Theo Wensing

Relationship between overfeeding and overconditioning in the dry period and the problems of high producing dairy cows during the postparturient period.

In dairy cows, overfeeding during the dry period leads to overcondition at calving and to depression of appetite after calving. As a consequence, at calving overconditioned high-producing dairy cows inevitably go into a more severe negative energy balance (NEB) postpartum than cows that have a normal appetite. During the period of NEB, the energy requirements of the cow are satisfied by lipolysis and proteolysis. Lipolysis results in an increased concentration of non esterified fatty acids (NEFA) in the blood. In the liver, these NEFA are predominantly esterified to triacylglycerols (TAG) that are secreted in very low density lipoproteins (VLDL). In early lactation in cows with a severe NEB, the capacity of the liver to maintain the export of the TAG in the form of VLDL in balance with the hepatic TAG production is not always adequate. As a result, the excess amount of TAG accumulates in the liver, leading to fatty infiltration of the liver (hepatic lipidosis or fatty liver). The NEB and/or fatty liver postpartum are frequently associated with postparturient problems. In general, a severe NEB induces changes in biochemical, endocrinological, and metabolic pathways that are responsible for production, maintenance of health, and reproduction of the postparturient dairy cow. These changes include a decrease in blood glucose and insulin concentrations, and an increase in blood NEFA concentrations. High NEFA concentrations caused by intensive lipolysis are accompanied by impairment of the immune system, making the cows more vulnerable to infections. Metabolic diseases such as ketosis, milk fever, and displaced abomasum are related to overcondition at calving. The changes in biochemical, endocrinological, and metabolic pathways are associated with delay of the first visible signs of oestrus, an increase in the interval from calving to first ovulation, a decrease in conception rate, and a prolonged calving interval. It is possible that the increased blood NEFA concentration directly impairs ovarian function.

Activities of the enzymes of hepatic gluconeogenesis in periparturient dairy cows with induced fatty liver.

The objective was to measure the activities of all the enzymes essential for hepatic gluconeogenesis in dairy cows with induced fatty liver. We aimed to induce severe fatty liver in ten experimental cows by overfeeding them during the dry period while seven control cows were maintained on a restricted diet. To induce a marked negative energy balance, the experimental cows were deprived of feed for 8 h immediately after parturition. In addition, the experimental cows were given a restricted amount of diet during the first 5 d of lactation. Liver samples were collected 1 week before and 1, 2 and 4 weeks after parturition. Before parturition, liver triacylglycerol concentrations did not differ between the two groups. After parturition, the experimental cows developed marked fatty liver as indicated by a higher level of triacylglycerols in the liver compared with the control cows. Before parturition, all gluconeogenic enzymes in the liver were lower in experimental cows than in control cows. Phosphoenolpyruvate carboxykinase, pyruvate carboxylase and propionyl-CoA carboxylase were significantly lower and fructose 1,6-bisphosphatase and glucose 6-phosphatase tended to be lower in the experimental cows. The activities of two crucial enzymes for gluconeogenesis in ruminants, i.e., phosphoenolpyruvate carboxykinase and propionyl-CoA carboxylase, remained low throughout the sampling period post partum. Activities of pyruvate carboxylase and glucose 6-phosphatase in the experimental cows post partum were upgraded to values similar to those of the control cows. The results showed that the capacity for hepatic gluconeogenesis before parturition was lower in cows with induced fatty liver than in control cows. After parturition, the low activities of crucial gluconeogenic enzymes indicated insufficient production of glucose. It is suggested that the low gluconeogenic capacity leads successively to low blood glucose concentrations, low insulin levels and high rates of mobilization of fatty acid, causing severe hepatic lipidosis.

Studies on hepatic lipidosis and coinciding health and fertility problems of high-producing dairy cows using the Utrecht fatty liver model of dairy cows . A review

Summary Fatty liver or hepatic lipidosis is a major metabolic disorder of high‐producing dairy cows that occurs rather frequently in early lactation and is associated with decreased health, production and fertility. A background section of the review explores reasons why high‐producing dairy cows are prone to develop fatty liver post partum. Hepatic lipidosis and coinciding health and fertility problems seriously endanger profitability and longevity of the dairy cow. Results from a great number of earlier epidemi‐ological and clinical studies made it clear that a different approach was needed for elucidation of pathogenesis and etiology of this complex of health problems. There was a need for an adequate animal model in which hepatic lipidosis and production, health and fertility problems could be provoked under controlled conditions. It was hypothesized that overconditioning ante partum and feed restriction post partum might induce lipolysis in adipose tissue and triacylglycerol accumulation in the liver following calving. This consideration formed the basis for the experiments, which resulted in the “Utrecht fatty liver model of dairy cows”. In this model, post partum triacylglycerol‐lipidosis as well as the whole complex of health and fertility problems are induced under well‐controlled conditions. The experimental protocol based on this hypothesis produced in all cases (10 feeding trials with over 150 dairy cattle) the intended result, i.e. all experimental cows developed post partum higher hepatic triacylglycerol concentrations than did control cows. The model was evaluated in biochemical, clinical pathology, immunological, clinical and fertility terms. It turned out that in this model, post partum triacylglycerol‐lipidosis as well as the whole complex of health and fertility problems were induced under well‐controlled conditions.

