Studies on the influence of calcium formate on growth, digestibility of crude nutrients, nitrogen balance and calcium retention in weaned piglets

Studies on the influence of calcium formate on growth, digestibility of crude nutrients, nitrogen balance and calcium retention in weaned piglets

Studies on the influence of calcium formate on growth, digestibility of crude nutrients, nitrogen balance and calcium retention in weaned piglets Abs...

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Studies on the influence of calcium formate on growth, digestibility of crude nutrients, nitrogen balance and calcium retention in weaned piglets

Abstracl 4n cxpcri~&W dietary

c.+ium

formal.

with formate

in addition

sion citiciency nutrients

3x 12 waned (Group

lu calcium

and. in Iwo balance

as well BS r~tenlmn

cral compound

lowrrcd

piglets t%as rarrled

C)

m compnr~san

carbonate

(Croup

oidwrhoen.

Wllh

gain was 3.2% higher and Ihc feed conwrsmn wcighl.

grstibllity

al Icast

the digcslibililg

oforgamc

malter.

of nulriinls

(Gmup

studted

clficac) 4)

of I.%

and c&turn

were growth,

Calcium

formaw

feed con\er-

calcium

formntc

eflicwnc?

inrwad

was tmprovcd

crude ash. crude librc and mwogcn-free

and calcium-relenlron

wcrc obsencd

as a pcrccmage

of

as an cncrgy-prowdmg

from 6.5 10 5.6 and slabiltzcd

the dlgerrion

of calcium formate

cxlraclives

III nnrogcn-re~cnrwn.

mtn. of !he

carbonate.

b) 3.7%. From

incrcascd in all groups. Calcium

in one balance trial. No differences

hilit? ofcalcium

carbonate

lnals s1anmg al bvc we~ghls of IO kg and 20 kg. dipslibilit)

ofnitrogen and C~ICIURI.

the pH value of Ihu dirt

piglcls with fewer incidences hod!

ou1 10 stud? Ihc nulrntrc

10 calcium

B 1. Thz crilena

till?

IO kg 10 20 kg

Impwed

lhe di-

( NfE f cgmficantlg. whcrcos the digcstl-

of Intake were sigmficanll)

mlprowd

by ral-

cwm foormalc in both balance trials. Calcium cficct wth

formale

as a supplement

regard 10 feed Intake.

bilitg of fat was signdicantly level when calcium

formale

10 a det

almad!

mcc~mg calrium

daily gam and fccd conversion

rcduccd.

cflicienc~.

For thls reason iolal cnlcwm

IS supplcmenlcd

rcqu~remcntr

had a negaliw

In particular

the digcsu-

should not cxcccd the optimum

to piglet dirts.

Introduction Calcium formate., a non-corrosive food additive in powder form, increases the acidity of the feed and contributes to the calcium supply of piglets. At the same time formic acid can be utilized energetically by the organism. Various studies have reported on the positive effects of calcium formate when used in diets for piglets (Schutte and Van Weerden, 1986; Kirchgessner and Roth, 1987) and for finishing pigs (Kirchgessner and Roth, 1987), resulting in a *Correspondingauthor.

66

J ,‘d,“,,L .I ,,arrr / I,rm~“,Ar~d.s~,c’,,~r’ond~nh~ildoy~ 43 IIYY.0 hT- -6

higher weight gain combined with an improved feed conversion and in general a more stable digestion. The aim of the present study was to examine the effect of calcium formate on the performance of weaned piglets, in particular the digestibility of crude nutrients, and nitrogen and calcium retention. Materials and methods Experimenral design In order to study the effect of calcium formate supplementation, a basal diet (Table I ) containing calcium carbonate (Group A) and meeting the requirements for weaned piglets according to the Gesellschaft fur Emlhrungsphysiologie (GfE, 1987) was supplemented with 1.5% calcium formate (Group B); for Group C calcium carbonate was omitted and only 1.5% calcium formate was added. Thirty-six weaned, castrated male, cross-bred piglets were purchased with an average live weight of 8 kg. After treatment for endoparasites, the animals were divided into three groups of the same average weight, each containing 12 piglets. The piglets were kept in individual metabolic cages for the total duration of the trial (42 days). After 1 week, at an average live weight of IO kg, the first collection period of 7 days began. A second period (7 days) followed at an average live weight of 20 kg. Room temperature gradually declined from 28°C initially to 22°C. Urine and faeces were collected separately twice daily during the trial and aliquot parts were put into airtight containers and stored at -20°C until analysis. Diers Soya-bean meal, skimmed milk powder and fish meal the protein of the basal diet (Table 1). t_-lysine-HCI and added so that the diet contained a total of 1.09% lysine oninc plus cystine. The energy adjustment of the diets metabolizable energy (ME) content of calcium formate was effected by replacing cellulose by corn starch. The diameter 4.5 mm) were fed three times daily, nearly ad

