Livestock Production Science 63 2000 17–26 www.elsevier.com locate livprodsci
Neither native nor popped cornmeal in the ration of dry cows affects magnesium absorption
a , a
b a
J.Th. Schonewille , A.Th. Van ‘t Klooster , J.W. Cone , H.J. Kalsbeek-Van der Valk ,
a a
H. Wouterse , A.C. Beynen
a
Department of Nutrition , Faculty of Veterinary Medicine, Utrecht University, P.O. Box 80.152, 3508 TD Utrecht, The Netherlands
b
DLO-Institute for Animal Science and Health , Department of Ruminant Nutrition, P.O. Box 65, 8200 AB Lelystad, The Netherlands
Received 16 November 1998; received in revised form 19 May 1999; accepted 1 June 1999
Abstract
The hypothesis tested was that addition of starch to the ration of cows would stimulate magnesium Mg absorption because of a lowering of ruminal pH, which renders Mg more soluble and thus more available for transport across the
epithelium of the rumen, which is the major site of Mg absorption in ruminants. The trial had a 5 3 5 Latin-square design in which five non-pregnant, non-lactating multiparous cows were fed rations containing either a mix of cellulose and
maizeglutenfeed or native or popped cornmeal each at two levels equivalent to 11 or 20 starch in the dry matter. The dietary periods lasted 28 days. The amount and type of dietary starch did not significantly affect total gastro-intestinal tract
Mg absorption, post-prandial ruminal pH, rumen fluid concentrations of Mg, K and total volatile fatty acids; for all five treatments combined, the measured values were 5.660.45 of intake, 6.560.04, 0.760.12 mmol l, 41.060.63 mmol l, and
10562.3 mmol l means6S.E., n 5 5, respectively. For all cows and treatments combined, there was a significant, negative relationship between ruminal pH and Mg concentration in rumen fluid. The ruminal Mg concentrations were low when
compared with earlier work. On the basis of published in-vitro studies showing that concentrations of soluble Mg fall to more or less constant, low values when pH values are above 6, it is suggested that the high baseline values of ruminal pH in
this study, had prevented a statistically significant effect of starch intake, if any, on Mg absorption.
2000 Elsevier
Science B.V. All rights reserved.
Keywords : Magnesium; Starch; Rumen; Fermentation; Absorption
1. Introduction Schonewille et al., 1997a. In ruminants, high K
intakes inhibit magnesium Mg absorption which Grass silages from areas with intensive livestock
enhances the risk of hypomagnesaemia Fontenot et production are generally high in potassium K
al., 1989. To safeguard the Mg status of dairy cows fed grass silages rich in K, it seems more appropriate
to improve Mg absorption from the diet rather than to supplement the ration with Mg because high Mg
Corresponding author. Tel.: 1 31-30-2531581; fax: 1 31-30-
intakes by ruminants may cause a depressed nutrient
2531817. E-mail address
: J.Schonewillevet.uu.nl J.Th. Schonewille
utilisation Chester-Jones et al., 1989.
0301-6226 00 – see front matter
2000 Elsevier Science B.V. All rights reserved. P I I : S 0 3 0 1 - 6 2 2 6 9 9 0 0 1 1 9 - 0
18 J
.Th. Schonewille et al. Livestock Production Science 63 2000 17 –26
In a study with dry goats the replacement of 2. Materials and methods
dietary cellulose, at a concentration of 342 g kg dry matter, by an equal amount of native corn starch had
2.1. Animals and experimental design a marked stimulatory effect on Mg absorption
Schonewille et al., 1997b. It is not known whether Five non-pregnant, non-lactating multiparous cows
this observation extends to dairy cattle. In any event, age 10.360.8 y; mean6S.E., fitted with rumen
the use of high amounts of starch in the ration of cannulas, were used. The cows were of a Friesian–
dairy cows entails the risk of ruminal acidosis and Holstein 3 Holstein–Friesian cross. During the ex-
increases feed costs to a practically unacceptable periment, they were housed in a stanchion barn.
level. Thus, to test whether consumption of corn The trial had a 5 3 5 Latin-square design and was
starch raises Mg absorption in cows, we used in the preceded by a 14-day pre-experimental period that
present study diets that contained either 100 or 200 g allowed the cows to become adapted to rations based
starch kg dry matter in the form of cornmeal. primarily on artificially dried grass. Each experimen-
A possible mechanism by which starch could tal period lasted 28 days. The animals were random-
increase Mg absorption is a lowering of ruminal pH ly assigned to each sequence of feeding on the five
which renders Mg more soluble and thus more experimental rations.
