To determine plasma cortisol and white blood cell response to castration, Angus (n = 12, 21.4 mo of age), Hereford (n = 6, 21.2 mo of age), and Brahman (n = 24, 20.3 mo of age) bulls nearing maturity were either left intact as uncastrated controls (CON), surgically castrated (SUR) after lidocaine, or castrated by latex rubber banding (BAN). Before and through 35 d after castration (castration = d 0), animals were weighed and blood samples were collected for analysis of cortisol and total white blood cell (WBC) count at 2-, 3-, or 7-d intervals. There was a treatment x breed interaction for ADG from d 0 to 7 (P < .05). From d 0 to 14, 0 to 21, 0 to 28, and 0 to 35, ADG tended to be lower for SUR and BAN animals than for CON animals (castrated vs CON, P < or = .13). No significant differences in ADG were observed between SUR and BAN animals during these times. On d 0, from just before treatment to just after treatment, plasma cortisol concentration increased 3.2 ng/mL for SUR and .1 ng/mL for BAN (SEM = +/- .5 ng/mL; SUR vs BAN, P < .03). From d 0 pretreatment to d 2 after treatment, plasma cortisol concentration increased 1.5 ng/mL for castrated (SUR = 2.0 and BAN = 1.1 ng/mL) and decreased 1.6 ng/mL for CON (SEM = +/- .7 ng/mL; P < .04). Plasma cortisol concentration was negatively correlated (P < .001) with BW (r = -.17) and BW change (r = -.19).(ABSTRACT TRUNCATED AT 250 WORDS)
Pregnancy rate, calf survival rate to weaning and calf age at weaning of several types of crossbred cows (2/3 or more Brahman) were compared to those of straightbred Brahman and Angus cows over a 12-yr period at Subtropical Agricultural Research Station near Brooksville, FL. The purpose of this study was to determine the relative importance of additive vs nonadditive genetic effects on reproductive and calf survival traits in a population of cattle whose foundation was selected on the basis of superior reproductive performance under harsh environmental conditions. Best linear unbiased estimates (BLUE) of direct additive effect (measured as the deviation of Brahman additive breed effect from Angus) for pregnancy rate and calf age, measured as traits of the dam, were 6 +/- 3% and -7.2 +/- 2.1 d, respectively. Thus, Bos taurus germ plasm did not increase pregnancy rate but resulted in an earlier calving date. The BLUE of nonadditive (intralocus) direct genetic effects measured as deviations from intralocus group genetic effects in the parental breeds on pregnancy rate and calf age at weaning were 25 +/- 4% and -6.4 +/- 2.5 d. Nonadditive effects on pregnancy rate were the primary cause of the superior reproductive rates observed in Brahman crossbred cows. Calf survival was considered to be a trait of the calf, and BLUE of direct additive, direct nonadditive, maternal additive and maternal nonadditive genetic effects was obtained. Only maternal nonadditive genetic effects were found to have a significant effect on survival rate (9 +/- 4%).
Herbicides applied postemergence to crops planted in rows must reach the target weed species to be effective. In numerous cases, the targeted species may be covered by leaves of a crop canopy. Our objective was to develop an apparatus that could be used effectively to apply directed herbicides postemergence to under‐canopy areas of crops planted in narrow rows (≤ 20 in.) so that the herbicide would reach the target species. We designed and constructed a sprayer that will attach to a 40‐ to 100‐hp row‐crop tractor having a PTO and standard Category (Cat.) II three‐point hitch attachment. This unit delivers herbicide sprays beneath the canopy of crops so that the maximum amount of herbicide spray reaches the target species. Each nozzle that is directed to cover the space in a single between‐row area is mounted on a wheel‐supported frame so that the height of application is constant regardless of terrain. Use of this sprayer to direct herbicide sprays underneath the canopy reduces the effect of wind that causes drift in over‐the‐top applications. Thus, use of this sprayer ensures that the maximum amount of spray solution of any herbicide applied postemergence will contact the target weed species that may be partially overshadowed by leaves of the crop, and will be confined to the intended area of application. Problem or Need and Approach Herbicides applied to crops must reach the target species to be effective. The crop canopy often intercepts a significant portion of a herbicide when applied over the top, especially in narrow‐row crop production systems (≤20 in.). A spray apparatus was built to provide a method for applying herbicide sprays underneath the canopy of crops in narrow rows so that deposition of herbicide on under‐canopy weeds would be maximum. Literature Summary Research results indicate that herbicides can effectively control weeds in crops grown in narrow rows. However, when applied above the crop canopy, some herbicides can cause temporary injury to the crop, and may not effectively reach the target weed species underneath the crop canopy. Thus, over‐the‐top application of herbicides may not be the most effective method for weed control in crops with partially developed canopies. Description of Sprayer A spray apparatus was designed and built for applying herbicide sprays under the canopy of crops in narrow rows. The sprayer uses a tool bar as a main frame to which nozzle support assemblies are attached by a hinge mechanism to allow the assemblies to follow the terrain in the sprayed area. The nozzle support assemblies are supported by wheels located at the end of each assembly, and tension springs are used to keep the units from bouncing excessively as the sprayer is pulled through the field. Nozzles are directed to the areas between individual rows. The sprayer is attached to a tractor with a three‐point hitch, and uses the tractor PTO to power a pump to pressurize the system. Applied Questions What is the general configuration of the sprayer? A rear view of the entire sprayer is shown in Fig. . T...
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