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131.
X. M. Zhou P. Dutilleul A. F. MacKenzie C. A. Madramootoo D. L. Smith 《Journal of Agronomy and Crop Science》1997,178(2):65-71
A field experiment was conducted to evaluate the effect of long-term exogenous sucrose supply on aspects of corn plant physiology and development during the grain filling period. Concentrated sucrose solution was supplied to corn ( Zea mays L.) stems by an injection technique. This injection technique delivered pressurized solutions through syringe needles sealed to the stem with latex. The pressure was applied to the syringe plunger with ceramic construction bricks. Solutions containing sucrose at 0, 150, and 300 g L−1 were injected over a 32 day period encompassing the duration of the active grain filling period. The primary ears of plants injected with sucrose produced approximately 50% more kernels and 30% more grain weight than those injected with distilled water. The injected internode was also considerably heavier (56%) for plants receiving 300 g sucrose L−1 than plants receiving distilled water. For all measured variables, plants injected with distilled water were either not different from or had larger values than the non-injected controls. After one week sucrose injection caused photo-synthetic inhibition (as measured by chlorophyll fluorescence) in the leaf just above the ear and the ear leaf, and this was more severe for plants receiving 300 g sucrose L−1 than for those receiving 150 g sucrose L−1 . For sucrose injected plants, the increased size of the primary ear was concomitant with a large decrease in grain production by the secondary ear and an overall decrease in per plant grain production. These results suggest that the mechanisms for signalling between sinks (the primary and secondary ears) and the primary sink and the source (leaves) are different. 相似文献
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Two varieties of avocado leaves (Persea americana var Guatemalan and var Mexican) were administered to lactating goats. The Mexican variety was without effect. The Guatemalan variety in doses exceeding 20 g fresh leaf per kg bodyweight, produced damage to the mammary gland with decreased milk production. The lesions were characterised by oedema and reddening, with clots in the large ducts. Microscopically, there was widespread degeneration and necrosis of the secretory epithelium, the necrotic cells sloughing into the lumen. There was no significant cellular inflammatory response. Concentrations of antitrypsin in the milk, indicating changes in vascular permeability, increased rapidly 15 h after a single high dose, coinciding with palpable oedema. Concentrations of NAGase, indicating cell damage, increased after 24 h. Goats given multiple doses followed a similar pattern but the initial response was delayed. The toxic principle, and its mode of action in selectively damaging mammary secretory cells, remains to be determined. 相似文献
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Dipta DEY Tanzila Ismail EMA Partha BISWAS Sharmin AKTAR Shoeba ISLAM Urmi Rahman RINIK Mahmudul FIROZ Shahlaa Zernaz AHMED Salauddin AL AZAD Ahsab RAHMAN Sadia AFRIN Rezwan Ahmed MAHEDI Md. Nasir Uddin BADAL 《农业科学与工程前沿(英文版)》2021,8(4):603
138.
Objective To measure associations between body weight, growth rate, sex, time of shearing and post-weaning mortality of Merino sheep.
Design Uni- and multivariable survival analyses of sheep mortality during the first year after weaning, using records (n = 3657) from two field experiments conducted in Western Victoria from 1996 to 2003.
Results Overall mortality was 14.3% (range 4.5–26.8%) and mean maximum mortality rate was 29 deaths/1000 weaners/month. Increased mortality risk was associated with decreases in fleece-free body weight and mean weaner growth rate, particularly at low weights and growth rates. Weaners in the lightest weaning weight quintile had a hazard ratio of 3.5, compared with the middle quintile. The hazard ratio for a 2-kg decrease in weaning weight was 1.2 to 1.7 for weaners lighter than 22 kg. The hazard ratio for a reduction in mean weaner growth rate in the first 5 months after weaning of 0.25 kg/month was 1.1 to 6.8 if mean growth rate was less than 1 kg/month, but did not differ significantly from 1 at greater growth rates. The hazard ratio for wether weaners was approximately 1.5 compared with ewe weaners. The hazard ratio for weaners shorn between December and May, compared with unshorn weaners, was 1.2 to 3.5, with the greatest risk difference associated with shearing in March (45 deaths/1000 weaners/month).
Conclusion Improving the body weight and mean growth rate of weaner sheep is likely to reduce post-weaning mortality. Lightweight weaners in a flock should be managed separately from the main portion after weaning. In southern Australia, not shearing spring-born Merino weaners between December and May may assist in reducing overall post-weaning mortality. 相似文献
Design Uni- and multivariable survival analyses of sheep mortality during the first year after weaning, using records (n = 3657) from two field experiments conducted in Western Victoria from 1996 to 2003.
