Florence, M. J.

Hutcheson, D. P.

Rouquette, F. M., Jr.

English

OAKTrust Digital Repository (Texas A&M Univ)

    PUBLICATIONS 1990 INFLUENCE OF LEVEL OF DAILY SUPPLEMENT INTAKE ON PERFORMANCEOF CALVES GRAZING RYE-RYEGRASS PASTURESF. M. Rouquette, Jr., M. J. Florence, D. P. Hutcheson, and W. C. EllisSUMMARYFall-weaned calves were grazed on rye-ryegrass pastures to determine theinfluence of two levels of a com-based supplemental feed on intake of ration anddaily gain. The targeted levels of 2 lbs VB 4 lbs per head per day were successfullyachieved using these two formulations. The 107-day average consumption was 2.32and 4.05 lbslday, respectively, for the two treatment groups. Calves receiving the2 lb and 4 lb/hd/day rations gained 2.34 and 2.26, respectively, which wassignificantly (P<.07) more than those calves which grazed pasture without an energysupplement. The additional 2 lblhd/day (4lb total), therefore, had no positive effecton daily gain over that of the 2 lblday total. Steers gained .33 lbslday more thanheifers (2.37 VB 2.04).INTRODUCTIONResearch conducted previously at the Overton Center has documented thebiological and economic benefits of supplementing a com-based ration to stockercattle grazing small grain-ryegrass pastures. The com-based rations used wererelatively effective in self-limiting calves to approximately 2 lbslhd/day. Theobjectives of this study were to determine if a simple dilution of the base rationwould be effective in limiting calves to 4 lbs daily; and to compare animalperformance from rations that were consumed at 1X VB 2X rates.PROCEDURESA total of 24 calves (112 Simmental x 1/4 Brahman x 1/4 Hereford), with anequal representation of steers and heifers, were allotted into 6 groups of 4 headeach. These groups were then randomly assigned to replicates of the followingthree treatments: (1) winter pasture with free-choice mineral; (2) winter pastureplus a self-limiting com-based supplement (lX); and (3) winter pasture plus a self-limiting com-based supplement that would allow for a 2X consumption of ration.The targeted daily intake per animal was 2 lbslday (1X) and 4 lbslday (2X). Acom-based ration was selected which had been used in several previous trials inwhich cattle grazing winter annual grasses had group intake estimates of 2lbslhd/day. This ration, in the past, had contained 3-4% salt with other minerals190and Rumensin to limit intake. Thus, the previously used ration with 4% salt wasselected to provide 2 Ibslday intake, and a ration which used one-half of the non-energy constituents were fed free-choice (Table 1). The rations were group fed incovered self-feeders with orts being measured at approximate 7-day intervalsthroughout the 107-day collection period (Feb. 21 to June 8). The totalweekly consumption of each 4-head group was then used to calculate a daily intakeper head.'Elbon' rye and 'Marshall' ryegrass were sod-seeded· into bermudagrasspastures in early October, 1988. The unseasonably dry fall prevented full-timegrazing until mid-December. Calves were adjusted to pasture and rations beforeinitiating the trial on January 4, 1989. The sudden, severe freeze in earlyFebruary necessitated that animals be removed from all test pastures fromFebruary 6 to February 21, 1989. Thus, the daily intake data are shown only forthe period of continuous grazing from February 21 to June 8, 1989. Pastures werestocked at approximately 1.8 calves per acre and adequate forage was available inall replicate groups to allow for ad libitum, selective intake of forage. Calves wereweighed at approximate 28-day intervals throughout the duration of the trial.RESULTS AND DISCUSSIONThe primary objectives of this trial were to feed two levels (IX and 2X) ofa corn-based, self-limiting supplement and evaluate: (a) the variability in intake ofeach group, and (b) the influence of supplemental feed on average daily gain (ADG).The weekly variation in ration intake among both replicate groups of eachsupplement level is shown in Table 2. With only minor exception, the 7-day periodestimates of daily intake were similar within a ration level group throughout thetrial. There were no clear indications that period had an effect on daily intake.Data are presented in Table 3 which shows the mean intake of both rations overtime. The potential impact of climate and forage quality have not been assessed,but these two factors, along with body size, may be causal factors for differencesin daily intake. Even though the daily intake of calves often exceeded the targetedrate by as much as two-fold, the 107-day group average showed that these tworations successfully limited intake to 2.32 and 4.05 Ibslhd/day, respectively. Othertrials (unpublished data) concerned with limiting the intake of feed on pasturewould indicate that the relatively low level of salt used in this trial was successfulin limiting intake because of the combination of other minerals and Rumensin.Previous research has shown that in the event that the minerals and Rumensin are191omitted, significantly