Dopamine-melatonin neurons in the turkey hypothalamus controlling seasonal reproduction
S. Kang, A. Thayananuphat, T. Bakken, and M. El Halawani
Department of Animal Science, University of Minnesota, St Paul
The neural and neurochemical substrate mediating the reproductive photoperiodic time measurement (PTM) in birds has not been denitively established. Our previous studies have shown that a 30 min light pulse induced c-fos mRNA expression in dopamine (DA) neurons within the premammillary nucleus (PMM) of the turkey caudal hypothalamus, as well as in GnRH-I neurons of the anterior hypothalamic/pre-optic area, where GnRH-I mRNA was also found. Double-label immunocytochemistry (ICC) showed these PMM neurons to be immunoreactive (ir) to both tyrosine hydroxylase (TH; the rate limiting enzyme in DA biosynthesis) and melatonin (MEL). Moreover, the intensity of MEL staining appeared greater in brain sections obtained during night than day. We have shown that mRNA expression of TH and tryptophan hydroxylase 1 (TPH1; the first enzyme in MEL biosynthesis), cycle rhythmically and with opposite phases in the PMM neurons of birds kept under a diurnal illumination cycle (12-h light: 12-h dark; LD). These neurons can generate 24 hr TH and TPH1 mRNA expression rhythms in constant light (LL) and constant dark (DD). In addition, the expression patterns and amplitudes of TH and TPH1 mRNAs were different between long and short photoperiods. It is suggested that endogenous oscillators within PMM neurons appear to be important in regulating the DA and MEL rhythms which are required to drive the circadian system controlling reproductive seasonality in turkeys.
Clock gene expression in the premammillary nucleus (PMM) and the pineal gland of turkey hens.
B. Leclerc1, S. Kang1, A. Thayananuphat1, C. Howell1, S. Kosonsiriluk2, Y. Chaiseha2, and M. E. El Halawani1
Recent findings from our laboratory have implicated the PMM as a site of putative photoreceptive neurons. These neurons are shown to express both dopamine (DA) and melatonin (MEL), with Daergic activity up regulated during the light phase and MELergic activity during the dark phase of the light-dark illumination cycle. Theses neurons reach threshold activation (as indicated by c-fos mRNA expression) when a light period is provided during the photosensitive phase (14hr after light on). And, this is coincided with the activation of gonadotropic releasing hormone-I (GnRH-I) and the upregulation of GnRH-I mRNA expression. It is hypothesized that PMM DA-MEL neurons may be a component of a biological clock involved in reproductive photoperiodic time measurement (PTM), controlling seasonal reproduction in turkeys. In this study we cloned turkey’s clock genes including Clock, Per2, Per3, Bmal1, Cry1 and Cry2 and examined their expression in the PMM which was compared to that expressed by the pineal gland. Turkey hens maintained on short photoperiod (6L:18D) were subjected to a 30 min light pulse at circadian times (CT) 8, 14 and 20. Tissues were collected 30 min, 1 hour and 3 hours following the onset of the light pulse. In the pineal gland, Per2 mRNA expression level was highest followed by mRNA expression of Cry1, Cry2, Per3, Clock and Bmal1. However, Per2 gene was not significantly modulated by light (one-way ANOVA; P>0.05) across all CTs. The expression of Per2, Cry1 and Cry2 genes was also examined in the PMM of turkeys following the 30 min light exposure. The expression of Cry1 and Per3 transcripts was enhanced 2-3 fold by the 1 hour light pulse at CT14 and CT20 and both were statistically significant by the ANOVA (P<0.05) and confirmed by the Tukey-Kramer test. It is not clear at this time whether clock genes are involved in mediating photic information to the reproductive neuroendocrine system of turkeys.
