J. C. de Blas

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.

Processed cereals in diets for early-weaned piglets

Two trials were carried out to study the influence of cereal processing in diets for early-weaned piglets. Six diets were formulated on an alternate base of two cereals: barley or maize, and three types of processing: control (raw), extrusion and micronization according to a factorial arrangement. In Trial 1, 120 male piglets weaned at 23 days and weighing an average of 6.4 kg, were randomly affected by litter in successive blocks and used in a 25-days performance trial. In Trial 2, 18 piglets, three animals per treatment, were used to measure apparent faecal digestibility of dry matter (DMD), organic matter (OMD), energy (ED), crude protein (CPD) and neutral detergent fibre (NDFD). Ileal viscosity, and pH of stomach, caecum and colon were also performed. In Trial 1, piglets fed barley-based diets grew faster than piglets fed diets based on maize (423 versus 404 g/ d; Pa 0.04). Heat processing of the cereal improved daily gain (423 versus 396 g/d, Pa 0.01) and feed conversion ratio (1.18 versus 1.25 g/g, Pa 0.02) with respect to diets based on raw cereal. An interaction between type of cereal and heat processing was observed for the first 2 weeks of the experiment: the improvement in daily gain associated with heat treatment was higher for barley than for maize (13.7 versusˇ4.3%; Pa 0.08). The same occurred for feed efficiency (ˇ14.5 versus 3%; Pa 0.06). No differences were detected between types of processing for growth or feed efficiency. In Trial 2, maize-based diets had higher DMD (0.908 versus 0.871; P < 0.001), OMD (0.921 versus 0.880; P < 0.001), ED (0.905 versus 0.863; P < 0.001), CPD (0.886 versus 0.860; Pa 0.04) and NDFD (0.795 versus 0.708; Pa 0.03), than barley-based diets. Processing of cereals increased digestibility of nutrients but only OMD was improved significantly (0.908 versus 0.886; Pa 0.05). Neither ileal viscosity nor pH of stomach and caecum contents were affected by the experimental treatment. Maize-based diets reduced colon pH compared to barley-based diets (6.18 versus 7.00; P < 0.01). It is concluded that processing of cereals improves performance and OMD of diets for piglets and that this improvement is higher for barley than for maize. # 1999 Elsevier Science B.V. All rights reserved.

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 type and level of fish oil supplementation on yolk fat composition and n-3 fatty acids retention efficiency in laying hens

1. Laying hen performance and yolk fat fatty acid (FA) concentrations were evaluated with respect to the inclusion in the diet of different sources and levels of marine fish oil (MFO). 2. Twelve diets were arranged factorially, with three sources (MFO1, MFO2_EPA, MFO3_DHA) and four levels of inclusion (15, 30, 45 and 60 g/kg) of MFO. 3. Type of diet had little effect on egg production traits, although laying rate and shell thickness slightly decreased at the highest level of MFO supplementation. 4. An increase in level of inclusion of MFO from 15 to 60 g/kg linearly increased concentrations of C20:5 n-3, C22:5 n-3, C22:6 n-3 and total n-3 FA in yolk fat, but greatly impaired their efficiencies of deposition (g retained/g ingested). 5. An interaction between type and dietary concentration of MFO was found, as the reduction in efficiency of retention of n-3 FA in egg fat with level of MFO was less when the proportion of n-3 in total FA decreased or when that of DHA in total n-3 FA increased. 6. MFO3_ DHA was more efficiently used for total n-3 FA yolk deposition than MFO2_EPA at a similar total n-3 FA intake. 7. Dietary inclusion of MFO reduced LC n-6 FA yolk fat content, which additionally decreased the ratio between total n-6 and total n-3 FA in egg fat. 8. Regression equations were calculated in order to predict efficiency of retention and n-3 FA concentration of yolk fat in the range of diets studied.

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

Effects of dietary conjugated linoleic acid and fish oil supplementation on performance and egg quality in laying hens

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.

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

1. Laying hen performance, yolk fat fatty acid concentrations and firmness of eggs were evaluated with respect to the inclusion in the diet of conjugated linoleic acid (CLA) and fish oil. 2. Nine diets were arranged factorially, with three levels of supplementation of CLA (1, 3 and 5 g/kg) and fish oil (0, 14 and 20 g/kg). 3. Type of diet did not affect egg production traits. 4. CLA addition increased yolk weight and yolk fat concentrations of CLA, saturated and total long-chain n-3 fatty acids, but decreased those of monounsaturated and total long-chain n-6 fatty acids. 5. Fish oil addition increased long-chain n-3 fatty acids yolk fat concentrations but decreased those of CLA, saturated and long-chain n-6 fatty acids. 6. Effects of CLA addition on yolk fat concentrations of C22:4 n-6 and C20:5 n-3 were greater when no fish oil was added to the diet. 7. CLA supplementation increased linearly yolk moisture and firmness and altered albumen and yolk pH.

A note on the use of sodium hydroxide treated straw pellets in diets for growing 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.

Effects of dietary conjugated linoleic acid and high-oleic sunflower oil on performance and egg quality in laying hens

The effects of the inclusion of increasing quantities of cereal straw treated with sodium hydroxide in the diet of rabbits weie studied on 68 animals, both males and females, of the Spanish Giant and New Zealand × Spanish Giant breeds, weaned at different weights. The nitrogen and fibre digestibilities, the overall growth rate (from weaning to 2·25 kg) and the partial growth rate (from weaning to 2 weeks after weaning) increased linearly, while the feed conversion rate decreased when the content of treated straw in the feed was raised. The overall growth rate for males was significantly higher ( P P P P P P P

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

1. Laying hen performance, yolk fatty acid (FA) concentrations, sensory quality and firmness of eggs were evaluated with respect to the inclusion in the diet of conjugated linoleic acid (CLA) and high-oleic acid sunflower oil (HOSO). 2. Nine diets were arranged factorially, with three concentrations of CLA (0, 1 and 2 g/kg) and HOSO (10, 20 and 30 g/kg). 3. Type of diet did not affect egg production traits. 4. Dietary addition of CLA decreased yolk lipid content and yolk lipid concentrations of monounsaturated FA, C20:4 n−6 and C22:6 n−3, but increased those of CLA and saturated FA. 5. Dietary addition of HOSO increased monounsaturated FA concentrations in the yolk lipid but decreased those of CLA and saturated FA. 6. CLA supplementation increased yolk moisture and firmness and impaired the sensory quality of eggs. 7. An interaction between CLA and HOSO addition was found as effects of CLA addition on yolk lipid CLA concentrations and egg quality traits were smaller when the amount of HOSO in the diet increased. 8. Regression equations have been calculated in order to predict yolk CLA and C18:1 concentration from dietary composition, and yolk firmness from yolk FA composition.