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Effects of supplements of urea and

minerals on steers fed maize silageT. F. Reardon

a

aRuakura Animal Research Station, Ministry of Agriculture and

Fisheries, P.B., Hamilton, New Zealand

Version of record first published: 18 Jan 2012.

To cite this article:T. F. Reardon (1980): Effects of supplements of urea and minerals on steers fedmaize silage, New Zealand Journal of Experimental Agriculture, 8:2, 101-104

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2/5

N.Z. Journal

of

Experimental Agriculture 8 (1980): 101-4

101

ffects of supplements of urea and minerals on steers fed

maize silage

T. F. REARDON

Ruakura Animal Research Station, Ministry

of

Agriculture and Fisheries,

P.B., Hamilton, New Zealand

A mineral mixture (Ca, P, Na, Mg, S, Cu, Co, Zn, Mn, I, Fe) and urea (10 g/kg silage

DM) were added separately and in combination to sole diets

of

maize silage (33 DM)

fed to 16-month-old beef steers initially weighing 303

kg.

Urea increased silage

DM

intake from 7.3 to

8.1

kg/day and increased carcass gain from 0.20 to 0.48 kg/day.

Minerals increased silage DM intake from 7.1 to 8.3 kg/day and increased carcass gain

from 0.22 to 0.46 kg/day with an indication (P < 0.1)

of

a positive interaction between

urea and minerals on both intake and carcass gain. There was a significant interaction on

live-weight gain with urea improving gain from 0.77 to 1.43 kg/day in the presence

of

and from 0.37 to 0.80 kg/day in the absence of, supplementary minerals. '

Keywords

Zeal mays

L., silage, steers, weight gain, urea (nutrient), minerals

(nutrient)

INTRODUCTION

In contrast to the North American (Goodrich

Meiske 1971) and British and European industries

(Mal terre 1976) the New Zealand beef industry uses

little maize silage. Low returns for beef, year-round

availability

of

pasture dry matter (DM) at less than one

half

of

the cost

of

maize silage DM (Hutton 1973), and

the need to correct protein and mineral deficiencies

of

maize have limited the use

of

maize silage. However, a

low-cost system

of

protein and mineral supple

mentation, consistent with reasonable levels

of

animal

production, could enable maize silage to contribute to

beef production in the warmer areas

of

New Zealand.

The present study examined the effects

of

supplements

of

minerals and urea added separately, or

in combination, to maize silage when fed to

beef steers.

MATERIALS AND

METHODS

Forty-five Angus-Hereford crossbred steers, aged

about

16

months, were divided into groups

of

5 by

stratified randomisation using live weight. They were

held on a sawdust pad with continuous access to feed

Received 30

july

1979;

revision

16

November 1979

and water. During days

1-9,

all groups were offered a

diet

of

hay and maize silage with reducing proportions

of

hay. On day 10, one group was slaughtered after a

24-h fast and carcass weight was recorded to establish a

regression

of

carcass weight on unfasted live weight.

From day 11, the remaining groups formed 2 replicates

of

a 2 x 2 factorial experiment in which maize silage

was offered to appetite (at least

5

refusals) together

with urea at levels

of

0 or

10

g/kg silage

DM

and with a

mineral mixture at levels

of

0 or 22.5 g/kg silage DM

added daily as fresh silage

was

offered. Levels

of

urea

supplementation were progressively increased from 4

to 109/kg silage D M from day 11 to day

17.

The

mineral mixture, offered at the full rate from day 11,

consisted

of

(g/kg mineral mixture): bone flour (627),

calcined magnesite (96), common salt (189), finely

ground sulphur (63), and trace minerals (25). The

trace mineral mixture consisted

of

(g/kg trace mineral

mixture):

CuS0

4

.5HP (70.6), CoS0

4

.7HP (0.6),

ZnS0

4

.7Hp

(393.3),

MnS0

4

.4Hp

(280.9), KI (1.6),

FeCI

3

.6Hp (252.8). Daily silage samples were bulked

into weekly samples for analysis.

