Diet selection by calves facing pairs of nutritionally complementary foods

Experimental evidence suggests that ruminant animals are capable of selecting a nutritionally balanced diet (i.e. a diet appropriate to their metabolic needs) from imbalanced but complementary foods. We tested this hypothesis by offering calves different combinations of the same complementary foods. A 5 × 5 Latin square design was used to assess the effect on diet selection of different combinations (termed as food A and food B) of two complementary foods (alfalfa-grass hay and maize grain) offered in separate feed bunks. In Treatment 1, food A and food B had the same composition, 50.0% hay and 50.0% grain (T50:50). In the rest of the treatments, hay–grain combinations in foods A and B were, respectively: 62.5–37.5% and 37.5–62.5% (T63:37); 75.0–25.0% and 25.0–75.0% (T75:25); 87.5–12.5% and 12.5–87.5% (T88:12); and 100.0–0.0% and 0.0–100.0% (T100:0). Daily intake data were analysed through repeated measures analysis. Crude protein intake was similar across treatments (P = 0.28). An increasing tendency (P = 0.01) in food B intake (the food with more grain content) from T50:50 to T100:0, however, led into a decreasing tendency (P < 0.001) in the protein: energy ratio of the diet across treatments. Grain consumption in treatments T75:25, T88:12 and T100:0 was higher than expected, leading to protein levels in the diet below those required for a balanced diet (predicted vs. observed: 19.38 vs. 16.67, P = 0.004; 20.53 vs. 16.10, P = 0.001; and 20.23 vs. 16.79 g kgMW^? 1 d^? 1, P = 0.015, for T75:25, T88:12 and T100:0, respectively). Although calves were potentially able to select a balanced diet in all feeding treatments, they failed when offered high grain foods at choice (75% of maize grain or more). Evolved mechanisms to regulate macronutrient intake under natural conditions may fail to adequately operate in artificial environments involving high-energy density foods (e.g. maize grain).     

Selection of young barley plants for tolerance to high soil acidity in relation with some agronomic characteristics of mature plants

Summary In four segregating populations of barley, grown in a naturally highly acid soil good plants and less vigorous ones were marked in a 3–4 leaf stage of development.Some agronomic characters of mature plants were studied in relation with the level of tolerance to high soil acidity of their progenies when tested in a seedling stage in a laboratory method.As compared with the good groups the reductions proved highly significant viz. 60% for mean number of tillers per plant, 25% for average culm length, 35% for mean number of kernels per spike and about 12% for 1000-grain weight.On the average more than 95% of the good plants showed a high level of tolerance to high soil acidity, indicating a close correlation between low-pH tolerance and agronomic performance.Although a rather high percentage (40%) of the progenies among the plants marked as bad was found to be tolerant, those lines showed a poor general performance.This goes to show that selection for tolerance to high soil acidity before flowering is an advisable procedure, without the risk of including sensitive lines or losing otherwise valuable genotypes.This study was carried out during a fellowship of the Spanish Ministry of Agriculture.     

Field-testing and characterization of Technosols made from industrial and agricultural residues for restoring degraded slopes in semiarid SE Spain

Journal of Soils and Sediments - Many industries and agriculture generate huge amounts of wastes either mineral, organic or both, with environmental impact. Some of these residues have the...     

Holocene-era landscape conditions affect genetic connectivity in a sagebrush obligate species,the pygmy rabbit (Brachylagus idahoensis)

Landscape Ecology - Environmental changes produce discontinuities in suitable habitat. However, drawing inference into the effects of these changes on contemporary genetic patterns is often...