Effect of Chromium Propionate Substituting 25% Rumen-protected Choline on Production Performance and Blood Indicators of Perinatal Dairy Cows

Wang Lei, Tang Ke-nan, Zheng Fei, Cao Sheng-xu, Liang Zi-chao, and Liu Da-sen,

1 College of Animal Sciences and Technology, Northeast Agricultural University, Harbin 150030, China

2 College of Science, Northeast Agricultural University, Harbin 150030, China

Abstract: The object of this study was to investigate the effects of chromium propionate replacing 25% rumen-protected choline(RPC) on production performance and blood indicators of perinatal dairy cows. According to the principle of ensuring that chromium propionate and RPC were fed 14 days prepartum, 27 healthy Holstein cows (age, parity, lactation volume, body condition and expectancy were similar) were randomly divided into three groups (GroupsⅠ, Ⅱ and Ⅲ), with nine cows in each group. Cows in GroupⅠwere fed basal diets; cows in GroupⅡwere fed the same basal diets with 10 g · d-1 RPC per cow; and cows in Group Ⅲwere fed the same basal diets, but 7.5 g RPC and 2.5 g chromium propionate (4 mg chromium) per cow. The results showed that dry matter intake (DMI) of prepartum in GroupsⅡand Ⅲ was significantly increased (P＜0.05), compared with GroupⅠ; however, there was no significant difference between Groups Ⅱ and Ⅲ (P＞0.05). The milk fat content in Group Ⅲ was significantly higher than that in Group Ⅰ on the 7th day of postpartum (P＜0.05). The urea nitrogen content in Groups Ⅱ and Ⅲ significantly lower than that in GroupⅠon the 21st day of postpartum (P＜0.05), but there were no significant difference between Groups Ⅱ and Ⅲ (P＞0.05). The somatic cell counts in Group Ⅲ were significantly lower than those in GroupsⅠand Ⅱ on the 14th and 21st days of postpartum(P＜0.05). The contents of the total cholesterol in Group Ⅲ decreased significantly compared to Group Ⅱ on the 7th day of prepartum,on the day of calving and the 7th day of postpartum (P＜0.05). The concentration of high-density lipoprotein (HDL) in Group Ⅲ was significantly higher than that in Group Ⅱ on the 7th day of prepartum, on the day of calving and the 7th day of postpartum (P＜0.05).On the 7th day of postpartum the concentration of insulin in Group Ⅲ was obviously higher than that in Group Ⅱ (P＜0.05). In summary, replacing 25% of rumen-protected choline with chromium propionate reduced production costs and improved dairy farming benefits.

Key words: chromium propionate, dairy cow, perinatal, rumen-protected choline

Introduction

The perinatal period is defined as from 15 days prepartum to 15 days postpartum, during this period,daily nutrient intake is insufficient to meet demands for milk yield and energy balance is negative, and dairy cows mobilize large amounts of fatty acids from adipose tissue to meet energy requirements(Piepenbrink and Overton, 2003). As a consequence of body fat mobilization, the concentration of nonesterified fatty acids (NEFA) increases in plasma,which leads to hepatic lipidosis. In liver, the NEFA also is re-esterified NEFA triglycerides (TG), and furthermore accumulated TG may result in fatty liver.It seriously affects the performance of dairy cows and reduces the benefits of dairy farming. At present,studies have shown that rumen-protected choline(RPC) significantly affected the negative balance of energy in dairy cows, during the perinatal period,reducing the incidence rate and improving yield performance of dairy cows. Choline plays an essential role in very low-density lipoprotein (VLDL) synthesis and thereby contributes to fat export from the liver(Eleket al., 2008). Several studies reported that the supplementation of RPC decreases concentration of serum non-esterified fatty acids (Guretzkyet al.,2006) and triglycerides contents (Zomet al., 2011),and improves lipid metabolism. Simultaneously, RPC supplementation increases milk yield in the early lactation of dairy cows (Zenobiet al., 2017) and dry matter intake (Chunget al., 2005). Wu (2012) found that RPC supplementation increases the content of milk fat and the total solids in dairy cow diets, during the lactation period.

