短花针茅草原五个载畜率水平绵羊活重变化规律

在内蒙古高原短花针茅荒漠草原采用5个不同载畜率水平进行的绵羊放牧试验结果表明,绵羊活重均以10月份为最大,中等载畜率有利于绵羊生产;随着载畜率增大,单位面积的绵羊增重逐渐增加,单个绵羊的增重逐渐减少,两者的交点为绵羊生产的适宜载畜率,即每半年 2.2只羊/hm2.     

内蒙古典型草原草畜系统适宜放牧率的研究Ⅰ.以绵羊增重及经济效益为管理目标

(1)绵羊个体增重与放牧率呈线性负相关,个体最大增重临界放牧率,因季节不同而变化,随着个体增重与放牧率回归系数b绝对值的增大而降低,以始、终放牧期间所得临界放牧率最小,(2.04羊/hm²)。(2)公顷增重与放牧率的关系符合二次曲线,在达到公顷最大增重以前,随着放牧率的增大而增大,之后则随着放牧率的增大而下降,平均543羊/hm²。(3)公顷最大增重并不一定获取公顷最大利润,主要视买卖价格及其差值而定。(4)以冷蒿小禾草为主的退化草原,宜以个体最大增重的适宜放牧率作为管理标准,以使该类草原在利用中得以恢复。     

Effects of stocking density and group size on the condition of the skin and feathers of pheasant chicks

Twenty-two flocks of pheasants were reared from day-old to approximately six weeks of age without the use of beak trimming or other measures against feather pecking. The pheasants were housed in aviaries in groups of 80 or 240 chicks at stocking densities of 0.7, 1.3 or 4.0 birds per m2. The quality of the pheasants' plumage was poorer at the highest stocking density than at the two lower densities. Higher stocking densities resulted in higher proportions of birds with injuries to their skin (7.2 per cent, 13 per cent and 34 per cent). The group size had no significant effect on the quality of the birds' plumage, but at the largest group size there were significantly more beak-inflicted skin injuries (21 per cent v 12 per cent). In the period between 35 and 42 days of age, the quality of the birds' plumage decreased significantly.     

Vegetation Responses to Fixed Stocking Densities in Highly Variable Montane Pastures in the Chinese Altay

Variability in aboveground herbaceous biomass and its quality were studied in response to three different stocking densities during a 2-yr grazing experiment with sheep on a montane summer pasture in the Chinese Altay. We determined herbaceous cover and aboveground biomass in 16 paddocks of 0.25 ha each. Vegetation cover showed high spatial variation, prompting us to implement a randomized block design. Forage intake of one male sheep per paddock was quantified four times per grazing season by collection of total feces and estimation of diet digestibility. Sheep weight was recorded every 3 wk. Aboveground herbaceous dry mass (DM) was characterized by pronounced annual variation. Biomass quality declined with progressing season and increasing sheep density. Daily organic matter intake per sheep ranged from 0.7 to 1.4 kg, which was paralleled by a biomass removal of 710 ? 1 560 kg DM/ha at densities of 8 ? 24 sheep/ha. At 8 sheep/ha, animals gained weight throughout each grazing period, whereas weight losses of 40 ? 100 g/d occurred at higher densities. These results challenge the presently followed concept of a fixed stocking density for summer pastures in Altay Prefecture, Xinjian, China. Such practice may result in low herbage allowances and thus deficient sheep nutrition in one year, as well as underutilization of forage resources in another. Flexible adjustment of stocking densities is also advisable for montane pastures where spatiotemporal variability, although less pronounced than in desert steppes of the Altay foothills, is nonetheless highly relevant.     

