Some Aspects of Calcium Metabolism in the Dairy Cow

Res. vet. Sci., 1962, 3, 470

Some Aspects of Calcium Metabolism in the Dairy Cow E. W.

MOODIE AND

A.

ROBERTSON

Department of Veterinary Hygiene and Preventive Medicine, Royal (Dick) School of Veterinary Studies, Edinburgh SUMMARY. Observations have been made on some biochemical and physiological changes in 4 young and 4 oldcows during the parturient period. Serum calcium and whole blood inorganic phosphate and citric acid fell, while whole blood lactic and pyruvic acids and glucose rose at parturition. Food intake, faecal output, rumen sounds as determined by auscultation, and the frequency and strength of rumen movements were reduced at calving. Six cows were excited for periods of 5 to IO minutes; the only changes observed in the various constituents of the blood were increases in lactic and pyruvic acids. Alimentary stasis induced in 2 dry cows and 3 milking cows by hyoscine hydrobromide injections was accompanied by a reduction in the serum calcium in the milking cows, whole blood inorganic phosphate in 4 cows, and citric acid in all cows. Two cows were infused with sodium oxalate solution to study the effect of lowered serum calcium on alimentary activity but this remained unchanged. The relationship between the biochemical and physiological changes and their bearing 011 the etiology of bovine hypocalcaemia are discussed in the light of these findings. IN PREVIOUS PUBLICATIONS (Robertson, Paver, Barden & Marr, 1960; Moodie, 1960; Moodie & Robertson, 1961) evidence was produced in support of the suggestion that the heavy

milking cow, particularly around peak lactation, is dependent not only on the release of calcium from bone but also on the continuous uptake of calcium from the alimentary canal to maintain her calcium equilibrium. Impairment of absorption of calcium from the digestive tract, associated possibly with bowel stasis was, therefore, suggested as an important factor in the etiology of naturally-occurring parturient hypocalcaemia. It would provide corroboration of this view if there was evidence of reduced absorption of calcium during the critical period of onset of lactation. The variable nature of the animal's appetite about the time of calving precludes the use of conventional balance experiments as a means of determining the quantities of calcium absorbed on an hourly or even on a daily basis, and the prolonged half-life of radio calcium 4sCa would tend to mar its usefulness in comparing the absorption of calcium on consecutive days in the same animal. There seems to be, therefore, no reliable method of evaluating calcium uptake from the gut on a short-term basis. However, it is possiblethat where digestive tract activity is reduced, movement of nutrients to portions of the alimentary canal favourable for absorption may be suboptimal. Ruminal activity and rate of passage of faeces have been used as measures of such activity in this work, but a direct measure of intestinal activity was not possible. Hyoscine hydrobromide was used to determine the effect of bowel stasis on serum calcium, while sodium oxalate given intravenously was used to find the effect of hypocalcaemia on the activity of the alimentary tract. At the same time, the opportunity was taken to study the inter-relations of serum calcium, whole blood inorganic phosphate, glucose, citric acid, lactic acid, pyruvic acid, food intake, ruminal activity and faecal output.

470

Ca Metabolism in the Dairy Cow

471

MATERIALS AND METIIODS

Animals The 4 young and 4 old animals (one of which developed milk fever) used for the parturition studies were among those described in a previous paper (Moodie & Robertson, 1961) and the other animals used were drawn from the same herd. The food offered and the estimation of food intake were also as described previously.

Collection of Faeces Faeces was collected at frequent intervals as it was voided during the day. Each day's output was bulked, mixed and an aliquot taken and dried at 100°C. to constant weight. Little was washed away by urine, and although some contamination occurred this would not affect the dry matter faecal output significantly.

Blood Sampling Blood was collected into heparinised bottles from either the jugular or mammary vein, the latter being used whenever possible. In experiments involving lactic and pyruvic acid estimations, a portion of the sample was immediately precipitated in freshly prepared icecold 10 per cent w/v trichloroacetic acid. This preparation was kept chilled until all estimations were completed and was used for the determination of inorganic phosphate and citric, lactic and pyruvic acids in whole blood. Samples required for glucose estimation were collected in heparinised bottles containing o- 3 mg. sodium iodoacetate per mi. blood.

Chemical Estimations

\

Serum calcium and inorganic phosphate in whole blood were estimated by the methods already described (Moodie & Robertson, 1961). Blood glucose was determined by the method of Somogyi (1952) within a few hours of collection, and citric, lactic and pyruvic acids by the techniques of McArdle (1955), Barker & Summerson (1941) and Friedemann & Haugen (1943) respectively,

Rumen Activity Rumen activity was recorded over periods of 10 to IS minutes and the movements classified as primary or secondary according to the method described by Alexander & Moodie (1960). The animals were prevented from eating during the recording periods but no attempt was made to discourage rumination. Activity was also estimated by auscultation in the left para-lumbar fossa and the sounds evaluated according to the following scoring system:o. No sounds. J. Background sounds similar to those produced by cutaneous twitching. 2. Continuous background sounds occasionally interspersed with sounds like •peals of thunder' which were usually associated with eructation. 3. Frequent 'thunder' sounds associated with most but not all of the rumen contractions. 4. Almost continuous 'thunder' sounds. .

