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Effect of Propylene Glycol Dosage During Feed Restriction on Metabolites in Blood of Prepartum Holstein Heifers
Effect of Propylene Glycol Dosage During Feed Restriction on Metabolites in Blood of Prepartum Holstein Heifers RIC R. GRUMMER,’ JON C. WINKLER, SANDY J. BERTICS, and VAUGHN A. STUDER Department of Dairy Science University of Wisconsin Madison 53706 ABSTRACT
INTRODUCTION
Different doses of propylene glycol were compared for lowering plasma NEFA concentration during restricted feed intake. Eight Holstein heifers, averaging 90 d prior to calving at initiation of the trial, were in a 4 x 4 Latin square design with 12-d periods. Heifers consumed alfalfa silage on an ad libitum basis during d 1 to 7 of each period. During d 8 to 12, heifers were gradually restricted to 50% of ad libitum intake. Heifers received an oral drench of 0, 296. 592, or 887 ml of propylene glycol once daily at 6 h prior to feeding on d 8 to 12. Propylene glycol linearly increased glucose and insulin and decreased BHBA and NEFA in blood. Quadratic effects of propylene glycol on plasma glucose, BHBA, and NEFA also occurred; response per milliliter of propylene glycol was greatest at the lowest dose. The highest dose of propylene glycol returned blood glucose, insulin, and NEFA concentrations to those prior to feed restriction. Ruminal acetate to propionate ratio decreased as propylene glycol dose was increased, indicating ruminal conversion of propylene glycol to propionate. A dose of 296 ml of propylene glycol was almost as effective as a dose of 887 ml in reducing lipid mobilization during restricted feed intake. (Key words: propylene glycol, fatty liver, ketones, nonesterified fatty acids)
Considerable triglyceride PG) is deposited in bovine liver by d 1 following calving (5). Feed intake depression prior to calving and stress during calving probably accounts for elevated plasma NEFA during the periparturient period (13, 15). Hepatic fatty acid uptake is positively associated with plasma NEFA concentrations (1). During accelerated NEFA uptake, TG synthesis and storage occur, partially because of the slow rate of export of very low density lipoprotein TG by the ruminant liver (8). Rate-limiting factors for very low density TG export are unknown; therefore, methods to increase the rate of export have been difficult to identify. Methods to reduce fatty acid mobilization from adipose tissue are known and may be useful near calving to reduce TG accumulation in the liver. Fatty liver may precede development of clinical ketosis (16). Techniques to reduce hepatic TG may reduce the incidence of ketosis. Propylene glycol (PG)has been an effective treatment for clinical ketosis (7), probably because of its ability to lower NEFA concentration in plasma (13). Recently, we (13) demonstrated that administration of PG during the final week prior to parturition can reduce hepatic TG at d 1 postpartum. However, the amount administered as an oral drench once daily was approximately four to eight times greater than that typically recommended for treatment of ketosis. The objective of this study was to evaluate the effectiveness of various doses of PG in reducing plasma NEFA concentrations during restriction of feed intake.
Abbreviation key: PG = propylene glycol, TG = triglyceride.
Received January 18. 1994. Accepted July 26. 1994. ‘Reprint requests: 1675 Observatory Drive, Madison, WI 53706. 1994 J Dairy Sci 77:3618-3623
MATERIALS AND METHODS
The following model was developed to estimate the effectiveness of PG dosage. Eight Holstein heifers that averaged 90 d prior to expected calving were used in a replicated 4 x 4 Latin square design; each period was 12 d.
