Effects of lanthanum on rumen fermentation, urinary excretion of purine derivatives and digestibility in steers

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Animal Feed Science and Technology 142 (2008) 121–132

Effects of lanthanum on rumen fermentation, urinary excretion of purine derivatives and digestibility in steers Q. Liu a,∗ , C. Wang a , Y.X. Huang a , K.H. Dong a , W.Z. Yang a,b , H. Wang a a

b

College of Animal Sciences and Veterinary Medicines, Shanxi Agricultural University, Taigu, Shanxi 030801, PR China Agriculture and Agri-Food Canada, Research Centre, P.O. Box 3000, Lethbridge, Alta., Canada Received 14 November 2006; received in revised form 8 June 2007; accepted 2 August 2007

Abstract The objective of this study was to evaluate the effects of LaCl3 supplementation on rumen fermentation, urinary excretion of purine derivatives and feed digestibility in the total tract of steers. Eight ruminally cannulated Simmental steers (420 ± 20 kg) were used in a replicated 4 × 4 Latin square experiment. The treatments were control (without LaCl3 ); La-low; La-medium and La-high with 450, 900 and 1800 mg LaCl3 per steer per day, respectively. Diet consisted of 600 g/kg corn stover and 400 g/kg concentrate (dry matter [DM] basis). Dry matter intake (averaged 9 kg/day) was restricted to a maximum of 90% of ad libitum intake. Ruminal pH (range of 6.59–6.42) was quadratically (P<0.04) changed, whereas total volatile fatty acids (VFA) concentration (range of 74.16–88.61 mM) was linearly (P<0.01) and quadratically (P<0.01) increased with increasing La supplementation. Ratio of acetate to propionate decreased linearly (P<0.01) from 3.28 to 1.79 as La supplementation increased due to the increased in propionate production. In situ ruminal neutral detergent fibre (aNDF) degradation of corn stover was improved but the crude protein (CP) degradability of soybean meal was decreased with increasing La supplementation. Urinary excretion of purine derivatives was quadratically (P<0.01) changed with altering La supplementation (75.5, 81.0, 82.4 and 70.6 mmol/day for Abbreviations: ADF, acid detergent fibre; BW, body weight; Ce, cerium; CP, crude protein; DM, dry matter; ED, effective degradability; N, nitrogen; NDF, neutral detergent fibre; OM, organic matter; PD, purine derivative; REE, rare earth elements; VFA, volatile fatty acids ∗ Corresponding author. Tel.: +86 354 628 9115; fax: +86 354 628 8052. E-mail address: [email protected] (Q. Liu). 0377-8401/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.anifeedsci.2007.08.002

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control, low-, medium- and high-LaCl3 supplementation, respectively). Similarly, digestibilities of organic matter, aNDF and CP in the total tract were also linearly and quadratically increased with increasing La supplementation. The present results indicate that supplementation of diet with LaCl3 improved rumen fermentation and feed digestion in beef cattle. It was suggested that the La stimulated the digestive microorganisms or enzymes in a dose-dependent manner. In the experimental conditions of this trial, the optimum La dose was about 900 mg LaCl3 per steer per day. © 2007 Elsevier B.V. All rights reserved. Keywords: Rare earth elements; Rumen fermentation; Digestibility; Urinary purine derivatives; Beef cattle

1. Introduction The use of feed additives such as antibiotics has proven to be effective by improving nutrient utilization leading to improved feed conversion ratio and better growth rate in most cases. However, there is increasing public concern about the use of feed antibiotics in livestock production due to the possible development of drug resistance in human pathogenic bacteria. Accordingly, the scientific community and animal feed industry have been actively searching for alternatives to feed antibiotics and growth promoters to manipulate rumen fermentation and to improve feed efficiency. Rare earth elements (REE) including La, Ce and other lanthanides are a group of elements with many similarities in chemical and biochemical characters. In China, salts of the REE (La, Ce among others) have been used as feed additives in animal production for many years. Numerous reports from the Chinese scientific community indicate that a small amount of REE mixtures in the diet increase not only the liveweight gain of pigs, cattle, sheep and chickens but also milk and egg production (Shen et al., 1991; Wang and Xu, 2003). Daily gain of fattening beef cattle increased by 7.3 and 8.2% in animals fed 300 and 500 mg REE/kg of DM, respectively (He et al., 1994). The supplementation of 100 mg La/kg of diet increased the average daily gain and feed conversion ratio of pigs by 13 and 7%, respectively. Recently, a number of studies have been conducted under western production conditions; the results showed that supplementation of chlorides of REE such as LaCl3 , CeCl3 or a mixture of LaCl3 and CeCl3 improved the performance of growing pigs and chicken (He et al., 2001; Halle et al., 2003). In addition, studies have also shown that dietary application of REE did not impair or harm the health state of any animal tested within the scope of European feeding trials (Rambeck et al., 1999; He et al., 2001). This coincides with reports from Chinese literature as well as with general literature on oral toxicity of REE (Ji, 1985; Fiddler et al., 2003). Furthermore, little accumulation of La and Ce in muscle, liver and kidneys were observed during feeding trials performed on pigs with diet supplemented with REE (He and Rambeck, 2000; Rambeck et al., 2004). Therefore, REE may be potentially developed as a new, safe and inexpensive alternative growth promoter. However, information on the effects of dietary supplementation of REE on rumen fermentation, nutrient digestibility as well as the mode of action of REE in the digestive tract of ruminants is very limited. The aim of this work was to study the effects of La supplementation on ruminal pH and fermentation, urinary excretion of purine derivatives (PD) and nutrient digestibility in the total tract of beef cattle.

