Growth rates of main and reciprocal crosses of Isa Brown and local chickens

The absolute and relative instantaneous growth rates of F1 hybrid chickens were determined at 2- 10 and 12-20 week periods of growth. The hybrids were hatched from eggs laid by 69 Isa Brown and local chicken parents. A total of 123, 49 and 116 chicks of Isa Brown x frizzle feathered (IBxF), Isa Brown x naked neck (IBxNa) and Isa Brown x normal feathered IBxN) main crosses and 137, 42 and 64 chicks of frizzle feathered x Isa Brown (FxIB), naked neck x Isa Brown (Na x IB) and normal feathered x Isa Brown (NxIB) reciprocal crosses, respectively were produced at day-old. The greatest absolute growth rates of 49.44g/week at 2-10 weeks and 71.11 g/week at 12-20 weeks were obtained from IBxN and FxIB genotypes, respectively. Instantaneously, IBxNa had the greatest rate of 0.28 g/time at 2-10 weeks, while IB x F and Na x IB each at 12-20 weeks were found to grow at the greatest rate of 0.091 g/time, respectively. It was concluded that normal and naked neck genes could be utilised in main crosses to develop fast growing broiler chicks while frizzle and naked neck genes could be used in reciprocal crosses to improve good laying pullets without precocious maturity.

EFECTO DE LA SALINIDAD SOBRE EL CRECIMIENTO POBLACIONAL Y EL RENDIMIENTO DEL ROTIFERO BRACHIONUS PLICATILIS (CEPA CIENAGA GRANDE DE SANTA MARTA)

The effect of salinity on the population growth and yield of a strain of Brachionus plicatiiis (O.F. Muller, 1786) was determined by two laboratory experiments. The rotifer B. plicatiiis was isolated from the plankton of the Ciénaga Grande de Santa Marta, Colombia, and cultivated in laboratory under different salinity conditions. The local microalgae Chiorella sp., also isolated in laboratory, was used as food for the rotifers. Salinity values ranged from 3 to 24 o/oo in the first experiment and 30 to 45 o/oo in the second. It was found that these rotifers grow and exhibit a" high adaptive capability when cultured at salinities ranging from 16 to 40o/oo. The rotifer curves of population growth were negative at salinities under 16 o/oo. At salinities of 30, 36, and 40 o/oo the maximum densities were similar in the ninth day. Although maximum densities were somewhat lower at 45 o/oo salinity, no significant statistical differences were found. Maximum values of density (d), yield (y), instantaneous growth rate (k) and doubling time (td) corresponded to a salinity of 36o/oo.

Instantaneous Growth Rate of Freshwater Nannochloropsis spp. at Different Salinity Levels

A study was conducted to determine the instantaneous growth rate of freshwater Nannochloropsis spp. at five different salinity levels (T1, 0 ppt - control; T2, 5 ppt; T3, 10 ppt; T 4, 15 ppt; and T5, 20 ppt) and were arranged in a Complete Randomized Design (CRD). Nannochloropsis spp. was cultured in fifteen 500 ml plastic experimental bottles based on the assigned treatment for eleven days. Initial sampling was done during the start of the experiment, and everyday thereafter. Cell density was counted using haemacytometer and viewed under the microscope. Results showed that the highest cell density and instantaneous growth rate of freshwater Nannochloropsis spp. was obtained in Treatment 3 with 18,510,000.00 cells/ml and16.00±0.36 cells/ml, respectively, while Treatment 5 had the lowest cell density and growth rate (10,040,833.33 cells/ml; 15.38±0.46 cells/ml).One-way ANOVA and Duncan’s Multiple Range Test revealed there was a significant difference (p<0.05) on the days of culture (days 3, 7 and 8) among treatments. Results for both cell density (cells/ml) and instantaneous growth rate (K) proved that freshwater Nannochloropsis spp. can tolerate a wider range of salinity from 5 ppt to 15 ppt. However, further studies should be conducted at a wider range of salinity levels and other variables such as nitrogen levels and light intensity to have a complete picture of the reproductive biology of this species. Keywords - Aquatic Ecology, instantaneous growth rate, freshwater Nannochloropsis spp., salinity levels, experimental design, Philippines, Asia