Department of Animal Husbandry, Alaska Agric~ltt~ral Experlment

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Department of Animal Husbandry, Alaska Agric~ltt~ral Experlment Powered By Docstoc
					C O M P A R A T I V E U T I L I Z A T I O N OF A L F A L F A - B R O M E G R A S S P A S T U R E
           UNDER ROTATIONAL AND DAILY STRIP GRAZING 1

                      A. L. BRUNDAGE AND W. J. SWEETMAN
     Department of Animal Husbandry, Alaska Agric~ltt~ral Experl:ment Station, _Palmer

                                          SUMMARY
    The efficiency of herbage utilization from alfalfa-bromegrass (M. falcata and
B. inermis) pasture under rotational and strip-grazing management was compared
for three grazing seasons. The expression of increased efficiency as increased carrying
capacity was precluded by restricting grazing, so that the cows on each system had
equal opportunity to utilize the available herbage. Under these restrictions, dairy
cows at a moderate level of milk production utilized alfalfa-bromegrass pasture ahnost
as efficiently under rotational grazing as under strip grazing.


     Herbage utilization has been called the chief problem of grassland manage-
merit (5). Medicago falcata is presently the only winter-hardy alfalfa available
for use in interior Alaska, and Bromus inermis is a highly productive grass
u n d e r Alaskan conditions. This study is a continuation of investigations being
carried out to determine the effectiveness of increasing intensities of pasture
m a n a g e m e n t on the efiqeieney of herbage utilization.
     Reports in the literature suggest that increased efficiency of herbage utiliza-
tion is expressed as increased c a r r y i n g capacity per acre, with little or no a p p a r e n t
effect on the level of production maintained by the individual animals. B r u n d a g e
and Petersen (1) and Davis and P r a t t (~t), comparing continuous grazing with
strip and rotational grazing, respectively, found that the intensity of grazing
control did not affect animal production significantly.
      Controlled grazing resulted in more efficient herbage utilization, however,
because it provided for salvage of material in excess of grazing needs. I t t n e r
et at. (10) and ];(eycr et at. (t3) found insignificant differences in rate of gain
for beef steers rotationally grazing, strip grazing, or soiling alfalfa. The total
yield of beef per acre was highest under the soiling system (9, 10, 13). Total pro-
duetion of beef was comparable under rotational and strip grazing when periods
on the rotated paddocks were limited to f r o m five to seven days. When the time on
each paddock was increased to f r o m eight to 12 days, production was higher under
strip grazing. Holmes et at. (6, 7) obtained 20-40% increases in production per
acre when cows were dose-folded, compared to rotational grazing. They attributed
these increases to increased efficiency of utilization. Hosking and Line (8) found
that daily herbage allocations gave 15 % more economical use of available pasture
than did four-day rotational grazing. They found no significant differences in
milk yield, live weight changes, or d r y m a t t e r intakes which could be attributed
to the grazing systems.

     Received for publication July 21, 1958.
    1Approved for publication by the Director, Alaska Agricultural Experiment Station,
Palmer, Alaska, as Technical Publication 10.
                                               1777
1778                   A. L. B R U N D A G E   A N D W . J. S W E E T M A N



    Brundage and Sweetman (2) obtained 63% greater production from mature
oats and peas pasture when it was offered in twice-daily breaks, compared with
uncontrolled access. Controlled grazing provided increased carrying capacity
with no increase in daily milk production per cow. Procter and tIood (14) ob-
tained 25% greater utilization of herbage with close-folding, compared with in-
tensive rotational grazing. Restricting grazing so that each group had equal
access to the available herbage, Brundage et al. (3) found little difference in
animal production or efficiency of utilization of a moderately productive brome-
grass pasture rotationally or strip grazed. Ivins et al. (11) have recently sug-
gested that often the potential production of the grazing animals, rather than
of the pasture, is the limiting factor, regardless of the pasture type or treatment.
They stressed the importance of dry matter yields supplemented with palatability
and digestibility data.
    In the experiments discussed above, increased efficiency of pasture utilization
has been obtained through increased carrying capacity of the sward, with little
or no increase in individual level of production. It is conceix~able, however, that
more intensive utilization of grassland might be expressed in higher levels of pro-
duction per grazing animal, with no increase in the number of animals nmin-
rained. The experiment to be described in this paper was designed to maintain
equal carrying capacity under two management systems, rotational and strip
grazing. Any difference in efficiency of herbage utilization nmst be expressed in
terms of increased production per animal unit.