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2. Materials and methods 2.1. Animals and expeirmental design Eight ruminally cannulated Chinese Simmental steers averaging 2.5-year-old and 420 ± 20 kg of body weight (BW), were assigned to a replicated 4 × 4 Latin square. The treatments were: control (without LaCl3 ), La-low, La-medium and La-high with 450, 900 and 1800 mg LaCl3 per steer per day, respectively. The supplement of lanthanum chloride analytical grade (450 g of LaCl3 /kg) was purchased commercially and was added into the concentrate portion when it was pelleted in the feed mill. Diets consisted of 600 g/kg corn stover and 400 g/kg concentrate (dry matter [DM] basis; Table 1). Feed intake (approximately 9 kg per steer per day) was restricted to a maximum of 90% of ad libitum intake. Experimental periods were 21 days with 11 days of adaptation and 10 days of sampling. Steers were housed in individual pens (3 m × 3 m) for adaptation period and in metabolism cages during the collection period. Steers were fed twice daily at 07:00 and 19:00 h and fresh water was available throughout the experimental period. Orts were measured daily at 16:00 h during the adaptation period, and the amount of feed offered was adjusted for a target of 5% orts. On day 8, steers were restricted to 90% of their respective ad libitum intake determined during the prior 7 days in an attempt to assure no orts during the sampling periods. Samples of diets were collected once weekly for DM determination, and then composited by period. The samples were dried in an oven at 55 ◦ C for 48 h, and ground to pass a 1-mm screen with a mill (FZ102, Shanghai Hong Ji instrument Co., Ltd., Shanghai, China) for chemical analysis. The animals were weighed at the beginning and the end of each period. The experimental protocol was approved by the Animal Care and Use Committee of the Shanxi Agriculture University. Table 1 Ingredient and chemical composition of the basal diet (in g/kg dry matter) Ingredients Corn stover Corn grain, ground Wheat bran Soybean meal Cottonseed cake Rapeseed meal Calcium carbonate Salt Dicalcium phosphate Mineral and vitamin mixa

600 208 40 66 48 20 5 4 3.5 5.5

Chemical composition Organic matter Crude protein Neutral detergent fibre Acid detergent fibre Calcium Phosphorus

101.1 565.1 355.9 15.6 8.2

a

Contained 42 ppm Co, 3500 ppm Cu, 20,000 ppm Fe, 12,000 ppm Mn, 12,000 ppm Zn, 1200 ppm I, 600 ppm Se, 3000 IU/g of vitamin A, 500 IU/g of vitamin D, and 15 IU/g of vitamin E.

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2.2. In situ ruminal degradability Ruminal degradation kinetics of the corn stover and soybean meal used in the present study was measured using nylon bag technique on days 12–14 of the experimental period. The corn stover and soybean meal were ground to pass a 2.5-mm screen with a mill (FZ102, Shanghai Hong Ji instrument Co., Ltd., Shanghai, China). Approximately 3 g of corn stover and 4 g of soybean meal were then weighed in 9 cm × 16 cm nylon bags made of monofilament Pecap polyester (Guangzhou Minyuan Business Co., Ltd., Guangdong, China) with a mean pore size of 47 ± 2 ␮m and heat-sealed. Individual bags were placed into the rumen through the ruminal fistula at 2 h after feeding (except the 0 h bags). The duplicated bags were suspended in the rumen of each steer for 0, 4, 8, 12, 24, 36, 48 and 72 h. An empty bag without sample for each incubation time was also incubated in the rumen as blank bag. All bags were removed at the end of the incubation period and were manually rinsed in cold tap water until the effluent remained clear. The bags were subsequently dried at 65 ◦ C for 12 h and then at 100 ◦ C for 24 h. All bags were weighed to determine DM disappearance. Kinetics of nutrient disappearance in situ in the rumen was estimated using the nonlinear regression procedure of SAS (SAS Inst. Inc., 1996). For each steer, period, and type of feed, the following model was fitted to the percentage of nutrient disappearance (McDonald, 1981): y = a + b(1 − e−c(t−L) )