Where doubt existed in classifying a case, an intermediary score was given.

47 2

E. W. Moodie and A. Robertson RESULTS

(a) Calving Cows Table I gives the average results obtained from the calving cows. The food intakes, milk yields, serum calcium and inorganic phosphate in whole blood were as described in the previous paper (Moodie & Robertson, 1961). Citric acid fell from over 4 mg. per cent before calving to I· 5 mg. per cent 16 hours after calving and thereafter rose to values of the order of 2· 5 mg. per cent 3 to 7 days post partum. Partition of the data for young and old cows revealed no differences between the changes in the citric acid fraction in the 2 groups. Glucose, pyruvic and lactic acids all tended to rise about the time of calving. Blood glucose rose from 50.7 mg. per cent 4 days before calving to a peak of 74.2 mg. per cent at calving; within 8 hours of calving the values had returned to precalving levels and thereafter continued to fall steadily to a mean of 30·2 mg. per cent 14 days after calving. Prepartum values of 0·8 and 3·6 mg. per cent were found for pyruvic and lactic acidsrespectively, and these increased to 1·1 and 6·3 mg. per cent at calving and returned to precalving values within a day. Rumen sound scores showed a marked drop from a prepartum mean value of 2· 8 to a mean of o· 8 shortly after parturition. Recovery to values above 2, which may be regarded as fairly normal, took about I day, but maximum scores were not recorded until 4 days after calving. There were no apparent differences between young and old cows. Total rumen movements were recorded on 5 normal cows and showed no change in frequency; there was, however, a reduction in primary movements at calving from 12 to 7·8 movements/to minutes. Faecaloutput data obtained from 3 young cows showed a marked fall in dry matter excreted on the day of calving. Although the reduction in frequency of the primary rumen movements was not great, there was marked evidence of weakening of these waves compared with the secondary movements in 3 of the 5 animals examined. Typical findings are illustrated in Figures I, 2 and 3 which show tracings from cows at their first, second and fifth calvings respectively. Figure I shows a very marked reduction in ruminal activity at calving, both in the frequency of the primary waves and in their strength compared with the secondary waves. This effect was not quite so marked in the cow recorded at her fifth calving (Figure 3) and no change could 1Jedetected at any time in the cow at her second calving (Figure 2). Regardless of the changes in rumen movement, the rumen sounds always disappeared at the time of calving and in some animals even the sound of eructation was inaudible on auscultation at the paralumbar fossa. (b) Effect ofExcitement and Exercise Six cows were stimulated for a period of 5 to 10 minutes by varying combinations of being chased round a yard, unusual noisesand pricking of the hindquarters, in order to assess the extent to which the observed changes in calving cows might have been associatedwith excitement and moderate physical exertion. The results are shown in Table II. No effect was observed on serum calcium or inorganic phosphate, citric acid or glucose. The mean concentration of lactic acid, however, increased to 3 times its original value while that of pyruvic acid doubled, the magnitude of these changes apparently being dependent on the degree of muscular activity. This is reflected in the significant increases in their standard deviations. For example, 4 cows which were exercisedin addition to other stimulation showed

TABLE I

Food intake kg. D,M·/day Faecal output kg. D.M·/day Milk yield kg./day

mins,

Serum calcium mg./lOO ml, Whole blood inorg. P, mg.] 100 ml. Whole blood citric acid mg.lux: ml. Whole blood glucose mg./loo ml. Whole blood pyruvic acid mg./loo ml. Whole blood lactic acid mg./loo m!. Rumen sounds score Total rumen movementsj ro mins, Primary rumen rnovementsj ro mins. Secondary rutnen m?v~tnentslI0

4

3

2

I

Before 0

1

i

I

Days from Calving I!

