Maturity of coastal bermudagrass and alfalfa affects ruminal in situ and total tract dry matter and phosphorus disappearance in cannulated steers

Variability of phosphorus (P) availability among forage species and plant maturity is largely ignored when formulating ruminant diets. To determine if variability in P availability changes with forage species and/or maturity, ruminal in situ and total (ruminal+post-ruminal) dry matter (DM) and phosphorus disappearance (PD) from alfalfa (ALF; Medicago sativa) and coastal bermudagrass (CB; Cynodon dactylon) harvested at four stages of maturity was measured in cattle. Forages were hand clipped at 14, 21, 28 and 35 days after first cutting. Ruminal in situ DM disappearance (DMD) and PD were measured after 24 h ruminal incubation in Dacron bags. Total tract DMD and PD were measured using the mobile nylon bag technique. Disappearance of DM and P were greater (p≤0.05) in the rumen than post-rumen for both species regardless of maturity; however, 80 g PD/kg DM in 35-day ALF (9% of total PD) and 224 g PD/kg of 35-day CB (38% of total PD) occurred post ruminally. Alfalfa DM disappeared to a greater (p ≤ 0.05) extent than CB and showed 5% greater total tract PD at 14 days and 13% more at 35 days compared to the grass. Alfalfa total tract PD decreased (p ≤ 0.05) 5.4% from 14- to 35-day maturity while the decrease was far greater for CB, 12.4%. Results from this study indicate that ruminant nutritionists should take into account forage species and maturity when calculating PD in diets; these details can be used to aid in formulating more precise rations that reduce fecal-phosphorus excretion into the environment.     

Depletion of intramuscularly and subcutaneously injected procaine penicillin G from tissues and plasma of yearling beef steers.

Withdrawal periods required when doses of 24,000 IU and 66,000 IU of procaine penicillin G/kg body weight were administered to yearling beef steers by intramuscular injection daily for five consecutive days were investigated. These dosages are in excess of product label recommendations, but are in the range of procaine penicillin G dosages that have been administered for the treatment of some feedlot bacterial diseases. The approved dose in Canada is 7,500 IU/kg body weight intramuscularly, once daily, with a withdrawal period of five days. Based on the tissue residue data from this study, the appropriate withdrawal period is ten days for the 24,000 IU/kg body weight dose and 21 days for the 66,000 IU/kg body weight dose when administered intramuscularly to yearling beef steers. In a related study, 18 yearling beef steers received 66,000 IU of procaine penicillin G/kg body weight administered by subcutaneous injection, an extra-label treatment in terms of both dose and route of administration, typical of current practice in some circumstances. Deposits of the drug were visible at subcutaneous injection sites up to ten days after injection, with more inflammation and hemorrhage observed than for intramuscular injections of the same dose. These results suggest that procaine penicillin G should not be administered subcutaneously at high doses; and therefore a withdrawal period was not established for subcutaneous injection.     

Branched-chain amino acids for growing cattle limit-fed soybean hull-based diets.

Five ruminally cannulated Holstein steers (176 kg) were used in a 5 x 5 Latin square to evaluate the effects of branched-chain AA supplementation on N retention and plasma AA concentrations of steers. Steers were limit-fed (3.0 kg/d of DM) twice daily diets low in ruminally undegradable protein (72% soybean hulls, 19% alfalfa, 5% molasses, and 4% vitamins and minerals). Acetate (400 g/d) was continuously infused into the rumen. Treatments were continuous abomasal infusions of 1) 115 g/d of a mixture of 10 essential AA designed to exceed the steers' requirements (10AA), 2) 10AA with Leu removed, 3) 10AA with Ile removed, 4) 10AA with Val removed, and 5) 10AA with all three branched-chain AA removed. Experimental periods were 7 d, with 3 d for adaptation to treatments and 4 d for total fecal and urinary collections for N balance. Blood samples were collected 5 h after feeding on d 7. Retained N decreased in response to removal of Leu (P < 0.06), Val (P < 0.05), or all three branched-chain AA (P < 0.05). Plasma Leu concentrations decreased (P < 0.05) in response to removal of Leu and all three branched-chain AA. Plasma Ile concentrations decreased (P < 0.05) in response to removal of Ile and all three branched-chain AA but increased (P < 0.05) in response to removal of Leu. Plasma Val concentrations decreased (P < 0.05) in response to removal of Val and all three branched-chain AA but increased (P < 0.05) in response to removal of Leu. Responses in N balance and plasma AA concentrations of growing cattle limit-fed soybean hull-based diets demonstrate limitations in the basal supply of Leu and Val but not Ile provided that supplies of all other essential AA are met.     