However, the high price of RPC has affected the breeding efficiency of dairy cows. From the study of chromium propionate on the regulation of fat metabolism in perinatal dairy cows, it is found that Cr3+has similar physiological effects to choline. It regulates fat metabolism by synthesizing lipoprotein,and improves the body fat situation and the yield performance of dairy cows. Chromium is an essential trace element for animals as active component of GTF(glucose tolerance factor). Chromium enhances the action of insulin, decreases concentration of plasma NEFA and TG, but improves glucose tolerance,which may result in improvement of performance and yield during the perinatal dairy cows (Sinclair,2010). Some studies report that the supplementation of chromium propionate (8 mg · d-1chromium) in diets of lactating cattle increases milk yield (Rockwell and Allen, 2016) and dry matter intake (DMI) (Vargas-Rodriguezet al., 2014). Duet al. (2013) reported that supplementation of chromium propionate in dairy cow diets significantly reduces the somatic cell counts in milk and reduces the incidence of mastitis.

Both RPC and chromium propionate improve the synthesis of lipoproteins to regulate fat metabolism,in which RPC promotes the formation of low density lipoprotein, and chromium propionate improves the yield of high density lipoprotein by enhancing the action of insulin. However, chromium propionate also regulates lipid metabolism by improving insulin sensitivity and glucose tolerance, while RPC is metabolizing and transporting fat in the liver. Moreover, RPC improves the ability of the liver to utilize fatty acids and reduces fat accumulation. In addition, studies showed that RPC promotes insulin secretion (Leivaet al., 2015). Meanwhile,choline is essential for the animal to maintain normal nervous system function. Therefore, the replacement of RPC with the chromium propionate may not be consistent with the results of partial replacement.

Materials and Methods

Animal care

Northeast Agricultural University Institutional Animal Care and Use Committee approved all the procedures involving animals.

Experiment animals, materials and design

Chromium propionate (chromium content of 0.04%)was purchased from Taiyuan Xinjida Chemical Co.,Ltd. The price was 50 Yuan · kg-1. Rumen-protected choline (effective choline was 25%) was purchased from Zhengzhou City Kelikang Commercial Co., Ltd.The price was 120 Yuan · kg-1.

The trial was conducted in October 2017 on the Jin'ao Farm (Heilongjiang, China). According to the principle of ensuring that chromium propionate and RPC were fed 14 days prepartum, 27 healthy Holstein cows (age, parity, lactation volume, body condition and expectancy were similar) were randomly divided into three groups (GroupsⅠ,Ⅱ and Ⅲ),with nine cows in each group. The cows in GroupⅠwere provided basal diets for 14 days prepartum and postpartum diet for 21 days; the cows in GroupⅡ were fed the same basal diets with 10 g · d-1RPC per cow;but cows in Group Ⅲ were fed the same basal diets supplemented with 7.5 g RPC and 2.5 g chromium propionate (4 mg chromium). The forage to concentrate ratios and nutrient values of the diets are shown in Table 1. The cows were fed three times every day and free access to water, during the experiment,and milked three times per day at 5 a.m., 1 p.m. and 9 p.m.

Table 1 Diets and nutritional components of prepartum and postpartum (%, DM)

Collection of samples

Milk yield and milk composition were measured on the 7th, 14th and 21st days of postpartum. The milk samples were collected at the ratio of 4 : 3 : 3 in the morning, the middle and the evening to add preservatives. A total of about 50 mL of milk samples were collected and mixed evenly, and stored at 4℃. The 10 mL blood was collected in vacuum anticoagulant centrifuge tube on the 7th day of prepartum, the day of calving, and the 7th, 14th and 21st days of postpartum in the fasting tail vein. Within 1 h after collection, blood samples were centrifuged at 3 000 r · min-1for 15 min, and subsequently, 1.5 mL of serum was transferred into a vial and stored at -20℃until further analyses.