                              EXPERIMENTAL           PROCEDURE

    Seven acres of alfalfa-bromegrass pasture were used in 1955, 1953, and 1957
to compare the efficiency of herbage utilization under rotational and strip grazing.
The field was divided down the long axis into two equal areas. One area was
further subdivided into three equal paddocks and rotationally grazed. The other
was daily strip grazed, using portable electric fences (3). Grazing under both
systems was restricted, so that each group had equal opportunity to utilize tile
available herbage. It was necessary to remove both groups at intervals, to allow
sufficient recovery of the pasture for further grazing. Management systems re-
mained the same for each area during all 3 yr.
    Different groups of eight milking dairy cows were matched into four pairs
at the initiation of grazing each year. One member of each pair was assigned at
random to one management system, the other cow going to the second system.
They remained under the assigned management programs for the entire grazing
season. One pair was removed from the experiment at the completion of the
second grazing cycle in 1956, because of different expectant calving dates.
    The cows were weighed prior to leaving the barn for pasture after the morning
milking. They were allowed water from a common trough after weighing, thereby
reducing the variable of water fill in the weight data. Weights taken at the be-
 ginning and end of each complete grazing cycle (once over the pasture) were
used to compute weight changes and maintenance requirements. 5[ilk production
                           U T I L I Z A T I O N OF A L F A L F A - B R O M E G R A S S P A S T U R E                 1779

was recorded twice d a i l y a n d s a m p l e d at t e n - d a y i n t e r v a l s for b u t t e r f a t tests.
A l i m i t e d q u a n t i t y of g r a i n was g i v e n o~le p a i r of cows i n 1955. None of the
other a n i m a l s received g r a i n s u p p l e m e n t a t i o n at a n y time while on e x p e r i m e n t .
These d a t a were used to c o m p u t e T D N u t i l i z a t i o n a c c o r d i n g to the p r o c e d u r e of
K n o t t et at. ( 1 2 ) .
                                              RESULTS AND DISCUSSION

      A n i m a l p r o d u c t i o n , the o n l y m e a s u r e of r e l a t i v e h e r b a g e utilizatio'n u n d e r
the two m a n a g e m e n t systems, is s m n m a r i z e d ( T a b l e 1). E a c h system s u p p o r t e d
th~ same n u m b e r of a c t u a l cow-days on p a s t u r e because of the r e s t r i c t i o n i n design
imposed. T D N p r o d u c t i o n p e r acre was h i g h e r each y e a r u n d e r s t r i p grazing,
b u t differences were small the last 2 yr. of the e x p e r i m e n t . The large differences
e v i d e n t i n 1955 reflect m i l k p r o d u c t i o n differences for one p a i r of cows. A l t h o u g h


                                                         TABLE 1
                   Prod.uction from alfalfa-bromegrass pastl~re grazed 3 yr. under
                                  the same two ~aanage,ment system*is
                                        1955                            1953                               1957
                                 Rotational Strip                Rotational Strip                  Rotational    Strip
                                  grazing grazing                 grazing    grazing                grazing     grazing
Number of cows                         4                4                4"               4"               4         4
Acres                                  3.6              3.45             3.6              3.45             3.6       3.45
Number of grazing cycles               4                4                4                4                3         3
Days on pasture                       75               75               91               91               69        69
Average daily production
  per cow
   FCM (lb.)                          28.10            33.18            29.06            27.72            26.05     24.27
  Weight gain (lb.)                    0.78             1.46              1.58         1.49                0.49      0.72
  Weight loss (lb.)                    0.33             0.14             ................                  0.06      0.15
Average daily grain
  ration per cow (lb.) b                5.1              5.1             ................................
Production per acre
  from pasture ¢
  TDN (lb.)                       1,622            2,061            2,094            2,198              1,498     1,546
  Standard cow-days                 101              129              131              137                 94        97
      " One cow under each system was removed at the completion of the second grazing (48 days).
      b One cow under each system was fed grain (67.3% TDN) the first year.
      c Calculated according to the method of Knott et al. (12).

n e a r l y equal i n level of p r o d u c t i o n at the s t a r t of the e x p e r i m e n t , the cow rota-
t i o n a l l y g r a z i n g failed to m a i n t a i n p r o d u c t i o n at a level c o m p a r a b l e to its mate.
W h e t h e r this is a reflection on the m a n a g e m e n t system or on the cow i n v o l v e d
is n o t definitely k n o w n . The lowered T D N p r o d u c t i o n of the p a s t u r e i n 1957
was the r e s u l t of a severe a n d p r o l o n g e d d r o u g h t t h a t s p r i n g a n d e a r l y s u m m e r .
       D a i l y m i l k p r o d u c t i o n was more unifo~rnI u n d e r s t r i p grazing. Milk p r o d u c -
t i o n was cyclic on the r o t a t e d p a s t u r e , r i s i n g w h e n a new p a d d o c k was e n t e r e d
a n d f a i l i n g as the a v a i l a b l e h e r b a g e was d e p l e t e d t h r o u g h c o n s u m p t i o n a n d foul-
ing. E v e n t h o u g h the paddocks o f t e n a p p e a r e d severely depleted before the
a n i m a l s were moved, total p r o d u c t i o n was c o m p a r a b l e or s u p e r i o r to t h a t on the
more u n i f o r m regime. The time s p e n t on a n y one p a d d o c k v a r i e d f r o m f o u r to
n i n e days.
1780                     A. L. BRUNDAGE AND W. J. SWEETMAN