2

3

After 4

7

14

Mean

4'1 56'0 0·8 3'3

4'3 52'5 0'8 3'6

4'5

50'7

0·8

8

5

5

8'4

3'3

3 8

-

-

3'3

7'2

5

8 3'I

7'3

7.6

12'0

5

-

II '0

13'0

19'2

5

8'0

18'3

20·6

2·8

8

8'1

2·8

2·8

3'6

4

5'4

5.6

5'7

8

10'2

10'3

9'9

6'4 1'9 12·8

2,8 -

7.6

7"8

15'5

1'0

6'3

1'1

74'2

II '2

10·8

2'7 13'3

-

-

8'0

-

-

7'1

7"6

6'4

12'5

18'2

18'3

18,8

2'4

1'2

0,8

3'3

3"3 16'1

8'7

-

8'7

II'5

20'2

2'1

8'6

II'8

20'4

2'2

2'9

2,8

3'4 15.8

9'4

7'4

10'9

18'4

2'1

2'7

0,8

0,8

0·8

0,8

2'6

4'4

9'3

37'1

2'2

4'1

8'8

39'3

42'4

1·8

4'1

8'8

46'1

3'4

1'0

55'1

1'7

4'1

8·6

4·6

0'9

54'3

1'5

1,8

2·8

-

8'3 3'9

4'3

8'7

3'3

8'9

7'5

7'7

12'3

20'0

2'2

3'7

0·8

61'2

4'1

4'7

9'5

3'3 17'4

9'2

7'9

13'I

3'9 17,6

10'5

7'4

II·6

19'0

2·6

2,8 21'0

4'1

0'9

34'2

2'5

4'4

9'5

3'1

0'9

37'2

2'5

4'3

9.6

19'1 II'5 7'6

-

-

-

3'I 15'8

8'3

2'1

-

-

3·6

0'9

47"9

2·8

4'4

9'3

3'3

1'0

30'2

2'9

4'1

9'5

- - - - - -- -- - - - - - - - - - - - - - - - - - --- - - -

8

No. of Cows

0'22 0,8

0'48

0'66

0'29

1'13

0'27

0'57

0'13

3'0

0'33

0'3 1

0'29

S.E.

P,
P,
N,S.

P,
N.S.

P,
P,<0'05

N,S,

P.
P,
P.
P.
Signif. of difference between days

CHANGES IN VARIOUS BLOOD CoNSTITUENTS AND IN RUMEN MOVEMENTS. FOOD CONSUMPTION. FAECAL ExCRETION OF COWS BEFORE AND AFTER CALVING. AND THEIR MILK YIELD

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E. W. Moodie and A. Robertson

474

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S

P? tmin.

FIG. I. Rumen movements recorded from the left paralumbar fossa of a cow at her first calving, A Normal Tracing. Movements 18/10 min. Sounds Score 3. Heifer very restless. B Seven hours pre-calving. Movements 18/10 min. Sounds Score o. Primary waves weakening. C Calving. Movements 9/10 min. Sounds Score 1'0. Primary waves very weak. D Eight hours "after calving. Movements 14/10 min. Sounds score 1'0. P Primary waves S Secondary waves

three to fourfold increasesin lactic acid. of the 2 stimulated by pricking only, I showed marked muscular tremors and the lactic acid rose from 3' 3 to 6· I mg. per cent, while the other showed no tremors and no increase in lactic or pyruvic acids.

Ca Metabolism in the Dairy Cow

475

fmin

FIG. 2. Rumen movements recorded from the left paralumbar fossa of a cow at her second calving. A Normal Tracing. Movements 22/10 min. Sounds score 3.0. 13 Half hour after calving. Movements 17/10 min. Sounds score O. P Primary waves S Secondary waves I min.

fllin

p

S

Straining

S

p

S

FIG. 3. Rumen movements recorded from the left paralumbar fossa of a cow at her fifth calving. A Normal tracing. Movements 17/10 min. Sounds score 3'0. 13 Twenty hours pre-calving. Movements 18/10 min. Sounds score 1'5. Primary waves reduced in height. C Half hour after calving. Movements 12/10 min. Sounds score 1'5. Primary waves small, D Eight hours after calving. Movements 16/10 min. Sounds score 2'0. P Primary waves S Secondary waves

E. W. Moodie andA. Robertson TABLE II EFFECT OF ExCITEMENT ON TIlE BLOOD CONSTITUENTS OF SIX COWS

Before

Serum calcium (mg./loo mI.) Whole blood inorganic phosphate (mg.jroo mI.) citric acid (mg.jroo mI.) " glucose (mg.jroo mI.) " " " lactic acid [mg.jroo mI.) " pyruvic acid [mg.jroo mI.) "

"

"

After

Mean

S.D.

Mean

S.D.

