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Changes in ruminal fermentation, milk performance and milk fatty acid profile in dairy cows with subacute ruminal acidosis and its regulation with pelleted beet pulp a
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Yongqing Guo , Libin Wang , Yang Zou , Xiaofeng Xu , Shengli Li & Zhijun Cao
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State Key Laboratory of Animal Nutrition, College of Animal Science & Technology, China Agricultural University, Beijing, China Published online: 05 Nov 2013.
To cite this article: Yongqing Guo, Libin Wang, Yang Zou, Xiaofeng Xu, Shengli Li & Zhijun Cao (2013) Changes in ruminal fermentation, milk performance and milk fatty acid profile in dairy cows with subacute ruminal acidosis and its regulation with pelleted beet pulp, Archives of Animal Nutrition, 67:6, 433-447, DOI: 10.1080/1745039X.2013.842038 To link to this article: http://dx.doi.org/10.1080/1745039X.2013.842038
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Archives of Animal Nutrition, 2013 Vol. 67, No. 6, 433–447, http://dx.doi.org/10.1080/1745039X.2013.842038
Changes in ruminal fermentation, milk performance and milk fatty acid profile in dairy cows with subacute ruminal acidosis and its regulation with pelleted beet pulp
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Yongqing Guo†, Libin Wang†, Yang Zou, Xiaofeng Xu, Shengli Li* and Zhijun Cao* State Key Laboratory of Animal Nutrition, College of Animal Science & Technology, China Agricultural University, Beijing, China (Received 6 April 2013; accepted 2 September 2013) The aims of the experiment were to investigate the variation in ruminal fermentation, milk performance and milk fatty acid profile triggered by induced subacute ruminal acidosis (SARA); and to evaluate the ability of beet pulp (BP) as a replacement for ground maize in order to alleviate SARA. Eight Holstein-Friesian cows were fed four diets (total mixed rations) during four successive periods (each of 17 d): (1) without wheat (W0); (2) with 10% finely ground wheat (FGW) (W10); (3) with 20% FGW (W20); (4) with 20% FGW and 10% pelleted BP (BP10). Inducing SARA by diet W20 decreased the daily mean ruminal pH (6.37 vs. 5.94) and the minimum ruminal pH (5.99 vs. 5.41) from baseline to challenge period. Ruminal concentrations of total volatile fatty acid, propionate, butyrate, valerate and isovalerate increased with the W20 compared with the W0 and W10 treatments. The substitution of BP for maize increased the minimum ruminal pH and molar percentage of acetate and decreased the molar percentage of butyrate. The diets had no effect on dry matter intake (DMI) and milk yield, but the milk fat percentage and yield as well as the amount of fat-corrected milk was reduced in the W20 and BP10 treatments. The cows fed the W20 diet had greater milk concentrations of C11:0, C13:0, C15:0, C14:1, C16:1, C17:1, C18:2n6c, C20:3n6, total polyunsaturated fatty acids (FA) and total odd-chain FA, and lower concentrations of C18:0 and total saturated FA compared with the cows fed the W0 diet. Therefore, it can be concluded that changes in ruminal fermentation, milk fat concentration and fatty acid profile are highly related to SARA induced by feeding high FGW diets, and that the substitution of BP for maize could reduce the risk of SARA in dairy cows. Keywords: acidosis; beet pulp; dairy cows; fatty acids; milk composition; rumen fermentation
1. Introduction Subacute ruminal acidosis (SARA), defined as periods of moderately depressed ruminal pH, is one of the most common chronic digestive disorders, especially in well-managed dairy herds. High-producing dairy cows are at greater risk of SARA because their diets often contain a high concentrate-to-forage ratio or a high percentage of easily fermentable carbohydrates to meet the high demand for energy (Stone 2004). Mid-lactation dairy cows are also at risk of SARA, due to their high dry matter intake (DMI), and they are particularly sensitive to sudden changes in feed and in feed composition and delivery (Nordlund et al. 1995). SARA can result in decreased DMI, milk production, and milk fat content, and cause diarrhoea and lameness, as well as an increase in mortality (Plaizier et al. 2008). *Corresponding authors. Emails:
