Protein replacement by digestible fibre in the diet of growing rabbits. 1: Impact on digestive balance, nitrogen excretion and microbial activity

Social, ethical, environmental, economic and technological aspects of rabbit meat production - A critical review

Rabbit (RM) has become a valuable source of nutrients since the 1970s, helping to transform the European food industry into the largest RM producer in the world. However, the RM industry is experiencing a critical period of ethical imbalance. This trend, described as feed conversion ratio, impacts the environmental and financial performance of RM farms, which could lead to an increase production of industrial waste. In addition, the loss of corporate ethical responsibility and sustainable development by RM-oriented companies has further exacerbated the situation. Our objective was to summarize current trends in the RM industry and markets, highlighting possible strengths and weaknesses. This review shows current approaches in sustainable techniques in RM production processes, ethical issue, environmental and processing responsibility of RM producers, as well as social responsibilities and ethical practices of slaughterhouses and RM producers, sustainable environmental practices of slaughterhouses, technological aspects and safety of RM and social drivers in RM market. The analysis of reviewed literature revealed the potential strategies for sustainable RM production.

Dietary replacement of maggot meal for soybean meal: implication on performance indices, nutrient digestibility, nitrogen utilisation and carcass characteristics of grower rabbits

A study was conducted to investigate the effect of replacing soybean meal (SBM) with maggot meal (MM) in growing rabbits' diets on their performance, nutrient digestibility, and carcass characteristics. In the 56 days feeding trials, sixty unsexed mixed breeds (New Zealand White x California) rabbits were allotted on a weight equalization basis into five dietary treatments where a standard corn-soybean meal based diet (0% of maggot meal) (MM0 diet) served as the while other diets had soybean meal replaced with MM at graded levels of 25, 50, 75 and 100% to give MM25, MM50, MM75, and MM100 diets respectively. Each treatment comprises of four replicates having three rabbits each (12 rabbits per treatment). Growth performance parameters were monitored and recorded weekly, carcass and organ weights evaluation was conducted on day 56. Nutrient digestibility commenced on the 56th day and lasted for 6 days. Feed and water were offered to the rabbits ad-libitum throughout the experimental period. All the performance parameters were significantly (P < 0.05) affected by MM inclusion in the diet of rabbits. Rabbits fed MM100 diet had the highest (P < 0.05) final weight (FW), total weight gain (TWG), and the best feed conversion ratio (FCR). The feed cost reduced (P < 0.05) with inclusion of MM in rabbit's diet. Feed cost per kg live weight (FC/LW) (1110.79 ₦/kg) and feed cost per kg weight gain (FC/WG) (1110.62 ₦/kg) was lowest (P < 0.05) for rabbits fed MM100 diet. Crude protein digestibility (CPD) (74.05%) was highest (P < 0.05) for rabbits fed the MM100 diet. The feeding of MM75 and MM100 diets to rabbits resulted in increased (P < 0.05) dry matter digestibility (DMD) (68.22 and 69.34%), nitrogen free extract digestibility (NFED) (65.52 and 65.22%) and neutral detergent fibre digestibility (NDFD) (70.05 and 69.58%). The highest (P < 0.05) nitrogen retained (NR) (2.10 g/d) occurred in rabbits fed the MM100 diet. The dressing percentage (DP) (71.01%) increased (P < 0.05) for rabbits fed the MM100 diet. The weight of forelimbs (10.48 and 10.45%) and hind limbs (17.42 and 18.07%) were highest (P < 0.05) for rabbits fed MM50 and MM100 diets respectively. Total gastrointestinal tract (GIT) and liver weight were highest (P < 0.05) for rabbits fed MM0 and MM100 diets respectively. It was concluded that MM can conveniently replace SBM in the diets of rabbits up to 100% for improved growth performance and increased nutrient digestibility. In addition, it can enhance DP and increase the carcass yield of rabbits.