10·43

± 0·69

10·52

± 0·54

5.39 2·95 47.2 3.27 0.77

± 0.65 ± 0·54 ± 5·68 ± 0.61 ± 0.06

5·32 2.81 46.8 9·18 1.40

± 0.42± 0.46 ± 7. 17 ± 3·45* ± 0·48t

Variance Ratios *F=3I.8 Sig. at 1% tF=64 Sig. at 1%

(c) Effect ofHyoscine Hydrobromide Five cows were injected subcutaneously with hyoscine hydrobromide, B.P., the aim being to inhibit peristalsis for a period of at least 16 hours. Particulars of animals and doses used are given in Table III. In all animals the initial dose of the drug produced mild bloating which lasted for 2 to 3 hours; this was not observed with the succeeding maintenance injections. During the initial period all rumen movements and sounds were inhibited, but the bloating diminished as the secondary movements returned to normal. (For a typical recording see Alexander & Moodie, 1960). Salivation was also inhibited, but despite this the animals attempted to eat as soon as the more severe effects of the drug had worn off and before the return of ruminal activity or salivation to normal. Faecal excretion was completely inhibited in 4 of the cows for periods of 16-24 hours but 1 cow (BSI) developed diarrhoea which persisted for 24 hours; data for faecal excretion were not obtained for this animal. The oldest cow (Pn) developed a milk. fever-like syndrome which was noticeable as fine muscular tremors 12 hours after the initial injection; four hours later she was unable to rise and showed TABLE III PARTICULARS OF Cows USED FOR HYOSCINE INJECTION EXPERIMENTS

Hyoscine hydrobromide Cow No.

Age (years)

Time after calving

Milk yield

kg.rday

Initial dose

Maintenance doses 50 mg. after 12 hours 50 mg. after 12 hours 100 mg. after 8 hours 50 mg. after 12 hours 50 mg. after 10 hours Nil

3 5 4

Barren 10 months 8 days

Nil Nil 15

150 mg. 150 mg. 200 mg.

B 51

7

PII

II

41 mths. 31 mths.

14·5 21.5

150 mg. 150 mg.

F4 D 19 E 14

Ca Metabolism in the Dairy Cow

477

signs typical of milk fever. This cow was treated with 3S0 mi. of 2S per cent calcium boragluconate solution given intravenously and responded uneventfully in about 4 hours. Table IV gives the data for 3 groups of cows used in these experiments, namely, young non-lactating, young lactating and old lactating. The average results obtained from the S cows used are shown in Figure 4a, while Figure 4b gives the data for Cow PlI. Food intakes, faecal excretions and milk yields are given on a za-hour basis(7 a.m, to 7 a.m.). Experiments were started at 10 a.m, on the second day and blood samples were taken and recordings of rumen movements and sounds were made at 4,8,12,18,24,30,36,48 and 72 hours after the start of the experiment. The average food intake dropped by about 30 per cent on the day of injection and took 3 days to return to normal; Cow EI4, however, recovered sufficiently to eat her entire ration within the za-hour sampling period following the injection despite being completely unable to eat for a considerable part of that day. Daily dietary calcium and phosphate intakes were also estimated, but were found to follow the pattern of the food intake and are not shown. Faecal output fell on the day of injection to between one third and one half of the previous day's output in the 4 cows recorded. Milk yield dropped only IS per cent in the cow on her second lactation (EI4) but fell SO per cent in BSI and 87 per cent in PIr. Rumen sounds and rumen movements followed similar courses. In the 3 younger cows movements stopped temporarily after the initial injection but returned to normal within a few hours. In the old Cows BSI and PlI the rumen activity remained depressed for up to 24 hours and the drug appeared to have a much more marked effect on these 2 animals. Rumen sounds were similar in all animals, taking 36 hours to recover their pre-injection scores. Blood citric acid showed on av:erage a very marked fall following the injections, remained low for 36 hours and then gradually increased to normal values in about 3 days. The changes in citric acid were greatest in those cows with high initial values. Inorganic phosphate was somewhat variable with reductions of up to So per cent being recorded. The serum calcium did not change markedly except in the 2 old lactating cows, B5I dropping to 7' S mg. per cent for over a day while PI I was treated with calcium borogluconate after the serum calcium had fallen to 4'9 mg. per cent and symptoms of hypocalcaemia had developed. Serum magnesium values on 3 of thesecows were normal, showing no change or a slight increase (B5I).

(d) Effect of Sodium Oxalate Two cows were given sodium oxalate by intravenous drip to study the effect of lowered serum calcium on ruminal activity. Cow B52 (dry and barren) received 16 g. sodium oxalate as a 2 per cent solution evenly over a period of 60 minutes while cow EI6, (dry-7 months pregnant) died after 19 g. sodium oxalate had been administered in S5 minutes. There was no evidence of alteration of the ruminal activity outside the normal range in either cow as a result of the injection (Table V); the values for calcium and magnesium in serum, and for inorganic phosphate and citric acid in whole blood are also shown in Table V. DISCUSSION

In the previous paper (Moodie & Robertson, 1961) the loss of appetite in calving cows was discussed. The reduced faecal excretion.reported here is in general agreement with those

IV

2 I 2 2 I 2

Young, non-lactating Young, lactating Old, lactating Young, non-lactating Young, lactating Old, lactating Young, non-lactating Young, lactating Old, lactating Young, non-lactating Young, lactating Old, lactating Young, non-lactating Young, lactating Old, lactating Young, non-lactating Young, lactating Old, lactating Young, lactating Old, lactating

Whole, blood inorg. phosphate mg./lOo ml,

Whole blood citric acid mg,/IOO ml.