Determination and method of index

The milk composition was determined by FossMaticTMFC and MilkoScanTMFT+ instruments, including milk fat, milk protein, lactose, the total solids, urea nitrogen content and somatic cell count (SCC). The concentrations of serum glucose, TG and the total cholesterol were determined using enzyme method;and concentration of low-density lipoprotein (LDL)and high-density lipoprotein (HDL) were measured by the direct method. The concentrations of NEFA andβ-hydroxybutyric acid (BHBA) were analyzed by enzyme-linked immunosorbent assay (ELISA)using kits (Bovine FFA ELISA kit and Bovineβ-OHB ELISA kit; Shanghai Jinma Experimental Equipment Co., Ltd.). Concentrations of insulin and glucagon were monitored by radioimmunoassay using kits (125I Insulin Radioimmunoassay kit and125I Glucagon Radioimmunoassay kit; Beijing North Biotechnology Research Institute Co., Ltd.).

Statistical analysis

SAS 9.2 (SAS Institute Inc, 2000) was used for data analysis. Multiple comparison for treatments of chromium propionate was done by the SNK method.For trial of replacing 25% of RPC, ANOVA single factor model was used to analyze the variance of the replacing effect on the yield performance and blood parameters of perinatal dairy cows. Data were expressed as the mean±standard deviation. Treatment effects were considered significant atP＜0.05 and trends were considered at 0.05≤P＜0.10.

Results

Dry matter intake (DMI) and milk yield

DMI of prepartum in GroupsⅡ and Ⅲ was significantly increased (P＜0.05), compared with GroupⅠ; however,there was no significant difference between GroupsⅡand Ⅲ (P＞0.05). Compared with GroupⅠ, DMI of postpartum in GroupsⅡand Ⅲ did not significantly affect (P＞0.05). The milk yield and 4% fat correct milk of GroupsⅡand Ⅲ did not significantly influence(P＞0.05), compared with GroupⅠ(Tables 2 and 3).

Table 2 Effect of RPC and replacing 25% RPC with chromium propionate on milk yield and 4% fat correct milk in dairy cows

Table 3 Effect of RPC and replacing 25% RPC with chromium propionate on DMI in dairy cows

Milk composition

The milk fat content in Group Ⅲ was significantly higher than that in GroupⅠ(P＜0.05) on the 7th day of postpartum. The urea nitrogen content in GroupsⅡand Ⅲ both was significantly lower than that in GroupⅠon the 21st day of postpartum (P＜0.05).Compared with GroupⅠ, the somatic cell counts in Group Ⅲ were significantly decreased on the 14th and 21th days of postpartum, and the somatic cell counts of Group Ⅲ were also significantly lower than those in GroupⅡ(P＜0.05). However, there were no significant difference in milk protein, lactose,the total solid contents among GroupsⅠ, Ⅱand Ⅲ(P＞0.05) (Table 4).

Blood indicators

From the 7th day of prepartum to the 21st day of postpartum, compared with GroupⅡ, the blood glucose level in Group Ⅲ increased, and the triglyceride content in Group Ⅲ decreased, but the difference was not significant between the two groups(GroupsⅡand Ⅲ) (P＞0.05). The contents of the total cholesterol in Group Ⅲ decreased significantly compared to Group Ⅱ on the 7th day of prepartum,on the day of calving and the 7th day of postpartum(P＜0.05).

The concentration of HDL in Group Ⅲ was significantly higher than that in Group Ⅱ on the 7th day of prepartum, on the day of calving and the 7th day of postpartum (P＜0.05), while only on the 14th day of postpartum, the concentration of LDL had a tendency decrease compared with GroupⅡ(P=0.06). Compared with GroupⅡ, the concentrations of NEFA and BHBA in Group Ⅲ decreased, but the difference was insignificant between GroupsⅡand Ⅲ (P＞0.05). On the 7th day of postpartum, the concentration of insulin in Group Ⅲ was obviously higher than that in GroupⅡ(P＜0.05). Compared with GroupⅡ, the concentration of glucagon in Group Ⅲ showed a tendency decrease on the 21st day of postpartum (P=0.08) (Table 5).

