The response of turkeys to dietary balanced protein during two periods of growth.

1. Two experiments were conducted to measure the response of growing turkeys to dietary protein content. In the first, 960 sexed British United Turkey (BUT 6) poults were used to measure the response to balanced protein from 3 to 6 weeks of age. In the second, 1440 sexed BUT and Hybrid Converter poults were raised from 14 to 17 weeks.2. In both experiments, six levels of dietary protein were fed, with feed intake, body and feather weight gain and changes in body composition measured. The levels of protein chosen ranged from 0.53 to 1.2 of the Aviagen requirements for growing turkeys.3. In the first experiment, six poults were sampled from each sex at the start of the experiment for carcass analysis, and four were sampled from each strain and sex in the second. At the end of each experiment, eight poults from each treatment were sampled. Body composition analyses were made on individual defeathered birds.4. Weight gain increased linearly with protein intake in the early period and exponentially in the later period. In both periods, feed intake decreased as protein content reduced.5. In the early period, body lipid content increased from 20.2 to 41.5 g/kg body weight, as dietary protein content decreased, but there was no change in the later period. Efficiency of utilisation of dietary protein declined linearly with an increase in dietary protein content, from 0.87 to 0.46 g/g in the first, and from 0.43 to 0.27 g/g in the later period.6. The inability of the growing turkey to increase feed intake on marginally limiting feeds may have been due to a genetic constraints to store excess energy consumed as body lipid, resulting in the observed decrease in feed intake as dietary protein content is reduced.

Dietary energy:protein ratio influences the efficiency of utilisation of dietary protein by growing turkeys.

1. The following experiment was designed to confirm that the efficiency of dietary protein utilisation (ep) can be reduced when the AMEn to digestible crude protein (DCP) ratio of the feed falls below a critical level. In addition, whether the efficiency would be improved at high DCP contents through the addition of oil or starch was determined.2. A 14d trial (starting at 21 d of age), using BUT 6 turkeys, was designed to measure the effects on ep of four feeds (12.1 MJ AMEn/kg) with AMEn:DCP ratios ranging from 45 to 72 MJ AMEn/kg, and two additional feeds with the same DCP as the highest protein feed, one with an AMEn:DCP ratio of 59, through the addition of canola oil, and the other with a ratio of 51 MJ/kg supplemented with both starch and oil. Twenty birds constituted each experimental unit, with two replications of each sex being used per dietary treatment.3. Ten birds per sex were sampled at the start of the trial and a further five per pen at the end for carcass analysis. Each carcass including feathers was ground and subsampled for water, protein and lipid determination.4. A split-line regression described ep on the four feeds unsupplemented with additional energy (R2 = 0.81) with breakpoint at 60.6 MJ AME/kg DCP, maximum ep at 0.736 g/g, and a slope of 0.017. No improvement in ep resulted from supplementing the high protein feed with oil or a mixture of oil and starch, but feed intake and protein and lipid retention increased significantly (P < 0.05).5. The argument that insufficient energy is available to enable high protein feeds to be utilised efficiently was not corroborated by the evidence from this trial.

Research Note: The effects of genotype, sex, and feeding regime on performance, carcasses characteristic, and microbiota in chickens.

The aim of the present study was to evaluate the effects of quantitative feed restriction (FR) in fast-, medium-, and slow-growing meat-type male and female chickens on their growth, feed consumption, economic efficiency, carcass composition, and gastrointestinal microbiota. In the experiment, fast-growing Ross 308, medium-growing Hubbard JA 757 and slow-growing ISA Dual chickens of both sexes were exposed to quantitative FR between 14 and 21 d of age. During the FR, restricted chickens received 70% of the amount of feed consumed by the ad libitum (AL) group. Live weight at the end of the experiment was affected by genotype (P < 0.001), sex (P < 0.001), feeding regime (P < 0.001), and their interaction (P < 0.001). The highest final weight was in AL and FR ISA Dual males and the lowest was in AL and FR females of the same genotype. A similar tendency was observed in daily weight gain and feed intake. Carcass traits were predominantly affected by genotype. However, interactions of genotype, sex, and feeding regime were observed in thigh (P < 0.001) and abdominal fat (P < 0.001) proportions. Concerning gastrointestinal microbiota, only Escherichia coli was affected by genotype. Feed restriction in slow-growing dual-purpose chickens might improve economic potential; however, further research is needed to reveal the involvement of variable processes, which are unclear and affect production.