Rumen sounds score

Total rumen movemenrs/ro mins,

Food intake kg,D,M,/day

Faecal output kg,D,M./day

Milk yield kg,/day

a

4

8

12

18

24

30

Hours from Initial Treatment 48

10'3 8'5 8'2

36

10·6 9'1 7'9

72

(After)

9'0 10'3

10'5

9'9 8'1 8'0

9'9

7'2

8'5

rO'I 8'7 6'4

10'2 9'2 6'3* 8'4

8'5

10'0

10'4 8·8 8'3

9,6

-

10'5

2,6 2'9 2·8

2'5

2'9 2'9

2'9 2'4 3'4

2'7 2'5 3'2

2'9 2'3

2'9 2'4 3'0

3,6 2'7 4'1

2'9 2,6 3.8

2·6 3'8

2'5

2'9 2,6 3'4

3'0 3'3

2'5

2'7 2'7 3'I

5'3 5'2

4,6

3,8 3'8 4'2

4'2 2,8 4'4

3'5

3'9 4'7 4'2

4'8

5'3

4'8

4'6

5,6

4'4

4'5

4,6 4.6

4'6 4·6 4'5

4'2 2,6

3'6 1'4

2'5 1'2

2'1 1'3

1'7 1'0

2'1 1'0

2'0 0'9

2'2 1'0

2'9 1'5

3,8 2·6

0'3 0'0 0'0

0'3

0'5

0'0

0'0

0'5

0'5

0·8

0'5 0'5

2'3

0'5

1'5

1'5 1'3

2'3 2'0 2'5

2'0 2'0 2'3

1·8 2'0 3'0

3'0 0'0

9'3

4'4 9'5

-y

8'5

22'0

0'5

7'0

13'51 II'S 6'0 20'0

J l

17'0 12'5

20'0 20'0

5'4 8'1 6'3

y-_--.J

17'5

22'0

6'9 8·6 9'5

21'0 IS'S

12'9

8'1

---

22'0 20'0

1'0 1'3 1'4

2'5

1'7 2'7

3'0 3'3 5'2

5'9

2'3

15'0 18'1

12'7 5'3

15'9 5'3

9'1

15'9

15'9 II'3

--- - - - - - - --- - - - --- --- - - - - - - --- ---

2'7 3'4 4'4

- - - --- --- --- - - - --- --- - - - --- - - - - - -

8'4 8'9 14'3

18'5 \

22'0

18'0

23'5

--- - - - --- ------ --- - - - --- - - - ----20'0 18'0 18'0 19'0 16'0 20'0 I' 5 3'0 17'5

2'0 2,8

2'3 2'0 2,8

- - --- - - - ------- - - - --- --- --- --- - 0,8 1,8

4'1 2·8

--- --- --- --- --- --- --- - - - ---2'5- --0·8 2'2 '1'9 1'1 1'0 2'0 0'7 0'9 0'7 0'7

5'4

5'2

4'3

--- --- --- --- --- - - - --- --- --- - - - - - -

2'3 2,8 2'9

- - - --- --- --- --- --- --- - - - --- - - - ---

10'3 9'9 10'6

--- --- - - - --- - - - --- - - - --- --- - - - ---

24

(Before)

tYoung, non-lactating-Cows F4 and D9, Young, lactating-Cow EI4, Old, lactating-Cows B 5I and PI1. *350 ml, 25% w]» calcium borogluconate given intravenously to Cow PII immediately after this sample,

I 2

2 I I

2 I 2

2 I 2

2 I 2

I I I

Young, non-lactating Young, lactating Old, lactating

Serum magnesium mg,/Ioo ml.

2 I 2

Young, non-lactating Young, lactating Old, lactating

No. of Cows

Serum calcium mg./Ioo ml.

Group of cows]'

CHANGES IN THE VARIOUS BLOOD CONSTITUENTS, AND IN RUMEN MOVEMENTS, FOOD CONSUMPTION, FAECAL EXCRETION AND MILK YIELD OF COWS INJECTED WITH HYOSCINE HYDROBROMIDE

TABLE

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l:l..

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Ca Metabolism in the Dairy Cow 11

479

11

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7

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o ~--~-....~--..._--..__-_lo a: 2 3 INJECTION

20

20

o

o 1 2 DAYS FROM INJECTION

3

(b) COW P II, aged II years

(a) Means of five cows FIG.

