Comparison of feeding urea-treated teff and barley straw based diets with hay based diet to crossbred dairy cows on feed intake, milk yield, milk composition and economic benefits

R Mesfin and I Ledin*

Ethiopian Agricultural Research Organization, Holetta Agricultural Research Center,
PO Box 2003, Addis Ababa Ethiopia
Y_takele@yahoo.com
*Swedish University of Agricultural Sciences,
Department of Animal Nutrition and Management, PO Box 7024, 750 07,Uppsala, Sweden
Corresponding Author: Inger.Ledin@huv.slu.se

Abstract

Six crossbred Boran x Friesian milking cows were used in a double Latin square design to study if urea-treated teff straw or urea-treated barley straw can replace hay in the diet of dairy cows. Feed intake, milk yield, milk composition and economic variables were used for the evaluation.

As a result of urea treatment, crude protein (CP) content of teff and barley straws increased by 134% and 85% respectively and in vitro organic matter digestibility by 7.4% and 28%, respectively. Neutral detergent fibre and hemicellulose content of teff and barley straws was reduced, while acid detergent fibre and lignin increased. There was no significant difference in milk yield or milk composition due to the experimental diets. The diet with urea treated teff straw gave the highest daily net return.

Urea treatment increased the nutritive value of teff and barley straw and these roughages can replace hay in the diet of dairy cows with no loss of  milk yield or change in composition. .

Key words: Barley straw, Boran*Friesian, Ethiopia, milk yield, teff straw, urea treatment

Introduction

Grazing, crop residues and hay from natural pastures form the basal diet of livestock in the highlands of Ethiopia. Crossbred cows are stall-fed mainly on native hay, concentrate feeds and mixed cereal straws. Hay is, however, becoming increasingly expensive owing to the scarcity of land and the cost of concentrate is also increasing due to limited and inaccessible grain milling factories.

Farmers produce and conserve considerable amounts of cereal straws every year, making this feed resource very important. Teff (Eragrostis teff) and barley (mainly Hordeum vulgare) straw are commonly produced in the highlands of Ethiopia, about 3 million tons of teff straw annually accounting for 25 % of the total straw production (Seyoum et al 1996). Similar to other crop residues the straws are low in nutrient content (crude protein, vitamins and minerals) and high in lignocellulose, which makes them less digestible and results in a low intake and lack of readily available energy for rumen microorganisms. According to Seyoum et al (1998), the chemical composition of teff straw and barley straw was 6% and 6.2% CP, 74.5% and 73.2% neutral detergent fibre (NDF), 42.4% and 45% acid detergent fibre (ADF) and 7.7% and 6.3% lignin. A feed intake study with sheep revealed higher intake with urea supplemented teff straw (354 g/d) than molasses supplemented teff straw (326 g/d), indicating that the first limiting factor is nitrogen (Nuwanykpa and Butterworth 1987). Dry matter digestibility (DMD) was 53.2% and 48.0%, respectively. Due to the unbalanced nutrient content, straw by itself cannot support ruminant production, more than providing for maintenance (Kudo et al 1994).

Different alkali treatments have been used to improve the feeding value of crop residues at farm and industrial levels. Urea treatment represents one of these methods to improve poor quality roughage in ruminant feeding. Wanapat et al (1996) indicated that urea treatment improved the CP content of straw by an average of 6 to 7% units and organic matter digestibility (OMD) by 10 to 15% units. According to Kayouli (1996), intake was improved and about 70% of the treated crop residues were edible compared to 30 to 40% for the untreated ones. Feeding urea treated crop residues to dairy cows also increased milk yield from 150 litres to 280 to 350 litres/cow over a period of a month (Kayouli 1996.

Oil seed cakes and bran from cereals can increase milk production owing to the supply of rumen undegradable protein and their high glycogenic potential, respectively (Ocen 1993). According to Chenost and Kayouli (1997), cereal bran and oil seed cakes are less soluble in the rumen. Noug (Guizotia abyssinica) is the most commonly occurring oil seed crop in the highlands of Ethiopia. The cake, after the oil is extracted is a very high quality protein supplement for ruminants (Varvikko 1991). According to Little et al (1987), supplementation of noug cake to crossbred dairy cows increased milk yield by 35%.

