Developmental adjustments of house sparrow (Passer domesticus)nestlings to diet composition

Abstract

SUMMARYHouse sparrow nestlings are fed primarily on insects during the first 3 days of their life, and seeds become gradually more important afterwards. We tested whether developmental changes in size and functional capacity of the digestive tract in young house sparrows are genetically hard-wired and independent of diet, or can be modified by food type. Under laboratory conditions, we hand-fed young house sparrows with either a starch-free insect-like diet, based mainly on protein and fat, or a starchcontaining diet with a mix of substrates similar to that offered to older nestlings in natural nests when they are gradually weaned from an insect to a seed diet. Patterns of overall development in body size and thermoregulatory ability, and in alimentary organ size increase, were relatively similar in house sparrow nestlings developing on both diets. However, total intestinal maltase activity, important in carbohydrate breakdown, was at least twice as high in house sparrow nestlings fed the starch-containing diet (P<0.001). The change in maltase activity of nestlings was specific, as no change occurred in aminopeptidase-N activity in the same tissues. There was no significant diet effect on digesta retention time, but assimilation efficiency for radiolabeled starch tended to be higher (P=0.054) in nestlings raised on starch-containing diet. Future studies must test whether the diet-dependent increase in maltase activity during development is irreversible or reversible, reflecting, respectively, a developmental plasticity or a phenotypic flexibility.

Gut Bacterial Diversity of the House Sparrow (Passer domesticus) Inferred by 16S rRNA Sequence Analysis

“…While some of the habitat characteristics (like pH or oxygen levels) could have important effects on the bacterial communities, the reduction in the diversity and availability of metabolizable substrates along the gut is probably the reason for the decreasing diversity of bacterial genera and species along the gut of the House Sparrow (Figures 3(a) and 3(b)) [41,55,59]. Previous studies of the physiology of this species showed that the activity of intestinal enzymes decreased along the gut as a response of a reduction of nutrients [9].…”

“…The dominance of Firmicutes and Proteobacteria in the intestinal bacterial communities has been reported for other birds like Zebra Finches [8], as well as wild and captive parrots [73]. Because Proteobacteria is a group with a high functional diversity [29], the dominance of Proteobacteria in the House Sparrow gut could be related to its omnivorous diet that includes seeds, insects, fruits, and a large diversity of human food scraps including meat [9,11,49]. This diverse diet provides bacterial communities with a high diversity of substrates.…”

“…To avoid contamination from bacteria present in the bird's food, we kept the two captured birds in cages for two and a half hours without food prior to tissue collection. Because gut-passage times in this species are long for a bird of its size (120-140 min) [9], this procedure allowed us to ensure that the intestines were empty at the moment of tissue collection. Birds were euthanized with ether and their intestines were immediately removed, dissected, and frozen in liquid nitrogen while the tissue was still fresh (birds were euthanized in conformity with Mexican laws and the codes of practice included in the guidelines for the use of wild birds in research).…”

Are levels of digestive enzyme activity related to the natural diet in passerine birds?

“…Nevertheless, recently, Brzek (2009) documented that specifi c maltase activity can be modulated during development in nestlings of house sparrows (Passer domesticus), but not in adult birds (Cavides-Vidal et al, 2000), suggesting that the magnitude of modulation in enzyme activities can be largely underestimated when using adult animals as experimental subjects. Unfortunately, few studies on the physiological diversity of birds have partitioned phenotypic variation (Biviano et al, 1993;Brzek et al, 2009), and hence it remains unknown how much of intra-specifi c variability in enzyme activities has a genetic basis or is attributable to phenotypic plasticity.…”

“…Furthermore, Meynard et al (1999), found a higher activity of maltase in the hervibore passerine Phytotoma rara, an expected result given the high carbohydrate diet of this animal. On the other hand, it has been documented that the activity of brush border enzymes can be strongly affected by the levels of specifi c substrates in both the fi eld and the laboratory (Martinez del Sabat et al, 1999;Caviedes-Vidal et al, 1994;Karasov et al, 1997;Sabat et al, 1998;Caviedes-Vidal et al, 2000;Brzek et al, 2009).…”