Effects of acclimation to handling on performance, reproductive, and physiological responses of Brahman-crossbread heifers

MISSING IMAGE

Material Information

Title:
Effects of acclimation to handling on performance, reproductive, and physiological responses of Brahman-crossbread heifers
Series Title:
2009 Florida Beef Report
Physical Description:
Book
Creator:
Cooke, R. F.
Austin, B. R.
Yelich, J. V.
Arthington, J. D.
Publisher:
Institute of Food and Agricultural Sciences, University of Florida
Place of Publication:
Gainesville, Fla.
Publication Date:

Record Information

Source Institution:
University of Florida Institutional Repository
Holding Location:
University of Florida
Rights Management:
All rights reserved by the source institution and holding location.
System ID:
AA00000435:00001


This item is only available as the following downloads:


Full Text







Effects of Acclimation to Handling on Performance, Reproductive, and
Physiological Responses of Brahman-crossbred Heifers

R. F. Cooke1
B. R. Austin
J. V. Yelich
J. D. Arthington


Acclimation to human handling after weaning hastened the onset of puberty in Brahman-crossbred
heifers.


Summary
The objective of this experiment was to evaluate
the effects of acclimation to human handling on
growth, plasma concentrations of cortisol, and
puberty attainment of Brahman-crossbred
heifers. Over two consecutive yr, 37 Braford and
43 Brahman x Angus heifers were assigned
randomly to receive or not the acclimation
treatment within 30 d after weaning. The
acclimation process consisted of bringing
heifers to the cowpens three times weekly during
four consecutive wk, where heifers were exposed
to common handling practices and returned to
pastures within 2 h. Heifers were maintained in
bahiagrass (Paspalum notatum) pastures and
received a blend of soybean hulls and cottonseed
meal at a daily rate of 6.0 lbs of DM per heifer
during the experiment (d 0 to 130). Blood
samples were collected prior to and at the end of
the acclimation process for determination of
cortisol concentrations. Puberty status was
assessed monthly during the experiment.
Acclimated heifers had decreased (P<0.05)
average daily gain (ADG) compared to control
heifers (1.1 vs. 1.3 lbs/d, respectively).
Attainment of puberty, however, was hastened
(P<0.01) for acclimated heifers. Further,
acclimated heifers had reduced cortisol
concentrations compared to control heifers after
the acclimation period (3.8 vs. 5.1 /g/dL,
respectively). Results from this experiment
indicated that c ,i~ h,,gh acclimation decreased


body weight gain, it enhanced the attainment of
puberty in Brahman-crossbred heifers.

Introduction
Age at puberty is influenced by breed type, and
heifers containing Brahman breeding typically
reach puberty after 15 mo of age (Plasse et al.,
1968; Rodrigues et al., 2002). In addition to this
genetic effect, Brahman-crossbred heifers are
often described as temperamental, and this trait
is expected to further negatively influence their
reproductive function (Plasse et al., 1970). Cattle
with excitable temperament experience
stimulated secretion and circulating
concentrations of ACTH and cortisol (Curley et
al., 2008). These hormones directly impair the
mechanisms responsible for puberty
establishment of heifers, such as synthesis and
release of gonadotropins (Li and Wagner, 1983;
Dobson et al., 2000). However, acclimation of
beef females to handling has been reported to
alleviate these negative physiological effects of
temperament on reproduction (Echternkamp,
1984). Based on these previous observations, we
hypothesized that Brahman-crossbred heifers
exposed to handling acclimation procedures
after weaning would experience improved
temperament, alleviated adrenal steroidogenesis,
and enhanced reproductive performance. The
objectives of the present experiment were to
compare growth, temperament, plasma


2009 Florida BeefReport










measurements, puberty attainment and
pregnancy rates of Brahman x Angus and
Braford heifers exposed or not to acclimation
procedures.

