Evaluating the effect of calcium, magnesium and sodium supplementation of Merino ewes on their lambs' growth

Our study aimed to investigate responses to supplementation of calcium (Ca), magnesium (Mg) and sodium (Na) to lactating ewes and lambs grazing barley forage from lamb marking to weaning. A 10-ha paddock sown to barley was subdivided into eight plots as four replicates of two treatments. Merino ewes (n = 104) with lambs at foot were stratified to the eight plots (13 ewes and 21 lambs/plot) based on number of lambs (twin or single) and ewes' weight. Supplemented groups had access to mineral supplements (30 g/ewe/day) supplying 12 g/ewe/day ground limestone, 12 g/ewe/day Causmag® and 6 g/ewe/day coarse salt in a ratio of 2: 2: 1 by weight (as fed) from day 0 (a day before lamb marking) after sample collection. Control groups were not supplemented with minerals. Blood, milk and urine samples from ewes and blood from lambs were collected at different time points, namely, a day prior to lamb marking (day 0), 14 days after the commencement of study (day 14), and 28 days after the commencement of study (day 28). Weight of the lambs was also recorded at each time point. We found that the concentration of the forage minerals (Ca, Mg and potassium (K)) was lower on day 28 than on day 0 (P < 0.025). Liveweight gain was greater in the first 14 days compared with the second weight gain period (P < 0.001). The interaction of time and treatment was significant for liveweight (P < 0.001). Due to the improvement in weight gain of supplemented lambs, we recommend that mineral supplementation during late lactation is beneficial considering the low cost of minerals, even though the mineral content of the forage was not deficient.

Behavioral responses to environmental change alter direct and indirect trait-mediated interactions

We used a field-based experiment to explore the consequences of altered environmental conditions on a predator–prey–resource system. The foraging choices of grasshoppers on plant resources were measured in the presence and absence of predator spiders and in shaded and unshaded conditions. We show that shading conditions affected the spiders, their direct behavioral interactions with the grasshoppers, and the indirect behaviorally mediated interactions between the spiders and the plants. In unshaded conditions in response to spiders, grasshoppers reduced their energy intake by 90%, reduced their time spent feeding by 68%, and switched to a largely grass diet that should increase mortality, while in shaded conditions spiders induced no behavioral shift. In no shade, spiders had an indirect positive effect on forb plants as evidenced by a trophic cascade pattern in plant biomass in the one-, two-, and three-trophic-level communities. But in shade, there was no indirect interaction of the spiders on the plants. Our results demonstrate the challenge of predicting the effects of environmental change on complex, real-world ecosystems and highlight the critical need for conducting experimental manipulations in the proper context with full complements of species.

Cortical visual dysfunction in children: a clinical study

Damage to the cerebral cortex was responsible for impairment in vision in 90 of 130 consecutive children referred to the Vision Assessment Clinic in Glasgow. Cortical blindness was seen in 16 children. Only 2 were mobile, but both showed evidence of navigational blind-sight. Cortical visual impairment, in which it was possible to estimate visual acuity but generalised severe brain damage precluded estimation of cognitive visual function, was observed in 9 children. Complex disorders of cognitive vision were seen in 20 children. These could be divided into five categories and involved impairment of: (1) recognition, (2) orientation, (3) depth perception, (4) perception of movement and (5) simultaneous perception. These disorders were observed in a variety of combinations. The remaining children showed evidence of reduced visual acuity and/ or visual field loss, but without detectable disorders of congnitive visual function. Early recognition of disorders of cognitive vision is required if active training and remediation are to be implemented.

Ultrastructural localization of retinal S antigen in the human retina

Retinal S antigen, a uveitogenic protein implicated in several forms of clinical and experimental uveoretinitis, has been localized by immunoelectron microscopy in the human photoreceptor outer segment using a protein A-gold technique and anti-bovine retinal S antigen serum. The protein was predominantly located to the proximal portion of the rod outer segment and appeared to be distributed on the disc membrane but not on the plasma membrane. No immunoreactive product was detected in cone outer segments or in any other retinal structure. These findings are discussed in relation to the physiological function of S antigen and its role in initiation of posterior uveitis.