All-Order Coulomb Corrections to Delbrück Scattering above the Pair-Production Threshold.

We report calculations of Delbrück scattering that include all-order Coulomb corrections for photon energies above the threshold of electron-positron pair creation. Our approach is based on the application of the Dirac-Coulomb Green's function and accounts for the interaction between the virtual electron-positron pair and the nucleus to all orders in the nuclear binding strength parameter αZ. Practical calculations are performed for the scattering of 2.754 MeV photons off plutonium atoms. We find that including the Coulomb corrections enhances the scattering cross section by up to 50% in this case. The obtained results resolve the long-standing discrepancy between experimental data and theoretical predictions and demonstrate that an accurate treatment of the Coulomb corrections is crucial for the interpretation of existing and guidance of future Delbrück scattering experiments on heavy atoms.

Chickpeas as a protein and energy supplement for high producing dairy cows.

Thirty lactating Holstein cows were randomly assigned to one of three diets to evaluate chickpeas as dietary supplement from wk 4 to 16 postpartum. Diets contained chickpeas at 0, 50, and 100% of the concentrate DM in place of corn and soybean meal. Total mixed diets, fed individually, contained concentrate, corn silage, and alfalfa hay at 52, 32, and 16% of DM. Milk yield (34.5, 35.1, 35.7 kg/d) was higher for cows fed 100% chickpeas than 0% chickpeas. Milk medium-chain (C12 to C16) fatty acids (53.8, 48.6, 45.5 g/100 g fat), milk long-chain (C18) fatty acids (29.4, 35.0, 38.8 g/100 g fat), and milk protein (3.20, 3.09, 2.96%) differed for all three diets. Ruminal acetate: propionate (2.0, 2.0, 2.4) was highest for cows fed 100% chickpeas. Total essential amino acid concentration in blood serum (105.3, 95.9, 89.4 mumol/dl) was higher for cows fed 0% chickpeas than 100% chickpeas. Lactational responses are discussed with respect to increased intake of fat, increased degradability of dietary protein, and decreased plasma essential amino acids.

Ration digestibilities and ruminal characteristics in steers fed chickpeas.

Twenty-four Holstein steers were used in a 5-d digestion trial to evaluate chickpeas as a substitute for corn and soybean meal. Total mixed diets contained (dry basis) 51% concentrate mix, 33% corn silage, and 16% alfalfa hay. Concentrate mixes contained 0, 50, and 100% chickpeas in place of corn and soybean meal. Ad libitum intakes of DM were not different between diets. Digestibilities of DM, NDF, ADF, hemicellulose, cellulose, lignin, and gross energy were not different among diets. Digestibilities of protein, fat, and ash were greater for steers fed 100% chickpeas than 0% chickpeas. Fecal N was lower and absorbed N was higher for steers fed 100% chickpeas. Ruminal acetate and acetate:propionate ratio were lower and ruminal propionate was higher for all steers fed diets containing chickpeas. Ruminal ammonia and pH were similar for all treatments.

Lactational response to soybean meal, heated soybean meal, and extruded soybeans with ruminally protected methionine.

Seventy-three high producing Holstein cows were arranged in a 3 X 2 factorial to evaluate three protein supplements (soybean meal, heat-treated soybean meal, and extruded blend of soybeans and soybean meal) without or with 15 g/head/d of ruminally protected DL-methionine during wk 4 through 16 postpartum. Total mixed diets contained (DM basis) 30% corn silage, 15% alfalfa hay, and 55% of the respective concentrate mix. Milk production was higher when cows were fed either heated soybean product instead of soybean meal. Methionine supplementation increased production when fed with soybean meal (32.2 and 33.8 kg/d) but not when fed with heat-treated soybean meal (34.5 and 33.0 kg/d) or extruded soybeans (36.2 and 34.4 kg/d). Milk fat percentages were lower with extruded soybeans (3.01, 2.93, and 2.66) and were similar without (2.83) or with (2.90) supplemental methionine. Milk protein percentages were highest when fed soybean meal, lowest with extruded soybeans (3.02, 2.92, and 2.87), and higher with supplemental methionine (2.91 and 2.96). Dry matter intake was higher when fed supplemental methionine (20.0 and 21.3 kg/d). Production of milk in early lactation high producing dairy cows was increased by supplementing a soybean meal diet with ruminally protected methionine or by replacing the soybean meal with heat-treated soybean meal, soybeans, or a mixture of the two.

Chickpeas as a substitute for corn and soybean meal in growing heifer diets.

Twelve Holstein heifers (average weight 270 kg) were randomly assigned to one of four diets to evaluate the feeding value of chickpeas. Total mixed diets were composed of (dry matter) 40% concentrate mix, 24.5% chopped alfalfa hay, and 35.5% corn silage. Concentrate mixes contained 0, 25, 50, and 75% chickpeas in place of corn and soybean meal. Diets were fed individually for 80 d. Average daily gains (.98, 1.13, 1.14, and .95 kg) were higher for heifers fed 25 and 50% chickpeas than for those fed 0 and 75% chickpeas. Feed per gain (4.72, 4.05, 3.65, and 4.01 kg/kg) was lower for all diets containing chickpeas. Dry matter intake was lowest for heifers fed 75% chickpeas, and dry matter intake as percent of body weight was similar for all groups. Ruminal ammonia, pH, total volatile fatty acid concentrations, and ratio of acetate to propionate were similar for all diets. Serum urea and rumen parameters displayed no trends between diets. Chickpeas were an acceptable replacement for corn and soybean meal in growing heifer diets.

