Periparturient concentrations of insulin glucagon and ketone bodies in dairy cows fed two different levels of nutrition and varying concentrate/roughage ratios

Strategies for increasing energy density of dry cow diets

The objective of this trial was to compare the effects of increasing dietary energy density from 1.51 to 1.65 Mcal/kg of dry matter (DM) by replacing forage with concentrate or by further increasing concentrate via the substitution of corn silage and alfalfa silage by a mixture of straw, starch, and soybean meal. Our hypothesis was that the latter diet would be more glucogenic while increasing rumen fill and be potentially desirable for transition cows. Nine far-off dry cows (greater than 3 wk before parturition at the end of the trial) were fed three diets: low energy diet, [LE, 1.51 Mcal/kg of DM, 14.0% crude protein (CP) and 35% nonfiber carbohydrates (NFC)], high energy diet, (HE, 1.65 Mcal/kg of DM, 13.9% CP and 39.5% NFC) and high energy diet, where a portion of alfalfa and corn silage was replaced by straw, soybean meal, and cornstarch (HES, 1.65 Mcal/kg of DM, 13.5% CP and 40.5% NFC). The experiment was a replicated 3 x 3 Latin square design with 21-d periods. Six cows from two squares were used to examine kinetics of DM disappearance from nylon bags suspended in the rumen. Two contrasts of interest were: LE versus HE, HES (effects of energy density) and HE versus HES (method of increasing energy density). Increasing energy density increased the potentially degradable (B) and decreased the undergradable (C) DM fractions of the diets. Because HES had greater B and a faster rate of degradation of fraction B (k), effective rumen degradable DM (ERDDM) was higher in HES compared to HE. Cows fed high energy diets had greater DM intake. No differences in DM intake were observed between HE and HES. Rumen volume or DM pool sizes were not affected by treatment. High energy diets increased total ruminal fluid volatile fatty acid concentration compared with LE. Propionate concentration was higher in cows fed high energy diets compared with cows fed LE. The partial replacement of alfalfa and corn silage by straw, soybean meal, and cornstarch further increased propionate concentration. The greatest increase in serum insulin concentration following feeding was observed in cows fed HE. Cows consuming high energy diets had lower plasma nonesterified fatty acids (NEFA) before and after feeding. The HES diet was less effective in decreasing plasma NEFA concentration after feeding compared to HE. In conclusion, increasing diet energy density of far-off dry cows positively affected DMI, ruminal propionate, serum insulin, and plasma NEFA. Increasing energy density with a blend of feeds that represent extremes in rates of carbohydrate fermentation may be a strategy to provide greater amounts of glucogenic precursors. Applicability of this strategy should be examined in transition cows.

Dry cow management for the prevention of ketosis and fatty liver in dairy cows

Dramatic increases in energy requirements during late gestation and early lactation, superimposed on an animal with a profound drop in DMI just before calving, make the dairy cow highly susceptible to the metabolic diseases ketosis and hepatic lipidosis. Increased serum concentrations of NEFA appear to be causally linked to these problems, and feeding strategies to reduce or avoid this dramatic increase are desirable for optimal health and performance. During the last 3 to 4 weeks prepartum, a diet higher in energy and protein concentration than current NRC recommendations should be fed so that adequate nutrient intake occurs within the limits of the reduced DMI. The additional energy should be provided by glucose precursors, such as starchy concentrates or propylene glycol, and not by lipid. Excessive energy and reduced fiber should be avoided both early in the dry period (more than 28 days prepartum) and immediately postpartum. Attention should be paid to the environment of the cow, especially during the last 3 weeks prepartum, to avoid environmental stressors as much as possible.

Effects of different energy levels, concentrate/forage ratios and lipid supplementation to the diet on the adaptation of the energy metabolism at calving in dairy cows

A low level of energy (110 MJ ME) and a low concentrate/forage ratio (10/90) at calving resulted in low basal concentrations of glucose and insulin, but the cows had the capacity to increase the glucose level after glucagon injections. No signs of disturbances in the metabolic adaptation were observed. High intensity feeding (200 MJ ME and 50% concentrates) resulted in high basal serum insulin levels. The increase in the insulin concentrations after glucagon injections and the changes in insulin levels around calving varied widely between individual cows. The metabolic adaptation period was longer than in cows in the former group. An energy level of 170 MJ ME and variations of concentrate/forage ratios (5/95, 30/70 and 60/40) resulted in small differences in basal glucose and insulin concentrations and in response to glucagon injections. But the cows fed 60% concentrates showed signs of prolonged metabolic adaptation. Increased lipid concentrations in diets containing equal levels of energy and protein resulted in a fall in basal glucose and insulin levels and the metabolism seemed to be directed towards catabolism. Because of these metabolic effects, more needs to be known on fat supplementation if it is used in practical feeding. It is also necessary to take more interest in the effects of protein feeding on the periparturient metabolism.

The adverse effects of long-term cassava (Manihot esculenta Crantz) consumption

Cassava (Manihot esculenta Crantz) is an important dietary staple for more than 500 million people in developing countries. People eat 60% of the cassava produced and one third of the harvest feeds animals. All cultivars of cassava contain the cyanogenic glucoside, linamarin, but in different concentrations. The roots of those cultivars with high cyanogenic content are processed to reduce the level of linamarin, because linamarin is hydrolysed in the intestinal tract of both men and animals by microbial flora and HCN is released. Researchers have implicated the sublethal levels of HCN produced on ingestion in the development of a number of metabolic diseases in both man and animals when cassava-based diets are consumed over a long period of time but the release of HCN cannot fully explain the metabolic effects of ingested linamarin. A significant amount of linamarin remains intact and is excreted in the urine. It appears that the intact linamarin inhibits Na+K+ATPase causing electrolyte imbalance within the cell. This phenomenon is exacerbated by free radicals generated by the hypoxia/normoxia cycles created by cyanide released from linamarin, which cause lipid peroxidation and cell membrane damage. When the supply of endogenous thiosulphate is adequate, cyanide plays a very minor role in the development of lesions. The amount of damage is related to the quantity of linamarin routinely ingested at sublethal levels. There appears to be species differences in the rate of the development of diseases and the intensity.