[email protected] (S. Li);
[email protected] (Z. Cao) †Equal contributors. © 2013 Taylor & Francis
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Rumen fluid pH is the only reliable tool to diagnose SARA (Keunen et al. 2002). At the herd level, the sampling methods (obtained via ruminocentesis or a stomach tube) were either an invasive technique or susceptible to salivary contamination (Gianesella et al. 2010). Accordingly, there is continued interest in milk compounds (e.g. milk fat content, milk oddand branched-chain fatty acids [FA]) as potential diagnostic tools of rumen fermentation patterns and function (Vlaeminck et al. 2006; Fievez et al. 2011). Various dietary strategies have been studied for regulating ruminal pH such as sodium bicarbonate and monensin (Mutsvangwa et al. 2002; Paton et al. 2006). However, neither of these methods have consistently maintained higher rumen pH values. Although direct-fed microbials or acarbose supplementation has been reported to increase rumen pH values more consistently (McLaughlin et al. 2009; Thrune et al. 2009), such supplementation is uneconomic and impractical for ordinary dairy farms. Beet pulp (BP) contains approximately 40% of neutral detergent fibre (NDF) and is unique in its high content of soluble fibre, especially pectic substances (Voelker and Allen 2003). The fermentation of pectins in the rumen has been shown to produce less lactate and propionate than starch fermentation (Marounek et al. 1985). Therefore, the substitution of BP for maize grain should reduce negative effects of increased starch fermentation and prevent unfavourable declines in ruminal pH (Silveira et al. 2007). The objective of this study was to test the hypothesis that SARA induced by feeding diets high in finely ground wheat (FGW) is related to alterations in the rumen fermentation pattern, milk performance and milk fatty acid profile in mid-lactation dairy cows. Another goal of this study was to evaluate the suitability of pelleted BP as a substitute for ground maize to alleviate SARA. 2. Materials and methods 2.1. Experimental design and animal management Animal care procedures were approved and conducted under the established standard of the College of Animal Science & Technology, China Agricultural University. Eight multiparous Holstein-Friesian (HF) cows (568 ± 34.7 kg BW; 164 ± 15 d in milk; mean ± SD), four of which were fitted with ruminal cannulas (10 i.d; Bar Diamond, Parma, ID), were fed a series of diets (sTable 1) during four successive periods: an initial baseline period with starch provided as ground maize to represent a slowly fermented starch diet without wheat (W0 treatment); a second period with 10% FGW (geometric mean particle sizes: 600 μm) to represent a moderately high fermented starch diet (W10 treatment); a third period with 20% FGW to represent a diet containing a large amount of rapidly fermented starch (W20 treatment); and a final period in which the W20 diet was amended by replacing 10% of the ground maize content with 10% dried, pelleted BP (BP10 treatment). The specific diets were fed sequentially to all eight cows over four 17-d periods (treatment adaptation 12 d and data collection 5 d) because previously Krause and Oetzel (2005) and Enjalbert et al. (2008) observed that SARA was not easily reversible, making other experimental designs (e.g. a Latin square) problematic for this type of study. The four diets were formulated to meet or exceed the National Research Council (2001) guidelines for 600 kg multiparous Holstein dairy cows producing daily 27 kg milk with 4.0% fat. The diets were fed as total mixed ration (TMR) (CAU-mixer wagon model JZC-200, Beijing, China), and the forage component of the diets was a mixture of maize silage, chopped alfalfa hay and Chinese wild rye. The moisture content of the maize silage was determined weekly and used to adjust the rations. During each data collection period, the particle size distribution of the TMR (Table 2) was determined using a Penn State Particle Separator (PSPS) as described by Lammers et al. (1996).
Archives of Animal Nutrition Table 1.