Sheep performance under intensive continuous grazing of native grasslands of <Emphasis Type="Italic">Paspalum notatum</Emphasis> and <Emphasis Type="Italic">Axonopus compressus</Emphasis> in the subtropical region of the Highlands of Central Mexico

Liveweight gain was evaluated in tropical Dorper X Pelibuey lambs under intensive continuous grazing of native grasslands dominated by Paspalum notatum (PN) or Axonopus compressus (AC) in the subtropics of Central Mexico. Two trials were undertaken. Trial 1 lasted 12 weeks with 10 lambs (initial weight 18 +/- 2.57 kg, 3 months old) per treatment in 2002, and Trial 2 for 13 weeks with 8 lambs (initial weight 24.0 +/- 2.0 kg, 4 months old) per treatment. Lambs were weighed once per week, and liveweight change was estimated by linear regression over day of the experiment, using individual regression coefficients as unbiased estimates of daily liveweight change; analysed in a random block design. Lambs on Trial 1 gained 0.061 kg/lamb/day on PN and 0.047 kg/lamb/day on AC (P > 0.05) at an overall mean stocking rate of 25 lambs/ha. In Trial 2, liveweight gain was significantly larger in PN (0.060 kg/lamb/day) than on AC (0.043 kg/lamb/day) (P < 0.05), at a mean stocking rate of 21.5 lambs/ha. It is concluded that intensive continuous grazing of native grasslands in the subtropics of the highlands of Central Mexico enables moderate liveweight gains for weaned lambs during the rainy season; with better results in grasslands dominated by Paspalum notatum.     

Stocking rate and the productivity of Rhodes grass pastures on the Lilongwe plain,Malawi

An experiment was undertaken over three wet (summer) seasons to investigate the effects of different set stocking rates on animal performance from fertilised Rhodes grass pastures. The three set stocking rates were 2.5, 5 and 7.5 livestock-units/ha (1 livestock unit=342 kg liveweight). Pasture productivity was related to stocking intensity. Animal gain per hectare was directly related to stocking rate. Gain per animal, gain per livestock unit and number of grazing days were all inversely proportional to stocking rate. Animals on the low stocking rate were carried through almost to the end of the dry (winter) season with only small changes in liveweight. The practical significance of the results is discussed.     

Cyromazine pour-on for the prevention of cutaneous myiasis of sheep

The results of trials on eight farms to assess the efficacy of two pour-on formulations containing cyromazine for the prevention of cutaneous myiasis of sheep are presented; data from trials on sheep with larval implants and on sheep kept in cages with adult flies are also reported. The incidence of cutaneous myiasis was reduced by between 87 per cent and 100 per cent for eight weeks when a formulation containing 6 per cent w/v cyromazine was used at an application rate of 60 to 85 mg of active ingredient/kg bodyweight. When a formulation containing 10 per cent w/v was used at an application rate of 50 to 100 mg/kg, the incidence of the condition was reduced by between 90 per cent and 100 per cent for eight weeks. Studies of sheep with larval implants, using the formulation containing 10 per cent w/v cyromazine at 50, 100 and 150 mg/kg bodyweight gave variable results with some animals at each dose rate having lost protection by the seventh week. When sheep were treated with the formulation containing 10 per cent w/v cyromazine at 50 or 100 mg/kg and exposed to adult flies in fly-proof cages they were completely protected for nine and eight weeks, respectively.     

Influence of stocking density on the performance, carcass characteristics and selected welfare indicators of broiler chickens

AIM: To compare the effects of four stocking densities (5, 10, 15 or 20 birds per m2) on the performance, carcass characteristics and selected welfare indicators of broiler chickens. METHODS: A total of 756 day-old male broiler chicks were assigned as six replicates of 13, 25, 38 and 50 birds per pen, to stocking densities of 2,000, 1,000, 667 and 500 cm2 floor space per bird, respectively. The birds were housed in floor pens in an environmentally controlled room. Normal commercial diets were fed ad libitum and fresh water was freely available throughout the 5-week study period. Liveweights of birds and feed intake were recorded at weekly intervals. Data on carcass parameters and welfare indicators (moisture, gait scores, feather scores, breast and hip lesions, and foot pad and hock burns) were obtained on Day 35. Adrenal glands were removed at slaughter, weighed and examined histologically to determine the total proportion of cortical and medullary tissues. RESULTS: During the study, the birds at the lowest density grew faster (p<0.001-0.01) and consumed more (p<0.001- 0.01) feed than those at the other three stocking densities. The liveweight gains and feed intake of birds reared at densities of 10, 15 and 20 birds per m2 were similar (p=0.11-0.83 and p=0.17-0.57, respectively). Stocking density had no influence on the feed/weight gain, mortality or carcass characteristics. No breast or hip lesions were observed in carcasses from any of the groups. The weight and structure of the adrenal glands were similar across all groups although the staining of medullary tissue of birds was most intense in the highest stocking density group. As stocking density increased, so did moisture and gait score, hock and foot pad burn scores, and the feather score was adversely affected. CONCLUSIONS: The data showed that the relationship between stocking density and productivity traits was not linear in nature, in accordance with other studies. Under the conditions of the current study, the performance, mortality and carcass characteristics of broilers grown at densities of 10, 15 and 20 birds per m2 were similar. There were some welfare implications at high population densities as indicated by adverse effects on litter quality, gait scores and the incidence of hock and foot pad burns.     

