Weaning weight response of pigs to simple and complex diets

Five experiments were conducted to determine (1) the value of simple vs complex diets on gains and feed conversion of pigs weaned at a constant age but varying in weight, (2) the optimum postweaning time to change from a complex to a simple diet and (3) the effect of previous treatment on subsequent performance. In the first experiment, pigs were weaned at 3 wk +/- 3 d and assigned within four weight groups (4.1, 5.0, 5.6 and 6.7 kg) to a simple or complex diet that was fed for 28 d. The complex diet improved (P less than .01) pig performance in all weight groups. As anticipated, the heavier pigs (5.6 and 6.7 kg) ate more (P less than .02) and grew faster (P less than .03) than did their lighter weight littermates (4.1 and 5.0 kg). The second experiment involved pigs weaned at 3 wk +/- 3 d that were assigned within two weight groups (4.4 and 6.6 kg) and fed a complex diet for 10 d, after which one-half of each weight group was switched to a simple diet. Pigs fed the complex diet for the entire 24-d period gained faster (P less than .05) and were more efficient (P less than .05) than those changed to the simple diet after 10 d. The heavier weight (6.6 kg) pigs ate more (P less than .02) and gained faster (P less than .02) than did the lighter weight (4.4 kg) pigs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in light intensity during the rearing period can influence egg production in domestic fowl

1. A total of 240 Shaver White and 240 ISA Brown pullets that had been reared in multi-bird cages on a 10-h photoperiod, and maintained at a light intensity of 3 or 25 lux, or changed from 3 to 25 lux or from 25 to 3 lux at 9 or 16 weeks of age, were moved into individual-bird cages at 20 weeks and transferred to 15-h photoperiods at 25 lux. 2. In both breeds, birds transferred from 3 to 25 lux at 16 or 20 weeks laid significantly more eggs than birds maintained on the brighter intensity from one day or increased to it at 9 weeks. 3. Mean egg weight, shell deformation, albumen height, feed intake and body weight gain in lay were not significantly affected by the light intensity treatments during the rearing period. There was, however, a small, but significant, negative correlation of egg numbers with mean egg weight, although this only partially explained the difference in egg numbers. The differences in egg production were unrelated to rate of sexual maturation.     

Constant photoperiods and sexual maturity in broiler breeder pullets

1. Broiler breeder pullets were maintained on 10-, 11-, 12-, 13-, 14- or 16-h photoperiods to determine the effect of constant photoperiods on sexual development in broiler breeders. The birds were fed to achieve a 2100 g body weight at approximately 17 or 20 weeks to see if the photosexual response was modified by rate of growth. 2. In both body weight groups, pullets maintained on 10h were the first to reach sexual maturity (50 eggs/100 bird-d), and these and the 11-h pullets matured significantly earlier than any of the other photoperiod groups. Pullets maintained on 13 or 14 h matured latest, at about 3 weeks after the 10-h pullets, though both were only marginally later than the 12- or 16-h birds. These differences in maturation probably reflect the different rates at which photorefractoriness is dissipated in broiler breeders reared on photoperiods that vary in their degree of stimulatory competence. 3. There were no significant interactions among the photoperiods and the ages at 2100 g; faster-growing birds consistently matured about 10 d earlier than conventionally grown pullets.     

Amino acid interactions in chick nutrition. 4. Growth, food intake and plasma amino acid patterns

A series of experiments has been conducted with chicks to study the effects of excess lysine, leucine and incomplete mixtures of amino acids on growth, food intake and plasma amino acid patterns.

Excess lysine induced a marked depression in growth within 48 h. Towards the end of the experiment, the chicks lost weight and showed no signs of adaptation to the excess dose of lysine. The plasma concentration of arginine fell within 24 h of feeding excess lysine but the reduction in food intake did not occur until 6 d of the experiment had elapsed. Excess leucine similarly caused a rapid retardation of growth which was followed subsequently by a depression in food intake. Mixtures of amino acids lacking in leucine, isoleucine and valine also induced marked growth inhibitions the severity of which were enhanced by the inclusion of leucine and isoleucine in the mixtures. Growth tended to be adaptive in chicks fed on the incomplete amino acid mixtures but non‐adaptive in those fed on excess leucine.

Pair‐feeding studies indicated that appreciable differences in weight gain still occurred when food intake was equated between control groups and groups receiving excess lysine or leucine.

The results of the present study indicate that the depression in food intake cannot account completely for the ill‐effects of excess lysine and leucine. They also suggest that the adverse effects of lysine and leucine are distinct from those caused by incomplete mixtures of amino acids.     

FERTILE TILLER PRODUCTION AND SEED YIELD IN MEADOW FESCUE (FESTUCA PRATENSIS L.)

The seed-producing capacity of two varieties of meadow fescue, S215 and S53, sown at three different spacings, was compared. One level of nitrogen was applied on three different dates in the spring. Tiller counts were made periodically during the growth of the crop. Fertile-tiller production was found to be related to vegetative growth.
The varieties differed not only in yield, but also in growth dynamics. A larger percentage of overwintering shoots became fertile in the hay variety, than in the pasture variety.
Drill spacings had significant effects on plant establishment and on vegetative-and fertile-tiller numbers. In both years N applied in March gave the highest production of fertile tillers. Date of N application did not produce marked trends in yield. The influence of spacing and date of N application on the number and density of spikelets indicated that the plant adjusted itself to environmental factors. Thus spikelet numbers were reduced in early heads with narrower drill spacing and with late applications of N. Head emergence was earlier in narrow drills, but time of N application in the spring did not produce significant differences in this respect.