Indirect evidence for microbiota reduction through dietary mannanoligosaccharides in the pigeon, an avian species without functional caeca.

A feeding trial was conducted to evaluate the effects of mannanoligosaccharides (MOS) on nutrient digestibility, intestinal pH, gut morphology and faecal bacteriology of pigeons, as model for birds without functional caeca. Sixteen adult pigeons (Columba livia domestica) were randomly allotted to either an extruded pellet diet with or without 0.4% MOS. After an adaptation period of 24 days, excreta were collected during 4 days. Apparent nutrient digestibility coefficients were determined using total collection method. Further, excreta pH was measured and percentage of uric acid determined. Fresh excreta were cultured for measurement of colony-forming units for Escherichia coli. At the end, the gastrointestinal tract (GIT) was excised and pH measurements performed on the separate GIT sections. Finally, pancreas, liver, gizzard and abdominal fat pad were weighed, and standardised segments of duodenum and jejunum were removed for microscopic measurement of crypt depth, villus height and muscularis thickness. Feed intake and water intake were similar between control diet and MOS diet. Intestinal pH was unaffected by MOS supplementation; however, excreta pH was significantly lower in pigeons on the MOS diet. Although nutrient digestibility was similar between treatments, uric acid content of excreta was significantly higher in the MOS group in relation to the control group. Further, duodenal crypt depth, villus height and muscularis thickness, as well as jejunal muscularis thickness were all significantly reduced by MOS supplementation. No effect of MOS supplementation was seen on the counts of E. coli. Furthermore, despite marked differences on both GIT morphology and uric acid content of excreta, apparent digestibility coefficients, and organ weights, were similar between treatments. It is suggested that the MOS-induced changes on gut morphology and the reduced excreta pH reflect a reduced bacterial challenge in the intestine of pigeons. Supplementation of MOS, therefore, has potential as prebiotic strategy in birds without functional caeca.

The effect of starch gelatinisation degree on intestinal morphology, intestinal pH and bacteriology in pigeons.

The effect of starch gelatinisation degree in extruded feed on intestinal morphology, intestinal pH and faecal bacteriology was investigated in pigeons. Extruded complete pigeon diets would offer the principle advantage of providing equilibrated nutrients and energy, but factors such as starch gelatinisation require investigation before these diets are offered as main dietary items to pigeons. Birds were fed two diets with equal ingredient composition and nutrient content, but with a different degree of starch gelatinisation resulting from altered extrusion processing (high gelatinisation degree (HG) with 73.6% gelatinisation vs. low gelatinisation degree (LG) with 53.1% gelatinisation). Feed intake and weight gain changes were measured weekly. Blood samples were collected at day 28 and analysed for non-esterified fatty acids, lactate dehydrogenase and glucose. The pH values for fresh excreta were measured; thereafter fresh excreta were collected and cultured for measurement of colony-forming units for bacterial classes. At the end, morphological measurements were examined and the pH values throughout the gastrointestinal tract were recorded. Liver, pancreas and abdominal fat were weighed. There was a tendency (p= 0.07) towards higher numbers of Escherichia coli in the excreta of the LG group compared with those in the HG group. No dietary treatment effects were noted on the number of Lactobacillus sp. in the excreta. In proximal parts of the intestine, LG revealed a significantly lower pH than HG. Villus height and crypt depth were not affected by dietary treatment, but the duodenum muscularis thickness, liver weight and pancreas weight were significantly lower in the LG than that in HG group. This trial demonstrated that the lower level of starch gelatinisation degree of extruded feed leads to acidification of the proximal gut and altered gut morphology in pigeons. Hence, extruded pigeon diets should preferably contain low-gelatinised starch instead of high-gelatinised starch. In addition, future research must focus on the effects of starch gelatinisation on the correlation between the intestinal pH, microflora content and intestinal morphology.

Effects of segregation and impact of specific feeding behaviour and additional fruit on voluntary nutrient and energy intake in yellow-shouldered amazons (Amazona barbadensis) when fed a multi-component seed diet ad libitum.

Parrots are commonly fed multi-component seed diets; however, both segregation and feeding behaviour might alter ingredient and nutrient composition of the offered diet. First, the nutritional impact of segregation was assessed as it occurs when multi-component diets are temporarily stored in food containers that are replenished before completely emptied and birds being fed from the upper layer. The most detrimental effect hereof was a vast decrease in mineral supplements, leading to a decrease in Ca:P ratio in the offered food in relation to the formulated diet. Next, caloric distribution shifted towards more EE energy at the expense of NFE energy, as proportion of oilseeds increased and NFE-rich seeds decreased. Next, a feeding trial was performed on six yellow-shouldered amazons (Amazona Barbadensis) in which nutritional impact of parrot-specific feeding behaviour was assessed as well as the influence of additional provision of fruit next to the seed mixture. Profound selective feeding behaviour and dehusking of seeds resulted in a vast increase in energetic density by up to 64% in the ingested fraction in relation to the offered mixture in toto. Furthermore, the already suboptimal Ca:P ratio further deteriorated and caloric distribution shifted by over twofold towards EE energy accompanied with a vast decline in NFE energy, CP energy remaining similar. Finally, provision of fruit next to the seed diet significantly lowered voluntary energy intake from 936 ± 71 to 809 ± 109 kJ ME/kg(0.75)/day, without compromising adequate protein intake. In conclusion, notwithstanding efforts of nutritionists to formulate diets to approximate estimated, species-specific requirements, nutritional composition of the actually consumed fraction of multi-component seed diets can be vastly deteriorated by both animal and management factors. Furthermore, offering of fruit next to a seed-based diet effectively reduces voluntary energy intake and can hence be applied to abate obesity.

