R. A. Britton

Level of nutrition and visceral organ size and metabolic activity in sheep

Thirty-two crossbred wether lambs (initial live-weight 31 kg) were fed on a diet (metabolizable energy (ME) 12.8 MJ/kg) ad lib. (ADLIB) or restricted to maintain body-weight (MAINT) for a 21 d period. On days 0, 7, 14 and 21, four lambs per treatment were slaughtered, visceral organs weighed and tissues sampled. During the 21 d period, ME intake in ADLIB lambs increased quadratically with an average rate of live-weight gain of 425 g/d. In MAINT lambs, live weight (30 kg) was maintained, and daily ME intake (kJ/kg empty body-weight (EBW)0.75) declined (P less than 0.01) quadratically with time. Weights of liver, stomach and small intestines as a percentage of EBW were increased in ADLIB lambs and decreased by 10-33% in MAINT lambs (treatment x day, P less than 0.01). In vitro liver oxygen consumption was not affected by level of feed intake. Estimates of whole-liver O2 consumption (mmol O2/d per kg EBW) increased in ADLIB lambs and were relatively constant in MAINT lambs. These findings suggest that level of feed intake changes the relative proportion of visceral organs to body mass. In addition, the effect of level of feed intake on changes in the relative contribution of visceral organs to whole-body metabolic rate appears to be primarily a result of differences in organ size rather than tissue-specific metabolic activity.

Effect of level of nutrition on splanchnic blood flow and oxygen consumption in sheep

The objective of the present study was to measure changes in splanchnic blood flow and oxygen consumption in sheep fed on a high-concentrate diet ad lib. (ADLIB) or an amount sufficient to maintain body-weight (MAINT) for 21 d. Eleven ram lambs were surgically implanted with chronic indwelling catheters in the portal, hepatic and mesenteric veins and mesenteric artery to measure blood flow and net O2 flux through the liver and portal-drained viscera (PDV). During the 21 d period, PDV (P less than 0.05) and liver (P less than 0.01) blood flow increased in ADLIB and decreased in MAINT lambs (treatment x day, linear). After 21 d, O2 consumptions in PDV and liver of MAINT lambs were 37 and 63% lower than in ADLIB lambs. In the control period, total splanchnic tissues represented an average of 52% of whole body O2 consumption. After 21 d, the relative contributions of PDV and liver to whole-body O2 consumption were 28 and 41% in ADLIB and 19 and 22% in MAINT lambs respectively. Allometric regression variables indicate that liver O2 consumption responds more rapidly to changes in metabolizable energy intake than portal O2 consumption. These results indicate that blood flow and O2 consumption in both PDV and liver are related to level of nutrition. Furthermore, splanchnic tissues represent a significant component of whole-body O2 consumption that is subject to manipulation by level of nutrition.

In vitro starch disappearance procedure modifications

Four in vitro experiments evaluated the effects of ruminal fluid inoculum:artificial saliva ratios, grinder type, grind size, and diet of ruminal fluid donor on in vitro starch disappearance. Experiment 1 examined rates of starch disappearance and coefficients of determination obtained by linear regression of starch disappearance using five grain sorghum (Sorghum bicolor (L.) Moench) lines, a corn (Zea mays L.) control, and a wheat (Triticum aestivum L.) control. Grains were incubated for 4, 8, 12, 16, and 20 h with inoculum varying in proportion of ruminal fluid and artificial saliva (1:1, 1:2, 1:3, and 1:4). In vitro rates of starch disappearance and coefficients of determination were similar for the 1:2, 1:3, and 1:4 inoculum dilutions and were higher (quadratic, P 0.10) by grain type fed; however, absolute rates of digestion varied among inoculate sources. Grinder, grind size, and ruminal fluid inoculum:artificial saliva ratios affected rate of starch disappearance in samples digested in vitro. Diet of ruminal fluid donor affected the rate of starch digestion, but not the relative ranking of the grains. If rates are to be compared across in vitro runs for different grains, these processing and dietary factors must be kept constant.