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o

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4. The Effect of Subcutaneous Hyoscine Hydrobromide on the Blood Composition and Alimentary Activity of cows. Ca-350 ml, 25 per cent wJv calcium borogluconategiven intravenously.

I

FEED

INTAKE

FAECAL

OUTPUT

o

MILK YIELD

E. W. Moodie and A. Robertson

observations, and also with those of Ward, Blosser and Adams (1953) based on 16 normal calving cows and 3 cows which developed milk fever. The changes in the blood constituents of the calving cows in these experiments are similar to those previously recorded for cows at normal parturition and with milk fever (Blosser & Smith, 1950; Ward, Blosser, Adams & Crilly, 1953) and for starved cows (Robertson et al., 1960). In order to test the hypothesis of Moodie (1960) that an interruption in the absorption of calcium from the alimentary canal could induce hypocalcaemia in older heavily milking cows, 5 cows in different physiological states were injected with hyoscine hydrobromide to induce alimentary stasis. The results show that marked changes in serum calcium occurred in the 2 older cows which were milking heavily, and that these changes occurred with a rapidity comparable to that observed in normal calving cows and in cows developing milk fever (Moodie, Marr & Robertson, 1955; Marr, Moodie & Robertson, 1955). Serum magnesium remained unaltered or was lightly elevated and blood phosphate decreased. Citric acid levels behaved similarly to those reported by Blosser and Smith (1950) for normal and milk-fever cows. EFFECT OF SODIUM OXALATE GIVEN

Serum calcium (mg.noo

BY

TABLE V INTRAVENOUS DRIP TO Two Cows ON VARIOUS CONSTITUENTS OFTHEIR BLOOD AND ON RUMENACTIVITY

ml.)

Serum magnesium (mg.noo

ml.)

Cow No.

Before injection

After half injection

Bp E 16

10.8 10.2

8.6 8·7

6.2 2·75

End of injection

B 52 E 16

2·70 2·50

2·70 2.5 0

2·55 2·50

Bp E 16

2.82 3·81

2.88 3·97

2·75 3·63

B 52 E 16

1.95 2·95

2.14 2·95

3·60

Rumen sounds score

Bp E 16

2.0 2·5

2.0 2·5

2.0 2·5*

Total rumen movements/ro min.

B 52 E 16

18 22

14 18

15 16*

Whole blood inorganic phosphate [mg.noo

Whole blood citric acid (mg./Ioo

ml.)

ml.)

2·37

* Five minutes before end of injection

Bp received 16 g. sodium oxalate as 2. per cent solution in 60 minutes.

E16 received 19 g. sodium oxalate as 2. per cent solution in 55 minutes.

Food intake and faecal output were also decreased in hyoscine-injected cows. It is of interest to note that the changes in milk yield were parallel to those of the serum calcium; thus Cow EI4 showed little change in either, Cow BSI showed a moderate fall in both, while the milk yield of Cow PI I, which developed the 'milk fever' syndrome, dropped from

Ca Metabolism in the Dairy Cow zr-o lirres per day before the experiment to 3'0 litres on the day of paresis. Prior to the development of symptoms only I' 1 litres of milk, probably containing lessthan 2 g. of calcium, had been withdrawn, thus indicating a negligible ability to mobilise calcium from the skeletal reserves. The effect of lowered serum calcium levels on alimentary activity was examined in 2 cows where sodium oxalate was given by intravenous drip. As a result there was no evidence of slowing or weakening of rumen activity or decrease in rumen sounds. Thus the reduction in alimentary activity observed in normal calving cows is probably not primarily due to hypocalcaemia, especially when the loss of appetite precedes the hypocalcaemia (Moodie & Robertson, 1961), although Hallgren, Carlstrom & Jonsson (1959) have reported some alimentary dysfunction in 2 out of 4 cows when sodium oxalate was administered for periods of several hours. These workers did not observe any gastro-intestinal dysfunction in the cows rapidly infused with oxalate in doses comparable to those given here. Thus it is possible that hypocalcaemia affects gastro-intestinal activity only where it persists for several hours; such a view would not be incompatible with the well-known effect of calcium injections being associated with evacuation of the bowel in cases of milk fever, nor with the occasional observations of hypocalcaemia in clinically healthy cows. The high values of lactic and pyruvic acids and low values of citric acid in normal cows at calving and in cases of milk fever led Ward et al., (1953) to suggest that some of the oxidative decarboxylation processes of Kreb's cycle may be impaired. If this were so, one would expect an increase in pyruvic and lactic acids, which in these experiments appear to be in equilibrium, to coincide with a fall in citric acid. Inspection of the data for calving cows presented here shows a to-hour difference in the maximum changes in pyruvic and lactic acids, and citric acid; the character of the changes is different, the first 2 being transient while the last is prolonged, and at one stage lactic pyruvic and citric acids are falling rapidly and simultaneously. These observations suggest there is no serious impairment of the Kreb's cycle in calving cows. In view of the results shown in Table II, the changes in lactic and pyruvic acids could be accounted for by the uterine and abdominal muscular activity, coupled with excitement, which occurs during parturition. Likewise, excitement might account for some of the corresponding changes observed in milk fever cases and in starved cows developing milk fever. There is a marked similarity between the changes in serum calcium and those in blood citric acid in parturient cows, both constituents reaching their lowest values at the same time and remaining depressed after calving. This type of relationship has previously been reported (Blosser & Smith, 1950) but it does not always hold good, for in the cows injected with hyoscine, 3 showed marked reduction in citric acid without any accompanying change in serum calcium. Nor was it observed when serum calcium was reduced to tetanic levels by the administration of sodium oxalate. Thus our results suggest that there is little direct association between the levels of circulating citric acid and calcium. This view is supported by the variability in citric acid which may be observed in individual cows with normal serum calcium values. It does not corroborate the conclusions of other workers (Chang & Freeman, 1950; Freeman & Chang, 1950a, 1950b) who, however, have based their opinions on experiments in dogs in which the circulating citric acid levels were increased far. beyond their normal physiological range. It may be that the citric acid changes obtained at parturition are associated in some way