Breast meat quality in males and females of fast-, medium- and slow-growing chickens fed diets of 2 protein levels.

The aim of this study was to evaluate the effects of genotype, sex, dietary protein level, and their interactions on select carcass characteristics and meat quality of fast- (Ross 308), medium- (Hubbard JA757) and slow-growing (ISA Dual) chickens (n = 2,520). The diet of the low-protein group of chickens had 6% lower CP than the commercial diet fed to the control group. When the chickens reached an average live weight of 2 kg, 10 males and 10 females of each genotype and the diet were selected for slaughter and breast meat-quality analysis. The dressing out and breast percentages were lower in the JA757 (-2.0 and -5.9%, respectively) and ISA Dual chickens (-9.9 and -14.3%, respectively) than those in the Ross 308 chickens. The ISA Dual chickens had higher abdominal fat percentage, higher DM and protein contents and lower ether extract content and shear force value in breast meat than the other genotypes. Significant interaction effects of genotype, sex, and diet were found on the color of breast skin. Among the various combinations of genotype, sex, and diet group, Ross 308 females fed the low-protein diet had the highest redness and yellowness of breast skin, highest pH45 value, and largest fibers, whereas ISA Dual females had the lowest color parameters and pH45 value, and ISA Dual males had the smallest muscle fibers. The low-protein diet was associated with decreased abdominal fat percentage and changes in meat quality parameters, including increased darkness, meat color intensity, drip loss, and muscle fiber area, in all genotypes. The results indicated greater differences in meat quality owing to genotype than to sex or dietary protein level.

Changes in the quality of eggs during storage depending on the housing system and the age of hens.

The objective of the study was to evaluate changes during storage time (0, 7, 14, and 21 D) in the weight, albumen quality and its functional properties, and protein content of eggs from enriched cage and free range at 26 and 51 wk of age. Egg weight was affected by a significant interaction between the housing system and the age of hens. Regarding individual factors, heavier eggs (P < 0.001) were obtained with the enriched cage (61.7 g) environment than with free range (59.6 g) environment at 51 wk (P < 0.001) (63.3 g vs. 58.0 g), and freshly laid eggs were heavier compared to eggs stored for 14 and 21 D (P < 0.001). The significant interaction of evaluated factors affecting egg weight loss included the Haugh unit score and pH. Albumen dry matter content was significantly higher in free-range eggs (14.70% vs. 14.0%), in eggs from younger hens (15.0% vs. 13.7%) and in eggs that were stored 21 D. Free-range eggs contained more lysozyme (P < 0.001), and younger hens produced eggs with higher ovotransferrin (P < 0.05) and ovalbumin content (P < 0.01). The data from the study show that the evaluated factors and their interactions significantly affected the physical parameters of the eggs, whereas albumen functional properties and lysozymes, ovalbumin, and ovotransferrin were negligibly affected.

The growth of turkeys 2. Body components and allometric relationships.

1. The relationships between the main components of the body and body protein among males and females of BUT 6 (BUT) and Hybrid Converter (HYB) turkey strains were examined. 2. The weights of breast meat, breast skin, drumstick meat, drumstick skin, thigh meat, thigh skin and wing-plus-skin as well as the head, neck, feet, blood, heart, liver and gizzard were measured at different stages of growth after which all components of each bird were minced together in order to determine the feather-free body protein weight of each bird sampled. Using the weights of the components and the protein content of each bird the allometric relationships between the components and body protein were determined and then compared for each strain x sex combination. 3. By excluding the breast weights at day-old and at 7 d, the remaining points produced an acceptable allometric relationship (R2 = 0.992). Thigh weight could be predicted for all strain x sex combinations using one allometric equation, as could drumstick skin weight. Breast and thigh skin weights differed between males and females. Females of the HYB strain exhibited heavier drumstick and wing-plus-skin weights at a given body protein weight than the other three strain x sex combinations. These differences in both the constant term and regression coefficient in the allometric equations between genotypes are probably due to differences in the amount of lipid that is deposited in these tissues. 4. Sexes differed in the allometric relationships for head, feet, heart and liver, while breeds differed in gizzard weight. A common relationship between the four genotypes could be used to predict the weight of blood in the carcass. 5. The allometric equations fitted to the data in this trial enable the accurate prediction of the weights of the different physical components given the weight of body protein.