Relevance of Bypass Protein to Cattle Feeding 13

Summary The primary cost for supplemental protein is for that portion of the protein which escapes (or bypasses) rumen digestion. Therefore, economical use of protein sources requires good estimates of protein bypass. This can be done by intestinal digesta collection or by animal growth, in order to adequately interpret estimates of bypass from growth studies, protein must be shown to be the first limiting nutrient and protein sources must be compared at levels below the animal’s requirement. Growth studies conducted using these criteria give bypass estimates similar to intestinal collection trials. High bypass protein sources can be effectively used in supplement formulations. Through the use of soybean meal equivalent values, supplements equivalent in feeding value to soybean meal can be formulated. Urea is used as an inexpensive source of rumen ammonia thus reducing the cost of the supplement containing bypass protein. Supplements containing bypass protein and urea can be supplied to producers at a lower cost than more traditional “all natural” protein supplements.

Protein supplementation of ammoniated roughages. III. Corncobs supplemented with a blood meal-corn gluten meal mixture--steer studies.

Two factorial experiments were conducted to investigate site and extent of organic matter (OM) digestion, nitrogenous fractions flowing at the abomasum and rates-of-passage in steers fed 0, 2 or 4 g NH3/100 g dry matter of treated corncobs supplemented with either a corn or a blood meal-corn gluten meal (BM-CGM) supplement. Rumen and total tract OM digestion coefficients were quadratically increased (P less than .05) and dietary N was quadratically increased (P less than .07) due to the main effect of ammonia. The main effect of protein supplement increased (P less than .05) postruminal OM digestibility, nonammonia N and dietary-N flow. Quadratic protein X ammonia interactions were noted for fluid flow, total-N flow, total amino acid flow and ammonia-N flow. Linear protein X ammonia interactions were noted for bacterial-N flow, which appeared to indicate that N utilization of the ammoniated corn-cob was improved by the inclusion of BM-CGM in the diet. Diet dry matter intake, fluid volume, rate of fluid passage, particulate mass and rate of particulate passage in rumen-fistulated steers were unaffected by either main effect. However, rumen fluid pH of steers fed BM-CGM was lower than that from steers fed the corn supplement.

In vitro rates of oxidation and gluconeogenesis from l(+)- and d(−)lactate in bovine tissues☆

Slices of bovine kidney cortex, liver, heart and sternomandibularis muscle actively metabolized D- and L-lactate. Rates of D-lactate oxidation were greatest in kidney cortex followed by heart and liver with muscle exhibiting the lowest rates. L-lactate oxidation was greatest in kidney cortex followed by heart with liver and muscle exhibiting similar rates. Rates of oxidation of gluconeogenesis were similar for D- and L-lactate at 0.1 mm lactate but D utilization, as a percent of L, decreased as substrate concentrations increased to 50 mM. Bovine tissues appear to possess significant potential for D(-)lactate utilization. Estimates of this and possible interactions are discussed.

Effect of protozoa and urea level on in vitro starch disappearance and amylolytic activity of ruminal microorganisms

Abstract In vitro experiments were conducted to study the effects of protozoa on starch fermentation and amylolytic activity of ruminal bacteria and protozoa. The first experiment consisted of a randomised complete block design with a 3 × 2 × 5 factorial arrangement of treatments. Treatments were grain source (corn, high moisture corn or grain sorghum), inoculum source (a mixed ruminal population or one free of protozoa) and urea addition (0, 5, 10, 20 or 30 mg g −1 of grain). An interaction ( P P P P P P P > 0.01) in amylase specific activity (units ml −1 of protein) was observed for protozoa (0.0802), bacteria (0.0472), and a mixed population (0.0435). The contribution of protozoa on the in vitro starch digestion may be dependent on the ammonia N concentrations.

Ruminal fermentation and in situ starch digestion with high moisture corn, dry rolled grain sorghum or a mixture of these grains

An experiment was conducted to study the effects of feeding mixtures of high moisture corn (HMC) and dry-rolled grain sorghum (DRGS) on ruminal fermentation and site and the extent of starch digestion. Three ruminally fistulated steers were used in a replicated Latin square design. Dietary grain treatments were:(1) 100% HMC;(2) 67% HMC:33% DRGS; and (3) 100% DRGS. Starch and DM intake (P<0.01), and in situ rate of starch disappearance of DRGS (P<0.05) increased linearly as sorghum was added to the diet. Entodinium counts and total amylolytic activity tended to be higher (quadratic, P=0.20) in the mixture. VFA and molar proportion were not affected by the treatments. No associative effects were detected in ruminal starch digestion. Ruminal protozoa numbers were increased when DRGS and HMC were combined.