Intestinal absorption of corn oil and beef tallow was studied in White Leghorn male chicks during the periods of 2 to 7 and 8 to 15 days of age. Absorption of both fats was less at the earlier age. The corrected absorbability of corn oil increased from 84 to 95%; that of beef tallow from 40 to 79%. With both dietary fats, the greatest amount of fat appeared in the excreta at 5 and 7 days of age and then decreased rapidly within a 2-day period. Absorbability values for corn oil and tallow during the 8 to 15 day period agreed with generally accepted values found in the literature, while those for the 2 to 7 day period were lower. These results show that the newly hatched chick does not have full physiological capacity for fat absorption. However, this appears to develop rapidly after the first few days of life.

No abstract

The Pima cotton (Gossypium barbadense L.) plant is inherently late maturing and unsuitable for production in areas where highly probable late‐season rainfall coincides with boll opening. A field study was conducted between 1990 and 1992 to determine if the maturity of Pima cotton can be enhanced with applied N and P without reducing lint yield. Five preplant‐applied N rates up to 180 kg ha−1 in 1990 and up to 269 kg ha−1 in 1991 and 1992 were tested. Four P rates from 0 to 45 kg ha−1 in a factorial combination with N were tested in 1991 and 1992. Nitrogen did not affect yield, days to first flower, or estimated percent open bolls in 1990. Nitrogen deficiency significantly enhanced maturity in 1991 and 1992. In 1991, >70% of the total bolls opened by 153 days after planting (DAP) where no N was applied, compared with 178 DAP where 202 or 269 kg N ha−1 was applied. In 1992, 68% of the bolls in the 0 kg N ha−1 treatment opened by 142 DAP, compared with <55% for all other treatments. The 0 kg N ha−1 treatment also significantly increased the ratio of reproductive to total plant dry weight earlier during the boll development period; however, the maturity‐enhancing effect of N deficiency occurred at the expense of lint yield. Relative to the 67 kg N ha−1 treatment, zero N reduced lint yield by 277 kg ha−1 (26%) in 1991 and 214 kg ha−1 (18%) in 1992. Phosphorus deficiency reduced lint yield in 1991, but did not affect percent open bolls or reproductive efficiency in 1991 and 1992. Earliness of Pima cotton may, therefore, be managed more effectively by minimizing applied N rates than by manipulating P fertilization.

Broiler chicks from 2 to 4 weeks of age were fed control (0.23%) and deficient (0.115, 0.058%) levels of L-tryptophan. Separate groups of control chicks were pair-fed daily with the deficient chicks. Deficient chicks grew less efficiently than did pair-fed controls. Plasma triiodothyronine (T3) was elevated in deficient chicks, especially compared to pair-fed controls, and this was accompanied by lower reverse T3. Plasma thyroxine (T4) was also reduced with 0.059% tryptophan. However, thyroid weights and follicle diameters were unchanged. Reductions in weight gain and bone growth, increases in pituitary and pineal weights, and elevations in plasma GH occurred in the tryptophan-deficient chicks apart from any effect due to reductions in feed intake. Comb and testis size, and plasma testosterone were little affected by the deficiency. Based on changes in plasma T3 levels and feed conversion efficiencies, we conclude that tryptophan-deficient chicks show signs of relative hyperthyroidism and energy wastage compared to pair-fed controls. The elevations in plasma growth hormone and T3 support the concept that serotonin is a negative modulator of the synthesis or release of these hormones in chickens.

Four replicate experiments were conducted to determine the effects of pinealectomy and environmental lighting on growth and thyroid function in broiler cockerels. Birds were housed in battery brooders under a 14L:10D white light regime for 2 weeks and then allotted to lightcontrolled chambers. The light environments were 14L:10D white, 14L:10D green (narrow band, 545 nm peak), and constant dark. Surgery was performed when the chicks were 3 to 5 days old. At the end of the 32-day experimental period, weight gain and thyroid weights were measured and plasma triiodothyronine (T 3 ) and thyroxine (T 4 ) levels were determined by radioimmunoassay.Pinealectomy significantly (P<.05) depressed growth but did not affect thyroid weight or circulating plasma levels of T 3 or T 4 .Birds grown under white light were significantly (P<,05) lighter in weight than those grown under green light or darkness. Plasma T 4 levels were significantly (P<.05) elevated in chicks grown under green light while T 3 levels were signficantly (P<.05) higher in dark-treated birds when compared to either light treatment.

No abstract

Petiole NO3‐N concentration (PNN) has been recommended as an indicator of midseason N deficiency in upland cotton (Gossypium hirsutum L.). Its use in Pima cotton (G. barbadense L.) management, exspecially when early maturity is the goal, is not well documented. A 3‐yr study evaluated PNN as an indicator of N status in Pima cotton in order to identify a critical minimum PNN level for yield and early maturity. Treatments were five preplant applied N rates of 0 to 180 kg ha−1 in 1990 and 0 to 269 kg ha−1 in 1991 and 1992. The PNN was measured throughout boll development, starting ≈ 2 wk before or at first flower. Applied N significantly (P ≤ 0.05) affected PNN in 1991 and 1992, when residual soil N was low, but not in 1990, when residual N was high; differences among treatments in 1991 and 1992 were largest during early flowering. PNN was a good indicator of plant N status within but not across seasons. Based on early‐flowering samples, the critical PNN level for lint yield was 3.84 g kg−1 in 1991 and only 1.75 g kg−1 in 1992; in 1990, residual soil N alone resulted in PNN much higher than the critical levels in the other years. PNN < 2 g kg−1 in 1991 and < 1 g kg−1 in 1992 resulted in earlier maturity, but also resulted in less lint yield. Pima cotton PNN did not exceed an average of 11 g kg−1, in contrast to 24 to 30 g kg−1 reported for upland cotton. Plant growth or petiole anatomical variables that cause year‐to‐year variation in PNN should be identified and the necessary normalization made before PNN can be used as a midseason diagnostic tool in Pima cotton.

No abstract