Livestock Production Science 62 2000 155–168 www.elsevier.com locate livprodsci
Requirements of lactating dairy cows for leucine and methionine at the duodenum
a b ,
M. Iburg , P. Lebzien
a
LOHMANN Tierzucht GmbH , Am Seedeich 9 –11, Postfach 460, 0-27454 Cuxhaven, Germany
b
Institute of Animal Nutrition , Federal Agricultural Research Centre Braunschweig, Bundesallee 50, D 38116 Braunschweig, Germany
Received 16 June 1998; received in revised form 6 April 1999; accepted 15 April 1999
Abstract
Infusion experiments were conducted with nine lactating dairy cows of the German Black and White breed in mid-stages of lactation, with a daily milk production averaging 20–25 kg fat-corrected milk FCM. The cows were fitted with rumen
and duodenal cannulae. The objective of the study was to investigate the cows’ requirements for leucine and methionine at zero N-balance as supply to the duodenum. Over a period of 13 weeks, the animals received rations that were sufficient for
maintenance plus 17 or 15 kg milk day, regardless of the actual, higher yields of the animals. Differences between estimated requirements according to recent knowledge and energy- and amino-acid supply by the ration were met by sucrose
hydrolysed-, caseine hydrolysed- and amino-acid infusion into the proximal duodenum. Alternatively, leucine and methionine were withheld from the infusion. Each experimental variation went on for five days. During this time, N-balances
were established. Following the 11 infusion periods, the amounts of amino acids at the duodenum resulting from the rations were measured. The daily amounts of leucine sufficient to meet the requirements of dairy cows [600 kg body weight BW]
for maintenance alone and for maintenance plus 15, 20, 25 or 30 kg milk day were 38.1, 101.1, 124.7, 148.3 and 171.9 g, respectively. These values corresponded with those calculated from dose–effect correlations 55.1, 111.5, 130.6, 150.0 and
169.4 g at zero N-balance. Daily methionine requirements, calculated at zero N-balances, were 6.3, 22.6, 28.4, 34.1 and 40.0 g. Again, these results corresponded well with estimations derived from dose–effect correlations 5.6, 22.7, 28.4, 33.1
and 39.8 g.
2000 Elsevier Science B.V. All rights reserved.
Keywords : Dairy cows; Leucine; Methionine; Amino acids requirements
1. Introduction strated, the same amino acids are essential for both
species. However, in ruminants, the amounts of In principle, the protein metabolism of ruminants
amino acids available at the duodenum are not at tissue level resembles that of non-ruminants. As
directly proportional to the corresponding amino Black et al. 1957 and Downes 1961 demon-
acids in the ration, but depend on the complex nitrogen metabolism in the rumen. Due to meth-
odical problems, our knowledge of maintenance
Corresponding author. Tel.: 149-531-596-440; fax: 149-531-
requirements, absorbability and intermediary utilisa-
596-376. E-mail address
: peter.lebzienfal.de P. Lebzien
tion of individual amino acids in dairy cows is
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 0 8 - 6
156 M
. Iburg, P. Lebzien Livestock Production Science 62 2000 155 –168
limited MacRae and Beever, 1997 and does not N-balance is zero and no other nutrient has a limiting
readily allow quantification of the requirements for effect.
the individual amino acids at the duodenum. Schwab 1996 described three approaches that have been
used to estimate the amino-acid requirements of
2. Materials and methods
lactating dairy cows; ‘‘factorial’’ mathematical, ‘‘direct dose–response’’ and ‘‘indirect dose–re-
2.1. Experimental design sponse’’, and discussed the advantages and disadvan-
tages of these methods. For a fuller description of the Nine lactating dairy cows of the German Black
different methods, the reader is referred to Schwab and White breed in the mid-stage of lactation, with a
1996. daily milk production averaging 20–25 kg fat-cor-
The objective of the present study was to de- rected milk FCM at the beginning of the trial, were
termine the leucine and methionine requirements of used. Mean liveweight of the animals was 598
622 lactating dairy cows at the small intestine. A method
kg. The animals were fitted with ruminal cannulas was established to measure the effects of defined
and simple
T-type cannulas
in the
proximal deficiencies of single amino acids at the duodenum
duodenum, positioned between the pyloric valve of in otherwise well-balanced rations on milk yields and
the abomasum and the entrance of the bile duct. The N-balances ‘‘three-dimensional dose–effect correla-
duodenal cannulas had an inner diameter of 20 mm tions’’.
