Christian Friis Børsting

Reducing nitrogen surplus from dairy farms. Effects of feeding and management

The objective of the present paper is to review the factors which can affect N flow and surplus both at farm and at cow level in order to point out areas with scope for future improvement. Special attention is given to management factors and feeding. Besides information from the literature the paper is based on meta-analyses of our own and published results. With regard to effects of production systems, mainly Danish surveys have been chosen as examples demonstrating the effects obtained under practical conditions. A positive correlation between stocking rate and N surplus per hectare at farm gate level is demonstrated, but there is also a considerable variation in N surplus per hectare at a given stocking rate. A number of factors influencing N surplus and loss have been identified, and their impact on N surplus and production efficiency has been estimated. N excretion per animal is an important factor for N turnover at farm level. Analysis of herd data indicates that feeding strategy, breed and milk yield, together with energy conversion and the protein content of the diet, are important factors explaining N excretion and N efficiency of cows. Reduction of N intake by optimal synchronisation of energy and protein supply over time, especially in pasture-based systems, is one way of reducing N excretion from cows. Furthermore, the ideal profile of absorbed amino acids should be identified, and models to estimate amino acid supply to the intestine should be further improved. The effect of reducing N excretion from cows has to be evaluated at farm level as manure is used as fertiliser for crop production. Overall, it seems possible to reduce the N surplus through better management and feeding without reducing production efficiency.

Digestibility of Fatty Acids in the Gastrointestinal Tract of Dairy Cows Fed with Tallow or Saturated Fats Rich in Stearic Acid or Palmitic Acid

Abstract Fatty acid digestibility was studied with five lactating cows fed three different fat sources in a 5 × 5 latin square experiment. The treatments were 500 g of tallow, 500 or 1000 g of saturated fat rich in stearic acid (C18:0) (SARF) or 500 or 1000 g of saturated fat rich in palmitic acid (C16:0) (PARF) per day. The total daily fatty acid intake was about 1100 g in rations with the highest fat inclusion. The fatty acid digestibilities were 76% for tallow, 74 and 64% for 500 and 1000 g SARF, respectively, and 87 and 81% for 500 and 1000 g of PARF, respectively. When compared to fatty acid digestibility for tallow predicted from a model based on literature values, PARF had a higher fatty acid digestibility at both fat intakes, and SARF had a lower fatty acid digestibility, especially at high fat intake.

Fatty Acid Digestibility in Lactating Cows Fed Increasing Amounts of Protected Vegetable Oil, Fish Oil or Saturated Fat

Abstract Fatty acid digestion was studied in three dairy cows cannulated in the rumen, duodenum and ileum. Cows were fed encapsulated fat sources (vegetable oil, saturated fat and fish oil). A preperiod diet was fed with no added fat. In a graeco-latin design nine diets comprising three levels of each of the three fat sources were fed. The preperiod diet contained 230 g fatty acids (FA), whereas the three other fats were fed at about 550, 850 and 1150 g FA/day. The feed-ileum true digestibility of total FA was 95, 47 and 86% for vegetable, saturated and fish fat, respectively. The true digestibility of FA was for all fat sources independent of fat level. The FA digestibility of C16:0 was higher than that of C18:0. The experiment supports the theory that unsaturated FA has a synergistic effect on the digestibility of saturated FA. Bile acid secretion was estimated to be 282–550 g/day, with the lowest secretion for fish fat diets. Secretion was independent of the amount of fat fed.

The Influence of Tallow on Rumen Metabolism, Microbial Biomass Synthesis and Fatty Acid Composition of Bacteria and Protozoa

Abstract Rumen metabolism, microbial biomass synthesis and microbial long chain fatty acid composition were studied in lactating cows fed at two levels of dry matter intake (L, 8.6 kg DM and H, 12.6 kg DM) with 0, 4 and 6% added tallow at the low feed level (L0, L4 and L6) and 0, 2, 4 and 6% at the high feed level (H0, H2, H4 and H6). Fibre digestibility was not significantly affected by tallow addition. Increasing tallow level in the diet decreased the total VFA concentration, the ratio of acetic acid to propionic acid and the ammonia concentration in the rumen. Crude fat and fatty acid content in bacterial and protozoal dry matter increased with increased tallow level, especially due to an increase in fatty acids originating from the feeds. Microbial synthesis in the rumen and flow of amino acids to the duodenum was highest for medium fat intake at the high feed level.

