Effects of urea, soybean meal and blood and feather meal mixture on rumen characteristics and performance of Brahman crossbred cattle

N T Ngu, N T H Nhan, N V Hon, L H Anh, N Thiet¹ and L T Hung²

College of Agriculture, Can Tho University, 3/2 Street, Can Tho City, Vietnam
ntngu@ctu.edu.vn
¹ Faculty of Rural Development, Can Tho University, 3/2 street, Can Tho City, Vietnam
² School of Agriculture and Aquaculture, Tra Vinh University, 126 Nguyen Thien Thanh, Tra Vinh City, Vietnam

Abstract

To examine the effects of urea and different protein source supplementation on cattle, 28 crossbred Brahman cattle were arranged in a 90-day feeding trial with 7 treatments and 4 replicates. The basal diet consisted of Hymenachne acutiglum grass (1% body weight, DM basic), rice straw (ad libiltum) and rice bran (1.5 kg/head/day). Treatment diets were U1 and U2 at 30 and 60 g urea/100 kg BW/day, respectively; soybean meal at 360 g (SBM1) and 720 (SBM2) g/head/day; blood and feather meal (50:50) at 360 g (BFM1) and 720 g/head/day (BFM2). Rumen fluid was collected for measurements of pH, NH₃-N and bateria enumeration and volatile fatty acid (VFA) analy Weight of cattle was taken at the beginning and the end of the experiment. It was shown that rumen pH was not affected by diets but NH₃-N content was higher in the U2 diet. Total bacteria were highest on the SBM2 ration. The supplementation of either soybean meal or blood plus feather meal resulted in improved weight gain. Addition of urea to the basal diet had a lesser effect on growth rate. Growth rate was positively related with molar proportion of propionate in the rumen VFA.

Keywords: bypass protein, cellulolytic bacteria, protein supplementation, weight gain

Introduction

Protein in the diet plays an important role in the nutrition of ruminants. In addition to the supply of amino acids as rumen bypass protein (Preston and Leng 1987) . It is also a nitrogen source for the synthesis of bacterial proteins (Nocek and Russell 1988). Any deficiency of amino acids provided by microbial protein can be adjusted by providing additional sources of ruminally undegradable protein (Preston and Leng 1987; Merchen and Titgemeyer 1992). Rumen undegradable proteins are those in fish meal, feather meal, blood meal, maize gluten meal, soybean meal (Santos et al 1998). Supplementation with undegradable protein can improve the performance of animals by altering the protein/energy ratio of nutrients that can be absorbed. In addition to ruminally undegradable protein, ruminally degradable protein is also used by rumen bacteria as they feed nutrients to microbial protein. Ruminally degraded protein can come in the form of non-protein nitrogen (NPN) or true protein. Ruminants can use NPN as protein in the diet. Based on the rate and extent of rumen degradation, NPN in feed and supplements such as urea and ammonium salts, is considered to be completely degraded in the rumen (NRC 2001). Many studies have examined the effect of different protein levels on growth (Kabir et al 2004; Kang et al 2012), ruminal fermentation (Davidson et al 2003) and slaughter efficiency (Agnihotri et al 2006; Ryan et al 2007) in sheep was also performed. Thus, the supply of protein sources to the ruminant diet plays an important role in rumen fermentation and protein synthesis of microorganisms, resulting in productivity gains of ruminants. This study was carried out to evaluate the effects of protein supplementation on rumen fermentation, microorganisms, feed intake and performance in beef cattle fed on grass and rice straw as basal diet.

Material and methods

The experiment was carried out in An Giang province (10°23' N, 105°26' E), Vietnam on 28 crossbred Brahman cattle with an average body weight (BW) of 176 ±7.5 kg. Cattle were arranged in a completely randomized block design with seven treatments and four replicates, in which body weight was considered a block. The basal diet (control) consisted of Hymenachne acutiglum grass (approximately 1% of body weight, DM basis), rice straw (ad libitum) and rice bran (1.5 kg/head/day). Treatments were different urea levels and protein sources consisting of U1 and U2 at 30 and 60 g urea/100 kg BW/day, respectively; soybean meal at 360 g (SB1) and 720 (SB2) g/head/day; blood and feather meal (50:50) at 360 g (BFM1) and 720 g/head/day (BFM2) (Table 1). Hymenachne acutiglum grass was divided into two parts and fed at 08:00 and 14:00 daily. Rice straws were supplied freely in the evening. Urea was dissolved in water and sprayed on rice straw. Soybean meal, blood meal and feather meal were mixed with rice bran and given twice a day before feeding grass. All cattle were offered the basal diet within 15 days before starting the 90-day experiment. At the end of the study, about 200 ml rumen fluid was collected before feeding by a stomach tube. Ruminal pH was immediately determined by pH meter (Delta-320, Mettler Toledo, USA). The concentration of ammonia nitrogen (NH₃-N) was determined by Kjeldahl method. The volatile fatty acids (VFA) were analyzed by using High Pressure Liquid Chromatography (Mathew et al 1997).