and were exteriorised caudally to the ribs. They were For this purpose, the protein- and energy require-
made of polyethylene and the base was a disk with a ments of the animals were met by a combination of
diameter of 60 mm. 2.2. Feeding
1. regular feeding and 2. infusion of amino acids and hydrolysed sucrose
Over a period of 13 weeks, all animals were into their proximal duodenum.
offered rations that were sufficient either for mainte- nance requirements plus 17 kg milk day Ration 1
Afterwards, the results were compared with the or 15 kg milk day Ration 2, regardless the actual
results from factorial calculations Rohr and Lebzien, milk yields of the animals, which were higher. The
1991 and calculations from changes in N-balance. composition of the rations is given in Table 1.
In the latter case, amino-acid requirement for a given It was intended to give energy and protein suffi-
milk protein yield is defined as the lowest amount of cient for approximately 7 kg of FCM by infusion.
amino acid at the duodenum that is required to Thus, animals had to be divided into two groups,
realise this protein yield, under the condition that based on their milk yield during the week prior to the
Table 1 Feed intake per cow and day
Ration 1 Ration 2
Dry matter kg
a
Concentrate 6.5
60 6.0
60 Grass silage 40 DM
6.0 60.2
5.4 60.1
Grass hay 1.0
60 1.0
60 Organic matter kg
12.22 60.21
11.23 60.16
Dig. organic matter kg 9.10
60.16 8.34
60.12 Metabolisable energy MJ
146 62.6
136 61.9
Net energy MJ 88.1
61.6 82.2
61.2 Nitrogen g
370 342
a
The concentrate was a mixture g kg of barley 260, wheat 300, soy bean meal 150, dried sugar beet pulp 250, soy bean oil 20 and mineral supplement 20.
M . Iburg, P. Lebzien Livestock Production Science 62 2000 155 –168
157
0.75
infusion period. Animals yielding 23 to 25 kg of BW
and an energy requirement for milk pro- FCM received ration 1 sufficient for maintenance
duction MJ NEL day as [0.37 3 milk fat content
plus 17 kg of FCM, whereas, in cases where the 1 0.21 3 protein
content 1 0.95] 3 milk
yield was below 23 kg 20–23 kg FCM day, yield kg. Differences between the actual energy
animals received ration 2 sufficient for maintenance requirement of the animals and that supplied by the
plus 15 kg of FCM. diet was met by infusion of hydrolysed sucrose into
By withholding defined amounts of leucine and the duodenum 330 to 2100 g day. The sucrose was
methionine from the infusion solutions, effects on hydrolysed by invertase Sigma, Deisenhofen, Ger-
the N-balances allowed an estimation of the require- many at pH 4.5 and 55
8C for 20 min. The NEL ments for leucine and methionine.
content of sucrose was calculated as 9.9 MJ kg 16.5 N-balances were calculated as N-balance
5 N-in- MJ gross energy kg sucrose
3 0.6 [efficiency for take
2 N-excretion faeces, urine, milk. Productive milk production].
N was calculated as the sum of N excreted via the Differences between the actual amino acid require-
milk and retinated resp. mobilised body protein-N. ment and the amino acid supply by the ration were
The animals received their ration in two equal met by continuous infusions of enzymatically hydro-
meals at 7.30 am and 3.30 pm. The first two weeks lysed caseine Megglysat CB, Meggle, Wasserburg,
of the experiment served as an adaptation period. Germany and amino acids Welding, Frankfurt,
Germany and Degussa, Hanau, Germany into the 2.3. Infusions
proximal duodenum via the duodenal cannulas. The basis for the calculation of the amount of individual
It was our intention that the rations would not be amino acids needed at the duodenum was the net
sufficient to fulfil the total requirements of the requirement for amino acids, defined as the amount
animals for energy and amino acids. The requirement of amino acids required for maintenance plus the
gap that arose during the trial periods was closed by amount of amino acids excreted with the milk: The
infusing appropriate amounts of single nutrients net requirement for amino acids was calculated by
hydrolysed sucrose, hydrolysed caseine, amino estimating the net requirement for N according to
acids into the proximal duodenum. Rohr and Lebzien 1991 and taking into account the
Calculations for energy- and amino-acid require- mean amino-acid composition of endogenous secre-
ments were performed on a weekly basis. Fresh tions, tissue- and milk protein. Net nitrogen require-
infusion solutions were prepared daily by diluting the ment g was calculated as: urinary nitrogen excreted
amino acids and the hydrolysed caseine in 1700 ml UN
1 faecal nitrogen excreted FN 1 surface-
e e
of water at 50 638C. This solution was transfered
loss nitrogen VN 1 milk protein-N, UN g day
e
into an infusion-bin containing 5000 ml of water, was calculated as 5.92 log BW
2 6.76; FN g day
e
supplemented with 40 ml of propionic acid, to avoid was estimated as 2.91
3 kg dry matter intake DMI
0.75
microbial contamination. After that, the hydrolysed and VN g d as 0.018
3 BW . In addition, in-
sucrose was added and dissolved by gentle stirring of testinal absorption of the amino acids and intestinal
the solution. The osmolality of the solution was utilisation of the amino acids absorbed were included
approx. 300 mOsmol kg. The solutions were infused in the calculations Rohr and Lebzien, 1991.
