Biomedical subjects

M J Zuidhof

Publications and source records attributed to M J Zuidhof.

9 recordsLinked to original sources

PubMed2005

Mathematical characterization of broiler carcass yield dynamics.

Modeling of broiler chicken supply-chain economics depends on robust biological models of growth and yield of broiler chickens. In this paper, 8 dynamic nonlinear broiler carcass and carcass part yield models were evaluated statistically for their suitability for predicting weights of carcass parts. The analysis employed 4 sigmoidal (S) models (Gompertz, modified Gompertz, Richards, and Lopez) describing carcass part weight as a function of age, as well as 3 diminishing returns (DR) models (Lopez, Mitscherlich, and log linear), and a log-linear proportional yield (PY) model, which describe carcass part yield and weight, respectively, as a proportion of feather- and fat-free empty body mass (FFEBM). Three S models with a flexible point of inflection were better able to predict carcass part weights than a fixed point of inflection Gompertz model and, in general, the DR models. The log-linear models were the only models that converged in 100% of the evaluations. The allometric PY model predicted weights for most carcass parts with the smallest degree of error and with substantially less bias than the DR log-linear model. Estimates of the coefficients for the log-linear PY model are included for 12 key carcass parts. Estimates of carcass chemical composition are presented for the log-linear PY model.

Animals↗

PubMed2004

Performance characteristics and economic comparison of broiler chickens fed wheat- and triticale-based diets.

The effects of triticale and wheat on broiler (mixed sexes) performance and cost of production were compared. In experiment 1, wheat- and triticale-based diets were fed to 3 strains of broilers (Ross x Ross, Hubbard x Hubbard, and Ross x Hubbard). Each of the diets was provided to 5 cages/strain (n = 10 chicks/cage; 1,273 cm2/bird). Weekly BW, gain, feed consumption, and feed conversion ratio (FCR; g of feed/g of gain) were determined. At 42 d, 4 chicks/pen were shipped to a commercial processing plant. The plucked, eviscerated carcasses were evaluated for carcass traits. Overall, the triticale-fed birds had lower final BW and average daily gain and higher FCR. Eviscerated carcass, thigh, and drum weights were lower, but pectoralis minor as a percentage of carcass weight was greater in triticale-fed birds. In experiment 2, a wheat diet and a diet in which triticale was substituted (by weight) for wheat were provided in a 3-phase feeding program. Each diet was provided to 2 identically-equipped commercial barns housing 17,034 broilers each. Individual BW of a sample of birds were recorded in each barn at 0, 19, 34, and 42 d, corresponding to the beginning and end of each dietary phase. Feed consumption and FCR were calculated for each barn. An analysis of each of the diets was calculated using a broiler chicken production cost model. Final BW, feed consumption, carcass weight at processing, flock uniformity, percentage of Grade A carcasses, and percentage of condemned carcasses were not affected by cereal source. Overall FCR (2.165, 2.036; P = 0.0052), feed cost (dollars 0.617, dollars 0.577/kg live weight; P = 0.0260), and total cost of production (dollars 1.019, dollars 0.972/kg live weight; P = 0.0183) were greater for the triticale than wheat diets, respectively. Triticale would be an economically feasible replacement for wheat in broiler diets when its price is less than or equal to 95% of the cost of wheat, less dollars 18 (Canadian). Increased knowledge of the available nutrient profile of triticale, as well as least-cost feed formulation would likely increase the value of triticale relative to wheat for broilers.

Animal Nutritional Physiological Phenomena↗

PubMed2004

Estimation of growth parameters using a nonlinear mixed Gompertz model.

In order to maximize the utility of simulation models for decision making, accurate estimation of growth parameters and associated variances is crucial. A mixed Gompertz growth model was used to account for between-bird variation and heterogeneous variance. The mixed model had several advantages over the fixed effects model. The mixed model partitioned BW variation into between- and within-bird variation, and the covariance structure assumed with the random effect accounted for part of the BW correlation across ages in the same individual. The amount of residual variance decreased by over 55% with the mixed model. The mixed model reduced estimation biases that resulted from selective sampling. For analysis of longitudinal growth data, the mixed effects growth model is recommended.

Aging↗

PubMed2004

Effects of nutrient density on growth and carcass traits in fast- and slow-feathering female turkeys.

