A. Dalle Zotte

Effect of dietary energy level, addition of fat and physiological state on performance and energy balance of lactating and pregnant rabbit does

The effects of dietary energy level and added fat were studied by comparative slaughter on 60 primiparous rabbit does in different reproductive states. Nine does were slaughtered immediately after their first parturition (preliminary slaughter group) to estimate initial empty body composition. The 51 remaining does were divided into three groups and given diets differing in digestible energy (DE) content: M (11·28 MJ/kg dry matter (DM); H (12·16 MJ/kg DM); F (11·93 MJ/kg DM, obtained by the inclusion of 25 g/kg of animal fat). Thirty-six does (12 per group) were remated 3 to 4 days after parturition, after which 20 does were concurrently pregnant and lactating (LP) and gave birth a second time. At the second parturition these does were slaughtered with their new-born litters. The non-mated or non-pregnant lactating does (LN) were slaughtered at the same time. All litters from the first parturition were weaned at the 30th day of age. The diets influenced the DE intake (3·11 v. 3·31 and 3·36 MJ/day, P v. 180 v. 191 glday, P 0·05) (average of LP and LN does). The maternal diet significantly influenced the weight of the sucking litters (first parturition) at 20 days (2409 and 2454 v. 2629 g, P The LP does showed lower DE intake, milk yield (from 10 to 30 days) and litter weaning weights than LN does. Between the first and the second parturition, the LP does had a loss of empty body weight and a negative protein balance (-0·06 of the initial content), while the LN does had an increase in live weight and empty body weight and a positive protein balance (+0·11 of the initial content). Both LP and LN does had a negative energy balance (−0·24 v. −0·25, respectively; P

Effect of genetic origin, diet and weaning weight on carcass composition, muscle physicochemical and histochemical traits in the rabbit

Fifty rabbits originating from the crossing of one dam strain with three sire strains, Hy+, INRA 9077 and INRA 3889, were studied. The adult body weights of the sire strains were 5·1, 4·1 and 3·1kg, respectively. After weaning, the Hy+ and the INRA 9077 rabbits were fed either an H (11·99MJ DEkgDM(-1)) or L diet (9·67MJ DEkg DM(-1)). The INRA 3889 rabbits were fed only the H diet. In each of these five blocks, two weaning weights were studied and the rabbits were slaughtered when the average body weight of each block reached 2·5kg. Slaughter yield, carcass fatness and hindleg meat to bone ratio were determined. Muscular tissue was described using (1) physicochemical criteria (ultimate pH, L(*)a(*)b(*) colour) of the biceps femoris (BFE), tensor fasciae latae (TFL) and semimembranosus accessorius (SMA) muscles and (2) histochemical characteristics of the longissimus lumborum muscle (LL) through computerised image analysis (fibre type composition, cross-sectional area). At slaughter, the rabbits of INRA 3889 sire origin, which had the highest degree of maturity (72%), gave the best slaughter yield (p<0·01), the heaviest reference carcass weight (p<0·01), and highest LL proportion (p<0·01), hindleg meat to bone ratio (p<0·05) and fatness (p<0·01); their LL muscle showed the lowest percentage of βR fibres, while the cross-sectional area of their muscular fibres was the highest (p<0·05). When all sire × diet combinations were put together, the heavier the weaning weight, the lower the daily gain (p<0·01) and the lightness (L*) of thigh muscles (p<0·05). The lower the DE content of the diet, the lower the growth rate, the slaughter yield, the reference carcass weight (p<0·01) and the cross-sectional area of all types of muscle fibres of the rabbits of both Hy+ and INRA 9077 sire origin.

Effect of feed rationing during post-weaning growth on meat quality, muscle energy metabolism and fibre properties of Biceps femoris muscle in the rabbit.

