Response of Ross 308 and Hubbard broiler chickens to feed removal for different durations during the day.

The effects of feed removal for 6, 8, or 10 h during the day from 8 to 28 days of age followed by ad libitum feeding to market age on the growth performance of two strains of broiler chickens, Ross 308 and Hubbard, were studied over 7 weeks. Ross 308 was superior to Hubbard in weight gain and final body weight but consumed more feed and deposited more abdominal fat. Overall, daily feed removal reduced feed intake and improved feed efficiency in all feed-restricted birds, and the longer the period of feed removal the better the efficiency of utilization, but it had no significant effect on weight gain and market weight. It is suggested that for broiler production in the tropics, Ross 308 could be used on a 10-h daily feed removal program from 8 to 28 days of age.

The response of Ross 308 and Hybro broiler chickens to early and late skip-a-day feed restriction.

The effects of skip-a-day feeding for 14 days during the starter or grower period or for 28 days during both periods followed by ad libitum feeding to market age on the growth performance of two strains of broiler chickens, Ross 308 and Hybro, were studied over 7 weeks. Ross was superior to Hybro in weight gain, final body weight and feed conversion but consumed more feed. Overall, feed restriction reduced feed intake, weight gain and body weight in all feed - restricted birds. Also, the 14-day feed-restricted birds gained more weight and were heavier than the 28-day restricted ones. Feed restriction neither improved feed conversion nor reduced abdominal fat but decreased mortality rate. Strain | treatment interaction significantly affected only feed intake. It is suggested that for broiler chicken production in the tropics Ross 308 could be used and feed restricted for 14 days during the starter or grower period.

Growth performance and carcass characteristics of feedlot cattle fed different levels of macadamia oil cake.

Eighteen cattle (six Bonsmara males, seven Simmanteler x Beefmaster males and five Simmanteler x Beefmaster females) were assigned to three diets containing 0% (Control), 10% and 20% Macadamia oil cake to evaluate the effects of different levels of Macadamia oilcake (MOC) on feed intake, growth performance and carcass characteristics of feedlot cattle. Differences in average feed intake were not significant (P > 0.05). Average daily gains on the 0% and 20% MOC diets were not significantly different (P < 0.05) but were significantly higher than the average gain on 10% MOC (P < 0.05). The inclusion of 20% MOC increased feed conversion ratio significantly (P < 0.05) compared with the other two treatments. The control group had significantly heavier warm carcasses than the 10% and 20% MOC groups and the 20% MOC group had significantly heavier carcasses than the 10% MOC group. The inclusion of MOC did not significantly affect the dressing percentage and conformation scores of the animals (P > 0.05). There were no condemned livers, suggesting that either there were no toxic factors in the feed or, even if present, were probably inactive in the liver.

The influence of stocking density on body weight, egg weight, and feed intake of adult broiler breeder hens.

The influence of stocking density on BW, egg weight (EW), and feed intake (FI) in Ross broiler breeder hens (n = 120) was investigated during the late medium egg production period (from 50 to 54 wk of age). Birds were randomly allocated to 6 pens in densities of 15, 20, and 25 birds/pen, giving rise to a floor space allowance of 5, 6.67, and 8.33 birds/m(2), respectively. Each density was replicated twice, and the order among the 6 pens was chosen at random. Data were analyzed using the repeated measures techniques of the Statistical Analysis System, considering the covariance structure of the observed data. There was a significant effect attributable to stocking density, time (in days), and their interaction for BW, EW, and FI. Birds in density of 6.67 per m(2) were lighter but had heavier eggs than birds in density of 5 per m(2); however, birds in density of 8.33 per m(2) had similar BW and EW with birds in the other 2 groups. The mean FI were statistically different among the 3 groups, with a reduction in FI as density increases. Total egg production within the 3 density groups and average egg production per bird were also analyzed using categorical data techniques. The results indicated that stocking density influenced egg production, with birds at higher density producing fewer eggs per bird. Although generous floor space allowances were allocated per bird in this experiment, stocking density influenced the performance of broiler breeder hens.

Effects of genetic and environmental factors on pre-weaning and post-weaning growth in West African crossbred sheep.

Effects of genetic and environmental factors on pre-weaning and post-weaning growth were studied in West African crossbred sheep. Effects of lamb genotype (7/8 Sahelian-1/8 Djallonké, 3/4 Sahelian-1/4 Djallonké and 1/2 Sahelian-1/2 Djallonké; hereafter denoted 7/8Sa, 3/4Sa and 1/2Sa, respectively), parity, type of birth, sex of lamb and year-season of lambing on birth weight, weaning weight, 8-month weight and pre- and post-weaning growth rates were determined. At birth 7/8Sa and 3/4Sa lambs were heavier (p < 0.01) than 1/2Sa lambs. Lambs born to first-parity ewes were lighter (p < 0.01) at birth than lambs of older ewes. At weaning and 8 months of age, lambs born to fourth-parity ewes were heavier (p < 0.05) than those born to ewes of the other parities. Parity did not have any significant effects on pre-weaning growth rate. Lambs born in the rainy season of 2001 were significantly heavier at birth and at 8 months of age than those born in the dry season of 2001/02, but there was no difference between the two groups at weaning. Pre-weaning growth rate was significantly faster in lambs born in the dry season of 2001/02 but the reverse was true for post-weaning growth rate.