Nitrogen was determined by a macro Kjeldahl

digestion using K

2

SO/Se

catalyst and steam

distillation. Na, K, Ca, Mg, and P were determined by


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102

N.Z. Journal of Experimental Agriculture, Vol. 8,

1980

atomic absorption spectrophotometry after digestion in

nitric:perchloric acid

(2:

1) with wet digestion being

followed by reduction to molybdenum blue for the

determination of P. Sulphur

was

determined

gravimetrically as BaS0

4

after oxidation in an oxygen

bomb.

Between days 62 and 72,

all

animals were

slaughtered after

24

h without feed. Rate oflive-weight

change was calculated as the regression coefficient of

weight (recorded weekly) on time from days 16 to 57.

Carcass gain was calculated from actual carcass weight

when slaughtered and carcass weight on day 10

estimated by the regression of carcass on live weight in

the initial slaughter group. Variation between animals

within replicates was used as the measure of

experimental error for gains of live weight and carcass

weight.

R SULTS

Compositions

of

feed and supplements are presented

in Table 1. Dry matter percentage

of

maize silage

by

toluene distillation (33.1 ) was slightly higher than

that found

by

oven drying (32.6%). The Kjeldahl N

content of the mineral mixture was higher than

anticipated when the mixture was formulated.

Intake of silage DM was increased

by

the addition of

minerals

(7.1

v.

8.3

kg/day, P

< 0.001)

and

of

urea

7.3 v. 8.1 kg/day, P

~

o

O:OA

2

0

o

O - - - - - - - r - - - - - ~ - - - - - - ~ - - - - - - ~

6 7 8 9

10

Silage OM

(kg/day)

Fig. 1 Mean silage intake for groups of 5 steers and rates of

gain

of

live weight (solid symbols) and carcass weight (open

symbols) on maize silage diets without supplements

(0, . ,

with urea only

A ,

with minerals only (V,. .. ), and with

both urea and minerals

(0, . ) .

Line relates intake by a 300

kg

steer

to

rate

of

live-weight gain estimated from National

Research Council (1976) tables assuming net energy values

of

6.53 and 4.14 MJ/kg OM for maintenance and gain

respectively.


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104

N.Z. Journal of Experimental Agriculture, Vol. 8, 1980

diets supplemented with NPN to higher levels of crude

protein (up to 90 g digestible crude protein/kg DM)

(Cottyn et al. 1977).

Part of the improvement in rates of gain as a result

of

supplementation can be attributed

to

increased

intake (Table 2). In Fig. 1, intake of silage DM and

rates of gain of live weight and carcass are plotted

together with the relationship between live-weight

change and dry matter intake estimated (National

Research Council 1976) for a 300 kg steer assuming

net energy contents of maize silage of 6.53 and 4.14

MJ/kg DM for maintenance and gain respectively. In

the present data, an increase in daily DM intake of 1 kg

was associated with increases in daily gains of about 0.5

and 0.25

kg

respectively in live weight and carcass

weight whereas the theoretical relationship (Fig. 1)

indicates an increase

of

about 0.2 kg oflive-weight gain

per kilogram of extra DM. This additional

improvement in animal performance, beyond that

attributable to increased intake, represents

improvement in efficiency of utilisation from a

deficiency situation up to a situation where utilisation

of the energy content of maize probably approaches

maximal values.

Some reservations must be held on the reliability

of

live-weight gain measured over a relatively short

period such as that used in the present experiment. In

addition,

all

groups lost weight during adaptation to the

experimental conditions and rations (Table

2, days

1-16). The results for carcass gain are less equivocal

with the largest source of error being the estimation of

initial carcass weight from live weight, measured

before differential feeding began. Thus, the low

proportion of carcass gain in live-weight gain (Table 2)

possibly indicates that live-weight gain was

overestimated in

all

groups.

