Beef Research News
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Supplemental zinc source effect on heifer immunity and performance
The effect of different sources of supplemental Zinc on receiving-period performance, morbidity, humoral immune response, and finishing performance and carcass characteristics of beef heifers was evaluated through two experiments. Experiment one compared no supplement (control) or 75 mg Zn/kg of DM from zinc sulfate, zinc methionine, or zinc propionate. The 97 crossbred heifers (initial BW = 223.4 kg) were monitored during a 35-d receiving period for BRD and serum samples were collected for Zn analysis on d 0, 14, and 28. After receiving, heifers were adapted to and fed a high-concentrate diet with no supplemental Zn for 42 days. The finishing period consisted of assigning heifers to same concentrations and sources of supplemental Zn as receiving period and fed for an average of 168 days. Serum samples were collected on d 0 and 56 of the finishing period and at the end of the study. Control heifers had a greater (P<0.05) BW and G:F on d 35 than heifers in other treatments during the receiving period. No differences were observed among treatments for morbidity or serum Zn concentrations (P>0.50). Overall G:F tended (P=0.06) to be less for control heifers than for heifers in the 3 supplemental Zn treatments during the feeding period, but DMI or ADG did not differ among treatment groups. Experiment 2 the same for treatments were fed to 24 beef heifers (initial BW = 291.1 kg) for a 21 day period. Humoral immune response was determined by measuring specific antibody titers following s.c. injection of ovalbumin on d 0 and 14. Serum Zn concentration and specific ovalbumin IgG titers did not differ (P>0.10) among the 4 treatments on any sampling day. Results from these two studies showed no major differences among the sources of supplemental Zn for receiving period morbidity, ADG, DMI,and humoral immune response of beef heifers; however, lack of supplemental Zn during an extended finishing period tended to negatively affect G:F.
Nunnery, G.A., J.T. Vasconcelos, C. H. Parsons, G.B. Salyer, P.J. Defoor, F.R. Valdez, M.L. alyean. Effects of source of supplemental zinc on performance and humoral immunity in beef heifers. published online first May 25, 2007, 2007-0167v1. doi:10.2527
Effect of IV sodium salicylate on plasma cortisol in calves after castration
Pain associated with castration in cattle is an animal welfare concern in beef production. This study examined the effect of oral aspirin and intravenous (i.v.) sodium salicylate on acute plasma cortisol response following surgical castration. Twenty bulls, randomly assigned to the following groups, (i) uncastrated, untreated controls, (ii) castrated, untreated controls, (iii) 50 mg/kg sodium salicylate i.v. precastration and (iv) 50 mg/kg aspirin (acetylsalicylic acid) per os precastration, were blood sampled at 3, 10, 20, 30, 40, 50 min and 1, 1.5, 2, 4, 6, 8, 10 and 12 h postcastration. Samples were analyzed by competitive chemiluminescent immunoassay and fluorescence polarization immunoassay for cortisol and salicylate, respectively. Data were analyzed using noncompartmental analysis, a simple cosine model, ANOVA and t-tests. Intravenous salicylate Vd(ss) was 0.18 L/kg, ClB was 3.36 mL/min/kg and t1/2 was 0.63 h. Plasma salicylate concentrations above 25 μg/mL coincided with significant attenuation in peak cortisol concentrations (P = 0.029). Peak salicylate concentrations following oral aspirin administration was <10 μg/mL and failed to attenuate cortisol response. Once salicylate concentrations decreased below 5 μg/mL, cortisol response in the castrated groups was significantly higher than uncastrated controls (P = 0.018). These findings have implications for designing drug regimens to provide analgesia during routine animal husbandry procedures.
Coetzee, J. F., Gehring, R., Bettenhausen, A. C., Lubbers, B. V., Toerber, S. E., Thomson, D. U., KuKanich, B., Apley, M. D. Attenuation of acute plasma cortisol response in calves following intravenous sodium salicylate administration prior to castration. J. vet. Pharmacol. Therap. doi: 10.1111/j.1365-2885.2007.00869.x
Grader bias in cattle markets?
Live cattle are increasingly priced as an explicit function of U.S. Department of Agriculture yield and quality grades. Human graders visually inspect each slaughtered carcass and call grades in a matter of seconds as the carcass passes on a moving trolley. The authors examined whether there is systematic bias in grade calls using a sample of loads delivered to three different midwestern packing plants during 2000–2002. Overall, results indicate that indeed there is a bias, and that grading standards vary significantly across packing plants. Results also are consistent with a behavioral model where graders are more accurate when grading relatively low-quality carcasses.
Hueth, B. P. Marcoul, J. Lawrence.
Grader bias in cattle markets? Evidence from Iowa.
Amer Jour Ag Econ.