provided the bulk of t>L-methionine were and of 0.68% methitook into account a of 3.3 MJ kg-‘, and pelleted diets (pellet libitum.

Analysm andstatistkc Determination of the crude nutrients in the feed and excrements was carried out according to Naumann and Bassler ( 1976); the content of the crude fat fraction was analysed after HCl hydrolysis (Method B). A Kjel-Foss Au-

Composition (g kg-’

)ofthc

Compositmn (g kg-’

)

basal iced and the tsocncrgcr~ erperimenta! dxrs

tfO.SOlJid M?lllC

Whcal Barlcy Whcal bran Soya-bean meal exrracted Skimmed milk powder Fashmeal Sunflower oil MIneral prcm,x’ Vitamin premix> oL-Mcthionine !_-Lysine-HCI

300 200 I30 85.4 130 50 40 20 IO 5 0.4 1.7

Total

972.5

Expenmcnlal diets

Trcatmenl group

Total

c

6

A

Basal feed Calcium formale Calcium carbonate Stzirch Ccllul0se

972.5 12.5 2.9 12.1 IOO0.C

972.5 15.0 12.5 _ 1noo.o

972.5 l5.U

12.5 1000.0

‘Mineral premix (mg kg-’ dlet): Ca, 1080; P. 1330; Na. 1380: Mg, 300: Fe, 100; Cu. 23: Mn. 55: 2”. 100:1.0.40;Sc,0.20:C0,0.2j. ‘Vitamin premix (mg kg-’ diet 1: retinal. 5.4: cholccalcifcrol, 0.06: n-tocopherol, 30: mcnndionc bisulphite, 6; thiamine, 3; riboflavin. 4.5; pyridoxine, Q; cyanocobalamm, 0.045; ascorbic acid. 60: biotin. 0.09: choline chloride. 400: fohc acid, 0.6: mco~mx acid. 18: panlothcnic acid. 8.

tomat (N. Foss-Electric) was used for nitrogen determination. Gross energy was determined by adiabatic bomb calorimetry (C-400; IKA) and the calcium analyses with an atomic absorption spectrophotometer (PU 9400; Phiiips). The pH value as well as the buffer capacity of the diets were determined in a 20% aqueous suspension; the latter was expressed as the amount (m1) of 0. I N HCl per IO0 ml feed suspension necessary to bring the pH to 4 (Jung and Bolduan, 1986). Table 2 shows the nutrient content analysis of the experimental diets as well as their calculated energy content. The statistical evaluation of the experimental results was effected using variance analysis and SPSS program. Differences in mean values were tested for significance according to Duncan.

,CKO%)

B (Cafo+CaCO,)

C (Cafe)

820.5 59.5 191.2 59.1 46.6 523.6 399.8 39.1 8.3 6.9

810.3 69.7 189.4 59.8 36.9 524.2 397. I 35.7 13.0 6.8

822.9 57.1 189.1 59.9 48.0 525.9 397.8 38.2 8.2 6.7

A

Organic matter Crude ash Crude protein Crude fal Crude Iibre NfE Starch Sugar Calcium Phosphorus Ca/P PH

ratio

I.21 6.47 49.6 17.18 13.85

Buffering capacity

(ml)’ Gross energy (MJ kg-‘)2 ME (MJ kg-‘)’

1.91 5.90 53.3 17.26 13.88

1.22 5.64 29.0 17.26 13.81

ICD

‘Millilitres 0. I N HCI per ml feed suswnsion. “Dcrermined by adiabatic bomb c~lonmelry. ‘Calculated on ~hc basis of crude nutrient content according Cafe, calcium formate: NfE, nitrogen-free cxlractivc^s.