Table 4 Effect of RPC and replacing 25% RPC with chromium propionate on milk composition in dairy cows

s airy cow atal d erin of p lood icators in b e ind n som ate o pion ro m p iu ith chrom C w RP lacing 25%ffect of rep ble 5 E Ta e artum P-valu ostp of p M 1st day SE The 2 Estimate e artum ostp P-valu of p M e 14th day SE Th Estimate m ay of postpartu -value M P SE e 7th d Th Estimate alue ay of calving -v M P SE On the d Estimate repartum -value f p M1 P day o SE The 7th Estimate p Grou Item 0.53 0.84 0.09 0.22±0.40 3.45±0.35 3.56±0.82 4.90±1.04 4.80 0.55 0.16 0.12 0.39 9.6 012 3.33±0.3 3.48±0.2 4.63±2 3.52±0.5 0.291＜0.0 0.07 0.21 3.37±0.33 3.51±0.214a.51b 3.95±0.3 2.44±0 0.53＜0.01 0.08 0.31.41±0.32 3.53±0 3.64 4.26±0.73a±0.68b 2.07 0.521＜0.0 0.09 0.26±0.361a 3.41±0.47 3.53 4.33±0.7 2.53±0.46bⅡⅢⅡⅢGlucose mol · L-1)HO TC mo l · L-1)(m (m 0.45.01＜0 0.01 0.34±0.026a.30b 0.16±0.03 0.15 2.54±1 4.38±0.8 0.39 0.11 0.01 0.28 3.0 267 0.16±0.0 0.15±0.4 4.31±1.5 3.43±0 0.151.0＜0 0.01 0.22 0.17±0.02 0.15±0.034b.54a 3.09±0.3 4.73±0 0.74＜0.01 0.01 0.22.03±0.02 0.15±0 0.14 3.14±0.54b 4.69±0.52a 0.461＜0.0 0.01 0.22±0.020a 0.16±0.02 0.15 3.43±0.76b 4.87±0.3ⅡⅢⅡⅢTG l · L-1)mo Ll · L-1)(m HD mo(m 0.58 0.10±0.38 1.63±0.44 1.52 0.06 0.21 2.6 1 2.36±0 1.85±0.4 0.43 0.10 1.91±0.37 1.77±0.41 0.42 0.12.54±0.48 2.39±0 2.20 0.74 0.11±0.48 2.31±0.51 2.23Ⅱ ⅢL LD mol · L-1)(m 0.42 12.53 4.52±7 1.32 1.17±2 391.56 39 0.83 4 13.1 382.16±61.61 387.92±52.85 0.93 11.53±58.39 9.61±40.91 367.56 36 0.88 5.6 13 8.44 374.69±7 1.01 378.92±3 0.98 8.7 16 3.55±8 1.57 7.10±6 396.42 39Ⅱ ⅢFA NE l · L-1)mo(μ 0.75 0.31 0.77 0.24 3.60 24.49±3.06 25.00±0.99 18.52±1.02 19.01±0.39 0.28 0.58 0.28 2.33 8±2.58 0.95 1.37 24.17±23.14±18.16±18.7 0.485.0＜0 0.52 0.26 2.54b a 23.61±1.88 22.85±0.73 3±1.17.72±17.4 18 0.23 0.07 0.60 0.31 1.72.47±3.12 0.66 0±1.60 1±24.00±23.9 15.0 17 0.62 0.18 0.37 0.34 1.64 25.07±1.57 24.68±0.71 17.74±1.86 18.68±ⅡⅢⅡⅢBA lin BH mol · L-1)· mL-1)(μInsu IU(μ 0.08 3.52 2.19±1 5.49 7.26±1 304.96 29 0.36 5.00 7.48±2 311.03 301.60±12.33 0.19 5.23±27.67 8.94±12.98 314.86 30 0.50 3.70 2.19 310.24±1 8.99 301.53±1 0.46 3.84 6.23±1 6.78 2.16 28 6.35±1 27Ⅱ Ⅲon Glucag(pg · mL-1)

