2002 Unified Beef Cattle and Range Research Report (continued)
Diet composition of beef cows grazing stockpiled native
range in southwestern North Dakota -- a progress report
T.J.Transtrom¹, C. Smith¹, W.W. Poland², L.J.Tisor² and J. Nelson²
Beef cows grazing stockpiled winter pastures typically lose body weight
and condition indicating that dietary supplementation may be necessary. Nonetheless,
cattle producers should use caution when designing supplementation strategies
based entirely upon the composition of the forage available for grazing. Although
forage and dietary composition are related, selective grazing may allow cattle
to consume a diet higher in quality than the total forage offered.
The objectives of this study were to determine the effects of advancing season
on the nutrient composition of forage available for grazing in stockpiled winter
pastures and to determine the effects of supplementation and advancing season
on fecal estimates of diet composition from cattle grazing winter pastures.
Stockpiling refers to the practice of allowing forage to accumulate without
grazing for use at a later time. Twenty-one mature crossbred cows grazed a predominantly
stockpiled native range from mid-November to late-January. The cows were randomly
allotted into four groups and assigned to one of four supplement treatments.
Treatments included an unsupplemented control (CON), or a barley-, pea- (PEA),
or sunflower meal-based supplement. Forage available for grazing (FOR) was sampled
every two weeks throughout the grazing period. Fecal samples were collected
monthly from cows in the CON and PEA treatments and used to estimate dietary
and fecal composition. Concentrations of total digestible nutrients (TDN), crude
protein (CP), acid- and neutral-detergent fibers, Ca, P, Mg and K in FOR were
not affected by advancing season. Although dietary supplementation did not affect
estimates of dietary digestible organic matter (DDOM), dietary crude protein
(DCP) or fecal nitrogen (FN), supplementation did increase fecal phosphorus
(FP). Advancing season affected DDOM, DCP, FN, and FP. Dietary crude protein
was highest in November, DDOM was lowest in December, FP was lowest in January
while FN declined across the season. There was no treatment by advancing season
interactions for either dietary or fecal composition. A gross comparison of
dietary to FOR composition implies that dietary estimates of energy and crude
protein were higher than comparable components in FOR. Nonetheless, DDOM and
DCP were positively correlated with TDN and CP, respectively. Although the nutrient
composition of FOR did not change, estimates of dietary composition varied across
the season. This may imply some level of dietary selectivity exhibited by beef
cows when grazing stockpiled native range in the late fall and early winter.
Producers should use caution when designing supplementation strategies based
entirely upon the composition of the forage available for grazing.
Introduction
Traditional economic opportunities in natural resource-based economies tend
to be decreasing due to lower profit margins particularly in agriculture. Ranchers
are a viable part of North Dakota's economic future and, with proper management
practices, they can become more profitable. Extended grazing seasons have been
shown to be a viable mechanism for decreasing operational costs while maintaining
overall production, thus increasing efficiency. Stockpiling of forage from perennial
plants during times of active growth for use at some other time of the year
is one means of extending the grazing season. However, at times the forage available
from stockpiling may not meet nutritional requirements so dietary supplementation
may be needed. Proper supplement formulation while grazing requires accurate
knowledge of the nutrients supplied from a base forage.
Objectives
- Determine the effects of advancing season on the nutrient composition of
forage available for grazing in stockpiled pastures during the winter.
- Determine the effects of supplementation and advancing season on fecal estimates
of diet composition from cattle grazing winter pastures.
Materials and Methods
Twenty-one summer-calving cows (BW = 1386 ± 142 lbs; BCS = 6.8
± .64 units) grazed a pasture of stockpiled predominately native range
in western North Dakota from Nov. 14, 2001 until Jan. 23, 2002.
Stockpiling refers to the practice of allowing forage to accumulate without
grazing for use at a later time. Cows were randomly allotted into four
groups which were then assigned one of four supplemental treatments.
Treatments included an unsupplemented control (CON; six head) and three
supplemented groups (five head/group). Supplemental treatments were
a barley-, field pea (PEA)- and sunflower meal-based pellet.
Supplemental treatments were chosen to supply additional energy and gradient
levels of rumen-degradable protein. Supplements were provided to
individual cows in the supplemental treatments three times a week.
Supplemental intake was limited to 3.0 lbs/hd per day or 7.0 lbs/hd per feeding.
Adjustments to supplement delivery based upon adverse environmental
conditions were not necessary during the study period.
