Effects of Feed Intake and Sodium Bicarbonate on Milk Production and Concentrations of Hormones and Metabolites in Plasma of Cows1

Effects of Feed Intake and Sodium Bicarbonate on Milk Production and Concentrations of Hormones and Metabolites in Plasma of Cows 1 J. L. V I C I N I , 2 W. S. COHICK, ~ and J. H. CLARK 4 Deparment of Animal Sciences University of Illinois Urbana 61801 S. N. McCUTCHEON s and D. E. B A U M A N Department of Animal Science

Cornell University Ithaca, N ¥ 14853 ABSTRACT

intake increased plasma concentrations of somatotropin and nonesterified fatty acids but decreased concentrations of insulin, triidothyronine, thyroxine, glucagon, and prolactin. In contrast, feeding supplemental sodium bicarbonate did not affect concentrations of hormones or metabolites in plasma at either feed intake.

Eight Holstein cows were used to investigate the effects of DM intake and sodium bicarbonate on lactational performance and concentrations of hormones and metabolites in plasma. Cows were fed a diet with or without 1.0% sodium bicarbonate (dry matter basis) in a switchback design. Four cows were fed ad libitum and four cows were fed approximately 80% of their recommended nutrient requirements by restriction of DM intake throughout the three 21-d periods. Supplementing the diet with sodium bicarbonate increased DM intake of cows fed ad libitum. There was a feed intake by sodium bicarbonate interaction for production of 4% FCM. This interaction may be explained by the difference in DM intake of cows fed ad libitum or restricted amounts of feed and supplemented with sodium bicarbonate. Cows fed restricted amounts of feed had lower milk, milk fat, milk protein, milk SNF, and milk energy yields. Restriction of feed

INTRODUCTION

Received October 7, 1987. Accepted December 14, 1987. l Supported in part by the University of Illinois Agricultural Experiment Station, Cornell University Agricultural Experiment Station, and Church and Dwight Company, Inc. 2Monsanto Agricultural Co., BB2K, 700 Chesterfield Village Parkway, St. Louis, MO 63198. 3Department of Animal Science, Cornell University, Ithaca, NY. 4 Reprint requests. SOn leave from Department of Animal Science, Massey University, Palmerston North, New Zealand. 1988J Dairy Sci 71:1232-1238

Clark and Davis (8) indicated that nutritional improvement of milk production by dairy cows could be achieved by optimizing the pattern and amount of nutrients absorbed or by partitioning nutrients toward the support of milk production. Cows fed diets supplemented with sodium bicarbonate (Bicarb) increased feed intake (6, 14, 22) and 4% FCM production (6, 22, 31). Supplementation of diets with Bicarb alters tureen fermentation, improves fiber digestibility, and increases flow of nutrients to the small intestine (9, 11). Little is known about postruminal effects of Bicarb supplementation to the diet of cows. Matteini et al. (25) demonstrated that the intravenous infusion of Bicarb into humans increased concentrations of somatotropin in plasma. The increase in somatotropin concentration occurred earlier in acidotic subjects than in those with normal acid-base equilibrium. If Bicarb induces changes in circulating concentrations of somatotropin in plasma of cows, it may do so by a direct effect, as was observed in humans, or by indirect effects. These indirect effects may include Bicarb induced alterations of acidbase balance, energy balance, and quantity or pattern o f nutrients absorbed from the gastrointestinal tract.

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SODIUM BICARBONATE, ENERGY, AND HORMONES The objective of this experiment was to determine whether feeding Bicarb affected hormone concentrations in plasma of lactating dairy cows fed ad libitum or restricted amounts of DM. Two quantities of DM were fed, because in experiments published previously secretory response of somatotropin to releasing stimuli was greater when animals were fasted (20, 26) or fed limited amounts of feed (3) than when they were fed ad libitum.

