D. V. Thomas

Influence of stocking density on the performance, carcass characteristics and selected welfare indicators of broiler chickens

Abstract AIM: To compare the effects of four stocking densities (5, 10, 15 or 20 birds per m2) on the performance, carcass characteristics and selected welfare indicators of broiler chickens. METHODS: A total of 756 day-old male broiler chicks were assigned as six replicates of 13, 25, 38 and 50 birds per pen, to stocking densities of 2,000, 1,000, 667 and 500 cm2 floor space per bird, respectively. The birds were housed in floor pens in an environmentally controlled room. Normal commercial diets were fed ad libitum and fresh water was freely available throughout the 5-week study period. Liveweights of birds and feed intake were recorded at weekly intervals. Data on carcass parameters and welfare indicators (moisture, gait scores, feather scores, breast and hip lesions, and foot pad and hock burns) were obtained on Day 35. Adrenal glands were removed at slaughter, weighed and examined histologically to determine the total proportion of cortical and medullary tissues. RESULTS: During the study, the birds at the lowest density grew faster (p<0.001−0.01) and consumed more (p<0.001− 0.01) feed than those at the other three stocking densities. The liveweight gains and feed intake of birds reared at densities of 10, 15 and 20 birds per m2 were similar (p=0.11−0.83 and p=0.17−0.57, respectively). Stocking density had no influence on the feed/weight gain, mortality or carcass characteristics. No breast or hip lesions were observed in carcasses from any of the groups. The weight and structure of the adrenal glands were similar across all groups although the staining of medullary tissue of birds was most intense in the highest stocking density group. As stocking density increased, so did moisture and gait score, hock and foot pad burn scores, and the feather score was adversely affected. CONCLUSIONS: The data showed that the relationship between stocking density and productivity traits was not linear in nature, in accordance with other studies. Under the conditions of the current study, the performance, mortality and carcass characteristics of broilers grown at densities of 10, 15 and 20 birds per m2 were similar. There were some welfare implications at high population densities as indicated by adverse effects on litter quality, gait scores and the incidence of hock and foot pad burns.

Endogenous flow of amino acids in the avian ileum as influenced by increasing dietary peptide concentrations

The aim of the present study was to establish whether feeding broiler chickens with diets containing increasing dietary peptide concentrations would cause increases in ileal endogenous amino acid flow. The flow of N and most amino acids increased quadratically (P < 0.05 to 0.001) with increasing dietary concentrations of peptides. The exceptions were the flow of threonine, serine, glycine, tyrosine and cystine, which increased linearly (P < 0.001) with dietary peptide levels. Another notable exception to the general trend was the flow of proline, which was significantly higher (P < 0.01) in birds fed the protein-free diet. The amino acid profile of endogenous protein, expressed as proportion of crude protein, indicated that the ratios of threonine, glutamic acid, proline, glycine, leucine, histidine, arginine and cystine were influenced (P < 0.05) with increasing dietary peptide concentrations. In general, compared with the protein-free diet, the ratios of threonine and arginine in endogenous protein were lower (P < 0.05) and those of glutamic acid, glycine and histidine were greater (P < 0.05) in diets with high concentrations of peptides. The ratio of proline was found to decrease (P < 0.05) with increasing dietary peptide concentrations. These changes in the amino acid profile of endogenous protein are probably reflective of changes in the output of one or more of the components of endogenous protein. Overall, the present results demonstrated that increasing dietary peptide concentrations increased the flow of endogenous amino acid flow at the terminal ileum of broiler chickens in a dose-dependent manner and also caused changes in the composition of endogenous protein. The observed changes in endogenous amino flow will influence the maintenance requirements for amino acids and also have implications for the calculation of true digestibility coefficient of feedstuffs.