Nutritional status of wild boar (Sus scrofa): II. Body fat reserves in relation to haematology and blood chemistry.

1. The relationship between body fat reserves and blood variables was calculated in 26 wild boar in order to evaluate blood variables as indicators for the nutritional status. 2. In juveniles only a relationship between bone marrow fat and haemoglobin, packed cell volume, albumin, total globulin, gamma globulin, alkaline phosphatase and urea were found. 3. Urea and packed cell volume accounted (together) for more than 90% of the variance of bone marrow fat.

Mechanism explaining why dietary soya protein vs. skim-milk protein lowers fat digestion in veal calves

Abstract The hypothesis was tested that, in veal calves, dietary soya protein vs. skim-milk protein withdraws bile acids from the process of fat digestion in the intestine, leading to enhanced faecal excretion of bile acids and reduced fat digestibility. Veal calves were fed control milk replacers containing milk proteins or test milk replacers containing soybean protein. The finisher control diet contained milk protein only, of which 64% was casein. The finisher test diet contained milk proteins, but not casein, and also a soya protein preparation, the preparation comprising 50% of total protein. After 26 weeks of feeding the milk replacers, body-weight gain was on average 3 kg lower in the calves fed soya protein, however this lowered body-weight gain did not reach statistical significance. Faeces were collected during week 15 of the trial. The test diet with soya protein vs. the control diet with skim-milk protein significantly reduced fat digestibility from 89.8 to 86.7% of intake. The feeding of soya protein produced an almost three-fold rise in bile acid excretion. Phosphate and calcium absorption were significantly reduced by the feeding of the diet with soya protein instead of that with skim-milk protein. In the light of earlier work in rabbits, it is proposed that in veal calves the feeding of soya protein, because of its negligible degree of phosphorylation, raises the amount of insoluble calcium phosphate in the intestine lumen. As a result, more bile acids are bound so that less bile acids are available for fat digestion and reabsorption of bile acids is depressed. This study may be useful in attempts to improve the nutritional value of milk replacers containing soya protein preparations.

The effect of Trypanosoma vivax infection on energy and nitrogen metabolism, and serum metabolites and hormones in West African Dwarf Goats at different feed intake levels.

Effects of Trypanosoma vivax infection on nitrogen and energy metabolism and serum hormones and metabolites were measured using 24 castrated West African Dwarf bucks. In order to discriminate between the effect of infection and the effect of food intake level on energy and nitrogen balance, food quantity restriction was applied for isonutritional comparison; a number of the animals were not infected and served as controls. Daily dry-matter (DM) intake was measured, and energy and nitrogen balance for a 7-day period in weeks 2, 4 and 6 after infection. Weekly blood sampling for analysis of hormones and metabolites was carried out. Infected animals had a lower DM intake, compared with control animals, viz. 38·6 (s.e. 3·2) and 16·1 (s.e. 2·0) g/kg M 0·75 per day, respectively ( P Metabolizability was not changed by infection and averaged 0·44. Heat production was increased by infection with an average of 33 kJ/kg M 0·75 per day. Energy and nitrogen retention were negative for all groups; infection reduced energy retention and, during week 2 and 4 after infection, also nitrogen retention. The required metabolizable energy (ME) intake for maintenance was increased in infected animals (406 and 335 kJ/kg M 0·75 per day for infected and control goats respectively), based on linear regression of energy retention on ME intake. The efficiency with which energy mobilization from body stores was substituted by dietary ME was estimated at 0·809 for both infected and control animals. The relationship between nitrogen retention and energy retention was not changed by infection. Therefore no indications were found for an increased catabolism of protein due to infection. Serum thyroxine and triiodothyronine were reduced by infection; serum metabolites and insulin levels reflected the negative energy balance in infected animals.

