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Biomedical subjects

Y Aharoni

Publications and source records attributed to Y Aharoni.

27 records · Page 2Linked to original sources
PubMed1995

Dietary effects on fat deposition and fatty acid profiles in muscle and fat depots of Friesian bull calves.

Dietary effects on fat deposition, cholesterol level, and fatty acid profiles of muscle and fat depots in Friesian bull calves were evaluated in two trials. In Trial 1 (eight pens of seven Friesian bull calves), three levels of ME (10.4, 10.9, 11.7 MJ/kg of DM; diets L, M and H, respectively) were offered to three groups of calves throughout the entire experimental period. Calves of the fourth group were fed diet M for the first 80 d and diet L thereafter (Treatment ML). Calves were 185 +/- 15 d of age and 215 +/- 18 kg BW at the start of the trial and were slaughtered when they reached a predetermined equal degree of fatness, in a BW range of 480 to 580 kg, and an age range of 417 to 548 d. In Trial 2, four groups of calves (eight pens of seven Friesian bull calves) had free access to diets of the same ME (11.7 MJ/kg of DM) but that differed in either CP content (11.3 vs 13.4%) or had poultry litter substituted for part of soybean meal at the equivalent CP. Calves were 18o +/- 13 d of age and 240 +/- 19 kg BW at the start of the trial and were slaughtered after 232 +/- 11 d, at 508 +/- 22 kg BW. In both trials, dressing percentages and carcass percentages of kidney, pelvic, and cod fat depots were recorded at slaughter, and samples of the 12th rib longissimus muscle with its subcutaneous fat were obtained for lipid analyses. Increasing the ME concentration shortened the growing period and tended to increase carcass depot fat percentage.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1993

Lactational response of dairy cows to change of degradability of dietary protein and organic matter.

The effect of variable degradability of both OM and CP, incorporated at a constant ratio in diets of high yielding dairy cows (35 kg/d), was studied under commercial dairy herd conditions. Two diets containing 17% CP were formulated, including high (70%) and low (65%) protein degradability. The ratio of rumen-degradable OM to degradable protein was adjusted to 5:1 in both diets. Cows were assigned to treatments based on equal milk yield prior to trial, parity, and DIM. The trial lasted 7 wk: a reference week (wk 0), in which both groups were fed the high degradability diet, was followed by 6 experimental wk, in which group 1 was fed the high degradability diet and group 2 the low degradability diet. Cows on the low degradability diet consumed 1.2 kg more DM and yielded 1.5 kg/d more milk, .055 kg/d more milk protein, and .196 kg/d more milk fat. Percentages of milk protein (3.06 and 3.03) were similar, but fat (3.67 and 3.28) was higher for cows fed the low degradability diet. The results suggest that, when diets were formulated to balance rumen degradability of both OM and CP, 65% rather than 70% degradability of CP was advantageous for yields of milk and milk components.

Animal Feed↗
PubMed1991

A new approach to the quantitative estimation of nitrogen metabolic pathways in the rumen.

Rumen nitrogen metabolism values were estimated by the use of a single injection of 15(NH4)2SO4 into the rumen of sheep and consecutive 15N enrichment measurements in the rumen ammonia pool, rumen non-NH3-N (NAN) pool, rumen purine pool and blood urea-N (BUN) pool for a period of 24 h. Synthesis and degradation of N compounds in the rumen and passage of N to and from the rumen were evaluated on a chemical rather than a microbial basis; microbial fractions were not separated. This model was examined in two experiments. In Expt 1 a ram (55 kg) was given a semi-synthetic diet (1067 g dry matter (DM), 22.8 g N) in which soya-bean meal provided over 90% of the N. In Expt 2, two rams (45 kg) were given in three consecutive periods a semi-synthetic basal diet containing: (1) roasted soya-bean meal (SBM, 725 g DM, 14.8 g N/d); or (2) fishmeal (FM, 728 g DM, 15.5 g N/d); or (3) raw soya-bean meal (RSBM, 724 g DM, 13.8 g N/d). In all these rations, the main protein source provided over 90% of the N. In Expt 1, 68.3% of N intake was degraded directly to NH3 in the rumen, 21.2% escaped rumen degradation and 10.5% was incorporated into stable N compounds in the rumen. Net NH3 transfer to the blood was 30.4%, NH3 flow from the rumen was 6.6% and rumen NAN output was 63% of N intake. In Expt 2, rumen NAN output was larger (7.67, 14.36 and 8.89 g N/d for diets containing SBM, FM and RSBM respectively; P less than 0.05) and net NH3 loss to the blood was smaller (6.1, 0.39 and 4.17 g N/d for diets SBM, FM and RSBM respectively; P less than 0.05) for diet FM as compared with the soya-bean diets. The percentage of rumen NAN that was synthesized from NH3 was larger for diet RSBM (36.4, 40.3 and 49.1 for diets SBM, FM and RSBM respectively; P less than 0.05) than for the other two rations. NH3 pool sizes (g N) were 0.463, 0.385 and 0.301 for diets SBM, FM and RSBM respectively (P less than 0.05), while their hourly turnover rates were 15.8, 26.1 and 5.12 for diets SBM, FM and RSBM respectively (P less than 0.01), indicating no correlation between pool size and its turnover rate.(ABSTRACT TRUNCATED AT 400 WORDS)