Nutrient digestibility and energy utilisation of diets based on wheat, sorghum or maize by the newly hatched broiler chick

1. Two experiments were conducted to measure changes in nutrient utilisation in the newly hatched broiler chicken. The first experiment determined the nitrogen-corrected apparent metabolisable energy (AMEN) and total tract digestibility of starch and fat in diets based on wheat, sorghum and maize during the first two weeks post-hatch. The second experiment was conducted to confirm the results of Experiment 1 using wheat- and maize-based diets and was of 21 d duration. 2. In both experiments, changes to AMEN with age were similar irrespective of the diet type, declining from d 3 to d 5–9 and then increasing after d 9. 3. In Experiment 1, the total tract digestibility of starch and fat exhibited a pattern similar to that of AMEN. 4. In Experiment 1, cereal effects were significant, with maize- and sorghum-based diets having higher AMEN values than the wheat-based diet. Total tract starch digestibility determined for d 5, 7 and 14 showed no cereal differences. Total tract fat digestibility on d 7 was significantly lower for the wheat- and sorghum-based diets than for the maize-based diet, but no cereal differences were observed on d 5 or 14. 5. In Experiment 2, cereal effects were significant, with the maize-based diet having a higher AMEN than the wheat-based diet. 6. These results showed that nutrient utilisation is compromised during the first week of life of the broiler chick.

Influence of conditioning temperature on the performance, nutrient utilisation and digestive tract development of broilers fed on maize- and wheat-based diets

1. The influence of conditioning temperature on the performance, nutrient utilisation and digestive tract development of broilers fed on maize- and wheat-based diets was examined up to 21 d of age. The experimental design was a 2 × 3 factorial arrangement of treatments evaluating two grain types (maize and wheat) and three conditioning temperatures (60°C, 75°C and 90°C). Broiler starter diets, each based on one grain (maize or wheat), were formulated and pelleted at the three temperatures. 2. Increasing conditioning temperature decreased the body-weight gain and feed intake in wheat-based diets, but birds fed on maize-based diets conditioned at 60°C and 90°C had higher body-weight gain and feed intake than those fed on the diet conditioned at 75°C. Increasing conditioning temperature increased feed per body-weight gain in both grain-type diets but improved pellet durability index (PDI) only in wheat-based diets; PDI was unaffected in maize-based diets. 3. In wheat-based diets, increasing conditioning temperature decreased the ileal digestibility of nitrogen and starch. Ileal nitrogen digestibility of maize-based diets conditioned at 60°C and 90°C was higher than at 75°C. Starch digestibility was unaffected by conditioning temperature in maize-based diets. No effect of conditioning temperature was found for apparent metabolisable energy (AME). Increasing conditioning temperature decreased digestible protein and AME intakes in wheat-based diets but, in maize-based diets, birds fed on the diet conditioned at 75°C had lower digestible protein and AME intakes compared to those fed on diets conditioned at 60°C and 90°C. 4. Small intestine was longer in birds fed on diets conditioned at 75°C and 90°C compared with those fed on diets conditioned at 60°C. 5. Overall, the data suggest that while the effects of conditioning temperature on body-weight gain and feed intake of broilers to 21 d of age differed depending on the grain type, feed per body-weight gain was adversely affected by higher conditioning temperatures.

Effect of two microbial phytases on mineral availability and retention and bone mineral density in low-phosphorus diets for broilers

1. The efficacy of supplementation of a low-phosphorus (low-P) maize–soyabean meal diet for broiler chickens with two different microbial (fungal and bacterial) phytases was examined. 2. Broiler chickens received a low-P maize–soyabean meal diet containing either no phytase or one of the two phytases included at one and two times the manufacturers recommended inclusion level for 21 d. 3. Titanium dioxide was included in the diets as an indigestible marker. Excreta were collected quantitatively from d 18 to 21, and at the end of the study the birds were killed and ileal digesta and leg bone samples collected. 4. No differences were observed for body weight gain and feed intake or apparent metabolisable energy (AME) among all dietary treatment groups. 5. Dietary phytase supplementation improved the apparent retention of Ca, Na and Cu and ileal phytate P absorption from 32% to 44% across inclusion levels. 6. Bone mineral density (BMD) was improved for both phytases across inclusion levels by, on average, 9% for the tibia and 13% for the femur. 7. Dietary phytase supplementation of the low-P diet improved apparent ileal digestibility of serine, glycine, valine, isoleucine, tyrosine, histidine, lysine and arginine. 8. When the results from the present study were combined with the results from other similar published studies and analysed statistically, factors such as dietary P and Ca concentration, as well as bird breed and age, rather than the type or activity of microbial phytase, had the greatest impact on the extent to which dietary supplementation improved P and Ca retention. 9. More work is required to explain the interrelationships between the multiple factors influencing the efficacy of phytase on the availability of dietary minerals.

