Effects of avilamycin on performance of broiler chickens.

The benefits of feeding avilamycin (Surmax/Maxus, Elanco Animal Health) to broiler chickens were demonstrated in a floor pen study (two trials) in which avilamycin was fed at 10 ppm in a 45-day growout. Final live weight of broilers fed avilamycin was significantly (P < or = .01) heavier (90 g) than that of control broilers fed for an equal number of days. Feed conversion was numerically but not significantly improved by avilamycin. Dressing percentage (hot eviscerated carcass weight/live weight) of broilers fed avilamycin was significantly improved (P < or = .01) relative to that of control broilers fed for an equal number of days.

Comparison of growth factor receptors and metabolic characteristics of satellite cells derived from the biceps femoris and pectoralis major muscles of the turkey.

Myogenic satellite cells were isolated from the turkey pectoralis major (PM), a muscle composed largely of white fibers, and the biceps femoris (BF), a muscle composed largely of red fibers, and their properties were compared in culture. Satellite cells derived from the PM and BF muscles exhibited differences in metabolic parameters, growth factor receptor characteristics, and mitogenic responses. PM satellite cells exhibited greater responsiveness to platelet-derived growth factor (PDGF), and the PDGF receptor on these cells had a higher affinity toward ligand compared to BF cells (P < 0.05). Protein synthesis, protein degradation, and glucose uptake rates were higher in BF satellite cell cultures (P < 0.05), correlating with previously reported in vivo measurements using red and white muscle fibers.

In vitro characteristics of myogenic satellite cells derived from the pectoralis major and biceps femoris muscles of the chicken.

Satellite cells were isolated from the pectoralis major (PM) and biceps femoris (BF) muscles of 5-week-old broiler chickens to compare growth and differentiation characteristics in vitro. BF cells proliferated at greater rates in the growth medium and were more responsive to the mitogenic effects of chicken serum than PM cells at all levels tested (p < or = 0.05). When low serum-containing medium was administered, the levels of creatine kinase, a marker of differentiation, increased at greater rates in PM cultures than in BF cultures (p < or = 0.05). Administration of increasing levels of fibroblast growth factor in serum-free medium resulted in similar responsiveness of the two lines to this mitogen. No differences were detected in rates of protein synthesis or degradation in myotube cultures from the two muscle sources. The results suggest that satellite cells derived from PM and BF muscles of the chicken have different responsiveness to serum mitogens.

Response of layer breeders to dietary acetylsalicylic acid. 2. Effects on circulating concentrations of prostaglandin F2 alpha.

White Leghorn breeder hens were fed 0, .05, or .40% acetylsalicylic acid (ASA) for either 1 wk or 1 mo. Blood samples were collected 4 h postentrance of an egg into the uterus (baseline) and at oviposition of a hardshelled (HS) egg. Plasma samples were analyzed for prostaglandin (PG) F2 alpha by radioimmunoassay. Peripheral PGF2 alpha concentrations peaked upon oviposition of a HS egg in both ASA-fed hens as well as the controls (0% ASA). The levels of dietary ASA and the duration of time the ASA was administered did not affect baseline or peak PGF2 alpha concentrations. It was concluded that either the timing or route of administration of ASA resulted in the failure of ASA to effectively reduce peak peripheral PGF2 alpha concentrations.

Response of layer breeders to dietary acetylsalicylic acid. 3. Effects on fertility and hatchability of embryos exposed to control and elevated incubation temperatures.

Because acetylsalicylic acid (ASA, aspirin) is a common antipyretic drug, there has been considerable research on the effects of ASA on mammalian embryonic development. However, very limited research has been conducted on the effects of ASA on avian development and hatchability. The present study investigated the effect of dietary ASA on fertility and hatchability and whether embryos of breeder hens fed ASA, as compared with embryos of hens fed a control diet, would survive elevated temperatures during incubation. White Leghorn layer breeders were fed 0, .025, .050, .100, .200, and .400% ASA for the first 13 mo of egg production. When averaged over 13 mo, hens fed .40% dietary ASA demonstrated a decline in fertility (P < .03), hatchability of fertile eggs (P < .04), and hatchability of eggs set (P < .02). Chicks from hens fed .10% ASA weighed more than chicks from hens receiving 0, .025, .20, or .40% ASA (P < .01). When embryos were incubated at elevated temperatures of 42.8 or 43.3 C for 5.5 to 12 h on Day 16 of incubation, hatchability declined. Also, ASA fed to layer breeders did not improve hatchability of embryos exposed to elevated incubation temperatures when compared with embryos exposed to a control incubation temperature (37.2 C). During Month 9 of production, chicks from hens fed .05 and .10% ASA and exposed to an elevated temperature of 42.8 C for 9 h on Day 16 of incubation weighed more than similarly heat-stressed chicks of hens fed 0, .20, or .40% ASA (temperature by diet interaction, P < .03).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of subcutaneous infusion of pituitary-derived chicken growth hormone on growth performance of broiler pullets.