IO GfE ( I987 ).

Results Incidence of diarrhoea

During the first week and in isolated cases after the start of the first collect-

ing period there were a few cases of mild diarrhoea. The incidence of diarrhoea (animalsxdays) was spread over the three groups as follows: Group A 13days, Group B 6 days, Group C 5 days. Supplementation of calcium formate led to a reduction G:owth andfeed

in the incidence of diarrhoea.

conversion

At the beginning of th: experiment, supplementation with calcium formate led to a slightly reduccj &d intake. However, there was an increased daily weight gain and therefor? improved feed conversion efficiency (Table 3 ). Throughout the entire trial (42 days) the die* with calcium formate and adjusted calcium conten _(Group C ) resulted in a 3.2% (not signiticant) higher weight gain and a 3.’ % (not significant) better feed conversion compared

69

Live wigI& weight gain. feed intake and feed c”“vcrsi”” cflicwncy ofp&is days1 and I” the colle~lmn periods

I

in lhc lolal period (42

0.9 t1.99 22.91” f3.12 610 +64 309’ * 35 .97’ 20.12

9.98 c 2.42 24.76” r3.27 636

453 +I11 259 +X9 1.75 kO.61

422 f72 267 i65 1.58 iO.18

J?I ?91 28X lriX 1.46 + 0.49

Smmd rullrcrron pwiod (20 kg waghr) Daily feed inlake (g) 957 ?a5 Daily gain (g) 511 ?76 Feed conversion 1.87 (kg feed kg-’ gain

931 +75 524 f36 1.78 to.15

972 272 537 AT39 1.77 iO.l4

9.61

i 2.02 23.92’ + 3.58 640 *X7 341”h +46 I .XP

Daily feed intake (g) Daily gain (g) Feed conversion (kgfeedkg-‘gam)

1013

Daily gain (g) Feed conver~m” (kg feed kg-’ gain)

)

Means Ahin

?0.22

I

a TOWwith dCferent superscripts differ significandy (P
with the diet containing calcium carbonate (Group A) and covering the calcium requirement. However, supplementation of the basal diet (already containing calcium carbonate) with calcium formate led to a significantly lower weight gain as well as to poorer feed conversion. Digestibilily

of crude nutrients

and nitrogen balance

At a live weight of 10 kg, metabolizable energy intake by the piglets was on average 1.5 times the maintenance requirement ofME, (MJ day-‘) =0.719x Wo.63 (GfE, 1987) and increased to 2.2 times the maintenance requirement at a live weight of 20 kg. The digestibility of all crude nutrients increased with

I Pullu,~ 1. IllaL? /An,“,., &l?fSrw”wPo”d z~kaul”g~ 4, IIYPJ, 65-76

70

live weight (Table 4). Most digestibility coefficients were improved with calcium formate supplementation (Groups B and C) particularly during the first collection period. At 10 kg weight there were significant differences compared with the calcium carbonate group (Group A) in the digestibility of organic matter, crude fibre and NfE. In the second collection period at a live weight of 20 kg, higher digestibility values were also found as a result of calcium formate supplementation, with significant differences in crude ash digestibility between diet A (calcium carbonate) and diet C (calcium formate). The high calcium content in the Group B (calcium carbonate plus calcium formate) diet led to a significant reduction in the digestibility of crude fat in both collection periods. For the ME calculated on the basis ofdigestible crude nutrients (GfE, 1987) at a live weight of IO kg, the calcium formate supplementedgroup with a 12.9 MJ ME kg-’ diet exceeded the calcium carbonate group by 3.2%. At a higher live weight, however, there were hardly any differences between the treatments. Metabolizable energy was closely related to the digestibility of crude fat (r-=0.86 as an average of both periods). Calcium formate supplementation in both periods led to reduction in the MJ of ME required per kg live weight. At approximately 20 MJ ME kg-’ as opposed to 23.8 MJ ME kg-’ Table 4 Appwznt con,cn,

digestibility

of nutrients

Trcalment

Organic mamr

Crude ash Crude protein Crude

rat

Crude iibrc NfE ME (MJ kg-‘dia)’ ME (MJ ka-’

