Effects of levels of urea and coconut oil on rumen ecology, milk yield and composition in lactating dairy cows fed on urea-treated rice straw

M Wanapat, A Petlum and S Chanthai^*

Tropical Feed Resources Research and Development Center, Khon Kaen University, Khon Kaen, 40002, Thailandanan_petlum@yahoo.com
^*Department of Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen, 40002, Thailand

Abstract

Four multi-parous lactating Holstein Friesian crossbred dairy cows were randomly allocated into a 2x2 factorial arrangement in a 4x4 Latin square design to receive four dietary treatments; Urea2CO2 = 2% urea + 2% coconut oil, Urea2CO4 = 2%Urea + 4% coconut oil, U4CO2 = 4%Urea+2%cocobut oil and U4CO4 = 4%Urea + 4% coconut oil.

Digestion coefficient of crude protein was significantly improved by higher level of oil but with no effect on DM and OM digestibility. Increasing level of oil enhanced C₃ and C₄ production and decreased C_2,thus lowering C₂/C₃ ratio.

Keywords: Urea, coconut oil, dairy cows

Introduction

Using a high level of cassava chips and cassava hay in ruminant diets (Wanapat and Petlum 2001; Wanapat et al 2001) provided more opportunity of using higher level of NPN as a N source for rumen microbes and microbial protein synthesis. However, densities of energy in diets containing cassava chips and cassava hay have been found to be low due to bulkiness of the cassava hay. Hence it could be possible to enhance energy density by other sources such as oil or fat.

Therefore, the objectives of this experiment were to study the effect of levels of urea and coconut oil in a cassava-based concentrate on digestibility, rumen ecology and milk production in cows fed urea-treated rice straw (UTRS) as roughage source.

Materials and Methods

Four treatments were randomly assigned to a 4x4 Latin square design in a 2x2 factorial arrangement. The treatments were levels of urea (2 and 4%) and coconut oil (2 and 4%) in cassava-based concentrate rations. Four HF-crossbred cows during late lactation were used for this experiment. All cows were fed concentrate and urea-treated rice straw (UTRS) at levels of 1.5 and 1.5 % BW (DM basis), respectively.

Feeds and faeces were sampled for analyses of DM, Ash, OM, CP, EE, NDF, ADF, ADL and AIA. Milk yields were measured and milk samples were analysed for composition using Milko-Scan 33 (Foss Electric, Hillerod, Denmark). Blood samples were analysed for urea-N (BUN). Rumen fluid samples were taken using a stomach tube connected with a vacuum pump, for measurement of pH, NH₃-N and concentration of VFA. Methane (CH₄) production was estimated from the concentrations of C2, C3 and C4 according to the equation of Moss et al. (2000). All data were subjected to ANOVA using GLM, procedures (SAS 1998). Treatment means were compared by Duncan's New Multiple Range Test.

Results and Discussion

Digestion coefficient of crude protein was significantly improved by the higher level of oil but with no effect on DM and OM digestibility (Table 1). Increasing level of oil enhanced C₃ and C₄ production and decreased C_2,thus lowering C₂/C₃ ratio. Oil supplementation improved milk fat percentage.

Table 1. Least square means for digestibility, rumen ecologies and milk productions of cows fed concentrate containing different levels of urea and coconut oil.
	2 % Urea		4 % Urea			Main effects
	2-CCO	4-CCO	2-CCO	4-CCO	SEM	U	CCO	UxCCO
Digestibility, %
DM	51.2	57.3	51.5	50.3	1.58	ns	ns	Ns
OM	55.4	60.7	54.2	52.6	1.98	ns	ns	Ns
CP	46.1^a	59.1^b	41.1^a	50.1^ab	2.30	ns	*	Ns

Ruminal pH	6.8	6.8	6.8	6.8	0.03	ns	ns	Ns
Ruminal NH₃-N, mg %	13.2	14.1	13.8	19.5	1.02	ns	ns	Ns
Volatile fatty acids
Total VFA, mM	91.4	113	109	113	8.34	ns	ns	ns
C_2, %	71.2^a	62.9^b	69.5^a	62.8^b	1.03	ns	**	ns
C₃, %	19.6^a	24.4^ab	20.7^ab	27.2^b	1.10	ns	*	ns
C₄, %	9.2^a	12.7^b	9.8^a	10.0^a	0.22	*	**	**
C₂: C₃	4.0^a	2.7^b	3.5^ab	2.4^b	0.20	ns	*	ns
CH₄, mM	26.8	30.2	32.1	27.7	2.28	ns	ns	ns

BUN, mg %	13.5^a	20.3^bc	15.6^ab	21.3^c	0.79	ns	**	ns
Milk yield, kg/d	6.6	8.1	8.4	6.5	0.49	ns	ns	ns
3.5 % FCM, kg/d	8.2	10.6	10.0	7.4	0.67	ns	ns	ns
Milk composition, %
Fat	5.0	5.2	4.8	4.4	0.22	ns	ns	ns
Protein	3.6	3.6	3.2	3.0	0.13	ns	ns	ns
Lactose	4.6^a	4.7^ab	4.9^b	4.8^ab	0.05	ns	*	ns
Total solids	13.9	14.2	13.6	12.9	0.33	ns	ns	ns
Solids-not-fat	9.0	8.9	8.8	8.5	0.14	ns	ns	ns
^a,b,c Means in the same row with different letters are significantly different (p<0.05)SEM= Standard error of the means, NS= Not significant, = p<0.05, *= p<0.01

Conclusions

The results obtained from this experiment could have a great impact on dairy feeding especially using diets based on local resources.
The utilization of higher levels of NPN as urea can reduce the use of more expensive protein sources especially soybean meal, and supplementation of coconut oil could improve rumen fermentation in terms of the fermentation-end-products.

References

Moss A R, J P Jouany and J Newbold 2000 Methane production by ruminants: its contribution to global warming Ann. Zootech, 49: 231-253.

SAS 1998 SAS/STAT Users Guide: Version 6, 12^th Edn. SAS Institute, Cary, N.C., USA.

Wanapat M and A Petlum 2001 Feeding cassava chip-based rations to lactating dairy cows. In: International Workshop on Current Research and Development on Use of Cassava as Animal Feed. Eds. T R Preston, B Ogle and M Wanapat. Khon Kaen University, Thailand. http://www.mekarn.org/procKK/wana2.htm

Wanapat M, A Petlum, O Poungchompu, P Rowlinson and W Toburan 2001 Effect of cassava hay supplementation and concentrate use on milk yield and composition. In: International Workshop on Current Research and Development on Use of Cassava as Animal Feed. Eds. T.R. Preston, B. Ogel and M. Wanapat. Khon Kaen University, Thailand. http://www.mekarn.org/procKK/wana1.htm