Ammonia↗
PubMed1991

Use of nitrogen-15 determinations of purine nitrogen fraction of digesta to define nitrogen metabolism traits in the rumen.

A method for direct purine N isolation and determination was modified from the method of Zinn and Owens for rapid determination of purines. By this method, N derived from purines in digesta was measured and collected for 15N determinations. Measurements of purine N in 33 samples of ruminal contents and duodenal digesta of sheep and goats were compared with purine determinations in the same samples. The results showed that essentially all the N in the purines that could be isolated by the Zinn and Owens procedure also could be detected by N isolation and determination. Determinations of 15N in the NH3 N, NAN, and purine N fractions in a continuous culture in vitro showed significant differences in the 15N enrichment curves between diets based on either roasted or raw soybean meal.

Animals↗
PubMed1988

Effect of ratio of roughage concentrate on glucose-induced heat production in sheep rumen fluid in vitro.

The effect of ration on heat of glucose fermentation in sheep rumen fluid was investigated. Heat production was measured in a semiadiabatic calorimeter. In trial 1, the effect of glucose (.4 to 6.4 mg) on fermentative heat production was determined in rumen fluid from sheep fed 25 or 100% roughage diet. Heat of glucose fermentation decreased with increase in glucose dose in both diets. Maximal heat of glucose fermentation in both diets agreed with stoichiometric calculations. However, at 6.4 mg glucose, maximal heat was 18 kcal/mol in the 25% roughage diet and 14 kcal/mol in the 100% roughage diet. Purine N and maximal rate of heat production were not affected by diet type. In trial 2, the effect of glucose (1.6 and 6.4 mg) on fermentative heat production was determined in rumen fluid from sheep fed 25, 50, 75, and 100% roughage. In addition, fermentation pattern was measured in donors of the rumen fluid. Heat of glucose fermentation was positively correlated with organic matter digestibility and negatively correlated with rumen pH and acetate concentration. These observations indicate that in addition to the effect of roughage on the fermentation pattern, supplemental adaptation may occur, as indicated by the reduction in the heat of glucose fermentation.

Animals↗
PubMed1977

Differential counteraction of ethylene effects by gibberellin a(3) and n(6)-benzyladenine in senescing citrus peel.

Treatment of mature citrus fruit (Citrus sinensis) with ethylene induced rapid chlorophyll destruction, a rise in respiration, a release of free amino acids, an accumulation of reducing sugars, and an appearance of phenylalanine ammonia lyase activity. Gibberellin A(3) (GA(3)) and N(6)-benzyladenine (BA) opposed the effects of ethylene on chlorophyll, amino acids, and to a lesser extent, reducing sugar levels. The ethylene-induced respiratory rise was only slightly modified by GA(3) and BA. Phenylalanine ammonia lyase activity was not affected by GA(3).The antagonism between ethylene and the senescence-delaying regulators GA(3) and BA seems to operate mainly within the chloroplast, but might not be confined to this compartment. The accumulation of reducing sugars exhibits the antagonism although it is not apparently related to the chloroplast.

Journal Article↗
PubMed1968

Respiration of oranges and grapefruits harvested at different stages of development.

Young and unripe oranges and grapefruits stored at 15 degrees or 20 degrees evidenced shortly after harvest a marked increase in respiratory rate, and then a well-defined maximum which was followed by a decrease.Ethylene production by oranges (measured by the manometric method) was observed, with curves parallel to the respiratory curves.The respiratory upsurge was accompanied by color changes typical of maturity in the above fruits, and by abscission of stem-ends.When fruit was harvested close to or at commercial maturity, it evidenced a gradual respiration decrease without any upsurge. No ethylene production was detected in oranges of this stage.

Journal Article↗