Rancidity development in feeds and feed ingredients reduces the feeds' nutritive value and produces toxic peroxides. This investigation was conducted to determine the effects of different levels of peroxide on broiler performance and to determine the effectiveness of ethoxyquin in ameliorating the adverse effects of peroxides. Poultry fat was oxidized to contain 0, 50, 100, and 175 meq peroxide/kg and added to diets to provide 0, 2, 4, or 7 meq peroxide/kg feed, respectively. Liquid ethoxyquin was incorporated into the diets at 0, 62.5, and 125 ppm. Each of the 12 diets was fed to 8 replicate pens with 35 males and 35 females/pen. Body weights at 21 and 42 days of age were significantly lower in birds fed diets containing 4 or 7 meq peroxide/kg feed. At 49 days of age, the reduction in body weight was significant only at the 7 meq/kg level. Reductions in feed efficiency showed a similar pattern, but the depression was significant only at the highest peroxide level. Supplementation of 62.5 and 125 ppm ethoxyquin resulted in significantly heavier birds at 49 days of age but had no significant effect on feed efficiency. Beneficial effects of ethoxyquin supplementation were evident at higher peroxide levels. The study showed that at least 4 meq peroxide/kg feed was required to significantly affect bird performance, and that the addition of ethoxyquin could alleviate the deleterious effects of dietary peroxide.

Lipogenic and lipolytic capacities were examined in fasted and nonfasted 28-day-old chicks from high-weight (HW) and low-weight (LW) selected lines. Lipogenesis was assessed in liver and bone (sternum) tissues through the activities of malic enzyme (EC 1.1.1.40), citrate cleavage enzyme (EC 4.1.3.8), and acetyl coenzyme A carboxylase (EC 6.4.1.2), as well as through the in vitro incorporation of acetate-1-14C into liver and bone lipid fractions. Lipolysis was estimated through the in vitro release of free fatty acids (FFA) from abdominal adipose tissue and through plasma FFA. Fasting depressed lipogenesis and increased lipolysis. Regardless of the feeding state, LW chicks exhibited higher lipogenic and lipolytic capacities than their HW counterparts, suggesting that lipid degradation may be relatively more important than synthesis in determining net fat deposition. In addition, the incorporation of radioactive acetate into bone lipid was associated with detectable activity of lipogenic enzymes, providing further evidence that the skeleton is an important site of lipogenesis in the chicken.

Lipogenic and lipolytic comparisons were made among normal and dwarf adult males from both high-weight (HW) and low-weight (LW) selected lines. Six nonfasted birds from each of the four populations were sacrificed, and in vitro lipogenesis and lipolysis were measured in liver, adipose, and bone tissue. Also determined were activities of acetyl CoA carboxylase (E.C.6.4.1.2), NADP-malate dehydrogenase (E.C.1.1.1.40), ATP-citrate lyase (E.C.4.1.3.8), and plasma-free fatty acids (FFA). In comparison with the HW chickens, the LW males tended to exhibit higher activities of lipogenic enzymes, a greater capacity to incorporate acetate-1-14C into liver slices, an increased mobilization of FFA from adipose tissue, and high concentrations of FFA in plasma. The results indicated that the maintenance of increased postmaturational body fat associated with selection for high body weight was primarily the result of decreased lipolysis rather than enhanced lipogenesis. Effects of the dwarf allele on lipogenesis and lipolysis were not clear. Acetate incorporation into bone tissue was substantially higher than for adipose tissue, suggesting that bone may be an important site of lipogenesis in the fowl.

Three groups of 96 crossbred gilts each were weaned at 4 to 5 wk of age (avg wt, 7.2 kg) and assigned to four treatments in a 2 X 2 factorial arrangement (ad libitum vs 75% of ad libitum energy intake and 100 vs 150% of NRC-recommended daily Ca and P). The effects on feedlot performance and on foot and leg scores and measurements were examined at approximately 50 and 100 kg body weight. Also, pigs were subjectively scored for overall structural soundness at the same weights. Limit-fed gilts consumed 78.1% as much feed as gilts fed ad libitum. Average daily gain of the limit-fed gilts was 86.7% that of the gilts fed ad libitum (P less than .01), and feed/gain was nonsignificantly improved by 8.4% for limit-fed gilts. The feeding of 150% of NRC-recommended levels of Ca and P resulted in a 5% increase (P less than .05) in daily gain, but daily feed intake and feed/unit of gain were not significantly affected. At the same age, almost all foot and leg measurements were larger for gilts fed ad libitum than for limit-fed gilts. However, when the values were adjusted for body weight, there was little or no measureable effect of energy intake. Elevated Ca and P levels had minimal effects, with only a trend toward larger measurements for gilts fed 150% of NRC-recommended daily Ca and P levels. Foot and leg measurements increased from 50 to 100 kg and were larger for the outside toes than for the inside toes for both front and hind feet. Energy intake and elevated Ca and P levels had little effect on the incidence and severity of toe lesions. The incidence of pad and horn lesions increased over time and was much greater on the outside toes on the front and hind feet. Restricted feeding and increased Ca and P levels did not improve overall structural soundness.

Boars were assigned at 5 wk of age in a 2 X 2 factorial arrangement to two energy (ad libitum and 75% of ad libitum) and two Ca and P levels (100 and 150% of the National Research Council daily recommended amounts) to determine the effect of reduced growth rate and elevated Ca and P intake on foot and leg measurements, pad and horn incidence and severity of lesions, and structural soundness. There were 20 boars/treatment; 15 boars from each treatment were necropsied at 10 +/- 2-d intervals from 80 to 220 d of age (45 to 185 d on test), with the remaining five boars in each treatment being necropsied at 220 d of age. Feet and leg measurements were taken and toe pads and horns were scored initially and after 78 and 131 d on when necropsied. Boars remaining after 130 d on test were scored for overall structural soundness. Toe size and circumference and length of limbs increased as boars grew, with larger values for ad libitum-fed compared with limit-fed boars when observed at a constant age. However, when these values were corrected for body weight, the effect of energy was generally removed and, in some cases, reversed. Limit-fed boars appeared to have fewer pad and horn lesions, but the effects were inconsistent. In general, Ca and P levels had little or no effect on toe and limb sizes and pad and horn lesion scores, whether or not the values were expressed on a constant age or corrected body weight basis. A comparison of inside and outside toes on the front and hind feet revealed that outside toes were larger than inside toes, with the magnitude of the difference much larger for the hind foot than for the front foot. The hind inside toes had fewer pad and horn lesions. Structural soundness scores were more desirable in ad libitum-fed compared with limit-fed boars; but, elevated Ca and P levels had no effect. Thus, these data do not support a hypothesis that structural soundness can be improved by reducing the growth rate of developing boars or by feeding an elevated level of Ca and P.