Materials and Methods
Over two consecutive yr, 37 Braford (37.5%
Brahman + 62.5% Hereford) and 43 Brahman x
Angus (approximately 25% Brahman) heifers
were initially evaluated for puberty status via
trans-rectal ultrasonography (d 0 and 10) and for
temperament by measurements of chute score,
pen score, and exit velocity (d 10) within 30 d
after weaning. On d 10, heifers were stratified
by puberty status, temperament and body weight
(BW), and randomly assigned to control or
acclimation treatment. Heifers were maintained
in bahiagrass (Paspalum notatum) pastures and
received a blend of soybean hulls and cottonseed
meal at a daily rate of 6.0 lbs of DM per heifer
throughout the experimental period (d 0 to 130).
The acclimation process (d 11 to 39) consisted
of bringing heifers to the cowpens three times
weekly, where heifers were exposed to common
handling practices and returned to pastures
within two h. Heifer shrunk (after 16 h of feed
and water restriction) BW was collected on d 1
and 192 for calculation of heifer ADG during
the experiment. Heifer puberty status, evaluated
via plasma progesterone concentrations and
trans-rectal ultrasonography, was assessed on d
40 and 50, d 80 and 90, and d 120 and 130.
Heifers were considered pubertal once a corpus
luteum and plasma progesterone concentrations
greater than 1.5 ng/mL (Cooke et al., 2007) were
concurrently detected in one or both evaluations
performed on a 10-d interval.

Blood samples collected prior to (d 10) and at
the end of the acclimation process (d 40) were
also evaluated for plasma cortisol
concentrations. Blood samples were collected
via jugular venipuncture into commercial blood
collection tubes (Vacutainer, 10 mL; Becton
Dickinson, Franklin Lakes, NJ) containing
sodium heparin, placed on ice immediately, and
centrifuged at 2,400 x g for 30 min for plasma
collection. Plasma was frozen at -200C on the
same d of collection. Concentrations of
progesterone and cortisol were determined using
Coat-A-Count solid phase 125I RIA kits (DPC


Diagnostic Products Inc., Los Angeles, CA). All
samples were analyzed in duplicates.

Heifer temperament scores were also obtained
on d 40, following blood collection and
ultrasonography exam, to evaluate treatment
effects. Heifer temperament was assessed by pen
score, chute score, and chute exit velocity. Chute
score was assessed by a single technician based
on a 5-point scale, where 1 = calm, no
movement, and 5 = violent and continuous
struggling. For pen score assessment, heifers
exited the chute and entered a pen containing a
single technician, and were assigned a score on a
5-point scale, where 1 = unalarmed and
unexcited, and 5 = very excited and aggressive
toward the technician in a manner that requires
evasive action to avoid contact between the
technician and heifer. Exit velocity was assessed
by determining the speed of the heifer exiting
the squeeze chute by measuring rate of travel
over a 1.5-m distance with an infrared sensor
(FarmTek Inc., North Wylie, TX). Further,
within each assessment d (d 10 and 40), heifers
were divided in quintiles according to their exit
velocity, and assigned a score from 1 to 5 (exit
score; 1 = slowest heifers; 5 = fastest heifers).
Individual temperament scores were calculated
by averaging heifer chute score, pen score, and
exit score.

Growth, temperament, and physiological data
were analyzed using the MIXED procedure of
SAS (SAS Inst., Inc., Cary, NC). The model
statement contained the effects of treatment,
breed, time variables (when appropriate), and
consequent interactions. Data were analyzed
using heifer(breed x treatment x yr) as random
variable. Results are reported as LS means and
were separated using LSD. Puberty data were
analyzed with the GLM and LOGISTIC
procedure of SAS. The model statement
contained the effects of treatment, breed, time of
estimated puberty establishment, year, and the
appropriate interactions. Significance was set at
P<0.05 and tendencies were determined if P>
0.05 and <0.10.