Herbage available for grazing (FOR) was sampled at 14-day intervals
(6 sampling times) to detect changes in dry matter available for grazing.
For sampling purposes the pasture was divided into two halves (east and
west) and five sample sites were chosen per pasture half to represent major
range types. Two .25-m2 areas were
clipped per site per sampling date. At clipping, forage was physically
separated into grasses (G) and others (F). All forage was dried (55° C) to a
constant weight. Dry weights of G and F were then used to calculate forage
production per acre (Smith et al., 2002). Total forage available for grazing
(T) was the sum of G and F. Subsequently, all forage was pooled
within pasture half and sampling date and submitted for chemical analysis.
FOR was submitted to a commercial laboratory for determination of
crude protein (CP), acid (ADF) and neutral (NDF) detergent fibers, calcium
(Ca), phosphorus (P), magnesium (Mg) and potassium (K) using standard
analytical techniques.
Fecal samples were collected from cows in CON and PEA
treatments. Samples were collected at 28-day intervals starting with day 14
of grazing (3 sampling times). Near infrared spectroscopy (Texas
A&M University; analysis supported by Jeff Printz, Natural Resource
Conservation Service, USDA, Bismarck) was used to provide estimates of
dietary digestible organic matter (DDOM) and crude protein (DCP) plus
fecal nitrogen (FN) and phosphorus (FP).
FOR composition was analyzed for the effects of sampling date using
a completely random design. Dietary and fecal composition was
analyzed using a split-plot design. Treatment was a whole plot factor with
cow within treatment as an error term. Sampling date was a split-plot
factor. Linear regression was used to test for relationships between DDOM
and TDN and DCP and CP.
Results
Nutritional composition of FOR was not affected by advancing season (P >
.3; Figures 1, 2 and 3). The average nutrient profile for FOR was 52.6 1.29
% TDN, 4.9 .19 % CP, 47.5 1.44 % acid detergent fiber, 70.8 1.11 % neutral detergent
fiber, 0.65 .12 % Ca, 0.10 .01 % Mg, 0.07 .01 % P and 0.34 .07 % K across the
grazing period.
Figure 1. Effect of advancing season on concentrations of total
digestible nutrients (TDN) and acid (ADF) and neutral (NDF) detergent fibers
in forage available for grazing. (Click here
for an 8KB black and white graph.)
Figure 2. Effect of advancing season on concentration of crude protein
(CP) in forage available for grazing. (Click here
for a 6KB black and white graph.)
Figure 3. Effect of advancing season on concentrations of calcium (Ca),
phosphorus (P), magnesium (Mg) and potassium (K) in forage available for
grazing. (Click here for an 10KB black and white
graph.)
There were no treatment by sampling date interactions (P > .5) evident in
fecal estimates of DDOM, DCP, FN or FP. Furthermore, DDOM, DCP and FN were not
affected by supplementation (P > .4; Table 1). Supplementation (P = .06)
did increase FP. Advancing season (P < .01) affected all fecal estimates
of diet composition (Figures 4 and 5). Dietary crude protein was highest in
November, DDOM was lowest in December, FP was lowest in January and FN declined
across the season.
Table 1. Effect of dietary supplementationa on fecal estimates
of dietary digestible organic matter and crude protein and
fecal nitrogen and phosphorus.
---------------------------------------------------------------
CON PEA SEb
---------------------------------------------------------------
Dietary
Digestible organic matter (DDOM) 59.3 59.2 .29
Crude protein (DCP) 7.9 7.83 .153
Fecal
Nitrogen (FN) 1.30 1.33 .022
Phosphorus (FP) .203x .258y .018
---------------------------------------------------------------
aUnsupplemented and pea-based supplement treatments (CON and
PEA, respectively).
bStandard error of a mean.
x,yMeans within a row with different superscripts differ
(P = .06).
Figure 4. Effect of advancing season on fecal estimates of dietary digestible
organic matter (DDOM) and dietary crude protein (DCP). (Click
here for a 7KB black and white graph.)
Figure 5. Effect of advancing season on estimates of fecal nitrogen
(FN) and fecal phosphorus (FP). (Click here for
an 8KB black and white graph.)
