Rosa Carabaño

Effect of fiber source on cecal fermentation and nitrogen recycled through cecotrophy in rabbits.

The influence of fiber source on fiber digestion in rabbits was investigated. Six fibrous feedstuffs with wide differences in chemical composition and particle size were selected: paprika meal, olive leaves, alfalfa hay, soybean hulls, sodium hydroxide-treated barley straw, and sunflower hulls. Six diets were formulated to contain one of these ingredients as the sole source of fiber. To avoid nutrient imbalances, fiber sources were supplemented with different proportions of a fiber-free concentrate, based on soy protein isolate, wheat flour, lard, and a vitamin and mineral mix, to obtain diets containing at least 3% nitrogen and 5% starch. Daily soft feces excretion, and its NDF, and total and microbial nitrogen content were determined in 60 fattening rabbits (10 per diet). Seven days after the last cecotrophy control, the same animals were used to determine weight of stomach, cecum and their contents, and cecal fermentation traits (pH, VFA and ammonia concentrations, and buffer properties of cecal contents). Stepwise regression analysis showed a positive effect (P < .001) on soft feces excretion, total and microbial nitrogen concentrations in soft feces, cecal acidity, and total VFA in the cecum of dietary pectic constituents (2.9, 3.5, 2.5, .9, and 6.6%) and proportion of fine particles (< .315 mm) (1.8, .9, 1.3, .15, and .9%) per each increment of one percentage unit of the independent variables. Proportion of fine particles also increased weight of cecal contents (P < .001). Soft feces excretion and weight of stomach and of its contents increased (P < .001) by 5.2, 2.8, and 10.2% per each percentage unit increment of proportion of large particles (> 1.25 mm). Degree of lignification of NDF decreased total nitrogen concentration in soft feces and cecal VFA concentration (P < .001). Source of fiber affected cecal pH not only by its influence on the cecal concentrations of the final products of fermentation, but also through its effect on the pH of dry cecal contents (P < .001). The latter was negatively correlated with dietary proportion of fine particles, degree of lignification of NDF, and base-buffering capacity of dry cecal contents (r = -.52, -.37, and -.49, respectively). From these results, we conclude that pectic constituent concentration, degree of lignification of NDF, and particle size are the variables that best characterize the influence of the source of fiber on soft feces excretion and cecal fermentation traits in rabbits.

Performance response of lactating and growing rabbits to dietary lignin content

This study investigated the lignin requirements of rabbits. Four isofibrous diets with similar particle size, containing from 59 to 33 g ADL/kg DM, were formulated by substituting a 50 : 50 mixture of wheat straw and alfalfa hay with soya bean hulls. Forty rabbits were used to determine nutrient digestibility and caecal traits. A feeding trial was carried out using 160 weanling rabbits. Milk production was measured in 48 lactations. Rabbits fed the diet with the lowest ADL content (33 g/kg DM) led to an increase NDF (p = 0.004) and energy (p = 0.06) digestibilities and feed efficiency in fattening (p = 0.03) period. The differences between extreme diets were 28%, 4%, and 6%, respectively. Weights of caecum and caecal contents were higher and caecal pH lower (by 18%, 15% and 3%; p = 0.009, 0.02 and 0.009, respectively) for rabbits fed the diet with the lowest ADL content (33 g/kg DM) than for the average of the other three diets. A decrease of dietary ADL content from 59 to 33 g/kg DM increased linearly (p < 0.05) caecal VFA concentration (by 22%) and molar proportion of propionic acid (by 30%) and decreased that of butyric acid (by 21%). Type of diet did not affect either molar proportion of acetic acid or caecal ammonia concentration. Feed intake and performance of growing and lactating rabbits were maximal for an ADL concentration of 41 and 59 g/kg DM, respectively. Average daily gain, milk production and feed intake were impaired by 5 (p = 0.04), 12 (p < 0.001) and 10% (p < 0.001), respectively, in animals fed diets containing suboptimal ADL contents. It is concluded that a minimal ADL concentration was needed to maximise feed intake and performance, and that this level was higher in lactating than in growing rabbits. This result enhances the interest of increasing the inclusion of inexpensive highly lignified by-products (as wheat straw) in commercial feeds for adult animals with respect to the levels used at present. However, a decrease of feed efficiency when increasing dietary lignin content should also be expected according to our results.