During the weaning period (5 weeks of age), 50 hybrid rabbits were divided at random into five groups (or blocks). Animals from the block 1 were immediately slaughtered at this age and used as initial reference. The remaining rabbits were placed in individual cages and fed the same amount of food until slaughter, but differently rationed. From 5 to 8 weeks of age, the rabbits coming from blocks 2 and 4, and from blocks 3 and 5 received 70% and 90% of the ad libitum ration, respectively. Animals of blocks 2 and 3 were slaughtered at 8 weeks of age. Between 8 and 11 weeks of age, animals from blocks 4 and 5 were fed, respectively, 90% and 70% of the ad libitum ration, prior to sacrifice. At slaughter the Biceps femoris (BF) muscles were immediately removed from each rabbit and the ultimate pH (pHu) and meat colour L*a*b* parameters were measured. Thereafter, one BF was used for aldolase and isocitrate dehydrogenase (ICDH) activity determinations, while the other BF muscle was used for fibre distribution (% of βR, αR and αW) and morphometric trait measurements. As expected, at 8 weeks of age, rabbits given for 3 weeks the strictest feed rationing (70% of the ad libitum ration) were lighter than rabbits fed the lowest feed rationing (90% of the ad libitum ration). At 11 weeks of age, rabbits given the 70% ration initially and then switched to 90% ration showed significantly higher body weights than rabbits fed the alternative diet (90% ration initially and then switched to 70% ration), and the best feed conversion ratio. Fibre type distribution, fibre cross-sectional area and compactness, colour and metabolic characteristics varied according to slaughter age. The effects of feeding treatment were low.

Effect of age, diet and sex on muscle energy metabolism and on related physicochemical traits in the rabbit.

Muscle energy metabolism and related physicochemical traits of the meat were studied in 84 Provisal hybrid rabbits of both sexes. From weaning (30 days) to 55 days of age, the rabbits were divided into 4 groups which were given ad libitum one of the following diets: H diet with high digestible energy (DE) level, L diet with low DE level, F diet with high DE level, obtained by supplementing with animal fats, and W diet with moderate DE level. The H, L and F diet were suitable for lactating does and weaning rabbits; the W diet for weaned young rabbits. From 55 days to slaughter age, the rabbits were given a G diet suitable for growing and fattening. The rabbits were slaughtered at 55 days (23 rabbits), 80 days (31 rabbits) or 87 days (30 rabbits) of age. The activity of a representative enzyme of the glycolytic (fructose-1,6-diP aldolase) and oxidative (NADP-isocitrate dehydrogenase: ICDH) energy metabolism pathways and two related physicochemical traits, namely lightness (L (∗)) and ultimate pH (pH(u)), were determined in the biceps femoris (BF) and longissimus lumborum (LL) muscles. The chemical composition of whole longissimus dorsi (LD) and total hindleg (HL) muscles was also determined. In BF and LL muscles, the activity of the glycolytic energy metabolism increased during the fattening period, as a result of metabolic differentiation. The increase stopped earlier in BF than in LL muscle. Variations in pH(u) values followed the same trend. The dietary effect on biochemical and physicochemical traits was moderate. A slight decrease in muscle pH(u) was observed under the less energetic diets. Aldolase activity was significantly higher in females. The significant correlations between metabolic and physicochemical traits confirmed that as glycolytic energy metabolism increases, the protein content increases, whereas pH(u) decreases. Slaughter weight was positively correlated to glycolytic energy metabolism.

Effect of dietary supplementation of Spirulina (Arthrospira platensis) and Thyme (Thymus vulgaris) on rabbit meat appearance, oxidative stability and fatty acid profile during retail display

The objective of this study was to evaluate the effect of Spirulina and Thyme supplementation on rabbit meat during retail display. At weaning 294 rabbits were allocated to 7 different treatments (42 rabbits/treatment). Rabbits of the control group (C) received a diet without any supplementation throughout the experiment (5-11 weeks of age). The other groups were fed diets containing 5% Spirulina (S), 3% Thyme (T) or both supplements (ST) for the whole trial (5-11 weeks; treatments S, T and ST), or for a part of the growing period (8-11 weeks; treatments C-S, C-T and C-ST). Colour parameters, pH, water holding capacity and drip loss were determined on fresh and stored Longissimus dorsi muscle of 5 rabbits/treatment. Spirulina- and Thyme-supplemented diets had a significant effect on redness and yellowness of Longissimus dorsi. Drip loss was significantly reduced in C-T and T groups that also showed the highest content of α-tocopherol and n-3 fatty acids content and the lower lipid oxidation.