Discussion

Milk yield and DMI

DMI of perinatal dairy cows during the early lactation was reduced, the energy requirements of the dairy cows did not meet, which resulted in reduced yield performance of dairy cows. Some studies reported that supplementation of RPC in diets increased DMI of dairy cows (Chunget al., 2005). RPC increased milk yield and DMI of cows in the transition period (Zhenget al., 2012). In this experiment, on the 7th, 14th and 21st days of postpartum, the milk yield in GroupⅡwas higher than that in GroupⅠ, which might be associated with the addition of RPC in the diet, thus increased the efficiency of fat supply during the peak lactation period of the dairy cows, and improved the negative balance of the body energy, thereby increasing the milk yields of the dairy cows. Meanwhile, some studies demonstrated that 8 mg · d-1chromium (Vargas-Rodriguezet al., 2014) or 10 mg · d-1chromium(McNamara and Valdez, 2005) increased DMI. In addition, Eleket al. (2008) found that adding RPC in diets increased milk yield in dairy cows, moreover,chromium propionate also increased milk yield in lactating dairy cows (McNamara and Valdez, 2005). In the present study, the increase of milk yield in GroupⅢcompared with GroupⅡmight be caused by the enhancement of gluconeogenesis in the livers of dairy cows.

Milk composition

Milk composition is an important indicator of milk quality. Limaet al. (2007) showed that the addition of RPC to dairy cow diets significantly increased milk fat. In this experiment, the milk fat content in GroupⅡwas higher than that in GroupⅠ, which might involve in the transport of fatty acids in the liver, during the process of body fat mobilization with choline as a component of lipoproteins, promote the transport of lipids from the liver and adipose tissue to the mammary gland, and improve the ability of the breast to synthesize milk fat using fatty acids, thereby improving the milk fat contents.

Due to the lack of glucose-6-phosphatase in the mammary gland tissue of cows, it is impossible to synthesize glucose with other raw sugar precursors,thus most of the lactose come from the supply of plasma glucose, because the blood sugar level is related to the lactose content. In this experiment,the insignificant difference of blood glucose levels between the two groups (GroupsⅡand Ⅲ) might result from the insignificant lactose content in the milk.The urea nitrogen content in Group Ⅲ was higher than that in GroupⅡon the 21st day of postpartum,which was consistent with the results of Yasuiet al(2014). The results of Paapeet al. (1973) showed that the increase of somatic cell counts in milk decreased milk yield. Collieret al. (1982) showed that the higher somatic cell counts in milk increased the incidence of subclinical mastitis. However, in this experiment, the somatic cell counts in Group Ⅲmilk were significantly lower than those in GroupsⅠand Ⅱ on the 14th and 21st days of postpartum, which was consistent with Wang's experimental results(2013). This result indicated that chromium propionate enhanced the resistance of dairy cows and reduced susceptibility to pathogens. It was speculated that chromium propionate might enhance the immunity of dairy cows and reduce the incidence of mastitis.Duet al. (2013) found that the addition of chromium propionate had little effect on the milk composition,and the differences in milk fat, milk protein and lactose contents were not significant. The reason for the inconsistency might be the cow's health, chromium propionate addition, the period of lactation and the stress of the environment.

Blood indicators

Blood glucose level is the body's response to the dynamic balance of glucose absorption, transport and metabolism, and the concentration of blood glucose in circulating blood reflects the level of energy metabolism in dairy cows. And the regulation of energy metabolism in ruminants is mainly controlled by insulin and glucagon. Insulin is the main hormone to promote anabolism and regulate the stable blood glucose. Insulin may also reduce the transfer of fatty acids from the lipid library to other tissues, and high concentrations of insulin in the blood reduce the concentration of non-esterified fatty acids (Christensenet al., 1997). The supplementation of RPC to diets improved the concentration of blood glucose and stabilized blood glucose levels (Davidsonet al., 2008).And some studies showed that RPC increased serum insulin concentration in cows (Leivaet al., 2015).Supplementation of chromium enhanced gluconeogenesis or glycogenolysis (Subiyatnoet al., 1996),and improved glucose metabolism in ruminants. Some studies reported that supplementation of chromium propionate (10 mg · d-1chromium) in cattle increased serum glucose (Sumneret al., 2007) and insulin concentrations (Leivaet al., 2015). Insulin appeared to act in concert with elevated blood glucose to inhibit glucagon secretion from the pancreas (Greenbaumet al., 1991). Choung and Chamberlain (1995) found that the infusion of propionate increased serum insulin concentration. However, cows fed chromium propionate had lower plasma glucose concentration within the 1st day of postpartum (Yasuiet al., 2014).These differences might be due to physiological status,degree of stress and type of nutritional ingredient. In this experiment, concentrations of serum glucose and insulin in cows were not significant. Co-operation of positive effect of propionic acid and negative effect of chromium attributed to it. Propionic acid decomposed from chromium propionate in rumen enhanced serum glucose by increasing gluconeogenesis of the liver and increasing serum insulin by high propionic acid level, but chromium in serum reduced serum glucose and glucagon concentrations by increasing action of insulin, which promoted the glycogen yield, glucose decomposition and glucose conversion into fat and inhibited the decomposition of glycogen and the gluconeogenesis.