Substitution of sugarbeet pulp for alfalfa hay in diets for growing rabbits

Four rabbit diets were formulated to study the effect of a progressive inclusion (0, 100, 200, and 300 g kg − 1) of sugarbeet pulp (SBP) substitute for alfalfa hay (AH). The control diet contained 500g kg−1 of AH and 190 g kg−1 acid detergent fibre (ADF) on a DM basis. In Experiment 1, 32 Californian x New Zealand White rabbits were used to determine dietary nutrient digestibility. The inclusion of SBP quadratically increased (P < 0.01) digestibility coefficients of NDF, ADF and gross energy, showing a maximum for the diet containing 200g kg−1 of SBP. Crude protein digestibility linearly increased with SBP inclusion (P < 0.05). In Experiment 2, 36 rabbits fed the same diets as in Experiment 1 were used to determine several digestive traits and the efficiency of utilization of dietary energy for growth. Dietary inclusion of SBP did not affect either the concentrations of ammonia (66 mg of N-NH3 per litre) and total VFA (50.3 mmol l−1) or the molar proportion of VFA (767, 62 and 171 mmol mol−1 VFA of acetate, propionate and butyrate, respectively) in the cecal digesta. The concentration of starch in the ileal digesta was also unaffected by diet (7.7 g kg−1 of DM, as average). The weight of cecal contents increased (P < 0.05) and the pH of cecal contents decreased (P < 0.05) when SBP proportion in the diet increased. The efficiency of utilization of dietary digestible energy for growth was not influenced by dietary SBP inclusion (0.224, as average).

Effect of diet and of remating interval on milk production and milk composition of the doe rabbit

The influence of four diets and two remating intervals (1 or 9 days after parturition) on several milk and production traits was studied in 73 lactations of 46 Californian C? × New Zealand

Effect of dietary supplementation with glutamine and a combination of glutamine-arginine on intestinal health in twenty-five-day-old weaned rabbits

does. Three diets were formulated to provide increasing levels of fibre concentration (180, 202 and 238 g acid-detergent fibre per kg dry matter (DM)); a fourth diet contained added pork lard (35 g/kg) at the lowest level of fibre. The energy: protein ratio was maintained between 72 and 84 kj digestible energy (DE) per g digestible protein. The DE intake increased significantly when fat was included in the diet but was not affected by dietary fibre concentration. An increase in the DE content of the diet tended to decrease food conversion ratio at a mean rate of 0·16 kg/kg per MJ/kg DE. Fat addition also improved milk yield, litter weight at 21 days and survival index, mainly when litter size was higher than nine pups born alive. Neither live-weight gain nor prolificacy of does were affected by any of the variables studied. The type of diet did not affect milk DM, crude protein, fat and energy concentrations, the mean values being 287·8, 116·1, 134·2 g/kg and 27·73 MJ/kg, respectively. The proportions of short- and medium-chain fatty acids in milk fat were not affected by type of diet. The effect of fat addition on milk fat composition was limited to the long-chain fatty acids, mainly C18: 0 and C18: 1. These changes in addition to differences in milk intake could also affect the survival index of pups. Does remated 1 day after parturition showed a lower total milk yield than those remated 8 days later, the decrease being more apparent at the end of lactation. Remating interval did not affect the other variables studied.

Nutritive evaluation and ingredient prediction of compound feeds for rabbits by near-infrared reflectance spectroscopy (NIRS)