The effect of manipulation of pellet size (diameter and length) on pellet quality and performance, apparent metabolisable energy and ileal nutrient digestibility in broilers fed maize-based diets

A 2 by 2 factorial arrangement of treatments was used to evaluate the effect of pellet diameter (3 and 4.76 mm) and pellet length (3 and 6 mm) on pellet quality and performance, apparent metabolisable energy and ileal digestibility of nitrogen and starch in broilers. From 0 to 9 days of age, all birds were offered a common starter diet. Broiler grower (Days 10–21) and finisher (Days 22–42) diets, based on maize, were formulated and then allocated to the four different treatments. All diets were steam-conditioned at 60°C before pelleting. In grower diets, increasing pellet diameter and pellet length reduced (P 0.05) by main effects or the interaction. In grower and finisher diets, increments in pellet durability index and pellet hardness with increasing pellet length were greater in pellets with a 3-mm diameter than those with a 4.76-mm diameter. During the grower period (Days 10–21), birds fed the 3-mm-diameter pellets had lower (P 0.05) for weight gain, feed intake and feed per gain. Increasing pellet diameter from 3 to 4.76 mm decreased (P 0.05) for the coefficient of ileal apparent digestibility of nitrogen. Increasing pellet length from 3 to 6 mm decreased (P 0.05). Overall, when low conditioning temperatures are used to optimise nutrient availability, small diameter die holes and longer pellet lengths can favour creating high physical quality pellets. The present study also showed that feeding lower diameter pellets to broilers during the grower period (Days 10–21) only improved feed per gain, a response which disappeared as the birds grew older.

An exploratory analysis of the suitability of diets fed to a flightless insectivore, the North Island brown kiwi (Apteryx mantelli), in New Zealand

The ingredients and the macro- and micro-nutrient contents of diets that are fed to captive kiwi at seven New Zealand holding facilities were subject to analysis. The nutrient compositions were compared across facilities and with an estimate of the nutrient composition of the diets of wild kiwi based on the intake of various dietary ingredients reported in the literature. A total of 20 ingredients were used, the number and proportion of these ingredients varied greatly between facilities. Six of the diets were based primarily on meat and three comprised a mixture of meat and cat biscuits. Just one included a proprietary insectivore mix. Nutrient content varied greatly between the seven diets, organic matter ranging from 91.8 to 95.6%, crude protein from 41.9 to 62.9%, and crude fat from 9.0 to 28.7% of dry matter content. Large variations were found in the total content and profile of amino acids and of fatty acids of the diets. The nutrient content of all seven diets differed from that of the natural diet of wild kiwi. Hence, the presence of nutrient deficiencies in the current formulations cannot be excluded.

Influence of pellet diameter and length on the quality of pellets and performance, nutrient utilisation and digestive tract development of broilers fed on wheat-based diets

1. The influence of pellet diameter and length on the quality of pellets and performance, nutrient utilisation and digestive tract development of broilers given wheat-based diets was examined from 10 to 42 d of age. The experimental design was a 2 × 2 factorial arrangement of treatments evaluating two pellet diameters (3 and 4.76 mm) and two pellet lengths (3 and 6 mm). From 0 to 9 d of age, all birds were offered a common starter diet pelleted with a 3-mm diameter die and 3-mm length. Broiler grower (d 10 to 21) and finisher (d 22 to 42) diets, based on wheat, were formulated and then subjected to the 4 different treatments. 2. In grower diets, increasing pellet diameter and pellet length reduced the gelatinised starch (GS) content of the diets. In finisher diets, GS content of 3-mm diameter pellets did not change with increasing pellet length but decreased in 4.76-mm diameter pellets. 3. In grower and finisher diets, increments in intact pellet weight, pellet durability index and pellet hardness with increasing pellet length were greater in 3-mm diameter pellets than those with 4.76-mm diameter. 4. Increasing pellet length from 3 to 6 mm increased apparent metabolisable energy values. Neither the interaction nor main effects were significant for the ileal digestibility of nitrogen and starch. 5. During the grower period (d 10 to 21), birds given pellets of 6-mm length had greater body-weight gain than those given 3-mm length pellets. Feeding 6-mm length pellets decreased feed per body-weight gain compared to 3-mm length pellets. During the finisher (d 22 to 42) and whole grow-out (d 10 to 42) periods, while different pellet lengths had no effect on feed per body-weight gain values at 3-mm pellet diameter, increasing the pellet length decreased feed per body-weight gain at 4.76-mm pellet diameter. 6. Increasing pellet diameter and pellet length reduced the relative length of duodenum. Birds given 3-mm diameter pellets had heavier proventriculus compared to those given 4.76-mm diameter pellets. 7. Overall, the data suggest that increasing the pellet length from 3 to 6 mm improved the body-weight gain and feed per body-weight gain during the grower period (d 10 to 21). While the positive effect on body-weight gain disappeared as the birds grew older, improvements in feed per body-weight gain were maintained over the finisher and whole grow-out periods only in 4.76-mm diameter pellets. Small diameter die holes and longer pellet lengths may be considered as potential manipulations to manufacture high-quality pellets under low conditioning temperatures.