The growth of turkeys 1. Growth of the body and feathers and the chemical composition of growth.

1. The potential growth of modern turkey genotypes was measured using male and female BUT 6 (BUT) and Hybrid Converter (HYB) strains. At one-day-old, 720 male and 960 female poults were randomly allocated to 48 littered pens in two houses with 30 males or 40 females of each strain per pen. Five feeds of decreasing protein content were fed to both sexes during the growing period. 2. Birds were weighed at 1, 7, 14, 21, 35, 56, 77, 119 d (males only), 126 d (females only) and 140 d (males only) and, on each occasion, six birds were selected and removed for carcass analysis. 3. Growth was similar in both strains, but the growth rate of females appeared to decline relative to the earlier trajectory after 70 d, and this tendency being greater in HYB females. 4. HYB birds of both sexes had more feathers than BUT to 77 d, but thereafter these differences were non-significant. A single allometry between feather and body protein weight was observed over all genotypes with no differences apparent between sexes within strains. The Gompertz curve adequately described the growth of body protein, water and ash. 5. Body lipid (g/100g bodyweight) declined in the early stages of growth. This might reflect an energy deficiency in the diet or might indicate that the present description of lipid growth does not apply in turkeys as it does in other species. 6. Whereas the description of body growth, feather growth and the chemical components of growth given in this paper may not fully reflect the true potential of the genotypes used, nevertheless they provide useful information regarding the latest genotypes available in the turkey industry. Some of the observations suggested that current performance might be improved if further research is conducted regarding dietary energy transactions.

The relationship between hepatocytes and small bowel after early and short food restriction: What the results show in morphometry.

The objective of this study was to evaluate the relationship between hepatocyte morphometry and small bowel architecture after early and short food restriction. Altogether 48 Hyplus broiler rabbits were divided into three groups. The control group was fed ad libitum (ADL) throughout the experiment (C). The first group were food-restricted between 32 and 39 days of age, when the rabbits received 50g of food per rabbit each day (R1). The second group was restricted between 32 and 39 days and the rabbits received 65g of food per rabbit each day (R2). In 39 and in 81 days eight rabbits from all three groups were euthanized. The diameter of centrilobular, midzonal and periportal hepatocytes and the height of villi, the width of villi and the crypt depth were measured. The hepatocytes grew from centrilobular to perilobular part in the C group, but in the R1 and R2 group, an opposite trend was noticed. On day 39 and daye 81 the elevations of villi were the highest. Interestingly, the nadirs of the crypts were deepest in the C group compared to the R1 and R2 groups. Early short intensive food restriction may play a role in the prevention of liver diseases (Tab. 2, Ref. 20).

The influence of food restriction on the small bowel: Does intensive short­term food restriction lead to weight loss?

The objective of this study was to show morphological changes in the small intestine of Hyplus broiler rabbits following an eight­day food restriction programme. The control group (C) received food ad libitum (ADL) for the duration of the experiment. Group R1 received 50g of food per day, and group R2 received 65g of food per day. After the food restriction diet had been completed, groups R1 and R2 were returned to ad libitum feeding. After food restriction and at the end of the experiment, the longest small bowel measurement was recorded in the C group. In the C group, after food restriction, the villi height was significantly higher, compared to that in R1 and R2 groups and at the end of the experiment, the villi were significantly higher in R1 and R2 groups. After food restriction, the values of crypts depth were approximately similar in all groups, and the end of experiment, the depth of crypts were deepest in R1and R2 groups, as compared to that in C group. The full process is followed by weight loss to the end of the experiment. These data suggest that intensive short­term food restriction followed by ADL feeding has effect on weight loss (Fig. 3, Ref. 30).

Age related changes in laying pattern and egg weight of different laying hen genotypes.

The aim of the study was to evaluate changes in laying patterns depending on the age of different genotypes of laying hens. In the experiment, six genotypes were evaluated (brown-egg hens Bovans Brown, Bovans Sperwer and Isa Sussex, white-egg hens Dekalb White, and laying hens with tinted shells Moravia Barred and Moravia BSL) in three periods during the laying cycle (the onset of lay between 20 and 26 weeks of age, the middle from 36 to 42 weeks of age and the end of lay between 64 and 70 weeks of age). A significant interaction between genotype and age was apparent in mean sequence length (P<0.001), length of the prime sequence (P<0.001), mean number of sequences (P<0.001) and mean time of oviposition (P˂0.001). The longest lag during the course of the experiment was with Moravia BSL, which was more than 3h; the shortest lag was observed in Bovans Brown, which was less than 1h. The mean time of oviposition was also affected by genotype (P˂0.001). Bovans Brown laid their eggs approximately 3.5h after the lights came on, whereas Moravia BSL laid their eggs almost 6h after the lights came on. Egg weight increased with age (P˂0.001), and the smallest differences in egg weight were with ISA Sussex (5g), whereas the biggest differences were with Moravia BSL (10g).