The objective of this experiment was to analyse and compare the chemical composition of teff and barley straw before and after treatment with urea and to study the effect of using urea-treated teff straw, urea-treated barley straw or hay in diets on performance of crossbred dairy cows.

Materials and methods

Location and climate of the study area

The experiment was conducted on station, in Holetta Research Center, 45 km west of Addis Ababa, Ethiopia. The area lies at 2400 m above sea level and receives an annual rainfall of 1100 mm with an average maximum temperature of 21.3^oC (18.6-24^oC).

Experimental feeds

The feeds used in the experiment were hay, urea-treated teff straw, urea-treated barley straw, wheat bran, wheat middling, noug cake, molasses, urea and salt. The hay was predominantly composed of Andropogon and Hyparrhenia species. It was harvested after maturity in November from seasonally waterlogged bottomlands. Noug cake, wheat bran, wheat middlings and molasses were purchased from different factories in the area. Common salt was used to supply the Na requirement of the cows.

Procedures for treatment of straws with urea

Treatment was done in an over-ground silo constructed of timber. Urea (5kg) was dissolved in 100 litres of water. The straw, in batches of 20 kg, was spread in the silo. Twenty litres of urea solution were sprinkled uniformly over the straw using a sprinkler. The treated straw was mixed using a fork. Further batches were treated following similar procedures. After treating one layer of straw, it was pressed by tramping before the next layer was placed. The pit was filled and the stack was covered tightly with a plastic sheet to exclude the entrance of oxygen and prevent ammonia from evaporating. The stack was loaded with sacks full of sand. The treated straw was kept for a month before opening for feeding as recommended by Chenost and Kayouli (1997). In order to have continued access to treated straws; the urea treatment was repeated at a minimum of one month after the first treatment.

Animals and management

Six lactating crossbred Boran * Friesian cows were selected from the dairy cattle herd of Holetta Agricultural Research Center for the study. The cows had calved in the same month and were in different parities, ranging from 1 to 8, and had different ages, ranging from 2.0 to 4.8 years. Body weights ranged from 309 to 421 kg. The experiment was commenced after the cows had passed the lactation peak at 98 ± 13 days in lactation. The cows were de-wormed for internal parasites with Albendazole one week before the start of the experiment and were fed individually in tie stalls.

Urea-treated teff straw, urea-treated barley straw and hay were divided in two equal parts for morning and afternoon feeding. Molasses was diluted with water (1:3, molasses: water) daily in the morning and given together with the roughages. The concentrate mixture, including wheat bran, wheat middling, noug cake and salt was fed in equal portions at milking in the morning and in the afternoon. Drinking water was available at all times. The cows were let out for exercise for 15 minutes daily in the morning after milking. They were milked by hand twice daily at 15:00 h in the afternoon and 05:00 h in the morning.

Experimental design

The experiment was conducted using a double 3*3 Latin Square Design. The decrease in milk yield as lactation stage proceeded was accounted for by the period effect. The experiment was run for three consecutive periods of 36 days each. Each period consisted of 15 days of adaptation and 21 days of data collection.

The three experimental diets were formulated to have the same content of metabolisable energy (ME) and CP and were calculated for the requirements of a cow of 400 kg with a milk yield of 11 litres/day (1308 g CP and 108 MJ ME according to NRC (1989)). Preliminary feed analysis (Table 1) was done and the results were used in the diet formulation. The intakes of hay, treated straws and molasses were tested before the start of the experiment. Based on this information, the level of hay, treated straws and molasses was fixed during the experiment. The composition of the concentrate was decided using different proportions of the feedstuffs to obtain the planned nutrient content.

