Are dual-purpose and male layer chickens more resilient against a low-protein-low-soybean diet than slow-growing broilers?

1. Although fattening dual-purpose types or male layer hybrid chickens appears more ethical than the common practice of culling day-old male layer chicks, the lower feed efficiency of these birds raises concerns. Replacing feed ingredients that compete with food production by those of lower value for human nutrition would be beneficial.2. Lohmann Dual (LD), a modern dual-purpose type, Lohmann Brown (LB), a male layer hybrid, and Hubbard JA 957 (HU), a slow-growing broiler type, were fattened for nine weeks on two diets (control or -20% crude protein; n = 6 × 12 birds). Growth, carcass and meat quality were analysed.3. Growth performance of HU exceeded that of LD and especially of LB. The growth depression caused by the low-protein diet fed to LD (-7%) was only half of that found in HU (-13%). The LD fed the control diet had the same feed efficiency as the HU fed the low-protein diet. Even the LB had a lower performance and feed efficiency with the low-protein diet in growth. There was a gradient in carcass properties (weight, dressing percentage, breast meat yield, breast proportion and breast angle) from HU to LD to LB, with some additional adverse effects of the low-protein diet especially in HU. There were some breed differences in fatty acid profile in the intramuscular fat.4. In conclusion, the dual-purpose type used complied with regulations for Swiss organic poultry systems in terms of growth rate and was found to respond less when fed a low-protein diet than the slow-growing broiler type. The LB males were inferior in all growth and carcass quality traits. Future studies need to determine the exact protein and amino acid requirements of dual-purpose and layer hybrid chickens and the economic feasibility of the systems, especially for organic farming.

Carcass and meat quality of dual-purpose chickens (Lohmann Dual, Belgian Malines, Schweizerhuhn) in comparison to broiler and layer chicken types.

Currently, there is an intensive ethical discussion about the practice of culling day-old layer cockerels. One solution to avoid this practice could be using dual-purpose types, where males are fattened for meat and females used for egg production. The aim of the present study was to compare fattening performance, carcass conformation, and composition as well as meat quality of Lohmann Dual, a novel dual-purpose type, and 2 traditional dual-purpose types (Belgian Malines and Schweizerhuhn) with 2 broiler types and 1 layer type (Lohmann Brown Plus). Broilers included a conventional line (Ross PM3) and a slower-growing line (Sasso 51) fulfilling requirements of organic farming. Nine birds of each type were fed on a conventional broiler diet. Feed intake and metabolizability of nitrogen and energy were recorded per pen (n = 3), the latter through excreta sampling. For each bird, carcass conformation was assessed, and weights of body, carcass, breast meat, legs, wings, and inner organs were determined. Additionally, breast angle, an indicator for carcass appeal, and skin color were recorded. Meat quality assessment included determinations of thaw and cooking loss, shear force, meat color, and proximate composition of the breast meat. None of the dual-purpose types (20 to 30 g ADG) performed as well in growth as the intensively growing broiler line (68 g ADG). However, Lohmann Dual could compete with the slower-growing broiler line (slower growth but better feed efficiency, similar in carcass weight and breast proportion). Also breast angle was quite similar between Lohmann Dual (100°) and the extensive broiler type (115°C) compared to the intensive broiler line (180°). Meat quality was most favorable in the intensive broilers with the smallest shear force and thawing loss, whereas meat quality was not different between the other types. The Schweizerhuhn performed only at the level of the layer hybrid, and the Belgian Malines was ranked only slightly better.

Swiss consumers' willingness to pay and attitudes regarding dual-purpose poultry and eggs.