The effect of 1-week feed restriction on performance, digestibility of nutrients and digestive system development in the growing rabbit.

A 3 to 4 week feed restriction of about 20% to 25% of the free intake is widely applied in rabbit breeding systems to reduce post-weaning digestive disorders. However, a short intensive feed restriction is described in few studies and can be beneficial for growing rabbits due to a longer re-alimentation period. The aim of this study was to evaluate the effect of ad libitum (AL) and two restriction levels of feeding (50 and 65 g/rabbit per day) applied for 1 week on performance, gastrointestinal morphology and physiological parameters during the restriction and during the re-alimentation period. Rabbits were divided into three experimental groups: AL rabbits were fed AL, R1 rabbits were restricted from 42 to 49 days of age and received 50 g daily (29% of AL) and R2 rabbits were restricted at the same age and were fed 65 g of feed daily (37% of AL). In the 1(st) week after weaning and in the weeks after restriction, all the groups were fed AL. During the restriction period, daily weight gain (DWG) in R1 significantly dropped to 11% (experiment 1) and 5% (experiment 2) compared with rabbits in the AL group, although they were fed 29% of AL, whereas in the R2 group it decreased to 20% (experiment 1) and 10% (experiment 2). In the week following feed restriction, DWG in the restricted groups increased (P<0.001) to 166% and 148% in R1 and to 128% and 145% in R2. Restricted rabbits in both the experiments reached up to 90% to 93% of the final live weight (70 days) of the AL group. Over the entire experimental period, feed restriction significantly decreased feed intake to 85% to 88% of the AL group; however, the feed conversion ratio was lower (P<0.05) only in experiment 1 (-6% in R1 and -4% in R2). Digestibilities of CP and fat were not significantly higher during the restriction period and during the 1(st) week of re-alimentation compared with the AL group. Significant interactions between feeding regime and age revealed the shortest large intestine in the AL group at 49 days of age and the longest at 70 days in the AL and R1 groups. Small intestinal villi were significantly higher and the crypts were significantly deeper in the restricted groups. It could be concluded that short intensive feed restriction increased digestible area in the small and large intestines, including the height of villi and depth of crypts, which might be involved in the compensatory growth and defence mechanism.

Genetic and morphological characterization of Trichuris myocastoris found in Myocastor coypus in the Czech Republic.

Trichuris sp. individuals were collected from Myocastor coypus from fancy breeder farms in the Czech Republic. Using morphological and biometrical methods, 30 female and 30 male nematodes were identified as Trichuris myocastoris. This paper presents the first molecular description of this species. The ribosomal DNA (rDNA) region, consisting of internal transcribed spacer (ITS)-1, 5.8 gene and ITS-2, was sequenced. Based on an analysis of 651 bp, T. myocastoris was found to be different from any other Trichuris species for which published sequencing of the ITS region is available. The phylogenetic relationships were estimated using the maximum parsimony methods and Bayesian analyses. T. myocastoris was found to be significantly closely related to Trichuris of rodents than those of ruminants.

Interaction of hen production type, age, and temperature on laying pattern and egg quality.

The effect of production type (layer vs. broiler breeder), age (onset and end of laying cycle), and temperature (20 and 28°C) on various aspects of the egg production process and quality was evaluated. Highly significant differences were detected between laying hens and broiler breeders (P ≤ 0.001) in all production parameters. Similarly, age significantly affected rate of lay (P ≤ 0.001; 75.4% for young vs. 62.6% for old), mean sequence length (P ≤ 0.001; 7.7 d for young vs. 2.6 d for old), and time of oviposition (P ≤ 0.001). However, there was no effect of temperature on rate of lay, sequence length, or feed intake. Significant interactions between hen type and age were apparent in rate of lay (P ≤ 0.001), sequence length (P ≤ 0.001), and time of oviposition (P ≤ 0.001). A significant interaction between production type and age (P ≤ 0.015) was evident in egg weight, but egg component proportions were dependent only on hen type. Egg shape index was significantly affected by age (P ≤ 0.004), by temperature (P ≤ 0.028), and an interaction between type and age (P ≤ 0.001). Specific gravity declined with age (P ≤ 0.035) and increasing temperature (P ≤ 0.013).