Measurements, sampling and chemical analysis

Total daily milk yield was recorded and milk samples were analysed fortnightly. The milk samples were analysed for fat by the Gerber method (BSI 1989) and for protein based on the formaldehyde titration method (Pyne 1932). Before the start of the experiment and for the purpose of diet formulation, samples from each feed ingredient were taken for analysis of DM, ash and CP according to AOAC (1990) and in vitro organic matter digestibility (IVOMD) by Tilley and Terry (1963). During the entire period of the experiment, daily samples of feed offered were bulked for a period and feed samples from the refusals were taken and bulked for two weeks and were analysed for DM, ash, CP and IVOMD by the same methods as above. ME was derived from % IVOMD: ME = 0.016*g IVOMD/kg according to McDonald et al (1995. Samples from the treated and untreated straws were also analysed for NDF, ADF, ADF-ash and lignin by the methods described in Van Soest and Robertson (1985).

Statistical analysis

DM intake, daily milk yield, milk fat and milk protein were analysed using Minitab Statistical Software (Minitab Version 12.21, 1998) using the ANOVA procedures in GLM. To minimise the carry-over effect, data of the last 21 days were used for the analysis. The statistical model used was:

Y_ijk=µ+r_i+c_j+t_k(ij)+e _ijk

Where:

Y_ijk is the dependent variable (feed intake, milk yield, milk fat and milk protein),
µ overall mean,
r_i effect of lactation stage (period effect),
c_j effect of cow,
t _k(ij) effect of diet and
e_ijk random variation.

Economic analysis

The economic evaluation was based on calculation of the total cost of production. The milk price was fixed at 1.25 Ethiopian birr/litre (8.3 ETB~1USD) which was the official price at the Dairy Development Enterprise. A milk price of ETB 1.83/litre based on the price paid by consumers to the small-scale commercial milk producers was also included as a comparison.

Results

Nutrient content of treated straws, untreated straws, hay and concentrates

There CP content increased by 134% and 85% respectively when teff straw and barley straw were treated with urea. The IVOMD for teff straw increased by 7.4% and barley straw by 28% as a result of the urea treatment. With regard to the cell wall constituents, NDF of teff and barley straw were reduced by 3.4% and 1%, respectively. The hemicellulose content of teff and barley straw was also reduced by 19.3% and 22%, respectively. On the other hand,  increases in ADF content of 9% and 11% and in lignin content of 57.5% and 29.5% for teff and barley straw respectively were observed.

Table 1. Chemical analysis of feedstuffs and chemical composition of feeds (means and standard error)
Feed	No of samples	DM, g/kg	Ash, g/kgDM	CP, g/kg DM	IVOMD, g/kg DM
Hay	11	893	90	59	556
Teff straw	11	951	71	38	566
Teff straw, UT	11	419	68	89	608
Barley straw	11	944	63	40	464
Barley straw, UT	11	437	70	74	594
Wheat bran	11	921	46	151	821
Wheat middlings	11	909	32	118	885
Noug cake	11	943	88	312	693
Molasses	11	700	-	64	794
Feeds offered in the experiment
Hay	6	896±0.7	90±0.6	59±0.4	557±0.7
Teff straw, UT	6	408±0.5	90±0.4	77±0.6	665±0.5
Barley straw, UT	6	415±0.6	96±0.6	76±0.6	638±0.4
Concentrate (diet with hay)	2	897±0.1	128±0.2	254±0.1	574±0.5
Concentrate (diet with UT teff straw)	2	898±0.2	124±0.1	261±0.2	580±0.8
Concentrate (diet with UT barley straw)	2	893±0.1	115±0.2	239±0.4	594±0.3
1Average of 2 replicates of one sample, DM=Dry matter, CP=Crude protein, IVOMD=In vitro organic matter digestibility, UT=Urea treated

Table 2. Fibre content of treated and untreated straws (mean and standard error, 2 samples)
Feed	NDF,  g/kg DM	ADF, g/kg DM	Hemicellulose, g/kg DM	Lignin, g/kg DM	ADF-ash, g/kg DM
Teff straw	788±0.02	446±0.02	342±0.1	40±0.05	35±0.02
Teff straw, UT	761±0.1	486±0.1	276±0.03	63±0.01	41±0.1
Barley straw	789±0.1	502±0.06	288±0.04	61±0.1	24±0.07
Barley straw, UT	782±0.05	557±0.1	224±0.05	79±0.02	30±0.05
UT=Urea treated, NDF=Neutral detergent fibre, ADF=Acid detergent fibre