The Effect of Stocking Density on the Behaviour of Broiler Chickens

A 35-day trial was conducted to examine the influence of floor density on the behaviour of broiler chickens. Day-old male broilers (n=756) were randomly assigned to one of four stocking densities (6 replicates of n=13, 25, 38 and 50) in 24 identical 2.6 ㎡ pens. These stocking densities were coded very low (VL), low (L), medium (M) and high (H) and contained a floor space allowance per bird of 2,000 ㎠, 1,000 ㎠, 667 ㎠ and 500 ㎠, respectively. Scan sampling of all groups was carried out at 15-min intervals during two 1-h periods (10.00 h～11.00 h and 14.00 h～15.00 h) for five days each week. The numbers of birds engaged in different behavioural activities were recorded. It was found that the most common behaviour in all densities was lying. There was no clear effect of density during wks 1～4 of the trial, but in wk 5 birds in the L, M and H groups showed lower levels (P=0.07) of lying behaviour when compared to birds in the VL group suggesting that an increase in animal density results in decreased opportunities for undisturbed rest. This observation is supported by standing and walking behaviour, which was lower (P＜0.05) in the VL group in wk 5. Foraging behaviour measured in the study by the numbers of birds pecking the ground declined as the trial progressed, but scratching increased in 2 wk then decreased. Birds in the VL group showed higher (P＜0.05) level of pecking the ground behaviour compared to birds in the L, M and H groups, but scratching behaviour higher (P＜0.05) and lower (P＜0.05) in VL of 1 wk and 2 wk respectively. However, a peak in aggressive behaviour was observed in wk 2 and birds in the VL group showed less (P＜0.05) agonistic behaviour than birds in the H and M groups. Other behaviours (dustbathing, preening, eating or drinking) were not influenced (P＞0.05) by stocking density.

Effects of spray-dried colostrum and plasmas on the performance and gut morphology of broiler chickens

The influence of feeding with starter diets containing spray-dried bovine colostrum (SBC), spray-dried bovine plasma (SBP), or spray-dried porcine plasma (SPP) on the growth performance and gut morphology of broiler chickens was investigated. The crude protein, lysine, and methionine plus cystine contents (g/kg as received) of SBC, SBP, and SPP were determined to be 766, 736, and 684; 58, 61, and 55; and 27, 28, and 24, respectively. The 3 test proteins were incorporated into a maize-soybean meal diet at a level of 50 g/kg and fed to 6 replicates of 8 male broiler chicks from 1 to 14 days of age. On Day 14, the experimental diets were replaced with a common grower-finisher diet, which was offered until Day 35. Dietary treatments had no effect (P > 0.05) on the weight gain or feed intake of birds during the first 14 days. However, feed/gain of birds fed the SBC diet was lower (P 0.05) on performance during Days 14-35 or Days 1-35. Villus height was increased by 5.7% (P < 0.05) and 4.6% (P = 0.05) in birds fed the SPP and SBP diets, respectively, compared with those fed the control diet. Crypt depth was 6% greater (P < 0.05) in birds fed the SPP diet and tended (P = 0.08) to be greater in birds fed the SBC diet, compared with birds fed the control. The ratio of villus height to crypt depth tended (P = 0.06) to be lower in birds offered the SBC diet compared with the control. Crypt goblet cell density was reduced (P < 0.05) by 13.9% in birds fed the SBC diet, compared with control birds. These results suggest that feeding with diets containing the SBC, SBP, and SPP during 1-14 days of age has some beneficial effects on broiler chickens. Further studies are needed to evaluate these products in less sanitary environments, which may increase the positive responses.