1University of Minnesota, St. Paul
2Suranaree University of Technology, Thailand
Response of market turkey toms to dietary protein and threonine levels in diets containing corn distillers dried grains
S.L. Noll and J. Brannon
Department of Animal Science, University of Minnesota, St. Paul
The response of market turkey toms to diet threonine level was examined during 8 to 19 wks of age. Diets were formulated to contain 90, 94, 100, and 106% NRC digestible thr from intact protein. In addition, supplemental thr was used to reach 100 or 106% NRC thr. Diets were composed primarily of corn, soybean meal, poultry by-product meal (PBM, 10%) and corn distillers dried grains with solubles (DDGS, 20%). Large White male turkey poults (Nicholas strain) were randomly assigned to pens (10/pen) at 8 wks of age. The treatments were (T): 1.
Corn soy control, 100% NRC thr; 2. PBM-DDGS 106% NRC thr; 3. As T2, plus 6% NRC thr; 4. As T2, 100% NRC thr; 5. As T4, plus 6% NRC thr; 6. As T4, plus 12% NRC thr; 7. As T2, 94% NRC thr; 8. As T7 plus 6% NRC thr; 9. As T7 plus 12% NRC thr; 10. As T2, 90% NRC thr; 11. As T10 plus 10% NRC thr. All diets were supplemented as needed with lys and met to meet the specic NRC recommendations for these amino acids. The ratio of calcium: inorganic phosphorus was maintained at 2:1. Each diet was fed to 8 replicate pens. The experimental design was a completely randomized block design. Dietary treatment affected body weight at all ages (P<.0001). BW at 19 wks of age was similar for T 1, 2, 3 and 4. Decreasing diet NRC thr to 94 and 90% signicantly decreased BW while supplementation with thr improved body weight but not to the level of the control at 100% NRC. Increased average daily gain response to supplemental thr (6% NRC thr) was observed for 100, 94, and 90% NRC thr treatment groups during 8-11 and 11-14 wks of age; and, only in the 90% NRC thr treatment during 14-17 and 17-19 wks of age. Improved feed efficiency in response to supplemental thr (6% NRC thr) was observed for the 94% NRC treatment during 8-11 wks; and, for the 90% NRC thr group during 8-11 and 17-19 wks of age. In diets containing a large amount of alternative protein (10% PBM and 20% DDGS), a gain response to supplemental thr was observed when diet thr from intact protein was less than 106% NRC during 8-11 wks, less than 100 % NRC during 11-14 wks, and less than 94% NRC during 14-19 wks of age.
Nutritional value of corn distiller dried grains with solubles (DDGs): Influence of solubles addition
S.L. Noll1, J. Brannon1, and C. Parsons2
Batches of corn distiller dried grains were produced with varying levels of solubles (syrup) added back to the wet grains (mash) in cooperation with a Minnesota ethanol plant. The batches produced contained syrup added at approximately 0, 30, 60, and 100% of the maximum possible addition of syrup to mash. Actual rates of syrup addition were 0, 12, 25, and 42 gal/minute. The different combinations of mash and syrup were dried at the plant with a lag of 60 minutes in between the changes for the different rates of syrup addition. Samples of each lot of material were taken and were chemically analyzed. Digestible amino acid content was determined with cecectomized roosters. True metabolizable energy (TMEn) was determined in intact young growing turkeys. Regression analyses and correlation coefficients (Pearson) were conducted to determine the extent of the relationship between the level of solubles added and the resulting nutrient content. Particle size was greatly affected with larger and more variable particle size with the highest level of solubles addition. The larger particles (“syrup balls”) were readily apparent in the 100% batch and are of concern for product quality for poultry feeds. Content of fat and ash increased with solubles addition. Fat content increased from 8% in the dried grains to 10.5% (as fed basis) where 100% of the solubles were added back. The TMEn content also increased with solubles addition from 2712 kcal/kg for the dried grains to 3743 kcal/kg where 100% of the solubles were added back. Mineral content, especially for magnesium, sodium, phosphorus, potassium, chloride, and sulfur increased as the level of solubles addition increased. Protein and amino acid content showed very little change in the various products. True amino acid digestibility coefficients of the essential amino acids tended to be negatively correlated with solubles addition. The results indicate that solubles addition has the largest effect on particle size, color, and; content of fat and minerals.
1University of Minnesota, St. Paul
2University of Illinois, Champaign
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