gas production and estimated parameters among cotton gin trash could be attributed to compositional differences of cotton gin trash, especially cell wall and CP contents. The nature and level of cell contents were the main factors which determine the amount of gas to be produced during the fermentation (Babayemi et al. 2004). Gas produced during the fermentation was associated with volatile fatty acid production so the more fermentation of a substrate the greater the gas production (Blummel & Orskov 1993). Although there was considerable amount of cotton gin trash production in Turkey, there was no available information about the biomass production of cotton gin trash as a roughage source for ruminant animals. It would be more useful if further studies should be focused on the biomass production potential of cotton gin trash in Turkey.

The ME contents of cotton gin trash produced by Companies II and IV were considerable higher than those reported by Holt et al. (2003) and Pordesimo et al. (2005) who found that the ME contents of cotton gin trash were 6.75 and 4.58 MJ/kg DM respectively whereas ME contents of cotton gin trash produced by the other companies in Turkey fall in that range reported by Holt et al. (2003) and Pordesimo et al. (2005). The reason why the ME contents of cotton gin trash produced by Companies II and IV are higher than those reported by Holt et al. (2003), and those by Pordesimo et al. (2005) had a low level of cell contents of cotton gin trash. It was indicated that the ME content of forage is negatively correlated with cell wall contents of feedstuffs (Kamalak et al. 2005).

It was very interesting to notice that the OMD values of cotton gin trash produced by Companies II and V were significantly higher than those for Companies I, III and IV even if the ash contents of cotton gin trash produced by Companies II and V were higher than those for Companies I, III and IV. Therefore the low digestibility of cotton gin trash produced by Companies I, III and IV would decrease the feed intake and production of ruminant animals. However, Pordesimo et al. (2005) showed that it was possible to increase the digestibility of the cotton gin trash by treatment with NaOH.

The most important limitation of the use of cotton gin trash as a roughage in ruminant diet is the chemical residue due to application of pesticides and defoliants throughout growing season of cotton plant. There is no available information about established tolerance levels of chemical residues in cotton gin trash to use safely in ruminant diets (Buser 2003). On the other hand, Stewart et al. (1998) reported that chemical residues in cotton gin trash due to application of pesticides and defoliants throughout growing season of cotton plant did not appear to be present at concentrations that cause a problem to the animal.

It is very difficult to suggest the inclusion rate of cotton gin trash into diets of different ruminant animals. However Myer (2007) suggested that 5% or less cotton gin trash could be included into the diet of finishing cattle to help maintain proper function of digestive system. Kennedy (2006) also showed that the cotton gin trash at% 45 of can be included into diet of beef cattle without any adverse effect on the performance.

4. Conclusion

In conclusion, chemical characterization of CP, OMD and ME suggests that the cotton gin trash moderate level of CP concentration and was quite digestible therefore it can be said that cotton gin trash will provide roughage of an acceptable quality for ruminant animals. However chemical residues due to application of pesticides and defoliants throughout growing season of cotton plant should be acceptable when cotton gin trash is used as roughage in ruminant diets.