3618
DOSE RESPONSE TO PROPYLENE GLYCOL
3619
All heifers consumed alfalfa silage ad libitum 10, 9.4 for the first 7 d of each period; for the entire trial, vitamins and minerals were mixed with Restricted Feed Intake, d 12 wheat middlings, and the mixture was fed at the rate of .45 kg/d per cow to meet requirements (9). Average DMI of silage by each heifer was calculated for d 5 to 7 of each period. The amount of silage offered was restricted to 90, 80, and 70% of ad libitum intake on d 8,9, and 10 of each period and 50% of ad MLibhn 0 1% 592 887 libitum intake on d 11 and 12. Feed intake lnhke restriction was intended to stimulate mobilizaDose of Propylene Glycol, ml'd d7 tion of fatty acid in adipose tissue and to mimic the feed intake depression that usually Figure. 1. The DMI of heifers prior to (d 7, SE = .4) occurs during the final 5 to 7 d prior to calv- and during (d 12, SE = . l ) feed restriction and administraing. Beginning on d 8 of each period, heifers tion of propylene glycol. The DMI was not different (P > were given 0,296, 592, or 887 ml of PG as an .15) among treatments during feed restriction. oral drench once daily 6 h prior to their feeding once daily at 1500 h. Blood was sampled on d 7 of each period 6 h prior to feeding and on d 12 at 360, 345, tiparous periparturient cows, and liver biopsies 330, 300, 270, 180, and 0 min prior to feeding. for evaluation of the effectiveness of different These times corresponded to 0, 15, 30, 60, 90, 180, and 360 min following delivery of PG. doses of PG for reducing fatty liver. A switchAnalysis of glucose, NEFA, BHBA, and insu- back design allowed us to reduce the number lin in blood were as described previously (13). of animals required for the experiment; howSamples obtained 15 min following the PG ever, it prevented the use of cows at calving. drench were not analyzed for BHBA. Ruminal Use of animals near calving was considered to fluid was sampled via stomach tube 2 h prior be desirable; therefore, periods were as short to feeding (4 h following PG drench) on d 7 as possible. Experiment length (48 d) precluded and 12 of each period. Ruminal fluid (50 ml) the use of mature nonlactating cows targeted to was acidified with 1.0 ml of 50% (volhol) have a standard dry period (45 to 60 d) because H 2 S O 4 and frozen until analysis. Molar per- we did not want the final period of the Latin centages of VFA were determined on all rumi- square to coincide with dramatic physiological nal fluid samples by GLC (Perkin-Elmer Au- changes that occur near calving. Consequently, tosystem, Norwalk, cr) using GP 10% SP- heifers that were approximately 90 d from 120011% H3P04 on 80/100 Chromasorb W calving at the start of the experiment were AW column packing (Supelco, Inc., Bellefonte, chosen as the experimental unit. Depletion of PA) as described previously (14). TG from the liver is slow, probably because of Data were analyzed by ANOVA using the general linear models procedure of SAS (1 1). slow rates of very low density lipoprotein exSources of variation in the model included port. This condition precluded using hepatic square, cow(square), period, treatment, square TG content as a criterion for assessing the x treatment, square x period, and treatment x effectiveness of PG dose because of carry-over period. For testing square effects, the mean effects across periods. The plasma NEFA consquare for cow(square) was used as the error centration is positively correlated with hepatic term. All other sources of variation were tested fatty acid uptake (1) and hepatic TG concentrausing the residual error mean square. Contrasts tion (2) and was considered to be the major were linear effect of PG, quadratic effect of criterion for assessing the effectiveness of PG PG, and 0 versus 296 + 592 + 887 ml of PG. dose. Average DMI of heifers on d 7 and 12 of RESULTS AND DISCUSSION each period are shown in Figure 1. The reducInsufficient resources precluded the use of a tion in DMI between d 7 and 12 was 4096, randomized complete block design, mul- which had been intended. The DMI were simiJournal of Dairy Science Vol. 77, No. 12, 1994
3620
GRUMMER ET AL
TABLE 1. Blood metabolites of Holstein heifers prior to (d 7) and during (d 12) feed restriction and administration of propylene glycol (PG).I d 12
d 7 Glucose? mg/dl Insulin,3 pIU/ml BHBA: mg/dl NEFA: @eq/L
81.5 18.1 10.4 278
SE 2.1 2.1 1.3 19
0 d d of PG
296 d d of PG
592 mVd of PG
887 mVd of PG
75.2 13.0 8.5 746
80.0 17.7 4.8 425
81.1 18.2 3.6 332
82.0 19.8 3.9 282
SE .5 .7 .2 11
IThe values for d 7 correspond to blood sampled 6 h prior to feeding. The values for d 12 are averages for multiple blood samples that were obtained between 6 h prior to feeding and at feeding. Glucose, BHBA, and NEFA were assayed in plasma. and insulin was assayed in serum. 2Linear effect of PG (P < ,001); quadratic effect of PG (P < .Ol); PG versus no PG (P < .OOOI). 3Linear effect of PG (P < .05); PG versus no PG (P < .05). 4Linear effect of PG (P < .Ol); quadratic effect of PG (P < .05); PG versus no PG (P < .01).
lar (P > .15) among treatments on d 12, which was important because we did not want treatment effects to be confounded by variable DMI.No effects of PG occurred on DMI of early lactation cows fed at 3, 6, or 9% of the concentrate (4). Feed intake of nonlactating cows was not decreased until PG intake exceeded 5% of dietary DM (3), which was in excess of the amount we drenched. Plasma and serum metabolite concentrations at 6 h prior to feeding on d 7 and average concentrations for all sampling times on d 12 are in Table 1. Concentrations of glucose, insulin, BHBA, and NEFA at 6 h prior to feeding on d 7 and 12 for heifers not receiving PG were 81.5 and 78.0 mg/dl, 18.1 and 14.2 pIUI ml, 10.4 and 8.4 mg/dl, and 278 and 771 Feq/ L. These changes would be expected with energy restriction. The decrease in BHBA concentration is probably accounted for by a reduction in BHBA production by the portaldrained viscera (6). Provided as an oral drench, PG increased plasma glucose (P < .OOOl) and decreased BHBA and NEFA concentrations (P < .Ol), in agreement with results from previous studies (3, 12) conducted using PG as an oral drench or feed additive for postpartum dairy cows. The decrease in plasma NEFA may have been mediated by an increase in the antilipolytic hormone insulin (Pc .OS). An increase in PG dose caused a linear increase in plasma glucose and serum insulin (P < .001 and P < .05; Figures 2 and 3) and a linear decrease in Journal of Dairy Science Vol. 77, No. 12, 1994
plasma BHBA and NEFA concentrations (P < .01; Figures 4 and 5). There was also a quadratic effect of the increasing PG dose on plasma glucose, BHBA, and NEFA (Figures 2, 4, and 5) that reflected a diminishing response to PG as dose was increased. Time by treatment interactions were observed for serum insulin (P c .OOOl) and plasma NEFA (P < .OOOl) and BHBA (P < .06) concentrations. These interactions reflected a rapid change in plasma metabolite concentrations after dosing PG treated heifers but not control heifers.
