Vitamins
Effects of Niacin Source on Epinephrine Stimulation of Plasma Nonesterified Fatty Acid and Glucose Concentrations, on Diet Digestibility and on Rumen Protozoal Numbers in Lactating Dairy Cows1 PETER S. ERICKSON,2 AHN M. TRUSK AND MICHAEL R. MURPHY3
Department of Animal Sciences, university of Illinois, Urbana, IL 61801 such situations lipid mobilization occurs to meet energy needs and may lead to ketosis. Metabolically, ketosis is characterized by increased blood concentrations of non esterified fatty acids (NEFA), ketonemia and hypoglycemia. Research with nonruminants has shown that nico tinic acid decreases lipolysis in adipose tissue (2-4). Nicotinic acid supplementation of dairy cow diets has increased milk production in some experiments (5-7), perhaps because of a decrease in ketosis (8). Several researchers have reported that NEFA and ketones were decreased by adding nicotinic acid to dairy cow diets (8-10). Recently, nicotinic acid supplementation has been shown to increase ruminai protozoa numbers (11) and microbial crude protein synthesis (12, 13). The objective of this study was to determine whether niacin (as nicotinic acid or nicotinamide) elicits its ketonemia-depressing effect by decreasing in vivo lipol ysis. Its effects on apparent diet digestibility and rumi nai protozoa number were also examined.
ABSTRACT Effects of niacin (nicotinic acid or nicotinamide) supplementation of dairy cow diets on ap parent total tract nutrient digestibility, milk yield and milk composition were determined using six mid-lac tation Holstein cows in a replicated 3x3 Latin square design arranged to test for residual treatment effects. Treatments were control, 12 g/d of nicotinic acid or 12 g/d of nicotinamide. Periods were 14 d long; d 1 to 4 served as an adaptation period before treatment ad ministration commenced (d 5 to 14). Effects of sup plemental niacin on plasma nonesterified fatty acid (NEFA) concentrations and plasma glucose concen trations were tested following saline injection on d 10. Blood was then sampled for 5.5 h at 15-min intervals. On d 13, cows were treated similarly except that epinephrine replaced saline. The area below d-10 curves was subtracted from the area below d-13 curves to serve as an indicator of niacin's effect on plasma NEFA and glucose concentration responses to epinephrine injection. Niacin treatments did not change the area differences for plasma glucose com pared to the control treatment; however, there was a trend for niacin to reduce the area difference compared to the control treatment for plasma NEFA. Niacin treatments did not alter dry matter intake, nutrient digestibility, milk yield or composition. Niacin supple mentation increased the number of entodinia protozoa in rumen fluid. J. Nutr. 120:1648-1653, 1990.
MATERIALS AND METHODS Six multiparous, mid-lactation Holstein cows (643 kg) from the University of Illinois dairy herd were used in a replicated 3x3 Latin square arranged to test residual treatment effects (14). Cows in one square had ruminai cannulae, but those in the other did not. Orthogonal comparisons tested the effects of niacin (nicotinic acid
INDEXING KEY WORDS:
•niacin •cows •epinephrine •protozoa
During the early stage of lactation, dairy cows are in negative energy balance. For example, a 600-kg dairy cow producing 40 kg/d of milk with 3.5% fat requires 37.3 Mcal/d (156.1 MJ/d) of net energy of lactation (NE,) (1). A cow consuming 20 kg of dry matter (DM) of a diet containing 1.6 Meal NE;/kg DM (6.69 MJ NE,/kg DM) would only obtain 85.8% of her energy requirement. In
'Supported by Illinois Agricultural Experiment Station, Hatch 35-0371 and a gift from Rhône-PoulencInc., Feed Additives Division, Atlanta, GA. 2Present address: Ralston Products, Inc., Suite 101,6780 Northern Blvd., East Syracuse, NY 13057. 3Towhom reprint requests should be addressed.
0022-3166/90 $3.00 ©1990 American Institute of Nutrition. Received 15 September 1989. Accepted 31 May 1990.