Correlation analysis was used to test for relationships among FOR composition
and dietary estimates of energy and protein. Dietary digestible organic matter
and TDN (P = .02; R2 = .15; Figure 6) and DCP and CP (P = .01; R2
= .19; Figure 7) were positively correlated. These relationships were present
even though FOR composition did not vary, while dietary estimates declined,
across the grazing period. This may imply some level of dietary selectivity
was exhibited by beef cows when grazing stockpiled native range in the late
fall and early winter. Although encouraging, the lack of stronger relationships
between diet and FOR composition related to considerable variation amongst cows
in dietary estimates within a sampling date and the lack of substantial variation
across the season in FOR composition.
Figure 6. Relationship of dietary digestible organic matter (DDOM, %
DM) and total digestible nutrients in forage available for grazing (TDN,
% DM). DDOM = 11.46 + (1.35 * TDN); [P < .02; R2 = .15]. (Click
here for an 8KB black and white graph.)
Figure 7. Relationship of dietary crude protein (DCP, % DM) and crude
protein in forage available for grazing (CP, % DM). DCP = 34.05 + (8.45
* CP); [P < .01; R2 = .19]. (Click
here for an 8KB black and white graph.)
Conclusions
Stockpiling of forage from perennial plants during times of active
growth for use at some other time of the year is one means of extending the
grazing season. Although the nutrient composition of FOR did not
change, estimates of dietary composition varied across the season. This
may imply some level of dietary selectivity exhibited by beef cows when
grazing stockpiled native range in the late fall and early winter. While
dietary supplementation did not affect estimates of dietary energy, protein
or fecal nitrogen, supplementation did increase fecal composition of
phosphorus.
¹Department of Agriculture
and Technical Studies, Dickinson State University
²Dickinson Research Extension
Center, North Dakota State University
INDEX
Effect of nutrient restriction and compensation
on gestating beef heifers
A.M. Encinias1, H.B.
Encinias1, G.P. Lardy1, and C.S.
Park1
Two nutrient restriction and compensation strategies were tested in gestating
beef heifers. The results suggest compensatory growth can be imposed during
gestation without impaired performance of beef heifers or their nursing calf.
The objective of this research was to determine responses of an imposed compensatory
growth pattern during gestation in beef heifers on subsequent lactation potential
and to define effects of compensatory growth on maternal and calf performance.
In the first trial, gestating heifers were assigned to one of two treatments,1)
conventional (CON) or 2) a stair step compensatory development regimen (SS).
Treatments were imposed at 90 days of gestation. The CON diet was formulated
for a constant gain of 1.1 lbs/days. The SS treatment was formulated to provide
65% of metabolizable energy (ME) intake of CON heifers for 90 days, followed
by a 25% increase in ME intake for the next 90 days. There were no adverse effects
on maternal performance, lactation milk yield, or calf weight due to treatment.
In Trial 2, heifers were assigned to either CON or SS treatments. Diets for
CON heifers were formulated for 1.5 lbs/day gain. The SS diet was formulated
to provide 65% of the ME intake of the CON heifers for 120 days, followed by
25% more ME intake for the last 60 days. Neither maternal nor calf performance
was adversely affected by imposed compensatory growth in the last 60 days of
gestation. Although a compensatory growth response was noted in the SS heifer,
no differences in lactation yield were observed. These results suggest that
compensatory growth can be imposed during gestation without impaired performance
of beef heifers or their nursing calves. This development system has the potential
to lower heifer development costs, however, more research is needed to determine
the necessary extent and degree of restriction necessary.
Introduction
Successes in heifer development programs should be measured
in terms of lifetime productivity of the heifer. The ability of the female
to reproduce and lactate annually is critical in determining longevity in
the cow herd. Nutritional management, from conception through the
heifer's first parturition, will determine her ability to express her genetic
potential as a mature cow.
Dietary manipulation is a common means of cost reduction in
heifer development programs (Freetly et al., 2001). These manipulations
alter physiological processes related to mammary development,
reproductive function, and metabolism. Compensatory growth in heifer
development programs have been extensively studied in the postweaning to
breeding period (Ford and Park, 2001; Park et al., 2001). However, effects
of compensatory growth during gestation have not been extensively studied
or reported in scientific literature. The objective of this research was
to determine responses of an imposed compensatory growth pattern
during gestation in beef heifers on subsequent lactation potential and to
define effects of compensatory growth on maternal and calf performance.