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Ingredients and chemical composition of experimental diets. Dietary treatments
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W0* Ingredients [% of DM] Maize silage 33.0 Alfalfa hay 15.0 Chinese wild rye 12.0 Maize grain 18.0 Wheat grain – Soybean meal 12.6 Cottonseed meal 3.5 Corn distillers grains 1.0 Wheat bran 0.2 Pelleted beet pulp – Whole cottonseed 2.0 0.50 Mineral-vitamin premix# Dicalcium phosphate 0.60 Limestone 0.50 Sodium bicarbonate 0.50 Magnesium oxide 0.15 Salt 0.50 Chemical composition [% of DM] Crude protein 15.8 31.9 NFC§ 41.2 NDF♦ ADF‡ 22.6 Forage NDF 34.4 Starch 28.5 Ether extract 3.4 Ash 7.7 Calcium 0.77 Total phosphorus 0.42 Forage : concentrate ratio 60:40 NFC/NDF 0.77 6.3 NEL¶ [MJ/kg]
W10*
W20*
BP10†
27.5 12.5 10.0 18.0 10.0 10.6 3.5 3.0 – – 2.0 0.50 0.58 0.69 0.50 0.15 0.50
22.0 10.0 8.0 18.0 20.0 9.6 3.5 3.0 0.9 – 2.0 0.50 0.47 0.92 0.50 0.15 0.50
22.0 10.0 8.0 8.0 20.0 9.6 3.5 3.0 1.0 10.0 2.0 0.50 0.54 0.70 0.50 0.15 0.50
16.2 36.0 36.2 19.9 28.6 33.0 3.4 8.2 0.77 0.42 50:50 0.99 6.5
16.5 42.2 31.2 16.1 22.9 36.6 3.3 6.8 0.77 0.42 40:60 1.35 6.7
16.4 34.8 38.0 19.8 22.9 31.0 3.0 7.8 0.77 0.42 40:60 0.92 6.5
Notes: *W0, W10 and W20, TMR containing 0, 10 and 20% finely ground wheat, respectively; †BP10, TMR containing 20% finely ground wheat plus 10% pelleted beet pulp. #Contained per kg of premix (on DM basis): 1,000,000 IU vitamin A; 65,000 IU vitamin D; 3340 mg vitamin E; 2000 mg Fe; 2550 mg Mn; 5500 mg Zn; 1750 mg Cu; 70mg I; 40 mg Co; 75 mg Se; §NFC, Non-fibre carbohydrates calculated as 100 – (crude protein + ash + NDF + ether extract); ♦NDF, Neutral detergent fibre; ‡ADF, Acid detergent fibre; ¶NEL, Net energy lactation, calculated using NEL values of feed stuffs from National Research Council (2001).
Table 2. Particle size distribution of the experimental diets determined using the Penn State Particle Size Separator (PSPS) [% retained, as-fed basis]. Dietary treatments Particle size
W0*
W10*
W20*
BP10†
>19 mm 8–19 mm 1.18–8 mm 0.05 to ≤ 0.10. The p-values indicated in Tables 3–5 refer to the overall diet effects. The correlation coefficient (R) between the selected rumen fermentation parameters and the milk FA profiles was calculated using SPSS Statistics software 18 (IBM). 3. Results 3.1. Ruminal pH The diets had a significant effect on the ruminal pH observed at each step change from the W0 treatment to the BP10 treatment of the dairy cows. The mean ruminal pH (over the 2-d period) was 6.37 ± 0.15 (mean ± SE) during the baseline period (W0 treatment) and decreased
438 Table 3. cows#.
Y. Guo et al. Effect of dietary treatments on rumen fermentation characteristics in mid-lactation dairy Dietary treatments
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W0*
W10*
W20*
p-Value BP10†
SEM§
6.01b 5.94b 6.05b Mean pH 6.37a 5.63b 5.41b 5.63b Minimum pH 5.99a Lactate [mmol/l] 0.26 0.17 0.29 0.18 VFA¶ concentration [mmol/l] Total 101.1c 114.4b 127.9a 124.0ab b ab ab 80.17 78.61 84.85a Acetate (C2) 72.53 19.58b 29.04a 25.28a Propionate (C3) 16.36b c bc a 11.19 15.08 12.39ab Butyrate 8.93 Isobutyrate 0.92a 0.87ab 0.68b 0.92a c bc a 1.36 2.34 1.68b Valerate 1.06 1.28b 2.13a 1.39b Isovalerate 1.33b a a b 4.16 3.13 3.41b C2/C3 4.56 VFA [%]‡ Acetate 71.93a 70.09a 62.44c 66.64b 17.08b 22.10a 20.28a Propionate 16.00b b b a Butyrate 8.82 9.76 11.50 9.85b
Treatment (Trt) Time Trt × Time
0.05 0.07 0.02