Dietary Inclusion of Crickets (Acheta domesticus) and Yellow Mealworm Meal (Tenebrio molitor) in Comparison with Soybean Meal: Effect on the Growth, Total Tract Apparent Digestibility, and Nitrogen Balance of Fattening Rabbits

Three diets were formulated, i.e., soybean meal (SM diet), adult Acheta domesticus (AD diet), and Tenebrio molitor larvae (TM diet), as the main crude protein (CP) sources. A total of 45 rabbits (Hyplus, weaned at 32 days of age) were divided into three groups (15 per treatment) and fed one of the three diets for 42 days. A higher daily weight gain (p = 0.042), as well as daily feed intake (p = 0.022), was observed in rabbits fed the AD and TM diets than in rabbits fed the SM diet within 21 days after weaning. The coefficients of total tract apparent digestibility (CTTAD) of gross energy were higher (p = 0.001) in rabbits fed the SM diet than in rabbits fed the other diets. The CTTAD of CP (p = 0.040) and starch (p = 0.041) was higher in rabbits fed the SM diet compared to those fed the AD diet. There were non-significantly higher losses of nitrogen in the urine (an average by 0.227 g/day; p = 0.094) in rabbits fed the TM diet than in rabbits fed the other diets. It can be concluded that the growth of rabbits and nitrogen output were not detrimentally affected by the insect meal (AD or TM) used in this study.

Growth Performance, Digestive Efficiency, and Meat Quality of Two Commercial Crossbred Rabbits Fed Diets Differing in Energy and Protein Levels

The present study evaluated the effect of digestible energy (DE) and crude protein (CP) levels on growth, digestive efficiency, slaughter yield and meat quality in growing rabbits of two genotypes (Grimaud, G vs. Hyla, H). A total of 384 crossbred rabbits (192 G and 192 H), half males and half females, were divided into eight experimental groups according to a bi-factorial arrangement (2 genotypes × 4 diets; 48 animals/group) and reared in individual cages. From 33 to 64 days of age, rabbits were fed four diets obtained by combining two DE levels (high, HE—10.9 MJ/kg vs. low, LE—9.2 MJ/kg, on average) and two CP levels (high, HP—159 g/kg vs. low, LP—144 g/kg, on average). Then, all rabbits received the same fattening diet (10.7 MJ DE/kg; 156 g CP/kg) until slaughtering (77 days of age). Growth performance did not differ between genotypes for the entire trial (on average final live weight 3010 g; daily weight gain 50.5 g/d), but H rabbits showed a faster growth during the post-weaning period (p ≤ 0.01) compared to G rabbits, while exhibiting lower slaughter yield and lower carcass fatness (p ≤ 0.01). As DE level increased, feed intake decreased and feed conversion improved (p < 0.001), while caecal volatile fatty acid concentration increased and caecal pH and N-ammonia decreased (p ≤ 0.01). The reduction in the CP level did not affect performance and carcass traits. No significant interaction was detected between genotype and diet. In conclusion, G rabbits may have an advantage over H rabbits because of the higher slaughter yield. As for the nutritional characteristics of diets for high-producing crossbred rabbits, high energy levels are confirmed to enhance feed efficiency, whereas dietary CP can be reduced to 144 g/kg without negative effects on performance and carcass traits.

Effects of replacement of alfalfa by big-leaf mulberry on growth performance, digestion and meat quality in growing rabbits

<p>This study aimed to investigate the effect of sundried big-leaf mulberry (BLM) as a replacement for alfalfa on the growth performance, digestibility of nutrients, nitrogen (N) utilisation and meat quality in New Zealand White rabbits. One hundred and sixty weaned rabbits, aged 35±1 d and with a body weight of 755±26 g, were randomly assigned to the 4 treatments with 20 replicates of 2 rabbits (1 male and 1 female) each. Animal performance was evaluated between the 35th and 77th d of age in 40 animals per treatment. The coefficients of total tract apparent digestibility (CTTAD) of nutrients and N utilisation were measured between 77 to 83 d of age in 30 animals per treatment. The control rabbits were fed a corn-soybean meal-alfalfa meal based diet. The three experimental groups were fed a similar diet in which the alfalfa meal was replaced by 10% (BLM10), 20% (BLM20), or 30% (BLM30) BLM. The final body weights and average daily gain were higher (<em>P</em>&lt;0.05) in BLM20 rabbits compared to control and BLM30 rabbits. Although BLM inclusion had no effects on the CTTAD of dry matter, organic matter and crude protein (<em>P</em>&gt;0.10), the CTTAD of ether extract was higher in rabbits fed the diets based on BLM (<em>P</em>&lt;0.05). No effect of treatment was noted on ingested and faecal N. Urinary (<em>P</em>&lt;0.05) and retained N (<em>P</em>&lt;0.10) were higher in animals fed with BLM30 and BLM20 diets, respectively. Dietary BLM supplementation increased a* (<em>P</em>&lt;0.05) and tended to reduce L* (<em>P</em>&lt;0.10) in rabbit meat samples. It was concluded that replacing alfalfa meal with BLM (20%) can promote growth and increase ether extract digestibility. Additionally, dietary BLM supplementation can increase the redness value of meat.</p>

