Objective To measure plasma cortisol responses in calves dehorned using a scoop after administration of local anaesthesia and/or cautery of the wounds. Design A physiological study with controls. Procedure There were six treatments: control handling with and without local anaesthesia, dehorning, dehorning after local anaesthesia, dehorning followed by wound cautery, and dehorning after local anaesthesia followed by wound cautery. Blood samples were taken before and after dehorning. Results Dehorning caused an increase in plasma cortisol concentrations, which decreased a little to plateau values and then declined to pretreatment values 3 to 4 h after dehorning. The peak was smaller after local anaesthesia was administered but when its effects wore off, cortisol concentrations increased and thereafter were similar to those in the dehorned animals. The combination of local anaesthesia and cautery resulted in a plasma cortisol response similar to those in control calves with or without local anaesthesia. Conclusions If plasma cortisol concentrations reflect the distress being experienced by the calves, then local anaesthesia reduces the acute distress for about 3 h after dehorning but not during the subsequent 3 to 4 h. Combining local anaesthetic and cautery prevented the significant increase in plasma cortisol following dehorning and may eliminate the acute distress caused by scoop dehorning. 相似文献
Nitrogen-fixing species can dramatically increase soil acidity and organic matter content, and potentially alter biogeochemical P dynamics. We compared ecosystem P cycling in adjacent stands of N2-fixing red alder (Alnus rubra Bong.) and non-fixing Douglas-fir (Pseudotsuga menziesii Franco) in order to determine whether P-cycling rates within stands were related to soil P forms as measured by sequential P fractionation. Above-ground annual P uptake was 61% greater in the red alder stand, although soil available P, as measured by Bray (NH4F–HCl) extraction, was only 10% of that found in the Douglas-fir stand. Total ecosystem P in the alder stand was only 69% of that found in the Douglas-fir stand, and could indicate a pre-establishment difference between stands. However, the percentage of total soil P released by Bray or NaOH extraction was also lower in the alder stand, which suggests that differences in total P alone did not control the patterns observed in P fractions. Concentrations of inorganic P sorbed to Fe and Al minerals and contained in Fe minerals and apatite were greater under Douglas-fir, while organic P was slightly greater under red alder. While fluxes of P in litterfall, uptake and resorption were 94, 60 and 292% higher in the alder stand, soil extractable fractions meant to represent available P were lower under alder. Static measures of available P do not appear to adequately reflect P supply, and the development of techniques to assess P turnover is needed to better understand cycling and plant availability of P. 相似文献
The response of a forest to nutrient and moisture stresses is reflected in nutritional, physiological, and structural changes that include efficiency of nutrient use, translocation and cycling of nutrients, transpiration, retention of foliage, below-ground and above-ground allocation of carbon, as well as the structural development of the forest stand and its growth characteristics. This article reviews the relationship of forest ecosystems to nutrient and moisture stresses and addresses the means by which productivity can be enhanced by altering nutrient and moisture regimes.
Considerable research has focused on optimizing productivity by minimizing nutrient and moisture stresses. Research involved in nutrient additions has led to the use of commercial fertilizers to improve forest productivity. The results suggest that many forests are deficient in N and P and, to a lesser extent, S, K, Mg and trace elements. The duration of response for most nutrient additions is, however, relatively brief and the efficiency of the tree in using fertilizer is relatively poor. Long-term correction of nutrient deficiencies is seldom achieved with chemical fertilizers. However, N added through symbiotic fixation or, on a more limited scale, through addition of municipal and industrial waste by-products, can provide an excellent long-term growth response.
It is seldom feasible to change the moisture regime of a forest ecosystem through irrigation. However, field trials involving irrigation have demonstrated that moisture stress can limit productivity. There are various ways of minimizing moisture stress without irrigation, including mulching, removing ground-cover vegetation, and changing the spatial characteristics of the forest cover.
Research trials show that forest ecosystems will respond to moisture and nutrient additions; however, these responses and interactions between nutrients and moisture are typically poorly understood, and many questions remain unanswered: Does fertilization increase moisture-use efficiency of a forest or simply improve the nutrition of the site? Does improving the moisture regime of a site improve productivity primarily by decreasing moisture stress or by increasing nutrient availability and the rate of nutrient uptake? Is there a synergism in growth response with the addition of both nutrients and moisture? The linkages between nutrients and moisture appear inseparable and confound experimentation in this field. Answers to these questions and issues need to be found for the future development of plantation forestry. 相似文献
Agroforestry Systems - Peach palm (Bactris gasipaes) was domesticated as a fruit crop by the first Amazonians in traditional Neotropical agroforestry systems, but research and development... 相似文献
The study compared response to prostaglandin F2α (PG), synchrony of ovulation and pregnancy per AI (P/AI) in a 5‐ vs a 7‐day Ovsynch + PRID protocol and investigated whether the initial GnRH affects P/AI in lactating dairy cows. Two hundred and seventy‐six cows (500 inseminations) were assigned to one of four timed‐AI (TAI) protocols: (i) PRID‐7G; 100 μg GnRH im, and a progesterone‐releasing intravaginal device (PRID) for 7 days. At PRID removal, PG (500 μg of cloprostenol) was given im. Cows received the second GnRH treatment at 60 h after PRID removal and TAI 12 h later. (ii) PRID‐5G; as PRID‐7G except the duration of PRID, treatment was 5 days and PG was given twice (12 h apart). (iii) PRID‐7NoG; as PRID‐7G except the initial GnRH, treatment was omitted. (iv) PRID‐5NoG; as PRID‐7NoG except the duration of PRID, treatment was 5 days. Response to treatments and pregnancy status at 32 and 60 days after TAI was determined by ultrasonography. The percentage of cows ovulating before TAI was greatest in PRID‐7G (17.1%), and the percentage of cows that did not have luteal regression was greatest in PRID‐5G (9.5%). The overall P/AI at 32 and 60 days did not differ among TAI protocols. However, during resynchronization, cows subjected to the 5‐day protocols had greater (p < 0.05) P/AI (45.3% vs 33.6%) than cows subjected to the 7‐day protocols. Pregnancy loss between 32 and 60 days tended (p = 0.10) to be greater in cows that did not receive initial GnRH (14.8%) compared to those that received GnRH (8.2%). In conclusion, the PRID‐5G protocol resulted in fewer cows responding to PG, but P/AI did not differ among TAI protocols. A 5‐day protocol resulted in more P/AI in resynchronized cows, and cows that did not receive initial GnRH tended to experience more pregnancy losses. 相似文献
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