"1
0
100
zw
100
.loo
M i n u t e s Postdrench
Figure 2. Effect of oral drench of propylene glycol (---A---),296 (A), 592 (u) or 887 (C)mVd on glucose concentrations in plasma (SE = .5). Treatment x time interaction was not significant (P > .15). Significant contrasts were linear effect of PG (P < ,001). quadratic effect of PG (P < .Ol).and PG versus no PG (P < (pG) of 0
.oaol).
362 1
DOSE RESPONSE TO PROPYLENE GLYCOL 1zw
-
1000-
0
0
1W
2 0
300
400
Minutes Postdrench
Figure 3. Effect of oral drench doses of propylene glycol (pG) of 0 (---A---), 296 (A), 592 (-C-), or 887 (A) d d on serum insulin concentrations (SE = .7). Significant contraSts were treatment x time interaction (P < .oOOl),linear effect of PG (P e .05), and PG versus no PG (P e .05).
1m
ZOO
3w
4.30
Minutes Postdrench
Figure 5. Effect of oral drench doses of propylene glycol (E) of 0 (---A-),296 (4-4. 592 (&), or 887 (L) mVd on plasma BHBA concentrations (SE = .2). Significant contmts were treatment x time interaction (P e .Xi), linear effect of PG (P < .Ol), quadratic effect of FG (P < .05), and PG versus no PG (P e .01).
Relatively little advantage was obtained from increased dose of PG >296 mud. Sauer et al. (12) fed PG as 3, 6, or 9% of concentrate to cows consuming 1 kg of concentrate/4 kg of milk produced (approximately 5 kg/d of concentrate) during the first 8 wk of lactation; PG had minor effects on blood glucose concentrations; NEFA concentrations were reduced when PG was fed as 6% of concentrate, and no additional benefits were observed by increasing the amount to 9% of concentrate. Blood ketones were reduced at all levels of dietary
PG, but only a slight advantage was obtained by increasing PG >3% of concentrate. When PG was fed at 3% of concentrate, it provided approximately 150 mud of PG per cow. An oral drench of 125 ml/d of PG to cows exhibiting a positive milk ketone test did not hasten recovery (10). Use of PG shifted the molar percentages of ruminal VFA (P c .01; Table 2). The molar percentage of isobutyrate appeared to increase; however, PG coelutes from the gas chromatography column with isobutyrate. The most dramatic shifts were linear decreases (P c .OOOl) and quadratic effects (P c .001) in acetate and linear increases (P c .OS)and quadratic effects (P e .Ol) in propionate that were due to in1 creasing PG dose. The shift in ruminal VFA confirms data of Waldo and Schultz (17). Total ruminal VFA concentration was reduced in vivo, and PG was not metabolized during in vitro incubations, leading Emery et al. (3) to conclude that PG is absorbed intact by the gut. Measurements made in vitro were within 24 h of PG administration; therefore, conversion of PG to propionate may occur after more a 1W ZW 300 m prolonged exposure. If PG is not converted to M i n u t e s Postdrench propionate, our results would have to be exFigure. 4. Effect of oral drench doses of propylene plained by a shift in microbial populations 296 (A), 592 (-o-) or 887 toward organisms that produce propionate. Beglycol (PG) of 0 (---A---), (a mVd) on plasma NEFA concentrations (SE = 11). cause of the short duration of PG administraSignificant contrasts were treatment x time interaction (P < .oOOl). linear effect of PG (P c .Ol), quadratic effect of tion during our trial, a shift in microbial popuPG (P e .05), and PG versus no PG (P < .01). lations is not considered to be likely. Journal of Dairy Science Vol. 77, No. 12, 1994
3622
GRUMMER ET AL
TABLE 2. Rumen VFA' (molesl100 mol) and acetate to propionate ratio of Holstein heifers prior to (d 7) and during (d 12) feed restriction and administration of propylene glycol (PG).