1648 Downloaded from https://academic.oup.com/jn/article-abstract/120/12/1648/4743979 by University of Glasgow user on 28 April 2018
1649
SUPPLEMENTAL NIACIN FOR DAIRY COWS
and nicotinamide) versus control, and of niacin source (nicotinic acid versus nicotinamide). All cows were fed a total mixed diet (Table 1)through out the experiment. The chemical composition of the diet is shown in Table 2. Cows were fed to insure a 10% feed refusal. Animals were maintained in a stanchion barn, offered fresh feed twice daily at 0500 and 1700 h and provided with water ad libitum. Cows were milked at 12-h intervals. Dry lot access was available from 2300 to 0500 h of the next day except for the days when catheters were in place. Experimental treatments were control, 12 g/d of supplemental nicotinic acid (Sigma Chemical, St. Louis, MO) and 12 g/d of supplemental nicotinamide (Sigma Chemical). These dosages were based on the common practice of feeding 6 to 12 g/d of niacin to decrease ketosis in commercial herds. Cows received either an empty gelatin capsule or a gelatin capsule containing 3 g of the appropriate supplement at 6-h intervals. Capsules were administered to ruminally cannulated cows via their fistulae whereas the other cows were dosed orally using a balling gun. Epinephrine and saline injection experiment. Peri ods were 14 d long. The first 4 d served as a recovery period between treatments. On d 5, treatment adminis tration commenced (d 5-14). Catheters were inserted into the jugular vein and filled with heparinized sterile saline on d 9. Heparinized saline was freshly prepared each period. Cows were weighed on d 7, 8 and 9. On d 10 at 1800 h, cows were injected with sterile saline (10 mL, intramuscularly). Blood samples were taken at 15-
TABLE 1 Diet composition Item
Amount % of diet dry matter
Corn silage Alfalfa-grass haylage High-moisture shelled corn Soybean meal Sodium bicarbonate Dicalcium phosphate Sodium sulfate Limestone Sodium chloride Trace mineral and vitamin mix1 Magnesium oxide
30.00 30.00 27.64 10.47 0.75 0.25 0.22 0.20 0.20 0.15 0.12
'University of Illinois Dairy #50826 (Goodlife Inc., Effingham, IL) guaranteed analysis: > 0.025% I, > 2.0% Fe, > 3.0% Zn, > 3.0% Mn, > 5% Mg, > 0.5% Cu, > 0.004% Co, > 0.015% Se, > 10% S, > 7.5% K, > 2,200,000 lU vitamin A/kg, > 660,000 lu vitamin D/kg, and > 7709 tu vitamin E/kg from calcium iodate, iron sulfate, zinc oxide, manganous oxide, magnesium sulfate, copper oxide, cobalt carbonate, sodium selenite, sulfur, potassium sulfate, retinyl acetate, cholecalciferol and all-rac-a-tocopherol. Downloaded from https://academic.oup.com/jn/article-abstract/120/12/1648/4743979 by University of Glasgow user on 28 April 2018
TABLE 2
Calculated nutrient content of diet (dry matter basis)1 Nutrient Crude protein, % Net energy of lactation, Meal/kg Acid detergent fiber, % Calcium, % Phosphorus, % Magnesium, % Potassium, % Sulfur, % Sodium, % Chloride, % Iron, mg/kg Zinc, mg/kg Copper, mg/kg Manganese, mg/kg Cobalt, mg/kg Iodine, mg/kg Selenium, mg/kg Vitamin A, ¡u/kg Vitamin D, ¡u/kg Vitamin E, lu/kg
Diet content 15.12 1.57 21 0.54 0.38 0.39 1.51 0.23 0.36 0.31 362 68
17 71 0.13 0.38 0.23 2312 991 12
'Content calculated from composition (Table 1| and data in réf. 1.
min intervals from 1730 to 2300 h. After each sampling, 5 mL of heparinized saline was infused through the catheter. Blood was centrifuged at 4000 x g for 10 min. Plasma was removed, frozen (-20°C)and later analyzed for NEFA (in vitro enzymatic colorimetrie method, Wako Pure Chemical Industries, Osaka, Japan) and glu cose (glucose assay, Sigma Chemical). On d 13 at 1800 h, epinephrine (0.03 mg/kg) in sterile saline was injected intramuscularly. The epinephrine dosage was the same as that used by Bassett (15) in sheep. Sample treatment and analyses were as for d 10. Data from d 10 provided baseline values for each cow. The area between d-10 and d-13 curves describing NEFA and glucose versus time, from 1815 to 2300 h, was the response criterion for treatment effects. Areas were measures using the trap ezoidal rule (16). Digestibility experiment. Apparent total tract nutri ent digestibility was determined by dosing with the digesta flow marker Cr2Os (20 g/d in gelatin capsules) between d 5 and 14. Dosing occurred just prior to each feeding. Feed samples were taken on d 8 through 12, orts were sampled on d 9 through 13 and fecal grab samples were taken at 12-h intervals on d 10 through 14. Dry matter intake was monitored throughout the treatment period. Feed, orts and feces were sampled, frozen and later composited by cow and period. The samples were dried at 45°C,and ground through a 2-mm screen in a Wiley mill (Arthur H. Thomas Co., Philadelphia, PA). They were analyzed for DM, N and ether extract (17) and for neutral detergent fiber and acid detergent fiber (18). Feces were also analyzed for Cr (19) using an atomic
1650
ERICKSON ET AL.
