Beef Research News
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Three experiments were conducted to determine the effects of low-dose progesterone presynchronization and eCG on pregnancy rates to GnRH-based, timed-AI (TAI) in beef cattle (GnRH on Day 0, PGF2α on Day 7, with GnRH and TAI on Day 9, 54–56h after PGF2α). Experiments 1 and 2 were 2×2 factorials with presynchronization (with or without a once-used CIDR; Days −15 to 0 in Experiment 1 and Days −7 to 0, with PGF2α at insertion, in Experiment 2), and with or without 400IU eCG on Day 7 in suckled cows. In Experiment 3, suckled cows and nulliparous heifers were either presynchronized with a twice-used CIDR (Days −5 to 0) and PGF2α at insertion, or no treatment prior to insertion of a new CIDR (Days 0–7). Presynchronization increased (P<0.05) ovulation rate to GnRH on Day 0 (75.0% vs 48.7%, 76.7% vs 55.0%, and 60.0% vs 36.1% for Experiments 1, 2, and 3, respectively), increased the diameter of the preovulatory follicle in Experiments 1 and 2, and increased the response to PGF2α (regardless of parity) in Experiment 1 (P<0.01), and in primiparous cows in Experiment 2 (P<0.01). Effects of presynchronization on pregnancy rates (53.4% vs 54.1%, 57.7% vs 45.3%, and 54.3% vs 44.4% for Experiments 1, 2, and 3, respectively) were influenced by parity and eCG (P<0.05). Treatment with eCG had no effect (P>0.05) on the diameter of the preovulatory follicle (Experiment 1), or the response to PGF2α (Experiments 1 and 2), but tended (P=0.08) to improve pregnancy rates, especially in primiparous cows that were not presynchronized (P<0.01). However, the effects of eCG and presynchronization were not additive.
J.A. Smalla, , M.G. Colazob, J.P. Kastelicc, R.J. Mapletoftd. Effects of progesterone presynchronization and eCG on pregnancy rates to GnRH-based, timed-AI in beef cattle. Theriogenology 2009 71(4): 698-706.
Effects of implanting and feeding zilpaterol hydrochloride on performance of fed cows
Sixty crossbred cull cows were used to determine the combined effects of a trenbolone acetate-estradiol implant and feeding zilpaterol hydrochloride on performance, carcass characteristics, and subprimal yields of mature cows fed for 70 d. Cows were assigned to 1 of 5 treatments: 1) grazing native grass pasture (G); 2) concentrate-fed (C) a grain sorghum-sorghum silage diet; 3) concentrate-fed and implanted (CI) with Revalor-200 (trenbolone acetate-estradiol); 4) concentrate-fed and fed Zilmax (zilpaterol hydrochloride) beginning on d 38 of the feeding period (CZ); and 5) concentrate-fed, implanted, and fed Zilmax beginning on d 38 (CIZ). The concentrate diet consisted primarily of ground grain sorghum and sorghum silage. During the last 34 d of the feeding trial, concentrate-fed (C, CI, CZ, and CIZ) cows had greater (P < 0.05) gains than G cows. Hot carcass weights and dressing percentages were greater (P < 0.05) for the concentrate-fed cows than for G cows. Longissimus muscle area was largest (P < 0.05) for CIZ cows, whereas subprimal weights from the chuck were heavier (P < 0.05) from CIZ cows than C and G cows, and carcasses from CI and CZ cows had heavier (P < 0.05) chuck subprimal weights than G cows. Rib and round subprimal weights were heavier (P < 0.05) for concentrate-fed cows compared with G cows. In addition, carcasses from CIZ cows had heavier (P < 0.05) total subprimal weights, and total subprimals were a greater percentage of their initial BW than C cows. Rib cut-out and total soft tissue weights from the 9-10-11th rib were less (P < 0.05) for G cows than concentrate-fed cows. Feeding cull cows a concentrate diet increased carcass weight, dressing percentage, and subprimal yields compared with feeding cows a grass-based pasture diet, and the combination of a trenbolone acetate-estradiol implant and feeding zilpaterol hydrochloride can maximize trimmed beef yields from cull cows fed a high-concentrate diet.
S. Neill, J. A. Unruh, T. T. Marston, J. R. Jaeger, M. C. Hunt and J. J. Higgins. Effects of implanting and feeding zilpaterol hydrochloride on performance, carcass characteristics, and subprimal beef yields of fed cows. J. Anim Sci. 2009. 87:704-710. doi:10.2527/jas.2008-1254
Behavior to predict and identify ill health in animals
We review recent research in one of the oldest and most important applications of ethology: evaluating animal health. Traditionally, such evaluations have been based on subjective assessments of debilitative signs; animals are judged ill when they appear depressed or off feed. Such assessments are prone to error but can be dramatically improved with training using well-defined clinical criteria. The availability of new technology to automatically record behaviors allows for increased use of objective measures; automated measures of feeding behavior and intake are increasingly available in commercial agriculture, and recent work has shown these to be valuable indicators of illness. Research has also identified behaviors indicative of risk of disease or injury. For example, the time spent standing on wet, concrete surfaces can be used to predict susceptibility to hoof injuries in dairy cattle, and time spent nuzzling the udder of the sow can predict the risk of crushing in piglets. One conceptual advance has been to view decreased exploration, feeding, social, sexual, and other behaviors as a coordinated response that helps afflicted individuals recover from illness. We argue that the sickness behaviors most likely to decline are those that provide longer-term fitness benefits (such as play), as animals divert resources to those functions of critical short-term value such as maintaining body temperature. We urge future research assessing the strength of motivation to express sickness behaviors, allowing for quantitative estimates of how sick an animal feels. Finally, we call for new theoretical and empirical work on behaviors that may act to signal health status, including behaviors that have evolved as honest (i.e., reliable) signals of condition for offspring-parent, inter- and intra-sexual, and predator-prey communication.