Results
Acclimated heifers had reduced (P<0.01) ADG
compared with control heifers (1.1 vs. 1.3 lbs/d


2009 Florida BeefReport










respectively; SEM=0.04). Given that both
treatment groups were provided similar pastures
and supplements during the experiment,
treatment effects on ADG can be attributed to
the additional exercise that acclimated heifers
were exposed to during the acclimation period.
During each acclimation event, heifers had to
walk nearly 1.3 miles in addition to the activity
inside the handling facility, whereas control
heifers remained on their pasture. A treatment
effect was also detected (P<0.05) for puberty
attainment. Although age at puberty in cattle is
highly determined by BW and growth rate
(Schillo et al., 1992), heifers exposed to
acclimation procedures reached puberty sooner
than control heifers despite their reduced ADG
(Figure 1).

Acclimated heifers had reduced (P<0.01)
cortisol concentrations compared with control
heifers after the acclimation period (3.8 vs. 5.1
gg/dL; SEM=0.17; Figure 2). Supporting our
results, previous research indicated that
acclimation of cattle to handling procedures was
an alternative to prevent elevated concentrations
of cortisol in response to handling stress
(Crookshank et al., 1979; Andrade et al., 2001;
Curley et al., 2006). However, no treatment
effects were detected for temperament scores
(Table 1), although acclimated heifers had
reduced chute score (P<0.01) compared with
control heifers after the acclimation period
(Table 1). Further, all measurements of
temperament were positively correlated to each
other, and also to cortisol concentrations
(P<0.01; Table 2). The positive correlations
detected among measurements of temperament
and cortisol concentrations reported herein were
also described by others (Stahringer et al. 1990;
Fell et a., 1999; Curley et al., 2006), suggesting
that these three measurements of cattle behavior
during handling can be used as indicators of
temperament and also denote the amount of
stress that the animal is experiencing (Thun et
al., 1998; Sapolsky et al., 2000).

Supporting our main hypothesis and rationale,
acclimated heifers in the present experiment had
reduced cortisol concentrations, decreased chute
score, and hastened onset of puberty compared
with non-acclimated cohorts. Nevertheless, the


mechanisms by which acclimation procedures
hastened puberty attainment regardless of
decreased ADG remain unclear. Based on our
hypothesis, it can be speculated that reduced
cortisol concentrations in acclimated heifers
facilitated the initiation of the physiological
events required for puberty attainment,
particularly the first ovulatory LH surge (Smith
and Dobson, 2002). Although concentrations of
cortisol were only evaluated when heifers were
handled and restrained for blood collection, one
can speculate that acclimated heifers also had
reduced cortisol concentrations compared to
control heifers on a daily basis given that heifers
from both groups were often exposed to brief
human interaction, particularly because of
feeding and traffic of personnel/vehicles within
the research station. Still, additional research
should be conducted to further address these
assumptions.

In conclusion, results from this experiment
indicate that acclimation of Brahman-crossbred
heifers to handling procedures and human
interaction reduced ADG because of the
additional exercise that heifers were exposed to,
but alleviated adrenal steroidogenesis and
hastened onset of puberty. Therefore,
acclimation of Brahman x Angus and Braford
replacement heifers to human handling after
weaning may be an alternative to enhance their
reproductive development, and increase the
efficiency of heifer development programs in
cow-calf operations containing Brahman-
influenced cattle.


2009 Florida BeefReport















Literature Cited

Andrade et al. 2001. Appl. Anim. Behav. Sci. 71:175-181.

Cooke et al. 2007. J. Anim. Sci. 85:2564-2574.

Crookshank et al. 1979. J. Anim. Sci. 48:430-435.

Curley et al. 2006. J. Anim. Sci. 84:3100-3103.

Curley et al. 2008. Horm. Behav. 53:20-27.

Dobson et al. J. Reprod. Fertil. 120:405-410.

Echternkamp. 1984. Theriogenology 22:305-311.

Fell et al. 1999. Aust. J. Exp. Agric. 39:795-802.

Li and Wagner. 1983. Biol. Reprod 29:25-37.

Plasse et al. 1968. J. Anim. Sci. 27:94-100.

