Jakob Sehested

Effect of concentrate supplementation level on production, health and efficiency in an organic dairy herd

The proportions of organic feed and roughage in the feed ration for organic dairy cows have to reach 100 and 60%, respectively, in 2005. The aim of this study was to elucidate the long-term effects of reducing or omitting concentrate supplementation to high genetic merit dairy cows on a basal ad libitum diet of clover-grass (silage and grazing). Three concentrate levels, N, L and L+ (38, 0 and 19% of dry matter (DM) intake, respectively) were investigated in a herd of 60 cows during 3 years. The production in group N was 6723 kg energy corrected milk (ECM) per cow year, based on an intake of 6226 kg DM of which 38% was concentrates. In group L the omission of concentrates reduced intake to 4770 kg DM, and milk production to 5090 kg ECM per cow year. Milk protein content was reduced and milk free fatty acid content was increased, and the first calving interval was significantly increased, as compared to group N. The intake in group L+ was 5226 kg DM per cow year of which 19% was concentrates. Milk production in group L+ was reduced by only 493 kg ECM per cow year as compared to group N, primarily due to a significantly improved feed conversion ratio (12%). There were no indications of health problems associated with the reduced feeding levels.

Feed-induced changes in the transport of butyrate, sodium and chloride ions across the isolated bovine rumen epithelium.

A short-chain fatty acid (SCFA) burst feeding strategy to dry cows (periodically high SCFA concentration in the ruminal fluid) has been hypothesized to increase the ruminal surface area and absorptive capacity. The present paper deals with the effects of a SCFA burst feeding strategy on epithelial transport function in dry cows. The epithelial transport capacity for [14C]butyrate and Na+ across the rumen epithelium in vitro was significantly increased by the SCFA burst feeding strategy, compared with the controls. The transport of Cl- was significantly increased by the SCFA burst feeding strategy at the high feeding level, but non-significantly decreased at the low feeding level. The increase in transport capacity could not be attributed to changes in epithelial resistance, to the concentration of Na+/K+-ATP-ase or to the epithelial surface area and structure (data on epithelial surface area and structure were published by Andersen et al., Report No. 23 from the National Institute of Animal Science, Denmark, 1994). The observed changes in transport must reflect a change in either composition of the cell membranes or processes that facilitate transport through the cell, including metabolic processes. The presented results support the existence of a saturable SCFA transport system in the epithelial cells and the results show that the capacity of this transport system can be the subject for feed-induced regulation.

Effect of decreasing dietary phosphorus supply on net recycling of inorganic phosphate in lactating dairy cows

Five ruminally cannulated lactating Holstein cows, fitted with permanent indwelling catheters in the mesenteric vein, hepatic vein, portal vein, and an artery were used to study intestinal absorption and net recycling of inorganic phosphate (P(i)) to the gastrointestinal tract. Treatments were low P (LP; 2.4 g of P/kg of DM) and high P (HP; 3.4 g of P/kg of DM). The dietary total P (tP) concentrations were obtained by replacing 0.50% calcium carbonate in the LP diet with 0.50% monocalcium phosphate in the HP diet. Diets were fed for 14 d and cows were sampled on d 14 in each period. Cows were fed restrictively, resulting in equal dry matter intakes as well as milk, fat, and protein yields between treatments. Net P(i) recycling (primarily salivary) was estimated as the difference between net portal plasma flux (net absorption of P(i)) and apparently digested tP (feed - fecal tP difference). Phosphorus intake, apparently digested tP, and fecal tP excretion decreased with LP. An effect of decreased tP intake on net portal plasma flux of P(i) could not be detected. However, despite numerically minute net fluxes across the liver, the net splanchnic flux of P(i) was less in LP compared with that in HP. Though arterial plasma P(i) concentration decreased, net P(i) recycling was not decreased when tP intake was decreased, and recycling of P(i) was maintained at the expense of deposition of P(i) in bones. Data are not consistent with salivary P(i) secretion being the primary regulator of P(i) homeostasis at low tP intakes. On the contrary, maintaining salivary P(i) recycling at low tP intakes indicates that rumen function was prioritized at the expense of bone P reserves.

Interactions between phosphorus feeding strategies for pigs and dairy cows and separation efficiency of slurry.

ABSTRACT Phosphorus (P) in manure is a nutrient source for plants, but surplus P amended to fields represents a risk to the environment. This study examines the interactions between low‐P diets for pigs and dairy cows and the separation of animal slurry into a solid P fraction and a liquid fraction. Replacing inorganic phosphates with phytase in pig feed reduced the concentration of P in slurry by 35%, but supplementing concentrates to dairy cows did not affect the P concentration in cattle slurry. Particle‐size fractions of the slurry were not affected by these dietary changes. The amount of dry matter (DM) in the <0.025 mm fraction was greater in pig slurry than in cattle slurry, but the relative amounts of P and nitrogen (N) were larger in the >0.025 mm fraction. Replacing feed phosphate, in the form of mono‐calcium phosphate, with phytase in the pig diet reduced the separation index (efficiency) of P from 80% to 60%.

