Ultrasound emission after cycles of water stress in Picea abies

The relationships among rate of ultrasound acoustic emission (AE), xylem water potential and transpiration rate were investigated in 5-year-old potted saplings of Picea abies Karst. after cycles of water stress. Water-stressed plants displayed minimum xylem water potentials of -3.9 MPa, near-zero transpiration rates and up to 45 AE counts per minute. After rewatering, water-stressed plants no longer produced AEs. Well-watered control plants produced only a small number of ultrasonic AEs. After three cycles of water stress (lasting 24 days in total), it was estimated that about two-thirds of the functional tracheids were embolized. The concomitant reduction in hydraulic conductance was about 70%.     

Rickets in alpacas (Lama pacos) in New Zealand

Rickets was diagnosed in two weaner alpacas from a flock showing ill thrift and lameness during the winter of 1992. Both animals had abnormally shaped ribs with occasional healing fractures, irregular thickening of growth plates and metaphyseal haemorrhages. The mean serum phosphorus concentrations of the alpacas fell during June and July, even though lambs grazing the same pasture had normal serum phosphorus concentrations and the phosphorus concentration of the pasture was considered adequate. Vitamin D deficiency may also have contributed to the osteodystrophy. The alpacas had a thick fleece during the winter, and diurnal Vitamin D, synthesis resulting from solar irradiation is likely to have been minimal, especially considering the reduced sunshine hours recorded during the 1992 winter. Surviving alpacas recovered after treatment with monosodium phosphate and an oral Vitamin D supplement. It is possible alpacas are more susceptible to deficiencies of phosphorus and Vitamin D than other grazing animals in New Zealand.     

A review of tissue reference values used to assess the trace element status of farmed red deer (Cervus elaphus)

AIMS: This paper reviews the principles for the establishment of biochemical reference criteria for assessing the trace element status of farmed livestock and summarises data for copper, selenium, vitamin B12 and iodine for farmed red deer. COPPER: Enzootic ataxia and osteochondrosis occur when liver copper concentrations are below 60 micromol/kg fresh tissue, and serum copper concentrations are below 3-4 micromol/l. Growth responses to copper supplementation have been equivocal when blood copper concentrations were 3-4 micromol/l, but were significant when mean blood copper concentrations were 0.9-4.0 micromol/l. No antler growth or bodyweight response to copper supplementation was observed when blood ferroxidase levels averaged 10-23 IU/l (equivalent to serum copper concentrations of 6-13 micromol/l) and liver copper concentrations averaged 98 mumol/kg fresh tissue. These data suggest that 'deficient', 'marginal' and 'adequate' ranges for serum copper concentrations should be 5, 5-8, and 8 micromol/l, respectively, and those for liver copper concentrations should be 60, 60-100, and 100 micromol/kg, respectively. SELENIUM: White muscle disease has been reported in young deer with blood and liver selenium concentrations of 84-140 nmol/l and 240-500 nmol/kg fresh tissue, respectively. No growth-rate response to selenium supplementation occurred in rising 1-year-old deer when blood selenium concentrations were less than 130 nmol/l, the range in which a growth-rate response would be expected in sheep. VITAMIN B12: Vitamin B12 concentrations in deer are frequently below 185 pmol/l without clinical or subclinical effects. No growth response was observed in young deer with vitamin B12 concentrations as low as 75-83 pmol/l. A growth response to cobalt/vitamin B12 supplementation occurs in lambs with serum vitamin B12 concentrations 336 pmol/l. CONCLUSIONS: Data that can be used to establish reference ranges for assessing trace element status in deer are limited. More robust reference values for farmed red deer need to be established through further studies relating biochemical data to health and performance.     

