One hundred Holstein heifers were used
to examine the effects of monensin
(Rumensin®) and lasalocid (Bovatec®)
included in calf starter and grower diets.
Heifers were assigned alternately at birth to a starter feed containing either Rumensin (28
g/ton, 90% dry matter basis) or Bovatec (40
g/ton, 90% dry matter basis). The Bovatec
group was switched to a starter feed containing
28 g Bovatec/ton (90% dry matter basis)
at 6 weeks of age. Both groups were
switched at 8 weeks of age to grower diets
designed to deliver 100 mg/head/day of either
Rumensin or Bovatec. No treatment differences
were observed between birth and 8
weeks of age. Heifers were moved from
individual hutches at 8 weeks of age to group
pens (five heifers/pen) and remained on the
same treatment for the next 84 days. During
this 84-day period, heifers receiving
Rumensin gained more weight at a faster rate
and tended to be more efficient than heifers
fed Bovatec. No differences were observed
in feed intake, skeletal growth as measured by
hip height, or body condition score

Isch, J. A.

Scheffel, Michael V.

Shirley, John E.

Thomas, E. C.

Titgemeyer, Evan C.

K-State Research Exchange

4Dairy Day 1999EFFECTS OF RUMENSIN AND BOVATEC ON GROWTH,FEED INTAKE, AND FEED EFFICIENCY INDAIRY CALVESJ. A. Isch, J. E. Shirley, M. V. Scheffel,E. C. Titgemeyer, and E.C. Thomas.SummaryOne hundred Holstein heifers were usedto examine the effects of monensin(Rumensin®) and lasalocid (Bovatec®)included in calf starter and grower diets.Heifers were assigned alternately at birth to astarter f ed containing either Rumensin (28g/ton, 90% dry matter basis) or Bovatec (40g/ton, 90% dry matter basis).  The Bovatecgroup was switched to a starter feed contain-ing 28 g Bovatec/ton (90% dry matter basis)at 6 weeks of age.  Both groups wereswitched at 8 weeks of age to grower dietsdesigned to deliver 100 mg/head/day of eitherRumensin or Bovatec.  No treatment differ-ences were observed between birth and 8weeks of age.  Heifers were moved fromindividual h tches at 8 weeks of age to grouppens (five heifers/pen) and remained on thesame treatment for the next 84 days.  Duringthis 84-day period, heifers receivingRumensin gained more weight at a faster rateand tended to be more efficient than heifersfed Bovatec.  No differencesw re observedin feed intake, skeletal growth as measured byhip height, or body condition score.  (Key Words: Calves, Replacement Heifers,Rumensin, Bovatec.)IntroductionDairy heifers often experience a reductionin rate of gain for the first week or two aftermoving from individual calf hutches to grouppens.  Various techniques have been tried toovercome this loss, including blending starterand grower feeds and delaying movementuntil heifers are consuming 5 lb of feed perday.  Stress-induced reduction in feed con-sumption or  decreased efficiency in f edutilization may be factors explaining thisdecrease in growth rate.  Inclusion of iono-phores in the tarter feed offers a potentialmeans of alleviating this reduction in gain.Both Rumensin® (monensin) andBovatec®(lasalocid) have claims for in-c eased rate of weight gain in dairy replace-ment heifers.  Additional claims of theseionop ores include control and prevention ofcoccidiosis, and improved feed efficiency incalve  and mproved feed efficiency in cattlefed in confin m nt for slaughter. Litt e info -mati n is available that compares concur-rently the efficacy of each ionop ore in heif-rs from b rth to 20 weeks of age.  Thisperiod includes the transition from individualhutches to group pens.  The objective of thisstudy was to determine the efficacy for pr -venting nd controlling coccidiosis and ef-fects on feed intake, weight gain, hip h ,and feed efficiency, when these ionophoreswereinclud d in the diet beginning at 1 to 3days of age.Proced resOne hundred female Holstein calves fromthe Kansas State University dairy herd wereutilized in this study, which consisted ofPhase I (birth to 8 weeks of age) and Phase II(8 to 20 weeks of age).  