Plasse et al. 1970. J. Anim. Sci. 30:63-72.

Rodrigues et al. 2002. Biol. Reprod. 66:603-609.

Sapolsky et al. 2000. Endocr. Rev. 21:55-89.

Schillo et al. 1992. J. Anim. Sci. 70:3994-4005.

Smith and Dobson. 2002. Domest. Anim. Endocrinol. 23:75-85.

Stahringer et al. 1990. Theriogenology 34:393-406.

Thun et al. 1998. Reprod. Dom. Anim. 33:255-260.










'R. F. Cooke, Former Graduate Student; B. R. Austin, Graduate Student; J. V. Yelich, Associate
Professor, UF- IFAS Animal Sciences, Gainesville, FL ; J. D. Arthington, UF-IFAS Range Cattle
Research and Education Center, Ona, FL


2009 Florida BeefReport












Table 1. Temperament measurements, obtained after the acclimation period, of heifers exposed or not
(control) to handling acclimation procedures. '
Item Acclimated Control SEM P-Value

Temperament score 2.46 2.48 0.096 0.93


Chute score 1.37 1.84 0.091 < 0.01


Pen score 2.85 2.72 0.137 0.51


Exit velocity, m/s 2.91 2.74 0.148 0.43
SValues reported are covariately adjusted means.










Table 2. Pearson correlation coefficients among measurements of temperament and plasma cortisol
concentrations of heifers.

Item Cortisol Chute score Exit velocity


Chute score 0.44
< 0.01

Exit velocity 0.55 0.46
< 0.01 < 0.01

Pen score 0.48 0.40 0.69
< 0.01 < 0.01 < 0.01

SUpper row = correlation coefficients. Lower row = P-values.


2009 Florida BeefReport











O Acclimated


80 -
70 -
60 -
50 -
40 -
30 -
20 -
10 -
0-


* Control


-


d 40 and 50


d 80 and 90


d 120 and 130


Figure 1. Puberty attainment of heifers exposed or not (control) to handling acclimation
procedures (d 11 to 39). Heifers were considered pubertal once a corpus luteum and plasma P4
concentrations greater than 1.5 ng/mL were concurrently detected in one or both evaluations
performed on a 10-d interval. A treatment effect was detected (P=0.02; SEM=6.5).


0 1 1


O Acclimated


* Control


Pre-acclimation (d 10)


Post-acclimation (d 40)


Figure 2. Plasma cortisol concentrations of heifers exposed or not (control) to handling acclimation
procedures (d 11 to 39). Samples collected on d 10 served as covariate, therefore results reported for d 40
are covariately adjusted least square means. Acclimated heifers had reduced (P<0.01; SEM=0.17)
concentrations of cortisol compared to control heifers on d 40.