TABLE 3
TABLE 4
Mean dry matter intake, apparent total tract nutrient digestibility, milk production and milk composition for Holstein cows supplemented with 12 g/d of nicotinic acid or nicotinamide1
Mean milk production and milk composition on the day after epinephrine infection (d 14) of Holstein cows supplemented with 12 g/d of nicotinic acid or nicotinamide1
Treatment
Item Dry matter intake, kg/d
Treatment
Control
Nico tinic acid
Nicotinamide
19.8
19.6
19.6
SEM
Item
0.2
Milk, kg/d 4% Fat-corrected milk, kg/d Fat content, % Protein, kg/d Solids-not-fat, %
Apparent %Dry digestibility, matterNitrogenNeutral fiberAciddetergent fiberEther detergent extract2Milk,
Control
Nico tinic acid
Nicotinamide
SEM
22.5 19.4 3.16 0.69 7.96
22.7 19.6 3.12 0.70 7.85
22.7 19.5 3.08 0.69 8.08
0.6 0.5 0.08 0.02 0.13
'There were six cows in a replicated 3x3 Latin square. Orthogonal comparisons made were control vs. niacin and nicotinic nicotinamide.
acid vs.
kg/d4% kg/dFat Fat-corrected milk, %Protein, content, kg/dProtein RESULTS %Solids-not-fat, content, %62.364.249.345.463.424.221.23.190.773.167.9762.665.149.146.465.424.621.73.220.783.187.9662.364.849.849.361.024.521.43.180.773.158.021.00.70.91.6 'There were six cows in a replicated 3x3 Latin square. Orthogonal comparisons made were control vs. niacin and nicotinic nicotinamide. 2Nicotinic acid vs. nicotinamide differed [p < 0.05).
acid vs.
absorption spectrophotometer (Perkin-Elmer, Model 2380, Norwalk, CT). Milk production and composition. Milk production was monitored on d 5 through 14 of each period. Milk samples were composited on d 8, 11 and 14 according to milk production and were analyzed for solids-not-fat (20) and protein and fat content (infrared analysis, Dairy Lab Services, Dubuque, IA) Protozoa concentration experiment. On d 14 com posite samples of 150 mL of fluid from the ventral rumen of ruminally cannulated cows were removed by suction strainer inserted through the fistula, and 150 mL of fluid expressed from material in the dorsal rumen was taken at 5-h intervals from 0700 to 1700 h. Samples were filtered through one layer of cheesecloth. One volume of sample was mixed with 2 volumes of fixative stain (methylgreen-formalin-saline) (21). Subsamples were counted randomly in duplicate. Concentrations were estimated by counting protozoa in a modified FuchsRosenthal chamber (3 x 3 x 0.2 mm, Weber Scientific International, Middlesex, England) at a magnification of 125x. Statistics. Data were initially analyzed to test for residual treatment effects (14). In the absence of residual treatment effects, data were reanalyzed using the con ventional model for a replicated 3x3 Latin square. For the protozoa experiment, data were analyzed using the 3x3 Latin square model. Downloaded from https://academic.oup.com/jn/article-abstract/120/12/1648/4743979 by University of Glasgow user on 28 April 2018
In all statistical analyses, residual effects of treat ments were not significant. Dry matter intake and nu trient digestibility data are presented in Table 3. These variables did not differ except that cows receiving nico tinic acid had increased apparent total tract digestibility of ether extract compared to cows receiving nicotin amide; however, differences between niacin and control ether extract digestibility were not significant. There were no significant effects of niacin or source of niacin on milk production or composition (Table 3). The effects of epinephrine injection on milk production and composition are depicted in Table 4; however, the effects of treatments did not differ. Yield of milk and milk components tended to be lower after epinephrine injection. Differences between baseline and epinephrine injec tion areas for NEFA and glucose are shown in Table 5. Area differences between saline and epinephrine for NEFA and glucose concentration curves were similar (p > 0.1); however, supplementation of nicotinic acid or nicotinamide tended to reduce the NEFA area differ ence, indicating that supplementation of niacin may decrease lipolysis. Figures 1-6 depict epinephrine's effect on plasma concentrations of NEFA and glucose. Plasma NEFA concentrations in cows not receiving niacin (Fig. 1), in cows receiving nicotinic acid (Fig. 2) and in cows receiv ing nicotinamide (Fig. 3) suggest that niacin decreased lipolysis compared to that in control cows. Plasma glucose concentrations in cows not receiving niacin (Fig. 4), in cows receiving nicotinic acid (Fig. 5) and in cows receiving nicotinamide (Fig. 6) indicate that niacin may also decrease epinephrine-stimulated glycogenolysis. High olasma glucose concentrations (2.5- to 3-fold
1651
SUPPLEMENTAL NIACIN FOR DAIRY COWS o- oEpinephrine • — »Saline
TABLE 5
Area differences between saline and epinephrine injection for nonesterified fatty acids (NEFA) and glucose in blood plasma of Holstein cows supplemented with 12 g/d of nicotinic acid
400-T3 'o
300--
or nicotinamide1
0
Treatment
Item NEFA, \ieq/(L x h) Glucose, mg/(l 00 mLxh)
Control
Nicotinic acid
522 279
429 256
15 200+ Nicotinamide SEM 386 288
82 26
'Plasma samples were obtained at 15 min intervals for 5 h. There were six cows in a replicated 3x3 Latin square. Orthogonal compar isons made were control vs. niacin and nicotinic acid vs. nicotin amide.
that of the saline sham) may have been due to increased glycogenolysis and glucose synthesis from a-glycerolphosphate released during lipolysis. Prolonged action of the epinephrine injection may have accounted for the lack of significant area differences. Niacin supplementation increased total protozoa in rumen fluid (Table 6). The increase was due primarily to increased numbers of entodinia. DISCUSSION Supplementing nicotinic acid or nicotinamide to dairy cow diets did not influence dry matter intake or apparent total tract digestibility compared to those val ues in control cows. However, supplementing nicotinic acid did improve apparent total tract ether extract di-
500 T cr
u Õ
-I2 3 Hours Post-injection
-1
FIGURE 2 Effects of epinephrine (O) and saline (•)injec tions on mean plasma nonesterified fatty acid concentrations in cows receiving nicotinic acid. Mean standard errors were 24 and 13 (leq/L, respectively; n = 6 for each point.
gestibility. The reason for this response is not clear. The source of niacin did not affect any of the milk components or alter milk production. Milk production was not improved by supplementing diets of dairy cows in mid-lactation with niacin. In another study con ducted in mid-lactation, milk yield was increased when niacin was supplemented (7).Data from d 14, post-epinephrine injection, indicated that milk production did not differ among treatments,- however, epinephrine probably depressed milk yield. Supplementing diets with nicotinic acid or nicotin amide tended to reduce the difference in areas between NEFA baseline and epinephrine curves. Niacin may reduce the amount of NEFAreleased from adipose tissue and elicit its ketone-depressing effect in this manner. These data concur with an in vitro study in which nicotinic acid reduced NEFA released hito the medium
ouu-400-'300-200-100-o
o— o Epinephrine • »Saline
o Epinephrine »Salinef°^I •
400 • •
A
300 • • -a
100-Non— es
200 --
"O
a;
0)
„-,V~ •-•-•/-«--• ^^0— ^ O^y0 *liliI
Vo/0\./*~~"--«^«~*I
*
100--
-1
-t-
-i-
1 2 3 Hours Post-injection
FIGURE 1 Effects of epinephrine (O) and saline (•)injec tions on mean plasma nonesterified fatty acid concentrations in cows not receiving niacin. Mean standard errors were 45 and 16 neq/L, respectively; n = 6 for each point. Downloaded from https://academic.oup.com/jn/article-abstract/120/12/1648/4743979 by University of Glasgow user on 28 April 2018
114 t10123'-o-°
I
1
5 Hours Post—injection
FIGURE 3 Effects of epinephrine (O) and saline (•)injec tions on mean plasma nonesterified fatty acid concentrations in cows receiving nicotinamide. Mean standard errors were 34 and 17 neq/L, respectively; n = 6 for each point.