Chick culling is an efficient and cost-effective method in modern poultry farming, but it raises ethical concerns. Dual-purpose poultry (DP), in which males are fattened and females are used for egg production, is currently the most realistic alternative to culling, as in ovo sexing is not yet viable for practical application. Consumers' acceptance of DP products and their willingness to pay (WTP) for them have not been studied yet, and we expect that both aspects are closely related to the acceptance of and WTP for products from systems claiming beyond-conventional animal welfare, such as organic products. Results from a survey conducted among 402 consumers at 8 Swiss supermarkets revealed that the practice of chick culling was largely unknown (75% of respondents). Generally, respondents' knowledge about poultry production was low. The DP alternative was preferred to chick culling, but no preference emerged between DP and in ovo sexing. Furthermore, the WTP for DP products was proportionally lower for chicken than for eggs, probably because of the different price elasticity between these products. A regression analysis was used to determine the factors influencing consumers' WTP for DP products. Consumers' WTP was positively related to knowledge about poultry production, habits tied to purchasing organic or free-range poultry products, and familiarity with DP products. Therefore, a combination of the DP alternative with an organic label is recommended.

Differences between spent hens of different genotype in performance, meat yield and suitability of the meat for sausage production.

The valorization of spent hens via the food chain has some major limitations, which include low meat yield and tough meat. The latter issue can be overcome by producing convenience foods; the first may be alleviated by employing a genotype with higher meatiness. To quantitatively compare two common layer genotypes in production performance, meat yield and sausage quality, 2200 57 weeks old Institut de Sélection Animale (ISA) Warren and Dekalb White hens each were investigated during the last 60 days of egg laying. The hens were housed in an aviary system in 2×10 compartments (10 compartments/each genotype). Measurements included feed intake, laying performance, egg weight and feed conversion ratio as measured per compartment. BW was determined twice on 10 animals per compartment. Finally, two sub-groups of five hens per compartment were slaughtered, meat yield was recorded and bratwurst-type sausages were produced (n=20 per genotype). Fat proportion, cooking loss, connective tissue properties and Kramer shear energy were measured. After 1, 4, 7 and 10 months of frozen storage, oxidative stability (thiobarbituric acid reactive substances (TBARS)) and microbiological status were determined as shelf-life related criteria. ANOVA was performed considering genotype as the main effect. The ISA Warren hens were inferior in laying performance (-11%) and feed conversion ratio (+10%) compared with Dekalb White, but had the same feed intake. The ISA Warren had higher BW and carcass weight than the Dekalb White. Carcass yield was higher by 5.9%. There were 80 g (23%) more meat available for sausage production from ISA Warren compared with Dekalb White. Sausages prepared from meat of ISA Warren hens contained less fat than those from Dekalb White, but showed the same cooking loss. Although the collagen proportion of the sausages produced from ISA Warren was lower than from Dekalb White, collagen solubility was lower and shear energy was higher. During the 10 months of frozen storage, TBARS increased continuously, but not to an extent that would prevent its use as food. The sausages from the ISA Warren genotype had marginally higher TBARS levels during storage. Total colony counts decreased with storage time, with slightly lower values found in the non-spiced sausage material from the ISA Warren hens. In conclusion, when intending to use spent hens as food, ISA Warren are clearly superior to Dekalb White in meat and sausage yield. When processing the meat to sausages, the higher shear energy is probably advantageous.

Effect of replacing dietary vitamin E by sage on performance and meatiness of spent hens, and the oxidative stability of sausages produced from their meat.

A total of 3960 hens (half ISA Warren and half Dekalb White) were housed in 18 compartments with 220 hens each. The effect of replacing dietary vitamin E by sage on productivity, meat yield and oxidative stability of sausages was studied. One third of all animals received either a vitamin E deficient diet (negative control) or diets supplemented with 30 mg/kg α-tocopherylacetate (positive control) or 25 g sage leaves/kg. At slaughter, meat yield was assessed and sausages were produced (n = 12 per treatment). The omission of vitamin E did not impair the oxidative stability of the raw sausage material or the spiced sausages in comparison to the positive control. Sage supplementation improved oxidative stability after 7 m of frozen storage, but not after 1, 4 and 10 m. Spice addition during meat processing had an antioxidant effect regardless of dietary treatment. Diet supplementation of any type did not affect laying performance and sausage meat yield. Feeding antioxidants to spent hens seemed to be not as efficient as in growing chickens, while seasoning with spices during sausage production proved to be a feasible way to delay lipid oxidation.

Oxidative stability of the meat of broilers supplemented with rosemary leaves, rosehip fruits, chokeberry pomace, and entire nettle, and effects on performance and meat quality.

Prevention of lipid oxidation needs special attention because a high proportion of fatty acids in broiler meat are unsaturated. A feeding experiment was conducted to evaluate the antioxidant effect of dietary addition of rosemary, chokeberry pomace, rosehip, or nettle in comparison with vitamin E. Male Ross PM3 broilers caged in groups of 6 (4 replicated cages per treatment) were fed a balanced diet supplemented with 25 g/kg of herbal additive, 200 IU of α-tocopheryl acetate/kg, or without supplementation from d 7 to 35. Intake, performance, and with the help of excreta samples, apparent fiber digestibility, ME content, and metabolizability of nitrogen and energy were recorded per cage. Feed was analyzed for total phenols and tocopherols. In each bird (n = 24 per treatment), carcass weight and relative organ weights were recorded, and skin and liver color were assessed. Abdominal fat was analyzed for induction time (h) of lipid oxidation (Rancimat). Breast meat was analyzed for total tocopherol content (mg/kg) and development of TBA reactive substances (TBARS; µg of MDA/kg) over 9 d of storage. Data were subjected to ANOVA considering treatment and, where applicable, storage time. Rosemary supplementation reduced oxidation (TBARS d 9: 201; induction time: 2.48) and elevated tocopherol content (5.72) of the meat compared with control (470, 1.87, and 3.53, respectively). Rosemary-treated birds had a slightly lower carcass weight and a reduced nitrogen and energy metabolizability. Rosehip addition numerically decreased TBARS (319) and enhanced carcass weight (1.71 kg) compared with rosemary-treated birds (1.54 kg). Only a trend in antioxidant activity could be ascribed to chokeberry pomace, although dietary phenolic content was highest. Nettle did not improve oxidative stability (TBARS: 506; induction time: 1.91), although tocopherol content was elevated (6.51). Nettle treatment strongly intensified skin yellowness (b* of 20.6) compared with the control treatment (10.8). Clearly, rosemary is the most suitable dietary antioxidant investigated in this study, yet chokeberry and rosehip also exhibited interesting properties.

Bt176 corn in poultry nutrition: physiological characteristics and fate of recombinant plant DNA in chickens.

A genetically modified Bt176 corn hybrid, which contains an insecticidal protein against the European corn borer, and its conventional, nonmodified counterpart were evaluated in 4 separate trials to verify substantial equivalence in feeding value and animal performance. Thirty-six individually kept laying hens and 3 replicates of 94 broiler chickens each, assigned to 12 cages, were fed 2 different hen and broiler diets containing either 60% conventional or 60% Bt176 corn. The nutrient compositions of the 2 corn hybrids and the 2 corn diets revealed no major differences. Furthermore, metabolism and performance data revealed no significant differences between the birds that received the conventional, nonmodified corn, and those that received the modified corn diets. The detection of the genetic modification, by PCR, in feed obtained from insect-resistant Bt corn, in tissues and products from animals fed Bt corn is described. In all evaluated chicken tissues of muscle, liver, and spleen, the corn-chloroplast ivr gene fragment was amplified. It can be deduced from these findings and from other studies that the transfer of DNA fragments into the body is a normal process that takes place constantly. Nevertheless, no recombinant plant DNA fragments such as recombinant bla or cry1A(b) fragments could be found. Bt-gene specific constructs from the Bt corn were not detected in any of the poultry samples, neither in organs, meat, nor eggs.

Effect of dietary energy supply and fat source on the fatty acid pattern of adipose and lean tissues and lipogenesis in the pig.