for t > L

where a is the soluble fraction; b the slowly degradable fraction; c the fractional degradation rate constant at which b is degraded; L the lag time (h) and t is the time of incubation (h). Effective degradability (ED) of feed was determined using ED = a + [bc/(c + k)], where k was the particulate passage rate out of the rumen and was 0.025 h−1 for corn stover and 0.058 h−1 for soybean meal according to our measurements (Liu et al., data not published). 2.3. Rumen pH and fermentation Rumen pH and fermentation characteristics were measured for two consecutive days during days 19 and 20 of the period. At 0, 3, 6, and 9 h after the 07:00 h feeding, rumen fluid was obtained from several sites within the rumen (reticulum, dorsal and ventral sac). Ruminal pH was immediately measured using an electric pH meter (Sartorius Basic pH Meter PB-20, Sartorius AG, Goettingen, Germany). The samples were then strained through four layers of cheesecloth. Five milliliters of filtrate was preserved by adding 1 mL of 250 g/L (w/v) meta-phosphoric acid to determine volatile fatty acid (VFA), and 5 mL of filtrate was preserved by adding 1 mL of 20 g/L (w/v) H2 SO4 to determine NH3 . The samples were subsequently stored frozen at −20 ◦ C until analyses. 2.4. Apparent digestibility in the total tract Steers were dosed via ruminal cannula with 2 g of chromic oxide per day per steer in two equal proportions at 07:00 and 19:00 h beginning 7 days before sampling and continuing throughout the sampling period for use as an indigestible marker of digesta flow. Fecal samples (approximately 200 g wet weight) were collected for each steer from the rectum

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three times daily at various times (3-h intervals) during five consecutive days and composited by steer for each period. After being dried at 55 ◦ C for 48 h, the samples were ground in a feed mill to pass a 1-mm sieve for chemical analyses. Dry matter excreted in feces was calculated by dividing chromium input (grams of chromium per day) by chromium concentration (grams of chromium per kilogram of DM) in the feces. Excretion of other nutrients in the feces was calculated by multiplying DM flow by their concentration in fecal DM. 2.5. Urine collection and PD measurements Urine output was totally collected using urine collection aprons from a 12 to 21 of the period. Urine was collected daily into containers with adding 100 mL/L sulphuric acid (sufficient to maintain pH < 3), weighed, mixed well and 1% daily aliquot was pooled over the 10 day period per animal. At the end of the collection period, 20 mL urine samples was diluted to 100 mL with distilled water, then divided into two subsamples and stored at −20 ◦ C for analysis of allantoin and uric acid. Total urinary PD excreted (mmol/day) were estimated as the sum of uric acid and allantoin. Excretion of the endogenous PD was assumed constant at 0.385 mmol/kg of BW0.75 for individual steer (Chen and Gomes, 1992). 2.6. Chemical analyses Dry matter content of the ingredients (corn stover, concentrate mix) was determined by oven-drying at 65 ◦ C for 24 h. Analytical DM content of oven-dried samples was determined by drying at 135 ◦ C for 3 h (AOAC, 1990; method 930.15). Organic matter (OM) content was calculated as the difference between DM and ash contents, with ash determined by combustion at 550 ◦ C for 5 h. Contents of neutral detergent fibre (aNDF) and acid detergent fibre (ADF) were determined using the methods described by Van Soest et al. (1991) with heat stable alpha amylase and sodium sulfite used in the NDF procedure, and expressed inclusive of residual ash. Content of nitrogen (N) in the samples was determined by the Kjeldahl method (AOAC, 1990; method 976.05). Ruminal VFA were separated and quantified by gas chromatography (GC102AF; Shanghai Specialties Ltd., China) using a 2-m (Ø4-mm) fused PEG2000, Chromsob WAW DMCS column (GC102AF; Shanghai Specialties Ltd., China) with 2-ethylbutyric acid as internal standard. Ammonia N content of ruminal samples was determined using the method of AOAC (1990). Allantoin and uric acid in urine was determined by ultraviolet–visible spectrophotometer UV-2100 using the procedure of IAEA (1997). 2.7. Statistical analyses Data were analyzed using the mixed model procedure of SAS (Proc Mixed; SAS, 1996) to account for effects of square, period within square, animal within square and treatment. The treatment was considered a fixed effect; square, period within square, and animal within square were considered random effects. Data for ruminal pH, VFA and ammonia N were summarized by sampling time and then analyzed using the same mixed model but with time included as a repeated measure using compound symmetry. Linear and quadratic orthogonal

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contrasts were tested using the CONTRAST statement of SAS with coefficients estimated based on the La application rates. Effects of the factors were declared significant at P<0.05 unless otherwise noted and trends were discussed at P<0.10.