Procedures
Trial 1. Twenty-four gestating Angus and Angus-cross heifers (initial
weight 900 ± 4.2 lbs) were used to evaluate a single step compensatory
growth regimen on prepartum growth, subsequent maternal and lactation potential,
and calf growth. All animals used in this research were cared for according
to protocols approved by the NDSU Institutional Animal Care and Use Committee
(IACUC). Heifers were grouped by ultrasound verified AI dates into six pens
(4 heifers/pen). At 90 days of gestation, heifers were assigned randomly to
one of two treatments (3 pens/treatment); treatments included conventional (CON)
and compensatory stair-step (SS) development programs. Treatments were imposed
at 90 days of gestation. The CON diet was formulated for a constant gain of
1.1 lbs/day. The SS treatment was formulated to provide 65% of metabolizable
energy (ME) intake of CON heifers for 90 days, followed by a 25% increase in
ME intake for the next 90 days. Diets for the CON and SS treatments are presented
in Table 1.
Three days of consecutive initial and final heifer weights were taken at the
beginning and end of each period. Heifers were also body condition scored at
these times. During the compensation period, heifers were weighed weekly. At
parturition, heifers were assigned a calving ease score (1= no difficulty, 2
= minor difficulty, 3 = major difficulty, 4 = Cesarean section, 5 = abnormal
presentation). Calf birth weight and vigor score (1 = nursed immediately, calf
was strong and healthy; 2 = nursed on its own, but took some time; 3 = required
some assistance to suckle; 4 = died shortly after birth; and 5 = dead on arrival)
were also recorded within two hours of birth. Milk production was estimated
three times during the lactation period. Milk production was quantified using
a portable milking machine. Heifers and their calves were separated the morning
of the milking. Heifers were restrained in a chute and oxytocin was administered
to stimulate milk letdown. Four minutes following oxytocin injection, heifers
were milked with a portable milking machine. Heifers and calves remained separated
for approximately 12 hours, at which time heifers were milked again. Milk production
was weighed and subsampled.
Trial 2. Thirty-six gestating Angus and Angus-cross heifers (initial
weight 1031 ± 22.9 lbs) were used to evaluate the effects of a stair step
compensatory development program on heifer development, maternal and lactation
performance, and calf growth. Procedures used in Trial 2 were similar to Trial
1 and all protocols were approved by IACUC. However, the length of nutrient
restriction was longer (120 days vs. 90 days) and the compensation period was
shorter (60 vs. 90 days). Diets used in Trial 2 are given in Table 1. Diets
for CON heifers were formulated for 1.5 lbs/day gain. The SS diet was formulated
to provide 65% of the ME intake of the CON heifers for 120 days, followed by
25% more ME intake for the last 60 days.
Table 1. Composition and nutrient analysis of conventional and
stair-step compensatory growth diets fed in Trials 1 and 2.
-------------------------------------------------------------------
Treatment Period
---------------------------------
Restriction Re-Feeding
-------------- -------------
CON SS CON SS
-------------------------------------------------------------------
Trial 1
Ingredients, % DM basis
Brome Hay 70.8 68.6 69.2 34.7
Dry Rolled Corn 15.3 2.2 17.0 42.7
Soybean Meal 7.9 23.2 7.8 2.4
Desugared Molasses 5.0 5.0 5.0 5.0
Sunflower Seeds - - - 14.2
Vitamins and Mineral Premix 1.0 1.0 1.0 1.0
Nutrient Levels, Calculated
Metabolizable Energy, Mcal/d 20.4 13.3 24.2 30.3
Nutrient Levels, Analyzed
Crude Protein, % 21.8 27.2 21.2 21.3
Trial 2
Ingredients, % DM basis
Alfalfa Hay 46.5 66.2 50.0 20.0
Dry Rolled Corn 44.3 20.0 42.0 59.0
Soybean Meal 3.2 7.8 2.0 2.5
Desugared Molasses 5.0 5.0 5.0 5.0
Sunflower Seeds - - - 12.5
Vitamins and Mineral Premix 1.0 1.0 1.0 1.0
Nutrient Levels, Calculated
Metabolizable Energy, Mcal/d 20.4 13.3 23.0 29.9
Nutrient Levels, Analyzed
Crude Protein, % 15.3 19.1 15.3 14.4
-------------------------------------------------------------------
Results
Trial 1. Energy restriction decreased ADG, body weight, and BCS in SS
heifers compared to CON (P < 0.05; Table 2) at day 180 of gestation. At the
end of the compensation period, SS heifers had similar weights and BCS compared
to CON. Calving ease, calf vigor, and birth weight was similar for SS and CON
(P > 0.16; Table 3). Milk production and lactation potential were similar
for SS and CON heifers (P > 0.28; Table 4). Calves from CON dams were heavier
at early, mid, and late lactation (P < 0.08; Table 4). Heifer development
strategy did not effect second or third parity performance (data not shown).
