83 PENINGKATAN DAYA HASIL DAN STAY-GREEN TANAMAN JAGUNG MELALUI SELEKSI TANDEM DAN INDEPENDENT CULLING LEVEL DI LAHAN KERING

ABSTRAK Tujuan penelitian adalah untuk mengetahui kemajuan seleksi tandem dan independent culling level selama tiga siklus di lahan kering dan mengetahui rerata daya hasil dan stay-green (brangkasan segar) populasi hasil seleksi dibanding dengan populasi awal dan varietas unggul Lamuru. Percobaan dirancang dengan rancangan acak kelompok, 3 blok di lahan kering Lombok Utara. Data dianalisa dengan analisis sidik ragam pada taraf nyata 5 persen. Rata-rata kemajuan seleksi per siklus setiap cara, diperoleh dari koefisien regresi antara karakter dengan siklus seleksi (populasi). Rerata perlakuan, diuji lanjut dengan BNT0,05. Hasil penelitian menunjukkan, bahwa kemajuan seleksi per siklus kedua cara hingga siklus ketiga untuk daya hasil dan brangkasan segar bersifat linear yang nyata. Besarnya kemajuan seleksi per siklus daya hasil secara tandem dan independent culling level berturut-turut 2,19 dan 2,74 g/tan; sedangkan untuk brangkasan segar sebesar 6,86 dan 13,77 g/tan. Rerata daya hasil dan bobot brangkasan segar, populasi hasil seleksi siklus ketiga kedua cara lebih besar dibanding populasi awal. Daya hasil populasi hasil seleksi independent culling level siklus ketiga lebih besar dibanding varietas Lamuru; namun populasi hasil seleksi tandem sama. ABSTRACT The objective of this research was to determine the progress of tandem and independent culling level selections until the three cycles on dry land and determine the mean grain yield and stay - green of selected plant populations compared with the base population and Lamuru superior variety. The experiment was designed using randomized block design with 3 replicates in North Lombok dry land. The observed data were analyzed using analysis of variance and LSD at the 5 percent significance level. The average of selection progress per cycle each way was obtained from the regression coefficient between the observed characters and the selection cycle (population). The results of the research showed that the progress of selection per cycle until the third cycle for yield (dry grain seed weight) and fresh biomass for both ways were significant linear. The selection progress of yield potential for tandem selection and independent culling level were 2,19 dan 2,74 g/tan respectivelly. The selection progress of biomass weight were 6,86 dan 13,77 g/tan for tandem selection and independent culling level. Mean of yield potential and fresh biomass weight for two ways were higher base population. Yield population of independent culling level selection three cycles were higher than Lamuru variety; but population result of tandem selection as the same.

Effect of temperament on performance of primiparous dairy cows

This study was designed to analyse the effect of milking behaviour (temperament) of primiparous dairy cows on their milk and reproductive performance as well as survival to the second lactation. Milk performance, reproductive performance and culling data on 12028 Polish Holstein-Friesian primiparous dairy cows were acquired from the SYMLEK database. Using the methodology of the Polish Federation of Cattle Breeders and Dairy Farmers, the temperament of the cows was assessed as: 1 - calm, 2 - normal, 3 - excitable or aggressive. Primiparous cows from the analysed population were characterized by averagely normal temperament and optimal milking speed. Daily and lactation yield depended (P≤0.01) on the temperament of cows. Excitable (aggressive) cows had higher daily and lactation yield compared to normal and calm cows. The temperament trait was found to correlate (P≤0.01) also with functional traits such as milking speed, survival to the second lactation, and culling level. As milking speed increased, the proportion of cows with calm temperament decreased and that of excitable (aggressive) primiparous cows increased. As the temperament score increased, so did the proportion of primiparous cows sold for further breeding. Excitable (aggressive) primiparous cows had the lowest chance of survival to the second calving.

Selection of extremes

SUMMARYA method of selection for two or more traits is investigated, where the selected individuals have to be the highest performing for any one trait, but not necessarily for several traits. The efficiency of selection of extremes is contrasted with the methods of culling levels and tandem selection. It is shown to be superior to culling level selection when the proportion of individuals retained for breeding exceeds 0·5. At higher selection intensities, the effectiveness of selection of extremes falls between that of culling levels and tandem selection.