Post-weaning evolution of muscle energy metabolism and related physico-chemical traits in the rabbit.

Metabolic differentiation in muscles was analysed in 50 rabbits of New Zealand White breed (strain INRA 1077) slaughtered at 28, 42, 56, 70 or 84 days. The activity of enzymes representing the glycolytic (fructose 1,6-diP aldolase) and the oxidative (NADP-isocitrate dehydrogenase) (ICDH) energy metabolism pathways, and two related physico-chemical traits, haem pigment content and ultimate pH, were estimated in semimembranosus proprius + soleus, psoas major and longissimus lumborum muscles. Aldolase activity was lowest in semimbranosus proprius + soleus, which are pure βR and the most precociously developed muscles, whereas haem pigment content and ultimate pH were highest; however, physico-chemical traits changed moderately during growth. In the psoas major (pure αW) and in the longissimus lumborum (mixed muscle), which develop later, aldolase activity increased until the 56th and 70th day respectively. The decrease in ICDH activity lasted longer, especially in the longissimus lumborum muscle. A significant negative relationship between aldolase activity and ultimate pH may explain why the ultimate pH decreased during fattening.

Black soldier fly as dietary protein source for broiler quails: apparent digestibility, excreta microbial load, feed choice, performance, carcass and meat traits

In order to expand with validated scientific data the limited knowledge regarding the potential application of insects as innovative feed ingredients for poultry, the present study tested a partial substitution of soya bean meal and soya bean oil with defatted black soldier fly (Hermetia illucens) larvae meal (H) in the diet for growing broiler quails (Coturnix coturnix japonica) on growth performance, mortality, nutrients apparent digestibility, microbiological composition of excreta, feed choice, carcass and meat traits. With this purpose, a total of 450 10-day-old birds were allocated to 15 cages (30 birds/cage) and received three dietary treatments: a Control diet (C) and two diets (H1 and H2) corresponding to 10% and 15% H inclusion levels, respectively (H substituted 28.4% soya bean oil and 16.1% soya bean meal for H1, and 100% soya bean oil and 24.8% soya bean meal for H2, respectively). At 28 days of age, quails were slaughtered, carcasses were weighed, breast muscles were then excised from 50 quails/treatment, weighed, and ultimate pH (pHu) and L*, a*, b* colour values were measured. Breast muscles were then cooked to assess cooking loss and meat toughness. For the digestibility trial, a total of 15 28-day-old quails were assigned to the three feeding groups. The excreta samples were subjected to chemical and microbiological analysis. The same 15 quails were then simultaneously provided with C and H2 diets for a 10-day feed choice trial. Productive performance, mortality and carcass traits were in line with commercial standards and similar in all experimental groups. With the exception of ether extract digestibility, which was lower in H1 group compared with C and H2 (P=0.0001), apparent digestibility of dry matter, CP, starch and energy did not differ among treatments. Microbial composition of excreta was also comparable among the three groups. Feed choice trial showed that quails did not express a preference toward C or H2 diets. Breast meat weight and yield did not differ among C, H1 and H2 quails. Differently, the inclusion of H meal reduced meat pHu compared with C. In conclusion, this study demonstrated that H. illucens larvae meal can partially replace conventional soya bean meal and soya bean oil in the diet for growing broiler quails, thus confirming to be a promising insect protein source for the feed industry. Further research to assess the impact of H meal on intestinal morphology as well as on meat quality and sensory profile would be of utmost importance.