3. Results 3.1. Ruminal pH and fermentation Ruminal pH, ammonia N and VFA profiles are shown in Table 2. Mean ruminal pH was quadratically changed with altering the amount of La supplementation but no linear effect was observed with increasing La supplementation. Total ruminal VFA concentration was higher for La supplementation (86.1 mM) than for control (74.2 mM). However, differences in total VFA among La-low, La-medium and La-high were not detected. Molar proportion of acetate was linearly reduced, whereas that of propionate was linearly increased with increasing La supplementation. In consequence, ratio of acetate to propionate was linearly reduced. Ruminal ammonia N content was reduced either linearly or quadratically with increasing La supplementation. The values (mg/100 mL) of the ruminal ammonia N were highest for the control (11.1), and the lowest for La-medium (7.4) supplementation. 3.2. Effective ruminal degradability In situ ruminal digestion kinetics and ED of corn stover and soybean meal are shown in Table 3. For corn stover, the soluble fraction of DM was quadratically changed, whereas a linear increase in ruminal potentially degradable fraction and a linear decrease in degradation rate were observed with increasing La supplementation. The ED of DM was reduced with the high La supplementation, which was likely due to the combination of the lower Table 2 Effects of La supplementation on ruminal pH and fermentation in steers Item

Treatmentsa

S.E.

Contrast, P

Control

La-low

La-medium

La-high

Linear

Quadratic

pH Total VFA (mM)

6.59 74.16

6.51 84.83

6.42 88.61

6.51 84.80

0.06 1.61

<0.25 <0.01

<0.04 <0.01

mol/100 mol Acetate (A) Propionate (P) Butyrate Valerate BCFAb

66.53 20.39 10.53 0.84 1.90

59.03 27.91 10.06 1.04 1.83

55.76 30.27 10.33 1.23 1.91

55.34 31.02 10.49 1.18 2.31

1.36 0.56 0.30 0.08 0.21

<0.01 <0.01 <0.79 <0.16 <0.13

<0.98 <0.01 <0.35 <0.57 <0.39

A:P Ammonia N (mg/100 mL)

3.28 11.10

2.13 9.14

1.85 7.37

1.79 9.05

0.04 0.07

<0.01 <0.01

<0.01 <0.01

a Control (without LaCl ), La-low, La-medium and La-high with 450, 900 and 1800 mg/(steer day) LaCl , 3 3 respectively. b Branch chained VFA, isobutyrate and isovalerate.

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Table 3 In situ ruminal digestion kinetics and effective degradability (ED) of corn stover and soybean meal Item

Treatmentsa

S.E.

Control

La-low

La-medium

La-high

0.105 0.702 0.018

0.189 0.723 0.011

0.269 0.730 0.007

0.115 0.882 0.008

ED

0.399

0.401

0.421

NDF ab b c (h−1 )

0.020 0.905 0.011

0.025 0.885 0.011

ED

0.280

Contrast, P Linear

Quadratic

0.002 0.020 0.001

<0.94 <0.01 <0.01

<0.01 <0.03 <0.01

0.303

0.003

<0.01

<0.01

0.050 0.872 0.011

0.048 0.944 0.007

0.007 0.027 0.001

<0.01 <0.15 <0.01

<0.04 <0.06 <0.01

0.285

0.310

0.263

0.006

<0.01

<0.01

0.437 0.524 0.022

0.424 0.524 0.022

0.431 0.564 0.017

0.377 0.596 0.018

0.003 0.016 0.001

<0.01 <0.01 <0.01

<0.01 <0.78 <0.16

ED

0.583

0.569

0.550

0.513

0.005

<0.01

<0.69

CP ab b c (h−1 )

0.461 0.539 0.037

0.457 0.543 0.032

0.547 0.362 0.021

0.439 0.555 0.010

0.015 0.023 0.004

<0.55 <0.82 <0.01

<0.01 <0.01 <0.77

ED

0.671

0.648

0.628

0.518

0.005

<0.01

<0.01

Corn stover DM ab b c (h−1 )