1652175-150-^-J
AL.jv-O^_o— ET Epinephrine• o »SalineA/
oEpinephrine• »Saline0-0-0--/•°^0 o/"*'^«-•-~*~~*^»14
Effects of Niacin Source on Epinephrine Stimulation of Plasma Nonesterified Fatty Acid and Glucose Concentrations, on Diet Digestibility and on Rumen Protozoal Numbers in Lactating Dairy Cows1 PETER S. ERICKSON,2 AHN M. TRUSK AND MICHAEL R. MURPHY3
Department of Animal Sciences, university of Illinois, Urbana, IL 61801 such situations lipid mobilization occurs to meet energy needs and may lead to ketosis. Metabolically, ketosis is characterized by increased blood concentrations of non esterified fatty acids (NEFA), ketonemia and hypoglycemia. Research with nonruminants has shown that nico tinic acid decreases lipolysis in adipose tissue (2-4). Nicotinic acid supplementation of dairy cow diets has increased milk production in some experiments (5-7), perhaps because of a decrease in ketosis (8). Several researchers have reported that NEFA and ketones were decreased by adding nicotinic acid to dairy cow diets (8-10). Recently, nicotinic acid supplementation has been shown to increase ruminai protozoa numbers (11) and microbial crude protein synthesis (12, 13). The objective of this study was to determine whether niacin (as nicotinic acid or nicotinamide) elicits its ketonemia-depressing effect by decreasing in vivo lipol ysis. Its effects on apparent diet digestibility and rumi nai protozoa number were also examined.
ABSTRACT Effects of niacin (nicotinic acid or nicotinamide) supplementation of dairy cow diets on ap parent total tract nutrient digestibility, milk yield and milk composition were determined using six mid-lac tation Holstein cows in a replicated 3x3 Latin square design arranged to test for residual treatment effects. Treatments were control, 12 g/d of nicotinic acid or 12 g/d of nicotinamide. Periods were 14 d long; d 1 to 4 served as an adaptation period before treatment ad ministration commenced (d 5 to 14). Effects of sup plemental niacin on plasma nonesterified fatty acid (NEFA) concentrations and plasma glucose concen trations were tested following saline injection on d 10. Blood was then sampled for 5.5 h at 15-min intervals. On d 13, cows were treated similarly except that epinephrine replaced saline. The area below d-10 curves was subtracted from the area below d-13 curves to serve as an indicator of niacin's effect on plasma NEFA and glucose concentration responses to epinephrine injection. Niacin treatments did not change the area differences for plasma glucose com pared to the control treatment; however, there was a trend for niacin to reduce the area difference compared to the control treatment for plasma NEFA. Niacin treatments did not alter dry matter intake, nutrient digestibility, milk yield or composition. Niacin supple mentation increased the number of entodinia protozoa in rumen fluid. J. Nutr. 120:1648-1653, 1990.
MATERIALS AND METHODS Six multiparous, mid-lactation Holstein cows (643 kg) from the University of Illinois dairy herd were used in a replicated 3x3 Latin square arranged to test residual treatment effects (14). Cows in one square had ruminai cannulae, but those in the other did not. Orthogonal comparisons tested the effects of niacin (nicotinic acid
INDEXING KEY WORDS:
•niacin •cows •epinephrine •protozoa
During the early stage of lactation, dairy cows are in negative energy balance. For example, a 600-kg dairy cow producing 40 kg/d of milk with 3.5% fat requires 37.3 Mcal/d (156.1 MJ/d) of net energy of lactation (NE,) (1). A cow consuming 20 kg of dry matter (DM) of a diet containing 1.6 Meal NE;/kg DM (6.69 MJ NE,/kg DM) would only obtain 85.8% of her energy requirement. In
'Supported by Illinois Agricultural Experiment Station, Hatch 35-0371 and a gift from Rhône-PoulencInc., Feed Additives Division, Atlanta, GA. 2Present address: Ralston Products, Inc., Suite 101,6780 Northern Blvd., East Syracuse, NY 13057. 3Towhom reprint requests should be addressed.
0022-3166/90 $3.00 ©1990 American Institute of Nutrition. Received 15 September 1989. Accepted 31 May 1990.