higher levels of salt than those used in this trial arenecessary to limit intake to 2 lbslhdlday.The average daily gain of the 65Q-Ib, spring-born-fall-weaned steers andheifers was 2.01 lbslday from the winter pasture (Table 4). The magnitude of gainadvantage for steers vs heifers (2.37 vs 2.04 lbs/day) was .331bs and was similarto the gain advantage obtained from those calves that received supplemental energyvs those calves which received only winter pasture. There was no advantage tofeeding calves 4 lbslhdlday (2X) over those calves which received 2 lbslhdlday whilegrazing winter pasture. Both groups gained about 2.3 lbslhdlday although therewas a slight numerical, but not statistical, advantage for those calves whichreceived 2 lbslhdlday. Calves that initiated the winter pasture plus supplementtreatments at 650 pounds in early January finished the grazing trial weighing 1010pounds on June 8. At P<.07, both of the supplement treatment groups had greaterADG than the group assigned to only winter pasture. The extra gain in this trialwas .3 lb from a 2-lb daily ration, or a feed:gain conversion of nearly 6:1. Inprevious trials, the conversion ratios have been about 2.5 to 3:1. Some of thisdiscrepancy may be attributed to the shorter length of the 1988-89 trial due to thesevere freeze in early February.Another noteworthy portion of this trial was that the additional 2 lbslhd/day(2X ration) was used in a substitutive role rather than an additive fashion. And,the economic incentives would favor using the 2 lb/hdlday ration over either pastureonly or pasture plus 4 lb/hdlday ration. With $140/ton ration for example, the .3lb/day extra gain would cost about $.4O/lb with the 2 lb/hdlday ration. An extrapound of gain using the 2X ration would cost double that amount, or about $.80/lb.Thus, only in unique pricing and margin situations would the 2X ration provide apositive economic return. In summary, the gain responses and feed conversionsobtained in this trial would suggest that only small daily quantities (.25%± of bodyweight) of an energy supplement may be cost effectively used on winter pasture.And, further, that if supplement cannot be limited by ration formulation,management decisions should be made to consider limit-supplementation by hand-feeding the desired daily levels of energy supplement on winter pasture. The endweight of the supplemented calves (>1000 lbs) may allow these cattle to have ashorter residence time in the feedlot as compared to non-supplemented cattle. Theoverall size of the cattle used in this trial (650 initial and >1000 lb final weight)certainly affects the stocking rate and eventual gain per acre. Thus, severalmanagement factors are necessary to consider prior to adopting this approach tostocker grazing.192TABLE 1. SELF-LIMITING SUPPLEMENTAL RATIONS FED TO CALVESGRAZING WINTER PASTUREInlUedient IX Ration ZKRation----------------% DM-----------------Ground comSaltLimestoneMagnesium OxideDicalcium PhosphateRumensin 60Trace Mineral Pre-Mix85.64.02.01.07.0.15.2592.82.01.00.53.5.075.125TABLE 2. ESTIMATES OF DAILY INTAKE PER CALF ON A WEEKLY ANDTRIAL-LONG BASIS FOR TWO SUPPLEMENT RATIONSNo. IX RATION 2X RATIONDate Days Rep 1 Rep 2 AVG, Rep 1 Rep 2 AVa-----ll>s1da)r------ -----ll>s1da)r------2-21 to 2-26 6 1.67 1.33 1.50 3.33 2.67 3.002-27 to 3-5 7 2.86 2.86 2.86 4.57 1.71 3.143-6 to 3-12 7 2.29 3.14 2.72 4.57 4.00 4.293-13 to 3-19 7 1.41 2.00 1.71 5.25 3.82 4.543-20 to 3-30 11 1.73 2.00 1.87 4.00 4.00 4.003-31 to 4-6 7 .98 2.29 1.64 2.29 2.13 2.214-7 to 4-12 6 2.67 2.67 2.67 5.33 2.67 4.004-13 to 4-18 6 2.46 3.43 2.95 5.33 2.67 4.004-19 to 4-25 7 3.43 3.43 3.43 6.86 4.57 5.724-26 to 5-3 8 2.50 1.50 2.00 5.59 6.06 5.835-4 to 5-10 7 2.11 2.29 2.20 3.54 4.07 3.815-11 to 5-17 7 2.25 2.57 2.41 1.04 5.14 3.095-18 to 5-24 7 2.29 2.29 2.29 4.57 6.86 5.725-25 to 6-1 8 2.00 2.00 2.00 4.00 2.00 3.006-2 to 6-8 6 3.00 3.00 3.00 3.50 5.33 4.42TOTALS/AVERAGES 107 2.22 2.42 2.32 4,25 3.87 4,06193TABLE 3. AVERAGE INTAKE OF BOTH RATION TREATMENTS BY PERIODPeriod611412521147831510139Date3-31 to 4-62-21 to 2-265-25 to 6-15-11 to 5-173-20 to 3-302-27 to 3-53-20 to 3-303-13 to 3-194-7 to 4-124-13 to 4-183-6 to 3-126-2 to 6-84-26 to 5-35-18 to 5-244-19 to 4-25Average DailyIntake1.92 d12.25 ed2.50 bed2.75 bed2.93 bed3.00 bed3.00 bed3.12 abed3.34 abed3.47 abe3.50 abe3.71 abe3.91 ab4.00 ab4.57 aIMeans followed by the same letter do not differ signifieantly at P<.05 (LSD).TABLE 4. PERFORMANCE OF CALVES GRAZING WINTER PASTURE ANDRECEIVING SUPPLEMENTAL FEEDInitial AverageItem Weight Daily Gain P<,05 P<.G7(lbs) (lbs/day)SUDDlement TreatmentsPasture Only 654 2.01 b bPasture +1X Ration 653 2.34 a aPasture +2X Ration 656 2.26 ab aSEX &JllSteers 669 2.37 aHeifers 639 2.04 b194

Influence of Level of Daily Supplement Intake on Performance of Calves Grazing Rye-Ryegrass Pastures

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Influence of Level of Daily Supplement Intake on Performance of Calves Grazing Rye-Ryegrass Pastures

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