Effect of starch gelatinisation on nutrient digestibility and plasma metabolites in pigeons.

Feed manufacturing exerts physical and chemical changes in ingredients, including the gelatinisation of starch. Studies on the effect of the degree of starch gelatinisation on nutrient digestibility, metabolism and subsequent performance show inconsistent results, and no data are available in pigeons. In a cross-over trial, fourteen adult pigeons were randomly divided into two groups, in which two extruded pellet diets were tested. Both the diets were similar in ingredient composition and nutrient content, but differed in extrusion conditions, resulting in a different degree of starch gelatinisation: pellets with high gelatinisation degree (HG; 73.6% gelatinisation) and low gelatinisation degree (LG; 53.1% gelatinisation). After a 14-day adaptation period, all excreta were gathered per bird during a 5-day collection period. Coefficients of apparent digestibility of dry matter (DM), crude protein (CP), ether extract (EE), crude fibre (CF), crude ash (CA) and nitrogen free extract (NFE) as well as apparent nitrogen retention were calculated from proximate analyses of feed and excreta. Further, excreta consistency was subjectively scored. Blood samples were taken at the end of each period and plasma samples were analysed for glucose, fructosamine and triglycerides. Feed intake and body weight changes were recorded weekly. The apparent digestibility coefficients (ADCs) of DM, OM, CP, EE, CA and NFE were significantly higher in the LG group (p < or = 0.05). The ADC of crude fibre was numerically higher in the LG group but not significant, and no significant differences were found in starch digestibility. Excreta consistency score tended to be higher in the LG diet group. Neither plasma glucose nor plasma fructosamine values were significantly different between the two test diets. The results of this study show that lower degree of starch gelatinisation in extruded diets can enhance digestibility in pigeons.

Effect of dilution degree of commercial nectar and provision of fruit on food, energy and nutrient intake in two rainbow lorikeet subspecies.

A feeding trial was performed on adult rainbow lorikeets of two subspecies: six green-naped lorikeets (Trichoglossus haematodus haematodus) and six red-breasted lorikeets (T. haematodus mitchellii). Throughout the entire trial, half of the birds from each subspecies had ad libitum access to water-diluted commercial nectar powder and drinking water only, whereas the other half also received ad libitum apple pieces. During three consecutive 14-d periods, the nectar powder was diluted to a different degree: 1:3 (low), 1:5 (high) and 1:4 (medium) (v:v). Diluting nectar to a higher degree resulted in both subspecies in a decrease in voluntary energy intake. Next, nectar intake significantly decreased when apple was available and apple intake significantly increased when fed higher-diluted nectar. In green-naped lorikeets fed nectar and apple, energy intake was similar between dilution degrees of nectar but was lower compared with feeding only low- or medium-diluted nectar. Whereas, in red-breasted lorikeets, provision of apple next to medium- or high-diluted nectar resulted in higher voluntary energy intake compared with feeding solely nectar of any degree. Overall, protein and thiamine intake as well as Ca:P ratio of the ingested ration were lowest when fed highly diluted nectar and apple. Yet, minimal requirements were still covered. Because energy content of fruit can be higher than liquid diets, in this case medium- or high-diluted nectar, ad libitum provision of fruit as a means to lower voluntary energy intake in lorikeets, for instance in case of obesity, needs to be considered with care.

Apparent nutrient digestibility and excreta quality in African grey parrots fed two pelleted diets based on coarsely or finely ground ingredients.

A feeding trial was performed to study the influence of particle size in extruded parrot pellets on apparent digestibility and excreta consistency and pH. Two test diets were alternately provided to eight African grey parrots according to a 2 x 2 cross-over design. Both diets were similar in nutrient content and ingredient composition but differed in particle size of the composing particles of individual pellets. Apparent digestibility of macronutrients was studied using the total collection method. Next, the appearance of the excreta was studied by calculation of weight-surface ratio of individual excrements as an objective measurement of consistency. Last, excreta pH was measured directly on fresh excrements and on homogenized 10% excreta solutions. Neither apparent digestibility coefficients nor excreta pH values were significantly different in parrots fed the two diets. However, excreta consistency was significantly (p < 0.05) more solid when fed the coarse diet than when fed with the finely ground diet. The results of this study suggest that excreta consistency can be improved through larger particle size, without adverse effects on nutritive value of the diet.

Comparison of the nutrient analysis and caloric density of 30 commercial seed mixtures (in toto and dehulled) with 27 commercial diets for parrots.

In this paper, an overview is given of the composition of 30 commercially available parrot seed mixtures. As parrots dehull the seeds, the analysis of the total seed mixture tends to differ from that of the ingested feed. Statistical evaluation and comparison of the dehulled seeds vs. the whole seeds indicates that most parrot species are fed a diet rich in fat (31.7 +/- 13.1% crude fat) and energy (22.4 +/- 2.9 MJ ME/kg). As the analysis of the total seed mixtures underestimates fat and energy content of the ingested feed, it is suggested that researchers, bird nutritionists and bird food producers should calculate diets based on the analysis of the dehulled seeds. Finally, the calculated data were compared with the composition of formulated pelleted/extruded diets on the market. These data indicate that the energy density of most diets (15.6 +/- 1.4 MJ ME/kg) is far below the energy density of common seed mixtures.