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Brought to you by Kansas State University
College of Veterinary Medicine - Agricultural Practices Section
October 2007 |
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Contents:
KSU Career Opportunities Workshop
International Symposium on
Beef Cattle Welfare
Effect of feeding places on
performance
GnRH-induced ovulation in beef
heifers
Heat load Index for Feedlot cattle
Ractopamine effect on
performance, feed intake
KSU
Veterinary Career Opportunities Workshop
Kansas State University Colleges of Veterinary Medicine and Business
Administration invite you to attend the Veterinary Career Opportunities
Workshop, November 2-3, 2007. The goal of this meeting is to help busy,
practicing veterinarians find the right person to join their practice as
a new associate. Education includes skills related to finding new
associates, graduating student expectations, fair benefits packages, and
reasonable job descriptions. This meeting is a great chance to learn
about recruiting and hiring the new associate. Practitioners will meet
and interact with current veterinary students who are interested in
mixed animal practice. Upon leaving the Workshop, practitioners will
have a professional, printed job description and a wealth of new
knowledge to help build their practices. The conference will be in
Manhattan, KS and ten hours of continuing education credit will be
awarded for attendance.
Veterinary students from Kansas State University will attend a portion
of the Workshop. Brief, mock, interviews between the students and
practitioners will be conducted to allow both prospective employers and
new associates to discuss expectations related to the specific job.
For a full schedule of events and
to register please contact us:
By phone: 785-532-5569
By web:
http://www.vet.ksu.edu/CE/vcow07.htm
International
Symposium on Beef Cattle Welfare
It is the pleasure of the Beef Cattle Institute at Kansas State
University to inform you of the International Symposium on Beef Cattle
Welfare. Notable beef cattle welfare experts from numerous universities
around the world have committed to making the trip to Manhattan, Kansas
on May 29 and 30, 2008. Also, representatives from USDA, FDA, AVMA and
NCBA will be speaking on their perspectives of current and future beef
cattle welfare issues.
Please hold the date to join us in the Little Apple! May is a wonderful
time of year to visit the Flint Hills and Konza Prairie.
Effect of feeding
places on performance
Seventy-two Friesian calves (BW = 102.0 ± 1.8 kg) were bought from a
commercial calf farm and distributed to a factorial arrangement of
treatments in a complete block design with 3 treatments and 3 blocks of
similar fasted BW to study the effect of increasing the number of
feeding places per pen on performance, behavior, and welfare indicators
during the 4 wk after arrival. Treatments consisted of 1 (T1), 2 (T2),
or 4 (T4) concentrate feeding places/pen (8 calves/pen). Concentrate and
straw were fed at 0830 in individual feeders and animals were allowed to
consume on an ad libitum basis. Dry matter intake and ADG were recorded
weekly, and blood samples were taken on d 0 (before transport), 7, 14,
21, and 28. Time spent in maintenance activities, number of
displacements between calves, and the angular dominance value (ADV) were
registered at wk 1 and 3 after arrival. Increasing the number of feeding
places per pen resulted in a quadratic response of concentrate and total
DMI, ADG, and BW during the 28-d period, with T1 showing the lowest
values. Straw intake and the within-pen SD of ADG tended to decrease
linearly (P = 0.10) as the number of feeding places per pen increased.
During the 4-wk receiving period,
and particularly on d 7 after arrival, serum NEFA responded
quadratically with T1 and T2 calves showing the greatest values. With
increasing number of concentrate feeders, the average time spent lying
increased (P = 0.001), standing time decreased linearly (P = 0.001), and
the diurnal feeding pattern changed (concentrate eating time increased
but straw eating time decreased during peak feeding times, P < 0.05).
The number of displacements from the concentrate feeders responded
quadratically (P < 0.001) with increasing number of feeding places per
pen, with T4 calves showing the lowest levels of aggression. In T1
calves, increasing ADV resulted in a linear decrease (P = 0.03) of ADG
at wk 1 with a quadratic effect at wk 3 (P < 0.01). In T2 calves,
increasing ADV resulted in a linear decrease (P = 0.04) of ADG at wk 1
but a linear increase (P = 0.02) at wk 3. No effect of social rank on
ADG was observed in T4 calves (P > 0.20). Increasing social pressure at
the concentrate feeders beyond the threshold of 4 heifers per feeder had
a negative effect on performance. Within-pen variability in performance
increased linearly as a consequence of greater effects of social
dominance. Physiological indicators of welfare were not consistently
affected by treatments.
Gonzalez, L.A., A. Ferret, X.