Calves were assignedalternately  birth to treatment diets contain-ng eithe  R mensin or Bovatec.  Calves werepaired b sed on birth date, except for thefinal two pairings.  This occurred becausetwo calv s died (one on each treatment) andwere replaced to b ing the total number ofheifers to 100 (50/treatment).  Calves weremoved from the maternity area to individualhutcheswithin 48 hours after birth and of-ered a starter feed (pelleted) containing5either Rumensin (28 g/ton, 90% dry matterbasis) or Bovatec (40 g/ton, 90% dry matterbasis) along with whole milk (4% of bodyweight).  Whole milk was fed twice daily, andstarter feed was fed once daily. The amountsof starter feed fed and consumed were re-corded daily. Feed refusal was weighed be-fore ach new daily allocation.  One measuredtablespoon of wet molasses was distributedover the top of the daily starter feed alloca-tion to stimulate intake.  Calves were weanedwhen they consumed 2 lb of starter feed for 3consecutive days.  If this level of intake wasnot achieved by 36 ays of age, milk offeredwas reduced by 50% to stimulate starter feedintake.  The starter pellets (Table 1) weremanufactured at the Grain Science Feed Milllocated on theKansas State University cam-pus.  Each batch was sampled and shipped toElanco Animal Health (Greenfield, IN) forRumensin compliance analysis or Hoffman-LaRoche (Belvidere, NJ) for Bovatec compli-ance analysis before they were used in thestudy.  Forages were sampled weekly andcomposited monthly, and grain mixes weresampled by batch for analysis.  Silage wasanalyzed weekly for dry matter, and theamount fed adjusted accordingly.  The pri-mary source of protein in the Phase II dietswas alfalfa hay (21% CP) offered in a TMRwith corn silage and a grain mix containingground corn and a mineral and vitamin pre-mix.  The ionophores were mixed withground corn and offere as a topdressing.Table 1.  Calf Starter-Pellet CompositionIngredient% ofDry MatterCracked corn 54.5Rolled oats 20.1Molasses 3.9Soybean meal 19.8Mineral-vitamin premix1.6Body weight and hip height measure-ments were obtained within 24 hours afterbirth, at weaning, and when calves weremoved from the hutches to the group pens (8weeks ± 3 days of age).  This was done on aWedn s y fter group pen daily feed refusalwa determined.  Group pen feed offered wasrecalculat d to include the new addition (five)to the pen.  Twenty-two group pens wereutilized in Phase II.  Eight pens for eachtreatment contained five heifers, two penscontained four heifers and one pen containedtwo h ifers.  The average number of daysrequir d to ill the Bovatec pens was 25(range 14 to 35), and the average numberrequired to fill the Rumensin pens was 19(r nge 14 to 35). The first calves enteredPhase II on February 25, 1998 and the lastcalvesntered Phase II on October 25, 1998fo bo h treatment groups.  Once a heiferentered a pen, it remained in there until thelast calfentering the same pen completed 84days. The average days in group pens were98.1 nd 94.6 for Bovatec and Rumensingroups, respectively, and were not signifi-cantly different.  Treatment pens ere paired based on thedate they were filled.  Because alternatecalves were assigned to treatments at birth,the average age of calves in paired pens wassimilar.  Pens were arranged in two rows, andtreatment groups were assigned to alternatingpensto reduce location effe t.  The amountof TMR fed was based on the number ofcalves per pen and the average weight ofcalves within the pen plus 14 lb of bodyweight per calf (projected gain in 7 days).Individual calf weights were obtained everyTuesday, and the amount of TMR fed wasadjusted very Wednesday.  