M A T E R I A L S A N D METHODS

Eight multiparous lactating Holstein cows (70 + 7 d postpartum; mean + SE) were assigned randomly to experimental treatments in a switchback design. Four cows were fed for ad libitum consumption, and four cows were fed restricted quantities of feed throughout the entire 63 d experiment. Dry matter intakes of cows receiving the restricted feeding regimen were adjusted weekly to provide 80% of each cow's metabolizable energy requirement. Nutrient requirements, as stated by the National Research Council (28), were calculated based on milk production, body weight, and milk fat composition from the previous week. Experimental diets consisted of 50% corn silage and 50% concentrate on a DM basis either with

1233

Bicarb or without (Control) supplemental Bicarb. The Bicarb was provided as 2% of the concentrate mixture (Table 1). For each DM intake, cows were assigned to one of two dietary sequences for the three periods of the experiment: Control-Bicarb-Control, or BicarbControl-Bicarb. Each period was 21 d with the first 7 d used for adaptation to the diet and the remaining 14 d used for collection of data. Feeds were sampled once each week, dried at 55°C, and composited at the end of each 21-d period. Feed intake and orts were recorded daily. Orts were sampled daily and composited by taking a constant percentage of each days refusal for each cow in each period. Samples of feeds and orts were analyzed for crude protein, ash (1), and acid detergent fiber (15). Cows were milked daily at 0500 and 1600 h. Milk samples were taken at each milking during the last 14 d of each period. Milk samples were preserved with potassium dichromate, com o posited by day according to weight, and analyzed for fat, protein (Multispec A, infrared milk analyzer), and SNF (16). On the penultimate day of each period a polyvinyl catheter was inserted into a jugular vein of each cow. Blood samples were taken hourly throughout the last 24 h of each period. Plasma was separated by centrifugation (5000

TABLE 1. Chemical analysis and concentrate composition.

Parameter

Control concentrate

Bicarbonate concentrate

Corn silage

(O/o). Composition Dry matter Ash1 Crude proteinI Acid detergent fiber 1 Ether extract ~

92.2 10.4 23.0 4.8 2.8

91.6 11.6 23.0 5.3 2.5

Ingredient Ground shelled corn Soybean meal Dicalcium phosphate Limestone Sodium sulfate Trace mineral salt Vitamin A and D supplement Sodium bicarbonate

60.45 34.00 1.35 2.41 .74 1.00 .05 ...

58.45 34.00 1.35 2.41 .74 1.00 .05 2.00

43.0 4.4 8.6 24.6 4.3

1Percent of dry matter. Journal of Dairy Science Vol. 71, No. 5, 1988

1234

VICINI ET AL.

× g) and stored at - 2 0 ° C . Alternate hourly samples were assayed for glucose (29) and nonesterified fatty acids (NEFA) (23). All samples were assayed for bovine somatotropin (bST), insulin, and glucagon. Somatotropin was determined (17) using bST for iodination (Miles Lot 12) and reference standards (NIHGH-B18). Insulin was determined (27) using bovine insulin as reference standards and trace. Glucagon was determined by radioimmunoassay (RIA) using an antibody produced and validated in the laboratory of E. N. Bergman, Cornell University, Ithaca, NY. Bovine glucagon (268-25J-120; Eli Lilly Co., Indianapolis, IN) was used for reference standard. Intraassay and interassay CV averaged 13.1 and 21.6%, 10.8 and 13.7%, and 5.2 and 9.1% for bST, insulin, and glucagon assays, respectively. Plasma samples taken at 4-h intervals were assayed for triiodothyronine (T3), thyroxine (T4), and prolactin (PRL). Concentrations of T3 and T4 were determined using solid phase RIA kits (Diagnostic Products Corp., Los Angeles, CA). Intraassay and interassay CV were 4.5 and 4.9% for T3 and 6.4 and 6.7% for T4. Prolactin was determined (5) using ovine PRL as trace and bovine PRL for standards (NIH-PRL-B4, NIADDK). Intraassay and interassay CV were 9.0 and 13.9%. Data from the switchback design were analyzed by General Linear Models procedure of SAS (30). Single degree of freedom comparisons were used to test for main effects of diet (Control vs. Bicarb) and dry matter intake (ad libitum vs. restricted) and their interaction. RESULTS

Cows fed ad libitum throughout the experiment were in positive energy balance (18.5 Mcal ME/d), whereas cows fed restricted amounts of the same diet were in negative energy balance ( - 2 . 8 Mcal ME/d) (Table 2). Because cows fed restricted amounts of DM could not consume more feed, the effect of Bicarb on DM intake was only tested statistically within the cows fed ad libitum. Supplementation of the diet with Bicarb resulted in significantly higher DM intakes when cows were fed ad libitum. Likewise, the calculated energy balance also was increased (15.5 vs. 21.5 Mcal ME/d) when cows were fed ad ]ibitum a diet supplemented with Bicarb. Journal of Dairy Science Vol. 71, No. 5, 1988