Manteca, et al. Effect of the number of concentrate feeding places per
pen on performance, behavior, and welfare indicators of Friesian calves
during the first month after arrival at the feedlot. 2007 J. Anim Sci.
published online October 16, 2007, 10.2527/jas.2007-0362
GnRH-induced ovulation
in beef heifers
The Co-Synch protocol has been used to synchronize ovulation and
facilitate fixed-time AI in beef cattle. Establishment and maintenance
of pregnancy was negatively affected, in previous studies, by GnRH-induced
ovulation of small dominant follicles ( 11 mm). The reason for the
presence of small follicles at the second GnRH (GnRH 2) is not clear.
The objectives of this study were: 1) to determine the effect of
ovulatory response at the first GnRH (GnRH 1) on diameter and variation
in diameter of the largest follicle at GnRH 2; and 2) to determine the
effect of day of the cycle (stage of a follicular wave) on GnRH-induced
luteinizing hormone (LH) release, and the resulting ovulatory response
after GnRH 1 and 2. Two experiments used pubertal beef heifers
synchronized to be on different days of the estrous cycle (d 2, 5, 10,
15, and 18 after estrus) in which a dominant follicle would or would not
respond to GnRH 1. Ovulatory response to GnRH 1 did not affect size or
variation in diameter of the largest follicle at GnRH 2 in Exp.1 or 2.
In Exp. 1, ovulatory response after GnRH 1 (0/14a,
12/13b, 4/13ac, 9/13bc, and 2/10a in the d 2, 5, 10, 15, and 18 groups;
abcP < 0.05) and GnRH 2 (13/14a, 12/13a, 12/13a, 2/13b, and 2/10b in the
d 2, 5, 10, 15, and 18 groups, respectively; abP < 0.05) was affected by
day of the cycle. In Exp. 2, day of the cycle also affected the
proportion of heifers ovulating after GnRH 1 (0/7a, 8/8b, 0/6a 5/8ab,
and 5/8ab of the d 2, 5, 10, 15, and 18 heifers, respectively; abcP <
0.05) and GnRH 2 (3/7ab, 8/8b, 5/6b, 1/8a, and 2/8a of the d 2, 5, 10,
15, and 18 heifers, respectively; abP < 0.05). In both experiments,
heifers receiving GnRH 1 on d 15 and 18 had a greater (P < .05)
occurrence of luteolysis before PG injection and expression of estrus
than heifers treated on d 2, 5, and 10. The GnRH-induced LH surge was of
greatest magnitude in heifers receiving GnRH 1 on d 18 of the cycle
followed by d 5, 15, 10, and 2 (9,054b, 5,774bc, 4,672c, 2,548c, and
915d arbitrary units; respectively; abcdP < 0.05). In summary, ovulatory
response to GnRH 1 did not affect size of the dominant follicle at GnRH
2. Day of the cycle when GnRH 1 was delivered affected dominant follicle
size at GnRH 2. Treatment with GnRH 1 in the earlier part of the estrous
cycle (on or before d 10) increased the proportion of dominant follicles
that were large enough to respond to GnRH 2 ( 10 mm) and increased
ovulatory response after GnRH 2.
Atkins, J.A., D.C. Busch, J.F. Bader, D.H. Keisler, D.J. Patterson, M.C.
Lucy, M.F. Smith. GnRH-induced
ovulation and luteinizing hormone release in beef heifers:
Effect of day of cycle. 2007 J. Anim Sci. published online October 2,
2007, 10.2527/jas.2007-0277
Heat load Index for
Feedlot cattle
The ability to predict effects of extreme climatic variables on
livestock is important in terms of welfare and performance. An index
combining temperature and humidity (THI) has been used for over 4
decades to assess heat stress in cattle. However, the THI does not
include important climatic variables such as solar load and wind speed
(WS; m/s). Likewise, it does not include management factors (the effect
of shade) or animal factors (genotype differences). Over 8 summers a
total of 11,669 Bos taurus steers, 2,344 Bos taurus crossbred steers,
2,142 Bos taurus x Bos indicus steers, and 1,595 Bos indicus steers were
used to develop and test a heat load index for feedlot cattle. A new
heat load index (HLI) incorporating black globe temperature (BG; °C),
relative humidity (RH; decimal form) and WS has been initially developed
using panting score (PS) of 2,490 Angus steers. The HLI consists of 2
parts based on a BG temperature threshold of 25 °C: HLIBG>25 = 8.62 +
(0.38 x RH) + (1.55 x BG) - (0.5 x WS) + [e(2.4 - WS)], and HLIBG<25 =
10.66 + (0.28 x RH) + (1.3 x BG) - WS. Where e = the base of the natural
logarithm. A threshold HLI above which cattle of different genotypes
gain body heat was developed for 7 genotypes. The threshold for unshaded
black Bos taurus steers is 86 and for unshaded Bos indicus (100%) the
threshold is 96. Threshold
adjustments were developed for factors such as coat color, health
status, access to shade, drinking water temperature, and manure
management. Upward and downward adjustment are possible; upward
adjustments occur where cattle have access to shade (+3 to +7) and
downward when cattle are sick (-5). A related measure, the accumulated
heat load (AHL) model also was developed following the development of
the HLI. The AHL is a measure of the animals heat load balance and is
determined by the duration of exposure above the threshold HLI. The THI
and THI-hours (hours above a THI threshold) were compared to HLI and AHL.