Fatty Acid Metabolism in the Digestive Tract of Lactating Cows Fed Tallow in Increasing Amounts at Two Feed Levels

Abstract Long-chain fatty acid metabolism in the digestive tract was studied in lactating cows fed at two levels of dry matter intake (L, 8.6 kg DM and H, 12.6 kg DM), with 0, 4 and 6% added tallow at low feed level (L0, L4 and L6), and 0, 2, 4 and 6% fat at high feed level (H0, H2, H4 and H6). Mean fatty acid balance from mouth to duodenum was about zero when corrected for endogenous fatty acids from bile. However, regression analysis showed a microbial synthesis of 68 g at zero fatty acid intake, and a trend which indicated declining de novo synthesis of fatty acids with increasing fat level in the diet. As a mean 68% of the unsaturated C18 fatty acids were hydrogenated in the rumen. Fatty acid and crude fat true digestibilities decreased with increasing fat intakes owing to a decrease in stearic acid (C18:0) digestibility.

Quantitative Glucose Metabolism in Lactating Mink ( Mustela vison ) - Effects of Dietary Levels of Protein, Fat and Carbohydrates

Glucose metabolism was measured during two consecutive years, 4 weeks postpartum, in a total of 36 yearling female mink, fitted with jugular vein catheters and raising litters of six to seven kits. The dams were fed ad libitum from parturition on diets with different ratios of metabolizable energy (ME) derived from protein:fat:carbohydrates (experiment 1: 61:37:2, 46:37:17, 31:37:32; experiment 2: 61:38:1, 47:52:1, 33:66:1). After 3 h fasting the dams were fed 210 kJ ME of the experimental diets. Two hours postprandially a single dose of 50 w Ci U- 14 C- and 2- 3 H-labelled glucose was administered to each dam and blood samples were drawn 5, 10, 20, 30, 45 and 60 min after the tracer administration. Glucose turnover rates were 4-5% min -1 in all dams, and the approximate daily glucose flux was 12-17 g day -1 ; however, these were not significantly affected by dietary treatment. In conclusion, the mink is able both to synthesize large amounts of glucose de novo and to utilize high levels of dietary digestible carbohydrates, and thereby to tolerate large variations in dietary carbohydrate supply.

Effects of variations in dietary protein levels on hair growth and pelt quality in mink (Mustela vison).

The effect of different and shifting dietary protein levels on hair growth and the resulting pelt quality in mink was studied. Two groups of pastel female mink were fed either 59% (high protein, HP) or 40% (low protein, LP) of metabolisable energy (ME) from protein during pregnancy and lactation. Shortly after weaning, kits from females fed the LP diet were put on a new LP diet (21% protein of ME). Kits from females fed HP were randomly distributed to four experimental groups fed a new HP diet (34% protein of ME) and three of these groups were shifted to diets with 21% protein at different times during June until September. Skin biopsies were taken at 4, 6, 23 and, 29 wk of age. Histological techniques and computer-assisted light microscopy were used to determine the ratio of activity (ROA) of underfur and guard hairs, respectively, defined as the number of growing hairs as a percentage of the total number of hairs. The hair fibre length and thickness were determined by morphometric methods and correlated...