Soybean meal DM ab b c (h−1 )

a

Control (without LaCl3 ), La-low, La-medium and La-high with 450, 900 and 1800 mg/(steer day) LaCl3 , respectively. b Parameters were calculated from the fitted equation y = a + b(1 − e−c(t−L) ) for t > L, where y = percentage of DM disappearance from the nylon bag at time t, a = soluble fraction, b = slowly degradable fraction, c = fraction rate constant at which b is degraded, L = lag time (h), and t = time of incubation (h). Effective degradability (ED) was calculated using equation a + bc/(c + k), where k = 0.025 or 0.058 h−1 for corn stover or soybean meal, respectively.

soluble fraction and the lower degradation rate compared to other treatments. Regarding the digestion kinetics of NDF, the soluble fraction was linearly increased and the potential degradable fraction tended to be quadratically (P<0.06) changed with increasing La supplementation. The degradation rate and ED were both linearly and quadratically responding to La supplementation with the lowest values observed with the La-high treatment. For soybean meal, the soluble fraction, rate of degradation and ED of DM decreased linearly, but the potentially degradable fraction increased linearly with increasing La supplementation. The ED of soybean meal DM was lower for La-medium (0.55) and La-high (0.51) than for control (0.58) due to lower rate of degradation. Similarly, rate of degradation and ED of crude protein (CP) also decreased linearly with increasing LA supplementation.

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Table 4 Effects of lanthanum chloride on urinary purine derivatives in steers Item

Treatmentsa Control

Urinary excretion (mmol/day) Allantoin 68.0 Uric acid 7.5 Total PD 75.5

S.E. La-low

La-medium

La-high

73.5 7.5 81.0

74.5 7.9 82.4

63.3 7.4 70.6

1.0 0.4 1.0

Contrast, P Linear

Quadratic

<0.01 <0.85 <0.01

<0.01 <0.27 <0.01

a Control (without LaCl ), La-low, La-medium and La-high with 450, 900 and 1800 mg/(steer day) LaCl , 3 3 respectively.

However, the soluble fraction was higher and the potential degradable fraction was lower for La-medium than for other treatments. 3.3. Urinary purine derivatives Urinary purine derivatives are shown in Table 4. Daily urinary excretion of uric acid was not affected by the treatments, but urinary excretion of allantoin and PD was affected quadratically by La supplementation, being highest for La-low (81.0) and La-medium (82.4), lowest for La-high (70.6) and intermediate for control (75.5). 3.4. Digestibility in the total tract Nutrient digestibilities in the total tract are shown in Table 5. Digestibilities of OM, CP and fibre in the total tract responded linearly and quadratically to La supplementation. The digestibilities of DM, OM and CP were increased with similar coefficients from 0.72, 0.75 to 0.78 for control, low to medium level of LA, respectively, and then decreased to 0.75 for high La supplementation. Similarly, digestibility of NDF or ADF was highest for Lamedium (0.67 or 0.65 for NDF and ADF, respectively), lowest for the control (0.59 or 0.56 for NDF and ADF, respectively), and intermediate for the La-low and La-high treatments (0.63 or 0.59 for NDF and ADF, respectively). Table 5 Effects of La supplementation on nutrient digestibility in the total tract of steers Item

Dry matter Organic matter Crude protein Ether extract Neutral detergent fibre Acid detergent fibre a

Treatmentsa Control

La-low

La-medium

La-high

0.724 0.721 0.721 0.693 0.594 0.563

0.753 0.750 0.762 0.733 0.626 0.593

0.784 0.779 0.773 0.799 0.672 0.650

0.748 0.745 0.754 0.698 0.631 0.579

S.E.

Contrast, P Linear

Quadratic

0.004 0.003 0.005 0.006 0.005 0.003

<0.01 <0.01 <0.01 <0.73 <0.01 <0.01

<0.01 <0.01 <0.01 <0.01 <0.01 <0.01

Control (without LaCl3 ), La-low, La-medium and La-high with 450, 900 and 1800 mg/(steer day) LaCl3 , respectively.