Restriction of feed intake significantly decreased production of milk, 4% FCM, SNF, and milk energy (Table 2). When Bicarb was included in the diet, there was no significant difference in milk production or milk composition, but total fat production increased (P<.07) due to small increases (nonsignificant) in milk fat percentage and milk yield. Supplemental Bicarb increased 4% FCM production by 1.3 kg/d when cows were fed ad libitum and reduced 4% FCM by .8 kg/d when cows were fed restricted amounts of DM. Therefore, there was a significant DM intake by Bicarb interaction. Cows fed a restricted amount of DM had increased plasma concentrations of bST and N E F A and decreased plasma concentrations of insulin, gtucagon, PRL, T3, and T4 compared with concentrations in cows fed ad libitum (Table 3). Concentrations of glucose in plasma were not altered by the quantity of DM consumed by the cows. Concentrations of bST, insulin, glucagon, PRL, T3, T4, and glucose in plasma were not affected by supplemental Bicarb in the diet, but N E F A were decreased (P<.10). A DM intake by Bicarb interaction was observed for T4 in plasma. DISCUSSION

Supplementation of diets with Bicarb has increased DM intake of cows in early lactation (14, 22) or at 120 d postpartum (6). However, DM intakes of cows fed Bicarb were not different from controls in other trials (7, 21, 31), and Rogers et al. (31) reported decreased DM intakes of cows fed Bicarb from 9 to 16 wk postpartum. Supplementation with Bicarb increased DM intake of cows fed ad libitum in this study (Table 2). Cows fed restricted amounts of the diet were not allowed to increase voluntary feed intake during Bicarb supplementation. Therefore, the DM intake by Bicarb interaction for production of 4% FCM suggests part of the increased milk production by cows fed ad libitum amounts of DM and supplemented with Bicarb was due to an increase in feed consumption. However, the additional feed consumed resulted in only a slight increase in output of energy in milk resulting in the remaining energy being used for body weight gain [calculated using values

TABLE 2. Feed intake, calculated energy balance, milk production, and composition of milk from cows fed control or sodium bicarbonate (Bicarb)-supplemented diets at ad libitum or restricted dry matter intakes. Significance o f difference (P<)

Treatments Ad tibitum ~ Parameter

Control

Bicarb

Dry matter intake, kg/d ME balance, Mcal/d 4 Milk, kg/d 4% FCM, kg/d Fat, kg/d Protein, kg/d SNF, kg/d Fat, % Protein, % SNF, % Milk energy, Mcal/d s

23.2 15.5 32.4 27.8 .99 1.O3 2.85 3.07 3.18 8.81 20.9

26.0 21.5 32.7 29.1 1.O7 1.O6 2.86 3.27 3.23 8.74 21.7

Restricted Control

Bicarb

SEM

Control vs. Bicarb

Ad libitum vs. restricted

Intake × diet interaction

~0 >

e~

14.3 -2.6 26.7 22.3 .78 .81 2.24 2.97 3.O1 8.35 17.3

13.9 --3.0 24.5 21.5 .78 .72 2.00 3.19 2.90 8.13 15.1

1.2 2.4 1.8 1.3 .05 .07 .16 .15 .09 .08 .75

.052 .042 NS NS .07 NS NS NS NS NS NS

.0001 .0001 .005 .02 .05 .O1 .005 NS .10 .01 .01

NS 3 NS NS .02 NS NS NS NS NS NS NS

© Z -] t~

~3 < > = Q

Refers to quantity o f DM fed to cows. 2Probability of difference tested only within ad libitum fed cows.

© Z

3NS = Not significant (P>.10). 4Calculated from National Research Council (28) where metabolizable energy (ME) balance (Meal/d) = dietary ME (2.8 X kg dry matter intake) minus maintenance requirement (15.11 Meal) minus ME required for 4% FCM production (1.24 X kg FCM). < 0

SCalculated f r o m Tyrrell and Reid (32) where: milk energy (Kcal/kg) = 92.24 (% fat) + 49.14 (% SNF) -- 56.39.