2009 Florida BeefReport


100 -
90 -


r_


d 0 and 10




Full Text

PAGE 1

Effects of A cclimation to H andling on P erformance, R eproductive, and P hysiological R esponses of Brahman crossbred H eifers R. F. Cooke 1 B. R. Austin J. V. Yelich J. D. Arthington Summary The objective of this experiment was to evaluate the effects of acclimation to human handling on growth, plasma concentrations of cortisol, and puberty attainment of Brahman-crossbred heifers. Over two consecutive yr, 37 Braford and 43 Brahman Angus heifers were assigned randomly to receive or not the acclimation treatment within 30 d after weaning. The acclimation process consisted of bringing heifers to the cowpens three times weekly during four consecutive wk, where heifers were exposed to common handling practices and returned to pastures within 2 h. Heifers were maintained in bahiagrass (Paspalum notatum) pastures and received a blend of soybean hulls and cottonseed meal at a daily rate of 6.0 lbs of DM per heifer during the experiment (d 0 to 130). Blood samples were collected prior to and at the end of the acclimation process for determination of cortisol concentrations. Puberty status was assessed monthly during the experiment. Acclimated heifers had decreased (P<0.05) average daily gain (ADG) compared to control heifers (1.1 vs. 1.3 lbs/d, respectively). Attainment of puberty, however, was hastened (P<0.01) for acclimated heifers. Further, acclimated heifers had reduced cortisol concentrations compared to control heifers after respectively). Results from this experiment indicated that although acclimation decreased body weight gain, it enhanced the attainment of puberty in Brahman-crossbred heifers. Introduction Age at puberty is influenced by breed type, and heifers containing Brahman breeding typically reach puberty after 15 mo of age (Plasse et al., 1968; Rodrigues et al., 2002). In addition to this genetic effect, Brahman-crossbred heifers are often described as temperamental, and this trait is expected to further negatively influence their reproductive function (Plasse et al., 1970). Cattle with excitable temperament experience stimulated secretion and circulating concentrations of ACTH and cortisol (Curley et al., 2008). These hormones directly impair the mechanisms responsible for puberty establishment of heifers, such as synthesis and release of gonadotropins (Li and Wagner, 1983; Do bson et al., 2000). However, acclimation of beef females to handling has been reported to alleviate these negative physiological effects of temperament on reproduction (Echternkamp, 1984). Based on these previous observations, we hypothesized that Brahman-crossbred heifers exposed to handling acclimation procedures after weaning would experience improved temperament, alleviated adrenal steroidogenesis, and enhanced reproductive performance. The objectives of the present experiment were to compare growth, temperament, plasma Acclimation to human handling after weaning hastened the onset of puberty in Brahman crossbred heifers.

PAGE 2

measurements, puberty attainment and pregnancy rates of Brahman Angus and Braford heifers exposed or not to acclimation procedures. Materials and Methods Over two consecutive yr, 37 Braford (37.5% Brahman + 62.5% Hereford) and 43 Brahman Angus (approximately 25% Brahman) heifers were initially evaluated for puberty status via trans-rectal ultrasonography (d 0 and 10) and for temperament by measurements of chute score, pen score, and exit velocity (d 10) within 30 d after weaning. On d 10, heifers were stratified by puberty status, temperament and body weight (BW), and randomly assigned to control or acclimation treatment. Heifers were maintained in bahiagrass ( Paspalum notatum ) pastures and received a blend of soybean hulls and cottonseed meal at a daily rate of 6.0 lbs of DM per heifer throughout the experimental period (d 0 to 130). The acclimation process (d 11 to 39) consisted of bringing heifers to the cowpens three times weekly, where heifers were exposed to common handling practices and returned to pastures within two h. Heifer shrunk (after 16 h of feed and water restriction) BW was collected on d 1 and 192 for calculation of heifer ADG during the experiment. Heifer puberty status, evaluated via plasma progesterone concentrations and trans-rectal ultrasonography, was assessed on d 40 and 50, d 80 and 90, and d 120 and 130. Heifers were considered pubertal once a corpus luteum and plasma progesterone concentrations greater than 1.5 ng/mL (Cooke et al., 2007) were concurrently detected in one or both evaluations performed on a 10-d interval. Blood samples collected prior to (d 10) and at the end of the acclimation process (d 40) were also evaluated for plasma cortisol concentrations. Bl ood samples were collected via jugular venipuncture into commercial blood collection tubes (Vacutainer, 10 mL; Becton Dickinson, Franklin Lakes, NJ) containing sodium heparin, placed on ice immediately, and centrifuged at 2,400 g for 30 min for plasma co llection. Plasma was frozen at -20C on the same d of collection. Concentrations of progesterone and cortisol were determined using Coat-A-Count solid phase 125 I RIA kits (DPC Diagnostic Products Inc., Los Angeles, CA). All samples were analyzed in duplicates. Heifer temperament scores were also obtained on d 40, following blood collection and ultrasonography exam, to evaluate treatment effects. Heifer temperament was assessed by pen score, chute score, and chute exit velocity. Chute score was assessed by a single technician based on a 5-point scale, where 1 = calm, no movement, and 5 = violent and continuous struggling. For pen score assessment, heifers exited the chute and entered a pen containing a single technician, and were assigned a score on a 5-point scale, where 1 = unalarmed and unexcited, and 5 = very excited and aggressive toward the technician in a manner that requires evasive action to avoid contact between the technician and heifer. Exit velocity was assessed by determining the speed of the heifer exiting the squeeze chute by measuring rate of travel over a 1.5-m distance with an infrared sensor (FarmTek Inc., North Wylie, TX). Further, within each assessment d (d 10 and 40), heifers were divided in quintiles according to their exit velocity, and assigned a score from 1 to 5 (exit score; 1 = slowest heifers; 5 = fastest heifers). Individual temperament scores were calculated by averaging heifer chute score, pen score, and exit score. Growth, temperament, and physiological data were analyzed using the MIXED procedure of SAS (SAS Inst., Inc., Cary, NC). The model statement contained the effects of treatment, breed, time variables (when appropriate), and consequent interactions. Data were analyzed using heifer(breed treatment yr) as rando m variable. Results are reported as LS means and were separated using LSD. Puberty data were analyzed with the GLM and LOGISTIC procedure of SAS. The model statement contained the effects of treatment, breed, time of estimated puberty establishment, year, and the appropriate interactions. Significance was set at P P > Results Acclimated heifers had reduced ( P <0.01) ADG compared with control heifers (1.1 vs. 1.3 lbs/d