d 12 296 d d of PG
592 mUd of PG
887 mYd of PG
d 7
SE
64.4 19.1
1.2 1 .o
69.1 16.9
51 6 33 5
54.0 26.9
49 1 25.4
5 8
3. I 9.5 2.2 I .7 3.4
<. 1 .7
3 .O 7.5 2.3 1.3 4.1
4.2 6.0 2.4 2.2 1.6
9.0 6.2 1.9 2.1 2.0
16.6 5.5 1.8 1.9 2.0
.3 .3 <.l <,l <.l
~
Acetate (AY Propionate (PY Isobutyrate plus PG1.4 Butyrates Isovalerate6 Valerate' A:P*
0 mUd of PG
SE
~
<.I
<.1 <.1
'PG coelutes with isobutyrate. *Linear effect of PG (P < .OOO1); quadratic effect of PG (P < ,001); PG v e m s no PG (P < .OOO1). 3Linear effect of PG (P < .05); quadratic effect of PG (P < .Ol); PG versus no PG (P < .01). 4Linear effect of PG (P < .OOOl); quadratic effect of PG (P < .Ol); PG versus no PG (P < .001). 5Linear effect of PG (P < .05); PG versus no PG (P < .05). 6Linear effect of PG ( P < .Ol); quadratic effect of PG (P < .05); PG versus no PG (P < .01). 7Linear effect of PG (P < .Ol); quadratic effect of PG (P e 0 0 1 ) ; PG versus no PG (P < .001).
CONCLUSIONS
Data from the trial indicate that 296 ml of PG given as an oral drench once daily was almost as effective as 887 ml of PG for reducing plasma NEFA concentrations in heifers that are feed restricted and 1 to 3 mo from calving. Heifers were feed restricted to mimic the feed intake depression that occurs during the final days prior to calving. The concentration of plasma NEFA during feed restriction was similar to that near calving (13, 15). Because plasma NEFA is positively associated with hepatic NEFA uptake and TG concentration, the model employed for this experiment may be suitable for screening feeding strategies or treatments designed to reduce hepatic TG at calving.
REFERENCES 1 Bell. A. W . 1980. Lipid metabolism in the liver and
selected tissues and in the whole body of ruminant animals. Prog. Lipid Res. 18:117. 2Bertics. S. J.. R. R. Grummer, C. Cadorniga-Valino, and E. E. Stoddard. 1992. Effect of prepartum dry matter intake on liver triglyceride concentration and early lactation. J. Dairy Sci. 751914. 3 Emery, R. S., N. Burg, L. D. Brown, and G. N. Blank. Journal of Dairy Science Vol. 77, No. 12. 1994
1964. Detection, occurrence, and prophylactic treatment of borderline ketosis with propylene glycol feeding. J. Dairy Sci. 47:1074. 4 Fisher, L. J., J. D. Erfle, G. A. Lodge, and F. D. Sauer. 1973. Effects of propylene glycol or glycerol supplementation of the diet of dairy cows on feed intake, milk yield and composition, and incidence of ketosis. Can. J. Anim. Sci. 53:289. 5 Grummer, R. R. 1994. Etiology of lipid-related metabolic disorders in periparturient cattle. J. Dairy Sci. 77 :3882. 6 Heitmann, R. N., S. C. Sensenig, C. K. Reynolds, J. Marco Fernandez, and D. J. Dawes. 1986. Changes in energy metabolite and regulatory hormone concentrations and net fluxes across splanchnic and peripheral tissues in fed and progressively fasted ewes. J. Nutr. 116:2516. 7Herdt, T. H.. and R. S. Emery. 1992. Therapy of diseases of ruminant intermediary metabolism. Vet. Clin. North Am. Food Anim. Pract. 8:91. 8 Kleppe, 8 . B., R. J. Aiello, R. R. Gmmmer, and L. E. Armentano. 1988. Triglyceride accumulation and very low density lipoprotein secretion by rat and goat hepatocytes in vitro. J. Dairy Sci. 71:1813. 9 National Research Council. 1989. Nutrient Requirements of Dairy Cattle. 6th rev. ed. Natl. Acad. Sci., Washington. Dc. 10 Ruegsegger. G. J., and L. H. Schultz. 1986. Use of a combination of propylene glycol and niacin for subclinical ketosis. J. Dairy Sci. 69:1411. 1 1 SAS@ User's Guide: Statistics, Version 5 Edition. 1985. SAS Inst., Inc., C q , NC. 12 Sauer. F. D., J. D. Erfle. and L. J. Fisher. 1973. Propylene glycol and glycerol as a feed additive for
DOSE RESPONSE TO PROPYLENE GLYCOL lactating dairy cows: an evaluation of blood metabolite parameters. Can. J. A i m . Sci. 53:265. 13 Studer, V. A., R. R. Grummer, S . J. Bertics, and C.K. Reynolds. 1993. Effect of prepartum propylene glycol administration on periparturient fatty liver in d;ilry cows. J. Dairy Sci. 76:2931. 14Supelco. 1975. GC Separation of VFA C2-C5. Bull. 749B. Supelco, Inc., Bellefonte, PA. 15 Vasquez-Anon, M.. S.J. Bertics, M. L. Luck, and R. R. Grummer. 1993. R e - and post-partum liver
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triglyceride and plasma metabolites in dairy cows. J. Dairy Sci. 7qSuppl. 1):289.(Abstr.) 16 Veenhuizen. J. J., J. K. Drackley, M. J. Richard, T P. Sanderson, L. D. Miller, and J. W. Young. 1991. Metabolic changes in blood and liver during development and the treatment of experimental fatty liver and ketosis in cows. J. Dairy Sci. 74:4238. 17 Waldo, D. R., and L. H. Schultz. 1960. Blood and mmen changes following the intra-ruminal administration of glycogenic materials. J . Dairy Sci. 43:496.
