Effects of rumen-protected choline supplementation on milk production and choline supply of periparturient dairy cows.

The objective of the present study was to determine the effects of rumen-protected choline (RPC) supplementation on body condition, milk production and milk choline content during the periparturient period. Thirty-two Holstein cows were allocated into two groups (RPC group - with RPC supplementation, and control group - without RPC supplementation) 28 days before the expected calving. Cows were fed the experimental diet from 21 days before expected calving until 60 days of lactation. The daily diet of the RPC group contained 100 g of RPC from 21 days before calving until calving and 200 g RPC after calving for 60 days of lactation, which provided 25 g and 50 g per day choline, respectively. Body condition was scored on days -21, 7, 35 and 60 relative to calving. Milk production was measured at every milking; milk fat, protein and choline content were determined on days 7, 35 and 60 of lactation. Body condition was not affected by RPC supplementation. Milk yield was 4.4 kg higher for the group of cows receiving supplementary choline during the 60 days experimental period and 4% fat-corrected milk production was also increased by 2.5 kg/day. Milk fat content was not altered by treatment, but fat yield was increased by 0.10 kg/day as a consequence of higher milk yield in the RPC-treated group. Milk protein content tended to increase by RPC supplementation and a 0.18 kg/day significant improvement of protein yield was detected. Milk choline content increased in both groups after calving as the lactating period advanced. However, milk choline content and choline yield were significantly higher in the RPC group than in the control group. The improved milk choline and choline yield provide evidence that some of the applied RPC escaped ruminal degradation, was absorbed from the small intestine and improved the choline supply of the cows and contributed to the changes of production variables.

Effect of supplementation with methionine and different fat sources on the glutathione redox system of growing chickens.

The effect of supplementary methionine and fats of different saturation levels on the glutathione redox system of growing broiler cockerels was studied. The diet of three groups of chicks was supplemented with corn germ oil, beef tallow and fish oil at the levels of 30 g/kg and 50 g/kg of feed, respectively. The diet of further three groups was supplemented with methionine (5 g/kg of feed) in addition to the different fat sources. Control chicks were fed with a compound feed without methionine and fat supplementation. Reduced glutathione (GSH) and glutathione disulphide (GSSG) content as well as glutathione peroxidase activity in the liver were determined and GSH/GSSG ratio was calculated at day old and then at one and three weeks of age. Our results indicate that supplementary methionine stimulates both the synthesis of the glutathione redox system and glutathione peroxidase activity in growing chickens in the first period of postnatal life, when the risk of lipid peroxidation is high due to feeding unsaturated fats in the diet.

Effects of saturated and unsaturated fats with vitamin E supplementation on the antioxidant status of broiler chicken tissues.

The influence of fish oil (highly unsaturated) and beef tallow (highly saturated) with vitamin E (100 IU/kg) supplementation on the antioxidant status of broiler chicken cockerels was investigated. Chicks were fed a control diet with no added fat, 40 g/kg each of fish oil and beef tallow diets, respectively, from 11 to 42 days of age. Tocopherol concentration and the rate of lipid peroxidation, thiobarbituric acid reactive substance (TBARS) in liver, fatty acid composition of the liver lipids, blood serum total antioxidant status (TAS), and reduced glutathione (GSH) content were determined. Vitamin E supplementation of the diet increased liver alpha-tocopherol content in chicks regardless of the type of dietary fat. Fish oil diet resulted in higher liver TBARS value while beef tallow diet showed lower values compared to the control diet. Vitamin E supplementation reduced liver TBARS as well as serum GSH, and raised serum TAS for all diets. Serum GSH was the same for vitamin E supplemented diets regardless of the fat supplement. Fish oil diets resulted in a significant increase in hepatic lipid n-3 PUFA content. A significant positive correlation was found between liver TBARS and n-3 PUFA content. No relationships were established, however, between liver TBARS and n-6 PUFA or saturated fatty acids. The results suggest that feeding oils rich in n-3 PUFA increases tissue concentration of these fatty acids, consequently increasing tissue lipid peroxidation and reducing the antioxidative status of broiler chickens. Supplementing high levels of vitamin E with such oils may increase tissue oxidative stability. Serum TAS or GSH may be used as a measure of antioxidative status in chickens.

Nutritional metabolic diseases of poultry and disorders of the biological antioxidant defence system.

Deficiencies or disturbances of nutrition cause a variety of diseases and can arise in different ways. The amount of a particular nutrient in the diet may be insufficient to meet the requirements, the diet may contain substances that inactivate the nutrient or inhibit its absorption/utilisation, or metabolism may be upset by the interaction of dietary and environmental factors. Peroxidation of lipids or oxygen free radical generation in general is a physiological process important for cell metabolism, division and differentiation and also for the biosynthesis of hormones and prostaglandins. Free radicals generated through these processes are effectively scavenged by the antioxidant defence system. Uncontrolled lipid oxidation caused by disturbances of that system may play a crucial role in some important poultry diseases and toxicoses. The first route of lipid peroxide loading of the organism is via the feed, such as through oxidised lipids. Oxidised fatty acids are absorbed from the intestine mainly in the form of unsaturated keto compounds and initiate lipid peroxidation in the tissues. The second problem is the insufficient amount of antioxidants in the feed, e.g. vitamin E deficiency. Nutritional encephalomalacia is a problem in poultry production which depends both on the actual vitamin E supply and the dietary amount of polyunsaturated fatty acids. In young birds the primary target of vitamin E deficiency is the brain because it contains low amounts of vitamin E, and the vitamin E content of the liver acting as store decreases rapidly during the first week of life. Besides vitamin E, other components of the antioxidant system, e.g. the antioxidant enzymes (catalase and glutathione peroxidase) also have low activity in the brain as compared to other major tissues. The brain is highly susceptible to oxidative stress because of the accumulation of polyunsaturated fatty acids. The third source of free radical generation is the toxic level of different feed ingredients, e.g. toxicoses caused by vitamin A, selenium, and ionophore antibiotics. Other important aspects of antioxidants (e.g. vitamin E and selenium) in poultry are stimulation of the immune response (e.g. in the case of vaccination) and reduction of the risks of free radical formation as a result of macrophage function.

Effect of bulk feeds (alfalfa hay, corn silage) on the metabolism and liver parameters of growing geese.

Rearing experiments were conducted with a total of 90 liver hybrid geese from Babat, divided into three groups of 30 birds each. The effect exerted by all-concentrate feeding (group 1), concentrate feeding supplemented with alfalfa hay (group 2) or with corn silage (group 3) ad libitum on the blood glucose level, blood plasma total lipid, total cholesterol and free fatty acid level, and on total lipid content of the liver was studied. In addition, aspartate aminotransferase (AST) activity of the blood plasma and carotene, vitamin A and vitamin E concentration of the blood plasma and the liver were determined. It was found that the blood and liver parameters of goose groups fed different diets changed within the physiological limits typical of the species. Excessive fibre intake resulted in reduced lipid transport within the organism at an unchanged plasma cholesterol level; at the same time, blood glucose level remained unchanged. Ad libitum feeding of alfalfa hay and corn silage enhanced carotene and vitamin A transport and carotene storage but did not affect the transport of vitamin E. The results confirm earlier data of the literature that beta-carotene and vitamin A together impair vitamin E metabolism.