1648 Downloaded from https://academic.oup.com/jn/article-abstract/120/12/1648/4743979 by University of Glasgow user on 28 April 2018
1649
SUPPLEMENTAL NIACIN FOR DAIRY COWS
and nicotinamide) versus control, and of niacin source (nicotinic acid versus nicotinamide). All cows were fed a total mixed diet (Table 1)through out the experiment. The chemical composition of the diet is shown in Table 2. Cows were fed to insure a 10% feed refusal. Animals were maintained in a stanchion barn, offered fresh feed twice daily at 0500 and 1700 h and provided with water ad libitum. Cows were milked at 12-h intervals. Dry lot access was available from 2300 to 0500 h of the next day except for the days when catheters were in place. Experimental treatments were control, 12 g/d of supplemental nicotinic acid (Sigma Chemical, St. Louis, MO) and 12 g/d of supplemental nicotinamide (Sigma Chemical). These dosages were based on the common practice of feeding 6 to 12 g/d of niacin to decrease ketosis in commercial herds. Cows received either an empty gelatin capsule or a gelatin capsule containing 3 g of the appropriate supplement at 6-h intervals. Capsules were administered to ruminally cannulated cows via their fistulae whereas the other cows were dosed orally using a balling gun. Epinephrine and saline injection experiment. Peri ods were 14 d long. The first 4 d served as a recovery period between treatments. On d 5, treatment adminis tration commenced (d 5-14). Catheters were inserted into the jugular vein and filled with heparinized sterile saline on d 9. Heparinized saline was freshly prepared each period. Cows were weighed on d 7, 8 and 9. On d 10 at 1800 h, cows were injected with sterile saline (10 mL, intramuscularly). Blood samples were taken at 15-
TABLE 1 Diet composition Item
Amount % of diet dry matter
Corn silage Alfalfa-grass haylage High-moisture shelled corn Soybean meal Sodium bicarbonate Dicalcium phosphate Sodium sulfate Limestone Sodium chloride Trace mineral and vitamin mix1 Magnesium oxide
30.00 30.00 27.64 10.47 0.75 0.25 0.22 0.20 0.20 0.15 0.12
'University of Illinois Dairy #50826 (Goodlife Inc., Effingham, IL) guaranteed analysis: > 0.025% I, > 2.0% Fe, > 3.0% Zn, > 3.0% Mn, > 5% Mg, > 0.5% Cu, > 0.004% Co, > 0.015% Se, > 10% S, > 7.5% K, > 2,200,000 lU vitamin A/kg, > 660,000 lu vitamin D/kg, and > 7709 tu vitamin E/kg from calcium iodate, iron sulfate, zinc oxide, manganous oxide, magnesium sulfate, copper oxide, cobalt carbonate, sodium selenite, sulfur, potassium sulfate, retinyl acetate, cholecalciferol and all-rac-a-tocopherol. Downloaded from https://academic.oup.com/jn/article-abstract/120/12/1648/4743979 by University of Glasgow user on 28 April 2018
TABLE 2
Calculated nutrient content of diet (dry matter basis)1 Nutrient Crude protein, % Net energy of lactation, Meal/kg Acid detergent fiber, % Calcium, % Phosphorus, % Magnesium, % Potassium, % Sulfur, % Sodium, % Chloride, % Iron, mg/kg Zinc, mg/kg Copper, mg/kg Manganese, mg/kg Cobalt, mg/kg Iodine, mg/kg Selenium, mg/kg Vitamin A, ¡u/kg Vitamin D, ¡u/kg Vitamin E, lu/kg
Diet content 15.12 1.57 21 0.54 0.38 0.39 1.51 0.23 0.36 0.31 362 68
17 71 0.13 0.38 0.23 2312 991 12
'Content calculated from composition (Table 1| and data in réf. 1.
min intervals from 1730 to 2300 h. After each sampling, 5 mL of heparinized saline was infused through the catheter. Blood was centrifuged at 4000 x g for 10 min. Plasma was removed, frozen (-20°C)and later analyzed for NEFA (in vitro enzymatic colorimetrie method, Wako Pure Chemical Industries, Osaka, Japan) and glu cose (glucose assay, Sigma Chemical). On d 13 at 1800 h, epinephrine (0.03 mg/kg) in sterile saline was injected intramuscularly. The epinephrine dosage was the same as that used by Bassett (15) in sheep. Sample treatment and analyses were as for d 10. Data from d 10 provided baseline values for each cow. The area between d-10 and d-13 curves describing NEFA and glucose versus time, from 1815 to 2300 h, was the response criterion for treatment effects. Areas were measures using the trap ezoidal rule (16). Digestibility experiment. Apparent total tract nutri ent digestibility was determined by dosing with the digesta flow marker Cr2Os (20 g/d in gelatin capsules) between d 5 and 14. Dosing occurred just prior to each feeding. Feed samples were taken on d 8 through 12, orts were sampled on d 9 through 13 and fecal grab samples were taken at 12-h intervals on d 10 through 14. Dry matter intake was monitored throughout the treatment period. Feed, orts and feces were sampled, frozen and later composited by cow and period. The samples were dried at 45°C,and ground through a 2-mm screen in a Wiley mill (Arthur H. Thomas Co., Philadelphia, PA). They were analyzed for DM, N and ether extract (17) and for neutral detergent fiber and acid detergent fiber (18). Feces were also analyzed for Cr (19) using an atomic
1650
ERICKSON ET AL.