available for transport across the epithelium of the rumen, which is the major site of Mg absorption in
2.2. Rations ruminants Rogers and Van ‘t Klooster, 1969; Tomas
and Potter, 1976. Native corn starch is slowly During the pre-experimental period the daily
degraded by ruminal bacteria but popping of corn ration of all cows consisted of 4.5 kg artificially
starch increases the rate of ruminal fermentation dried grass, 0.2 kg barley straw and 2.2 kg of a
Cone et al., 1989; Cone and Vlot, 1990 and may commercially available concentrate containing 9.0 g
further lower ruminal pH Malestein et al., 1988. Ca, 4.9 g P and 6.3 g Mg kg. During the experimen-
Thus, it could be suggested that popped cornmeal tal periods, the commercial concentrate was replaced
enhances Mg absorption more than would native by 0.1 kg of a pelletted experimental concentrate and
cornmeal. This suggestion was tested also in this 2.1 kg powdered feed containing the dietary vari-
feeding trial with dry cows. ables. The ingredient composition of the experimen-
Table 1 Ingredient composition of the experimental rations
Control Native cornmeal
Popped cornmeal 10 starch of dm
20 starch of dm 10 starch of dm
20 starch of dm
a
Constant components kg d 4.8
4.8 4.8
4.8 4.8
b
Control mix kg d 2.1
1.05 ...
1.05 ...
c
Native cornmeal kg d ...
1.05 2.1
... ...
c
Popped cornmeal kg d ...
... ...
1.05 2.1
a
The constant components consisted of 4.5 kg of artificially dried grass 924 dry matter kg, 0.2 kg of barley straw 930 g of dry matter kg, and 0.1 kg of experimental concentrate 910 g of dry matter kg. The experimental concentrate consisted of 5.0 g of beet
vinasses, 92.6 g of beetpulp, 1.4 g of MgO, and 1.0 g premix. The premix consisted of 609.4 mg of CaCO , 3.0 mg of CoSO ? 7H O, 2.1
3 4
2
mg of Na SeO ? 5H O, 5.3 mg of KIO , 30.5 mg of MnSO ? H O, 27.5 mg of ZnSO ? H O, 150.0 mg of CuSO ? 5H O, 17.2 mg of
2 3
2 3
4 2
4 2
4 2
retinylacetate 50,000 IU, 5.0 mg of cholecalciferol 200 000 IU, and 150 mg
DL
-a-tocopherylacetate 150 IU.
b
The control mix 917 g of dry matter kg consisted of 63 g of distilled water kg, 639 g of cellulose kg, and 298 g of maizeglutenfeed kg.
c
The corn meal used in this study was derived from one batch. One portion was popped and ground to pass a 3 mm sieve. The dry matter contents of the native cornmeal and the popped cornmeal were 884 g kg and 881 g kg, respectively and the starch contents were 652 and
668 g kg dry matter, respectively.
J .Th. Schonewille et al. Livestock Production Science 63 2000 17 –26
19
tal rations is shown in Table 1. The control ration During the last eight days of each experimental
contained cellulose and maizeglutenfeed which was period, urine and faeces were collected quantitatively
replaced by either native or popped cornmeal so as to from each cow. Urine was collected by using urinals
formulate the experimental rations. In essence, this attached to the cows with the use of leather harnas-
replacement involved an exchange of cellulose ses. Urine coursed down into two vessels so that
Arbocel , Internatio B.V., Rotterdam, The Nether- approximately 80 was collected in one vessel. The
lands and corn starch. The native and popped remaining urine was collected in the other vessel
cornmeal were from the same batch and were which contained Na-azide as a preservative. Total
supplied by Presco International, Weert, The Nether- urine collections from each 24-h period were
lands. The analysed composition of the whole rations weighed, and 0.5 of the total urine was sampled
is shown in Table 2. from the preserved urine and stored at 2 188C in a
The animals were fed individually. On an energy plastic bottle which contained 100 ml 6 M HCl. The
basis, the rations provided approximately the require- daily faeces production of each cow was mixed
ment for maintenance. The rations were offered thoroughly, and 3 of the wet weight was stored at
twice daily in two equal portions at 08:00 and 17:00 2 188C. At the end of each collection period, the
h. Feed refusals, if any, were recorded. stored faeces fractions of each cow were combined,
mixed thoroughly and sampled. The samples were 2.3. Collection of samples
dried at 608C for four days, ground, and stored in air-dry form in sealed jars at room temperature until
During the last week of each experimental period, analysis.
the experimental feedstuffs were sampled daily and On day 19, approximately 10 min prior to the
then pooled, ground and stored in sealed jars at room morning meal, 350 ml of Cr-EDTA solution 100 g
temperature. Cr-EDTA l was injected into the rumen as a marker
Blood samples were taken on day 21 of each for estimating the rumen volume and passage rates of
experimental period. Between 16:00 and 16:30 h, the liquid phase from the rumen. Rumen liquid
before the afternoon meal, blood was sampled from samples approximately 30 ml were taken at 07:45,
the jugular vein into evacuated heparinized tubes. 09:00, 10:00, 11:00, 13:00, 15:00 and 17:00 h.