(%) 81 10 kg and ZC kg live weight as well as metabolizable

al 10 kg weight

Treatment

cncrgy

at 20 kg weight

A (taco,)

B

C

A

B

C

(carO+caco,)

(care)

(taco,)

(caro+caco,)

(cafO)

82.5” f2.3 55.3 26.1 7Y.3 ? 5.6 67.4” f9.5 35.4” t7.3 90. I= fl.5 12.6”’ kO.5 23.8

84.3=” * 2.2 58.1 * 5.4 X2.1 ?L3.3 60.6” A8.6 40.9”” + 7.6 90.9’h t I.2 12.5” ? 0.4 20. I

84.9” ? 1.6 59.8 +4.1 XI.7 + 2.0 70.2” +5.1 45.0” k6.Y 9l.JD t I.1

85.0 * 1.3 5X.71 2 3.4 X4.2 +2.2 13.F f2.8 40.5 kY.8 90.5 t I.2 13.0 to.2 24.7

86.4 ? 1.3 60. I lb * 3.3 X6.3 * 2.0 71.6’ +3.6 44.5 * 5.9 91.1 to.8 13.0 ? 0.2 23.1

86. I + 1.9 61.6b +2.7 x5.4 i2.8 76.5” * 2.4 41.5 kY.1 91.5 z! I.2 13.2 kO.3 23.4

I2.P

i-o.3 IY.9

‘Cnlculalcd on the basis ofdigsstiblc nutricnls. Means witbin a TOWwlh dtffcrem superscripts ditTci signilicanlly Cafe. calcium formatc: NfE, nitrogen-fnx cxtractircs.

(P
Nimgenmakc

13.86

(gday-‘)

f341 l%ca,

““rogc”

Urinary

,g clay-‘,

“itmgc”

Igday-’

Nmogcn

rew”lmn

&day-‘,

Nwoge”

mention

(?6)

IZ.Xl ??

> 8,_

)

18

,277 i2.77

2.27

2.31

29.57 k2.60

28 26 i2.27

4.63

19.44 -2.17

3.87

4.29

1096

t OS?

to47

to.56

3.34 i 0.89 7.70

3.04 I 0.53 7.50

3 23 to.85 7 23

1.39 ?I.,, Il.55

+ 0.99 17.3,

7 53 i ?.KZ 17.61

f 2.30

kI.55

+ 1.91

il.95

t 1.57

T 1.85

54 9 27.1

58.2 t 3.7

56 1 i 5.6

to.80

to.73

59 3 k 2.9

7.08

61.2

I

60.

13.1

r 6.X

Cafe. caIcI”m fomlate.

Calcium

intake (g&y-‘)

Faccalcalcium .Appare”t

(gday-‘1

absorplian

of calctum (%) Urinary calcium (medav-‘)

ral&ll Aenmn &day-‘)

Cahum

rcknmn

(%)

398 r0.83 ?.?7a

t 1.07

+0.53

to.80

3.12”

3.4X’

i 0.70

1.76’ t 0.45 49 4b

42.2” t3.4 83.7” i 33.4 1.57’ f0.34

45.3’b + 7.7 179.4” t 88.6 2.410 +a.53

t5.3 95.7’ t55.1 .6?’

40.1’

42.P

46.5b

i3.3

+ 8.2

I

kO.32 f 5.2

8.49’

12.03”

tlo8 4.55

3 0.97

t 1.03 46.4’

kO.81 55.4b

k7.5 480.01 zk388.7 3.46” k 0.46 40.7’ ? 6.4

5.36b

t 5.5 898.P f 519.6 5.7X’ to.97 4S.Ob 2 1.8

3.971 iO.59 3.311 i0.35 57.6b + 3.4 406.4’ f 344.8

4.1aa

to.52 5?.4b t6.2

weight gain without calcium formate supplementation, the difference was greater in the first period. Calcium formate supplementaticn without correction of the calcium content (Group B) led to a significant reduction in the digestibility values of crude fat of approximateiy 10% and 5%, respectiveiy, in the two collection periods, which had negative effects on the energetic evaluation of the feed. Nitrogen retention was not significantly affected by calcium formate (Ta-

