Effect of pharmacological concentrations of zinc oxide with or without the inclusion of an antibacterial agent on nursery pig performance.

A study involving nine research stations from the NCR-42 Swine Nutrition Committee used a total of 1,978 crossbred pigs to evaluate the effects of dietary ZnO concentrations with or without an antibacterial agent on postweaning pig performance. In Exp. 1, seven stations (IA, MI, MN, MO, NE, ND, and OH) evaluated the efficacy of ZnO when fed to nursery pigs at 0, 500, 1,000, 2,000, or 3,000 mg Zn/kg for a 28-d postweaning period. A randomized complete block experiment was conducted in 24 replicates using a total of 1,060 pigs. Pigs were bled at the 28-d period and plasma was analyzed for Zn and Cu. Because two stations weaned pigs at < 15 d (six replicates) and five stations at > 20 d (18 replicates) of age, the two sets of data were analyzed separately. The early-weaned pig group had greater (P < 0.05) gains, feed intakes, and gain:feed ratios for the 28-d postweaning period as dietary ZnO concentration increased. Later-weaned pigs also had increased (P < 0.01) gains and feed intakes as the dietary ZnO concentration increased. Responses for both weanling pig groups seemed to reach a plateau at 2,000 mg Zn/kg. Plasma Zn concentrations quadratically increased (P < 0.01) and plasma Cu concentrations quadratically decreased (P < 0.01) when ZnO concentrations were > 1,000 mg Zn/kg. Experiment 2 was conducted at seven stations (KY, MI, MO, NE, ND, OH, and OK) and evaluated the efficacy of an antibacterial agent (carbadox) in combination with added ZnO. The experiment was a 2 x 3 factorial arrangement in a randomized complete block design conducted in a total of 20 replicates. Carbadox was added at 0 or 55 mg/kg diet, and ZnO was added at 0, 1,500, or 3,000 mg Zn/ kg. A total of 918 pigs were weaned at an average 19.7 d of age. For the 28-d postweaning period, gains (P < 0.01), feed intakes (P < 0.05), and gain:feed ratios (P < 0.05) increased when dietary ZnO concentrations increased and when carbadox was added. These responses occurred in an additive manner. The results of these studies suggest that supplemental ZnO at 1,500 to 2,000 mg Zn/kg Zn improved postweaning pig performance, and its combination with an antibacterial agent resulted in additional performance improvements.

Energy restriction and testosterone implants alter ornithine decarboxylase gene expression in kidney of female rats.

Effects of testosterone and energy restriction (30%) on enzyme activity and mRNA level of ornithine decarboxylase (ODC) were studied in 19-wk-old female Sprague-Dawley rats. Testosterone implantation for 1 wk elicited a sixfold increase in ODC activity and a fourfold increase in ODC mRNA transcripts in the kidney. Energy restriction also increased renal ODC activity. Further, the 56% increase in ODC enzyme activity observed in the testosterone-implanted, energy-restricted group was greater than the 24% increase in the placebo-implanted, energy-restricted group. No changes in renal ODC mRNA levels were observed in the energy-restricted groups. These observations suggest that translational or post-translational mechanism(s) are involved in the greater renal ODC activity in energy-restricted rats.

Effects of compensatory growth on milk protein gene expression and mammary differentiation.

This experiment was conducted to develop an understanding of mechanisms responsible for effects of a compensatory (stair-step) growth pattern on the expression of milk protein genes and mammary differentiation. One hundred thirty weanling female rats were randomly assigned to either a control or a test group (compensatory growth). Early lactating mammary tissues from the compensatory growth group showed an increase in the RNA:DNA ratio, protein:DNA ratio, DNA, RNA, and protein while exhibiting a decrease in the lipid content as compared with those of the control group (2.2, 1.6, 1.7, 3.8, 2.8, and 0.5 times, respectively). Mammary tissues from the compensatory growth group contained about 1.1- to 1.4-fold more total cytoplasmic mRNA for caseins and whey acidic protein than those of the control group. The compensatory growth pattern increased beta-casein mRNA accumulation, milk protein secretion, and amino acid uptake in mammary acinar culture (1.3, 1.3, and 1.1 times, respectively) compared with those of the control group. These results indicate that the compensatory growth pattern increases milk protein mRNA transcripts and may contribute to an increase in the functional activity of the mammary gland.