Z

O

00 00

tj l

C

Ox

C

Z7

<

o

TABLE 3. Mean concentrations t o f metabolites and h o r m o n e s in plasma of cows fed control or diets s u p p l e m e n t e d with s o d i u m bicarbonate (Bicarb) at ad libitum and restricted dry m a t t e r intakes.

+

Treatments

Z

Significance o f difference (P<)

O +

00 o0

A d libitum 2 Parameter

Control

Bicarb

Restricted 2 Control

Bicarb

SEM

Control vs. Bicarb

Ad libitum vs. restricted

Intake X diet interaction <

Nonesterified fatty acids, ~eq/L Glucose, mg/dl Somatotropin, ng/ml Insulin, ng/ml Glucagon, pg/ml Prolactin, n g / m l Triiodothyronine, ng/ml Thyroxine, n g / m l

237 66.7 2.3 2.1 303 21.9 1.29 53

223 64.2 2.1 2.2 274 21.8 1.37 58

428 61.2 4.3 1.2 212 7.7

1.10 47

330 57.9 3.7 .8 217 9.7 .89 40

38 3.0 .5 .3 15 1.7 .13 4

.10 NS NS NS NS NS NS NS

.08 NS .005 .03 .03 .01 .07 .01

NS 3 NS NS NS NS NS NS .07

Samples obtained hourly for 24 h. Hourly samples were analyzed for somtotropin, insulin, and glucagon. Alternate hourly samples were analyzed for glucose and nonesterified fatty acids. Prolactin, triiodothyronine, and t h y r o x i n e were measured in samples taken every 4 h. 2 Refers to q u a n t i t y of DM fed to cows. 3NS = Not significant (P>.10).

Z +4 > t-

SODIUM BICARBONATE, ENERGY, AND HORMONES from the National Research Council (28) to be .7 kg/cow/d]. Cows fed ad libitum were in positive energy balance (Table 2) and, using values from the National Research Council (28), were calculated to be gaining an average of 2.2 kg of b o d y weight per cow daily, which is typical for cows in midlactation. Restriction of DM intake reduced milk production (Table 2) and resulted in a negative energy balance and a calculated b o d y weight loss of about .3 kg/ cow/d. Restriction of feed intake altered concentrations of all metabolites and hormones measured in plasma except glucose (Table 3). Concentrations of N E F A and bST in plasma were increased, but concentrations of insulin and T3 were decreased when cows were fed restricted amounts o f feed. These changes are similar to those reported by Cohick et al. (10) when DM intake was restricted to approximately 80% of the cows' nutrient requirement. Restriction of feed intake decreased glucagon, T4, and PRL in plasma during this trial but had no effect on these hormones in a previous trial (10). Cohick et al. (10) restricted feed intake for only 10 d, but DM intake was restricted in this experiment for 21 d in each of three consecutive periods. Furthermore, feed intake by cows fed restricted amounts of feed was decreased each week as milk production declined. Therefore, differences in effects of feed restriction on glucagon, T4, and PRL in plasma may reflect the more chronic feed restriction imposed on cows in this experiment. Other studies also have shown that feed restriction decreased concentrations of T3, T4, and insulin and increased concentrations of somatotropin and N E F A in plasma of ruminants (2, 3, 4, 18), but Gow et al. (18) reported that feed restriction did not affect concentrations of glucagon in plasma of lactating sheep. Previous studies have reported that neither energy status nor milk yield affected concentrations of PRL in plasma of cattle (3, 19, 24). Based on these studies, the differences we observed for the effect of DM intake on PRL may be a chance occurrance related to animal variation. Circulating concentrations of PRL vary widely among lactating cows and in our design cows were assigned to a single DM intake throughout the study. A single intravenous infusion of 12 g of Bicarb over 4 h into children increased plasma