E. W. Moodie and A. Robertson with the variations in the alimentary activity of the cows. Thus in the cows injected with hyoscine the lowest citric acid occurred from 12-36 hours after the initial dose, while in the calving cows the lowest mean values occurred from 8 to 36 hours after the period of minimum alimentary activity. There is no particular reason to attribute the reduction in alimentary activity to the fall in citric acid particularly in view of the time lag, but this aspect obviously warrants more critical investigation. At first sight the changes in glucose and inorganic phosphate in the calving cows (Table I) seem to vary inversely especially when allowance is made for the possible effect of milk secretion in lowering their levels after calving. Both constituents started to alter a few days before calving and their maximum changes were observed at calving. However, inspection of the data from individual cows shows that this relationship existed only until about 8-16 hours post-partlltn and that thereafter blood inorganic phosphate and glucose tended to alter in a similar fashion. In the preceding paper (Moodie & Robertson, 1961) it was not possible to demonstrate any close relationship between the quantity of food eaten and the inorganic phosphate in whole blood before calving, and similarly in the experiments described above no correlation has been found between the quantity of food eaten and the blood glucose before calving. However, it should not be overlooked that Robertson et al., (1960) demonstrated an increase in blood glucose in starved cows, while alimentary inactivity as a result of hyoscine injection was associated with a rapid fall in blood phosphate. It may be that neither food consumption on a daily basis nor ruminal activity is a reliable measure of intestinal activity (Alexander & Moodie, 1960) and faecal output is probably a better measure to adopt. Thus the possibility of changes in blood glucose and phosphate being associated with changes in alimentary activity, which in turn may be due to hormonal influences,cannot be excluded. Both Le Bars, Nitescu & Simonnet (1953) and Vallenas (1956) have recorded evidence of high blood glucose levels associated with reduction in the frequency and amplitude of rumen contractions. The loss of rumen sounds as parturition became imminent was a consistent feature of all cows examined although the rumen movements recorded were quite normal in some cows and only partially inhibited in others, while there were no changesin the secondary movements which are predominantly associated with eructation (Stevens & Sellers, 1959). In the hyoscine-injected cows there was an initial complete loss of rumen activity associated with low sounds scores, but this was followed by a period of ruminal activity accompanied by eating in some caseswithout any marked improvement in sound. It is difficult to offer an adequate explanation for this discrepancy between the rumen movments and sounds but it is possible that this is associated with changes in the 'degree of fill' of the rumen. A crude estimate of changes in the total solidscontained within the alimentary canal can be obtained by comparing the daily faecal dry matter with that of the food eaten. Tables VI and VII show that the ratio of faecal output to food intake dropped by about 40 per cent on the day of parturition in 3 normal calving cows and also in 4 cows injected with hyoscine, and it is unlikely that a change of this magnitude would be due solely to an increase in the digestibility of the food. The values of these ratios are positively correlated with the rumen sounds score (N = 48, r = +0·459 P = 0·01) thus supporting the possibility that in certain circumstances the rumen sounds score is influenced by the 'degree of fill' of the rumen. Moodie (1960) pointed out that the hypocalcaemia of parturition and milk fever could be explained by the sudden onset of calcium secretion in the milk accompanied by a deficiency

Ca Metabolism in the Dairy Cow

in the availability of calcium from the bones and an interruption in the absorption of calcium from the alimentary canal. This paper presents evidence in support of such a view, viz:(I) There are signs of reduced alimentary activity at parturition, e.g. loss of appetite, reduced faecal output, reduction in primary rumen movements and loss of rumen sounds. TABLE VI RATIO BETWEEN DRY MATTER EXCRETED IN THE FAECES AND THE DRY MATTER OF THE FOOD CONSUMED DURING 24 HRS.

