Biomedical subjects

J High

Publications and source records attributed to J High.

5 recordsLinked to original sources

PubMed2002

Use of milk urea nitrogen to improve dairy cow diets.

The hypothesis of this field study was that providing farmers with information regarding their herd's milk urea nitrogen (MUN) would result in more accurate feed management and a change in MUN toward target values. All dairy herd bulk tanks (n = 1156) in the Maryland and Virginia Milk Producers' Cooperative were tested for MUN each month for six months ending in May 1999. Farmers (n = 454) who returned a survey were provided with the results of their MUN analysis each month along with interpretive information. Survey results indicated that most (89.5%) dairy farmers did not routinely use MUN prior to participating in the project, but most (88%) extension agents and nutritionists in the region recommended it. The average MUN across all farms in the study increased in the spring, but the increase was 0.52 mg/dl lower for farmers receiving MUN results than for those who did not participate in the program. Farmers who indicated they increased dietary crude protein (CP) due to low MUN started with MUN values that were 3 mg/dl below target but ended with target values. Farmers who indicated that they decreased CP due to high MUN began the project with high MUN but decreased it by 1 mg/dl compared to non-participating farmers. At the end of the project, 30% of farmers responding to a follow-up survey indicated they would use MUN analysis in the future. Providing MUN results and interpretive information to farmers was documented to change feeding practices and subsequent MUN results.

Animal Feed↗

PubMed2002

Dairy herd management practices that impact nitrogen utilization efficiency.

Improving the efficiency of feed N utilization by dairy cattle is the most effective means to reduce nutrient losses from dairy farms. The objectives of this study were to quantify the impact of different management strategies on the efficiency of feed N utilization for dairy farms in the Chesapeake Bay Drainage Basin. A confidential mail survey was completed in December 1998 by 454 dairy farmers in PA, MD, VA, WV, and DE. Nitrogen intake, urinary and fecal N, and efficiency of feed N utilization was estimated from survey data and milk analysis for each herd. Average efficiency of feed N utilization for milk production by lactating dairy cows (N in milk/N in feed x 100) was 28.4% (SD = 3.9). On average, farmers fed 6.6% more N than recommended by the National Research Council, resulting in a 16% increase in urinary N and a 2.7% increase in fecal N. Use of monthly milk yield and component testing, administration of bovine somatotropin (bST), and extending photoperiod with artificial light each increased efficiency of feed N utilization by 4.2 to 6.9%, while use of a complete feed decreased efficiency by 5.6%. Increased frequency of ration balancing and more frequent forage nutrient testing were associated with higher milk production, but not increased N utilization efficiency. Feeding protein closer to recommendations and increasing production per cow both contributed to improving efficiency of feed N utilization.

Animal Nutritional Physiological Phenomena↗

PubMed1986

Antihypertensive effects of 12 beta adrenoceptor antagonists in conscious spontaneously hypertensive rats: relationship to changes in plasma renin activity, heart rate and sympathetic nerve function.

Twelve beta adrenoceptor antagonists were examined for their effects on mean blood pressure (MBP), heart rate (HR), plasma renin activity (PRA) and sympathetic nerve function in spontaneously hypertensive rats (SHR). The selected drugs included cardioselective agents (acebutolol, atenolol and metoprolol), agents with intrinsic sympathomimetic activity (oxprenolol, acebutolol, alprenolol and pindolol) and agents with local anesthetic activity (propranolol, oxprenolol, acebutolol, alprenolol and labetalol). All 12 beta adrenoceptor antagonists, administered once daily for 4 days (30 mg/kg p.o.), significantly decreased MBP of SHR. This reduction in MBP was dissociable from both reductions in HR as well as peripheral beta adrenoceptor blockade. In addition, the onset of MBP reduction was slower than the onset of beta adrenoceptor blockade and became greater with duration of treatment. PRA activity was significantly and markedly reduced by both bunolol and metoprolol shortly after dosing at a time when HR was significantly reduced but MBP was not. Conversely, at a time when MBP was significantly reduced by both bunolol and metoprolol, PRA and HR were found to be normal. The changes in HR and PRA were correlated with peripheral beta adrenoceptor blockade but changes in MBP were not. Bunolol, metoprolol and propranolol had no consistent inhibitory effect on pressor responses to nerve stimulation in pithed SHR, although positive chronotropic responses to norepinephrine, tyramine, dimethylphenylpiperazinium and angiotensin I and II were significantly and markedly reduced. It is concluded that beta adrenoceptor antagonists, as a class, reduce MBP of conscious SHR, provided that sufficient time is allowed for this observation to occur. Furthermore, the reduction in MBP caused by beta adrenoceptor antagonists is unrelated to acute beta adrenoceptor blockade, changes in HR, reductions in PRA or inhibition of sympathetic nerve function. Finally, cardioselectivity, intrinsic sympathomimetric activity and local anesthetic activity are not required for the antihypertensive activity of these agents.

Acebutolol↗

PubMed1984

The effect of short-term obstruction on urinary bladder function in the rabbit.

The effect of short term partial obstruction on urinary bladder function was studied in rabbits. After 1 week of partial bladder obstruction, the bladders were significantly hypertrophied with a mass over 9 times that of control bladders. The obstruction resulted in a marked decrease in both intracellular ATP and muscarinic receptor density. In vitro response of isolated smooth muscle strips from the obstructed bladder body to cholinergic stimulation was only 50 per cent of the response of control bladders. The obstructed bladder was able to expel only 28 per cent of its volume whereas control bladders expelled 100 per cent of their volume. The results of these studies demonstrate the rapid nature of the response of the bladder to chronic obstruction. Within 1 week frank hypertrophy and significant defects in the contractile ability of the bladder were evident.

Adenosine Triphosphate↗

PubMed1982

Metabolic and contractile effects of anoxia on the rabbit urinary bladder.

The in vitro metabolic and contractile effects of anoxia and glucose deprivation on the rabbit urinary bladder were studied. The exposure of isolated strips of rabbit urinary bladder to a glucose deficient medium equilibrated with nitrogen rather than with oxygen resulted in 1) a rapid decrease in baseline tension, 2) a progressive decrease in the intracellular concentration of adenosine 5'-triphosphate (ATP) and progressive increases in the concentrations of adenosine 5'-monophosphate and adenosine 5'-diphosphate, 3) a rapid decrease in the ability of bethanechol to stimulate contractility, and 4) the inability of bethanechol to maintain a sustained increase in contractile force. Recovery from a 60-minute exposure of bladder strips to anoxia was characterized by a rapid recovery of the ability of the bladder to respond to bethanechol (50 per cent recovery occurring within 15 minutes) and a slightly slower recovery of the intracellular ATP level. Both the contractile response to bethanechol and the intracellular concentration of ATP returned to control levels within 60 minutes after the termination of anoxia.

Adenosine Diphosphate↗