1997 * VIII * 4

A. Bender.  
  The winterhardiness of alfalfa species and cultivars 291
The winterhardiness of alfalfa species and cultivars. The winterhardiness of 134 alfalfa cultivars from 20 different countries was investigated in 4 field trials at Jõgeva Plant Breeding Institute (58°45' north latitude, 26°24' east longitude, the yearly average air temperature 4.4°C, precipitation 655 mm) during 1982-1990. The investigation included 63 cultivars of the species Medicago sativa L., 68 of Medicago media Pers., 2 of Medicago falcata L. and 1 of Medicago borealis L. The vast majority of the cultivars' seeds originated from the gene bank of VIR. Research was carried out in spaced-plant plantation (90×90 cm), the winterhardiness of cultivars was assessed on the basis of plants' survival.

Minimal air temperature and the sum of mean diurnal negative air temperatures (in the presence of sufficient snow cover) were not the reasons for bad winter survival during the conducting of the trials. A lot of alfalfa plants were lost winters with sudden and large temperature fluctuations. Heat waves occurred in December and January during these years when the air temperature rose to 4-6°C and it was raining. The shallow soil layer thawed, saturated with melted snow and ice, and later on an ice crust formed.

The winter survival of red clover in tame hay swards (assessed with suffusion) and that of alfalfa were not always similar in Jõgeva. The winters occurred when red clover had satisfactory winter survival in Estonia and alfalfa overwintered well in Jõgeva and vice versa.
As was also the case in several previously published research papers in Estonia we had to experience the unreliability M. sativa L. cultivars of southern origin in Estonian climatic conditions. Only in very favourable wintering conditions during the first hibernation did their sward maintain the necessary density for considerable yield capacity.

Cultivars of M. media Pers. had better winter survival than those of M. sativa L. in the trials. There were 19 foreign cultivars among the former ones (18 originating Commonwealth of Independent States (CIS), 1 of Canadian origin), winterhardiness of which turned out to be good (60-80% of the plants survived until the end of the growing season of the third year of use) or excellent (80-100% of the plants survived until the end of the growing season of the third year of use) in Estonian conditions. On the basis of the trial results so far, the economic traits of the following M. media Pers. cultivars should be checked in state testing: 'Kamalinskaya 930' (86.7% of the plants survived the autumn of the third year of use in Jõgeva), 'Marusinskaya 425' (84.2%), 'Barnaulskaya 171' (83.8%), 'Kamalinskaya 530' (80.0%), 'Taezhnaya' (79.2%), 'Zabaikalka' (79.2%), 'Omskaya 8893' (77.1%), 'Biiskaya 3' (75.4%), 'Oranzhevaya 115' (74.2%), 'Zheltogibridnaya 99' (70.0%), 'Kazanskaya 64/95' (69.6%), 'Iskra' (67.5%), 'Karatshinskaya' (67.5%) and 'Kazanskaya 36' (66.7%).

The tested cultivars of M. falcata L. and M. borealis L. revealed good or excellent winterhardiness but their yield capacity is lower than that of M. media Pers. cultivars.

Considering that Estonian soils are sporadically very stony and that machinery and energy have become several times more expensive, it would be reasonable to test the cultivars of variegated and yellow-flowered M. media Pers., M. falcata L. and M. borealis L. separately in state testing. The State Variety List can be kept in a respective way. The current testing order, after which the yield of the three years of use is determined, does not expose the advantages of these species (hybrids) arising from their different longevity.

P. Elias.  
  The effect of the thermophilic lactic acid bacteria, mesophilic lactobacilli and propionic acid bacteria single strain starter cultures on microbiological processes in emmental cheese 311
The Effect of the Thermophilic Lactic Acid Bacteria, Mesophilic Lactobacilli and Propionic Acid Bacteria Single Strain Starter Cultures on Microbiological Processes in Emmental Cheese. The effect of the thermophilic streptococci, lactobacilli, mesophilic lactobacilli and propionic acid bacteria single strain starter cultures on microbiological processes in making of Emmental cheese was studied.

The count of the lactococci increased in pasteurized milk about 1.3 times when it was ripened (9-12 °C; 16-20 hours) with mesophilic starter cultures of lactococci, and they became dominating microorganisms in milk. When thermophilic streptococci, lactobacilli and L. casei single strain starter cultures were added to milk, the milk contained considerably more thermophilic and mesophilic lactobacilli and less thermophilic streptococci, compared with using of the mixed thermophilic culture TMB. These differences were caused by starters. The relation between lactobacilli and streptococci changed in cultivating of the mixed bulk starter culture TMB. This changed relation was carried in to milk by adding of the mixed starters and from milk to the cheeses in cheesemaking. The differences between the cheeses of the thermophilic lactic acid bacteria and the cheeses made with monocultures, compared to the cheeses, which made with the mixed bulk starter TMB, remained in case of streptococci for 30 days and in case of lactobacilli for 3 months. It affected significantly pH and through it the quality of the cheeses. The count of the mesophilic lactobacilli increased in milk by adding Lactobacillus casei T and it stabilized multiplication of the lactobacilli from raw milk. The raw milk contamination with aerobic spore forming bacteria was small and their multiplication in cheeses slow. Using of different lactic acid starter cultures did not have any effect on the counts and multiplication of the spores.

When monocultures of the thermophilic lactic acid bacteria were used, the multiplica-tion of propionic acid bacteria was more intensive and the count of them significantly higher in two or three months old cheeses, compared with cheeses made with the mixed culture TMB. Our results showed that cheesemaking with the selected starter cultures of the propionic acid bacteria, which grew well together with the mesophilic and thermophilic lactic acid starter cultures and very slowly at low temperatures (below 10 °C) gave us one of the possibilities to regulate the propionic acid fermentation in ripening of Emmental cheeses.