Effect of dam and sire genotypes on productive and carcass traits of rabbits

The aim of the experiment was to study the effect of dam and sire genotypes on the production and slaughter performance of growing rabbits. The experiment was carried out at Kaposvár University. Pannon White (PW) and maternal line (M) does were inseminated with the sperm of PW, M, large body line (LB), terminal line of Hycole hybrid (H), or colored line (CL) bucks. The mature body size of the M, PW, and CL genotypes was medium. The mature body size of the LB and H genotypes was large. Only PW and LB rabbits were selected for carcass traits based on computer tomograph (CT) scanning data. The rabbits (n = 320) were weaned at the age of 5 wk and housed in a closed climate-controlled rabbitry in wire cages. Rabbits were fed ad libitum a commercial pellet. Rabbits were slaughtered at 78 d of age. Daily BW gain (5.7%, P < 0.001) and G:F (6.2%, P < 0.001) of the progeny of PW does were better than those of the progeny of the M does. The weight of the chilled carcass and body parts was greater for the progeny of the PW does (P < 0.001). The ratio of the hind part compared with the reference carcass was greater in the PW group (P < 0.001); however, the ratio of the fore part was greater in the M group (P < 0.05). Examining the effect of the genotype of the sires, the BW and daily BW gain were greater in groups H and LB, whereas the progeny of M and CL sires were inferior (P < 0.05). Body weights at 11 wk of age were H: 2,918 g, LB: 2,793 g, PW: 2,678 g, CL: 2,636 g, and M: 2,585 g (P < 0.001). Similar differences were found for daily feed intake (P < 0.05). The G:F differed (P < 0.05) significantly between groups H and CL. The weights of the chilled carcass and of the body parts were the greatest for the progeny of the H sires, and the smallest in the M group. The differences between the dressing out percentages of the groups were not significant. The ratio of the fore part was greater (P < 0.05) in groups LB, H, and CL, but the ratio of the middle part was not different. The ratio of hind part related to the reference carcass was largest in progeny of PW and least in LB and CL groups (P < 0.05). It was concluded that the production of growing rabbits was affected by the adult BW of their sires, but the carcass traits were influenced by their own adult BW and by the CT-based selection.

Effect of an outdoor rearing system on the welfare, growth performance, carcass and meat quality of a slow-growing rabbit population

The effect of Outdoor or Indoor housing systems on the growth, welfare and carcass and meat quality of a local rabbit population was investigated. The slaughter age was 103±2days. Open-field tests showed an effective capacity of the Outdoor group to combat stressors. Compared to Indoor rabbits, Outdoor rabbits showed better growth performance and higher slaughter weight (SW) (2535 vs 2137g; P<0.01). Outdoor housing conditions increased the physical activity of rabbits and their hind legs were more developed (36.1% vs 34.9%; P<0.01). Slaughter yield was lower in Outdoor rabbits (57.8% vs 58.4% SW; P<0.05) due to the higher skin proportion (17.2% vs 15.6% SW; P<0.05). Outdoor rabbit meat showed lower L∗ value (L. lumborum: 55.6 vs 59.2; P<0.01; B. femoris: 53.0 vs 55.5; P<0.01) and cooking loss (L. lumborum: 15.9% vs 18.1%; P<0.05). Outdoor rabbit hind leg meat was characterized by lower water (74.5% vs 75.1%; P<0.01) and higher protein (22.9% vs 22.6%; P<0.01) and fat (1.4% vs 1.1%; P<0.01) contents; lipids were lower in SFA and higher in MUFA. Outdoor rearing seems to be a possible alternative housing system that allays the ethical concerns of modern consumers while also providing good meat quality.

Effect of housing conditions on production, carcass and meat quality traits of growing rabbits

Production, carcass traits and meat quality of rabbits housed in cages or in different pens were compared. Rabbits (n=579) were sorted into 5 groups: C=cage (2 rabbits/cage); pen without platform: P11=9 rabbits/pen; P16=14 rabbits/pen; pen with platform: PW=wire net platform, 14 rabbits/pen; PD=platform with straw-litter, 14 rabbits/pen. Feed intake and average daily gain between 5 and 11 weeks, and body weight at 11 weeks were significantly higher in C rabbits than that of the mean of pen-housed groups, while the PD group had the lowest growth performance. C rabbits had the smallest hind part to reference carcass (P<0.001) and the largest percentage of perirenal and scapular fat (P<0.001). The meat/bone ratio was the largest in group C (P<0.05). Differences were recorded in a* value and lipid content of m. Longissimus dorsi. Rabbits housed in cages generally had the best performance whereas those housed in pens with platform exhibited the worst.