Risk factors for calf mortality in large Swedish dairy herds

The aim of this study was to identify possible risk factors for 1-90 day calf mortality in large Swedish dairy herds. Sixty herds with a herd size of ≥160 cows were visited once between December 2005 and March 2006. Thirty herds were known to have low mortality (LM) and 30 were known high mortality herds (HM). Upon the visit, data about housing and management was collected from interviews with personnel responsible for the calves. The herd status regarding the calves' passive transfer (total protein), levels of α-tocopherol, β-carotene and retinol, and excretion of faecal pathogens (Cryptosporidium spp., Escherichia coli F5, rota and corona virus) was evaluated based on targeted sampling of high risk calf groups; in each herd, blood and faecal samples were collected from calves 1-7 and 1-14 days old, respectively. Similarly, the herd status regarding clinical respiratory disease in calves and history of respiratory virus exposure was evaluated based on lung auscultations and blood samplings of calves 60-90 days old. The median calf mortality risk (in calves 1-90 days of age) among HM herds was 9% (Range: 6-24%) and among LM herds 1% (Range: 0-2%). LM and HM herds were compared using five logistic regression models, covering potential risk factors within different areas: "Disease susceptibility", "Factors affecting the gastrointestinal tract", "Factors related to transmission of infectious disease", "Hygiene" and "Labour management". The percentage of calves, 1-7 days old, with inadequate serum concentrations of α-tocopherol and β-carotene were significantly higher in HM herds compared to LM herds and also associated with higher odds of being a HM herd (OR=1.02; p=0.023 and OR=1.05; p=0.0028, respectively). The variable "Average number of faecal pathogens in the sampled target group" was significantly associated with higher odds of being a HM herd (OR=4.65; p=0.015), with a higher average in HM herds. The percentage of calves with diarrhoea treated with antibiotics was significantly higher in HM herds and was associated with higher odds of being a HM herd (OR=1.08; p=0.021). The median age at death of calves in the age interval 1-90 days that died during a one-year period was significantly lower among HM herds (13 days) than in LM herds (24 days) (p=0.0013) The results indicate that gastrointestinal disorders may be an important cause of calf mortality in large Swedish dairy herds. Furthermore, our study provides additional indications that fat soluble vitamins might play an important role for calf health.     

How to reduce the incidence of black bean aphids (Aphis fabae Scop.) attacking organic growing field beans (Vicia faba L.) by growing partially resistant bean varieties and by intercropping field beans with cereals

Abstract

There is an increasing demand for organically grown pulses and cereal grains in Denmark, which is expected to cause a change in the typical organic farm structure away from dairy farming and towards arable farming. Spring field beans (Vicia faba) could be a popular break crop in organic agriculture. The black bean aphid (Aphis fabae) is generally considered to be a serious pest of spring-sown field beans in northern Europe, and field studies have shown that yield losses can exceed more than 50% due to attacks from the black bean aphid.

The use of insecticides in organically grown field bean crops is not permitted, but it has been known for a long time that the black bean aphid infests different varieties of beans to a very different extent. Therefore, partial resistance to the black bean aphid is one method of stabilizing yields. Another method of cultural pest control is intercropping and a third method could be a combination of both. Six field experiments involving the three methods were carried out. There was a significant difference between the number of aphids per plant on the three investigated bean varieties, where ‘Colombo’ was the most susceptible, ‘Quattro’ was intermediate, and ‘Caspar’ the most resistant variety. ‘Colombo’ intercropping with spring wheat and spring barley reduced the numbers of aphids per plant significantly, and also the number of plants infested. The harvesting of all crops took place during the last fourteen days of August.

It can be concluded that the growing of partial host plant resistant varieties of field beans or the intercropping of field beans with spring cereals separately will reduce the infestation with black bean aphids. If both methods are used, the reduction of infestation will be even higher and consequently also the yield.     

Predicting seed yield in perennial ryegrass using repeated canopy reflectance measurements and PLSR

Abstract

Repeated canopy reflectance measurements together with partial least-squares regression (PLSR) were used to predict seed yield in perennial ryegrass (Lolium perenne L.). The measurements were performed during the spring and summer growing seasons of 2001 to 2003 in three field experiments with first year seed crops using three sowing rates and three spring nitrogen (N) application rates. PLSR models were developed for each year and showed correlation coefficients of 0.71, 0.76, and 0.92, respectively. Regression coefficients showed in these experiments that the optimum time for canopy reflectance measurements was from approximately 600 cumulative growing degree-days (CGDD) to approximately 900 CGDD. This is the period just before and at heading of the seed crop. Furthermore, regression coefficients showed that information about N and water is important. The results support the development of an additional N- and water-application model which will calculate the application rate of N and water according to expected seed yield.     

OPTIMUM DISTRIBUTION BETWEEN AUTUMN-APPLIED AND SPRING-APPLIED NITROGEN IN SEED PRODUCTION OF TALL FESCUE

The effect of different autumn and spring nitrogen (N) application rates on plant establishment, plant development, and seed yield were tested in a field experiment using tall fescue (Festuca arundinacea Schreb.). Results clearly showed that the optimum distribution of N between autumn and spring to achieve the highest seed yield and economical benefit was dependent on the choice of cover crops and location. The economically optimum N application rate was in the range from 44 to 73 kg ha^?1 in autumn and 94 to 157 kg ha^?1 in spring. The results are discussed in relation to Danish N regulations and plant establishment and development.     