Phosphorus bioavailability in the chick: effects of protein source and calcium level.

Three experiments utilizing 1,104 broiler cockerels were conducted to establish optimum dietary conditions for the determination of phosphorus (P) bioavailability. The reference P source was KH2PO4. A response-surface design and purified diets containing casein as the protein source were utilized in Exp. 1 Various levels of calcium (Ca) and P supported near-maximal gain in tibia ash. Optimal gain in tibia ash was attained at 1.8% Ca and .55% total (highly available) P. Regression equations describing the gain in tibia ash in response to added P from KH2PO4 for diets in Exp. 2 that contained casein and isolated soybean protein had different (P less than .05) slopes. Diets moderately limiting in available P exhibited reduced gain in tibia ash content if more than 1.4% total Ca was present. A corn-soybean meal diet was utilized in Exp. 3. Partitioning of tibia ash gain into effects due to basal diet, added P from KH2PO4, or P from the test ingredient was investigated. Sunflower meals containing 42 or 28% crude protein were evaluated for P bioavailability. The P content of the meals was 21.6 and 22.7% available, respectively. The fiber of the sunflower hull did not interfere with P availability. Selection of diet ingredients is discussed with respect to the development of P bioavailability values for use in practical diets.

Effects of dietary protein and fiber on growth and selected cholesterol responses of rats.

The effect of dietary protein and fiber on growth and metabolic parameters in blood serum, liver and kidney were determined in a 2 X 5 factorial experiment involving 40 Sprague-Dawley rats. Treatment variables were two dietary protein levels (16 and 24%) and five acid detergent fiber levels (6, 10, 16, 24 and 34%). No difference in growth rate of rats was found due to varying levels of either protein or fiber in the diet. Increasing the dietary protein level from 16 to 24% resulted in an 18.5% reduction in blood cholesterol. The dietary treatment containing 16% fiber influenced most metabolic parameters examined, including blood serum cholesterol, liver cholesterol and total lipid content in liver and kidney. Rats receiving the diet containing 16% fiber had the highest serum cholesterol (88.9 mg/dl) and the lowest liver cholesterol (4.4 mg/g) as compared with other fiber groups.

Crop volume of chickens as affected by body size, sex, and breed.

Single Comb White leghorn (SCWL) hens, broiler cockerels, and two weight classes of SCWL roosters were utilized to determine the relationships of breed, sex, and body size to crop volume. Crop volume was significantly different (P less than .05) among all types of birds examined. Significant differences (P less than .05) of crop volume per kilogram body weight occurred between birds of opposite sex within a breed and between birds of identical sex but differing breed. However, within a breed, birds of identical sex but differing body size exhibited similar crop volume (cc/kg body weight).

Nutritive value of green or yellow foxtail, wild oats, wild buckwheat or redroot pigweed seed as determined with the rat.

Pure green foxtail (Setaria viridis Beauv.), yellow foxtail (Setaria lutescens Hubb.), wild oats (Avena fatua L.), wild buckwehat (Polygonum convolvulus L.) and redroot pigweed (Amaranthus retroflexus L.) seeds were fed to growing male rats in two experiments. In the first experiment, green or yellow foxtail and wild oats seeds were found to be first-limiting in the amino acid lysine. Green or yellow foxtail seed supplemented with lysine produced satisfactory rat growth. Digestible energy (DE) values of lysine-supplemented diets were: 3.478, 3.068 and 2.696 kcal/g dry matter (DM) for green foxtail, yellow foxtail and wild oats, respectively. Protein digestibility values were 77.1, 68.6 and 54.2 for the respective diets. Wild oats were accepted poorly by the rats, even after lysine supplementation. In the second experiment, rats required approximately 7 days to adapt to voluntary consumption of an amino acid-supplemented wild buckwheat diet. Moderate weight gain of weanling male rats was obtained because of high consumption of the wild buckwheat diet, which had 2.206 kcal DE/g DM and 52.5% crude protein digestibility. In contrast, initial high acceptability of the redroot pigweed diet quickly declined. Digestibility values for the redroot pigweed diet were 2.884 kcal DE/g DM and 54.6% rude protein digestibility. The relationship between digestibility values obtained with rats and those obtained with swine is discussed.