Table 2. Effect of conventional (CON) or stair-step
(SS) heifer development strategies on growth in beef
heifers (Trials 1 and 2).
-----------------------------------------------------
Treatment
---------------
Item CON SS SEM P
-----------------------------------------------------
Trial 1
BW, lb
d 90 937.0 932.6 22.9 0.89
d 180 1012.9 984.5 9.2 0.04
d 270 1254.0 1242.3 12.3 0.51
ADG, lb
d 90 to 180 0.86 0.55 0.09 0.04
d 181 to 270 2.66 2.86 0.09 0.17
d 90 to 270 1.76 1.72 0.07 0.51
Body Condition Score
d 90 5.67 5.65 0.19 0.94
d 180 5.63 5.05 0.15 0.01
d 270 6.08 6.04 0.16 0.86
Trial 2
BW, lb
d 90 1018.2 1044.1 22.2 0.42
d 180 1229.1 1111.0 30.1 0.001
d 270 1294.7 1300.4 35.0 0.91
ADG, lb
d 90 to 210 1.78 0.53 0.09 <0.001
d 211 to 270 0.88 3.12 0.09 <0.001
d 90 to 270 1.52 1.83 0.11 0.02
Body Condition Score
d 90 6.11 6.08 0.06 0.73
d 210 6.19 4.64 0.08 <0.001
d 270 6.19 6.13 0.12 0.68
-----------------------------------------------------
Table 3. Effect of conventional (CON) or stair-step
(SS) heifer development strategies on heifer and
calf performance at parturition (Trials 1 and 2).
-------------------------------------------------------
Treatment
---------------
Item CON SS SEM P
-------------------------------------------------------
Trial 1
Gestation Length, d 292.2 278.7 5.8 0.05
Calving Ease Score 1.00 1.09 0.06 0.33
Calf Vigor Score 1.00 1.45 0.22 0.16
Calf Birth Weight, lb 72.8 71.3 3.7 0.79
Trial 2
Gestation Length, d 283.4 283.8 2.2 0.92
Calving Ease Score 1.33 1.44 0.16 0.63
Calf Vigor Score 1.00 1.17 0.11 0.32
Calf Birth Weight, lb 80.7 80.7 1.09 0.96
-------------------------------------------------------
Trial 2. As expected, energy restriction decreased ADG, body weight,
and BCS in SS heifers compared to CON (P < 0.001). During the compensation
period, SS heifers had increased ADG (P < 0.001; Table 2). At the end of
the compensation period, heifer body weights were similar (P = 0.91). Due to
the design of the study, these differences were expected. No differences in
gestation length, birth weight, calving difficulty, or calf vigor were noted
for SS and CON heifers (P > 0.32; Table 3). No differences in milk production
were noted for SS and CON heifers (P = 0.84; Table 4). In other species, lactation
potential has been increased by following stair step development programs. However,
calves from CON dams tended (P = 0.12; Table 4) to be heavier at weaning. The
reasons for this weight difference are not apparent, since similar milk productions
were noted and the cattle grazed common pastures during the summer.
Table 4. Effect of conventional (CON) or stair-step (SS)
heifer development strategies on heifer milk production
and calf weight gain (Trials 1 and 2).
----------------------------------------------------------
Treatment
------------- Treatment
Item CON SS SEM P-Value
----------------------------------------------------------
Trial 1
Milk Production, lb/d
d 42 21.6 18.5 1.8 0.28
d 133 12.5 11.9 0.9 0.63
d 197 11.7 11.0 0.9 0.68
Calf Body Weight, lb
d 42 184.4 159.1 9.2 0.09
d 133 310.0 277.0 11.7 0.08
d 197 478.1 431.9 13.6 0.05
Nursing Gain, lb/d 2.05 1.83 0.07 0.02
Trial 2
Milk Production, lb/d
d 72 13.9 12.8 2.0 0.40
d 147 10.3 9.5 0.9 0.53
d 218 8.8 9.5 1.1 0.72
Calf Body Weight, lb
d 80 216.0 208.8 8.8 0.56
d 145 315.3 304.9 13.4 0.54
d 216 399.1 363.0 14.7 0.12
Nursing Gain, lb/d 1.47 1.32 0.44 0.17
----------------------------------------------------------
Conclusion
Our results indicate gestating beef heifers can be energy restricted and re-fed
during mid and late gestation, respectively, without adverse effects on either
maternal or calf performance, provided the heifer reaches BCS 6 prior to calving.