Journal of Dairy Science Vol. 77, No. 12, 1994
INTRODUCTION
Different doses of propylene glycol were compared for lowering plasma NEFA concentration during restricted feed intake. Eight Holstein heifers, averaging 90 d prior to calving at initiation of the trial, were in a 4 x 4 Latin square design with 12-d periods. Heifers consumed alfalfa silage on an ad libitum basis during d 1 to 7 of each period. During d 8 to 12, heifers were gradually restricted to 50% of ad libitum intake. Heifers received an oral drench of 0, 296. 592, or 887 ml of propylene glycol once daily at 6 h prior to feeding on d 8 to 12. Propylene glycol linearly increased glucose and insulin and decreased BHBA and NEFA in blood. Quadratic effects of propylene glycol on plasma glucose, BHBA, and NEFA also occurred; response per milliliter of propylene glycol was greatest at the lowest dose. The highest dose of propylene glycol returned blood glucose, insulin, and NEFA concentrations to those prior to feed restriction. Ruminal acetate to propionate ratio decreased as propylene glycol dose was increased, indicating ruminal conversion of propylene glycol to propionate. A dose of 296 ml of propylene glycol was almost as effective as a dose of 887 ml in reducing lipid mobilization during restricted feed intake. (Key words: propylene glycol, fatty liver, ketones, nonesterified fatty acids)
Considerable triglyceride PG) is deposited in bovine liver by d 1 following calving (5). Feed intake depression prior to calving and stress during calving probably accounts for elevated plasma NEFA during the periparturient period (13, 15). Hepatic fatty acid uptake is positively associated with plasma NEFA concentrations (1). During accelerated NEFA uptake, TG synthesis and storage occur, partially because of the slow rate of export of very low density lipoprotein TG by the ruminant liver (8). Rate-limiting factors for very low density TG export are unknown; therefore, methods to increase the rate of export have been difficult to identify. Methods to reduce fatty acid mobilization from adipose tissue are known and may be useful near calving to reduce TG accumulation in the liver. Fatty liver may precede development of clinical ketosis (16). Techniques to reduce hepatic TG may reduce the incidence of ketosis. Propylene glycol (PG)has been an effective treatment for clinical ketosis (7), probably because of its ability to lower NEFA concentration in plasma (13). Recently, we (13) demonstrated that administration of PG during the final week prior to parturition can reduce hepatic TG at d 1 postpartum. However, the amount administered as an oral drench once daily was approximately four to eight times greater than that typically recommended for treatment of ketosis. The objective of this study was to evaluate the effectiveness of various doses of PG in reducing plasma NEFA concentrations during restriction of feed intake.
Abbreviation key: PG = propylene glycol, TG = triglyceride.
Received January 18. 1994. Accepted July 26. 1994. ‘Reprint requests: 1675 Observatory Drive, Madison, WI 53706. 1994 J Dairy Sci 77:3618-3623
MATERIALS AND METHODS
The following model was developed to estimate the effectiveness of PG dosage. Eight Holstein heifers that averaged 90 d prior to expected calving were used in a replicated 4 x 4 Latin square design; each period was 12 d.
