The sustenance of growing and fattening ruminants by intragastric infusion of volatile fatty acid and protein

Abstract

A technique is described for feeding young sheep for long periods entirely by the infusion of volatile fatty acids into the rumen and protein and other essential nutrients into the abomasum. When the energy infused was twice the estimated requirement for maintenance, growth rate and nitrogen retention were essentially the same as in normally-fed sheep.There are several principles of the nutrition of ruminants which are difficult to study because their diets are fermented to yield volatile fatty acids (VFA). The VFA can vary both in the amounts produced and in composition, and both can vary during a feeding cycle. The rumen micro-organisms produce microbial protein in varying amounts and the dietary protein is degraded by rumen microbes to varying extents (Orskov, 1977). Infusion of VFA at higher levels was attempted by Armstrong & Blaxter (rg57b) and Orskov & Allen (1965) fed increments of salts of VFA with concentrate diets. These latter studies suffer from the disadvantage of possible interference of the VFA, or their salts, with the digestion and metabolism of the basal diet since it was only achieved when the animals were given a basal diet of solid food, and even with that regimen only small additions of VFA or VFA salts were possible. Attempts to sustain long-term infusion of VFA alone have generally been abandoned owing to problems of electrolyte imbalance and acidity of rumen contents. Tao & Asplund (1979, however, have recently sustained lambs at maintenance energy levels for periods of some weeks by infusion of partially-neutralized VFA and buffer solutions into the rumen, and amino acids into the abomasum, but they also reported several problems and deaths due to electrolyte imbalance.The method reported here was developed to sustain ruminants at high feeding levels and maintain normal growth by complete intragastric infusion. EXPERIMENTALThe following is a description of the infusion technique as it was developed after several attempts which failed. Since, however, the blood composition and rumen pH were measured routinely it was possible when an animal showed signs of severe stress or died to make an appropriate change in the procedure. The first attempts failed because VFA alone was infused as a result of which the animal developed, after some days, a severe acidosis. Other attempts failed as a result of partially neutralizing the VFA with sodium hydroxide. Toxic levels of sodium in the blood in excess of 200 mmol/l were observed. It was finally realized that the rumen pH and blood electrolytes could be kept in the normal range provided a 0007-1 145 179 13185-2710 f 01'00

Modelling purine derivative excretion in dairy goats: endogenous excretion and the relationship between duodenal input and urinary output

“…Initially proposed to be applied in sheep (Pé rez et al, 1998), the method based on the urinary dilution of labelled exogenous purines allows determination of the endogenous component of the urinary PD without having any adverse physiological effect on the animals. Using that method in sheep, the above authors obtained an endogenous excretion of 115.2 mmol/kg LW 0.75 , which was in the range (92 to 150 mmol/kg LW 0.75 ) reported by non-isotopic studies based on intragastric or digesta draining methods (Ørskov et al, 1979;Giesecke et al, 1984;Chen et al, 1990;Balcells et al, 1991). Furthermore, the technique has been used in lactating cows , showing that recycling of exogenous PB into the tissues by the salvage mechanism was negligible .…”

Inhibition of reticulo‐ruminal motility by volatile fatty acids and lactic acid in sheep.

“…To ensure uniform concentrations of acid throughout the rumen during ruminal infusions many experiments were made in sheep maintained by infusion of a liquid diet (0rskov, Grubb, Wenham & Corrigall, 1979), with the ruminal contents mixed externally by pump.…”

Inhibition of Forestomach Motility by Short-Chain Volatile Fatty Acids in Sheep

“…However, VFAs also inhibir rhe inrrinsii forestomach motility of vagotomized sheep (Gregory 1984) and so a direct action on the forestomach may also be involved. By maintainrng sheep totally with intragastric infusion ofnutrients (Orskov et al 1979) it is possible to manipulate the rumen contents preciiely and so determine accurately the ruminil concentrarion of each VFA needed to cause abolition of motility.…”