    Therefore, these data fail to show a consistently large difference in efficiency
of herbage utilization between rotational and strip grazing. B u t caution must
be used in deriving general statements from these results. The rotated animals
were often required to remain on paddocks which were seriously depleted, to
satisfy the requirement that each group be given the same opportunity to graze
comparable areas. Altho~lgh good herdsmanship would demand their rotation
at these times, they were able to recover when moved to a new paddock and main-
tained their total production at a level comparable to the strip-grazed group. As
Ivins et al. (11) suggested, the potential productive level of the grazing animals,
and no't the pasture, may have been a limiting factor. The rotation interval (from
four to nine days) may have been too short to deplete the animals sufficiently
before they moved to a new paddock, l~inally, the productive potential of the
pasture may have been such that a good rotation system was nearly as efficient
as strip grazing. Efficiency of utilization is a function of the potential producing
ability of the grazing animals and the pasture being grazed. As the level of either
or both rises, more intensive grazing may be necessary to maintai~ a comparable
level o'f efficiency.
                                      REFERENCES
 (1) BP~UNDAGE,A. L., AND PF~TERSEN, W. E. A Comparison Between Daily Rotational Grazing
           and Continuous Grazing. J. Dairy Sci,, 35: 623. 1952.
 (2) BRUNDAGE.,A. L., AND S~VE~:TI~IAN,W. J. Unpublished data. 1954.
 (3) BRUNDAG]g,A. L., S%¥'E.ET),L~N, W. J., HODGSON, H. J., AND BULA, R. J. The Utilization
           of Smooth Bromegrass (Bro~nus i~ler.mis) under Rotational and Strip Grazing Systems
           of Pasture Management. I. Animal and Pasture Production. J. Dairy Sci., 39: 280.
           1956.
 (4) D.xvIS, R., AND P~.A~'T, A. D. t~otational vs. Continuous Grazing with Dairy Cows. Ohio
           Agr. Expt. Sta., Research Bull. 778. 1956.
 (5) I t o L ~ , s , W. High Milk Yields per Acre from Grassland. J. Brit. Grassland Soc., 9:
           17. 1954.
 (6) ttOL~ES, W., WAITS, R., F~aGUSS0N, D. L., :xxI) CAMPBELL, J. I. Studies in Grazing
           Management. I. A Comparison of the Procluetion Obtained from Close-Folding and
           Rotational Grazing' of Dairy Cows. J. Agr. Sci., 40: 381. 1950.
 (7) HOLLIES, W., WAITE, R., FEI~GUSSON, D. L., AND M~t'LusKY, D. S. Studies in Grazing
           Management. IV. A Comparison of Close-Folding and Rotational Grazing of Dairy
           Cows on Intensively Fertilized Pasture. J. Agr. Sci., 42: 304. 1952.
 (8) ttOSKINS, ZENA D., AND LINE,, C. Comparison of Two Methods for the Controlled Grazing
           of Dairy Cows. J. Brit. Grassland Soe., 11: 1.°,0. 1956.
 (9) HITL1,, J. L., MEYEr, J. It., LOFG~E~N, G. P., ,~ND ST~OTHER, A. Studies on Forage Utili-
           zation by Steers and Sheep. J. A,ai.mal Sci., 16: 757. 1957.
(10) ITTNER, N. R., LO*G~EEN, G. P., AND MEYER, J. It. A Study of Pasturing and Soiling
           Alfalfa with Beef Stee~'s. J. A n i m a l Sol., 13: 37. 1954.
(11) IvINs, J. D., DrLNOT, JEAn,', A~:D DAVIS0N, J. The Interpretation of Data of Grassland
           Evaluation in RelatioIt to the Varying Pote~tial Outputs of Grassland and Livestock.
           J. Brit. Grassland Soe., 13: 23. 1958.
(12) KNO~% J. C., HOBGSON, R. E., AND ELLINGTON, E. V. Methods of Measuring Pasture
           Yields with Dairy Cattle. Washington AgE Expt. Sta., Bull. 295. 1934.
(13) M~Y~a, J. H., L O F a a ~ , G. P., AN~ I'r~NER, N. R. Further Studies on the Utilization
           of Alfalfa by Beef Steers. J. 3ni,mal Sei., 15: 64. 1956.
(14) P n o c ~ , J., A~D HOO~, A. E. M. The Close-Folding of Dairy Cows. II. J. Brit. Grass-
            land Soe., 8: 239. 1953.

				
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