Cattle were weighed in the morning before feeding on two consecutive days at the start of the experiment, after 30 days, 60 days and at the end of 90 days. Feed offer and refusal samples were collected daily for DM determination. The digestion trial was performed in the last 7 days of the experiment. In this period, all feces were collected daily, weighed and samples were taken to be stored at -20^oC. Feed and feces samples were dried at 60°C and ground (Retsch, Germany) for further analysis (Table 2; AOAC 1990). Neutral detergent fiber (NDF) and Acid detergent fiber (ADF) were analyzed by the procedure of Van Soest et al (1991).

For quantification of rumen bacteria by real-time PCR, rumen samples were pooled for DNA extraction. Microbe genomic DNA extraction was done following the CTAB-based protocol described by Minas et al (2011). The primers used in PCR and real-time PCR were taken from Denman and McSweeney (2006) for total bacteria and from Koike and Kobayashi (2001) for R. albus, F. succinogenes, and R. flavefaciens quantification. For methanogens, the primer pair was picked from Denman et al (2007). The standard curves were generated following the instruction of the manufacturers. In brief, purified PCR products were cloned in TOPO ^® TA Cloning^® Kits (Invitrogen). The recombinant plasmids were then extracted by the PureLink^® Quick Plasmid Miniprep Kits (Invitrogen). DNA plasmids were diluted with concentration from 10⁸ to 10¹. Real-time PCR assays were performed on ABI Prism^Ò 7000 SDS machine (Applied Biosystems), based on the fluorescent component changes with the increase of the product. The number of DNA copy was calculated based on threshold cycle (C_T) value and via dissociation curve analysis (Petri et al 2013).

The data were subjected to analysis of variance using the General Linear Model procedure of Minitab software version 16.2.1. Tukey's pairwise comparisons (p <0.05) were applied to determine differences between dietary treatments.

Results and discussion

Effects of urea and protein source supplementation on rumen characteristics

In general, different supplemental sources did not lead to changes in pH values but in NH₃-N concentration (P <0.01), of which urea supplemented diet provided the highest value of NH₃-N (180.9 mg/L) (Table 3). It is known that urea is a rapidly and totally degradable non-protein nitrogen source whereas soybean meal is a moderately rumen degradable plant protein source with high rate of industry use; BFM mixture is a slowly rumen degradable animal by-product protein source (NRC 2001). For rumen parameters, the nitrogen available in the rumen is very important for rumen microbes; cellulolytic bacteria used NH₃-N as a major nitrogen source for their cell protein synthesis. Although by-pass protein is advantageous for the host ruminant to receive good quality protein directly from the diet, nitrogen available for rumen microbes for their growth and cell activities is equally vital and unavoidable. However, the release of NH₃ in the rumen occurred more rapidly than NH₃ utilization by rumen bacteria; therefore, NH₃ would accumulate in the rumen and can be toxic (Cherdthong and Wanapat 2010).

The current study showed that supplementation of urea at 60 g urea/100 kg BW/day would result in higher amount of NH3-N with 181 mg/L, as compared with other supplemented diets (p<0.001). Our result confirmed the report of Sawyer et al (2012) that adding urea in the diet led to higher NH3-N concentration in the rumen due to its solutability and quick convertion into ammonia.

In terms of rumen microbes, the number of total bacteria was lowest under blood and feather meal supplements (Table 2). Among cellulolytic bacteria group, Fibrobacter succinogenes was the highest but these values were constant in rumen of cattle having different diets. In addition, the presence of Ruminococcus albus was highest in soybean meal supplemented diet. In the study by Coomer et al (1993), it was shown that soybean meal with average speed of degradation in the rumen was capable of assimilating and providing nitrogen, thus it created favorable conditions for the growth of rumen bacteria. The present results are in agreement with those reported by Koike and Kobayashi (2001; 2009), Micealet-Doreau et al (2001) and Firkins and Yu (2006) showed thatFibrobacter succinogenes population was always more dominant than Ruminococcus flavefaciens and Ruminococcus albus species in the rumen cellulolytic bacteria population. Previously, Huntington and Archibeque (2000) stated that the degradation activity of proteolytic bacteria depended on the chemical and structural properties of the protein as well as the bacterial species in the rumen; therefore, the addition of different proteins to the diet will affect the growth of microbial communities in the rumen. In support of this view, current research also showed that groups of bacteria were present at different densities in different protein sources. Specifically, when SBM2 was added to the cow diet, the numbers of R. albus (19.8 x 10⁵) and total bacteria (7.51 x 10¹¹) were higher and different from other diets. According to Chanthakhoun et al (2012), the bacterial population increased with increased crude protein diet, namely total bacterial population, Fibrobacter succinogenes and Ruminococcus albus. Indeed, the study by Owens et al (2014) showed that, in the rumen, the supply of true protein might alter the supply of nitrogen (ammonia, peptides, certain amino acids, nucleic acids) and might therefore alter the microflora or their diversity and the growth of these groups of bacteria.