Results Overall mortality was 14.3% (range 4.5–26.8%) and mean maximum mortality rate was 29 deaths/1000 weaners/month. Increased mortality risk was associated with decreases in fleece-free body weight and mean weaner growth rate, particularly at low weights and growth rates. Weaners in the lightest weaning weight quintile had a hazard ratio of 3.5, compared with the middle quintile. The hazard ratio for a 2-kg decrease in weaning weight was 1.2 to 1.7 for weaners lighter than 22 kg. The hazard ratio for a reduction in mean weaner growth rate in the first 5 months after weaning of 0.25 kg/month was 1.1 to 6.8 if mean growth rate was less than 1 kg/month, but did not differ significantly from 1 at greater growth rates. The hazard ratio for wether weaners was approximately 1.5 compared with ewe weaners. The hazard ratio for weaners shorn between December and May, compared with unshorn weaners, was 1.2 to 3.5, with the greatest risk difference associated with shearing in March (45 deaths/1000 weaners/month).
Conclusion Improving the body weight and mean growth rate of weaner sheep is likely to reduce post-weaning mortality. Lightweight weaners in a flock should be managed separately from the main portion after weaning. In southern Australia, not shearing spring-born Merino weaners between December and May may assist in reducing overall post-weaning mortality. 相似文献
139.
EI Cortés-Gutiérrez F Crespo C Serres-Dalmau AL Gutiérrez de las Rozas MI Dávila-Rodríguez C López-Fernández J Gósalvez 《Reproduction in domestic animals》2009,44(5):823-828
Sperm DNA fragmentation (sDF) is an important parameter to assessing sperm quality. Information about sperm quality is not available for donkeys, especially in some breeds at risk of extinction. The objectives of this research were to test the four commercial variants of sperm chromatin dispersion test (SCD; sperm Halomax test), originally developed to assess sDF in boars, bulls, rams and stallions, in order to scrutinize their applicability in the study of sDF in a donkey breed at risk of extinction (Zamorano-Leonesa), for which there is no specific test available to analyze sperm at present. Only the SCD test, originally developed for stallions, produced stable and consistent results, and was deemed suitable to assess DNA fragmentation in sperm samples from donkeys. Image analysis was used to compare differences between the SCD methodology applied to stallion and donkey semen samples processed under the same experimental conditions. The extent of SCD in the SCD test was approximately 20% lower in donkey sperm than in stallion sperm. Yet, the ratio of chromatin sperm dispersion achieved in fragmented and unfragmented nuclei did not differ significantly between species. These data suggest that a similar protein depletion treatment can cause differences in protein removal in equivalent cells from different species and that sperm chromatin may be organized differently in stallions and donkeys. 相似文献
140.
Duncan S. MacKenzie Hae Young Moon Delbert M. Gatlin III Lisa R. Perez 《Fish physiology and biochemistry》1993,11(1-6):329-335
Juvenile red drum (Sciaenops ocellatus) were cultured at 25°C on a variety of diets and blood sampled over eight weeks to examine the relationship between growth and plasma thyroid hormone levels. Maximum growth rates were achieved on formulated experimental diets and a simulated natural shrimp diet. Associated with these maximal rates was a significant increase in triidothyronine (T3), but no consistent change in thyroxine (T4). Reduced rations of diets resulted in low growth rates associated with significantly lowered levels of T3 but not T4. To determine whether weight gain could be increased by application of exogeneous hormone, diets were supplemented with T3 or T4 at 2, 10, and 50 mg hormone/kg diet. Significantly elevated T3 was induced by supplementation with 10 and 50 mg T3/kg diet, although there were no indications of an anabolic effect of T3 incorporation, and 50 mg T3/kg diet was in fact associated with decreased weight gain. Incorporation of T4 into diets had no effect on growth or T3, and had effects on T4 which were small and inconsistent, indicating that T4 may not be effectively absorbed from the gut. No difference was found in response to hormone feeding between low (6 ppt) or high (35 ppt) water salinity. T3 levels thus appear to closely parallel growth in fish on unsupplemented diets, whereas T4 which were small and manipulation. Supplementation with T3 is not an effective means of stimulating growth in red drum fed optimum diets. Whereas thyroid hormones may function to regulate intermediary metabolism in red drum, elevated endogenous thyroid hormone levels appear adequate to supply tissue needs during juvenile growth in culture. 相似文献