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Kansas State University

 

Beef Research News
Brought to you by Kansas State University College of Veterinary Medicine - Farm Animal Section
October 2007

 

 

 

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.

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Beef Research News is produced by the Farm Animal 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