Efficacy of praziquantel against ovine cysticercosis caused by Taenia hydatigena

Praziquantel was evaluated for its larvicidal activity against naturally or experimentally induced Taenia hydatigena infections in sheep. The major criterion used for assessing efficacy was an estimate of the dose rate required to free 90 per cent of the sheep from infection (ED90) together with a 95 per cent confidence interval. With both light and heavy infections of three-month-old T hydatigena in lambs up to 12 months old, many larvae were killed. The ED90 and 95 per cent confidence limits for six-month-old and aged organisms was estimated to be 13.1 (5.5 to 31.4) mg/kg and 6.1 (2.4 to 15.5) mg/kg, respectively. Equivalent data for the ED50 were 3.4 (1.4 to 8.3) mg/kg and 1.3 (0.3 to 5.4) mg/kg, respectively. It was established that one of the factors involved in the efficacy of praziquantel was associated with the age of the larvae at the time of treatment, the drug being markedly more effective against older than younger organisms.     

Propetamphos pour-on formulation for the control of lice on sheep: effect of lice on weight gain and wool production

Infestation of sheep with the biting louse Damalinia ovis is a potentially serious problem which can effect the quality and quantity of wool produced and may reduce weight gains. In this trial treated sheep produced 34 per cent more wool than louse-infested controls and the wool from the treated sheep was of a better quality. The mean liveweight gain in the treated groups was 18 per cent more than that in the untreated group. Treatment with a pour-on formulation of propetamphos at 25 to 50 mg kg-1 gave more than 99 per cent control of lice and protected against reinfestation for four months.     

Assessment of possible methods for estimating the stocking density of sheep being carried on commercial vehicles

Five methods for estimating the stocking density of sheep confined in a pen were assessed. The pen (2.35 m x 3.01 m) simulated the pens on a normal road transporter. The trial used 50 lambs (average weight 34 kg) of mixed sex and breed, held at five stocking densities--0.466 to 0.824 m2/100 kg or 214 to 121 kg/m2--covering the range used in commercial practice, and 14 assessors, all experienced in handling animals. The best method was that based on the girth measurement of a sample of animals to estimate liveweight and a count of the animals in the pen. The methods based on using a moveable gate to take up free floor space, assessing the difficulty of moving through the pen of animals, using photographic scales, and counting the numbers of sheep across transects were generally less successful.     

Financial benefit from the eradication of swine dysentery

Swine dysentery was eradicated from a 270 sow herd by using medication in conjunction with cleaning and disinfection, without reducing the herd size. The feed conversion efficiency, cost per kg liveweight gain and veterinary costs in the herd were compared with similar Meat and Livestock Commission recorded herds before swine dysentery entered the farm, while it was present and after its eradication. During the four years when the disease was endemic in the herd the feed conversion efficiency deteriorated by 0.58, equivalent to 7.31 pounds per pig, the cost per kg liveweight gain was 15 per cent higher and the costs of veterinary care and medicines were 1.38 pounds per pig greater. Although there were pigs with clinical swine dysentery in the herd during the four year period, the poor production figures were attributed mainly to subclinical disease. The cost of eradicating the disease was more than 20,000 pounds but this sum was recouped within 12 months by the improved production and reduced drug usage. The chances of success of such a programme have been estimated to be between 54 and 90 per cent.     