Correlation between structure and phytotoxic activities of nitrodiphenyl ethers

Various nitrodiphenyl ethers were assayed using a cell-free photosynthetic system and intact microalgae to approach a correlation between chemical structure and their effect upon three biochemical processes: (1) linear photosynthetic electron transport (Hill reaction); (2) photophosphorylation (energy-transfer inhibition by affecting the ATP synthetase); and (3) light-induced peroxidative degradation of thylakoid lipids (formation of short-chain hydrocarbons). Diphenyl ethers with a p-nitro group at one phenyl ring and one or two chloro substituents at the other exhibit energy-transfer inhibition. Analogs with different substituents are ineffective. A moderate electron-transport inhibition is seen with almost all derivatives. The most obvious phytotoxic effect is the occurrence of light-induced peroxidation (of polyunsaturated fatty acids) by p-nitro- and p-nitrosodiphenyl ethers. Substituents such as -OCH₃, -OC₂H₅, -NHC₂H₅, or -COOCH₃, -CONHCH₃ next to the p-nitro group enhance peroxidative activity and are apparently important for stabilization and/or reactivity of a diphenyl ether radical originating through photosynthetic electron flow. Activity is further enhanced by substituents with positive Hammett parameters in ortho or para positions at the phenyl ring not carrying the nitro group.     

Bovine Viral Diarrhea Virus in Swine: Characteristics of Virus Recovered from Naturally and Experimentally Infected Swine

A noncytopathogenic field strain of bovine viral diarrhea virus (BVDV) was isolated from an Iowa farm brood sow and from her hysterectomy-derived, colostrum-deprived (HDCD) piglets. This field isolant was fully virulent for a neonatal calf. The NADL strain of BVDV was passaged through a series of HDCD piglets with no resultant loss of virulence for neonatal calves. Most of the BVD viral isolants recovered from pigs had been changed from a cytopathogenic biotype to a noncytopathogenic biotype. Circumstantial evidence points to swine as “carrier” hosts of BVDV.     

Comparative study of various Chlamydia strains--preliminary study (author's transl)]

The chlamydia order comprises two species (Chlamydia trachomatis and Chlamydia psittaci) which are the only ones which can be rigorously differentiated with experimental criteria. However, the clinical study of chlamydia demonstrates the existence of various syndromes due to pathogenic agents. Some observations also seem to indicate the possibility of antigenic differences between isolated strains, during abortions, among small ruminants.We have entered upon a comparative study of various Chlamydia psittaci strains in order to look for objective criteria of differentiation of the strains extracted from small ruminants from those which were isolated from other animal species. Chlamydia taken from samples of ovine and caprine origin by direct isolation on embryonated egg or on cellular cultures were also compared by the following methods: seroneutralization on embryonated eggs and on cell cultures, characteristics of the plaques on cell cultures, crossed-immunofluorescence, toxic effects, lethal action on the foetus of the pregnant mouse, crossed-immunoelectrophoresis by agar gel (simple or double quantitative diffusion), electrophoresis by polyacrylamide gel.The use of those numerous techniques has enabled us to observe significant differences between those strains. However, it is not yet possible to propose a classification defining several groups. The specificity of these differences, especially between ovine and caprine strains, should become clear through the studies now in progress: in particular through the method using the interference of specific antigens compared on the one hand by serioimmunologic methods and, on the other hand, by tests setting an immunity to cellular mediation into action.     

The weather determines the number of cases of tick paralysis in dogs and cats in eastern Australia,caused by Ixodes holocyclus,the eastern paralysis tick

We studied over 222,000 cases of emergency veterinary consultations in four regions along the eastern coast of Australia. We found that cases of tick paralysis (TP) caused by the eastern paralysis tick, Ixodes holocyclus, accounted for 7.5% of these cases: >16,000 cases. The season of TP and the number (prevalence) of TP cases varied among regions and over the years. Our study of the association between weather and (i) the start of the season of TP, and (ii) the number of TP cases revealed much about the intricate relationship between the weather and I. holocyclus. We studied the effect of the hypothetical availability of isoxazoline-containing tick-preventative medicines and found that an increase in the availability of these medicines had significantly contributed to the decrease in TP cases. We found that the weather in winter accounted for the time of the year the season of TP starts whereas the weather in summer accounted for the number of TP cases in the TP season. Last, through a study of the effects of shifts in the climate under four hypothetical scenarios (warmer/cooler and drier/wetter than average), we propose that the start of the season of TP depends on how soon the weather in winter becomes suitable for the activity (e.g. host-seeking) and the development of I. holocyclus nymphs, and that the number of TP cases during the TP season depends on how many engorged female ticks and their eggs survive during summer.     

Crystal structure of a silyl cation with no coordination to anion and distant coordination to solvent

The crystal structure of a stable silyl cation, triethylsilylium, in the form of its tetrakis (pentafluorophenyl)borate salt [Et(3)Si(+) (C(6)F(5))(4)B(-)] (Et, ethyl) shows no coordination between cation and anion. The closest silicon-fluorine distance is greater than 4 angstroms. A toluene solvent molecule is close enough to cause some deviations from planarity at the silicon, but the silicon-toluene distance is well beyond the sum of the silicon and carbon covalent radii. The toluene molecule is essentially planar and undistorted, as expected if little or no positive charge has been transferred from silicon to toluene.