2007 (OnlineEarly Articles). Doi: 10.1111/j.1467.8276.2007.1026.x
Feed efficiency, growth and carcass merit
Feed intake and feed efficiency are economically important traits of beef cattle. This study determined the relationships of daily DMI, feed-to-gain ratio (F:G), residual feed intake (RFI), and partial efficiency of growth (efficiency of ADG, PEG) with growth and carcass merit of beef cattle. Residual feed intake was calculated from phenotypic regression (RFIp) or genetic regression (RFIg) of ADG and metabolic BW on DMI. An F1 half-sib pedigree file containing 28 sires, 321 dams, and 464 progeny produced from crosses between Alberta Hybrid cows and Angus, Charolais, or Alberta Hybrid bulls was used. Families averaged 20 progeny per sire (range = 3 to 56). Performance, ultrasound, and DMI data was available on all progeny, of which 381 had carcass data. Phenotypic and genetic parameters were obtained using SAS and ASREML, respectively. Differences in RFIp and RFIg, respectively, between the most and least efficient steers were 5.59 kg DM/d and 6.84 kg DM/d. Heritabilities for DMI, F:G, PEG, RFIp, and RFIg were 0.54 ± 0.15, 0.41 ± 0.15, 0.56 ± 0.16, 0.21 ± 0.12, and 0.42 ± 0.15, respectively. The genetic (r = 0.92) and phenotypic (r = 0.97) correlations between RFIp and RFIg indicated that the 2 indices are very similar. Both indices of RFI were favorably correlated phenotypically (P < 0.001) and genetically with DMI, F:G, and PEG. Residual feed intake was tendentiously genetically correlated with ADG (r = 0.46 ± 0.45) and metabolic BW (r = 0.27 ± 0.33), albeit with high SE. Genetically, RFIg was independent of ADG and BW but showed a phenotypic correlation with ADG (r = -0.21; P < 0.05). Daily DMI was correlated genetically (r = 0.28) and phenotypically (r = 0.30) with F:G. Both DMI and F:G were strongly correlated with ADG (r > 0.50), but only DMI had strong genetic (r = 0.87 ± 0.10) and phenotypic (r = 0.65) correlations with metabolic BW. Generally, the phenotypic and genetic correlations of RFI with carcass merit were not different from zero, except genetic correlations of RFI with ultrasound and carcass LM area and carcass lean yield and phenotypic correlations of RFI with backfat thickness (P < 0.01). Daily DMI had moderate to high phenotypic (P < 0.01) and genetic correlations with all the ultrasound and carcass traits. Depending on how RFI technology is applied, adjustment for body composition in addition to growth may be required to minimize the potential for correlated responses to selection in cattle.
Nkrumah, J.D., J.A. Basarab, Z. Wang, C. Li, M.A. Price, E.K. Okine, D. H. Crews, S.S. Moore. Genetic and phenotypic relationships of feed intake and different measures of feed efficiency with growth and carcass merit of beef cattle. J Anim Sci. Published online first on May 25, 2007. doe: 10.2527/jas.2006-767.
MGA impact on inflammatory response in Mannheimia challenged heifers
Previous research from our laboratory has indicated that melengestrol acetate (MGA) added to the diet during the first 35 d after arrival in the feedlot improves growth rates and tends to reduce chronic respiratory disease in heifers naturally challenged with bovine respiratory disease. The current study was conducted to provide further insight into the possible immunomodulatory effects of MGA. Crossbred heifers (n = 48; 232 ± 5.5 kg of BW) were used in a randomized complete block design to determine the effects of MGA on lung pathology and markers of inflammation after Mannheimia haemolytica challenge. On d 0, cattle were blocked by BW and randomly assigned, within block, to diets (54% concentrate) that provided 0 or 0.5 mg of MGA per heifer daily for the duration of the experiment. Inoculum containing from 1.3 x 109 to 1.7 x 109 cfu of M. haemolytica (20 mL) was instilled at the bifurcation of the trachea on d 14. Blood samples were collected, clinical observations were made, and rectal temperatures were recorded for each animal at 0, 12, 24, 48, 72, 96, 120, and 138 h after inoculation. Heifers fed MGA had greater circulating concentrations of eosinophils and postchallenge concentrations of segmented neutrophils and white blood cells (P < 0.01) than controls, as well as elevated plasma protein, serum haptoglobin, and fibrinogen after M. haemolytica challenge (P < 0.01). Heifers fed MGA had lower plasma glucose (P < 0.01), greater plasma urea N (P = 0.02), and elevated respiratory indices (P < 0.01) compared with controls. Necropsies performed on d 6 after inoculation suggested that M. haemolytica challenge was relatively mild, because lesions were confined to a small portion of the lungs. On a 0 to 100 scale, average lung lesion scores were 3 and 1 for MGA-fed and control groups, respectively (P < 0.06). Heifers fed MGA before mild M. haemolytica challenge were more susceptible to infection, as evidenced by a greater number of heifers fed MGA exhibiting pulmonary lesions 138 h after inoculation than controls (14 out of 23 vs. 6 out of 24 for MGA and controls, respectively; P < 0.02).
Corrigan, M.E., J.S. Drouillard, M.F. Spire, D.A. Mosier, J.E. Minton, J.J. Higgins, E.R. Loe, B. E. Depenbusch, and J.T. Fox. Effects of melengestrol acetate on the inflammatory response in heifers challenged with Mannheimia haemolytica. J. Anim Sci. 2007. 85: 1809-1815.
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