TABLE 3
TABLE 4
Mean dry matter intake, apparent total tract nutrient digestibility, milk production and milk composition for Holstein cows supplemented with 12 g/d of nicotinic acid or nicotinamide1
Mean milk production and milk composition on the day after epinephrine infection (d 14) of Holstein cows supplemented with 12 g/d of nicotinic acid or nicotinamide1
Treatment
Item Dry matter intake, kg/d
Treatment
Control
Nico tinic acid
Nicotinamide
19.8
19.6
19.6
SEM
Item
0.2
Milk, kg/d 4% Fat-corrected milk, kg/d Fat content, % Protein, kg/d Solids-not-fat, %
Apparent %Dry digestibility, matterNitrogenNeutral fiberAciddetergent fiberEther detergent extract2Milk,
Control
Nico tinic acid
Nicotinamide
SEM
22.5 19.4 3.16 0.69 7.96
22.7 19.6 3.12 0.70 7.85
22.7 19.5 3.08 0.69 8.08
0.6 0.5 0.08 0.02 0.13
'There were six cows in a replicated 3x3 Latin square. Orthogonal comparisons made were control vs. niacin and nicotinic nicotinamide.
acid vs.
kg/d4% kg/dFat Fat-corrected milk, %Protein, content, kg/dProtein RESULTS %Solids-not-fat, content, %62.364.249.345.463.424.221.23.190.773.167.9762.665.149.146.465.424.621.73.220.783.187.9662.364.849.849.361.024.521.43.180.773.158.021.00.70.91.6 'There were six cows in a replicated 3x3 Latin square. Orthogonal comparisons made were control vs. niacin and nicotinic nicotinamide. 2Nicotinic acid vs. nicotinamide differed [p < 0.05).
acid vs.
absorption spectrophotometer (Perkin-Elmer, Model 2380, Norwalk, CT). Milk production and composition. Milk production was monitored on d 5 through 14 of each period. Milk samples were composited on d 8, 11 and 14 according to milk production and were analyzed for solids-not-fat (20) and protein and fat content (infrared analysis, Dairy Lab Services, Dubuque, IA) Protozoa concentration experiment. On d 14 com posite samples of 150 mL of fluid from the ventral rumen of ruminally cannulated cows were removed by suction strainer inserted through the fistula, and 150 mL of fluid expressed from material in the dorsal rumen was taken at 5-h intervals from 0700 to 1700 h. Samples were filtered through one layer of cheesecloth. One volume of sample was mixed with 2 volumes of fixative stain (methylgreen-formalin-saline) (21). Subsamples were counted randomly in duplicate. Concentrations were estimated by counting protozoa in a modified FuchsRosenthal chamber (3 x 3 x 0.2 mm, Weber Scientific International, Middlesex, England) at a magnification of 125x. Statistics. Data were initially analyzed to test for residual treatment effects (14). In the absence of residual treatment effects, data were reanalyzed using the con ventional model for a replicated 3x3 Latin square. For the protozoa experiment, data were analyzed using the 3x3 Latin square model. Downloaded from https://academic.oup.com/jn/article-abstract/120/12/1648/4743979 by University of Glasgow user on 28 April 2018
In all statistical analyses, residual effects of treat ments were not significant. Dry matter intake and nu trient digestibility data are presented in Table 3. These variables did not differ except that cows receiving nico tinic acid had increased apparent total tract digestibility of ether extract compared to cows receiving nicotin amide; however, differences between niacin and control ether extract digestibility were not significant. There were no significant effects of niacin or source of niacin on milk production or composition (Table 3). The effects of epinephrine injection on milk production and composition are depicted in Table 4; however, the effects of treatments did not differ. Yield of milk and milk components tended to be lower after epinephrine injection. Differences between baseline and epinephrine injec tion areas for NEFA and glucose are shown in Table 5. Area differences between saline and epinephrine for NEFA and glucose concentration curves were similar (p > 0.1); however, supplementation of nicotinic acid or nicotinamide tended to reduce the NEFA area differ ence, indicating that supplementation of niacin may decrease