Daily feed and nutrient intake of experimental cows

Approximately 99 %, 93% and 92 % of the hay, urea-treated teff straw and the urea-treated barley straw offered respectively were consumed. The total DM intake of thediet with hay (11.3 kg) was significantly higher than for the diets with urea-treated teff straw (9.9 kg) or barley straw (9.7 kg). However, there was no difference between the two straw diets. The total ME intake of the urea-treated teff diet was significantly higher and the CP intake lower than the intake of the hay diet and the urea-treated barley straw diet.

Table 3.  Feed offered and feed intake in the experiment (LS-means and SE)
	Diet with hay	Diet with teff straw, UT	Diet with barley straw, UT	SE
Feed offered, kg DM/day
Hay	8	-	-	-
Teff straw, UT	-	7	-	-
Barley straw, UT	-	-	5.5	-
Wheat bran	0.5	0.3	1.1	-
Wheat middlings	0.4	0.2	0.3	-
Noug cake	2.3	1.7	2.0	-
Salt	0.1	0.1	0.1	-
Molasses	-	1.2	1.2	-
Total DM offered, kg/day	11.3	10.5	10.2	-
Total ME offered, MJ/day	108	109	108	-
Total CP offered, g/day	1304	1307	1308	-
Feed intake, kg DM/day
Hay	7.95	-	-	0.06
Teff straw, UT	-	6.53	-	0.06
Barley straw, UT	-	-	5.1	0.06
Wheat bran	0.5	0.3	1.1	-
Wheat middlings	0.4	0.2	0.3	-
Noug cake	2.3	1.7	2.0	-
Salt	0.1	0.1	0.1	-
Molasses	-	1.1	1.1	0.02
Total DM intake, kg/day	11.3a	9.9b	9.7b	0.07
Total ME intake, MJ/day	101b	105a	99b	1.0
Total CP intake, g/day	1268a	1157b	1264a	10.0
Total DM intake, g/kg W0.75	132 a	115b	115b	1.0
Intake of UT straw, g/kg 0.75	-	76a	61b	1.0
ab means between columns within a row withiut common superscript are different at P<0.05, UT=urea treated. LS-means=Least square means, SE=Standard error

Effect of experimental diets on milk yield, milk fat and milk protein

There were no significance differences in milk yield, milk protein or milk fat among the experimental diets (Table 4).

Table 4. The effect of feeding diets with hay, urea treated teff straw or urea treated barley straw to  cross bred dairy cows on milk yield, milk fat and milk protein (LS-means and SE)
	Hay	Teff straw, UT	Barley straw, UT	SE
Milk yield, litres/day	6.82	7.17	6.75	0.12
Milk fat, %	4.23	4.42	4.54	0.13
Milk protein, %	3.47	3.36	3.35	0.06
UT = urea treated LS-means=Least square means, SE=Standard error

Economic analysis

According to the cost-profit analysis calculated for each diet (Table 5), the diet with hay resulted in the highest cost of production, followed by the diet with urea-treated teff straw. The diet with hay had the lowest net return, whereas the diet with urea treated teff straw had the highest net return.

Table 5. Cost benefit analysis of the diets based on hay, and urea-treated teff and barley straws
	Hay	Teff straw, UT	Barley straw, UT
Production cost, ETB/day	7.1	6.75	6.59
Milk yield, litres/cow/day	6.9	7.2	6.8
Price paid by the Dairy Development Enterprise
Milk price, ETB/litre	1.25	1.25	1.25
Gross return, ETB/cow/day	8.63	9.00	8.50
Net return, ETB/cow/day	1.53	2.25	1.91
Benefit cost ratio	1.22	1.33	1.29
Marginal rate of return		2.13:1
Price paid by the consumers
Milk price, ETB/litre	1.83	1.83	1.83
Gross return, ETB/cow/day	12.63	13.18	12.44
Net return, ETB/cow/day	5.53	6.43	5.85
Benefit cost ratio	1.78	1.95	1.89
Marginal rate of return