Paired penseceived the same amount of TMR per headbased on the average weight of heifers in theheaviest pen to ensure that sufficientfeed wasavailable to achieve the desired rate of gain.The ionophores were mixed with finelyground corn at the rate of 200 g/ton and fedas a topdressing to deliver 100 mg/head/day(1 lb of topdressing per head per day).Heifers were weighed within 24 hr ofbirth; at weaning; when moved from hutchesto group pens; and on days 28, 56, and 84following movem nt into group pens.  Hipheightwas me sured within 24 hr of birth,6when heifers were moved to group pens; andat the end of the trial.  Feces of individualcalves in hutches were scored daily using thescale of: 1 = normal, solid; 2 = with consis-tency of partially melted soft-serve ice cream;3 = moderate scours with consistency ofpancake batter, spread out without firm parts;4 = primarily liquid with consistency of water;and 5= bloody.  After calves were moved togroup pens, a fecal score was determinedweekly for the pen.  All heifers were observeddaily, and their health conditions were re-corded along with appropriate follow-upobservation and therapy. Results and DiscussionThe responses of dairy calves to Rumen-sin orBovatec inclusion in starter feed (birthto 8 weeks of age) are shown in Tabl 2.  Theaverage daily gain and dry matter intake werelower than expected based on previous expe-rience and probablywere due to the pelletedfeed used in the study.  The low intakes ofboth starter feeds reduced the average intakesof Rumensin and Bovatec to 26 and 37 mgper head per day, respectively, during the 8-week period.  No differencesw re observedin performance traits measured.  Further,none of the calves experienced coccidiosis,and fecal scores for both groups averaged lessthan 2.The responses of dairy heifers duringPhase II (8 to 20 weeks of ge) of the studyareshown in Table 3.  Average daily gainwas greater (P<.01) for heifers receivingRumensin than for those fed Bovatec.  Drymater intak  and lbs. of gain per lb of feedwere si il  between the two treatments.The d e s in Phase II were formulated toprovide sufficient protein to support 2 lb ofdaily gain.  The reason for this formulationwas to test th  ability of the ionophores toimpr ve nergy efficiency through theirefectson rumen fermentation.  Additionalprotein was included to ensure that it was notlimiting. Exposure to this type of grower dietwithout a transition period probablyaccounted for the slow rate of gain during thefirst 28 days after calves were moved fromhu ches to group pens.  Calves fed Rumensingain d faster (P<.05) than those fed Bovatecduring this period.  These results agree withhe concept that Rumensin improves rate ofgain when dded o high forage diets.  Theuse of ionophores in starter and grower dietsofera convenient method to controlcoccidiosis and potentially improve feedeficiency.  Further studies with a more palat-able starter feed are warranted.Table 3.Effect of Ionophores on Performance of Dairy Heifers from Birth to 8 Weeksof Age (Phase I)TreatmentItem BovatecRumensin SEM P-ValueBirth wt, lb 79.5 79.5 1.4 .98Weaning wt, lb 111 108 1.9 .28Weight at 8 weeks, lb132 131 2.27 .72Days to weaning 40.6 41.0 .58 .70Days to weaning weight43.6 43.2 .17 .07Days in hutches 56.4 56.9 .24 .10Daily gain, lb     Birth to weaning.72 .66 .03 .16     Birth to 8 weeks.92 .89 .03 .50Daily intake (DM), lb1.87 1.86 .04 .86Gain/feed .50 .48 .01 .37Hip height, inches     Birth 30.4 30.2 .20 .52     Weaning 32.9 33.1 .23 .58     8 weeks 34.1 34.2 .23 .817Table 3.Effects of Ionophores on Performance of Dairy Heifers from 8 to 20 Weeks ofAge (Phase II) TreatmentItem BovatecRumensin SEM P-ValueHip height, inches     56 days of age34.1 34.2 .32 .75     140 days of age38.2 38.4 .16 .37Body weight, lb     56 days of age130 133 3.07 .60     84 days of age166 174 3.48 .12     112 days of age 216 229 3.11 .01     140 days of age267 282 3.90 .02Daily gain     56-84 days of age1.28 1.49 .06 .03     56-112 days of age 1.53 1.73 .03 .001     56-140 days of age 1.62 1.78 .02 .0006Daily intake (DM), lb7.04 7.05 .08 .90Gain/feed .24 .26 .009 .22Average days in pen98 95 1.4 .1