Accuracy of prediction of the liveweight of horses from body measurements

Fifty-three horses, all but two of them over two years of age and varying in type, sex and liveweight (230 to 707 kg) were weighed and seven different body measurements were recorded in duplicate by a single operator. The best overall prediction of liveweight using an equation with two variables was found to be: liveweight (kg) = (umbilical girth [cm])1.78 X (length of body from tuber ischii to elbow [cm]0.97/3011). This equation had an adjusted R2 value of 94.9 per cent and was derived from the pooled data, because differences of sex, type and weight did not significantly affect the relationship. The stable behaviour of the relationship was demonstrated by the fact that about 95 per cent of the residuals lay within +/- 53 kg, giving an average error of 4.7 per cent. The accuracy of prediction of the equation was better than the accuracy of four other established equations. A nomogram based on the equation is given.     

Acute phase response of sheep: changes in the concentrations of ceruloplasmin, fibrinogen, haptoglobin and the major blood cell types associated with pulmonary damage

The concentrations of plasma ceruloplasmin, plasma fibrinogen, serum haptoglobin and the major cell types in blood together with liveweight changes were monitored during the acute phase response in sheep. Five control sheep, five sheep that underwent sham bronchial obstruction, and five sheep that developed pneumonia after bronchial obstruction were examined. Blood samples were taken and liveweights were recorded from four to six days before until 14 days after the surgical operations (sham and bronchial obstruction). The operations led to an acute phase response in the sheep and the development of pneumonia increased and sustained the response or led to a secondary response. Statistically significant changes observed in the blood of the sheep during the acute phase response included increased concentrations of plasma ceruloplasmin and plasma fibrinogen, depression of erythrocyte numbers and elevation of neutrophil numbers (means on day of maximum change as percentage of pretreatment values; 250 per cent, 400 per cent, 80 per cent and 200 per cent, respectively). Serum haptoglobin showed a pronounced and significant increase in concentration (over 6000 per cent of pretreatment values in some sheep). All three groups of sheep showed significant depression of liveweight after overnight confinement in the surgery but this was sustained for the period of the experiment only in the bronchial obstruction group. The results indicated that measurement of the concentrations of the three plasma proteins may be more useful in the diagnosis of tissue injury and infectious disease than the number of circulating neutrophils in sheep.     

The anthelmintic efficacy of fenbendazole against a mixed nematode infection in sheep.

Fenbendazole (methyl-5-(phenylthio)-2-benzimidazole carbamate) at dose rates of 5 mg/kg and above was 100 per cent effective in eliminating a naturally acquired Dictyocaulus filaria infection in sheep. The drug was 100 per cent effective in eliminating concurrent infections of adult Trichostrongylus axei, Haemonchus contortus, Haemonchus placei, Ostertagia circumcincta, Ostertagia ostertagii, Cooperia oncophora, Cooperia mcmasterii, Nematodirus spathiger, Neumatodirus filcollis, Oesophagostomum venulosum and Chabertia ovina. Fenbendazole was 93 per cent and 97 per cent effective at doses of 5 and 10 mg/kg respectively in removing infection with adult T colubriformis, and post-treatment worm-egg production was completely suppressed in surviving female worms. No adverse side-effects were observed in treated sheep at either of the two dose rates used.     

Efficiency of bleeding of broilers after gaseous or electrical stunning

The efficiency of bleeding of broilers (g blood/kg liveweight) was measured after stunning them with either 45 per cent carbon dioxide in air for two minutes or with 2 per cent oxygen (achieved by displacing air with argon) for two minutes or with an electric current (77 or 104 mA at 50 Hz for four seconds). The results indicated that the initial rate of bleeding was higher in the electrically stunned broilers with non-fibrillated hearts than in the gas stunned broilers and electrically stunned broilers with fibrillated hearts. This difference was significant up to 60 seconds after neck cutting (P less than 0.05) but after 140 seconds all the broilers had bled out to a similar extent (30 to 33 g/kg liveweight). It is concluded that after gas stunning the time interval between neck cutting and scalding should be 60 to 140 seconds.     