3618
DOSE RESPONSE TO PROPYLENE GLYCOL
3619
All heifers consumed alfalfa silage ad libitum 10, 9.4 for the first 7 d of each period; for the entire trial, vitamins and minerals were mixed with Restricted Feed Intake, d 12 wheat middlings, and the mixture was fed at the rate of .45 kg/d per cow to meet requirements (9). Average DMI of silage by each heifer was calculated for d 5 to 7 of each period. The amount of silage offered was restricted to 90, 80, and 70% of ad libitum intake on d 8,9, and 10 of each period and 50% of ad MLibhn 0 1% 592 887 libitum intake on d 11 and 12. Feed intake lnhke restriction was intended to stimulate mobilizaDose of Propylene Glycol, ml'd d7 tion of fatty acid in adipose tissue and to mimic the feed intake depression that usually Figure. 1. The DMI of heifers prior to (d 7, SE = .4) occurs during the final 5 to 7 d prior to calv- and during (d 12, SE = . l ) feed restriction and administraing. Beginning on d 8 of each period, heifers tion of propylene glycol. The DMI was not different (P > were given 0,296, 592, or 887 ml of PG as an .15) among treatments during feed restriction. oral drench once daily 6 h prior to their feeding once daily at 1500 h. Blood was sampled on d 7 of each period 6 h prior to feeding and on d 12 at 360, 345, tiparous periparturient cows, and liver biopsies 330, 300, 270, 180, and 0 min prior to feeding. for evaluation of the effectiveness of different These times corresponded to 0, 15, 30, 60, 90, 180, and 360 min following delivery of PG. doses of PG for reducing fatty liver. A switchAnalysis of glucose, NEFA, BHBA, and insu- back design allowed us to reduce the number lin in blood were as described previously (13). of animals required for the experiment; howSamples obtained 15 min following the PG ever, it prevented the use of cows at calving. drench were not analyzed for BHBA. Ruminal Use of animals near calving was considered to fluid was sampled via stomach tube 2 h prior be desirable; therefore, periods were as short to feeding (4 h following PG drench) on d 7 as possible. Experiment length (48 d) precluded and 12 of each period. Ruminal fluid (50 ml) the use of mature nonlactating cows targeted to was acidified with 1.0 ml of 50% (volhol) have a standard dry period (45 to 60 d) because H 2 S O 4 and frozen until analysis. Molar per- we did not want the final period of the Latin centages of VFA were determined on all rumi- square to coincide with dramatic physiological nal fluid samples by GLC (Perkin-Elmer Au- changes that occur near calving. Consequently, tosystem, Norwalk, cr) using GP 10% SP- heifers that were approximately 90 d from 120011% H3P04 on 80/100 Chromasorb W calving at the start of the experiment were AW column packing (Supelco, Inc., Bellefonte, chosen as the experimental unit. Depletion of PA) as described previously (14). TG from the liver is slow, probably because of Data were analyzed by ANOVA using the general linear models procedure of SAS (1 1). slow rates of very low density lipoprotein exSources of variation in the model included port. This condition precluded using hepatic square, cow(square), period, treatment, square TG content as a criterion for assessing the x treatment, square x period, and treatment x effectiveness of PG dose because of carry-over period. For testing square effects, the mean effects across periods. The plasma NEFA consquare for cow(square) was used as the error centration is positively correlated with hepatic term. All other sources of variation were tested fatty acid uptake (1) and hepatic TG concentrausing the residual error mean square. Contrasts tion (2) and was considered to be the major were linear effect of PG, quadratic effect of criterion for assessing the effectiveness of PG PG, and 0 versus 296 + 592 + 887 ml of PG. dose. Average DMI of heifers on d 7 and 12 of RESULTS AND DISCUSSION each period are shown in Figure 1. The reducInsufficient resources precluded the use of a tion in DMI between d 7 and 12 was 4096, randomized complete block design, mul- which had been intended. The DMI were simiJournal of Dairy Science Vol. 77, No. 12, 1994
3620
GRUMMER ET AL
TABLE 1. Blood metabolites of Holstein heifers prior to (d 7) and during (d 12) feed restriction and administration of propylene glycol (PG).I d 12
d 7 Glucose? mg/dl Insulin,3 pIU/ml BHBA: mg/dl NEFA: @eq/L
81.5 18.1 10.4 278
SE 2.1 2.1 1.3 19
0 d d of PG
296 d d of PG
592 mVd of PG
887 mVd of PG
75.2 13.0 8.5 746
80.0 17.7 4.8 425
81.1 18.2 3.6 332
82.0 19.8 3.9 282
SE .5 .7 .2 11
IThe values for d 7 correspond to blood sampled 6 h prior to feeding. The values for d 12 are averages for multiple blood samples that were obtained between 6 h prior to feeding and at feeding. Glucose, BHBA, and NEFA were assayed in plasma. and insulin was assayed in serum. 2Linear effect of PG (P < ,001); quadratic effect of PG (P < .Ol); PG versus no PG (P < .OOOI). 3Linear effect of PG (P < .05); PG versus no PG (P < .05). 4Linear effect of PG (P < .Ol); quadratic effect of PG (P < .05); PG versus no PG (P < .01).
lar (P > .15) among treatments on d 12, which was important because we did not want treatment effects to be confounded by variable DMI.No effects of PG occurred on DMI of early lactation cows fed at 3, 6, or 9% of the concentrate (4). Feed intake of nonlactating cows was not decreased until PG intake exceeded 5% of dietary DM (3), which was in excess of the amount we drenched. Plasma and serum metabolite concentrations at 6 h prior to feeding on d 7 and average concentrations for all sampling times on d 12 are in Table 1. Concentrations of glucose, insulin, BHBA, and NEFA at 6 h prior to feeding on d 7 and 12 for heifers not receiving PG were 81.5 and 78.0 mg/dl, 18.1 and 14.2 pIUI ml, 10.4 and 8.4 mg/dl, and 278 and 771 Feq/ L. These changes would be expected with energy restriction. The decrease in BHBA concentration is probably accounted for by a reduction in BHBA production by the portaldrained viscera (6). Provided as an oral drench, PG increased plasma glucose (P < .OOOl) and decreased BHBA and NEFA concentrations (P < .Ol), in agreement with results from previous studies (3, 12) conducted using PG as an oral drench or feed additive for postpartum dairy cows. The decrease in plasma NEFA may have been mediated by an increase in the antilipolytic hormone insulin (Pc .OS). An increase in PG dose caused a linear increase in plasma glucose and serum insulin (P < .001 and P < .05; Figures 2 and 3) and a linear decrease in Journal of Dairy Science Vol. 77, No. 12, 1994
plasma BHBA and NEFA concentrations (P < .01; Figures 4 and 5). There was also a quadratic effect of the increasing PG dose on plasma glucose, BHBA, and NEFA (Figures 2, 4, and 5) that reflected a diminishing response to PG as dose was increased. Time by treatment interactions were observed for serum insulin (P c .OOOl) and plasma NEFA (P < .OOOl) and BHBA (P < .06) concentrations. These interactions reflected a rapid change in plasma metabolite concentrations after dosing PG treated heifers but not control heifers.
