Genetic parameters and correlations for lactation milk yields according to lactation numbers in jersey cows

Bu çalışmada, Karaköy Tarım İşletmesi Jersey sığır sürüsünde 1984-2007 yılları arasında doğum yapmış inekten elde edilen 3630 adet 305 günlük süt verim kayıtları kullanılmış ve süt verimlerine ait kalıtım dereceleri ile laktasyon sıraları arasındaki genetik ve fenotipik korelasyonlar tahmin edilmiştir. Verilerin istatistik analizinde, buzağılama yılı, buzağılama ayı ve laktasyon sırası sabit etkili faktörler olarak alınmıştır. Kalıtım dereceleri ile genetik ve fenotipik korelasyonlar hayvan modeli altında derivative-free REML yöntemi kullanılarak tahmin edilmiştir. Analizler, 305-günlük süt verimi, laktasyon süresi, kuruda kalma süresi ve buzağılama aralığı ortalamalarının sırasıyla 3476 kg, 297 gün, 70 gün ve 367 gün olduğunu göstermiştir. Varyans analizi sonuçları, ele alınan tüm sabit etkili faktörlerin süt verimleri üzerinde istatistiksel olarak önemli olduğunu göstermiştir (P

Anahtar Kelimeler:

laktasyon süresi, kalıtsallık, genetik parametreler, genetik korelasyon, kuru dönem, süt ineği, sığır ırkları, inek, Jersey, fenotipik korelasyon, buzağılama aralığı, süt sığırı, sığır, süt verimi, süt üretimi, laktasyon dönemi

Jersey ineklerde laktasyon sıralarına göre laktasyon süt verimleri İçin genetik parametreler ve korelasyonlar

In this study, heritabilities, genetic and phenotypic correlations for lactation milk yields were estimated using 3630 305-day lactation milk yield records obtained from cows calved from 1984 to 2007 years in Jersey cattle herd of Karaköy Agricultural State Farm in Samsun. Calving year, calving month and lactation number were assumed as fixed effect factors in statistical analysis of data. Heritabilities, genetic and phenotypic correlations were estimated by derivative-free REML with the animal model. Analysis showed that the overall means of 305-day milk yield, lactation length, dry off period and calving interval were 3467 kg, 297 days, 70 days and 367 days, respectively. Variance analysis results showed that all of the fixed effect factors were statistically significant on lactation milk yields (P<0.001). REML estimates of heritability were 0.289, 0.319, 0.324, 0.331, 0.339, 0.357 and 0.379 for lactation milk yields (from the first to seventh lactation numbers, respectively). Genetic correlations among the first and sub-sequent lactation milk yields were 0.687, 0.676, 0.631, 0.601, 0.590 and 0.551, respectively. All genetic correlations were high and statistically significant (P<0.01). High genetic correlations among lactation numbers reflected that the first lactation milk yield of cows would be useful indicator for the sub-sequent lactations and selection of breeding stock.

Keywords:

lactation duration, heritability, genetic parameters, genetic correlation, dry period, dairy cows, cattle breeds, cows, Jersey, phenotypic correlation, calving interval, dairy cattle, cattle, milk yield, milk production, lactation stage,

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