ble 5). Only in the case of nitrogen retention as a percentage of the intake did the calcium formate groups show slightly higher values. Calcium retention Calcium formate supplementation (Group C), in contrast to calcium carbonate supplementation (Group A), led in both balance periods to a 7.2% and 1 I .2% higher calcium digestibility and also to a significantly higher calcium retention expressed as g day-’ and percentage of intake (Table 6). The high calcium content in the feed of Group B resulted in significantly higher values for Ca retention when expressed as g day-‘, compared with Groups A and C, accompanied by approximately double the renal calcium excretion. Discussion At weaning, piglets frequently suffer from digestive disturbances. According to Manners ( 1976) the not yet fully developed gastrointestinal system does not secrete suflicient HCI. As a result of this, pepsinogen is not optimally activated and the stomach does not represent the desired barrier for bacteria, consumed orally (Aumaitre, 1983). In the present study calcium formate supplementation reduced feed pH r&es by up to 0.8 units and at the same time the buffer capacity of the feed was lowered. So even a small quantity of secreted stomach acid is able to lower the pH value of the digested feed. These factors could explain the reduced incidence of diarrhoea in the trial, as was similarly re.ported by Kirchgessner and Roth ( 1987, 1989) on the supplementation of calcium formate to the feed of piglets and finishing pigs. The reduced feed intake resulting from calcium for.mate supplementation at the beginning of the trial agrees with the findings of Jos; and Bracher-Jakob ( 1991) as well as those of Biihme ( 1991). In these studies the live weight gain and the feed conversion were also negatively influenced. Ti:e option trials of Henry et al. ( 1985) offer an explanation for this as they showed that pigs exhibited a marked preference for a non-acidic feed. Kirchgessner and Roth ( 1987, 1990) reported a slight reduction or an unaltered feed intake. 1n their experiment, calcium formate supplementation in general improved feed conversion by 3.4% and 4%, respectively. This compares with the 3.7% improvcment seen in the present study. Schutte and Van Weerden (1986) also found higher daily gains accompanied by improved feed conversion with a 1.5% calcium formate supplementation. The lowest feed intake, low weight gain and poorer feed conversion was shown by the high calcium Group B (calcium formate plus calcium carbonate). Weigand et al. ( 1988) also found that an increasing calcium/phosphorus ratio or too high a concentration of calcium in the diet caused depression of the feed Lttake and growth rate.

J PWlO”%J uiiwr / I”,,,,<,, hd

.s‘w.u

md 7
73

During the second collection period higher digestibility values could be observed for all crude nutrients. These reflect the physiological adaptation of the piglet’s digestive system after weaning (Aumaitre, 1983). The variation in the digestibility coefftcients within the groups decreases for the heavier animals. This points to bigger individual differences in the animals in the early stage of the development of their digestive capacity. The digestibility valuer found cnrr~~pnn? with those of other studies using diets based mainly on maize and other cereals. The digestibility of organic matter of 83-869/o found by Broz and Schulze ( 1987) is comparable with the results of the present study. Studies on the intluence of calcium formate on the digestibility of nutrients have so far only been carried out by Jest and Bracher-Jakob ( 1991). The digestibility values found for the crude protein and gross energy were not affected by calcium formate. Supplementation of calcium propionate did not influence the total digestibility compared with the control group according to Roth and Kirchaessner ( I982 ). In the absence of further oossible comparisons the digestibility values found should be discussed in relation to studies on organic acids. According to Kirchgessner and Roth ( 1980) as well as Pallauf et at. ( 1987) fumaric acid improves growth rate and the digestibility of almost all crude nutrients by 2-396. In a further study of Pallauf and Walz ( 1988), the positive effect ofthis acid could not be confirmed. The closer the diets were adapted to the nutritional requirement and physiological development of the young animal (e.g. by a high proportion of highly digestible protein sources and conditioned starches), the less, in general, appeared to be the influence of organic acids or their salts. In the present experiment, calcium formate showed a positive effect on the digestibility of crude nutrients with significant improvements for crude ash, crude tibre and NfE. In Group C the ME content of the digestible nutrients reached a maximum in both collection periods: 12.9 MJ ME in Period 1 and 13.2 MJ ME kg-’ diet in Period 2. This, however, was still below the energy content of 13.8 MJ ME kg-’ calculated from the analysis of crude nutrients. In a digestibility trial Pallauf and Walz (1988) obtained higher energy values than were estimated on the basis of the crude nutrients. However, the diet was based on particularly highly digestible components such as oat flakes and corn starch, components which are seldom used in practice for feeding weaned piglets. The energy expenditure per kg live weight gain of 20-24 MJ kg-’ in the present trial corresponds with the values found by Bijhme ( I991 ). However, because of a severely reduced feed intake in the trial of Biihme ( 199 I ) the calcium formate group could not be shown to be superior to the control group. The increased digestibility of crude ash with calcium formate supplementation in the present trial indicates a better availability of calcium from this organic compound. The negative influence of the unbalanced high calcium content in Group B