Effects of rumensin and bovatec on growth, feed intake, and feed efficiency in dairy calves

J. A. Isch

Michael V. Scheffel

Evan C. Titgemeyer

E. C. Thomas

Crossref

Kansas Agricultural Experiment Station Research Reports

One hundred Holstein heifers were used to examine the effects of monensin (Rumensin®) and lasalocid (Bovatec®) included in calf starter and grower diets. Heifers were assigned alternately at birth to a starter feed containing either Rumensin (28 g/ton, 90% dry matter basis) or Bovatec (40 g/ton, 90% dry matter basis). The Bovatec group was switched to a starter feed containing 28 g Bovatec/ton (90% dry matter basis) at 6 weeks of age. Both groups were switched at 8 weeks of age to grower diets designed to deliver 100 mg/head/day of either Rumensin or Bovatec. No treatment differences were observed between birth and 8 weeks of age. Heifers were moved from individual hutches at 8 weeks of age to group pens (five heifers/pen) and remained on the same treatment for the next 84 days. During this 84-day period, heifers receiving Rumensin gained more weight at a faster rate and tended to be more efficient than heifers fed Bovatec. No differences were observed in feed intake, skeletal growth as measured by hip height, or body condition score.; Dairy Day, 1999, Kansas State University, Manhattan, KS, 1999