"1
0
100
zw
100
.loo
M i n u t e s Postdrench
Figure 2. Effect of oral drench of propylene glycol (---A---),296 (A), 592 (u) or 887 (C)mVd on glucose concentrations in plasma (SE = .5). Treatment x time interaction was not significant (P > .15). Significant contrasts were linear effect of PG (P < ,001). quadratic effect of PG (P < .Ol).and PG versus no PG (P < (pG) of 0
.oaol).
362 1
DOSE RESPONSE TO PROPYLENE GLYCOL 1zw
-
1000-
0
0
1W
2 0
300
400
Minutes Postdrench
Figure 3. Effect of oral drench doses of propylene glycol (pG) of 0 (---A---), 296 (A), 592 (-C-), or 887 (A) d d on serum insulin concentrations (SE = .7). Significant contraSts were treatment x time interaction (P < .oOOl),linear effect of PG (P e .05), and PG versus no PG (P e .05).
1m
ZOO
3w
4.30
Minutes Postdrench
Figure 5. Effect of oral drench doses of propylene glycol (E) of 0 (---A-),296 (4-4. 592 (&), or 887 (L) mVd on plasma BHBA concentrations (SE = .2). Significant contmts were treatment x time interaction (P e .Xi), linear effect of PG (P < .Ol), quadratic effect of FG (P < .05), and PG versus no PG (P e .01).
Relatively little advantage was obtained from increased dose of PG >296 mud. Sauer et al. (12) fed PG as 3, 6, or 9% of concentrate to cows consuming 1 kg of concentrate/4 kg of milk produced (approximately 5 kg/d of concentrate) during the first 8 wk of lactation; PG had minor effects on blood glucose concentrations; NEFA concentrations were reduced when PG was fed as 6% of concentrate, and no additional benefits were observed by increasing the amount to 9% of concentrate. Blood ketones were reduced at all levels of dietary
PG, but only a slight advantage was obtained by increasing PG >3% of concentrate. When PG was fed at 3% of concentrate, it provided approximately 150 mud of PG per cow. An oral drench of 125 ml/d of PG to cows exhibiting a positive milk ketone test did not hasten recovery (10). Use of PG shifted the molar percentages of ruminal VFA (P c .01; Table 2). The molar percentage of isobutyrate appeared to increase; however, PG coelutes from the gas chromatography column with isobutyrate. The most dramatic shifts were linear decreases (P c .OOOl) and quadratic effects (P c .001) in acetate and linear increases (P c .OS)and quadratic effects (P e .Ol) in propionate that were due to in1 creasing PG dose. The shift in ruminal VFA confirms data of Waldo and Schultz (17). Total ruminal VFA concentration was reduced in vivo, and PG was not metabolized during in vitro incubations, leading Emery et al. (3) to conclude that PG is absorbed intact by the gut. Measurements made in vitro were within 24 h of PG administration; therefore, conversion of PG to propionate may occur after more a 1W ZW 300 m prolonged exposure. If PG is not converted to M i n u t e s Postdrench propionate, our results would have to be exFigure. 4. Effect of oral drench doses of propylene plained by a shift in microbial populations 296 (A), 592 (-o-) or 887 toward organisms that produce propionate. Beglycol (PG) of 0 (---A---), (a mVd) on plasma NEFA concentrations (SE = 11). cause of the short duration of PG administraSignificant contrasts were treatment x time interaction (P < .oOOl). linear effect of PG (P c .Ol), quadratic effect of tion during our trial, a shift in microbial popuPG (P e .05), and PG versus no PG (P < .01). lations is not considered to be likely. Journal of Dairy Science Vol. 77, No. 12, 1994
3622
GRUMMER ET AL
TABLE 2. Rumen VFA' (molesl100 mol) and acetate to propionate ratio of Holstein heifers prior to (d 7) and during (d 12) feed restriction and administration of propylene glycol (PG).
