No abstract

The effect of source of carbohydrate on gut histology, digestion efficiency, and growth performance in early-weaned (25 d) rabbits at the starter period (25 to 39 d) was investigated. Six diets were factorially arranged to study the effect of partial substitution of starch (0, 25, or 50%) by lactose at two levels of fiber (30 or 36% NDF). Diets were formulated to meet or exceed essential nutrient requirements of growing rabbits. A feeding trial was conducted to measure the effect of treatments on growth performance in 252 rabbits that were fed the experimental diets in the starter period and thereafter received a common feed until 60 d of age. Fecal apparent digestibility was determined at 35 d of age in nine animals per diet. The four diets with extreme lactose content were used to determine ileal apparent digestibility of starch and lactose (nine replicates per diet), weights of stomach and cecum, stomach pH, cecal fermentation traits, amylase and disaccharidase activities (10 animals per diet), and jejunal morphology (six animals per diet). Weaning increased (P < 0.001) amylase activity by 59% but decreased (P < 0.001) maltase, sucrase, and lactase activities by 30, 48, and 72%, in parallel with a reduction of villus height by 19%. Dietary NDF level did not affect either jejunal morphology or sucrase and lactase activities but increased amylase (P = 0.05) and maltase (P < 0.001) activities by 22 and 92%, respectively. Substitution of starch by lactose had no effect on jejunal morphology or enzymatic activity. Ileal lactose and starch digestibility were not affected by dietary NDF or lactose level and averaged 73.8 and 90.8%, respectively. Substitution of starch by fiber and lactose affected ileal flux of starch plus lactose (by -0.5 and +1.7 g/d) and cecal pH (by +2.1 and -2.8%, respectively). Fecal NDF digestibility was relatively low (23.1% on average) and was not affected by treatments, whereas that of lactose and starch was almost complete. An increase of dietary NDF level led to an impairment of ADG and feed efficiency in the starter (P < 0.002) and in the overall (P < 0.03) fattening period. Substitution of starch by lactose linearly decreased (P < 0.001) feed efficiency in the starter period and linearly increased (P < 0.001) diarrhea incidence in the fattening period. The results indicate that digestive capability of early-weaned rabbits is limited and should be taken into account to establish optimal levels and sources of carbohydrates in the starter diet.

-Four diets based on different vegetal protein concentrates: soya bean meal 48 (SB48 diet), soya bean protein concentrate (SB61 diet), sunflower meal 36 (SF36 diet) and a combination of soya bean meal 48 and potato protein concentrate (SB48-P77 diet) were formulated for the starter period (25-39 days) in early weaned rabbits (25 days of age). These sources of protein accounted for 30% of the total dietary crude protein (CP) content. All diets were formulated to be isonutritive and to meet or exceed all the essential nutrient requirements of growing rabbits. A feeding trial was conducted to measure the effect of the treatments on growth performance in 204 rabbits that were fed ad libitum the experimental diets in the starter period and thereafter received a common feed until 60 d of age. Faecal and ileal apparent digestibility of dry matter (DM) and CP (9 and 7 replicates, respectively) were determined at 35 d of age. The weights and pH of the stomach and caecal contents, ammonia concentration in the caecum and jejunal morphology were also determined (11 rabbits per diet). The treatments did not affect faecal DM and CP digestibility. However, the source of protein affected ileal digestibilities of DM and CP (P < 0.04), which were around 14 and 7% higher for SB61 and SF36 diets, respectively, than for the SB48 diet, whereas the values obtained for the SB48-P77 diet were intermediate. The ileal flux of CP and the N-NH 3 caecal concentration were (P = 0.08 and 0.05, respectively) affected by the source of protein. The highest values were observed in animals fed the SB48-P77 diet, increasing by around 25 and 35%, respectively, compared to the other three diets. The treatments had no effect on digestive traits and jejunal morphology. The differences in ileal digestion efficacy among treatments led to differences (P = 0.008) in food efficiency the first week after weaning, which was higher (10%, as average) in animals fed the SB61 diet than that observed for animals fed the SB48 and SB48-P77 diets, whereas the value obtained for SF36 was intermediate. In this period, the type of diet tended (P = 0.08) to affect daily gain and food efficiency, with the lowest values obtained for the SB48 diet. The treatments had no effect on mortality in the first two weeks after weaning. However, mortality in the whole fattening period was affected by protein source (P = 0.03), since it was higher in animals fed the SB48-P77 diet after weaning than the animals fed the other three diets (34.6 vs. 16.7%, respectively). In conclusion, SF36 and SB61 are the sources of protein that led 461 * Corresponding author: cdeblas@pan.etsia.upm.es Anim. Res. 52 (2003) DOI: 10.1051 to the best growth performances and the lowest mortality rate. The higher efficiency obtained for these feeds might be mainly related to its higher ileal (CP) digestibility.461-471  INRA, EDP Sciences,sources of protein / digestion / growth performance / early weaning / rabbits Résumé -Effet de la source protéique sur la digestion et la croissance de lapereau...

The Cuatro Ciénegas Basin (CCB) is located in the Chihuahuan desert in the Mexican state of Coahuila; it has been characterized as a site with high biological diversity despite its extreme oligotrophic conditions. It has the greatest number of endemic species in North America, containing abundant living microbialites (including stromatolites and microbial mats) and diverse microbial communities. With the hypothesis that this high biodiversity and the geographic structure should be reflected in the virome, the viral communities in 11 different locations of three drainage systems, Churince, La Becerra, and Pozas Rojas, and in the intestinal contents of 3 different fish species, were analyzed for both eukaryotic and prokaryotic RNA and DNA viruses using next-generation sequencing methods. Double-stranded DNA (dsDNA) virus families were the most abundant (72.5% of reads), followed by single-stranded DNA (ssDNA) viruses (2.9%) and ssRNA and dsRNA virus families (0.5%). Thirteen families had dsDNA genomes, five had ssDNA, three had dsRNA, and 16 had ssRNA. A highly diverse viral community was found, with an ample range of hosts and a strong geographical structure, with very even distributions and signals of endemicity in the phylogenetic trees from several different virus families. The majority of viruses found were bacteriophages but eukaryotic viruses were also frequent, and the large diversity of viruses related to algae were a surprise, since algae are not evident in the previously analyzed aquatic systems of this ecosystem. Animal viruses were also frequently found, showing the large diversity of aquatic animals in this oasis, where plants, protozoa, and archaea are rare. In this study, we tested whether the high biodiversity and geographic structure of CCB is reflected in its virome. CCB is an extraordinarily biodiverse oasis in the Chihuahuan desert, where a previous virome study suggested that viruses had followed the marine ancestry of the marine bacteria and, as a result of their long isolation, became endemic to the site. In this study, which includes a larger sequencing coverage and water samples from other sites within the valley, we confirmed the high virus biodiversity and uniqueness as well as the strong biogeographical diversification of the CCB. In addition, we also analyzed fish intestinal contents, finding that each fish species eats different prey and, as a result, presents different viral compositions even if they coexist in the same pond. These facts highlight the high and novel virus diversity of CCB and its "lost world" status.