Stress commonly associated with weaning, marketing, and shipment of feeder cattle can temporarily compromise immune function, thereby reducing the effective response to vaccination intended to control bovine respiratory disease (BRD). Two vaccination timing treatments were used to evaluate the effect of timing of a multivalent modified live virus (MLV) BRD vaccine on health, performance, and infectious bovine rhinotracheitis (IBR) antibody titers of newly received stocker cattle. Crossbred bull and steer calves (n = 528) were weighed (197 ± 2.4 kg) and randomly assigned to MLV vaccination treatment: 1) MLV vaccination upon arrival (AMLV), or 2) delayed (14 d) MLV vaccination (DMLV). All cattle were processed similarly according to routine procedures, with the exception of the initial MLV vaccination timing. Subsequently, BW were recorded on d 14, 28, and 42. Blood samples were collected on d 0, 14, 28, and 42 to determine serum IBR
Lambs exposed to a heat-stressed environment (33 degrees C, 50% relative humidity) were used in three experiments to determine whether ergovaline (EV) is the primary toxin involved in fescue toxicosis. The first study evaluated the effects of feeding diets containing increasing levels of endophyte-infected tall fescue seed (E+) and decreasing levels of endophyte-free tall fescue seed (E-). The second and third study evaluated the response to a diet that contained synthetic EV added to an E- diet and the response to a diet containing endophyte-infected ryegrass seed (R+) with an elevated concentration of EV. In Exp. 1, lambs were fed diets of: 1) 10% E- and 0% E+, 2) 5% E- and 5% E+, or 3) 0% E- and 10% E+. Increasing the percentage of E+ in the diet resulted in a linear decrease (P < 0.01) in feed intake (as-fed basis), skin temperature, thermocirculation index (TCI), and serum prolactin. Body weight gain also decreased (P < 0.06). Respiratory rate and core body temperature were not affected by the 5 or 10% E+ diets. In Exp. 2, lambs were fed diets that contained: 1) 10% E-, 2) 10% E- with synthetic EV added at a level equivalent to the 10% E+ diet, or 3) 10% E+. Feed intake (as-fed basis), body weight gain, and skin temperature did not differ for lambs fed the E- and EV diets. The EV diet elicited a decrease (P < 0.05) in TCI and prolactin compared with the E- diet. The TCI for lambs fed EV did not differ (P > 0.10) from the E+ lambs; however, serum prolactin was lower (P < 0.05) for lambs on the E+ diet than for those fed EV. Core body temperature was not affected (P > 0.10) by feeding EV or E+ fescue seed in Exp. 2. In Exp. 3, lambs were fed diets that contained: 1) 10% E-, 2) 3.24% R+ and 6.76% E-, which added an equivalent amount of EV to E+ diets but reduced concentrations of other ergot alkaloids, or 3) 10% E+. Lambs fed the E+ diet and maintained at 33 degrees C had lowered feed intake (as-fed basis), skin temperature, and TCI compared with lambs fed the E- or R+ diets (P < 0.05). Lambs fed the E+ diet had increased rectal temperatures and lowered serum prolactin compared with lambs on the R+ diet (P < 0.05). Lambs on the R+ diet had a greater rectal temperature and lower serum prolactin than lambs on the E- diet (P < 0.05). These results suggest that EV is a fescue toxin; however, other alkaloids might work synergistically with EV, causing the full expression of fescue toxicosis.
Stress, commonly associated with weaning, marketing, and shipment of feeder cattle, can compromise immune function, and vaccine administration during immunosuppression may reduce vaccine efficacy and calf growth. Four treatments were compared in a 2 x 2 factorial arrangement to evaluate the effect of on-arrival (d 0) vs. delayed (d 14) administration of clostridial (CLOS) and respiratory (RESP) vaccines on health, performance, bovine viral diarrhea virus (BVDV) antibody titers, and physiological immune measurements of high-risk, newly received calves. Crossbred bull and steer calves (n = 263) were weighed (239 +/- 1.2 kg), stratified by sex, and randomly assigned to vaccination treatment: 1) arrival CLOS, arrival RESP (ACAR); 2) arrival CLOS, delayed RESP (ACDR); 3) delayed CLOS, arrival RESP (DCAR); and 4) delayed CLOS, delayed RESP (DCDR). Body weight and blood samples were collected on d 0, 14, 28, 42, and 56. Average daily gain did not differ (P > or = 0.34), averaging 0.98, 0.93, 0.95, and 0.91 kg/d for ACAR, ACDR, DCAR, and DCDR, respectively, for the entire 56-d trial. Vaccination timing did not affect morbidity (P > or = 0.23); however, there tended to be a CLOS timing effect (P = 0.07) and RESP timing effect (P = 0.09) on days to initial bovine respiratory disease (BRD) treatment. Average days to initial BRD treatment were less for ACAR (6 +/- 0.8 d) compared with DCDR (8 +/- 0.8 d; P = 0.01). Greater white blood cell counts were observed for DCDR than ACDR (P = 0.01), with ACAR and DCAR being intermediate. Serum cortisol concentrations were greater on d 0 than d 14 (P < 0.01) or d 28 (P = 0.01) but no treatment x day interaction (P = 0.21) was observed. Timing of RESP administration affected (P = 0.001) serum BVDV type I titers, with greater (P < 0.01) levels in calves receiving RESP vaccine on arrival. Delaying CLOS or RESP vaccination did not affect BW gain or morbidity in high risk, newly received stocker calves. Calves administered RESP vaccine on d 0 developed antibody titers to BVDV type I earlier than delayed RESP treatments. Total white blood cell count was greatest when RESP and CLOS vaccination were delayed (DCDR).