led to a significantly lower crude fat digestibility. According to Molnar and Thole (1987) the formation ofcalcium salts (lime soap) in the digestive tract inhibits the absorption of fat if the dietary calcium content is high. A lower pH value in the feed resulting from calcium formate supplementation facilitates the activity of the pepsin enzyme, thus promoting protein digestion in the stomach. The use of highly digestible protein sources of animal origin may explain (Giesting and Easter, 19g5) why only a tendency towards an improved protein digestibility could be observed in the present study. Similarly, as found for the digestibility of the other crude nutrients, the nitrogen balance (as a percentage of intake) also showed an age-related increase as shown earlier (Pallauf et al., 1987). The slightly reduced feed intake in the first collection period led to a lower nitrogen retention (in g day-‘) in the calcium formate groups. With regard to nitrogen balance, the non-significant superiority of the calcium ibrmate supplementation as opposed to calcium carbonate is related to the reduced fecal nitrogen excretion and this reflects the tendency of improved protein digestibility. Thus calcium formate can also increase nitrogen retention as was shown for fumaric and citric acid (Pallaufand Walz, 1988). Although the supplement to the basal mix in Groups C and A represented only slightly more than 50% of the calcium in the total diet, calcium formaie (Group C) as opposed to calcium carbonate (Group A) led to significantly higher calcium digestibility as well as to higher c&urn’ retention-expressed as percentage intake. Kirchgessner and Roth ( 1980) reported increased calcium retention under the influence of fumaric acid, whereas Walz and Pallauf ( 1990) found that fumaric acid had no influence on calcium retention and that citric acid even had a negative effect. Calcium fomlate, however, can only be partly compared with the above free acids, for although it likewise has a mild acidifying effect, it is also a source of calcium. Supplementation of calcium formate plus calcium carbonate (Group B) led to a significantly higher calcium retention expressed in g day-‘, but the approximately 100% higher renal excretion of calcium indicates severe calcium oversupplementation, as was reported also by Kamphues and Schrgder ( 1990) in studies on pigs with excessive calcium intake. In conclusion, calcium formatc as a feed additive is suitable for acidifying the diet slightly and for lowering the buffering capacity of a feed. Compared with calcium carbonate it reduced the incidence of diarrhoea and related digestive disturbances. Feed conversion efficiency and digestibility of crude nutrients as well as ofcalcium were improved by calcium formate supplementation. Metabolizable energy contents, calculated on the basis of digestible nutrients, were also positively affected. To prevent a depressed feed conversion and particularly a lowered digestibility of the crude fat fraction, total calcium should not exceed the recommended level when calcium formate is supplemented to piglet feed.