However, the lactation potential in beef heifers seems to be unresponsive to
compensatory growth strategies applied during gestation, which is different
from many other animal models (dairy heifers, gilts, rats) in which lactation
yield is increased following a stair step development program. Unlike dairy
cows, beef cows may not be able to express their maximum lactation potential
because they lack the biological necessity to do so. The beef cow produces milk
when needed (stimulated by suckling). Dairy cows require a relatively high nutritional
level during lactation. This high level of nutrition satisfies the metabolic
demand for milk synthesis associated with induced compensatory mammary tissues.
Literature Cited
Ford, J.A. and C.S. Park. 2001. Nutritionally directed compensatory growth
enhances heifer development and lactational potential. J. Dairy Sci. 84:1669-1678.
Freetly, H.C., C.L. Ferrell, and T.G. Jenkins. 2001. Production performance
of beef cows raised on three different nutritionally controlled heifer development
programs. J. Anim. Sci. 79:819-826.
Park, C.S., R.B. Danielson, B.S. Kreft, S.H. Kim, Y.S. Moon, and W.L. Keller.
1998. Nutritionally directed compensatory growth and effects on lactation
potential of developing heifers. J. Dairy Sci. 81:243-249.
1Department
of Animal and Range Sciences
North Dakota State University
INDEX
Comparison of corn versus soyhulls as a source of energy
in lactating beef cow diets
T.A. Baumann1, G.P.
Lardy1, W.W. Dvorak1, and V.L.
Anderson2
The use of soyhulls instead of corn as a supplement source for lactating
beef cows did not affect milk production, cow body condition score or calf
weaning weights. The addition of sunflower meal as a protein source also had
no effect. Soyhulls may be used for supplementation of lactating beef cows
when cost-effective.
A 2 x 2 factorial design was used to determine effects of supplement type (corn
vs soyhulls) and protein addition (with or without) to a medium-quality forage
diet for lactating beef cows. Cow/calf pairs (n = 78; 1346 ± 7.5 and 200
± 3.3 lb initial BW; cows and calves, respectively) were used in the study.
A basal diet consisting of 75% grass hay (11.5% CP, 65.9% NDF and 40.1% ADF)
and 25% wheat straw (7.4% CP, 75.9% NDF and 50.2% ADF; DM basis) was fed from
May 16 (43 ± 10 days post-partum) to Sept. 6. Cows were stratified by calving
date and BW and assigned randomly to treatment. Supplemental treatments and
predicted DIP balances were 10.5 lb dry rolled corn (-415 g/d); 11.7 lb soyhulls
(SH; -260 g/d); 8.11 lb dry rolled corn plus 3.42 lb sunflower meal (-0.02 g/d);
or 9.9 lb SH plus 2.31 lb. sunflower meal (-0.02 g/d). Diets were formulated
to provide 20 Mcal/d NEm. Cow BW, body condition score (BCS), milk
yield and calf BW were recorded at days 1, 28, 56, 84 and 112 except milk yield
which was not recorded at day one. Data was analyzed as a split-plot in time
with one pen as the experimental unit and two pens per treatment. No interaction
between energy source and addition of protein was present (P = 0.33)
nor was there an interaction between treatment and sampling period (P
= 0.91) for any response variable. Therefore, the main effects of treatment
and period are discussed. Energy source and addition of protein had no effect
(P > 0.16) on cow BW, BCS, milk yield, or calf BW. Cow BW decreased
(P < 0.001) from 1346 to 1288 ± 7.5 lb during the study. Cow
BCS decreased (P < 0.001) from 5.58 on day one to 5.01 ± 0.05
on day 112. Milk yield declined (P < 0.001) from 28.9 lb on day 28
to 17.0 ± 2.4 lb on day 112. Calf BW increased (P < 0.001) from
200 to 483 ± 3.3 lb during the 112-day trial. In summary, no differences
due to energy source or protein addition were noted for BW, BCS or milk yield,
and calf BW. Therefore, corn or SH are suitable as an energy source when supplementing
the quality of forage used in this trial. Addition of supplemental protein did
not improve cow or calf performance.