PAGE 3

respectively; SEM=0.04). Given that both treatment groups were provided similar pastures and supplements during the experiment, treatment effects on ADG can be attributed to the additional exercise that acclimated heifers were exposed to during the acclimation period. During each acclimation event, heifers had to walk nearly 1.3 miles in addition to the activity inside the handling facility, whereas control heifers remained on their pasture. A treatment effect was also detected (P<0.05) for puberty attainment. Although age at puberty in cattle is highly determined by BW and growth rate (Schillo et al., 1992), heifers exposed to acclimation procedures reached puberty sooner than control heifers despite their reduced ADG (Figure 1). Acclimated heifers had reduced ( P <0.01) cortisol concentrations compared with control heifers after the acclimation period (3.8 vs. 5.1 results, previous research indicated that acclimation of cattle to handling procedures was an alternative to prevent elevated concentrations of cortisol in response to handling stress (Crookshank et al., 1979; Andrade et al., 2001; Curley et al., 2006). However, no treatment effects were detected for temperament scores (Table 1), although acclimated heifers had reduced chute score ( P <0.01) compared with control heifers after the acclimation period (Table 1). Further, all measurements of temperament were positively correlated to each other, and also to cortisol concentrations ( P <0.01; Table 2). The positive correlations detected among measurements of temperament and cortisol concentrations reported herein were also described by others (Stahringer et al. 1990; Fell et a., 1999; Curley et al., 2006), suggesting that these three measurements of cattle behavior during handling can be used as indicators of temperament and also denote the amount of stress that the animal is experiencing (Thun et al., 1998; Sapolsky et al., 2000). Supporting our main hypothesis and rationale, acclimated heifers in the present experiment had reduced cortisol concentrations, decreased chute score, and hastened onset of puberty compared with non-acclimated cohorts. Nevertheless, the mechanisms by which acclimation procedures hastened puberty attainment regardless of decreased ADG remain unclear. Based on our hypothesis, it can be speculated that reduced cortisol concentrations in acclimated heifers facilitated the initiation of the physiological events required for puberty attainment, particularly the first ovulatory LH surge (Smith and Dobson, 2002). Although concentrations of cortisol were only evaluated when heifers were handled and restrained for blood collection, one can speculate that acclimated heifers also had reduced cortisol concentrations compared to control heifers on a daily basis given that heifer s from both groups were often exposed to brief human interaction, particularly because of feeding and traffic of personnel/vehicles within the research station. Still, additional research should be conducted to further address these assumptions. In conclusion, results from this experiment indicate that acclimation of Brahman-crossbred heifers to handling procedures and human interaction reduced ADG because of the additional exercise that heifers were exposed to, but alleviated adrenal steroidogenesis and hastened onset of puberty. Therefore, acclimation of Brahman Angus and Braford replacement heifers to human handling after weaning may be an alternative to enhance their reproductive development, and increase the efficiency of heifer development programs in cow-calf operations containing Brahmaninfluenced cattle.