75

Aumaitre. A., 1983. Die Enlwtcklung der Verdauungsfunklionen bctm Ferkel sowic Problcme des Absetzens. iibersichten TlcremBhr., I I: 103-124. Biihme. H., 1991. Zur Wirksamkeil van Calcmmformiat in dcr Ferkelaufzuchl. VDLUFASchriftenreihe Bd. 33. VDLUFA-V~rlag. Darmstadt, pp. 439-444. Broz. J. and Schulze. J., 1987. Efftcacy of citric acid as a feed addilive in early weaned piglets. J. Anim. Physiol. Anim. Nmr.. 58: 215-233. Gesellschafi fdr Em%hrungsphysiologie (GIE). 1987. Energic- und N%hrstoffbedarf landwinschaftlicher Nutztiere, .Jr. 4 Schweine. Ausschuss ftir Bedarfsnormen der Gesellschaft fir EmBhrongsphysiologie. Deutschc Landwirtschafts-Gcsellschafl, Frankfurt/M. Gicsting. D.W. and Easter. R.A.. 1985. Response of starter pigs to supplementation of cornsoybean meal diets wrlh xganic acids. J. Anim. SC].,60: 1288-1294. Henry. R.W., Piekard, D.W. and Hughes, P.E.. 1985. Cttric acid and fumaric acid as food additives for early weaned piglets. Anim. Prod.. 40: 505-509. JO% M. and Bracher-Jakob, A., 1991, Einsatz van organischen SBuren im Fatter ftir .Auhuchtferkel. Landwinsch. Schweiz., 4: 133-136. Jung, H. and Boldoan, G.. 1986. Zur Wirkung unterschiedlicher Mineralstoffanteile m der Ralion des Absetzferkels. Monatsh. Veteriniiroxd., 41: 50-52. Kamphues. J. and Schriider, B.. 1990. Untersuchungen zum Ca-Haushalt van Schweinen bei exzffniver Ca-Aufnahme. J. Anim. Phys. Anim. Nuw.. 64: 17-18. Kirchgcssner. M. and Roth, F-X.. 1980. Verdaulichkcit und Bilanz voo Protein, Energie und einigen Mineralstoffen bei Fumanaurczulage an Ferkel. 2. Tierphysiol. Tierernlhr. Futtermittelkd.. 44: 239-246. Kirchgeesner, M. and Roth. F.X., 1987. Use of formales in the feeding of piglets. Is1 communication: Calcium formate. Landwinsch. Forsch.. 40: 141-152. Kirchgessner, M. and Roth, F.X.. 1989. Use ofcalcium formate in the fattening ofpigs. Landwirtsch. Forsch.. 42: 150-l 56. Klrchgessoer. M. and Roth, F.X., 1990. Nutritive effect ofcalcium formare m combination with free acids in the feeding of piglets. Agrobiol. Rcs., 43: 53-64. Manners. M.J.. 1976. The development of digestive fun&on in the pig, Proc. Nulr. Sot.. 35: 49-55. Molnar. S. and Tholc. 9.. 1987. Untersuchungen zum EinIluss erhiihter Ca-Gaben auf die Seifenbildung und Fettabsorption beim Schwein. 2. Tierphysiol. TicrcmPhr. Futtermittelkd.. 57: 82-86. Naumann, K. and Bassler. R.. 1976. Untcrsuchung voo Futtermitwln. 3. Aull. Neumann-Neudamm, Melsungen. Pallauf, J. and Wah. O.P.. 1988. Untersuchungen zum Einlluss van Zulagen an Fumarsaure und Cilronenslure bei unterschiedhcher Fiittcrungsinlensit%t auf Verdaulichkeit der RohnPhrstoffe und N-Bilanz beim friihemwBhnlen Ferkei. Landwirtsch. Forsch., 41: 109-l 19. Pallaof, 1.. Gijltert. W. and Kr&ner, K., 1987. Zum Einfluss van Fumars;iure auf NBhrstofiverdaulichkeit und N-Bilanz beim Ferkel. Landwirtsch. Forsch., 40: IZO-I 30. Roth. F.X. and Kirchgessner. M., 1982. Zum nutritiven Einsatz van Ca-Pmpionat in der Fcrkelaufzucht. Das wirtschaftseigene Futter, 28: 235-242. Schuttc. J.B. and van Weerden. E.J., 1986. Cafo as a feed additive in diets for young pigs. IlobReport 575. Wageningen. Wall. O.P. and Pallauf. J.. 1990. Untersuchung zum Vergleich des Bilanzverfahrens und drr Ticrkijrperanalyse zur Messung des Protem-. Encrgie- und Mineralsloffansatzes van Aufzuchtferkeln J. Anim. Physiol. Anim. Nmr., 64: 103-I II.

Weigand, E., Kirchgessner, M. and Kaufman T.E.G., 1988. Einfluss abgestuftcr Ca:P-VcrhPltnissc im futtcr auf Wachslum und Futtervenvcnung van Absatzferkeln. Ziichlungskunde.60: 143-154.