湖南省麦迪卡药石农业应用效果综述

湖南省麦迪卡药石(MEDCAL STONE)资源丰富,质量优良,具有富硅、富钾、富微量元素和离子轻稀土的特点,具有很强的吸附性能,可溶出多种有益矿物质,增加水中氧的含量,调节水的pH值,生物活性强,对防治疾病具有重要作用。经过近20 a的研究,农业上应用在作物施肥、药膳食疗等方面,均有极好的社会、经济效益。同时,产地水土、森林、人文资源特好,生态景观优美,不但是天然的无公害农业基地,也是发展休闲农业、旅游农业的"风水宝地"。     

Ontogenetic movements of juvenile blacktip reef sharks: evidence of dispersal and connectivity between coastal habitats and coral reefs

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日光温室内反光膜补光的实践与理论探析

试验结果表明 ,温室后墙悬挂反光膜进行补光后 ,对温室内测定点处最大光照度值无影响 ,但平均提高测定点处水平光照度值 15 4 8% ;温室内凌晨时气温、地温、墙温和被反光膜遮掩处墙温分别比对照温室低 1 1℃、1 5℃、0 9℃和 1 8℃ ,但正午时分别比对照温室高 1 6℃、1 4℃、0 3℃和低 11 4℃。温室经济产量增加 7 4 % ,当期经济效益增加 2 1元 /m2 。     

不同栽培模式及施氮量对半旱地冬小麦氮素累积及分配的影响

【目的】研究不同栽培模式和施氮量对半旱地栽培条件下冬小麦-夏玉米轮作体系中冬小麦地上部氮素累积、分配及利用效率的影响。【方法】在陕西关中地区进行了田间试验,以常规栽培为对照,比较了补灌、覆草和垄沟等栽培模式及0,120,240 kg/hm2施氮水平,对冬小麦连续2年(2004和2005年)不同生长期各部位氮素累积量的影响。【结果】在补灌模式下,2004和2005年成熟期冬小麦叶片和茎秆的氮素累积量较其他模式低,氮素分配率也较低,而籽粒的氮素分配率较高;施用氮肥显著增加了各生长时期冬小麦叶片、茎秆、颖壳和穗轴以及籽粒的氮素累积量,当氮肥施用量由120增加到240 kg/hm2时,除籽粒外,成熟期冬小麦叶片、茎秆、颖壳和穗轴的氮素残留量均随之明显增加。与不同栽培模式相比,施用氮肥对冬小麦不同器官中氮素分配的影响较小。随着氮肥施用量的增加,氮肥利用效率、氮肥农学效率和氮肥生理效率均呈降低趋势。在不同栽培模式中,连续2年补灌栽培模式下冬小麦的氮肥利用效率、氮肥农学效率以及氮肥生理效率均较高,而其他栽培模式下这3个指标年际间的变化较大。【结论】施用氮肥可显著增加冬小麦各生长时期不同器官的氮素累积量,但对氮素在不同器官中分配比例的影响较小;与施用氮肥相比,不同栽培模式对冬小麦氮素的累积、分布无明显影响;冬季补灌有利于提高冬小麦的氮素效率。     

Body condition at parturition and postpartum weight changes do not influence the incidence of short-lived corpora lutea in postpartum beef cows

Seventy-seven multiparous beef cows (Hereford and Angus x Hereford) with thin to moderate BCS at calving were used to evaluate the effects of body condition at parturition and BW change after calving on duration and occurence of luteal activity before and after first estrus. Blood samples were collected twice weekly after parturition to determine the occurrence of the first postpartum luteal activity (LA, progesterone > or = 0.5 ng/mL). Weight changes and BCS were determined at 2-wk intervals. Cows were exposed to bulls and observed twice daily for behavioral estrus. Luteal activity was classified as normal if plasma concentrations of progesterone were > or = 0.5 ng/mL for at least 11 d, or short if concentrations of progesterone were > or = 0.5 ng/mL for 10 d or less. The interval from parturition to first normal LA was shorter (P < 0.001) for moderate condition (BCS > or = 4.5) than for thin (BCS < or = 4) cows (58.3 +/- 3.2 vs. 93.3 +/- 5.1 d, respectively). Interval to first estrus also was shorter (P < 0.001) for moderate than for thin cows (53.3 +/- 3.7 vs. 89.3 +/- 5.6 d, respectively). Before the first normal LA, 78% of cows had an increase in progesterone for < 11 d. Postpartum weight change and BCS at calving did not influence the incidence of estrus associated with first normal LA. After the first estrus, 72% of cows had normal LA, 16% had a short luteal phase, and 12% lacked LA. Postpartum weight change and BCS did not influence the length of LA associated with the first estrus. Cows with normal LA had increased (P < 0.05) maximal concentrations of progesterone compared with cows that had a short luteal phase. When a transient increase in progesterone occurred before first behavioral estrus, 81% of cows had normal luteal function after estrus. We conclude that when beef cows are in thin to moderate body condition at calving, postpartum BW change and BCS at calving do not influence the duration of luteal activity before or after the first postpartum estrus.     

