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The effectiveness of an Escherichia coli phytase in comparison with a commercially available Aspergillus phytase in improving the bioavailability of phosphorus in broilers, layers and young pigs was studied in three separate experiments. Three basal diets, marginally deficient in dietary P mainly provided as phytate, were formulated. Both phytases were added to the diets at the rate of 500 U/kg diet. The phytases significantly (Por = 0.05) improved the availability of phytate P to broilers, layers and young pigs. Aspergillus and E. coli phytases enhanced the pre-caecal digestibility of P by 11 and 29% for broilers and 18 and 25% for layers, respectively. Total tract digestibility of P (P balance) was also enhanced but with smaller magnitude. In pigs, total tract digestibility of P was improved by 33 and 34% by Aspergillus and E. coli phytases, respectively. Under the conditions of this study, it was observed that E. coli consistently, though with small magnitude in layers and pigs, enhanced the availability of phytate P at the same range or slightly better than Aspergillus phytase. It was only in pigs that the availability of Ca was significantly (Por = 0.05) improved by addition of both phytases. It can be concluded that E. coli phytase is highly effective in improving the bioavailability of phytate P to broilers, layers and young pigs. This seems to be based on the high proteolytic stability of the enzyme in the digestive tract, as shown recently.

The physical and chemical properties of six crude phytase preparations were compared. Four of these enzymes (Aspergillus A, Aspergillus R, Peniophora and Aspergillus T) were produced at commercial scale for the use as feed additives while the other two (E. coli and Bacillus) were produced at laboratory scale. The encoding genes of the enzymes were from different microbial origins (4 of fungal origin and 2 of bacterial origin, i.e., E. coli and Bacillus phytases). One of the fungal phytases (Aspergillus R) was expressed in transgenic rape. The enzymes were studied for their pH behaviour, temperature optimum and stability and resistance to protease inactivation. The phytases were found to exhibit different properties depending on source of the phytase gene and the production organism. The pH profiles of the enzymes showed that the fungal phytases had their pH optima ranging from 4.5 to 5.5. The bacterial E. coli phytase had also its pH optimum in the acidic range at pH 4.5 while the pH optimum for the Bacillus enzyme was identified at pH 7.0. Temperature optima were at 50 and 60 degrees C for the fungal and bacterial phytases, respectively. The Bacillus phytase was more thermostable in aqueous solutions than all other enzymes. In pelleting experiments performed at 60, 70 and 80 degrees C in the conditioner, Aspergillus A, Peniophora (measurement at pH 5.5) and E. coli phytases were more heat stable compared to other enzymes (Bacillus enzyme was not included). At a temperature of 70 degrees C in the conditioner, these enzymes maintained a residual activity of approximately 70% after pelleting compared to approximately 30% determined for the other enzymes. Incubation of enzyme preparations with porcine proteases revealed that only E. coli phytase was insensitive against pepsin and pancreatin. Incubation of the enzymes in digesta supernatants from various segments of the digestive tract of hens revealed that digesta from stomach inactivated the enzymes most efficiently except E. coli phytase which had a residual activity of 93% after 60 min incubation at 40 degrees C. It can be concluded that phytases of various microbial origins behave differently with respect to their in vitro properties which could be of importance for future developments of phytase preparations. Especially bacterial phytases contain properties like high temperature stability (Bacillus phytase) and high proteolytic stability (E. coli phytase) which make them favourable for future applications as feed additives.

Five trials were conducted with 744 beef heifers to determine the efficacy of exogenous steroid hormones for synchronization of estrus under field conditions. An implant containing 6 mg of 17α-acetoxy-11β-methyl-19-nor-preg-4-ene-3,20-dione (norgestomet) was implanted subcutaneously in the convex surface of the ear and remained in situ for 9 days. An intramuscular injection of 5 mg of estradiol valerate (EV) plus 3 mg of norgestomet was administered on the day the implant was inserted. Approximately equal numbers of treated and control animals were used in each trial. The proportion of treated heifers in estrus by 120 hr after implant removal was 100%, 98%, 98%, 85% and 96% in Trials 1 through 5, respectively. In Trials 2, 3 and 5, small nonsignificant differences of 3%, 4% and 0%, respectively, were noted in pregnancy rate at first service between treated and control heifers, whereas, in Trials 1 and 4, significantly more control heifers (21% and 25%) were pregnant after first service (P

The White-bellied Wren (Nannorchilus leucoguster) is a small, plainly colored, almost exclusively Mexican wren which is far more often heard than seen. It is smaller than the House Wren (Troglodytes agdon) and is brownish gray above and grayish white below, and has a fairly distinct grayish white superciliary line. Its wings and tail are faintly barred with dark brown. Its most distinctive feature is its stubby tail, which is only a little more than an inch long. In the Gomez Farias district of southwestern Tamaulipas, where I first encountered this wren in early March of 1938 (Sutton and Burleigh, 1939:36), it lives principally in the thickets of kuipilca or wild pineapple (Bromelia pinguin) , a tough, barbed xerophyte which grows in dense, waist-high mats throughout the brushy woodlands bordering the rivers as well as on the lower foothills of the Sierra Madre Oriental. Here the bird spends much of its time close to the ground, feeding at the bases of theleaf-rosettes, keeping itself more or less hidden even while singing. Its song, a tinkling, ebullient pret-til-ly, pret-til-ly, pret-til-ly, is instantly recognizable as a wren’s because of its rhythmic quality. As the bird sings it lifts its head, but ordinarily it does not assume the head-straight-up, tail-straight-down posture which is characteristic of so many wrens. Two other bird species, the Cinnamomeous Tinamou (Crypturellus cinnumomeus) and Olive Sparrow (Arremonops rujivirgatus), inhabit the huipilla beds with it in that region. .

In the course of the John B. Semple expedition of 1939 to eastern Mexico, several points in the low, comparatively flat southeastern part of San Luis Potosi were visited. Extensive collections were made in the vicinity of Tamazunchale and at Valles, towns situated 66 miles apart at between 200 and 300 feet elevation along the highway from Laredo to Mexico City. Two four-day stops were made at Valles, the first from March 23 to 26, the second (Semple and Sutton only) from April 29 to May 2. Since the birds recorded at this point differ so considerably from those seen at Tamazunchale, we have decided to publish lists from the two regions separately. The most thoroughly investigated section near Valles was the dry, wooded plateau, about 300 to 400 feet in elevation, extending from two to twelve miles north of town. Here there were grassy, prairielike openings among the trees, thick tangles crossed by cattle trails, and clumps of wild pineapple and palmetto. At the time of our visits most of the larger trees were leafless, and the countryside appeared somewhat desertlike. The following list of eighty-seven forms includes most of the birds that breed on the uplands near Valles, some that characteristically winter there, and a few that are transients. Since no extensive work was done along any stream in the vicinity, the characteristic waterbirds (kingfishers, herons, ducks, and shorebirds) naturally are missing from our list.