The effect of subcutaneous infusion of pituitary-derived chicken growth hormone (p-cGH) on plasma hormone/metabolite status and growth performance of young broiler pullets was investigated. Two-week-old pullets were surgically prepared and maintained via a fluid swivel/spring tether/harness system. Birds were subcutaneously infused 24 h a day for 21 days with 1.0 mL/day of either a p-cGH or vehicle (control) solution (20 micrograms/kg BW/day). Subcutaneous infusion of p-cGH had no significant effect on growth performance parameters in comparison with controls. Differences between levels of overall feed intake, net BW gain, feed efficiency, and carcass composition were not significant for treatments. However, dressing percentage was lower in p-cGH treated birds than in vehicle infused birds (P less than .04). Growth hormone treatment resulted in a modest degree of enlargement of the liver (P less than .06). However treatment had no effect upon wet weights of other measured organs or upon parameters of longitudinal bone growth, including length and mass of the tibiotarsus and width of the epiphyseal growth plate. Differences between treatment groups in preinfusion plasma concentration of GH, insulin, and glucose were not significant. Postinfusion plasma concentrations of GH were elevated over three-fold by p-cGH treatment (P less than .0001), with no treatment differences in plasma insulin or glucose concentrations. This study indicated that a sustained, 24-h elevation in plasma GH concentration in response to a physiological dosage of exogenous p-cGH is ineffective in altering growth performance of young, rapidly growing meat type chickens.

Effect of pattern of administration on the response to exogenous pituitary-derived chicken growth hormone by broiler-strain pullets.

The effect of pulsatile versus continuous intravenous administration of exogenous, pituitary-derived chicken growth hormone (cGH) on growth performance and endocrine/metabolite status of broiler-strain pullets was determined. In a first study, 8-week-old pullets, surgically prepared with intravenous catheters and maintained via a fluid swivel/spring tether/harness system, were administered cGH or vehicle (control) over a 10-min period every 90 min (i.e., 90-min pulse pattern) for 21 consecutive days. Feed intake, body weight gain, and carcass yield and composition were determined in conjunction with plasma concentrations of several hormones and metabolites. In a second study, 8-week-old pullets were intravenously administered cGH or vehicle continuously for 21 consecutive days under the same conditions as for Study I. Pulsatile cGH administration improved feed efficiency (P less than 0.02), increased longitudinal bone growth (P less than 0.02) and mass (P less than 0.01), and reduced abdominal fat pad size (P less than 0.05) and total carcass lipid (P less than 0.09) over the 21-day treatment period in comparison to vehicle infusion. Pulsatile cGH administration also resulted in hepatomegaly, a marked elevation in plasma IGF-I (P less than 0.003) and T3 (P less than 0.005) concentrations, and a reduction in plasma T4 levels (P less than 0.04). In contrast to the above responses to pulsatile cGH, continuous intravenous cGH administration significantly impaired feed efficiency (P less than 0.01) and had no significant effect on abdominal fat pad or liver size or on total carcass lipid, but did result in widening of the epiphyseal growth plate (P less than 0.06) and increased bone mass (P less than 0.01) in comparison to vehicle infused controls. These studies demonstrate that in the broiler chicken, for which endogenous plasma GH concentrations are pulsatile at early ages in conjunction with rapid growth, the pattern of exogenous GH administration is clearly a factor influencing the nature of response to the hormone.

Effect of various levels of avilamycin on the performance of growing-finishing swine.

A series of 12 trials involving 1,710 crossbred pigs was conducted at eight geographical locations in the United States to determine the effect of avilamycin on average daily gain (ADG), average daily feed (ADF) and feed-to-gain ratio (F/G) of growing-finishing swine. Eight of 12 trials evaluated avilamycin concentrations at 0, 5, 10, 20, 40 and 60 ppm, while an additional four trials evaluated avilamycin concentrations at 0, 10, 20 and 40 ppm in swine grower and finisher diets fed ad libitum. All trials were conducted using a randomized complete block design with data from the 12 trials pooled for statistical analysis. Pigs fed 5, 10, 20, 40 or 60 ppm avilamycin had increased (P less than .05) ADG over control pigs. No differences were detected for ADF between control and avilamycin-fed pigs. Pigs fed 10, 20, 40 or 60 ppm avilamycin had improved (P less than .05) F/G over control animals. Average daily gain, ADF and F/G for pigs fed 0, 5, 10, 20, 40 or 60 ppm avilamycin were: 749, 763, 767, 769, 771 and 771 g; 2.38, 2.40 2.39, 2.41, 2.38 and 2.38 kg; and 3.17, 3.15, 3.12, 3.13, 3.09 and 3.09, respectively. Linear plateau procedures showed that the effective dose range of avilamycin for the growing-finishing phase is 5 to 10 ppm for improving ADG and 10 to 60 ppm for improving F/G.

Effects of feeding tylosin to layers exposed to Mycoplasma gallisepitcum.

Two experiments are reported in which the effect of tylosin upon the development of Mycoplasma gallisepticum (MG) infection in replacement layers was monitored by serological and cultural methods. Concentrations of tylosin tested included 0, 22, 38.5, and 55 ppm. Egg production and feed consumption data were collected for one year. Tylosin slowed the rate of spread of MG infection as measured by serological and cultural methods. The effect of tylosin on the spread of MG infection was dose related. Hen day egg production peaked at 85 to 87% in the mediated groups, while controls peaked at 81 to 84%. The magnitude of tylosin effect on production increased with time to a maximum difference of 10 to 12% at 52 weeks. Feed efficiency was markedly improved by all concentration of tylosin ranging from 5% at peak production to 12 to 18% at 52 weeks. The incidence of shell-less or soft shelled eggs was markedly reduced in the tylosin treated group.