Cerebrolysin inhibits lipid peroxidation induced by insulin hypoglycemia in the brain and heart of mice.

As a consequence of enhanced production of oxygen free radicals, lipid peroxidation leads to the degradation of membrane lipids and disturbances of membrane permeability. Lipid peroxidation increases under stress conditions such as hypoxia, ischemia or acidosis as well as in metabolic diseases, e.g. diabetes mellitus. We have shown that subcomatous doses of insulin (6.0 IU/kg) significantly increase thiobarbituric acid reactive substances (TBARs), especially malondialdehyde (MDA) - the endproduct of lipid peroxidation, in the brain and heart of mice. In our model of insulin-induced hypoglycemia, mice were treated with the neuroprotective, peptide-containing drug Cerebrolysin (100 mg/kg b.w.). Animals were sacrificed by decapitation two or three hours after the injection of tested substance and samples were taken to determine several serum parameters (glucose, total protein, triglycerides and lactic acid) and TBARs in the brain and heart. Although Cerebrolysin was not able to affect serum parameters after subcomatous insulin injection, the drug significantly influenced lipid peroxidation. A single injection of Cerebrolysin already decreased TBARs levels in the brain and heart tissue. Presuming that an increase of TBARs reflects disturbances of the cell membrane, we have documented a promising effect of Cerebrolysin on cell integrity.

Oxidative stress in the brain tissue of laboratory mice with acute post insulin hypoglycemia.

Malondialdehyde (MDA), Cu,Zn-superoxide dismutase (Cu,Zn-SOD) and selenium-dependent glutathione peroxidase (GSPHx) are currently considered to be basic markers of oxidative stress. MDA is one of the end-products of the peroxidation of membrane lipids, whereas enzymes Cu,Zn-SOD and GSHPx belong to the natural antioxidants. The role of oxygen free radicals in the pathogenesis of many diseases is well documented. The aim of this study was to ascertain the influence of insulin-induced acute hypoglycemia on oxidative stress in the brain tissue. Hypoglycemia was induced in ICR mice by intraperitoneal administration of insulin at a dose 24 IU/kg. There was a correlation between the severity of hypoglycemia and the levels of MDA, Cu,Zn-SOD and GSHPx. The results showed that in severe hypoglycemia (serum glucose concentration below 1.0 mmol/l) the lipoperoxidation in brain tissue expressed as the level of MDA was higher in comparison with normoglycemic controls (glycemia around 3.7 mmol/l) as well as in comparison with the levels of MDA during moderate hypoglycemia (glycemia ranging between 1-2 mmol/l). This indicates the enhancement of lipoperoxidation in the brain tissue during severe hypoglycemia. However, both enzymes - Cu,Zn-SOD or GSHPx - did not show a similar tendency.

Performance and oocyst shedding in broiler chickens orally infected with Cryptosporidium baileyi and Cryptosporidium meleagridis.

To study effects of experimental cryptosporidiosis, broiler chickens were infected per os with 5 x 10(5) oocysts of Cryptosporidium baileyi and Cryptosporidium meleagridis. In the first experiment, chickens were infected with oocysts of C. baileyi at the age of 7, 14, and 21 days. In the second experiment, chickens were infected with oocysts of C. baileyi, C. meleagridis, or both cryptosporidial species at the age of 7 days. Although clinical signs of infection were apparent, neither final live weight nor mortality was significanty influenced in chickens infected with a single Cryptosporidium species. In chickens infected with C. meleagridis, the growth retardation was observed in the 2-wk period after infection. The compensatory growth, however, started when the oocyst shedding had ceased. The number of oocysts in excreta specimens of chickens infected with C. meleagridis was two to three times lower than in excreta of chickens infected with C. baileyi. Chickens infected with both C. baileyi and C. meleagridis (5 x 10(5) oocysts of each) had significantly lower final live weight and worse feed efficiency than chickens of other groups. Concurrent infection did not influence individual C. baileyi or C. meleagridis oocyst shedding.

Influence of dietary fat source and copper supplementation on broiler performance, fatty acid profile of meat and depot fat, and on cholesterol content in meat.