Key words: thermophilic lactic acid streptococci and lactobacilli, mesophilic lactoba-cilli, propionic acid bacteria, starter, Emmental cheese.

H. Kaldmäe, M. Vadi.  
  Feeding cellobacterin to calves and dairy cows 325
Feeding cellobacterin to calves and dairy cows. Cellobacterin was worked out on the basis of cellulolytic, nitrogen-binding bacteria and lactobacilli of the rumen. It is based on rapeseed or sunflower cake.

The authors explained the influence of cellobacterin on the health, development and live weight gain of the calves.

The following problems were under investigation: the most proper way of giving cello-bacterin to calves; the amount and influence of cellobacterin on rumen microflora and -fauna; the influence of the population of rumen microbes on digestibility of the ration.

The authors explained the influence of cellobacterin on the milk yield of cows in the spring and autumn transitional periods when the rations changed.

Five feeding trials, one digestion trial and an investigation into the degradability of feeds in fistulated cows were carried out.

During the first trial the average daily gain of the 1st group (control group) calves was 748 g, these values for the 2nd and 3rd group were 881 g and 809 g accordingly.

Cellobacterin increased the total account of microbes in the rumen of the calves by 1.6 times and the number of cellulolytical bacteria by 2.6 times. The use of cellobacterin improved the digestibility of crude fibre and crude fat by 3.3% in calves.

We recommend that cellobacterin be added to the rations of calves beginning from the age of 2-2.5 months that they be fed 1 g of it per 10 kg body weight with concentrated feed every fifth day.

When the feed rations of the cows changed, cellobacterin guaranteed more stabile microbe populations during the adaption period.

Cellobacterin increased the number of cellulolytical bacteria and improved the degradability of nutrients. During the change of rations, a fall in milk yield can be avoided if cellobacterin is used.

Key words: probiotic, cellobacterin, calves-, cows-, milk-yield, live weight gain, calf-feeding, cattle-feeding.

H. Kärblane, L. Kevvai, J. Kanger.  
  Heavy metals in potatoes 335
Heavy Metals in Potatoes. There are always heavy metals in smaller or larger quantities in potatoes. The content of these in the dry matter of potatoes grown in Estonia is characterised by data presented in Table 1. It can be seen that there is always a smaller degree of dangerous heavy metals (Pb, Cd, Hg) in potatoes than the maximum allowed grade in Estonia for table potatoes. The permitted grade for Pb is 3.0, for Cd 0.2 and for Hg 0.1 mg/kg in dry matter. Of the samples collected from 69 different Estonian regions only one contained more Cd than permitted, being 0.22 mg/kg in dry matter.

In potatoes there are also a few heavy metals (Mn, Zn, Cu, Co, Mo) that are seen as micro-elements. In no case is there a larger amount of these than allowed in food potatoes.

The content of heavy metals in different organs of the potato plant (roots, stalks, tubers) vary (Table 2). There are always more heavy metals in potato peel than in the inside of the tuber (Table 3).

The content of heavy metals in potatoes varies considerably (Table 1), being affected by the content of the corresponding heavy metal in the soil of the growing area, by the soil reaction, humus content, soil characteristics and fertilising. The variety of potato plays no role in the content of heavy metals.

Ü. Pavel.  
  Assessment of general toxicity of plant by means of bioassay 348
Assessment of general toxicity of plant pollutants by means of bioassay. It is recommended that the embryotoxicity and immunosuppressive effect of pollutants be assessed during the perinatal period of chick development (measuring the perinatal mortality). On the 9th day of incubation the chloroform-ethanol (80:20 v/v) extracted material suspension in plant oil was injected into allantois (0.1 ml), as in Adebajo and Oyesiku (1994). The embryonic mortality is registered on the 12th and 18th incubation day and on the day of hatching. For the assessment of the immunosuppressive impact of the plant extract we are guided by R. R. Lochmiller et al. (1993). On the 10th post-hatching day the New Hampshire chicks (20 fertilized eggs were taken as control and 20 for the experiment) were challenged subcutaneously with Salmonella gallinarum killed cells (0.1 ml, 108 cells). On the 8th postvaccinational day the chicks were bled and the specific agglutinin titers (log2) were determined. The body mass, the mass of the spleen and bursa Fabricius were also determined.

On the 15th day of their life, the CMI of the chicks was assessed by a phytohemaggluti-nin (PHA-P, Sigma, USA) skin test, injecting 0.05 ml (100 μg). After 24 hours the reaction was determined.

V. Tominga, T. Paaver.  
  The dressing percentage and proportions of body components of different species and hybrids of suregon reared in a recirculation system 351
The dressing percentage and proportions of body components of different species and hybrids of sturgeon reared in a recirculation system. The dressing percentage and relative weight of the head, viscera and backbone of three species (Russian, Siberian and Sterlet) and two interspecies hybrids (Russian × Siberian sturgeon and Bester) of stur-geon from the Pringi recirculated fish farming system was studied. All the analysed fish were immature weighing 900-9200 g. There were no significant differences between the species; the dressing percentage depended mostly on the size of the fish. The fillet (with skin, scutes and fins) percentage was 50-69 %, with an average of a 60 %. Small fish, weighing less than 2 kg had a significantly lower dressing percentage. In the larger fish there was no correlation between weight and dressing percentage. The fillet percentage correlated positively with Fulton’s condition factor and negatively with the weight of the head. The correlation between the weight and condition factor or the relative weight of the head was weaker in the sample of Russian sturgeon than in Bester. The percentage of consumable parts of sturgeon is approximately the same as in other farmed fish, although the body shape of sturgeon is different.
J. Kuum.  
  Kasoraan prevents a mildew 359