PAGE 4

Literature Cited Andrade et al. 2001. Appl. Anim. Behav. Sci. 71:175 181. Cooke et al. 2007. J. Anim. Sci. 85:2564 2574. Crookshank et al. 1979. J. Anim. Sci. 48:430 435. Curley et al. 2 006. J. Anim. Sci. 84:3100 3103. Curley et al. 2008. Horm. Behav. 53:20 27. Dobson et al. J. Reprod. Fertil. 120:405 410. Echternkamp. 1984. Theriogenology 22:305 311. Fell et al. 1999. Aust. J. Exp. Agric. 39:795 802. Li and Wagner. 1983. Biol. Reprod 29:25 37. Plasse et al. 1968. J. Anim. Sci. 27:94 100. Plasse et al. 1970. J. Anim. Sci. 30:63 72. Rodrigues et al. 2002. Biol. Reprod. 66:603 609. Sapolsky et al. 2000. Endocr. Rev. 21:55 89. Schillo et al. 1992. J. Anim. Sci. 70:3994 4005. Smith and Dobson. 2002. Domest. Anim. Endocrinol. 23:75 85. Stahringer et al. 1990. Theriogenology 34:393 406. Thun et al. 1998. Reprod. Dom. Anim. 33:255 260. 1 R. F. Cooke, Former Graduate Student; B. R. Austin, Graduate Student; J. V. Yelich, Associate Prof essor, UF IFAS Animal Sciences Gainesville, FL ; J. D. Arthington, UF IFAS Range Cattle Research and Education Center, Ona, FL

PAGE 5

Table 1 Temperament measurements, obtained after the acclimation period, of heifers exposed or not (control) to handling acclimation procedures. 1 Item Acclimated Control SEM P Value Temperament score 2.46 2.48 0.096 0.93 Chute score 1.37 1.84 0.091 < 0.01 Pen score 2.85 2.72 0.137 0.51 Exit velocity, m/s 2.91 2.74 0.148 0.43 1 Values reported are covariately adjusted means. Table 2 Pearson correlation coefficients among measurements of temperament and plasma cortisol concentrations of heif ers. 1 Item Cortisol Chute score Exit velocity Chute score 0.44 < 0.01 Exit velocity 0.55 0.46 < 0.01 < 0.01 Pen score 0.48 0.40 0.69 < 0.01 < 0.01 < 0.01 1 Upper row = correlation coefficients. Lower row = P values.

PAGE 6

0 10 20 30 40 50 60 70 80 90 100 d 0 and 10 d 40 and 50 d 80 and 90 d 120 and 130 Pubertal heifer, % Acclimated Control Figure 1. Puberty attainment of heifers exposed or not (control) to handling acclimation procedures (d 11 to 39). Heifers were considered pubertal once a corpu s luteum and plasma P4 concentrations greater than 1.5 ng/mL were concurrently detected in one or both evaluations performed on a 10 d interval. A treatment effect was detected ( P =0.02; SEM=6.5). 0 1 2 3 4 5 6 7 Pre acclimation (d 10) Post acclimation (d 40) Plasma cortisol, g/dL Acclimated Control Figure 2. Plasma cortisol concentrations of heifers exposed or not (control) to handling acclimation procedures (d 11 to 39). Samples collected on d 10 served as covariate, therefore results reported for d 40 are covariately adjusted least square means. Acclimated heifers had redu ced ( P <0.01; SEM=0.17) concentrations of cortisol compared to control heifers on d 40.