using a tube pump IKA Labortechnik, type PA-SF. Prediction of intestinal supply of amino acids was
The tubes were fixed to the animals using non- according to Rohr and Lebzien 1991 and compared
irritant breast harnesses. The mean pump capacity with calculations by Hvelplund and Madsen 1989.
was 306 ml h, resulting in a total infusion time of 22 The equation for the calculation of duodenally
h per day. The remaining 2 h were used for available individual amino acids Rohr and Lebzien,
maintenance of the technical equipment. 1991 reads:
The total energy requirement of the animals was calculated according to GfE 1986, giving an energy
AA g day 5
x
requirement for maintenance [MJ net energy for
[27.83 DOM kg day 1 0.34 NI gday 2 2.34 DMI kgday 2 26.3 3 a 3 b
0.75
]]]]]]]]]]]]]
lactation NEL day] as 0.293 3 kg body weight
c
158 M
. Iburg, P. Lebzien Livestock Production Science 62 2000 155 –168
where, AA 5relevant amino acid; DOM5digestible
digestibility of nutrients was calculated from differ-
x
organic matter; DMI 5dry matter intake; NI5feed-N
ences in nutrient flow in digesta at the various sites intake exclusive urea-N; a
5AA2nitrogen fraction of the gastrointestinal tract. Estimation of the amino
of the non-urea-N in the duodenal chyme 50.73;
acids was performed according to the procedure of b
5N from relevant amino acid as a percentage of Spackmann et al. 1958, as modified by Weidner
the total AAN and c 5N content of the individual
and Eggum 1966, using an automated amino acid amino acids .
analyzer Beckmann System 6300. 2.4. Experimental groups
2.5. Statistical methods The nine animals served as a trial group, from
The effects of different amounts of the respective which, every week, two animals were allocated to
amino acids on the N-balances allowed an estimation the balance trials for five days. Selection of the
of the actual amino acid requirements of the animals. animals was based on their state of health, feed
This was undertaken, on the basis of the data intake and performance. During this time, leucine or
derived, for leucine and methionine. methionine were withhold alternatively from the
A three-dimensional surface graph was chosen for infused solution, and faeces, urine and milk were
presentation of the data, with the x-axis representing collected separately to establish N-balances. The
the amount of nitrogen in the milk, the y-axis giving cows were milked twice daily. The urine was
the amount of the relevant amino acid at the delivered into 40-l bins containing 250 ml of hydro-
duodenum and the z-axis showing the N-balance chloric acid. Faeces and urine were weighed and
resulting from the combination of x- and y-values. In subsampled daily for analysis. Composite samples of
this way, the results of various infusion trials dealing the feed and left-over were freeze-dried, ground in a
with the same amino acid were combined. Spline 1-mm screen ultracentrifuge-mill, and analyzed for
interpolation of the derived data was carried out to organic matter, crude protein, crude fibre, ether
interpolate a function for the two variables, N in the extract and ash Naumann and Bassler, 1976. Urine
milk and the amount of amino acids at the and milk samples were analyzed for nitrogen using
duodenum, onto a rectangular grid by using the SAS the Kjeldahl-method Naumann and Bassler, 1976.
G3GRID procedure SAS GRAPH User’s Guide, Milk weights were recorded daily at each milking.
1988. Milk samples of morning and afternoon milkings
were taken on day two and day five of the infusion period, preserved with potassium dichromate and
3. Results and discussion