Kansas State University

Kansas Agricultural Experiment Station Research Reports Volume 0 Issue 2 Dairy Research (1984-2014) Article 6 1999 Effects of rumensin and bovatec on growth, feed intake, and feed efficiency in dairy calves J. A. Isch Michael V. Scheffel Evan C. Titgemeyer See next page for additional authors This report is brought to you for free and open access by New Prairie Press. It has been accepted for inclusion in Kansas Agricultural Experiment Station Research Reports by an authorized administrator of New Prairie Press. Copyright 1999 Kansas State University Agricultural Experiment Station and Cooperative Extension Service. Contents of this publication may be freely reproduced for educational purposes. All other rights reserved. Brand names appearing in this publication are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. K-State Research and Extension is an equal opportunity provider and employer. Follow this and additional works at: https://newprairiepress.org/kaesrr  Part of the Dairy Science Commons Recommended Citation Isch, J. A.; Scheffel, Michael V.; Titgemeyer, Evan C.; and Thomas, E. C. (1999) "Effects of rumensin and bovatec on growth, feed intake, and feed efficiency in dairy calves," Kansas Agricultural Experiment Station Research Reports: Vol. 0: Iss. 2. https://doi.org/10.4148/2378-5977.2931 Effects of rumensin and bovatec on growth, feed intake, and feed efficiency in dairy calves Abstract One hundred Holstein heifers were used to examine the effects of monensin (Rumensin®) and lasalocid (Bovatec®) included in calf starter and grower diets. Heifers were assigned alternately at birth to a starter feed containing either Rumensin (28 g/ton, 90% dry matter basis) or Bovatec (40 g/ton, 90% dry matter basis). The Bovatec group was switched to a starter feed containing 28 g Bovatec/ton (90% dry matter basis) at 6 weeks of age. Both groups were switched at 8 weeks of age to grower diets designed to deliver 100 mg/head/day of either Rumensin or Bovatec. No treatment differences were observed between birth and 8 weeks of age. Heifers were moved from individual hutches at 8 weeks of age to group pens (five heifers/pen) and remained on the same treatment for the next 84 days. During this 84-day period, heifers receiving Rumensin gained more weight at a faster rate and tended to be more efficient than heifers fed Bovatec. No differences were observed in feed intake, skeletal growth as measured by hip height, or body condition score.; Dairy Day, 1999, Kansas State University, Manhattan, KS, 1999; Keywords Dairy Day, 1999; Kansas Agricultural Experiment Station contribution; no. 00-136-S; Report of progress (Kansas Agricultural Experiment Station and Cooperative Extension Service); 842; Dairy; Calves; Replacement heifers; Rumensin; Bovatec Creative Commons License This work is licensed under a Creative Commons Attribution 4.0 License. Authors J. A. Isch, Michael V. Scheffel, Evan C. Titgemeyer, and E. C. Thomas This research report is available in Kansas Agricultural Experiment Station Research Reports: https://newprairiepress.org/kaesrr/vol0/iss2/6 4Dairy Day 1999EFFECTS OF RUMENSIN AND BOVATEC ON GROWTH,FEED INTAKE, AND FEED EFFICIENCY INDAIRY CALVESJ. A. Isch, J. E. Shirley, M. V. Scheffel,E. C. Titgemeyer, and E.C. Thomas.SummaryOne hundred Holstein heifers were usedto examine the effects of monensin(Rumensin®) and lasalocid (Bovatec®)included in calf starter and grower diets.Heifers were assigned alternately at birth to astarter feed containing either Rumensin (28g/ton, 90% dry matter basis) or Bovatec (40g/ton, 90% dry matter basis).  The Bovatecgroup was switched to a starter feed contain-ing 28 g Bovatec/ton (90% dry matter basis)at 6 weeks of age.  Both groups wereswitched at 8 weeks of age to grower dietsdesigned to deliver 100 mg/head/day of eitherRumensin or Bovatec.  No treatment differ-ences were observed between birth and 8weeks of age.  Heifers were moved fromindividual hutches at 8 weeks of age to grouppens (five heifers/pen) and remained on thesame treatment for the next 84 days.  Duringthis 84-day period, heifers receivingRumensin gained more weight at a faster rateand tended to be more efficient than heifersfed Bovatec.  No differences were observedin feed intake, skeletal growth as measured byhip height, or body condition score.  (Key Words: Calves, Replacement Heifers,Rumensin, Bovatec.)IntroductionDairy heifers often experience a reductionin rate of gain for the first week or two aftermoving from individual calf hutches to grouppens.  Various techniques have been tried toovercome this loss, including blending starterand grower feeds and delaying movementuntil heifers are consuming 5 lb of feed perday.  