Chickens have been sexed based on feather development at hatching for many years, but the slow-feathering gene has only recently been incorporated into a commercial line of turkeys. Female turkeys of a fast- and a slow-feathering strain were compared with regard to BW, gain, and carcass composition to 29 wk of age. A total of 432 fast-feathering (FF) and 432 slow-feathering (SF) poults were reared to 198 d on a control (CON) or a high-energy, high-protein (HIGH) diet. Data concerning BW and carcass characteristics (thoracic circumference and width, shank, keel, breast muscle, fat pad, and liver), feather scores, and breast muscle morphology were assessed over the course of the trial. Strain did not affect BW of the CON-fed birds until after 112 d, when FF birds were 3.1% heavier than SF birds. From 11 to 112 d, feeding the HIGH diet increased BW of SF birds significantly compared with birds fed the CON diet. From 170 to 198 d, FF birds were approximately 0.8 kg heavier than SF birds. At 42 and 84 d in FF birds, and at 84 d in SF birds, increased diet density increased measures of frame size and decreased liver weight. Breast muscle weight, area, and thickness were greater in SF than in FF birds at 42 and 84 d. Increased nutrient density increased feather score in SF birds at 32 (9.8%) and 56 d (7.1%).

Animal Feed↗

PubMed2002

The effects of age at photostimulation and dietary protein intake on reproductive efficiency in three strains of broiler breeders varying in breast yield.

The effects of strain, age at photostimulation, and dietary CP intake during the early lay period on sexual maturation and egg production parameters in broiler breeder hens were determined. Three Arbor Acres strains, Classic, Feather Sexable Yield (FSY), and an experimental line (EXP), were reared in floor pens. At 19 wk of age, pullets were moved into individual cages. At 20 wk of age one-half of the birds were photostimulated by increasing the day length from 8L:16D to 15L:9D. The remaining birds were photostimulated at 23 wk of age. The birds were fed 16 or 18% CP diets from 19 to 32 wk of age. The Classic hens achieved sexual maturity 4 d before the EXP hens. Delaying photostimulation to 23 wk of age delayed sexual maturity but the rate of sexual maturation was accelerated after photostimulation occurred. Egg weight at sexual maturity was higher for the later photostimulated birds. The FSY and EXP hens, selected for more white-meat yield than the Classic hens, were heavier in BW but had lower settable egg production than the latter. Feeding 18% CP resulted in a higher BW throughout the trial, as compared to the 16% CP diet. There was a response to dietary CP and photostimulation age on initial egg weight and the number of double-yolked eggs. Early photostimulation was not advantageous because egg production parameters were not affected. Both Classic and FSY strains performed well when fed 18% CP; however, EXP hens benefited from 16% CP intake.

Age Factors↗

PubMed2002

Responses of two strains of female broiler breeders to a midcycle increase in photoperiod.

The influences of strain and a midcycle increase in photoperiod on the reproductive performance of broiler breeder hens were evaluated. At 22 wk of age, Strain X and Y pullets were randomly assigned to one of five groups [processed at 22 wk of age (A), processed after third oviposition (B), processed at 32 wk of age (C-32), processed at 40 wk of age (C40), and processed at 54 wk of age (C-54)] and were placed into individual laying cages. These groups were euthanized at different ages to analyze reproductive and carcass parameters. Photostimulation occurred at 22 wk of age when the photoperiod was increased from 8L:16D to 14L:10D. A light-tight wall partitioned the room into two halves. At 33 wk of age, half of the birds received an increase in photoperiod to 18L:6D, whereas the other half remained at 14L:10D. Body weight and abdominal fat pad weight increased with age. The number of large yellow follicles (LYF) decreased from 8.78 at sexual maturity to 4.60 at 54 wk of age. The number of atretic white follicles (WF) and small yellow follicles (SYF) also increased with age. Although there were no differences in BW, Strain Y had a greater egg weight throughout the laying cycle than Strain X. Peak hen-day egg production was 93.0%, and, overall, egg production was not affected by strain. Reproductive performance and ovarian morphology were not affected by the increase in photoperiod, presumably because peak egg production was so high. Carcass data demonstrated that frame size was determined by sexual maturity, whereas organ weights changed in response to reproductive status.

Animal Husbandry↗

PubMed2001

Carcass traits, ovarian morphology and egg laying characteristics in early versus late maturing strains of commercial egg-type hens.