Effect of Supplemental Feeding with Glycerol or Propylene Glycol in Early Lactation on the Fertility of Swedish Dairy Cows

The aim of this field study was to evaluate the effect of supplemental feeding with glycerol (GLY) or propylene glycol (PG) during early lactation on the fertility of Swedish dairy cows. Within 17 commercial dairy herds, 798 cows were randomized to three groups that were daily fed supplements with 450 g GLY, 300 g PG or nothing (control, C). The supplements were given twice daily during 0–21 days in milk as a top dress on concentrates. Data on calving date, insemination dates, gynaecological examinations, as well as breed, parity and monthly milk yield were collected. From a subset of 308 cows in seven herds, milk samples for progesterone analysis were taken twice weekly and used to determine the time for onset of luteal activity. The effects of supplements on the intervals from calving to first luteal activity (FLA), first AI (FAI) and conception (CON), respectively, were analysed using semi‐parametric survival models (Cox proportional hazards models) controlling for the effect of parity, breed, calving season, milk yield and the clustering effect of herd. There was no difference in time to FLA between the cows in group C and in group GLY or PG. No differences in time to FAI or in time to CON were found between cows in group PG and group C. However, cows in the GLY group tended to get their FAI later compared with cows in the control group but without at subsequent delaying of time to CON.     

Changes in the blood composition of calves during experimental and natural infections with Eimeria alabamensis

Two trials were carried out to assess the changes in blood composition of calves infected either experimentally or naturally with Eimeria alabamensis. In the first, 12 calves were dosed orally with 10 to 400 million sporulated oocysts and compared with three control calves. The second trial used eight calves turned out to graze a permanent pasture known to induce E alabamensis coccidiosis in calves and eight calves turned out on to a previously ungrazed pasture. In both trials the serum activities of glutamate dehydrogenase (GLDH) and alkaline phosphatase (AP) and the serum concentration of total bile acids decreased in the infected animals while total bilirubin increased. The changes in GLDH, bile acids and bilirubin were most pronounced just before the calves began to excrete oocysts. In the first trial the lowest AP activity was observed 10 days after infection, but in the second its activity continued to decrease throughout the trial. In the first trial haematology, serum fibrinogen, total protein and protein fractions were also investigated. All the significant changes were small and the potential of the investigated blood components as diagnostic markers is therefore minimal.     

Hyperphosphorylation of cereal starch

Plant starch is naturally phosphorylated at a fraction of the C6 and the C3 hydroxyl groups during its biosynthesis in plastids. Starch phosphate esters are important in starch metabolism and they also generate specific industrial functionality. Cereal grains starch contains little starch bound phosphate compared with potato tuber starch and in order to investigate the effect of increased endosperm starch phosphate, the potato starch phosphorylating enzyme glucan water dikinase (StGWD) was overexpressed specifically in the developing barley endosperm. StGWD overexpressors showed wild-type phenotype. Transgenic cereal grains synthesized starch with higher starch bound phosphate content (7.5 (±0.67) nmol/mg) compared to control lines (0.8 (±0.05) nmol/mg) with starch granules showing altered morphology and lower melting enthalpy. Our data indicate specific action of GWD during starch biosynthesis and demonstrates the possibility for in planta production of highly phosphorylated cereal starch.     

RADIOGRAPHIC HEART-VOLUME ESTIMATION IN NORMAL CATS

Heart volume mensuration was evaluated on conventional radiographs from eight normal cats in different body positions using computed tomography (CT). Heart volumes were calculated from orthogonal thoracic radiographs in ventral and dorsal recumbency and from radiographs exposed with a vertical X-ray beam in dorsal and lateral recumbency using the formula for an ellipsoid body. Heart volumes were also estimated with CT in ventral, dorsal, right lateral and left lateral recumbency. No differences between heart volumes from CT in ventral recumbency and those from CT in right and left lateral recumbency were seen. In dorsal recumbency, however, significantly lower heart volumes were obtained. Heart volumes from CT in ventral recumbency were similar to those from radiographs in ventral and dorsal recumbency and dorsal/left lateral recumbency. Close correlation was also demonstrated between heart volumes from radiographs in dorsal/ left lateral recumbency and body weights of the eight cats.     

Cryptosporidium parvum and Giardia intestinalis in calf diarrhoea in Sweden

The objective of this study conducted in 75 herds was to investigate the presence and significance of Criptosporidium parvum and Giardia intestinalis in Swedish dairy calves in comparison with rotavirus, coronavirus and Escherichia coli K99+. The farmers were asked to collect faecal samples from each heifer calf that had diarrhoea between birth and 90 days of age, and also from a healthy calf of the same age. In total, 270 samples were collected and analysed. C. parvum, either alone or together with G. intestinalis and/or rotavirus, was detected in 16 (11%) and 6 (5%) of the samples from diarrhoeic and healthy calves, respectively. Even though a higher proportion of diarrhoeic calves shed C. parvum, the difference between the groups was not statistically significant (p = 0.067), possibly due to the low number of positive samples. G. intestinalis was found in 42 (29%) of the diarrhoea samples and in 29 (23%) of the samples from healthy calves. Rotavirus and coronavirus were demonstrated in 24% and 3% of the diarrhoea samples, respectively, whereas E. coli K99+ was only found in samples from 2 healthy calves. C. parvum and G. intestinalis were found in samples from calves 7 to 84 days of age and during all seasons. The results confirm that C. parvum is present in Swedish dairy herds and might have clinical significance. G. intestinalis was the most common agent found but the importance of this parasite remains unclear. Both parasites have suggested zoonotic potential and thus warrant further attention. In addition, rotavirus is a major pathogen in neonatal enteritis in Sweden, whereas coronavirus and E. coli K99+ seem to be of less importance.