d 12 296 d d of PG
592 mUd of PG
887 mYd of PG
d 7
SE
64.4 19.1
1.2 1 .o
69.1 16.9
51 6 33 5
54.0 26.9
49 1 25.4
5 8
3. I 9.5 2.2 I .7 3.4
<. 1 .7
3 .O 7.5 2.3 1.3 4.1
4.2 6.0 2.4 2.2 1.6
9.0 6.2 1.9 2.1 2.0
16.6 5.5 1.8 1.9 2.0
.3 .3 <.l <,l <.l
~
Acetate (AY Propionate (PY Isobutyrate plus PG1.4 Butyrates Isovalerate6 Valerate' A:P*
0 mUd of PG
SE
~
<.I
<.1 <.1
'PG coelutes with isobutyrate. *Linear effect of PG (P < .OOO1); quadratic effect of PG (P < ,001); PG v e m s no PG (P < .OOO1). 3Linear effect of PG (P < .05); quadratic effect of PG (P < .Ol); PG versus no PG (P < .01). 4Linear effect of PG (P < .OOOl); quadratic effect of PG (P < .Ol); PG versus no PG (P < .001). 5Linear effect of PG (P < .05); PG versus no PG (P < .05). 6Linear effect of PG ( P < .Ol); quadratic effect of PG (P < .05); PG versus no PG (P < .01). 7Linear effect of PG (P < .Ol); quadratic effect of PG (P e 0 0 1 ) ; PG versus no PG (P < .001).
CONCLUSIONS
Data from the trial indicate that 296 ml of PG given as an oral drench once daily was almost as effective as 887 ml of PG for reducing plasma NEFA concentrations in heifers that are feed restricted and 1 to 3 mo from calving. Heifers were feed restricted to mimic the feed intake depression that occurs during the final days prior to calving. The concentration of plasma NEFA during feed restriction was similar to that near calving (13, 15). Because plasma NEFA is positively associated with hepatic NEFA uptake and TG concentration, the model employed for this experiment may be suitable for screening feeding strategies or treatments designed to reduce hepatic TG at calving.
REFERENCES 1 Bell. A. W . 1980. Lipid metabolism in the liver and
selected tissues and in the whole body of ruminant animals. Prog. Lipid Res. 18:117. 2Bertics. S. J.. R. R. Grummer, C. Cadorniga-Valino, and E. E. Stoddard. 1992. Effect of prepartum dry matter intake on liver triglyceride concentration and early lactation. J. Dairy Sci. 751914. 3 Emery, R. S., N. Burg, L. D. Brown, and G. N. Blank. Journal of Dairy Science Vol. 77, No. 12. 1994
1964. Detection, occurrence, and prophylactic treatment of borderline ketosis with propylene glycol feeding. J. Dairy Sci. 47:1074. 4 Fisher, L. J., J. D. Erfle, G. A. Lodge, and F. D. Sauer. 1973. Effects of propylene glycol or glycerol supplementation of the diet of dairy cows on feed intake, milk yield and composition, and incidence of ketosis. Can. J. Anim. Sci. 53:289. 5 Grummer, R. R. 1994. Etiology of lipid-related metabolic disorders in periparturient cattle. J. Dairy Sci. 77 :3882. 6 Heitmann, R. N., S. C. Sensenig, C. K. Reynolds, J. Marco Fernandez, and D. J. Dawes. 1986. Changes in energy metabolite and regulatory hormone concentrations and net fluxes across splanchnic and peripheral tissues in fed and progressively fasted ewes. J. Nutr. 116:2516. 7Herdt, T. H.. and R. S. Emery. 1992. Therapy of diseases of ruminant intermediary metabolism. Vet. Clin. North Am. Food Anim. Pract. 8:91. 8 Kleppe, 8 . B., R. J. Aiello, R. R. Gmmmer, and L. E. Armentano. 1988. Triglyceride accumulation and very low density lipoprotein secretion by rat and goat hepatocytes in vitro. J. Dairy Sci. 71:1813. 9 National Research Council. 1989. Nutrient Requirements of Dairy Cattle. 6th rev. ed. Natl. Acad. Sci., Washington. Dc. 10 Ruegsegger. G. J., and L. H. Schultz. 1986. Use of a combination of propylene glycol and niacin for subclinical ketosis. J. Dairy Sci. 69:1411. 1 1 SAS@ User's Guide: Statistics, Version 5 Edition. 1985. SAS Inst., Inc., C q , NC. 12 Sauer. F. D., J. D. Erfle. and L. J. Fisher. 1973. Propylene glycol and glycerol as a feed additive for
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triglyceride and plasma metabolites in dairy cows. J. Dairy Sci. 7qSuppl. 1):289.(Abstr.) 16 Veenhuizen. J. J., J. K. Drackley, M. J. Richard, T P. Sanderson, L. D. Miller, and J. W. Young. 1991. Metabolic changes in blood and liver during development and the treatment of experimental fatty liver and ketosis in cows. J. Dairy Sci. 74:4238. 17 Waldo, D. R., and L. H. Schultz. 1960. Blood and mmen changes following the intra-ruminal administration of glycogenic materials. J . Dairy Sci. 43:496.
Journal of Dairy Science Vol. 77, No. 12, 1994