The effect of dietary supplementation with 1% l-glutamine and a combination of 1% l-glutamine and 0.5% l-arginine on intestinal health was examined in weaned rabbits. A basal diet was formulated to meet nutrient recommendations. Another 2 diets were formulated by adding 1% (as-fed basis) Gln or a mixture of 1% (as-fed basis) Gln + 0.5% (as-fed basis) Arg (Gln-Arg) to the basal diet. In Exp. 1, a total of 357 rabbits were blocked by litter and assigned at random to the experimental diet to determine mortality (119 per diet) and growth performance (35 per diet; from weaning at 25 to 56 d of age). Rabbits were fed the experimental diets for a 2-wk period and thereafter received a commercial diet. Rabbits weaned at 25 d (blocked by litter and assigned at random to diets) were slaughtered at 35 d and used to determine apparent ileal digestibility of DM, CP, and AA (Exp. 2, a total of 60 rabbits), intestinal morphology, N-aminopeptidase and myeloperoxidase intestinal activity, the expression of PPARgamma at the ileum and kidney, serum immunoglobulin in healthy and sick rabbits (Exp. 3, a total of 24 rabbits), and ileal and cecal microbial composition by PCR-RFLP (Exp. 4, a total of 45 rabbits). Dietary treatment did not affect ADG, ADFI, or G:F, during the entire fattening period. Supplementation with Gln reduced mortality during the first 2 wk and the whole fattening period from 18.5 to 8.4% (P = 0.023) and from 31.9 to 20.2% (P = 0.039), respectively, whereas no effect was detected for Arg supplementation. Among all the variables studied, the reduction on mortality due to Gln was related to a reduced intestinal colonization (Eimeria lesions) and changes on microbial ecosystem in the ileum and cecum, reducing the frequency of detection of Clostridium spp. (from 86.7 to 33.3%, P = 0.003) at the ileum, and Helicobacter spp. at the ileum (from 86.7 to 46.7%, P = 0.003) and at the cecum (from 86.7 to 46.7, P = 0.028), whereas no effect was detected for Arg supplementation. In conclusion, 1% l-Gln supplementation to postweaned rabbit diets decreased fattening mortality and modified the intestinal microbiota (although no consistent effects were observed on mucosal histology or inflammatory and systemic immune response). Diets containing a combination of 1% Gln and 0.5% Arg were of little additional benefit.

Prediction of the digestible energy and digestibility of gross energy of feeds for rabbits. 1. Individual classes of feeds

Near-infrared reflectance spectroscopy (MRS) was used to predict the nutritive characteristics of 66 compound rabbit feeds from three countries (Belgium, Spain and Italy) and the main ingredient inclusion rate in 59 of these feeds of known ingredient composition. Principal component analysis (PCA) was performed to classify the compound feeds according to their origin. The coefficient of multiple determination (R-2) for crude protein concentration (CP) was ca. 0.88 in both, calibration and validation with standard errors of calibration (SEC) and prediction (SEP) equal to 7.5 and 7.7 g (kg DM)(-1), respectively. NIRS prediction of gross energy (GE) and digestible energy (DE) concentrations was more precise, with high R-2 (0.90) and low SEP (0.26 and 0.37 MJ (kg DM)(-1), respectively). Satisfactory results were also obtained for both, the dry matter digestibility (DMd) and gross energy digestibility (GEd) prediction. The CP-correlated wavelengths were observed to be associated with the bond vibrations of the protein functional groups, while the wavelengths correlated with GE, DE, DMd and GEd were linked with starch, protein and crude fiber structure. The calibration on absorbance data to estimate the inclusion rate of the main ingredients demonstrated a fair correlation for alfalfa meal, barley and wheat bran, intermediate for sunflower meal and weak for soybean meal. In validation, the precision of the NIRS estimate remained satisfactory for alfalfa and sunflower meal but decreased for barley and wheat bran. The calibration of the spectra transformed in second derivative appeared to improve the quality of estimation by reducing the number of optimal factors from 9-15 to 2-4; moreover, the estimate precision of soybean and sunflower meal inclusions improved (R-2: 0.90 and 0.86, respectively) with the reduction of SEC (13.0 and 12.9 g kg(-1), respectively). In validation, however, the estimate precision for all raw materials became weaker than the degree achieved using absorbance data. PCA on the transformed spectra grouped the compound rabbit feeds according to their country of origin and indicated the possibility of identifying the presence of specific ingredients (i.e. full-fat rapeseed)

Effect of type of diet (casein-based or protein-free) and caecotrophy on ileal endogenous nitrogen and amino acid flow in rabbits