1237

somatotropin concentrations (25). This secretory response occurred earlier in acidotic subjects than in those with normal acid-base balance. However, feeding Bicarb to lactating cows did not alter circulating concentrations of bST in plasma nor of other hormones measured in this study (Table 3). In another study where lactating cows were fed Bicarb, the concentrations of bST in plasma were reduced compared with those of cows fed a control diet (12). Feed intake and output of energy in milk were not reported in that study, so the confounding effects of energy balance could not be evaluated. Chalupa et al. (6) examined the effects of feeding Bicarb and administration o f exogenous bST to lactating cows in positive energy balance. Although both Bicarb and exogenous bST treatments increased milk production (.9 and 3.7 kg/d, respectively), responses were additive, indicating different mechanisms of action. These data agree with our finding that supplemental Bicarb does not increase concentrations of bST in plasma of lactating cows. In many studies, researchers have attempted to relate changes in plasma concentrations of bST or other hormones to dietary factors and attribute milk production responses to changes in hormone concentrations caused by dietary ingredients. When milk production and feed intake are altered, hormonal changes may simply reflect changes in energy balance. For example, in a study where the diet was supplemented with the mineral salt, magnesium oxide, plasma bST was increased (13). However, when the bST concentration was analyzed with DM intake as a covariate, magnesium supplementation had no effect on circulating concentrations of bST in plasma (13). Clearly, it is essential that animals be in comparable energy balance when effects of dietary ingredients on changes in circulating concentrations o f hormones are measured. Our results demonstrate that Bicarb supplementation does not affect circulating concentrations of bST or a number of other hormones and metabolites in lactating cows fed restricted or ad libitum amounts o f dry matter. REFERENCES

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Govt. Printing Office, Washington, DC. 16 Golding, N. S. 1959. A solids-not-fat test for milk using density plastic beads as hydrometers. J. Dairy Sci. 42:899. (Abstr.) 17 Gorewit, R. C. 1981. Pituitary, thyroid and adrenal response to clonidine in dairy cattle. J. Endocrinol. Invest. 4:135. 18 Gow, C. B., G. H. McDonald, and E. F. Annison. 1981. Control of gluconeogenesis in lactating sheep. Aust. J. Biol. Sci. 34:469. 19 Hart, I. C., J. A. Bines, and S. V. Morant. 1979. Endocrine control of energy metabolism in the cow: correlations of hormones and metabolites in high and low yielding cows for stages of lactation. J. Dairy Sci. 62:270. 20 Hertelendy, F., and D. M. Kipnis. 1973. Studies on growth hormone secretion. V. Influence of plasma free fatty acid levels. Endocrinology 92:402. 21 Kilmer, L. H., L. D. Muller, and T. J. Snyder. 1981. Addition of sodium bicarbonate to rations of postpartum dairy cows: Physiological and metabolic effects. J. Dairy Sci. 64:2357. 22 Kilmer, L. H., L. D. Muller, and P. J. Wangsness. 1980. Addition of sodium bicarbonate to rations of pre- and postpartum dairy cows. J. Dairy Sci. 63:2026. 23 Ko, H., and M.E. Royer. 1967. A submicrometer assay for nonpolar acids in plasma and depot fat. Anal. Biochem. 20:205. 24 Koprowski, J. A., and H. A. Tucker. 1973. Serum prolactin during various physiological states and its relationship to milk production in the bovine. Endocrinology 92:1480. 25 Matteini, M., G. Cotrozzi, and G. Cappelli. 1976. Human growth hormone secretion induced by sodium bicarbonate infusion. Acta Med. Auxol. 8:49. 26 McAtee, J. W., and A. Trenkle. 1971. Effect of feeding, fasting, and infusion of energy substrates on plasma growth hormone levels in cattle. J. Anim. Sci. 33:612. 27 McCann, J. P. 1980. The effect of an 8-day starvation period upon the metabolic and reproductive endocrinology of cyclic Holstein heifers. M. S. Thesis, Cornell Univ., Ithaca, NY. 28 National Research Council. 1978. Nutrient requirements for dairy cattle. Natl. Acad. Sci., Washington, DC. 29 Raabo, E., and T. C. Terkildsen. 1960. On the enzymatic determination of blood glucose. Scand. J. Clin. Lab. Invest. 12:402. 30 Ray, A. A. 1982. SAS User's guide: statistics. SAS Inst., Inc. Cary, NC. 31 Rogers, J. A., L. D. Muller, C. L. Davis, W. Chalupa, D. S. Kronfeld, L. F. Karcher, and K. R. Cummings. 1985. Response of dairy cows to sodium bicarbonate and limestone in early lactation. J. Dairy Sci. 68:646. 32 Tyrrell, H. F., and J. T. Reid. 1965. Prediction of the energy value of cow's milk. J. Dairy Sci. 48:803. (Abstr.)