D. M. Weary, J. M. Huzzey and M. A. G. von Keyserlingk. BOARD-INVITED REVIEW: Using behavior to predict and identify ill health in animals. J. Anim Sci. 2009. 87:770-777. doi:10.2527/jas.2008-1297
We determined whether an ovulatory estrus could be resynchronized in previously synchronized, AI nonpregnant cows without compromising pregnancy from the previous synchronized ovulation or to those inseminated at the resynchronized estrus. Ovulation was synchronized in 937 suckled beef cows at 6 locations using a CO-Synch + progesterone insert (controlled internal drug release; CIDR) protocol [a 100-µg injection of GnRH at the time of progesterone insert, followed in 7 d by a 25-mg injection of PGF2 at insert removal; at 60 h after PGF2 , cows received a fixed-time AI (TAI) plus a second injection of GnRH]. After initial TAI, the cows were assigned randomly to 1 of 4 treatments: 1) untreated (control; n = 237); 2) progesterone insert at 5 d after TAI and removed 14 d after TAI (CIDR5–14; n = 234); 3) progesterone insert placed at 14 d after TAI and removed 21 d after TAI (CIDR14–21; n = 232); or 4) progesterone insert at 5 d after TAI and removed 14 d after TAI and then a new CIDR inserted at 14 d and removed 21 d after TAI (CIDR5–21; n = 234). After TAI, cows were observed twice daily until 25 d after TAI for estrus and inseminated according to the AM-PM rule. Pregnancy was determined at 30 and 60 d after TAI to determine conception to the first and second AI. Pregnancy rates to TAI were similar for control (55%), CIDR5–14 (53%), CIDR14–21 (48%), and CIDR5–21 (53%). A greater (P < 0.05) proportion of nonpregnant cows was detected in estrus in the CIDR5–21 (76/110, 69%) and CIDR14–21 (77/120, 64%) treatments than in controls (44/106, 42%) and CIDR5–14 (39/109, 36%) cows. Although overall pregnancy rates after second AI service were similar, combined conception rates of treatments without a CIDR from d 14 to 21 [68.7% (57/83); control and CIDR5–14 treatments] were greater (P = 0.03) than those with a CIDR during that same interval [53.5% (82/153); CIDR5–21 and CIDR14–21 treatments]. We conclude that placement of a progesterone insert 5 d after a TAI did not compromise or enhance pregnancy rates to TAI; however, conception rates of nonpregnant cows inseminated after a detected estrus were compromised when resynchronized with a CIDR from d 5 or 14 until 21 d after TAI.
J. E. Larson, K. N. Thielen, B. J. Funnell, J. S. Stevenson, D. J. Kesler and G. C. Lamb. Influence of a controlled internal drug release after fixed-time artificial insemination on pregnancy rates and returns to estrus of nonpregnant cows.
J. Anim Sci. 2009. 87:914-921. doi:10.2527/jas.2008-1443.
The objective of this study was to investigate the effects of bovine respiratory disease (BRD) complex on economically important production traits with the use of health records in combination with lung lesion scores obtained at harvest. Records from 5,976 animals were used in this study from cattle that were managed in Midwestern feedlots. Average daily gain for 3 different feeding periods (acclimation, on-test, and overall test) along with final BW were evaluated as performance measures. Hot carcass weight, LM area, subcutaneous fat cover, and marbling score were collected at harvest. All calves were monitored by experienced feedlot personnel and treated according to the specific health protocol of each feedlot. Incidence of BRD was observed at a rate of 8.17% and lung lesions at harvest were present in 61.9% of cattle from a sub population (n = 1,665). From this group of cattle, the overall incidence of BRD, defined as incidence of BRD and/or cattle with lung lesions at the packing plant, was 64.4%. Incidence of BRD in the feedlot decreased ADG during both the acclimation period (0.37 ± 0.03 kg) and the overall test period (0.07 ± 0.01 kg). Incidence of BRD also had significant effects on HCW and marbling score with reduction of 8.16 ± 1.38 kg and 0.13 ± 0.04, respectively in treated cattle. The adverse effects on production traits tended to increase as the number of treatment increased. Potential decrease in performance and carcass merit observed in this study were associated with a decline of $23.23, $30.15, and $54.01 in carcass value when comparing cattle never treated to cattle treated once, twice, or three or more times, respectively. The presence of lung lesions did not have a significant effect on any of the traits; however, there was an association between the presence of active bronchial lymph nodes and lower productivity of feedlot cattle.
M. J. Schneider, R. G. Tait, Jr., W. D. Busby and J. M. Reecy. An evaluation of bovine respiratory disease complex in feedlot cattle: Impact on performance and carcass traits using treatment records and lung lesion scores. Published online first on January 30, 2009 J. Anim Sci. 1910. doi:10.2527/jas.2008-1283
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