Introduction
Supplementing lactating cows is necessary when forage production
is not adequate in either quantity or quality to meet the nutrient
requirements of lactation. Low-quality forages such as winter native
pastures, crop residues, and CRP hay often do not provide enough crude protein
or energy to adequately maintain cow body weight and body condition
score during early lactation. Research by Fleck et al. (1987) and Ovenell
(1991) has shown that feeding the proper amounts and type of
supplements (those low in starch) improves utilization of low-quality
forages. Feeding grains with low-quality forages may have a negative effect
on the digestion of the forage. Soyhulls, a soybean by-product high in
digestible fiber, should increase energy intake without the adverse effects
normally observed when high-starch feedstuffs are used to supplement
low-quality forages (Marston et al., 1993). Determining proper
supplement practices is necessary to maintain optimum cattle performance. The
cost of supplementing lactating cows may be reduced by feeding
by-products such as soyhulls instead of a cereal grain like corn. However, for
energy supplementation to be effective, ruminal degradable intake
protein requirements must be met. Therefore, this study evaluated the use of
soyhulls versus corn with or without supplemental degradable intake protein
in the diets of lactating beef cows.
Procedures
The study utilized 78 cow-calf pairs in a completely randomized design (initial
BW 1346 ± 7.5 and 200 ± 3.3 lb for cows and calves, respectively).
A basal diet consisting of 75% grass hay (11.5% CP, 65.9% NDF, 40.1% ADF; DM
basis) and 25% wheat straw (7.4% CP, 75.9% NDF, 50.2% ADF) was fed from May
16 (43 ± 10 days post-partum) to Sept. 6. Pairs were confined in drylot
located at the Carrington Research Extension Center with 9 to 10 pairs per pen.
Animals were stratified by calving date and BW and assigned randomly to treatment.
Supplemental treatments were 10.5 lb dry rolled corn (C), 11.7 lb soyhulls (SH),
8.1 lb dry rolled corn plus 3.40 lb sunflower meal (C+P), and 9.9 lb SH plus
2.33 lb sunflower meal (SH+P). Diets were reformulated to meet lower energy
requirement of late lactation on July 25 (Table 2). Animals were weighed and
cow body condition score (BCS) reported every four weeks during the trial. Prior
to the start of the trial, five cows from each treatment were chosen randomly
for milk sample analysis. Each teat was stripped prior to obtaining a milk sample.
Milk yield from cows was determined by the weigh-suckle-weigh method. Calves
were allowed to suckle their dams after a three-hour separation period. Calves
were then separated from their dams for eight hours. Calves were weighed, allowed
to suckle to completion, and weighed to determine milk production.
Table 1. Early lactation diet composition (percent, DM basis).
-------------------------------------------------------------------
Treatmenta
------------------------------------------
Corn Corn/protein SH SH/protein
-------------------------------------------------------------------
Hay 49 48 47 47
Wheat Straw 16 16 16 16
Corn 34 26 0 0
SH 0 0 37 31
SF meal 0 11 0 7
-------------------------------------------------------------------
DMI, lb 30.5 31.5 31.7 32.2
Formulated, Diet CP, % 8.0 11.1 8.9 10.8
-------------------------------------------------------------------
aSH = Soyhulls, SF = Sunflower meal.
Table 2. Late lactation diet composition (percent, DM basis).
------------------------------------------------------------------
Treatmenta
-----------------------------------------
Corn Corn/protein SH SH/protein
------------------------------------------------------------------
Hay 59 57 58 57
Wheat Straw 19 19 19 18
Corn 22 15 0 0
SH 0 0 24 18
SF meal 0 9 0 7
------------------------------------------------------------------
DMI, lb 27.0 27.9 27.7 28.2
Formulated, Diet CP, % 7.7 10.3 8.2 10.2
------------------------------------------------------------------
aSH = Soyhulls, SF = Sunflower meal.
Results
Energy source and addition of protein had no effect (P > 0.16) on
cow BW, BCS or milk yield, and calf BW. During the study, cow BW decreased (P
< 0.001) from 1346 to 1288 ± 7.5 lb; BCS decreased (P <
0.001) from 5.58 on day 1 to 5.01 ± 0.05 on day 112, and daily calf milk
intake declined (P < 0.001) from 28.9 lb on day 28 to 17.0 ±
2.4 lb on day 112. Calf BW increased (P < 0.001) from 200 to 483 ±
3.3 lb during the 112-day trial (Table 3). Contrasts for supplement type and
protein addition were not significant for cow BW (P = 0.16 and 0.62,
for supplement type and protein addition respectively), BCS (P = 0.29
and 0.20), milk yield (P = 0.87 and 0.48) and calf BW (P = 0.23
and 0.41; Table 4).