1. Three hundred and twenty d-old chickens were fed on a wheat/maize-soyabean meal diet supplemented with (i) 50 g/kg lard, (ii) 25 g/kg lard and 25 g/kg rapeseed oil, (iii) 50 g/kg rapeseed oil, and (iv) 50 g/kg rapeseed oil and 200 mg copper per kg as copper sulphate pentahydrate. 2. Final weights at 39 d of age in chickens receiving rapeseed oil were lower by 9% than in those fed on the diet containing only lard (P<0.05). The fatty acids profiles of lipids extracted from the tissues of 10 chickens per group reflected those of the diets. 3. The polyunsaturated fatty acid (PUFA) content of breast muscles and abdominal fat (expressed as a percentage of total fatty acids) was increased and the ratio of n-6:n-3 fatty acids was decreased by the substitution of lard by rapeseed oil (P<0.001). These changes were more pronounced for the adipose tissue than for breast muscles. 4. Copper sulphate supplementation increased the final body weight of chickens by 4.3% (P<0.05), reduced the saturated fatty acid (SFA) proportion (P<0.05) in abdominal fat and increased the PUFA:SFA ratio (P<0.05). The magnitude of improvement, however, was small. 5. The substitution of rapeseed oil for lard decreased the concentration of cholesterol in breast muscles by 13%. Copper supplementation further reduced the cholesterol content by 25%. Both effects were significant (P<0.001).

[Spontaneous Cryptosporidium infection in weaned rabbits]. / Spontánní kryptosporidiová nákaza u odstavených králícat.

The first occurrence of Cryptosporidium parvum Tyzzer, 1912 in broiler rabbits in the Czech Republic is reported. The protozoon was determined on the basis of morphometrical parameters of oocysts and of localization of endogenous developmental stages. The dynamics of natural Cryptosporidium infection was studied in a group of 72 young rabbits after weaning (their age ranging from 23-33 to 82-92 days) obtained from six large flocks and used in a feeding experiment. C. parvum was found in rabbits from four farms (Tab. I). Animals under observation were divided into 9 subgroups according to the genotype (Hyla 2000, California White, crosses of New Zealand x California, New Zealand White, Cunistar and Zika) as well as according to the farm of origin. The animals were housed in 28 cages under the conditions of two-floor cage technology. The upper floor consisted of cages housing three head, the lower floor two head each. The animals were fed ad libitum with commercial feed mixture (till the average age of 64.days supplemented with Robenidin as coccidiostat). During the first 10 days of observation pooled samples of droppings from each cage were examinated by flotation-centrifugation method according to Breza (1957) and Pavlásek (1991) in the intervals of three to four days, later one-week intervals. Post mortem scrapings from mucous epithelium taken from young rabbits were examinated (to reveal endogenous developmental stages of C. parvum) together with digesta (to detect oocysts of the protozoon) taken from the full length of the small intestine using method of native preparations and Giemsa stain. In one 37-day dead animal the small and large intestines were examined histologically. The maximum number of young rabbits infected with C. parvum were 30-40 and 33-43 days old (Fig. 1). In animals of this age category the oocysts of the protozoon were found in pooled samples in 11 and 12 cages (39.3 and 42.9%) from totally 28 cages under study. In rabbits of more than 50 days of age the occurrence of infection was significantly decreased (3.7%). During the experiment seven rabbits (9.7%) died; six of them (8.3%) at the age of 30-40 days. All these naturally infected and dead animals represented cases of monoinfection with C. parvum. The major clinical signs were typical diarrhoea lasting 3-5 days, inappetency, apathia, lethargy, prominent signs of exhaustion followed by dehydration of the organism. Atrophy of villi of the ileum in one of young rabbits was found histologically. Table II presents concrete data on significantly lower body weights (the decrease being 7-61.5%) as compared with rabbits of the same age not infected with cryptosporidia. It was not possible to evaluate objectively the differences in susceptibility to C. parvum infection between the individual genotypes of rabbits. As was found in the course of our further studies (unpublished data) a possible source of infection of young rabbits can be represented by their mothers in which oocysts are excreted sporadically shortly before parturition and during several days after it. Cryptosporidium infection (cryptosporidiosis) in flocks of broiler rabbits is taken as a new protozoal disease in the Czech Republic and C. parvum as one of possible agents in cases of disorders of digestive tract, namely in rabbits after weaning.