lipolysis. Figures 1-6 depict epinephrine's effect on plasma concentrations of NEFA and glucose. Plasma NEFA concentrations in cows not receiving niacin (Fig. 1), in cows receiving nicotinic acid (Fig. 2) and in cows receiv ing nicotinamide (Fig. 3) suggest that niacin decreased lipolysis compared to that in control cows. Plasma glucose concentrations in cows not receiving niacin (Fig. 4), in cows receiving nicotinic acid (Fig. 5) and in cows receiving nicotinamide (Fig. 6) indicate that niacin may also decrease epinephrine-stimulated glycogenolysis. High olasma glucose concentrations (2.5- to 3-fold
1651
SUPPLEMENTAL NIACIN FOR DAIRY COWS o- oEpinephrine • — »Saline
TABLE 5
Area differences between saline and epinephrine injection for nonesterified fatty acids (NEFA) and glucose in blood plasma of Holstein cows supplemented with 12 g/d of nicotinic acid
400-T3 'o
300--
or nicotinamide1
0
Treatment
Item NEFA, \ieq/(L x h) Glucose, mg/(l 00 mLxh)
Control
Nicotinic acid
522 279
429 256
15 200+ Nicotinamide SEM 386 288
82 26
'Plasma samples were obtained at 15 min intervals for 5 h. There were six cows in a replicated 3x3 Latin square. Orthogonal compar isons made were control vs. niacin and nicotinic acid vs. nicotin amide.
that of the saline sham) may have been due to increased glycogenolysis and glucose synthesis from a-glycerolphosphate released during lipolysis. Prolonged action of the epinephrine injection may have accounted for the lack of significant area differences. Niacin supplementation increased total protozoa in rumen fluid (Table 6). The increase was due primarily to increased numbers of entodinia. DISCUSSION Supplementing nicotinic acid or nicotinamide to dairy cow diets did not influence dry matter intake or apparent total tract digestibility compared to those val ues in control cows. However, supplementing nicotinic acid did improve apparent total tract ether extract di-
500 T cr
u Õ
-I2 3 Hours Post-injection
-1
FIGURE 2 Effects of epinephrine (O) and saline (•)injec tions on mean plasma nonesterified fatty acid concentrations in cows receiving nicotinic acid. Mean standard errors were 24 and 13 (leq/L, respectively; n = 6 for each point.
gestibility. The reason for this response is not clear. The source of niacin did not affect any of the milk components or alter milk production. Milk production was not improved by supplementing diets of dairy cows in mid-lactation with niacin. In another study con ducted in mid-lactation, milk yield was increased when niacin was supplemented (7).Data from d 14, post-epinephrine injection, indicated that milk production did not differ among treatments,- however, epinephrine probably depressed milk yield. Supplementing diets with nicotinic acid or nicotin amide tended to reduce the difference in areas between NEFA baseline and epinephrine curves. Niacin may reduce the amount of NEFAreleased from adipose tissue and elicit its ketone-depressing effect in this manner. These data concur with an in vitro study in which nicotinic acid reduced NEFA released hito the medium
ouu-400-'300-200-100-o
o— o Epinephrine • »Saline
o Epinephrine »Salinef°^I •
400 • •
A
300 • • -a
100-Non— es
200 --
"O
a;
0)
„-,V~ •-•-•/-«--• ^^0— ^ O^y0 *liliI
Vo/0\./*~~"--«^«~*I
*
100--
-1
-t-
-i-
1 2 3 Hours Post-injection
FIGURE 1 Effects of epinephrine (O) and saline (•)injec tions on mean plasma nonesterified fatty acid concentrations in cows not receiving niacin. Mean standard errors were 45 and 16 neq/L, respectively; n = 6 for each point. Downloaded from https://academic.oup.com/jn/article-abstract/120/12/1648/4743979 by University of Glasgow user on 28 April 2018
114 t10123'-o-°
I
1
5 Hours Post—injection
FIGURE 3 Effects of epinephrine (O) and saline (•)injec tions on mean plasma nonesterified fatty acid concentrations in cows receiving nicotinamide. Mean standard errors were 34 and 17 neq/L, respectively; n = 6 for each point.
1652175-150-^-J
AL.jv-O^_o— ET Epinephrine• o »SalineA/
oEpinephrine• »Saline0-0-0--/•°^0 o/"*'^«-•-~*~~*^»14