Rate of carcass gain provides a convenient measure

for the practical assessment of these results. In a

preliminary report (Reardon

et al.

1976), the mineral

mixture and urea were estimated to each add 0.3 cents

to the cost of a kilogram of silage DM but together

produced sufficient extra carcass, relative to

unsupplemented maize silage, to more than cover the

costs of their addition. However, at the assumed prices

of

3 c/kg DM for unsupplemented maize silage and

50 c/kg for carcass, total daily feed costs exceeded the

value of total daily carcass gains by a wide margin for

the unsupplemented group and

by

a narrow margin for

the fully supplemented group. At more favourable

relative prices for carcass and silage, the results in

Table 2 indicate that total feed costs of a fully

supplemented maize silage diet would be recovered

from the value of carcass gained. Evaluation of this

profit margin against non-feed costs and against profits

from alternative means of producing beef and of using

the maize crop

is

beyond the scope of this discussion.

Acknowledgments

Mr W. Ferguson for the feeding and care of the animals;

Mr R. P. Newth and Mr D. Karl for chemical analyses.

REFERENCES

Board on Agriculture and Renewable Resources 1976: Urea

and other non-protein nitrogen compounds in animal

nutrition . Committee on Natural Resources, National

Research Council, National Academy

of

Sciences (USA).

Cottyn,

B.

G.; Boucque, Ch. V.; Aerts, J. V.; Buysse, F. X.

1977: The use

of

non-protein nitrogen

in

rations for

intensive beef production. In Protein and Non-Protein

Nitrogen for Ruminants .

Proceedings

o f

United Nations

Symposium, Geneva, January 1977. Pergamon Press.

Ensminger, M. E.; Olentine Jr.,

C.

G. 1978: Feeds

Nutrition - Complete . Ensminger Publishing Co.,

Clovis, California.

Essig,

H.

W. 1968: Urea-limestone-treated silage for beef

cattle. Journal of nimal Science 27: 730-8.

Goodrich, R. D.; Meiske, 1. C. 1971: The use of corn silage in

feedlot rations. Pp. 123-40. International Silage Research

Conference. Dec. 1971. National Silo Association (Inc.)

Cedar Falls, Iowa.

Hutton, J.

B.

1973: Developments

in

nutrition and

management, and their relation to the future of the New

Zealand dairy industry.

Proceedings ofRuakura Farmers

Conference: 220-32.

Hutton,

1. B.;

Rattray, P. V. 1976: The effect on dairy cows

and sheep performances of additives to high dry matter

maize silage.

Proceedings

of

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N.z.

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Jacobson, D. R.; Barnett, J. W.; Carr, S. B.; Hatton, R. H.

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Journal

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Johnson, R. R.; McClure, K. E. 1968: Corn silage maturity.

IV Effects on digestibility of corn silage in sheep. Journal

ofAnimal Science 27: 535-40.

Malterre, C. 1976: Different ways of utilizing the maize crop

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In

Improving the

Nutritional Efficiency of Beef Production . J. C. Tayler

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Communities, Luxembourg.

Moir, R. 1.; Somers, M.; Bray,

A.

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Institute Journal 3: 15-18.

National Research Council 1976: Nutrient Requirements of

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Beef Cattle. National Academy of Sciences. (USA).

Phipps, R. H.; Cramp, D. G. 1978: Maize silage with a non

protein additive as feed for autumn-calving cows.

Journal

of the British Grassland Society 33: 19-22.

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1976: Supplementing maize silage. Proceedings of

Ruakura Farmers Conference: 58-61.

Thorn,

E. R.

1977: The effect of plant population and time

of

harvest on growth of hybrid and non-hybrid maize.

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silage for intensive beef production.

3.

Nitrogen and

acidity as factors affecting the nutritive value of enslled

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effects of supplements of urea and

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