Effect of blood metabolites, body condition and pasture management on milk yield and postpartum intervals in dual-purpose cattle farms in the tropics of the state of Veracruz, Mexico

Research was conducted on typical smallholder farms with dual-purpose cattle (DPC) (Bos indicus x B. taurus) in the coastal north-central area of Veracruz, Mexico. The study was divided into two phases. The aim of the first phase was to investigate the effect of blood metabolities, body condition and pasture management on milk yield and postpartum intervals, in order to investigate if the former are suitable indicators of the reproductive and nutritional status of DPC. One hundred and sixty-five calvings of crossbred cows were recorded from January 1992 to November 1994 on 12 small farms. Milk samples were collected twice a week for progesterone analysis. Blood samples and BCS were taken once a month. However, in Phase II emphasis was placed on the effect of pasture management upon reproductive and productive performance of DPC. Records of four farms were obtained from June 1995 to November 1996. Stocking rates were 0.40, 0.87, 0.35 and 1.5 cows/ha for farms A, B, C and D, respectively. Farms A and C used a slow rotation while B and D used a rapid rotation. In Phase I, the changes in BCS during the last month of pregnancy and first month postpartum did not correlate (p > 0.05) with milk yield or reproductive performance. Blood the metabolite profiles were not consistently related to productive or reproductive variables. The effect of farm and season was significant (p < 0.05) on most of the response variables and low productivity on overstocked farms lead to the conclusion that the low reproductive performance of DPC was linked to poor pasture management. During Phase II, farms A (FA) and D (FD) produce more milk than the others. Days to first service, days open, and calving interval were similar for farms B (FB) and C (FC), highest for Farm A, and lowest for Farm D. The forage availability mean was above the critical range of 6-8 kg of dry matter per 100 kg of liveweight (kg DM/100 kg LW) in all farms (range from 6.1 +/- 5.0 to 21.1 +/- 11.2 kg DM/100 kg LW). Farm D had the highest stocking rate (1.5 cows/ha), a rapid rotation (10 paddocks), a good forage availability (7.1 +/- 3.9 kg DM/100 kg LW) with a good quality for a tropical pasture (11.6 +/- 2.4% crude protein), and an economic energy supplementation. These results suggest this type of management could be more widely employed to improve the productivity of DPC on smallholder farms in the Mexican tropics.     

In vitro and in vivo hepatoprotective and antioxidant effects of Astragalus polysaccharides against carbon tetrachloride-induced hepatocyte damage in common carp (Cyprinus carpio)

The present study is aiming at evaluating the hepatoprotective and antioxidant effects of Astragalus polysaccharide (APS) on the carbon tetrachloride (CCl₄)-induced hepatocyte and liver injury in common carp in vitro and in vivo. In vitro, APS (200, 400 and 800 μg/ml) was added to the carp primary hepatocytes before (pre-treatment), after (post-treatment) and both before and after (pre- and post-treatment) the incubation of the hepatocytes with CCl₄ at 8 mM in the culture medium. APS at concentrations of 200, 400 and 800 μg/ml significantly improved cell viability and inhibited the elevation of glutamate pyruvate transaminase (GPT), glutamate oxalate transaminase (GOT), lactate dehydrogenase (LDH) and malondialdehyde (MDA) and significantly increased the reduced level of superoxide dismutase (SOD). In vivo administration of APS at the doses of 1.5 and 3 g/kg in the diet for 60 days prior to CCl₄ intoxication significantly reduced the elevated activities of GPT, GOT and LDH and increased the reduced levels of total protein and albumin in the serum; meanwhile, the reduced levels of SOD, glutathione and total antioxidant capacity (T-AOC) were markedly increased and the MDA formation was significantly inhibited in liver tissue. Overall results proved the hepatoprotective action of APS, which is likely related to its antioxidant activity. The results support the use of APS as a hepatoprotective and antioxidant agent in fish.     

Pan‐continental invasion of Pseudorasbora parva: towards a better understanding of freshwater fish invasions

In recent years, policy‐makers have sought the development of appropriate tools to prevent and manage introductions of invasive species. However, these tools are not well suited for introductions of non‐target species that are unknowingly released alongside intentionally‐introduced species. The most compelling example of such invasion is arguably the topmouth gudgeon Pseudorasbora parva, a small cyprinid species originating from East Asia. A combination of sociological, economical and biological factors has fuelled their rapid invasion since the 1960s; 32 countries (from Central Asia to North Africa) have been invaded in less than 50 years. Based on a combination of monitoring surveys (2535 populations sampled) and literature reviews, this paper aims to quantify and characterise important invasion parameters, such as pathways of introduction, time between introduction and detection, lag phase and plasticity of life history traits. Every decade, five new countries have reported P. parva introduction, mainly resulting from the movement of Chinese carps for fish farming. The mean detection period after first introduction was 4 years, a duration insufficient to prevent their pan‐continental invasion. High phenotypic plasticity in fitness related traits such as growth, early maturity, fecundity, reproductive behaviour and the ability to cope with novel pathogens has predisposed P. parva to being a strong invader. The Pseudorasbora parva invasion has provided quantitative data for the development of 1) early warning systems across different spatial scales; 2) rapid eradication programmes prior to natural spread in open systems and 3) sound risk assessments with emphasis on plasticity of life history traits.     

环磷酰胺诱导的尼罗罗非鱼体内外肝损伤模型的构建

以环磷酰胺(CTX)为诱导物，建立罗非鱼体内外急性肝损伤模型。体外，0、5、10、15、20和25 mmol·L^-1 CTX 分别作用于离体培养的罗非鱼精密肝切片（PCLS）6 h 后，测定切片培养上清中谷丙转氨酶（GPT）、谷草转氨酶（GOT）和乳酸脱氢酶（LDH）水平，同时收集肝切片，用噻唑蓝（MTT）法检测肝切片增殖活性，测定切片内总抗氧化能力（T-AOC）、丙二醛（MDA）、过氧化物歧化酶（SOD）和谷胱甘肽（GSH）水平。体内，采用胸腔注射法造模，每千克鱼体重分别注射0、10、25、75和100 mg环磷酰胺（下文以mg·kg^-1表示），每隔3 d给药1次，连续3次。末次给药后第4天取血，测定罗非鱼血清中GPT、 GOT 和LDH及肝组织匀浆中T-AOC 、MDA、SOD和GSH水平。结果显示： 20～25 mmol·L^-1 CTX作用体外培养精密肝切片6 h及75～100 mg·kg^-1 CTX胸腔注射罗非鱼后，均可以导致GPT、GOT和 LDH 活力显著升高；T-AOC、SOD活力及GSH含量显著下降，MDA含量显著提高。同时，20 和25 mmol·L^-1 CTX能导致肝切片增殖活性显著下降，分别为空白对照组的67.29%和55.41%，且有剂量依赖性。结果表明：CTX可引起罗非鱼肝损伤；分别采用20 mmol·L^-1 CTX 作用体外培养PCLS 6 h或者采用75～100 mg·kg^-1 CTX胸腔注射罗非鱼，每隔3 d给药1次，连续3次，均可以构建体内外急性肝损伤模型。     

Pikeperch (Sander lucioperca) spermatozoa motility and volume regulation under different osmotic and ionic conditions

Fish Physiology and Biochemistry - Pikeperch (Sander lucioperca) is a highly profitable commercial species whose economic value has greatly increased in the last decade. As in other species, the...