Concentrations ofβ-hydroxybutyric acid (BHBA)and non-esterified fatty acids (NEFA) in serum were used as indicators for the energy status of dairy cows and subclinical ketosis (Zomet al., 2011). RPC reduced NEFA and BHBA in the blood of dairy cows(Guretzkyet al., 2006). And some studies reported that chromium propionate supplementing to cattle decreased serum NEFA concentration (Yasuiet al.,2014). This study showed that the contents of NEFA and BHBA in the serum of the two groups (GroupsⅡand Ⅲ) trended to decrease from the 7th day of prepartum to the 7th day of postpartum, and increase from the 7th day to the 21st day of postpartum. It suggested that the energy supply met basic the needs of dairy cows and the demand of lipid metabolism had been reduced.

Choline played a major role in the hepatic fat metabolism of dairy cows and might promote the transport and metabolism of lipids accumulated in the liver as lipoproteins, and was an essential component for the synthesis of phosphatidylcholine, being the most important phospholipid component of VLDL(Vance, 2002). It increased the rate of VLDL synthesis and secretion of esterified lipid products from liver(Piepenbrink and Overton, 2003). Liet al. (2014)reported that the supplementation of RPC to diets of perinatal dairy cows increased significantly LDL level in serum. In addition, chromium supplementation enhanced the activity of lipoprotein enzyme and lecithin cholesterol acyl transferase. However, these two enzymes were mainly involved in the synthesis of HDL and increasd the concentration of HDL in the blood. In the present experiment, the concentration of HDL in Group Ⅲ was significantly higher than that in Group Ⅱ and LDL was lower. The result resulted from chromium propionate replacing RPC reduced NEFA concentration in blood and resulted in a decrease in the content of VLDL in the liver, which further decreased the concentration of LDL. Some studies reported that feeding RPC decreased the concentration of TG (Piepenbrink and Overton, 2003; Zomet al.,2011). Subiyatnoet al. (1996) found that perinatal dairy cows fed with chromium (0.5 mg · kg-1diet) had reduced concentration of TG. Rahmaniet al. (2014)reported that feeding RPC affected cholesterol in the early lactation dairy cows. Zenobiet al. (2018) found that diets supplemented with RPC in cows reduced the total cholesterol and TG concentrations. It was proved that Cr3+was the main active ingredient of GTF and Cr3+enhanced the action of insulin. GTF could convert blood glucose into tissues through the effect of insulin and reduced the concentrations of serum cholesterol and TG. The result was generally supported by the role of Cr3+, and it indicated that less cholesterol and triglyceride concentrations in the blood might potentially decrease the risk for metabolic disorders in the perinatal dairy cows.

From the economic point of the view, when chromium propionate replaced 25% RPC, it saved about 6 400 Yuan a year, if 100 perinatal dairy cows were taken as examples.

Conclusions

Replacing an equivalent amount of rumen-protected choline (25%) with 2.5 g of chromium propionate (containing 4 mg of chromium) per day in high density lipoprotein, cholesterol, insulin concentrations and milk in somatic cell counts aspect had a significant effect. Replacing 25% of rumen-protected choline with chromium propionate reduced production costs and improved dairy farming benefits.