Stress-induced reduction in feed con-sumption or  decreased efficiency in feedutilization may be factors explaining thisdecrease in growth rate.  Inclusion of iono-phores in the starter feed offers a potentialmeans of alleviating this reduction in gain.Both Rumensin® (monensin) andBovatec® (lasalocid) have claims for in-creased rate of weight gain in dairy replace-ment heifers.  Additional claims of theseionophores include control and prevention ofcoccidiosis, and improved feed efficiency incalves and improved feed efficiency in cattlefed in confinement for slaughter.  Little infor-mation is available that compares concur-rently the efficacy of each ionophore in heif-ers from birth to 20 weeks of age.  Thisperiod includes the transition from individualhutches to group pens.  The objective of thisstudy was to determine the efficacy for pre-venting and controlling coccidiosis and ef-fects on feed intake, weight gain, hip height,and feed efficiency, when these ionophoreswere included in the diet beginning at 1 to 3days of age.ProceduresOne hundred female Holstein calves fromthe Kansas State University dairy herd wereutilized in this study, which consisted ofPhase I (birth to 8 weeks of age) and Phase II(8 to 20 weeks of age).  Calves were assignedalternately at birth to treatment diets contain-ing either Rumensin or Bovatec.  Calves werepaired based on birth date, except for thefinal two pairings.  This occurred becausetwo calves died (one on each treatment) andwere replaced to bring the total number ofheifers to 100 (50/treatment).  Calves weremoved from the maternity area to individualhutches within 48 hours after birth and of-fered a starter feed (pelleted) containing5either Rumensin (28 g/ton, 90% dry matterbasis) or Bovatec (40 g/ton, 90% dry matterbasis) along with whole milk (4% of bodyweight).  Whole milk was fed twice daily, andstarter feed was fed once daily. The amountsof starter feed fed and consumed were re-corded daily. Feed refusal was weighed be-fore each new daily allocation.  One measuredtablespoon of wet molasses was distributedover the top of the daily starter feed alloca-tion to stimulate intake.  Calves were weanedwhen they consumed 2 lb of starter feed for 3consecutive days.  If this level of intake wasnot achieved by 36 days of age, milk offeredwas reduced by 50% to stimulate starter feedintake.  The starter pellets (Table 1) weremanufactured at the Grain Science Feed Milllocated on the Kansas State University cam-pus.  Each batch was sampled and shipped toElanco Animal Health (Greenfield, IN) forRumensin compliance analysis or Hoffman-LaRoche (Belvidere, NJ) for Bovatec compli-ance analysis before they were used in thestudy.  Forages were sampled weekly andcomposited monthly, and grain mixes weresampled by batch for analysis.  Silage wasanalyzed weekly for dry matter, and theamount fed adjusted accordingly.  The pri-mary source of protein in the Phase II dietswas alfalfa hay (21% CP) offered in a TMRwith corn silage and a grain mix containingground corn and a mineral and vitamin pre-mix.  The ionophores were mixed withground corn and offered as a topdressing.Table 1.  Calf Starter-Pellet CompositionIngredient% ofDry MatterCracked corn 54.5Rolled oats 20.1Molasses 3.9Soybean meal 19.8Mineral-vitamin premix 1.6Body weight and hip height measure-ments were obtained within 24 hours afterbirth, at weaning, and when calves weremoved from the hutches to the group pens (8weeks ± 3 days of age).  This was done on aWednesday after group pen daily feed refusalwas determined.  Group pen feed offered wasrecalculated to include the new addition (five)to the pen.  Twenty-two group pens wereutilized in Phase II.  Eight pens for eachtreatment contained five heifers, two penscontained four heifers and one pen containedtwo heifers.  The average number of daysrequired to fill the Bovatec pens was 25(range 14 to 35), and the average numberrequired to fill the Rumensin pens was 19(range 14 to 35). The first calves enteredPhase II on February 25, 1998 and the lastcalves entered Phase II on October 25, 1998for both treatment groups.  Once a heiferentered a pen, it remained in there until thelast calf entering the same pen completed 84days.  The average days in group pens were98.1 and 94.6 for Bovatec and Rumensingroups, respectively, and were not signifi-cantly different.  Treatment pens were paired based on thedate they were filled.  Because alternatecalves were assigned to treatments at birth,the average age of calves in paired pens wassimilar.  Pens were arranged in two rows, andtreatment groups were assigned to alternatingpens to reduce location effect.  