Concentrations of macro- and micro-elements in the milk of pasture-fed thoroughbred mares

OBJECTIVE: To determine the changes in Ca, P, Mg, Na, K, S, Cu, Fe and Zn concentrations of milk during the lactation in pasture-fed Thoroughbred mares and then calculate the dietary mineral requirements of the sucking foal and the lactating mare. PROCEDURE: Milk was sampled on days 1, 3, 7, 14, 21, 28 and at various times between 55 to 65, 85 to 95 and 135 to 150 days after parturition from 21 pasture-fed mares. The concentrations of macro- and micro-elements in the milk were determined by inductively coupled plasma emission spectrometry. RESULTS: Concentrations (mg/L) of these elements were highest in colostrum (Mg 302, Na 561, K 955, S 1035, Cu 0.76, Fe 0.79 and Zn 5.5) except for Ca (1245) and P (895), which where highest on day 7. The mean milk mineral element concentrations (mg/L) over days 55 to 150 were Ca 843, P 543, Mg 47, Na 120, K 590, S 219, Cu 0.19, Fe 0.34 and Zn 2.1. The mean plasma element concentrations (mg/L) over the same period were Ca 120, P 77.1, Mg 17.0, Na 3110, K 168, S 983, Cu 1.1, Fe 1.5 and Zn 0.49. Concentration gradients between plasma and milk were observed and, in the case of Ca, P, Mg, K and Zn, their concentrations in milk were greater than those in plasma, while a reverse situation was observed for Na, S, Cu and Fe. CONCLUSION: With the exception of Ca and P, the highest concentrations of mineral elements were observed in the colostrum. The nursing foal should have access to good pasture or creep feed, because the intakes of Ca, P and Cu from milk may be less than optimum to meet the daily mineral element requirements.     

The effect of increasing the Vitamin B12 status of Romney ewes on foetal liver Vitamin B12, milk Vitamin B12 and liver Vitamin B12 concentrations in suckling lambs

AIM: To determine the effect of increasing the Vitamin B12 status of the ewe on the Vitamin B12 supply to the suckling lamb. METHODS: The Vitamin B12 status of the ewe was increased during gestation and lactation by three injections of a long-acting preparation of Vitamin B12 microencapsulated in an organic acid polymer. The Vitamin B12 status of the ewes and suckling lambs was assessed from changes in serum and liver Vitamin B12 concentrations. RESULTS: Compared to untreated animals, serum and liver Vitamin B12 concentrations of the treated ewes were increased at least 70% during gestation. Foetal liver Vitamin B12 concentrations were increased 270%. Over the lactation, ewe serum and milk Vitamin B12 concentrations were increased at least 200% and 44%, respectively. The liver Vitamin B12 stores of the newborn lambs from Vitamin B12-treated ewes were depleted within 58 days. There were no significant differences in the serum Vitamin B12 concentrations of suckling lambs from Vitamin B12-treated and untreated ewes. CONCLUSION: Ewes with a high Vitamin B12 status will ensure an adequate supply of Vitamin B12 to their lambs for at least the first 30 days of life. CLINICAL SIGNIFICANCE: In flocks grazing Co-deficient pastures, treating ewes with a long-acting Vitamin B12 supplement at mating will prevent Vitamin B12 (Co) deficiency in ewes, as well as their lambs, until they can be treated at tailing at 4-6 weeks of age.     

Determination of the digestible energy intake and apparent absorption of macroelements in pasture-fed lactating Thoroughbred mares

AIM: To measure the nutritive value of pasture in terms of digestible energy (DE) intake (DEI) and dry matter (DM) digestibility, and to determine the apparent absorption of macroelements in lactating Thoroughbred mares grazed on pasture. METHODS: DM intake (DMI) and DEI were determined from daily faecal DM output measured in grazing mares, divided by the DM indigestible fraction (1-digestible DM), measured in a digestibility trial using pasture-fed mares. Eight lactating mares and their foals, that had a mean age of 40 days, were grazed separately on 50x100 m areas of pasture and daily faecal DM outputs were recorded for 8 days. Five mares and their foals were then placed in individual bare 20x20 m corrals containing custom-made feeding stations for 14 days to determine the indigestible DM fraction. DM, gross energy content, crude protein (CP), soluble carbohydrate, acid detergent fibre (ADF), neutral detergent fibre (NDF), lipid, and macroelement composition of the pasture offered and faeces were determined and their digestibility and/or apparent absorption calculated. RESULTS: DM digestibility of the pasture was 0.6 and the DMI and DEI of a grazing 560 kg mare in early lactation nursing a foal growing at 1.34 kg/day was 13.6 (SE 0.8) kg/day and 146.9 (SE 8.4) MJ DE/day, respectively. Apparent absorptions of the macroelements measured were: Ca 0.75, P 0.43, Mg 0.63, Na 0.78, and K 0.72. CONCLUSIONS: Good quality ryegrass-white clover pasture that had a DE content of 10.8 MJ/kg DM, and a macroelement composition (g/kg) of Ca 3.33, P 3.0, Mg 1.67, Na 1.67, and K 24.2, will provide adequate DMI, DEI, and macroelement intake to lactating Thoroughbred mares.     