Abstract Apparent digestible energy (DE) and the coefficient of apparent digestibility of gross energy (GE D ) together with chemical analyses for 31 individual feedstuffs from two data sets were subjected to multiple linear regression analysis employing biological data as dependent variables and chemical data as independent variables. The best equations in terms of R 2 values were: DE (MJ kg −1 DM) = 12.912 − 0.0236CF + 0.010CP + 0.020EE ( R 2 = 0.924, RSD = 1.32) and GE D = 0.798 − 0.0014CF + 0.00025CP ( R 2 = 0.874, RSD = 0.079) where CF is crude fibre, CP is crude protein and EE is ether extract (all in g kg −1 DM). Groups of feedstuffs were subsequently classed separately into protein concentrates ( n = 11), energy concentrates ( n = 6), high fibre feedstuffs ( n = 6) and medium fibre/protein feedstuffs ( n = 8). Both beet and citrus pulps samples which had been evaluated in conjunction with a basal diet of high nutrient concentration, which produced abnormally slow rates of passage of digesta and consequently an overestimation of their nutritive value, were excluded from this analysis because it was considered that data for these two determinations would accordingly have been atypical. Improvements in accuracy of regression equations derived when compared with those obtained for all feedstuffs were confined to high fibre feedstuffs and medium fibre/ protein feedstuffs, although it was concluded that further studies would be necessary to confirm these observations.

Effect of diet on amino acid composition of soft faeces and the contribution of soft faeces to total amino acid intake, through caecotrophy in lactating doe rabbits

Twenty-eight New Zealand White X Californian doe rabbits weighing 3791±141 g were surgically fitted with a glass T-cannula at ileum level. Animals were given ad libitum access to either a casein-based diet (C) or a protein-free diet (PF). The only difference in the ingredient composition of the diets was the substitution of 160g/kg of maize starch by casein in the C diet. Animals were randomly allotted to each experimental diet. Seven rabbits per diet were not allowed to practice caecotrophy. The C diet resulted in higher food dry matter (DM) intake (DMI) (111-5 v. 51-5 g/day), food nitrogen intake (3-12 v. 0-20 g/day), ileal flow of DM (56-0 v. 23-8 g/day) and ileal flow of nitrogen (0-72 v. 0-24 g/day) but lower soft faeces DMI (21-7 v. 41-4 g/day) than the PF diet. A linear relationship between ileal endogenous nitrogen flow and total DMI was found for animals given the C but not for the PF diet. The ingestion ofC diet led to a higher (proportionately 0-41, on average), endogenous ileal amino acid flow than PF diet for all amino acids except for glycine. The ileal flow of glycine was proportionately 0-25 higher in animals given the PF diet than in animals given the C diet. The C diet resulted in higher content of nitrogen, threonine and proline in soft faeces than the PF diet. In contrast, the ingestion of the PF diet led to a higher content of lysine and methionine in soft faeces than the C diet. Within the C diet, animals practising caecotrophy showed higher ileal flow of DM (73-4 v. 56-0 g/day) and phenylalanine (0-834 v. 0-677 g/kg DMI) than animals not practising it. Caecotrophy led to a higher endogenous proportion of some of the most important limiting essential amino acids in rabbits, such as arginine, lysine, phenylalanine and threonine. In rabbits, the use of PF diets has limited practical application in the estimation of nitrogen endogenous losses as the low food DMI and the high soft faecesDMI leads to abnormal food: soft faeces intake ratio. Moreover, due to the important effect of caecotrophy on the amino acid composition of endogenous losses, it is important to correct the total amino acid content of the ileal chyme by the undigested amino acid residue coming from the soft faeces intake. This correction could be made, without the methodological complexity implied, by fitting animals with a wooden collar and thereby avoiding caecotrophy as in the present trial.

Effect of type of fiber, site of fermentation, and method of analysis on digestibility of soluble and insoluble fiber in rabbits.

Twenty-five New Zealand White × Californian lactating doe rabbits were used to study the effect of different dietary fibre concentrations on the amino acid contribution of soft faeces to the total amino acid intake. Five isoenergetic diets containing 312, 334, 360, 384, and 412 g/kg neutral-detergent fibre (DM basis) were formulated. All diets were designed to maintain the same amino acid pattern. Soft faeces production showed a trend to increase (P = 0·07) as dietary fibre increased. The content of isoleucine (P