The amountof TMR fed was based on the number ofcalves per pen and the average weight ofcalves within the pen plus 14 lb of bodyweight per calf (projected gain in 7 days).Individual calf weights were obtained everyTuesday, and the amount of TMR fed wasadjusted every Wednesday.  Paired pensreceived the same amount of TMR per headbased on the average weight of heifers in theheaviest pen to ensure that sufficient feed wasavailable to achieve the desired rate of gain.The ionophores were mixed with finelyground corn at the rate of 200 g/ton and fedas a topdressing to deliver 100 mg/head/day(1 lb of topdressing per head per day).Heifers were weighed within 24 hr ofbirth; at weaning; when moved from hutchesto group pens; and on days 28, 56, and 84following movement into group pens.  Hipheight was measured within 24 hr of birth,6when heifers were moved to group pens; andat the end of the trial.  Feces of individualcalves in hutches were scored daily using thescale of: 1 = normal, solid; 2 = with consis-tency of partially melted soft-serve ice cream;3 = moderate scours with consistency ofpancake batter, spread out without firm parts;4 = primarily liquid with consistency of water;and 5 = bloody.  After calves were moved togroup pens, a fecal score was determinedweekly for the pen.  All heifers were observeddaily, and their health conditions were re-corded along with appropriate follow-upobservation and therapy. Results and DiscussionThe responses of dairy calves to Rumen-sin or Bovatec inclusion in starter feed (birthto 8 weeks of age) are shown in Table 2.  Theaverage daily gain and dry matter intake werelower than expected based on previous expe-rience and probably were due to the pelletedfeed used in the study.  The low intakes ofboth starter feeds reduced the average intakesof Rumensin and Bovatec to 26 and 37 mgper head per day, respectively, during the 8-week period.  No differences were observedin performance traits measured.  Further,none of the calves experienced coccidiosis,and fecal scores for both groups averaged lessthan 2.The responses of dairy heifers duringPhase II (8 to 20 weeks of age) of the studyare shown in Table 3.  Average daily gainwas greater (P<.01) for heifers receivingRumensin than for those fed Bovatec.  Drymater intake and lbs. of gain per lb of feedwere similar between the two treatments.The diets in Phase II were formulated toprovide sufficient protein to support 2 lb ofdaily gain.  The reason for this formulationwas to test the ability of the ionophores toimprove energy efficiency through theireffects on rumen fermentation.  Additionalprotein was included to ensure that it was notlimiting. Exposure to this type of grower dietwithout a transition period probablyaccounted for the slow rate of gain during thefirst 28 days after calves were moved fromhutches to group pens.  Calves fed Rumensingained faster (P<.05) than those fed Bovatecduring this period.  These results agree withthe concept that Rumensin improves rate ofgain when added to high forage diets.  Theuse of ionophores in starter and grower dietsoffer a convenient method to controlcoccidiosis and potentially improve feedefficiency.  Further studies with a more palat-able starter feed are warranted.Table 3. Effect of Ionophores on Performance of Dairy Heifers from Birth to 8 Weeksof Age (Phase I)TreatmentItem Bovatec Rumensin SEM P-ValueBirth wt, lb 79.5 79.5 1.4 .98Weaning wt, lb 111 108 1.9 .28Weight at 8 weeks, lb 132 131 2.27 .72Days to weaning 40.6 41.0 .58 .70Days to weaning weight 43.6 43.2 .17 .07Days in hutches 56.4 56.9 .24 .10Daily gain, lb     Birth to weaning .72 .66 .03 .16     Birth to 8 weeks .92 .89 .03 .50Daily intake (DM), lb 1.87 1.86 .04 .86Gain/feed .50 .48 .01 .37Hip height, inches     Birth 30.4 30.2 .20 .52     Weaning 32.9 33.1 .23 .58     8 weeks 34.1 34.2 .23 .817Table 3. Effects of Ionophores on Performance of Dairy Heifers from 8 to 20 Weeks ofAge (Phase II) TreatmentItem Bovatec Rumensin SEM P-ValueHip height, inches     56 days of age 34.1 34.2 .32 .75     140 days of age 38.2 38.4 .16 .37Body weight, lb     56 days of age 130 133 3.07 .60     84 days of age 166 174 3.48 .12     112 days of age 216 229 3.11 .01     140 days of age 267 282 3.90 .02Daily gain     56-84 days of age 1.28 1.49 .06 .03     56-112 days of age 1.53 1.73 .03 .001     56-140 days of age 1.62 1.78 .02 .0006Daily intake (DM), lb 7.04 7.05 .08 .90Gain/feed .24 .26 .009 .22Average days in pen 98 95 1.4 .11

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Effects of rumensin and bovatec on growth, feed intake, and feed efficiency in dairy calves

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