D .M . FAECES) OF 3 Cows BEFORE AND ( D.M.FoOD

A FTER C ALVING.

Days from calving: Cow

No. 4

3

2

I

0

1

2

3

4

7

0·39 0·37

-

0.26 0·38 0·44

0·34 0.42 0·39

0.25 0·34 0·44

0.20 0.22 0.27

0·31 0.29 0.28

0.3 1 0·39 0·37

0·33 0·34 0·34

0·30 0.40 0.3 1

0·35 0·38 0.4 1

0·38

0.36

0·38

0·34

0.23

0.29

0·36

0·34

0·34

0·38

J 2

3

Mean

After

Before

(2) Inhibition of alimentary activity by means of hyoscine injections had no effect on serum

calcium in dry cows, but in'. lactating cows biochemical and physiological effects were produced very similar to those found in calving cows of the same age and in cows developing milk fever. (3) Acute lowering of blood calcium for short periods in 2 cows by means of sodium oxalate produced no evidence of slowing or weakening of rumen activity or decrease in rumen .

~~

TABLE

vn

RATIO BETWEEN THE DRY MATTER EXCRETED IN THE FAECES AND THE DRY MATTER OF THE FOOD CONSUMED DURING

D .M . FAECES)

24 HRS. ( D.M. FOOD

OF

4 Cows INJECTED WITH HYOSCINE HYDROBROMIDE

Days from injection

Before Cow

After

No.

F4 D 19 E 14

Pn Mean

1

0

1

2

3

0·34 0.3 1 0·38 0·31

0.21 0.24 0.14 0.19

0·30 0·34 0·33 0.22

0.50 0·37 0·38 0·37

0.26 0·32

0·34

0.20

0·30

0·41

0·34

-

0·43

E. W. Moodie and A. Robertson Thus evidence is accruing from these and previously-reported observations that parturient hypocalcaemia can be induced by a failure in the activity of the digestive tract in older animals where mobilisation of other sources of calcium are inadequate, and that the changes observed in some of the other blood constituents may be purely secondary in nature. ACKNOWLEDGMENTS

The wholehearted assistance of Mr. A. Laing, farm manager, and Mr. R. Munro, chief technician of the Department of Veterinary Hygiene and Preventive Medicine, is gratefully acknowledged. Receivedfor publicationFebTlJary

121h, 1962.

REFERENCES ALEXANDER, E, and Mooma, E. W. (1960). Res. vet. Sci., 1,248. BARKER, S. B., and SUMMERSON, W. H. (1941). J. bioi. Chem., 138, 535. BLOSSER, T. H., and SMTIH, V. R. (1950). J. Dairy sa; 33,81. CHANG, T. S., and FREEMAN, S. (1950). Amer. ]. Physiol., 160, 330. FREEMAN, S., and CHANG, T. S. (1950a). Ibid., 160, 335. (1950b). Ibid., 160, 341. fRIEDEMANN, T. E., and HAUGEN, GLADYS E. (1943). J. bioi. Chem., 147, 415. HAllGREN, W., CARLSTROM, G., and JONSSON, G. (1959).

Nord. Vet.Med., II, 217. LE BARS, H., NITEScu, R., and SIMONNET, H. (1953). Bull. Acad. vet. Pr., 26, 351.

McARDLE, B. (1955). Biochem. j., 60, 647. MARR, A., Moonts, E. W., and ROBERTSON, A. (1955). J. compo Path., 65, 347. Mooors, E. W., (1960). Vet. Rec., 72, 1145. - . , MARR, A., and ROBERTSON, A. (1955). Ibid., 65, 20. and ROBERTSON, A. (1961). Res. vet. Sci., 2, 217. ROBERTSON, A., PAVER, H., BARDEN, P., and MARR, T. G. (1960). Ibid., I, 117. STEVENS, C. E., and SELLERS, A. F. (1959). Amer.]. vet, Res., 20, 461. SOMOGYI, M. (1952). J. bioi. Chem., 195, 19· VALLENAS, G. A. (1956). Amer. J. vet. Res., 17, 7'). WARD, G. M., BLOSSER, T. H., and ADAMS, M. F. (1953). Cire. Wash. agrie. Exp. Sta. No. 220, State College of Washington, Pullman, Washington. - . , and CRILLY, J. B. (1953).]. Dairy Sci., 36, 39·