The relationship between tympanic temperature and the average HLI and
THI for the previous 24 h were (R2 = 0.67; P < 0.001) and (R2 = 0.26; P
< 0.001) respectively. The R2 between HLI and panting score, and AHL and
PS were positive (P < 0.001). The R2 were 0.93 and 0.92 for HLI and AHL
respectively. The R2 for THI was 0.61 (P < 0.001), and for THI-hours R2
= 0.37 (P < 0.001). The HLI and the AHL are successful in predicting
panting score responses of different cattle genotypes during periods of
high heat load.
Gaughan, J.B., T.L. Mader, S.M. Holt, A. Lisle.
A new heat load index for feedlot cattle.
2007 J. Anim Sci. published online October 2, 2007,
10.2527/jas.2007-0305
Ractopamine effect on
performance, feed intake and acid-base balance
Two experiments evaluated effects of
ractopamine hydrochloride (RAC) on performance, intake patterns, and
acid-base balance of feedlot cattle. In Exp. 1, 360 crossbred steers (Brangus,
British, and British x Continental breeding; initial BW = 545 kg) were
used in a study with a 3 x 3 factorial design to study the effects of
dose [0, 100, or 200 mg/(steer•d) of RAC] and duration (28, 35, or 42 d)
of feeding of RAC in a randomized complete block design (9 treatments, 8
pens/treatment). No dose x duration interactions were detected (P >
0.10). As RAC dose increased, final BW (FBW; P = 0.01), ADG (P < 0.01),
and G:F (P < 0.01) increased linearly. As duration of feeding increased,
ADG increased quadratically (P = 0.04), with tendencies for quadratic
effects for FBW (P = 0.06), DMI (P = 0.07), and G:F (P = 0.09). Hot
carcass weight increased linearly (P = 0.02) as dose of RAC increased.
Thus, increasing the dose of RAC from 0 to 200 mg/(steer•d) and the
duration of feeding from 28 to 42 d improved feedlot performance,
although quadratic responses for duration of feeding indicated little
improvement as the duration was extended from 35 to 42 d.
In Exp. 2, 12 crossbred beef steers (BW = 593 kg)
were used in a completely random design to evaluate the effects of RAC
[0 or 200 mg/(steer•d) for 30 d; 6 steers/treatment] on rate of intake,
daily variation in intake patterns, and acid-base balance. To assess
intake patterns, absolute values of daily deviations in feed delivered
to each steer relative to the total quantity of feed delivered were
analyzed as repeated measures. There were no differences (P > 0.10) in
feedlot performance, urine pH, blood gas measurements, or variation in
intake patterns between RAC and control cattle, but steers fed RAC had
increased (P = 0.04) LM area, decreased (P = 0.03) yield grade, and
increased (P < 0.10) time to consume 50 and 75% of daily intake relative
to control steers. Our results suggest that feeding RAC for 35 d at 200
mg/(steer•d) provided optimal performance, and no effects on acid-base
balance or variation in intake patterns of finishing steers were noted
with RAC fed at 200 mg/(steer•d) over a 30-d period.
Abney, C.S., J.T. Vasconcelos, J.P. McMeniman, S.A.
Keyser, K.R. Wilson, G.J. Vogel, and M.L. Galyean.
Effects of ractopamine hydrochloride on
performance, rate and variation in feed intake, and acid-base balance in
feedlot cattle. 2007 J. Anim Sci.
85:3090-3098.
___________________________________________________________________
Beef Research News is produced by the Agricultural Practices section at
Kansas State University. To modify your subscription to this service
please email Erin Evanson ( eevanson@vet.ksu.edu )
For more information please contact:
Brad White
Beef Production Medicine
Q211 Mosier Hall
Manhattan, KS 66506
bwhite@vet.ksu.edu
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