Effect of pregnancy and feeding level on cell turnover and expression of related genes in the mammary tissue of lactating dairy cows.

Milk yield is reduced by pregnancy, and the present experiment was conducted to study the biological basis for the negative effect of pregnancy on milk yield. A total of 16 dairy cows were fed at either a normal or a low feeding level (eight cows per treatment), and half of them were inseminated after approximately 3 months of lactation and the other half were not inseminated. Mammary biopsies were taken at approximately 9 months of lactation. The milk yield of pregnant cows was reduced by 2.6 kg/day, and lactation persistency was reduced already from the time of insemination. Low feeding level reduced the milk yield by 9.8 kg/day from week 8 to week 39 of lactation, whereas no interaction between pregnancy and feeding level was found. Cell proliferation (Ki-67) and apoptosis (terminal deoxynucleotidyl transferase dUTP nick end labeling, TUNEL) were unaffected by feeding level, and pregnancy tended to reduce cell proliferation but had no effect on apoptosis. Reduced cell proliferation may explain the reduced lactation persistency in pregnant cows. Transcription of oestrogen receptor α, progesterone receptor A and B, and long and short isoforms of the prolactin receptor were higher in pregnant cows compared with non-pregnant cows. Feeding level did not mediate changes in transcription of genes. Transcription of other cell-turnover-related genes (IGF-I, IGF binding protein-5, caspase-3) as well as genes related to the secretory activity of the cells (α-lactalbumin and acetyl CoA carboxylase α) was not affected by pregnancy or by feeding level.

Effect of exogenous phytase on feed inositol phosphate hydrolysis in an in vitro rumen fluid buffer system.

Three in vitro experiments using a rumen fluid buffer system were performed to investigate the effect of addition of 4 experimental phytases (Phy1, Phy2, Phy3, and Phy4) compared with no addition of phytase on feed inositol phosphate hydrolysis in wheat and rapeseed cake to determine which of the 4 phytases was most suitable under rumen-like conditions. The feedstuffs were incubated with a mixture of physiological buffer, ruminal fluid, and exogenous phytase at pH 6.2, after which the samples were incubated for different periods. Incubations were stopped using HCl, and the samples were analyzed for inositol phosphates via high performance ion chromatography. Addition of phytase (Phy1) resulted in enhanced degradation of myo-inositol hexakisphosphate (InsP(6)) in rapeseed cake, whereas addition of exogenous phytase did not improve the degradation of InsP(6) in wheat. Only rapeseed cake was therefore used subsequently. All 4 phytases increased degradation of InsP(6) in rapeseed cake in the in vitro system, and degradability of InsP(6) increased with higher incubation time and higher phytase dosages, independent of phytase. Addition of 2 units of phytase per gram of substrate of the phytases Phy1, Phy2, Phy3, and Phy4 led to an undegraded InsP(6) content of 56, 49, 70, and 18%, respectively, when incubated with rapeseed cake for 6h, indicating that Phy2 and Phy4 were the most effective phytases. However, Phy2 had a higher specific activity than Phy4, as 60% of the original InsP(6) content was remaining after 3h when 5mg of enzyme protein per gram of substrate of Phy2 was added to rapeseed cake, whereas 150 mg of enzyme protein per gram of substrate of Phy4 was necessary to achieve a similar result. Therefore, Phy2 appeared to be most applicable under rumen-like conditions.

Gastrointestinal development of dairy calves fed low- or high-starch concentrate at two milk allowances

The objective was to study the effect of type of concentrate with varying starch and fibre content on growth and gastrointestinal development in preweaned dairy calves. Thirty-two newborn Danish Holstein male calves were allocated to four treatment groups in eight blocks of four calves. An experimental low-starch, high-molasses, high-fibre (EXP) concentrate or a traditional high-starch (TRA) concentrate were fed either at a high (HIGH; 2 × 3.2 kg/day) or a low (LOW; 2 × 1.6 kg/day) whole milk allowance in a 2 × 2 factorial design. TRA contained 350 and EXP 107 g starch/kg dry matter (DM), whereas the NDF content was 136 and 296 g/kg DM, respectively. Metabolizable energy (ME) was 11.2 and 12.2 MJ ME/kg DM in EXP and TRA, respectively. All calves had free access to artificially dried grass hay (9.8 MJ ME/kg DM). Four calves were culled during the experiment. The calves were euthanized either at 38 (12 calves) or 56 days (16 calves) of age. Evaluated across both slaughter ages, there was no difference between TRA and EXP in concentrate and hay intake, rumen weight and papillation. EXP resulted in increased villi number in duodenum and jejunum compared with TRA. Concentrate intake and reticulo-rumen weight was higher for LOW compared with HIGH milk allowance, whereas live weight gain was 20% lower. The results show that a low-starch, high-molasses, high-fibre concentrate with 8% lower ME content tended to reduce daily gain compared with a traditional calf starter concentrate, but resulted in similar ruminal development in preweaned calves both on a high and a low milk allowance fed along with grass hay. Furthermore, the results suggest that the experimental concentrate stimulated intestinal villi growth over that of the traditional concentrate.

