Nutrient requirements of dairy cattle , Nutrient requirements of dairy cattle , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Nutrient requirements of dairy cattle

During subacute ruminal acidosis (SARA) rumen pH is depressed for several hours per day due to accumulation of volatile fatty acids and insufficient rumen buffering. Surveys suggested an incidence of SARA of between 19% and 26% in early and mid-lactation dairy cows. Causes of SARA include feeding excessive amounts of non-structural carbohydrates and highly fermentable forages, and insufficient dietary coarse fiber. Consequences of SARA include feed intake depression, reduced fiber digestion, milk fat depression, diarrhea, laminitis, liver abscesses, increased production of bacterial endotoxin and inflammation characterized by increases in acute phase proteins. The increase in endotoxin is similar among methods for SARA induction, but depends on the diet fed before induction. Increases in acute phase proteins vary among methods of SARA induction, even when the methods result in similar rumen pH depressions. This suggests that the inflammatory response might not be solely due to bacterial endotoxin in the rumen.

Subacute ruminal acidosis in dairy cows: the physiological causes, incidence and consequences.

Understanding and preventing subacute ruminal acidosis in dairy herds: A review

For the last several decades, antimicrobial compounds have been used to promote piglet growth at weaning through the prevention of subclinical and clinical disease. There are, however, increasing concerns in relation to the development of antibiotic-resistant bacterial strains and the potential of these and associated resistance genes to impact on human health. As a consequence, European Union (EU) banned the use of antibiotics as growth promoters in swine and livestock production on 1 January 2006. Furthermore, minerals such as zinc (Zn) and copper (Cu) are not feasible alternatives/replacements to antibiotics because their excretion is a possible threat to the environment. Consequently, there is a need to develop feeding programs to serve as a means for controlling problems associated with the weaning transition without using antimicrobial compounds. This review, therefore, is focused on some of nutritional strategies that are known to improve structure and function of gastrointestinal tract and (or) promote post-weaning growth with special emphasis on probiotics, prebiotics, organic acids, trace minerals and dietary protein source and level.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1439-0396.2012.01284.x

Gastrointestinal health and function in weaned pigs: a review of feeding strategies to control post‐weaning diarrhoea without using in‐feed antimicrobial compounds

Subacute ruminal acidosis (SARA) is likely to arise when an easily palatable, high-energy diet meets a ruminal environment not adapted to this type of substrate. Increase of short-chained fatty acids (SCFA) will occur. Eventually, this may result in a transient nadir of ruminal pH below 5.5. Two situations are likely to represent the risk of SARA. First, fresh lactating cows are confronted with a diet considerably differing from that in the dry-period. A diet change carried out too rapidly or without proper transition management will put the animals at risk. Secondly, further in lactation, inaccurate calculation of dry-matter-intake (DMI) leading to wrong roughage/concentrate ratio, an inadequate content of structure within the diet or mistakes in preparing of total mixed rations may produce SARA. The consequences of SARA are diverse and complex. Laminitis is regularly connected to SARA and the negative impact of organic acids on the ruminal wall may lead to parakeratosis enabling translocation of pathogens into the bloodstream provoking inflammation and abscessation throughout the ruminant body. Moreover, milk-fat depression (MFD) can be related to SARA. In order to achieve a proper diagnosis, SARA has to be understood as a herd-management problem. A screening of the herd for SARA by means of a rumenocentesis, performed on a sample-group, preferably 12 individuals, may reveal the presence of SARA. The herd screening should include the risk group suspected, preferably. The prevention of SARA applies to the principles of ruminant feeding. Careful transition management from the dry to the lactation period and control of fibre-content and ration quality should be more yielding than the use of buffers or antibiotic drugs.

Subacute ruminal acidosis (SARA): a review.

Effect of Milk Allowance on Concentrate Intake, Ruminal Environment, and Ruminal Development in Milk-Fed Holstein Calves

The unidirectional transport and metabolism of 14C-labeled acetate, propionate and butyrate across the isolated bovine rumen epithelium was measured in vitro by the Ussing chamber technique There was a significant, but relatively small, net secretion of acetate and propionate, and a large and significant net absorption of butyrate The results demonstrate that the mucosal-serosal (MS) pathway for short-chain fatty acids (SCFA) is different from the serosal-mucosal (SM) pathway, and that butyrate is treated differently from acetate and propionate by the epithelium The results support that the main route for epithelial SCFA transport is transcellular The correlation between SCFA lipophility and the flux rate was positive but weak at both pH 73 and 60 Decreasing pH increased all SCFA fluxes significantly, but not proportionally to the increase of protonized SCFA in the bathing solution There was a significant and apparently non-competitive interaction between the transport of acetate, propionate and butyrate It seems that mediated transport mechanisms must be involved in epithelial SCFA transport in the bovine rumen, but the data do not exclude that passive diffusion could account for a significant part of the flux The metabolism of SCFA in the Ussing chamber system was considerable, and there was a clear preference for excretion of CO2 from this metabolism to the mucosal side, while side preference for non-CO2 metabolite excretion was not studied Of the propionate and butyrate transported in the MS direction, 78 and 95% was metabolised, while only 37 and 38% was metabolised in the SM direction (acetate metabolism could not be measured) There was, however, no simple relation between the degree of metabolism and the transport rate or the transport asymmetry of the SCFA

Ruminal transport and metabolism of short-chain fatty acids (SCFA) in vitro: effect of SCFA chain length and pH

(1999). Effect of Dry Cow Feeding Strategy on Rumen pH, Concentration of Volatile Fatty Acids and Rumen Epithelium Development. Acta Agriculturae Scandinavica, Section A — Animal Science: Vol. 49, No. 3, pp. 149-155.