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4. Discussion 4.1. Ruminal fermentation Supplementation of La in the diet of steers altered rumen fermentation pattern from acetate to propionate production as shown by the dramatic reduction in ratio of acetate to propionate with increasing La dose (Table 2). The reduction in acetate to propionate ratio and increase in total VFA concentration was mainly due to an increase in propionate concentration. Lack of effect of La supplementation on ruminal acetate concentrations is consistent with high ruminal pH across the treatments. Ruminal pH in the present study was within the optimum range for cellulolytic bacterial activity (Russell and Wilson, 1996). This result is not consistent with in vitro findings of Wehr et al. (2005) who reported that addition of 150, 750 or 3750 ppm rare earth citrates did not influence ruminal fermentation using Rumen Simulation Technique. Similarly, using dual-flow continuous culture fermentors, Yang et al. (2007) observed no effect of a mixture of REE (adding daily 20–40 mg/L into fermentor) on ruminal total VFA concentration and the molar proportion of acetate or propionate. In contrast, the molar proportion of butyrate was increased (P<0.05) with 40 mg/L REE added. The dose of REE applied in the study of Wehr et al. (2005) was substantially higher than those used in the current study or in the study of Yang et al. (2007). Early studies showed that rare earths possess certain antibacterial properties (Muroma, 1958; Evans, 1990). Ruming et al. (2002) observed that Ce ions affected the growth of bacteria dose-dependently. Muroma (1958) reported that a concentration of 10−4 to 10−2 mol/L were necessary to inhibit bacterial growth, while at concentration of 10−5 mol/L, REE were able to support bacterial growth. It is suggested that REE could selectively stimulate or inhibit ruminal microbes at certain concentrations and, therefore, also change ruminal fermentation patterns. The quadratic response to La supplementation indicated that 1800 mg/(head day) had a negative effect on total VFA concentration and the proportion of propionate (Table 2). 4.2. In situ ruminal degradability and apparent digestibility in the total tract The linear increase of in situ ruminal ED of corn stover DM and NDF was consistent with linearly increased ruminal total VFA concentration (Table 2) with increasing La supplementation. Also, Yang et al. (2007) found a tendency (P<0.10) for increased digestibility of NDF from 0.67, 0.70 to 0.71 when REE (La and Ce) supplementation was increased from 0, 20 to 40 mg/L during continuous culture. Furthermore, the linear responses of ED of corn stover DM and NDF also supported the results of linearly increased nutrient digestibility in the total tract with La supplementation. It is suggested that oral uptake of La also improved nutrient digestibility in the intestine. In fact, magnitude of the increase in the total digestibilities of DM and NDF due to La supplementation was greater than that of the increase from the in situ ruminal ED. Furthermore, the intestinal CP digestibility should have been improved with La supplementation since increased total digestibility of dietary CP was not supported by an increase of in situ ruminal CP degradability of soybean meal (Table 3). Ming et al. (1995) reported that rare earths were capable of improving the digestibilities of total energy and CP in pigs, thus improving feed utilization. Hu et al. (1999) also observed improvement of apparent

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digestibilities of energy, protein and amino acids in pigs supplemented with REE. Several studies from the Chinese scientific community attributed performance enhancing effects of REE to improved digestibility and utilization of nutrients (Xie and Wang, 1998; Xu et al., 1998). In Europe, He et al. (2001) and Halle et al. (2003) reported higher BW gain along with reduced feed consumption for pigs supplemented with REE, thus better utilization of nutrients. Increases in energy balance, carbonate retention and digestibility of nutrients were observed in piglets supplemented with a low dose of REE (150 mg/kg DM of feed) versus a high dose (300 mg/kg DM of feed) (Prause et al., 2005). Shen et al. (1991) reported that daily gains of fattening beef cattle and feed efficiency during 45 day of feeding period were increased by 16 and 25%, respectively. He and Rambeck (2000) observed that BW gain and feed conversion ratio of the piglets were increased by 19% and 10%, respectively, with 150 mg La/kg DM of feed. He et al. (2003) also reported the benefits of oral supplementation of REE to improve growth rate and feed efficiency in rats. Improved animal growth rate and feed efficiency were likely resulted from increased nutrient digestibility in the digestive tract with REE supplementation. Considering the poor absorption of REE in the digestive tract (Hutcheson and Albaaj, 2005), several potential modes of action by REE in the intestine have been proposed. Prause et al. (2005) suggested that REE may influence the permeability of intestines, thereby, enhancing the absorption of nutrients, or may enhance the activities of certain enzymes involved in the digestive tract, thus enhance digestibility. In addition, Ou et al. (2000) proposed that REE could promote the secretion of digestive fluids in animal stomachs. Indeed, La was shown to increase gastric acid secretion dose-dependently in in vitro studies performed on isolated mice stomachs (Xu et al., 2004). The quadratic response to La supplementation with no further improvement of in situ ruminal degradation and total digestibility indicate that high dose of La supplementation (1800 mg/(steer day)) was not beneficial to improve rumen fermentation or intestinal digestion. This further confirmed the report of Muroma (1958) and suggested that La modulates the digestive microorganisms or enzymes in a dose-dependent manner. 4.3. N metabolism and PD excretion The increased urinary excretion of PD (Table 4) suggested that the microbial protein production in the rumen would be increased with increasing La supplementation. The improved in situ ruminal degradation of corn stover and the nutrient digestion in the total tract also supported an increase of ruminal microbial protein synthesis. Ruminally fermentable carbohydrate was the key dietary factor affecting microbial protein synthesis according to Krause et al. (2002). The linear reduction in ruminal ammonia N concentration with increasing La supplementation could have been due to an enhanced microbial growth which should have consumed more ammonia. Cellulolytic bacteria derive their N exclusively from ammonia N (Russell et al., 1992). One can suggest that La supplementation may improve ruminal fibrolytic bacterial activity as in situ ruminal ED of NDF was linearly improved (Table 3). In contrast, La supplementation in the present study likely reduced proteolytic activity in the rumen but increased protease activity post-ruminally (Table 5) as it showed a linear decrease of ruminal ED of soybean meal and a tendency for higher (P<0.13) proportion of branch chained VFA for the La-high than for the other treatments.