Responses to controlling gastrointestinal parasitism in dairy cattle.

Sixty-eight Holstein heifers, paired on milk production potential and season of birth, were randomly assigned within pairs to a control or treatment group to evaluate the effect of raising replacement heifers on a prophylactic anthelmintic regimen. The anthelmintic, thiabendazole (6.6 g/100 kg body weight), was administered orally as a paste at 2.5, 3.5, 6, 9, and 14 mo of age and at parturition. The control group received no thiabendazole. Fecal samples were collected from both groups at the time of thiabendazole treatment. Days to first service were 457.1 and 457.8 for the control and treatment groups. There were no differences in services per conception or days to first calving. Nematode eggs per 5 g of feces were similar at 2.5 mo (.6 and .8), 3.5 mo (38.6 and 22.4), 6 mo (40.2 and 43.1), 9 mo (39.0 and 22.4), 14 mo (55.2 and 22.4), or parturition (16.5 and .4). There were no differences in body weight changes over the first 18 mo of age. Subsequent first lactations were similar (9422 and 8710 kg 305-d mature equivalent, for twice daily milking) as was actual milk production for the first 120 d of lactation. Under these environmental conditions and apparently low parasitism in this herd, thiabendazole did not substantially influence nematode egg count and had no effects on body weight gains or milk production.

Variability of Milk Components in 1705 Herds.

Biweekly herd milk samples collected for a 1-year period (January 1, 1984 to December 31, 1984) from 1705 herds in eastern South Dakota, western Minnesota and northwestern Iowa were analyzed to evaluate milk components as factors considered in milk pricing programs. The average composition was 3.71% fat, 8.64% solids-not-fat (SNF), 3.28% protein, 12.35% total solids (TS) and 1.8 × 105 CFU/ml (aerobic plate count). Fat was the most variable (8.4% coefficient of variation) milk component, followed by protein, TS and SNF (6.3, 4.1 and 3.4% coefficient of variation, respectively). The concentration of fat, SNF, protein and TS in milk was lowest in July and August and highest during November through March. Correlation coefficients (r) for fat vs. SNF, protein and TS were 0.40, 0.64 and 0.84, respectively, for SNF vs. protein and TS were 0.70 and 0.83, respectively, and for protein vs. TS was 0.79. Grade A milk had lower aerobic plate counts (3.2 × 104 and 3.0×105 CFU/ml), higher % SNF (8.68 and 8.60), and higher % TS (12.39 and 12.31) than manufacturing grade milk. There were no differences in % fat (3.71 and 3.72) and % protein (3.28 and 3.28) between Grade A and manufacturing grade milks. Some cooperatives and milk plants are paying a SNF premium (8.75% base), stating that an 8.75% SNF is equivalent to a 3.2% protein content. This occurred in herds with <3.0% fat; however, for herds producing ≥3 and ≤4% fat, 8.75% SNF was equivalent to 3.31% protein, whereas for herds producing >4% fat, 8.75% SNF was equivalent to 3.46% protein. Solids-not-fat component pricing has the potential to be compared to protein pricing if producer grade, seasonal period and fat content of herd milk are considered.

Metabolism of orally administered [3H]ergocalciferol and [3H]cholecalciferol by dairy calves.

Concentrations of ergocalciferol, cholecalciferol, and their metabolites in plasma were determined after a single oral dose of [3H]ergocalciferol or [3H]cholecalciferol was given to 95- to 105-kg Jersey bull calves. One group (three calves) was given 365 muCi of [3H]ergocalciferol (1.2 Ci/mmol) per calf, and the other group (three calves) was given 365 muCi of [3H]cholecalciferol (1.2 Ci/mmol) per calf. Fourteen blood samples were taken from each calf during the 3 weeks after administration. Total plasma radioactivity was highest at 80 hours in both groups (8400 dpm/ml and 4600 dpm/ml in the [3H]cholecalciferol- and [3H]ergocalciferol-treated calves, respectively). For determination of the time-dependent appearance and disappearance of plasma vitamin D and vitamin D metabolites, the plasma 3H-labeled steroids were extracted and separated by high-performance liquid chromatography. In both groups, [3H]vitamin D peaked at 24-48 hours and was the predominant radioactive form in plasma 10-15 hours after dosing. After 15 hours, 25-[3H]hydroxyvitamin D became the predominant labeled metabolite, reaching its maximal concentration between 48 and 96 hours. Concentrations of 25-[3H]hydroxycholecalciferol were about twice those of 25-[3H]hydroxyergocalciferol. The appearance/disappearance profile of 25,26-[3H]dihydroxycholecalciferol and 1,25[3H]hydroxycholecalciferol resembled that of 25-[3H]hydroxycholecalciferol.(ABSTRACT TRUNCATED AT 250 WORDS)