Effect of Dry Cow Feeding Strategy on Rumen pH, Concentration of Volatile Fatty Acids and Rumen Epithelium Development

Unidirectional transport rates of sodium (22Na+) and chloride (36Cl-) across bovine rumen epithelium were measured in vitro by the Ussing chamber technique The active and short-chain fatty acid (SCFA)-stimulated sodium transport was shown to fit Michaelis-Menten kinetics, and was rate limited mainly by one transport system, characterized by a Km of 43 mmol l-1 Na+ and a Jmax (maximal transport rate) of 62 mumol cm-2 h-1 Na+ It was confirmed that the basolateral Na+,K(+)-ATPase was essential for active sodium transport, and that an apical amiloride-sensitive sodium transport system (Na(+)-H+ exchange) was involved in a minimum of 60-70% of the active sodium transport in the presence of SCFAs (butyrate) The main part of both the mucosal-serosal (MS) and serosal-mucosal (SM) sodium flux was sensitive to an applied electrical potential difference (PD) It is noteworthy that an applied PD, equal to the in vivo PD (+30 mV, lumen as reference), abolished net transport of sodium The stimulating effect of a mixture of acetate, propionate and butyrate on active sodium transport was confirmed, and it was further shown that the stimulating effect of each of the three SCFAs was nearly equal Analogues of naturally occurring SCFAs (isobutyrate and 2-ethyl-butyrate) did not stimulate active sodium transport, but inhibited the stimulating effect of butyrate The stimulating effect of butyrate was clearly concentration dependent and showed a maximum at approximately 20 mmol l-1 butyrate Above this limit active sodium transport was decreased with increasing butyrate concentration This suggests that there was a limit to the amount of butyrate that could be handled by the epithelium The active sodium transport was clearly correlated with the chloride concentration, and was significantly reduced, but not abolished, by replacement of chloride with gluconate Active transport of chloride was stimulated by butyrate and reduced by the Na(+)-H+ exchange inhibitor amiloride (3 mmol l-1) There was no effect of the Cl(-)-HCO3- exchange inhibitor DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid; 05 mmol l-1) on sodium transport HCO3- (13 mmol l-1) and CO2 (5%) themselves had only a small and non-significant stimulating effect on sodium fluxes, however, in the presence, but not the absence of HCO3- and CO2 in the experimental solutions acetazolamide (1 mmol l-1) significantly reduced active sodium transport It is concluded that SCFAs could stimulate the active sodium and chloride transport as a result of their metabolism The CO2 produced could stimulate apical Na(+)-H+ and Cl(-)-HCO3- exchangers running in parallel via increased H+ and HCO3- gradients

Transport of sodium across the isolated bovine rumen epithelium: interaction with short-chain fatty acids, chloride and bicarbonate.

Short-chain fatty acids are the main end-products of microbial metabolism in the forestomach of ruminants. SCFA produced by the microorganisms are rapidly absorbed across forestomach epithelia and can cover up to 80% of the energy requirement of the animal. Although there is a great concentration gradient for SCFA between the forestomach content and the blood favoring passive transport, (secondary) active transport mechanisms are likely involved in SCFA permeation across the epithelia. (Secondary) active SCFA transport seems to be mediated by an anionic exchange system. The system interacts with other anions like chloride and bicarbonate. Similar to the large intestine of various species, SCFA can stimulate sodium transport probably by activating a Na+/H+ exchange located in the apical membrane. However, in contrast to the large intestine, SCFA transport itself seems to be independent from sodium. Part of the absorbed SCFA does not reach the blood side in the original form because it is metabolized in the epithelial cell. Metabolism, in turn, influences SCFA transport.

Jakob Sehested

Papers

Effect of Milk Allowance on Concentrate Intake, Ruminal Environment, and Ruminal Development in Milk-Fed Holstein Calves

Ruminal transport and metabolism of short-chain fatty acids (SCFA) in vitro: effect of SCFA chain length and pH

Effect of Dry Cow Feeding Strategy on Rumen pH, Concentration of Volatile Fatty Acids and Rumen Epithelium Development

Transport of sodium across the isolated bovine rumen epithelium: interaction with short-chain fatty acids, chloride and bicarbonate.

SCFA-transport in the forestomach of ruminants