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5. Conclusion Increasing supplementation of beef diet with LaCl3 linearly increased ruminal VFA concentration and switched rumen fermentation pattern into more propionate production. In situ ruminal NDF degradation of corn stover was improved but CP degradability of soybean meal was decreased with increasing La supplementation. Urinary excretion of purine derivativs and nutrient digestibility in the total tract were also improved with La supplementation. Improvement of the total digestibilities of nutrients due to La supplementation was attributed to increase of both ruminal degradation and intestinal digestion. The results suggest that La modulates the digestive microorganisms or enzymes in a dose-dependent manner. The optimum La dose was about 900 mg/(steer day) and 1800 mg/(steer day) was not beneficial to improve the feed utilization under the present experimental conditions. The mode of action of rare earth elements in the digestive tract of cattle is unclear. Further study is warranted to focuss on the mechanism of rare earth elements in the digestive tract.

Acknowledgements This work was supported by a grant from National Agricultural Scientific Research Foundation of China (02EFN211401036). The authors thank the staff of Shanxi Agriculture University beef unit for care of the animals.

References AOAC, 1990. Official Methods of Analysis, 14th ed. Association of Official Analytical Chemists, Inc., Arlington, VA. Chen, X.B., Gomes, M.J., 1992. Estimation of microbial protein supply to sheep and cattle based on urinary excretion of purine derivatives—An overview of the technical details. Occasional Publication 1992, International Feed Resources Unit, Rowett Research Institute, Aberdeen, UK, p. 21. Evans, C.H., 1990. In: Frieden, E. (Ed.), Biochemistry of the Lanthanides. Plenum Press, New York, pp. 211– 283. Fiddler, G., Tanaka, T., Webster, I., 2003. Low systemic adsorption and excellent tolerability during administration of Lanthanumcarbonate (FosrenolTM ) for 5 days. In: Proceedings of the Ninth Asian Pacific Congress of Nephrology, Pattaya, Thailand, February 19–20. Halle, I., B¨ohme, H., Schnug, E., 2003. Investigations on rare earth elements as growth promoting additives in diets for broilers and growing-finishing pigs. In: Kampheus J., Wolf, P. (Eds), Proceedings of the Seventh Conference of the European Society of Veterinary and Comparative Nutrition (ESVCN), Hannover, Germany, 3–4 October, 2003, p. 101. He, M.L., Rambeck, W.A., 2000. Rare earth elements—a new generation of growth promoters for pigs? Arch. Anim. Nutr. 53, 323–334. He, M.L., Yang, Y., Cao, C.Z., Li, S.R., Hu, Q.L., Liu, Y.J., 1994. Effect of dietary rare earth additives on gaining ability in fattening cattle. Mod. Livestock Poultry Raising Ind. 9, 21–22 (in Chinese). He, M.L., Ranz, D., Rambeck, W.A., 2001. Study on the performance enhancing effect of rare earth elements in growing and fattening pigs. J. Anim. Physiol. Anim. Nutr. 85, 263–270. He, M.L., Wang, Y.Z., Xu, Z.R., 2003. Effect of dietary rare earth elements on growth performance and blood parameters of rats. J. Anim. Physiol. Anim. Nutri. 87, 229–235. Hu, Z., Wang, J., Yang, Y., Ma, Y., 1999. Effects of REE on the nutrient digestibility for growing pigs. Feed World 11, 29–31.