Effects of supplementation on intake, digestion, and performance of beef cattle consuming fertilized, stockpiled bermudagrass forage

Experiments were conducted to determine the effects of increasing supplement protein concentration on performance and forage intake of beef cows and forage utilization of steers consuming stockpiled bermudagrass forage. Bermudagrass pastures were fertilized with 56 kg of N/ha in late August. Grazing was initiated during early November and continued through the end of January each year. Treatments for the cow performance trials were: no supplement or daily equivalents of 0.2, 0.4, and 0.6 g of supplemental protein per kilogram of BW. Supplements were formulated to be isocaloric, fed at the equivalent of 0.91 kg/d, and prorated for 4 d/wk feeding. Varying the concentration of soybean hulls and soybean meal in the supplements created incremental increases in protein. During yr 1, supplemented cows lost less weight and condition compared to unsupplemented animals (P < 0.05). During yr 2, supplemented cows gained more weight (P = 0.06) and lost less condition (P < 0.05) compared to unsupplemented cows. Increasing supplement protein concentration had no affect on cumulative cow weight change or cumulative body condition score change. Forage intake tended to increase (P = 0.13, yr 1 and P = 0.07, yr 2) in supplemented cows. Supplement protein concentration did not alter forage intake. In a digestion trial, four crossbred steers were used in a Latin square design to determine the effects of supplement protein concentration on intake and digestibility of hay harvested from stockpiled bermudagrass pasture. Treatments were no supplement; or 0.23, 0.46, and 0.69 g of supplemental protein per kilogram of BW. Forage intake increased (P < 0.05) 16% and OM intake increased (P < 0.01) 30% in supplemented compared to unsupplemented steers. Diet OM digestibility increased (P = 0.08) 14.5% and total digestible OM intake increased (P < 0.05) 49% in supplemented compared to unsupplemented steers. Supplement protein concentration did not alter forage intake, total digestible OM intake, or apparent digestibility of OM or NDF. During the initial 30 d after first killing frost, beef cows did not respond to supplementation. However, later in the winter, supplementation improved utilization of stockpiled bermudagrass forage.     

Effects of Body Condition and Protein Supplementation on LH Secretion and Luteal Function in Sheep

In ruminants, nutrition is one of the exogenous inputs affecting reproductive function at different levels of the hypothalamic-hypophyseal-gonadal axis. However, the exact mechanisms or even the identification of the signalling metabolic compounds by which nutrition affects reproductive function still need further clarification. The role of static body condition (BC) and its interaction with a short-term protein supplementation (PL), on secretion of metabolic hormones [growth hormone (GH), insulin and insulin-like growth factor-1 (IGF-1)], as well as on secretion of LH and progesterone (P4) was evaluated in sheep. Twenty-four Rambouillet ewes divided into two groups, with lower (LBC) and higher body condition (HBC), were randomly assigned within BC to one of two PL levels: low (LPL, 24% of crude protein; 14 g/animal/day), and high (HPL, 44% of crude protein; 30 g/animal/day). The secretion of GH, insulin, IGF-1 and LH was evaluated on day 10 of the oestrous cycle; appearance and timing of oestrous behaviour were previously detected using rams. Progesterone secretion was evaluated on day 13 of the same cycle. No differences were found (p > 0.05) between PL groups on serum GH concentrations during the sampling period (overall mean of 4.0 +/- 0.3 ng/ml), but a trend for lower values in HBC sheep was found (3.6 +/- 0.4 vs 4.4 +/- 0.4 ng/ml, p = 0.06). A BC effect was observed (p < 0.05) on serum IGF-1 level, with higher values in HBC sheep (p < 0.05). Neither BC nor PL affected (p > 0.05) secretion of LH and the number of corpora lutea, nor serum P4 and insulin concentrations. Results indicate a predominance of the static component of nutrition on sheep metabolic hormone responses, GH and IGF-1, with no effect of short-term PL on secretion of pituitary and ovarian hormones as well as luteal number and activity.