High dietary niacinamide and performance of male poults at 16 weeks of age

1. Male poults were fed diets with 50 and 100 mg supplemental niacinamide/kg and grown at stocking densities of 3.2 and 4.3 birds/m2 from 56 to 112 d. 2. At 50 mg/kg niacinamide high stocking density (HSD) depressed 112 d body weight and gain from 56-112d. High dietary niacinamide (100 mg/kg alleviated the growth depression under HSD but decreased body weight gain under low stocking density (LSD). 3. Dressed yield and hock width were not affected by dietary niacinamide or stocking density. 4. Dressed carcase composition was altered by stocking density. The dressed carcase of HSD birds contained 3.7% more protein and 7% less fat. 5. High dietary niacinamide tended to increase carcase protein (+2.4%) and decrease carcase fat (-4.0%).     

Broiler performance under high stocking densities

1. In two consecutive experiments a total of 4,780 broilers were reared at high stocking densities. 2. In experiment 1, the birds were housed at 10, 20, 30, 40 or 50/m2 till 6 weeks. In experiment 2 densities of 20, 40 and 50/m2 were compared; the two higher densities were reduced to 30/m2 at either 3 or 5 weeks of age. 3. In the first experiment 6-week body weight was a curvilinear function of stocking density. Average food intake over the whole experimental period declined linearly with densities above 20/m2. 4. A slight but significant improvement in the efficiency of food utilisation was recorded from birds at high densities in the first experiment only. 5. Reducing the stocking density from 40 or 50/m2 to 30/m2 at 3 weeks increased food consumption and body weight gain and led to a recovery in their body weight by 6 weeks. 6. No significant differences were observed in mortality as a result of high stocking densities in either experiment. 7. Profit margin per m2 increased almost linearly in experiment 1, by about 65 p for every bird/m2 increase in stocking density. 8. The implications for poultry welfare are briefly discussed.     

桑树群体结构的研究 Ⅳ.群体结构与物质生产

不同密度新一之濑桑园,栽植后头5年内,桑叶产量变动在306.4—2625.6公斤·亩~(-1)·年~(-1)之间,净初级生产力变动在8—16吨·公顷~(-1)·年~(-1)之间,收获指数在0.3—0.6之间,光能利用率在0.3—0.7％(以年为基础)和0.4—1％(以生长季节为基础)之间。密植和推迟开剪年份能增加桑叶产量和提高桑园的净初级生产力及光能利用率。密植会降低收获指数,而提早开剪则有增加收获指数的倾向。     

A study of tail tip necrosis in young fattening bulls on slatted floors

A questionnaire sent to 78 producers revealed that tail tip necrosis was seen only in units with fattening bulls housed on slatted floors. Out of 43 such units, 20 (46.5 per cent) reported that tail tip necrosis was a herd problem. All 43 herds were visited, owners were interviewed and housing and management data recorded. It is concluded that tail tip necrosis is a multifactorial disease. The initial lesion is caused by tramping, but the following factors are essential in the development and severity of the disease, i) slatted concrete floors, ii) close confinement, iii) hot season and iv) body weight above 200 kg. The stocking density (expressed as kg bodyweight per square meter pen) was significantly higher in problem herds (210 kg/m2) than in control herds (165 kg/m2). There was a close relationship between high environmental temperature and tail tip necroses. The majority of incidents occurred during the warm season (May through September), very few cases were seen during the colder months. The general morbidity and mortality rates were significantly higher in problem herds than in control herds. Microbiology of affected tails revealed mixed infections in most cases, with Corynebacterium pyogenes and Bacteroides melaninogenicus as the most frequently isolated organisms. Principles of treatment and prevention are discussed. There is evidence to assume that a 10-20 per cent reduction in stocking density could be an efficient prophylactic measure.