Effects of stocking density and group size on the performance of white and brown Hyline layers in semi-arid conditions.

The effect of housing two Hyline strains of commercial laying hens White Hyline (W-98) and Brown Hyline (Hyline Brown) at densities of 2, 3 or 4 per cage (1100, 733 or 550 cm2/hen, respectively) was investigated over 3 months. Hyline Brown layers gained more weight, laid more but lighter eggs, utilized feed more efficiently and had a lower mortality than W-98 layers. Housing birds 2 or 3 per cage resulted in greater body weight gain, higher egg production, heavier eggs, better feed conversion ratio and a lower mortality than housing them 4 per cage. There were significant interactions between strain and stocking density for egg production, egg weight, egg output and mortality. It is suggested that for egg production in semi-arid areas Hyline Brown hens could be used and housed at a density of 733 cm2/hen.

Estimation of genetic parameters and variance components for growth traits of Nguni cattle in Limpopo Province, South Africa.

Estimates of (co)variance and genetic parameters of birth, weaning (205 days) and yearling (365 days) weight were obtained using single-trait animal models. The data were analysed by restricted maximum likelihood, fitting an animal model that included direct and maternal genetic and permanent environmental effects. The data included records collected between 1976 and 2001. The pedigree information extended as far back as early 1960s. The heritabilities for direct effects of birth, weaning and yearling weights were 0.36, 0.29 and 0.25, respectively. Heritability estimates for maternal effects were 0.13, 0.16 and 0.15 for birth, weaning and yearling weights, respectively. The correlations between direct and maternal additive genetic effects were negative for all traits analysed. The results indicate that both direct and maternal effects should be included in a selection programme for all the traits analysed.

Relationships between longevity and linear type traits in Holstein cattle population of Southern Africa.

Relationships between longevity and linear type traits were estimated using data on 34,201 cows with lifetime information and linear type scores. The longevity trait considered was the number of lactations initiated and the linear type traits were rump height, body depth, angularity, rear udder height, fore udder attachment, udder depth, fore teat placement and fore teat length. Fixed effects included in the models were herd year, season of calving and herd-date of classification-classifier and days in milk. Age at first calving and age at classification were included as linear and quadratic covariates. Heritability estimates were low for longevity and moderate for most type traits except rump height and fore teat length. All the phenotypic correlations between longevity and the linear type traits were slightly positive (0.01 to 0.09) except the relationships with rump height and fore teat length which were -0.01 and -0.02, respectively. Genetic correlations between longevity and udder traits as well as angularity were moderate to high and positive (0.22 to 0.48). The only notable negative genetic correlations were longevity with body depth and fore teat length (-0.15 and -0.07, respectively). The genetic correlations suggest that selection for udder traits and angularity should improve longevity in the Holstein cattle population.

Effects of food restriction during the finishing period on the performance of broiler chickens.

1. Three hundred 4-week-old commercial Hibrow broiler chicks were fed ad libitum, 85% and 70% of ad libitum or ad libitum for 5 d per week with 3rd and 5th days of food withdrawal for 28 d to examine the effects of food restriction on liveweight, growth rate, food conversion efficiency, dressing percentage, abdominal fat and mortality. 2. Quantitative food reduction to 85% and 70% of ad libitum, and reduction in feeding time by 2 d/week significantly reduced final body weight and rate of growth. 3. Food restriction (to 70% ad libitum) resulted in lower abdominal fat than ad libitum feeding, 15% food restriction or reduction in feeding time by 2 d/week. 4. There were no significant differences between the effects of 15% food restriction and 2-d reduction in feeding time per week on final body weight, growth rate and abdominal fat. 5. Reduction in feeding time by 2 d/week resulted in the same food efficiency as ad libitum feeding and quantitative food restriction by 15% and a significantly better food efficiency than 30% quantitative food reduction. 6. Reducing feeding time by 2 d/week seemed to have less severe effects on the birds than quantitatively reducing food supply by 30%.

Estimation of liveweight from chest girth in pure and crossbred west African goats.

Linear and geometric regression equations were used to estimate liveweight from chest girth in 78 West African Dwarf and 73 Sahel x West African Dwarf goats. The coefficients of determination (R2) ranged from 0.87 to 0.92 and 0.97 to 0.99 for linear and geometric equations respectively. There were no significant breed or sex differences in the R2 values of the equations. The geometric equations estimated liveweight with a high degree of reliability regardless of girth size whilst the linear equations yielded very low and frequently negative liveweight estimates where girth measurements were below 30 centimetres.

Genotype-environment interaction effects on reproductive performance in Tribolium castaneum.

Three lines of Tribolium castaneum were raised totally on a yeast-free or yeast-supplemented diet, or raised to pupation on a yeast-free diet and then on a yeast-supplemented diet, and vice versa, to study the effects of genotype x environment interaction and diet changes after pupation on reproduction.Feeding the yeast-supplemented diet generally resulted in earlier sexual maturation, heavier adult weights and higher egg production. The diets had no effects on larval viability. Changes in diet after pupation had no effects on age at sexual maturity or adult weight. Egg production was determined largely by the environment just prior to and during egg laying. However, egg production on the yeast-free diet was influenced by the pre-pupation diet.There was significant line x environment interaction effects on age at sexual maturity, mature egg production and adult weight (P<0.01). There was also a sire x environment effect on egg production (P<0.05).