The effect of long-acting injectable selenium formulations on blood and liver selenium concentrations and liveweights of red deer (Cervus elaphus)

AIM: To evaluate the efficacy of a new long acting injectable selenium ( Se ) formulation to increase the Se status and prevent Se deficiency in red deer. METHODS: Groups of weaned red deer (four stags and six hinds/group) grazing pastures containing <30 mg Se/kg DM were injected subcutaneously with either 0.5, 1.0 or 2.0 mg Se/kg as a new formulation of BaSeO4 (Deposel Multidose), 1.0mgSe/kg of a current formulation (Deposel), or not treated. Blood Se concentrations and liveweight were measured nine times at intervals over 377 and 270 days, respectively. RESULTS: Both formulations of Se elevated blood Se concentrations from 105 nmol/l pre-injection for at least 377 days with peak levels of 1894, 1395 and 818 nmol/l for high, medium and low doses of Deposel Multidose, respectively, at 73141 days, and 1508 nmol/l at 73-141 days for the medium dose of Deposel, which persisted at similar levels for the duration of the study. Deposel Multidose produced fewer and less severe subcutaneous tissue reactions than Deposel. Pastures contained 10 to 30 mg Se/kg DM. There was no significant difference in growth rate between treated and control deer. There was a significant (p<0. 01) linear relationship (y = 1.25x + 71.6, R2=0.86) between blood (x) and liver (y) Se concentrations in the range of 120 - 2100 nmol/l for blood concentrations, and 200 - 3000 nmol/kg for liver concentrations. CONCLUSION: Injections of BaSeO4 in both formulations studied were effective in increasing the Se status of deer but the new formulation produced fewer and less-severe tissue reactions. Young growing red deer appear less sensitive to Se deficiency as measured by weight gain, than sheep and cattle, suggesting that reference ranges for those species are not appropriate for deer. There was a linear correlation between blood and liver selenium concentrations.     

Photosynthetic capacity in a central Amazonian rain forest

The vertical profile in leaf photosynthetic capacity was investigated in a terra firme rain forest in central Amazonia. Measurements of photosynthesis were made on leaves at five levels in the canopy, and a model was fitted to describe photosynthetic capacity for each level. In addition, vertical profiles of photosynthetic photon flux density, leaf nitrogen concentration and specific leaf area were measured. The derived parameters for maximum rate of electron transport (J(max)) and maximum rate of carboxylation by Rubisco (V(cmax)) increased significantly with canopy height (P < 0.05). The highest J(max) for a single canopy level was measured at the penultimate canopy level (20 m) and was 103.9 &mgr;mol m(-2) s(-1) +/- 24.2 (SE). The highest V(cmax) per canopy height was recorded at the top canopy level (24 m) and was 42.8 +/- 5.9 &mgr;mol m(-2) s(-1). Values of J(max) and V(cmax) at ground level were 35.8 +/- 3.3 and 20.5 +/- 1.3 &mgr;mol m(-2) s(-1), espectively. The increase in photosynthetic capacity with increasing canopy height was strongly correlated with leaf nitrogen concentration when examined on a leaf area basis, but was only weakly correlated on a mass basis. The correlation on an area basis can be largely explained by the concomitant decrease in specific leaf area with increasing height. Apparent daytime leaf respiration, on an area basis, also increased significantly with canopy height (P < 0.05). We conclude that canopy photosynthetic capacity can be represented as an average vertical profile, perturbations of which may be explained by variations in the environmental variables driving photosynthesis.     

《饲料博览》（管理版）杂志

牛奶和奶制品如果能作为提供促进健康的特定营养素的传递系统，它将变得更具吸引力和价值。牛奶营养素的改善可以通过一些方式来实现，较好的方式有：改变机体内环境和直接调控农场的食物来源而不需要后续的操作。适合于典型牧场实践的方法，包括对理想表型性状的。选择，特定的营养饲料，长效的外源补充剂和瘤胃茵群的改善。