The effect of undernutrition on haematological and serum biochemical variables in wild boar (Sus scrofa)

The effect of induced long term undernutrition on the blood composition of wild boar was studied. During the first weeks, the activity of plasma alkaline phosphatase decreased, while creatinine concentrations increased, and the ratio urea/creatinine decreased, suggesting a renal mechanism as well as recycling of nitrogenous waste products to conserve nitrogen. During the last weeks, haemoglobin and packed cell volume decreased, suggesting protein or mineral deficiencies, and the ratio urea/creatinine increased, indicating substantial endogenous protein catabolism.

The effect of the quality of roughage on the course of Trypanosoma vivax infection in West African Dwarf goats:: II. Metabolic profile, packed cell volume, and pathology of disease

Abstract Effects of trypanosome infection and feed quality on the metabolism of trypanotolerant West African Dwarf goats were measured. Goats were allotted to either a diet of lucerne pellets (Crude protein level=172 g/kg DM; n=14) or a diet of chopped grass straw (Crude protein level=68 g/kg DM; n=15). Five animals per feed group served as controls, and the other animals were infected with Trypanosoma vivax parasites. Before and after infection, blood samples were taken weekly, and analyzed for packed cell volume and parasitaemia, and for serum metabolites and hormone concentrations. Six weeks after infection, the goats were killed and post mortem analysis was carried out to study the pathology of disease. Infected animals showed reduced feed intake, increased plasma nonesterified fatty acids concentration, and decreased serum insulin concentration. Liver triacylglycerol concentration was increased in all grass straw fed animals, and some infected goats fed the lucerne feed. Infection drastically reduced serum concentration of thyroxine and triiodothyronine. Infection caused an increased weight of the liver and prescapular lymph nodes in animals from both feed treatments, but lymph nodes were more enlarged in infected animals fed lucerne. Pathological findings were typical for T. vivax infection in goats, irrespective of feed type. Packed cell volume was reduced by infection in both feed groups to values below 20 percentage points. Serum γ-globulin concentration was increased more in infected animals, fed lucerne than those fed grass straw. It was concluded, that by maintaining a feed with a higher protein level, the nutritional status of infected West African Dwarf goats was improved. This was reflected in the serum concentrations of some metabolites and hormones. However, in general, no indications of an interaction between infection and feed type with respect to nutritional status were found. Differences in feed quality did not change the nature and severity of pathological variables, measured at autopsy after 6 weeks of infection.

Apparent fat digestibility in rats fed different diets is negatively correlated with faecal bile acid excretion.

Seventy-two rats were fed one out of 9 diets differing as to protein source and calcium concentration. For the individual rats apparent fat digestibility and faecal bile acid excretion were negatively correlated. It is suggested that a high solubility of bile acids in the small intestinal digesta, which is associated with little loss of bile acids with faeces, stimulates the process of fat digestion.

The effect of previous growth retardation on energy and nitrogen metabolism of goats infected with Trypanosoma vivax

The effect of growth retardation, resulting from feed restriction for a prolonged period, on the course of infection with Trypanosoma vivax was studied. Twelve male castrated West Africa Dwarf goats were subjected to a restricted feeding reghen of 55 g pelleted lucerne ( Medicago safiva )/kg body weight 0·75 per d for on average 17 weeks. Twelve other animals were fed on pelleted lucerne ad libitum , resulting in a normal growth pattern. After this period, all animals were fed on pelleted lucerne ad libitum , and six animatn of each previous feeding regimen treatment were infected with Trypanosoma viva . The other animals served as controls. In week 2 and 4 post infection ( pi ) energy and N balaoces were measured. In the week before infection and daring infection blood biochemical and clinlcal variables were measured. At 2 weeks before, and 4 weeks after infection, a liver biopsy was taken for measurement of triacylglycerol. Iofection caused intermittent fever and anaemia. The first peak of fever persisted longer in iofected anlmaln with normal growth than in infected animals with retarded growth. Gross energy and metabolizable energy intake, and energy retention were reduced ininfected animals. Metabolizable energy requirements for mainteoaoce were increased by infection. Plasma non-esterified fatty acids (NEFA) and glucose concentratioos were increased in infected animals, whereas serum triiodothyronine and thyroxine coocentratioos were decreased.Plasma urea concentration and liver triacylglycerol were uoaffected. No interaction of growth retardation with infection with respect to blood biochemical variables was found, apart from plasma NEFA in week 2 pi . N retention was not significantly affected by treatments. In conclusion, minor indications were found for an interaction between growth retardation, as applied in the present study, and trypaommiasis infection in West Africao Dwarf goats with respect to energy and N metabolism.