Narrow-leaved lupine seeds as a dietary protein source for fattening rabbits: a comparison with white lupine seeds

Lupine seeds have the potential to be an alternative to imported dietary proteins. In rabbits, it has been indicated that White lupine seed (WLS) is a suitable protein source. Other lupine species, for example, narrow-leaved lupine seed (NLS), have not yet been tested in rabbit diets. Two experiments were carried out to evaluate the effect of the dietary inclusion of NLS on growth performance, sanitary risk index (SRI), coefficients of total tract apparent digestibility (CTTAD) and nitrogen output in fattening rabbits. Narrow-leaved lupine was compared with WLS as a main protein source. For Experiment I, a total of 198 Hyplus rabbits (37 days of age) were allocated into two groups (99 rabbits per group), fed the WLS I diet (120 g/kg of WLS cv. Amiga) or the NLS I diet (150 g/kg of NLS cv. Probor), and used for performance and carcass trait evaluations. In addition, the CTTAD of the diets and the nitrogen output were determined in 10 Hyplus rabbits per treatment (37 days of age). For Experiment II, a total of 180 Hyplus rabbits (32 days of age) were allocated into two groups (90 rabbits per group), fed the WLS II diet (120 g/kg of WLS cv. Amiga) or the NLS II diet (130 g/kg of NLS cv. Primadona), and used for performance and carcass trait evaluations. In addition, the CTTAD of the diets was determined in 10 Hyplus rabbits per treatment (32 days of age). Regardless of the treatment, the dietary inclusion of NLS had a negative effect on growth of the rabbits. The nitrogen excretion and coefficients of nitrogen retention of rabbits were not affected by the treatments. In Experiment I, SRI (37 to 80 days of age) was higher in rabbits fed the NLS I diet than in those fed the WLS I diet (38.4% v. 23.2%, respectively; P = 0.031). Similarly, in Experiment II (32 to 74 days of age), SRI was higher in rabbits fed the NLS II diet than in rabbits fed the WLS II diet (37.8% v. 23.3%, respectively; P = 0.052). In conclusion, regardless of the variety, the dietary inclusion of NLS had no negative effect on the nitrogen output or dressing-out percentage of rabbits when compared to those of rabbits fed the WLS diets. With respect to the SRI and performance, however, NLS did not provide a satisfactory outcome.

Direct and correlated responses to selection in two lines of rabbits selected for feed efficiency under ad libitum and restricted feeding: III. Digestion and excretion of nitrogen and minerals

Two rabbit lines have been created to result in better feed efficiency: the ConsoResidual line was selected for a lower residual feed intake under ad libitum feeding, and the ADGrestrict line was selected for higher ADG under restricted feeding (-20% of ad libitum). The present study aimed to analyze the digestion and excretion of N and minerals from 29 to 63 d of age of these 2 lines compared with an unselected control line (G0) under 2 feeding levels (ad libitum or restricted). The ADGrestrict line had greater digestibility compared with G0 (+1.3% for OM and N; < 0.05), and the ConsoResidual line had intermediate values. There was no genetic line effect on the digestibility of N and P and on minerals concentrations (P, Zn, and Cu) in the feces and in the urine. The N balance was improved for the 2 selected lines (+5%; < 0.05), leading to a reduced N output through the feces (0.06 g/d compared with G0; < 0.001) and the urine (-0.07 g/d; < 0.05) and to an improved N retention ratio (+3% compared with G0). Over the whole fattening period (d 29-63), significant differences were observed among lines only when fed ad libitum, with 13% greater DM fecal output and 5% greater N fecal output for G0. The N excretion in urine was 2 g less in the 2 selected lines, leading to a reduction of total N release of 4.4 g (compared with G0). The P excretion in feces (12 g) or urine (0.1 g) did not differ among the 3 lines. Over the whole fattening period and for ad libitum-fed rabbits, the 5% improvement in feed efficiency ( < 0.01) for the 2 selected lines corresponded to 400 g less feed intake (-8%) and to 20 g less N intake. The fecal excretion of the ADGrestrict and ConsoResidual lines were reduced by 200 g DM ( < 0.01), corresponding to 417 g fresh matter and 5 g of N. The excretion in minerals (P, Zn, and Cu) was not affected by the line. The feeding level strongly reduced the fecal and urine outputs (-50 and -60%, respectively; < 0.001). Higher digestibility coefficients ( < 0.001) were found in restricted-fed rabbits for OM (+6%), N (+8%), and P (+11%). The N balance was substantially improved by the restriction, with 40% less total (feces + urine) N excretion ( < 0.001). The P balance was improved by the restriction (0.469 vs. 0.360). Over the fattening period, the P fecal output was 37% less (-6 g) with 24% less feed intake and the Zn and Cu outputs were reduced by 27 (-130 mg) and 29% (-30 mg), respectively.