Transfer of Dietary Zinc and Fat to Milk—Evaluation of Milk Fat Quality, Milk Fat Precursors, and Mastitis Indicators

The present study demonstrated that the zinc concentration in bovine milk and blood plasma is significantly affected by the intake of saturated fat supplements. Sixteen Holstein cows were used in a 4 x 4 Latin square design with 4 periods of 12 d, and 4 dietary treatments were conducted. A total mixed ration based on corn silage, grass-clover silages, and pelleted sugar beet pulp was used on all treatments. A high de novo milk fat diet was formulated by adding rapeseed meal and molasses in the total mixed ration [39 mg of Zn/kg of dry matter (DM)], and a low de novo diet by adding saturated fat, fat-rich rapeseed cake, and corn (34 mg of Zn/kg of DM). Dietary Zn levels were increased by addition of ZnO to 83 and 80 mg of Zn/kg of DM. Treatments did not affect daily DM intake, or yield of energy-corrected milk, milk fat, or milk protein. The high de novo diet significantly increased milk fat percentage and milk content of fatty acids with chain length from C6 to C16, and decreased content of C18 and C18:1. Treatments did not influence milk free fatty acids at 4 degrees C at 0 or 28 h after milking. The average diameter of milk fat globules was significantly greater in milk from cows offered low de novo diets. Furthermore, the low de novo diet significantly increased the concentration of nonesterified fatty acids and d-beta-hydroxybutyrate in blood plasma, the latter was also increased in milk. Treatments did not affect the enzyme activity of lactate dehydrogenase and N-acetyl-beta-d-glucosaminidase in milk or the activity of isocitrate dehydrogenase and malate dehydrogenase in blood plasma. The low de novo diet significantly increased plasma Zn and milk Zn content, whereas dietary Zn level did not in itself influence these parameters. This indicates that the transfer of fat from diet to milk might facilitate transfer of Zn from diet to milk.

Effect of starch level and straw intake on animal performance, rumen wall characteristics and liver abscesses in intensively fed Friesian bulls

The objective was to reduce the incidence of liver abscesses (LAs) in young bulls by reducing the starch content of the concentrate and increasing the straw intake by adding molasses without reducing performance. Eighty-five Danish Friesian bulls (146 ± 2.6 kg live weight (LW)) were allocated to four treatment groups in a 2 × 2 factorial design and were ad libitum fed either a high (H) (43%) or a low (L) (25%) starch concentrate, and either chopped barley straw (S) or a mixture (Sm) of chopped barley straw and sugar-beet molasses (75:25). The bulls were slaughtered at 440 (±4.2) kg LW (11.3 months of age) on average. The concentrate dry-matter intake (DMI) was 7.5% higher (P < 0.001), the roughage DMI was 12% higher (P < 0.01), whereas the total net energy intake was 7% lower (P < 0.001) for the L compared with the H concentrate. By adding molasses to the straw, roughage DMI increased from 0.50 to 0.96 kg/day (P < 0.001). Average daily gain (ADG) was not affected by treatment. Feed conversion efficiency (FCE) for dry matter (FCEDM) was decreased (P < 0.001), whereas FCE for net energy (FCENE) was increased with the L concentrate (P < 0.01), suggesting a lower utilisation of the cell wall fraction with the H starch concentrate. There were no major effects of treatment on carcass characteristics. The higher roughage intake with Sm prevented rumen wall damage, but did not reduce the number of animals with LAs. The L concentrate did not affect the rumen wall but reduced the level of LA (2 v. 9 animals, P < 0.02). There was a higher level of respiratory diseases in animals fed the H concentrate (P < 0.05). The experiment showed that it was possible to maintain performance and reduce LA by using a lower starch content of the concentrate.

Feeding phosphorus (P) to cattle: A new basis for Nordic recommendations

Phosphorus (P) is an essential nutrient and significant safety margins have until now been included in both feeding recommendations for cattle and allocation of P in practice. However, there is a need to optimize the utilization of P in cattle and thereby minimize its allocation and excretion. This demands well-defined requirements and availabilities of P in feeds as well as fairly precise use of this knowledge in practice. The purpose of this paper is to review the current knowledge and to give proposals for feeding phosphorus to cattle in relation to physiological requirement, availability of phosphorus in feeds, and minimal excretion of P. There is scientific and practical basis for a reduction of recommendations and allocation of P to cattle in the Nordic countries. No evidence or indication is found that surplus P relative to physiological requirement is beneficial. Future P feeding recommendations should continuously be based on the factorial method. The quantitatively most important improvement will be the increase and differentiation of the TAC value (true availability coefficient), which can be raised from 0.55 to 0.65 and 0.70 for the most common feeds. However, there is still no basis for a specific TAC for an individual feedstuff. When applying the recommended P allocation, it will be possible to increase the utilization of P in, e.g. high producing dairy cows, to 35–40%.