132

Q. Liu et al. / Animal Feed Science and Technology 142 (2008) 121–132

Hutcheson, A.J., Albaaj, F., 2005. Lanthanum carbonate for the treatment of hyperphosphataemia in renal failure and dialysis patients. Expert Opin. Pharmacother. 6, 319–328. International Atomic Energy Agency, 1997. Estimation of rumen microbial protein production from purine derivatives in urine. IAEA-TECDOC-945, IAEA, Vienna, pp. 22–24. Ji, Y., 1985. Toxicological study on safety evaluation of rare earth elements used in agriculture. In: Xu, G.X., Xiao, J.M. (Eds.), Proceedings of the International Conference on Rare Earth Development and Application, pp. 4–10. Krause, K.M., Combs, D.K., Beauchemin, K.A., 2002. Effects of forage particle size and grain fermentability in midlactation cows. I. Milk production and diet digestibility. J. Dairy Sci. 85, 1936–1946. McDonald, I., 1981. A revised model for the estimation of protein degradability in the rumen. J. Agric. Sci. (Camb.) 96, 251–252. Ming, Y., Xiu, Z., Ming, H., Yuan, L., 1995. Production and physiological effect of rare earth complex added to growing pig diet. In: Proceedings of the Third International Conference on Rare Earth Development and Applications, Baotou, China, August 21–25. Muroma, A., 1958. Studies on the bacterial action of salts of certain the rare earth metals. Ann. Med. Exp. Biol. Fenn. 36 (Suppl. 6), 1–54. Ou, X., Guo, Z., Wang, J., 2000. The effects of rare earth element additive in feed on piglets. Livestock Poultry Ind. 4, 21–22. Prause, B., Gebert, S., Wenk, C., Rambeck, W.A., Wanner, M., 2005. The impact of rare earth elements on energy, carbon and nitrogen balance of growing pigs. In: Proceedings of the 10th Symposium of Vitamins and Additives in the Nutrition of Man and Animal, Jena, Germany, September 28–29. Rambeck, W.A., He, M.L., Chang, J., Arnold, R., Henkelmann, R., Suss, A., 1999. Possible role of rare earth elements as growth promoters. In: Schubert, R., Flachowsky, G., Bttsch, R., Jahreis, G. (Eds.), Proceedings of the Seventh Symposium on Vitamins and Additives in the Nutrition of Man and Animal. Jena, Germany, pp. 311–317. Rambeck, W.A., He, M.L., Wehr, U., 2004. Proceedings of the British Society of Animal Science Pig and Poultry Meat Quality—Genetic and Non-genetic Factors, Krakow, Poland, October 14–15. Influence of the alternative growth promoter “rare earth elements” on meat quality in pigs.. Ruming, Z., Yi, L., Xu, Z.X., Ping, S., Qiu, S.S., 2002. Microcalorimetric study of the action of Ce(III) ions on the growth of E. coli. Biol. Trace Element Res. 86, 167–175. Russell, J.B., Wilson, D.B., 1996. Why are ruminal cellulolytic bacteria unable to digest cellulose at low pH? J. Dairy Sci. 79, 1503–1509. Russell, J.B., O’Connor, J.D., Fox, D.G., Van Soest, P.J., Sniffen, C.J., 1992. A net carbohydrate and protein system for evaluating cattle diets. I. Ruminal fermentation. J. Anim. Sci. 70, 3551–3561. SAS User’s Guide, 1996. Statistics, Version, 7th ed., SAS Inst., Inc., Cary, NC. Shen, Q., Zhang, J., Wang, C., 1991. Application of rare earth elements on animal production. Feed Ind. 12, 21–22 (in Chinese). Van Soest, P.J., Robertson, J.B., Lewis, B.A., 1991. Methods for dietary fiber, neutral detergent fiber and non-starch polysaccharides in relation to animal nutrition. J. Dairy Sci. 74, 3583–3597. Wang, M.Q., Xu, Z.R., 2003. Effect of supplemental lanthanum on the growth performance of pigs. Asian Austr. J. Anim. Sci. 16, 1360–1363. Wehr, U., Knebel, C., Ranbeck, W.A., Wanner, M., 2005. Effect of rare earth elements on ruminal fermentation as measured in vitro in rumen simulation technique (RUSTEC). In: Proceedings of the Society of Nutrition Physiology, vol. 14, p. 84 (abstract). Yang, W.Z., Laarman, A., He, M.L., 2007. Effects of supplementation of feedlot ration with rare earth elements on rumen fermentation and digestion in a continuous culture. In: Proceedings of Canadian Nutrition Congress, Wennipeg, MB, Canada, June 18–21. Xie, J., Wang, Z., 1998. The effect of organic rare earth compounds on production performance of chiken. In: Proceedings of the Second International Symposium on Trace Elements and Food Chain, Wuhan, China, November 12–15, p. 74. Xu, S., Harrison, J.H., Chalupa, W., 1998. The effect of ruminal bypass lusine and methionine on milk yield and composition of lactating cows. J. Dairy Sci. 81, 1062–1077. Xu, X., Xia, H., Rui, G., Hu, C., Yuan, F., 2004. Effect of lanthanum on secretion of gastric acid in stomach of isolated mice. J. Rare Earths 22, 427–430.