Forty Large White barrows were used to determine whether the effects of dietary fat source (tallow or soy oil at 5% of the diet) on lipogenesis and fatty acid profile of porcine adipose and lean tissue were dependent on dietary digestible energy density (8.8 vs 14.0 MJ DE/kg). Barrows were allocated to one of four groups and offered a fixed amount of feed (170 g x BW0.569/d) from 27 to 105 kg BW. The fatty acid composition of the backfat layers (BF), omental fat (OF), and i.m. adipose tissue of longissimus muscle as well as the activity of lipogenic enzymes of the adipose tissues were determined. Growth performance and carcass characteristics were affected by the dietary energy level (P < 0.01) but not by fat source. In accordance with the lower carcass fat deposition, the activity of lipogenic enzymes were decreased in the low-energy groups (P < 0.01). Within dietary energy level, inclusion of soy oil resulted in increased proportion of PUFA that was compensated by decreased saturated (SFA) and monounsaturated fatty acid (MUFA) proportions (P < 0.01). The SFA changes accounted for 23 (BF) and 24% (OF) of the PUFA changes in the high-energy and 31 (BF) and 39% (OF) in the low-energy diets. The differences in the fatty acid proportions between the soy oil and tallow group were more pronounced in the low-energy groups (fat source x energy density interactions: P < 0.01). Pigs fed the soy oil, low-energy diet had decreased SFA (BF: 28%; OF: 30%) and MUFA (BF: 13%; OF: 19%) concentration, whereas PUFA concentration was increased (BF: 59%; OF: 88%) compared with pigs fed the soy oil, high-energy diet. However, in the tallow groups, pigs fed the low-energy diets had slightly decreased SFA (BF: 14%; OF: 12%) and relatively constant MUFA (BF: 3%; OF: 1%), whereas PUFA concentration increased (BF: 39%; OF: 62%) relative to pigs fed the tallow high-energy diet. Lipid content of the i.m. adipose tissue was decreased in the low-energy groups (P < 0.05). Contrary to what was observed in the adipose tissues, increased PUFA concentration in the neutral and polar lipid fractions of the longissimus muscle was predominantly compensated by reduced MUFA deposition. In the polar lipid fraction, the proportions of both SFA and MUFA were decreased by the low-energy diet. Thus, the extent to which tissue concentration of fatty acids are altered from dietary fats differing in the degree of unsaturation depends on the dietary energy level.

Activity of supplemental enzymes and their effect on nutrient utilization and growth performance of growing chickens as affected by pelleting temperature.

Activity of supplemental enzymes in a barley-soybean-maize based diet at 60, 75 and 90 degrees C pelleting temperatures was studied using feed viscosity, in-vitro enzyme activity and broiler performance data. High pelleting temperatures increased feed viscosity but supplemented enzymes reduced the viscosity at all three temperatures levels by 11, 14 and 17%, respectively. Water intake and losses in excreta of birds were found to be affected by feed viscosity. Activity of cellulase enzyme, measured using the radial diffusion method, was unaffected at 60 and 75 degrees C, but reduced by 73% in feed processed at 90 degrees C. Enzymes increased the weight gain of broilers by 11.1% at 90 degrees C, but no effect could be seen at low pelleting temperatures possibly due to high dietary protein and energy contents. Feed intake was unaffected by enzymes. Birds consumed 6% more feed and grew 9% faster when the pelleting temperature was increased from 60 to 75 degrees C. Reduced feed intake and daily weight gain observed at 90 degrees C could be fully compensated by the enzyme supplementation. High pelleting temperature reduced energy metabolizability (3.2%) and nitrogen utilization (4%) but enzyme almost compensated them (by 3.3% and 2.6%, respectively). No interaction could be detected between the pelleting temperatures and enzymes. It is concluded that pelleting temperatures as high as 90 degrees C drastically reduce cellulase activity, energy and nitrogen utilization thus lowering broiler performance. Either the remaining activity of cellulase or other thermostable enzymes can prevent the losses.