Influence of the dietary hay/maize ratio on digestion in the stomach of cattle

[Food conversion in the digestive system of juvenile bulls. 3. Rumen liquor investigations]

Two bulls with a permanent rumen fistula and a re-entrant cannula at the duodenum were fed various concentrates and straw (dry matter ration composition: 60% concentrate, 40% straw). Negative correlations were found between the pH value and total fatty acid concentration (r = -0.70). The animals were given the straw one hour before the concentrate. The pH value increased to not more than 7.3 one hour after they had received the straw. It did not drop below 6.4 after the concentrate with any of the rations. The addition of dried sugar beet pulp to the rations leads to a higher mean acetate concentration than the other rations and causes an unvarying high total fatty acid concentration.

[Ruminal nitrogen metabolism in calves and sheep. 3. Effect of hay-concentrate ratio in calves]

During the milk feeding period (ca. 55th day of life) and 2 weeks after the milk feeding period (ca. 80th day of life) the influence of a hay quota in the ration (on DM basis) of 6, 10, 14 and 18% in the milk feeding period and of 16, 23, 31 and 37% in the period after milk feeding was tested as to ruminal N metabolization with calves supplied with duodenal re-entrant cannulae. The increase of the hay quota in the ration for ruminating calves reduced as a tendency duodenal NAN passage, its bacterial N-quota, post-ruminal NAN digestibility and, due to a worse utilization of available N for bacterial N-synthesis, bacterial N-synthesis rate. The apparent fermentation of organic matter was, as a tendency, increased with the growing hay quota in the ration.

Protein and energy relationships in dairy cattle. 1. Dry cows

Nitrogen metabolism in ruminants is a dynamic process depending on level of intake and composition of dietary dry matter and on the physiological state of the animals. These parameters were analysed in a regression model for the requirements of nitrogen absorbed in the small intestine in relation to nitrogen balance of dry cows fed at maintenance level. The amount of total dietary nitrogen and the apparent nitrogen digestibility vary notably according to energy intake and energy concentration in dietary dry matter. On the contrary, the amount of nitrogen absorbed in the small intestine is only slightly affected by these parameters. The discrepancy between these statements lies mainly in differences in intestinal nitrogen absorption and in altered fermentation processes of the large intestine in response to changes in energy supply and ME concentration in dietary dry matter.

The association of maize silage with urea: the effect on the ammonia content of the rumen fluid, the N flow in the duodenum, the nitrogen and energy balances and the milk production

In different experiments, the nutritive value of maize silage associated with urea was compared with that of the same forage without any N supplement. The ammonia concentration in the rumen liquor was measured with two dry cows fitted with a permanent rumen cannula. Urea was rapidly hydrolysed in the rumen and gave rise to high ammonia concentrations. The control diet did not supply enough fermentable nitrogen to the ruminal flora. The duodenal N flow was measured with two dry cows fitted with a re-entrant cannula at 10 cm from the pylorus. When increasing amounts of urea were fed, the duodenal N flow initially increased to a maximum, but it leveled off with higher amounts of urea in the diet. With 13 cows in the second part of lactation, the feeding of urea increased the nitrogen balance of the animals and the metabolizable energy density of the rations. However, the milk production and the milk protein secretion were only slightly enhanced.