Search

The objective of this study was to determine the early responses to a moderate concentrate increase in cattle diets with regards to various behavioral and physiological responses in cattle. Eight ruminally cannulated Angus crossbred beef heifers were adapted to a 70% concentrate diet (T70) and then switched to a 90% concentrate diet (H90). Measurements of feeding behavior, ruminal pH and temperature, rumen motility, liquid passage rate, and blood acid–base status were conducted on T70 as well as first day (d1) and second day (d2) of high-grain H90feeding to monitor the beginning of the transition period. Ruminal pH was below 5.6 for longer on both days of H90 compared with T70, suggesting animals experienced subacute ruminal acidosis while switching from T70 to H90. Transitioning did not affect dry matter intake (DMI). Eating rate during meals was reduced on d1 and d2 H90 compared with T70. Ruminal contraction amplitude was reduced on both days of H90 feeding. Contraction duration was reduced on d1 H90, and returned to T70 values by d2 H90. Results indicated that a moderate transition to a finishing diet influenced feeding behavior and reduced rumen motility at the beginning time after transition, but did not influence voluntary DMI.

Twenty-four steers [initial body weight (BW) = 510 ± 4.9 kg] predominately of Angus breeding were used to determine the effect of dietary crude protein (CP) level [8.5, 10.7, 12.3 or 14.5%, dry matter (DM) basis; high-moisture-corn-based diets] on visceral mass, cellularity, and protein expression of ATP synthase, Na+/K+-ATPase, proliferating cell nuclear antigen (PCNA) and ubiquitin. Steers were on dietary treatment for 28 d. Kidney, liver, and reticulorumen weights (g) increased linearly (P -1 BW) linearly increased (P +/K+-ATPase expression increased linearly (P = 0.05) with increased CP. These results indicate that increasing dietary CP increases liver, kidney, lung, and rumen masses, and differentially influences expression of proteins influencing energy utilization and efficiency in liver, kidney, and small intestine.Key words: Dietary crude protein, visceral organ mass, cellular energy metabolism, steer

Eighteen Holstein bull calves averaging 100 kg were individually housed and radomly assigned to nine dietary treatments. Isonitrogenous diets, containing approximately 12% protein (DM basis), were offered free choice. Treatment 1 consisted of ground ear corn and liquid protein supplement (LPS-50) with 50% protein equivalent from urea. In the eight remaining treatments, corn ears were gradually replaced by processed poplar wood pellets (Bender-Heaney process) so that Treatment 9 consisted of processed wood and LPS-50 only. Increments of processed wood dry matter were approximately 10%/treatment. Weight gains and feed consumptions were recorded at 14-day intervals over the 98-day trial. Blood samples were taken for 3 consecutive days prior to slaughter. Digestive organs were observed for abnormalities and reticuloruminal contents were analyzed for pH, protein and volatile fatty acids. Overall daily gains (kg) and feed conversion ratios for Treatments 1–9 were 1.14, 5.97; 1.26, 5.81; 1.35, 6.01; 1.16, 6.73; 1.01, 7.31; 0.91, 8.05; 0.52, 11.44; 0.16, 27.23, respectively. There were no treatment effects on acetic, propionic and butyric acid concentrations in the reticulorumen. However, as the proportion of processed wood increased, there was a significant decrease (P

Urea transferred from the blood to the digestive tract of ruminants is potentially an important source of nitrogen for microbial growth in the reticulorumen and hind gut. Early attempts to assess the quantitative importance of urea transfer did not distinguish between its reticuloruminal and hind gut components. However, recent advances in tracer methodology have facilitated this partition, and a number of estimates have been made, principally using sheep on roughage diets. For some roughage diets, the rate of urea transfer to the rumen of sheep was small and was attributable to salivary urea, whereas for other diets substantial amounts of urea appeared to be entering the rumen across the rumen epithelium in addition to that carried in saliva. Regression analysis indicated that the rate of transfer of endogenous urea to the rumen of sheep given those diets was associated with the concentration of rumen ammonia and of plasma urea, and with the amount of organic matter digested in the rumen. Experimental evidence supporting the validity of this concept is discussed. Relationships are presented which show that the clearance of plasma urea to the rumen is inversely proportional to the concentration of rumen ammonia in both sheep and cattle, but that clearance is increased by the addition of grain or sucrose to the diet. It is concluded that transfer of urea across the rumen epithelium may contribute significantly to the nitrogen economy of the microorganisms, but the mechanism by which such transfer is controlled by the ruminant remains obscure.

The subject is reviewed with respect to the role of nutrient metabolism upon the regulation of ruminant feed intake. Chemical factors associated with changes in dietary or nutrient composition and their metabolism within the reticulorumen or animal body, or both, are emphasized. The importance of physical, physiological or metabolic, and sensory regulatory mechanisms are discussed in relation to their effects upon the formation of various metabolites known to be related to feeding. These include volatile fatty acids, amino acids, and blood glucose. Various tissues are discussed in relation to their relative importance for activation of a feedback signal associated with satiety. A general hypothesis is postulated for the integration of various factors, known to influence feed intake regulation, into a complex system.

Sustained release pellets were prepared containing chromic oxide (Cr2O3) as an indicator for digestibility studies using plaster of paris, portland cement, or china clay as binding agents. The pellets released the Cr2O3 at a constant rate in vitro but when placed in the reticulum of steers or wethers failed to mix uniformly with the reticulorumen contents. The percentage difference between the indicator method estimate and the total fecal collection method was 12.7 for estimating dry matter digestibility and 9.7 for energy digestibility. The percentage difference between the calculated and actual dry matter intake was 35.3. The sustained release pellets as prepared in this study are not satisfactory for administering the Cr2O3 indicator to estimate digestibility or feed intake.

Heidschnucken, an autochthonous sheep breed, were able to utilize a fibrous roughage diet of poor quality by increasing the volume of the reticulorumen and prolonging the retention time of particles. Under poor dietary conditions Merino Sheep, too, were able to supply the energy demands by increasing the volume of the fermentation chamber. Blackhead sheep showed no major ability of such an adaptation. Key words: Sheep, low quality, diets, rumen volume, retention time

In four wethers the kinetics of the liquid and particulate phases were estimated with Co-EDTA and Cr mordanted NDF, respectively. The rates of escape of these phases from the reticulorumen were closely related and amounted on average to 6.0 and 3.8%/h. Key words: Sheep, reticulorumen, retention time, feed particles

A method is described to determine hindgut CH4 production of sheep in an open circuit respiration apparatus by removing the contents of the reticulorumen through a large ruminal cannula. Preliminary results on two sheep fed lucerne (L) or a corn leaf sheath (CLS) diet demonstrated that measurement periods of one hour are suitable for this purpose. Key words: Sheep, methane production, hindgut

Level of hay intake did not affect fractional outflow rate of chromium-mordanted particles from the reticulorumen in lactating dairy cows fed three levels of hay and a fixed level of concentrate. Outflow rate of a rumen liquid phase marker was significantly affected by level of hay intake. Key words: Cattle, level of feeding, rate of passage