Three hundred commercial Single Comb While Leghorn (SCWL) pullets of two strains differing in age at first oviposition (early maturing = EARLY; later maturing = LATE) were reared and photostimulated at 18 wk. Selected birds of each strain were killed at weekly intervals from 17 to 23 wk, at sexual maturity, or at 68 wk of age for the study of carcass and reproductive organ traits. Egg production was recorded for surviving hens to 68 wk of age. The two strains differed in age at sexual maturity (EARLY, 137.5 d; LATE, 142.1 d). The EARLY strain birds appeared to allocate a greater proportion of nutrients to reproductive development (oviduct) from 19 to 22 wk of age than did the LATE group, which showed greater breast muscle development during this same period. The LATE strain hens were significantly heavier than the EARLY hens at sexual maturity, and this difference in BW persisted to the end of the laying period. Although total egg production did not differ between strains, the LATE strain hens had a longer prime egg-laying sequence length (LATE, 70.2 d; EARLY, 52.6 d) as well as a longer mean sequence length (LATE, 12.8 d; EARLY, 8.7 d). Egg weight did not differ between strains. These data suggest that LATE lines of egg-type hens offer equivalent production efficiency due to improved rates of lay, albeit starting later.

Animal Husbandry↗

PubMed2000

The effects of body weight and long ahemeral days on early production parameters and morphological characteristics of broiler breeder hens.

Shaver Starbro broiler breeder pullets were used to study the effect of day length (24 and 28 h) on egg production parameters and egg traits from 22 to 30 wk of age, and ovarian and morphological characteristics at 30 wk of age. Floor-housed pullets were raised in a light-tight facility from 1 d of age until housing in individually illuminated cages at time of photostimulation (22 wk). Cages were equipped with hardware to monitor egg laying time. The photoschedule during rearing was 24 h light: 0 h dark for the first 3 d followed by 8 h light: 16 h dark from 3 d to photostimulation. Body weight was monitored throughout the trial to maintain weights at targets set by Shaver Poultry Breeding Farms, Ltd. The experimental design was a 2 x 2 factorial with two day lengths [hemeral (24 h) and ahemeral (28 h)] and two BW groups [high (HBW) and low BW (LBW)], with the LBW weighing 327 g less than the HBW birds at 22 wk of age. The hemeral photoschedule was 14 h light: 10 h dark, and the ahemeral photoschedule was 14 h light: 14 h dark. Differences in BW remained throughout the trial. Egg numbers were not increased by the 28-h day (24 h = 25.4 eggs; 28 h = 23.1 eggs). The 24-h hens laid more double-yolked eggs (0.9% of total egg production) than did the 28-h birds (0.3%). Egg formation time was consistently longer for the 28-h hens (26.8 h at 25 wk of age and 25.8 h at 29 wk of age) compared with the 24-h hens (25.4 h at 25 wk of age and 24.8 h at 29 wk of age). Mean egg weight was higher for the 28-h birds (55.1 g) compared with the 24-h birds (53.0 g). Egg specific gravity was higher in eggs from the 28-h hens than eggs from the 24-h hens. Some of the increase in egg weight between the 28- and 24-h birds was due to shell weight. Absolute and proportional weights of the egg shell were 5.5 g and 10.0% of the total egg weight for the 28-h birds and 4.9 g and 9.3% for the 24-h birds, respectively. The 28-h hens had higher proportional breast muscle weight, smaller livers and oviducts, and lower ovary weight compared with the 24-h birds. The data indicated that, although egg size can be increased with the use of long ahemeral days early in lay, this result may be at the expense of egg numbers. Early in lay, follicular maturation rates are fast, and egg production may be limited to one ovulation per 28 h.

Animals↗

PubMed1995

The effects of nutrient dilution on the well-being and performance of female broiler breeders.

A study was conducted to determine the effect of nutrient dilution on plasma heterophil:lymphocyte ratios, behavior, and productivity of broiler breeder hens. Standard age-appropriate broiler breeder diets were fed either undiluted or diluted with 15 and 30% ground oat hulls from 0 to 56 wk of age. Feed was allocated daily so as to achieve the BW recommended by the breeder. Pullets were photostimulated at 20 wk, at which time 80 per treatment were moved, 2 per cage, to 120 laying cages, where they were housed until 56 wk of age. The same dilution treatment was continued for the laying period. The time required to consume the diluted feed was higher when diets were diluted during both the rearing (P = .002) and the laying periods (P = .0001). Heterophil:lymphocyte ratios at 12 wk of age indicated that hens subjected to higher levels of quantitative feed restriction experienced more long-term stress (P < .05). This difference was not evident at 20 wk or at 50 wk. During the laying period, hens that were fed diluted diets spent less time at the water source than those fed standard diets (P = .0001). The rate of decrease in flock uniformity during lay was slower in hens fed the diluted diets (P < .05). Hens fed the diet diluted by 15% had the highest egg production (P = .012), chick production (P < .0001), the best CP conversion efficiency (P < .05), and better feed conversion efficiency (P < .05). Diet dilution with ground oat hulls seems to be a means of reducing stress and improving efficiency and productivity in broiler breeder flocks.

Animals↗