Effects of dietary supplement of essential amino acids on mortality rate, liver traits and blood parameters in mink (mustela vison) fed low‐protein diets

A low‐protein diet supplemented with essential amino acids to meet the estimated requirements for essential amino acids in growing mini and with a total amino acid nitrogen content of 65–75% of the requirement, was fed to male mink kits during the growing period from weaning to pelting. The effects on mortality rate, liver fat content, liver weights, growth performance, plasma activities of alanine‐aminotransferase (ALAT), plasma concentrations of total protein, urea, creatinine and bile acids and haematocrit values were studied. The results showed that the mink has a high requirement of dietary protein besides essential amino acids, especially glucogenic amino acids. Feeding a low‐protein diet caused increased mortality rate, liver lipidosis, increased plasma activity of ALAT and reduced growth performance compared with control feeding. A dietary supplement of essential amino acids to the low‐protein diet did not improve the health status, but had a positive effect on growth performance compared with the...

Effects of High Dietary Levels of Fresh or Oxidised Fish Oil on Performance and Blood Parameters in Female Mink (Mustela vison) During the Winter, Reproduction, Lactation and Early Growth Periods

The effects of high dietary levels of fresh or moderately oxidised fish oil on performance and blood parameters in mink females were investigated during the winter, reproduction, and lactation periods. Furthermore, the effects of the diets on kit performance were investigated during the lactation and early growth periods. The investigation was carried out with a total of 292 females distributed in five experimental groups fed fresh fish oil stored frozen, fresh fish oil ensiled, oxidised fish oil stored frozen, oxidised fish oil ensiled, and soya oil, respectively. The females were weighed three times during the winter period, and the females and the kits were weighed at parturition and 2, 4, and 7 weeks post partum. Blood samples were collected from the females and the kits 6 and 8 weeks post partum, respectively. The results show that high dietary levels of fresh or moderately oxidised fish oil could be used for mink females during the winter and reproduction periods without any negative effects on performance, health and reproduction results. However, high levels of fish oil resulted in lower kit weights at weaning. These negative effects on kit growth were related to the dietary composition fed during the lactation and early growth periods and not to the diet used during the preceding winter and pregnancy periods. A high intake of polyunsaturated fatty acids resulted in a decreased number of blood platelets for both mink females and their kits.

Glucose Homoeostasis and Regulation in Lactating Mink ( Mustela vison ): Effects of Dietary Protein, Fat and Carbohydrate Supply

The ability of lactating mink dams to control glucose homoeostasis, when fed diets containing different ratios of metabolizable energy (ME) from protein, fat and carbohydrates, was studied by measuring plasma concentrations of glucose, insulin, glucagon, urea and free fatty acids (FFA), in the fasted and absorptive state 4 weeks postpartum, in two consecutive years. A total of 36 yearling female mink, fitted with jugular vein catheters and raising litters of six or seven kits, was fed ad libitum lactation diets with different amounts of ME derived from protein, fat and carbohydrates (year 1:61:37:2, 46:37:17 and 31:37:32; year 2:61:38:1, 47:52:1 and 33:66:1). After 3 h fasting the dams were fed 210 kJ ME of the experimental diets. Blood samples were drawn 10 and 5 min before feeding and 30, 60, 90, 120, 150 and 180 min postprandially. The glucose concentration was increased 30 to 150 min postprandially in dams fed the carbohydrate-containing diets (46:37:17 and 31:37:32), whereas the glucose concentration showed no postprandial response in dams fed the carbohydrate-free diets (61:38:1, 47:52:1 and 33:66:1). Plasma insulin concentrations were increased 30 to 120 min postprandially in all dams, irrespective of dietary treatment. Plasma concentrations of glucagon were higher ( P <0.005) in dams fed the low-protein diets (31:37:32 and 33:66:1) than in dams fed the high-protein diets (61:37:2 and 61:38:1). Postprandially, the glucagon : insulin ratios decreased in dams fed the carbohydrate-containing diets, whereas the glucagon:insulin ratios tended to increase in dams fed the carbohydrate-free diets. Plasma concentrations of urea were significantly higher in dams fed the high-protein diets. Plasma concentrations of FFA, measured in the second experiment (year 2) only, showed increased concentrations postprandially, the responses being significant in dams fed the 33:66:1 and 61:38:1 diets. In conclusion, the mink is able to regulate the concentrations of blood constituents involved in maintaining glucose homoeostasis, and thereby to adapt to a wide range of dietary protein and carbohydrate supply.