The blood samples were centrifuged for 10 to 15 min Immediately after collection, pH of ruminal fluid was
at approximately 2700 g, and the plasma was col- recorded and the rumen liquid samples were cen-
lected and stored at 2 188C. trifuged at room temperature at 2700 g for 15 min,
Table 2 Analysed composition of the experimental rations g kg dry matter
Control Native cornmeal
Popped cornmeal 10 starch of dm
20 starch of dm 10 starch of dm
20 starch of dm Crude protein
179 185
191 184
188 Crude fat
45 49
53 50
55 Crude ash
107 106
105 106
105 Crude fibre
337 260
181 260
180 Neutral detergent fibre
643 551
459 551
458 Acid detergent fibre
377 283
187 281
184 Acid detergent lignine
19 19
19 18
17 Starch
23 112
201 114
205 Mg
1.97 1.95
1.92 1.95
1.93 K
33.1 33.3
33.5 33.3
33.5 Na
1.17 1.10
1.04 1.10
1.03 Ca
4.90 4.84
4.78 4.83
4.75
20 J
.Th. Schonewille et al. Livestock Production Science 63 2000 17 –26
and the supernatant was stored in plastic tubes at stuffs and faeces was estimated by atomic absorption
2 188C. An aliquot of the supernatant from the spectroscopy
Perkin-Elmer 3110;
Perkin-Elmer, rumen liquid samples taken at 07:45, 09:00, 11:00,
Norwalk, CT, USA. Calcium and K in feedstuffs 13:00, 15:00 and 17:00 h was centrifuged at 208C at
and K in supernatant of rumen fluid were estimated 30,000 g for 30 min and the supernatant was stored
by atomic absorption spectroscopy and Na in feed- in plastic tubes at 2 188C. From the rumen liquid
stuffs by atomic emission spectroscopy Perkin samples taken at 07:45, 09:00, 11:00, 13:00, 15:00
Elmer 3110. Magnesium in plasma, urine, superna- and 17:00 h, 2 ml non-centrifuged fluid was de-
tant of rumen fluid, and chromium III in rumen proteinised according to the method of Bergmeyer
fluid were measured directly by atomic absorption 1970. After 10 min, the de-proteinised rumen
spectroscopy. The accuracy of each assay run was liquid samples were centrifuged at room temperature
monitored using a commercial reference sample hay at 2700 g for 15 min and the supernatant was
powder, CRM 129; Community Bureau of Refer- collected and stored in plastic tubes at 2 188C until
ence, Brussels, Belgium and laboratory reference analysis of volatile fatty acids VFAs.
samples, and was found to be within 5 deviation from the target values. The combined within and
2.4. Chemical analyses between-run precision of the determinations was
3.0 coefficient of variation. Samples of the feedstuffs were subjected to the
VFAs in rumen fluid were determined gas- Weende analysis. Nitrogen contents were determined
chromatographically Perkin Elmer Autoscan with a by the macro-Kjeldahl method IDF, 1986; a factor
2 m glass column Chromosorb WAW DMCS; 17 of 6.25 was used to convert g of N into crude
neopentyl glycol adipate, 1 H PO . Pivalic acid
3 4
protein. Ether extracts of the feedstuffs were pre- 0.045, w v was added to the de-proteinised
pared according to the AOAC 1984; the solvent ruminal fluid as an internal standard.
was evaporated and the crude-fat residue weighed. The crude fibre contents of the feedstuffs were
2.5. Statistical analyses estimated using the Fibertec System M2 Tecator,
Stockholm, Sweden. The NDF, ADF and ADL All data were checked for normal distribution
content of the feedstuffs were estimated according to using the Kolmogorov–Smirnov test and then were
the methods described by Goering and Van Soest subjected to analysis of variance ANOVA with
1970. To determine the starch content of the animal, experimental period and dietary treatment as
feedstuffs, they were enzymatically treated with factors Wilkinson, 1990. Rumen-liquid mineral
amyloglucosidase from
Aspergilles niger
EC data were subjected to repeated measurement analy-
3.2.1.3 to hydrolyse all starch to glucose Keppler ses with animal, experimental period and dietary
and Decker, 1974. Subsequently, glucose was mea- treatment as factors Wilkinson, 1990. When a
sured enzymatically with a test combination Boeh- dietary factor had a statistically significant influence,
ringer Mannheim Diagnostica, Mannheim, Germany Bonferroni’s test was used to identify the diets that
and a
computerised autoanalyser
Beckman had different effects on the variable involved.
Synchron CX Systems; Beckman, Mijdrecht, The
Throughout, the level of statistical significance was Netherlands. The free glucose content of the feed-
pre-set at P , 0.05. stuffs was measured directly. Starch was calculated
as total glucose minus free glucose. For the ex- perimental feedstuffs, i.e., the control mix and the
3. Results