Table 3. Effect of day on BW, BCS, milk yield and calf BW in cows fed
medium-quality forage diets.
---------------------------------------------------------------------------
Day
-------------------------------------------
Item 1 28 56 84 112 SE P-value
---------------------------------------------------------------------------
Cow BW, lb 1346 1347 1329 1293 1288 7.5 < 0.001
BCS 5.58 5.73 5.54 5.40 5.01 0.05 < 0.001
Milk, lb --- 28.9 23.8 19.4 17.0 2.4 < 0.001
Calf BW, lb 200 266 329 412 483 3.3 < 0.001
---------------------------------------------------------------------------
Table 4. Effect of supplement source and protein addition on BW,
BCS, milk yield and calf BW in cows fed medium-quality forage diets.
-------------------------------------------------------------------
Supplement Protein Contrasta
--------------- -------------- ----------
Item Corn Soyhulls (+) (-) SE 1 2
-------------------------------------------------------------------
Cow BW, lb
Initial 1342 1350 1343 1349 6.0 0.37 0.54
Final 1279 1296 1278 1297 18.9 0.54 0.50
BCS
Initial 5.53 5.63 5.53 5.63 0.07 0.35 0.35
Final 4.95 5.08 5.00 5.03 0.14 0.54 0.90
Milk, lb 22.5 21.8 20.7 23.8 2.9 0.87 0.48
Calf BW, lb
Initial 205 196 201 199 14.2 0.67 0.89
Final 471 495 492 475 9.2 0.12 0.25
-------------------------------------------------------------------
aContrasts for treatment effects within initial or final period.
1 = Corn vs soyhulls; 2 = with protein vs without protein.
Discussion
In the current study, cow BW and BCS decreased over time for
all treatments, but no differences occurred among treatments.
Decrease in BW and BCS may be expected as requirements for peak lactation
may not be met with diet sources. All treatments were formulated to
be isocaloric. High-energy supplements frequently contain cereal grains
that are high in starch (Hibberd et al., 1982). Cereal grain
supplements decrease forage digestibility and intake, resulting in no
improvements in the nutritional status of cows (Chase and Hibberd, 1987,
Martin and Hibberd, 1990). Since no difference in BW and BCS was
noted, both supplements had similar effects on forage digestion.
The addition of protein did not increase performance over the
non-supplemented treatments. This indicates that the diet (forage
plus corn or SH) supplied adequate protein to meet the lactation
requirements of these animals, therefore, milk yields were not affected.
Conclusion
In conclusion, no differences due to supplement type or protein
addition were noted for BW, BCS or milk yield, and calf BW. Therefore, corn
or SH are suitable as an energy supplement for the quality of forage
utilized in this trial. Addition of supplemental protein did not improve cow or
calf performance in this trial.
Literature Cited
Chase, C.C., Jr. and C.A. Hibberd. 1987. Utilization of low-quality native
grass hay by beef cow fed increasing quantities of corn grain. J. Anim. Sci.
65:557.
Fleck, A. T.,, K. S. Lusby, F. N. Owens and F. T. McCollum. 1987. Effects
of corn gluten feed on forage intake, digestibility and ruminal parameters
of cattle fed native grass hay. J. Anim. Sci. 66:750
Hibberd, C. A., D. G. Wagner, R. L. Schemm, E. D. Mitchell, Jr., R. L. Hintz
and D. E. Weibel. 1982. Nutritive characteristics of different varieties of
sorghum and corn grains. J. Anim. Sci. 55:665.
Marston, T. T., K. S. Lusby, and R. P. Wettemann. 1993. The effects of energy
and protein supplements on spring-calving cows. Okla. Ag. Exp. Station.
Martin, S. K. and C. A. Hibberd. 1990. Intake and digestibility of low-quality
native grass hay by beef cows supplemented with graded levels of soybean hulls.
J. Anim. Sci. 68:4319-4325.
Ovenell, K. H., K. S. Lusby, G. W. Horn, and R. W. McNew. 1991. Effects of
lactational status on forage intake, digestibility, and particulate passage
rate of beef cow supplemented with soybean meal, wheat middlings, and corn
and soybean meal. J. Anim. Sci. 69:2617-2623.
1Department
of Animal and Range Sciences
2Carrington Research
Center
North Dakota State University
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