Effect of feed restriction and feeding plans on performance, slaughter traits and body composition of growing rabbits

Two feeding systems (L, <em>ad libitum vs. </em>R, feed restriction) were combined with 3 feeding plans (MM, MH, HH) to evaluate the effects on performance, slaughter results, body composition and nitrogen balance of 300 commercial crossbred rabbits kept individually from weaning to slaughter (34-70 d of age). The R rabbits were fed from 80% (first days on trial) to 100% (end of 3rd wk) of <em>ad libitum </em>intake, whereafter R rabbits had free access to feed. The 3 feeding plans were: MM plan, M diet with moderate digestible energy (DE) content, 10.6 MJ/kg, throughout the trial; HH plan, H diet with high DE content, 11.1 MJ/kg, throughout the trial; MH plan, M diet for the first 3 wk and H diet for the last 2 wk. Feed restriction did not affect nutrient digestibility, growth rate on the whole trial and slaughter results, but improved feed conversion (2.96 <em>vs. </em>2.89 in L and R rabbits, respectively; <em>P</em>&lt;0.01) and reduced N excretion (2.16 <em>vs. </em>2.07 g excreted N/d, in L and R rabbits; <em>P</em>&lt;0.05). At the end of the first period (55 d), R rabbits showed lower empty body protein, lipid, and gross energy gains than L rabbits, but differences disappeared within the end of the trial. The HH plan improved feed conversion (2.97 <em>vs. </em>2.89 for MM <em>vs. </em>HH; <em>P</em>&lt;0.05), but increased excreted N (2.03 <em>vs. </em>2.17 g/d; <em>P</em>&lt;0.001) in comparison with the MM plan due to the higher digestible protein/DE ratio of H diet, whereas the MH plan showed intermediate results. In conclusion, a moderate feed restriction during post weaning improved feed conversion and reduced N excretion without negative effects on growth or slaughter results. Moreover, N excretion was confirmed to depend largely on dietary nitrogen content.

Stimulate feed intake before weaning and control intake after weaning to optimise health and growth performance

<p>Post-weaning feed restriction is a common practice in rabbit farming to reduce mortality, but results in lower growth performance and slaughter weights. This study aimed to assess the influence of 2 diets both rich in fibre and low in starch, with high or low digestible energy (DE) and digestible protein (DP) contents for a constant DP/DE ratio offered from 18 to 70 d of age, on the growth performance and health parameters of rabbits. Eight hundred rabbit kits were divided in 2 experimental groups differing in the feed offered from 18 to 70 d: a high concentrate diet (HC group; 10.37 MJ DE/kg DM and 102 g DP/kg DM) or low concentrate diet (LC group; 9.63 MJ DE/kg DM and 95 g DP/kg DM). Feed was offered ad libitum before weaning (35 d) and from 63 to 70 d, while feed offered from 35 to 63 d was controlled to obtain similar DE intake in both groups. Feed intake, animal weights and health status were recorded weekly. Mortality was recorded daily. Feed intake was similar in both groups before weaning (P=0.204), and consequently the DE intake was higher in the HC group compared to the LC group before weaning (3.91 vs. 3.39 MJ, respectively; P=0.017). Feed intake from 63 to 70 d was lower in the HC than in the LC group (229 vs. 239 g/d/kit, respectively; P&lt;0.001).<br />Total DE ingested after weaning was similar in both groups (45.44 MJ; P=0.143). Kits were heavier in the HC group throughout the study (P&lt;0.05). A higher average daily gain during the periods of 18-28, 35-42 and 56-63 d was seen in the HC group (+8.1%, +16.8% and +4.5%, respectively; P&lt;0.05). Mortality and morbidity rates were similar between groups throughout the study (P=1.0 and P=0.104, respectively). Our results suggest that when the feed intake after weaning is controlled, i) the feeding strategy before weaning determines the weight at weaning and at slaughter age; and ii) rabbits fed a diet more highly concentrated but rich in fibre increase their growth performance without negative consequences on their digestive health.</p>