Grazing forages on small-grain fields can be a profitable "second crop" for grain producers and an opportunity for cow-calf producers to retain ownership of weaned calves. The increasing costs of conventional tillage and movement of soil nutrients into surface water creates a need for more sustainable production practices to be incorporated by producers into wheat pasture production systems. Research at the Livestock and Forestry Research Station near Batesville, AR, and the Southwest Research and Extension Center near Hope, AR, has been conducted over a 9-yr span to characterize the impacts of pasture systems on forage production, animal performance, soil quality, water runoff, and the economics associated with the stocker cattle enterprises. Gains of growing cattle grazing nontoxic endophyte-infected tall fescue and small-grain forages can be increased by 80 and 150%, respectively, compared with grazing Bermuda grass or toxic endophyte-infected tall fescue. Producers grazing spring-calving cowherds can use these improved forages to accelerate stocker performance when retaining calves in the fall and improve net returns by 99% with winter annual or nontoxic tall fescue production systems compared with Bermuda grass or toxic tall fescue. Rainfall simulation of small grain pastures indicates that runoff volume and nutrient load does not differ between conventionally tilled fields and no-till fields in the spring before tillage when soil surface cover is similar. In the fall after tillage, however, conventionally tilled fields had 4 times greater runoff; hence, there was 1.9 times greater N runoff and 3.2 times greater P runoff in conventionally tilled fields compared with no-till. Total natural rainfall runoff from conventionally tilled wheat fields were 2 times greater than from no-till fields with 25 mm rainfall events yet were 4 times greater with 62-mm rainfall events. Soil analysis shows that soil aggregate content was greater in no-till compared with conventional till, indicating greater soil porosity, improved water infiltration rate, and reduced erositivity of soil. Carbon concentration in no-till soils was 50% greater than conventional tillage after 9 yr. These experiments show that production systems can be designed that maintain livestock production, increase soil quality, reduce nutrient discharge, and promote improved economic returns.
Beef bull calves (n = 62) were assigned randomly, within sire breed, to 1 of 4 treatments at birth. Treatments were 1) surgical castration near birth, 2) surgical castration near birth with oral administration of meloxicam (1 mg/kg BW), 3) surgical castration at weaning (WNG), or 4) surgical castration at weaning with oral administration of meloxicam (1 mg/kg BW; WMX). A subset of calves (n = 7/treatment group) were selected randomly near birth for blood collection, behavioral analyses, and rectal temperature (RT) records for a 7-d postcastration period on d 0 (birth), 1, 3, and 7, and on d 214 (weaning), 214 + 6 h, 215, 217, 221, and 228. Calf standing and lying activity were monitored from the same subsets by recording x- and y-axis positions of an accelerometer attached to the right metatarsus for 7 d postcastration. Calf BW was recorded throughout the entire production cycle, and carcass data were collected at slaughter. For statistical analyses, bulls left intact at birth were considered a positive control (BUL) for observations that occurred before their treatment application at weaning; likewise, bulls castrated at birth were considered a negative control (STR) during postweaning observations. No difference (P > 0.88) occurred in ADG between treatments throughout the preweaning period (d 0 to 214); however, 56-d postweaning ADG was greatest ( P= 0.02) in STR, intermediate in WMX, and least in WNG. At weaning, haptoglobin (Hp) was greater (P ≤ 0.005) for WNG and WMX compared to STR on d 214+6 h, 215, and 217, and Hp was greater (P = 0.05) in WNG compared to WMX on d 217. Neutrophils increased (P < 0.001) and red blood cells decreased (P ≤ 0.03) for WNG and WMX on d 214+6 h and 217, respectively. Postweaning behavior observations indicated that STR calves spent the least proportion of time standing (P = 0.002) when compared to WNG and WMX. Furthermore, WMX calves exhibited a greater proportion of time spent standing (P = 0.03) compared to WNG. Grazing and finishing phase ADG and carcass measurements did not differ (P ≥ 0.24) across treatments. In this study, surgical castration at weaning, but not near birth, altered the acute phase response, behavior, and growth performance. Oral meloxicam reduced serum Hp and improved ADG briefly when administered to calves castrated at weaning. Oral administration of meloxicam may be efficacious for mitigating some of the stress and inflammation associated with castration of weaning-age bull calves.
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