In terms of VFA, acetate appeared to be the highest in the control treatment (68.0 mol/100 mol) while the lowest concentration was in rations with soybean meal and blood and feather meal supplementation. The propionate and butyrate content was similar among diets, but the acetate/propionate ratio was greater in the control treatment.

The present result showed that cattle fed with U2 supplement created the highest NH₃ content.. In general, all protein supplemented diets exhibited lower levels of VFA than control diets. In addition, in the present work, when supplemented with the same protein concentration in the diet, the slow-release protein BFM1 exhibited lower propionate content than SBM1. Similarly, Khorasani et al (1994) reported that the concentrations of propionate, isobutyrate and valerate in rumen of cattle were lower in fish meal, corn gluten meal and meat meal than in fast-degrading protein sources (cocoa powder and SBM).

Effects of urea and protein source supplementation on live weight gain, dry matter intake and nutrient digestibility

Rations with blood and feather meal supplement led to better daily gain compared with other diets. The present results show that the addition of SBM and BFM has enhanced cattle growth rate. According to Preston and Leng (1987), glucose precursors may limit animal productivity. These ideas were confirmed by this study when live weight gain was linearly related with the molar percentage of propionic acid in the rumen VFA (Figure 2). Similarly, Cridland (1984) reported that the contribution of propionate to glucose synthesis ranged from 80 to 90% in sheep fed roughage diets. In the present study, the diets supplemented at 360 g/day blood and feather meal and 720 g/day soybean meal had lower ratio C2:C3 ratios (Table 3) and thus may contribute more glucose precursor in these treatments. As a result, live weight gain was highest in those treatments (Table 4 and Figure 2).

Figure 1. Effect of supplements of urea, soybean meal and blood and feather meal on live weight gain of cattle fed a basal diet of Hymenachne acutiglum grass, rice straw and rice bran

Figure 2. Live weight gain was linearly related with the molar % of propionic acid in the rumen VFA

Figure 3. Feed conversion was improved with a linear trend as the proportion of propionate in the rumen VFA was increased

According to De Leon et al (2001), supplementation of FM or SM to DM was reported to improve dry matter (DM) intake, average daily gain (ADG), and feed conversion ratio (FCR) of growing cattle. Bypass proteins and microbial proteins are two of the sources of metabolized intestinal protein and the addition of fish meal or soya bean meal rations has been demonstrated to improve the intake of dry matter, average daily gain and feed conversion ratio of cattle (Preston and Willis 1974; Preston and Leng 1987; De Leon et al 2001; Parish and Rhinehart 2008). The results of Sawyer et al (2012) suggested that the addition of 40 g bypass protein/day could replace 160 g/d of rumen degradation protein and could maintain the rumen function. High percentage of rumen undegradable protein sources can improve host protein utilization by providing lesser amounts of nitrogen loss in the rumen and metabolic nitrogen. Similar findings have been reported by Knaus et al (2002), in which the supplementation of blood meal in diet contributed to better weight gain (1272g/head/d). In another study comparing the effects of urea and urea combined with bypass protein, Sindt et al (1994) concluded that young calves (7-10 months of age) could gain weight faster and more effectively in the early stages if supplemented with bypass protein plus urea, compared to urea supplementation alone.

Conclusions

• The supplementation of either soybean meal or blood plus feather meal resulted in improved weight gain of cross-bred Brahman cattle fed grass and rice straw as basal diet.
  
  
• Addition of urea to the basal det had only a lesser effect on growth rate.
  
  
• Growth rate was linearly and positively related with molar proportion of propionate in the rumen VFA

Acknowledgment

This research was funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 106-NN.05-2013.04.

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Received 7 February 2019; Accepted 9 May 2019; Published 4 June 2019

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