Beef Research News
Brought to you by Kansas State University
College of Veterinary Medicine - Farm Animal Section
June 2007
Contents:
Supplemental zinc source effect on immunity & performance
Sodium salicylate and plasma cortisol in calves after castration
Grader bias in cattle markets?
Feed efficiency, growth and carcass merit
MGA and inflammatory response in Mannheimia challenged heifers
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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