This study was conducted to identify gene polymorphisms and to investigate the relationships of polymorphisms with yield and composition of milk from Holstein cows. Significant relationships of growth hormone (GH), leptin (LEP) and myogenic factor 5 (MYF5) gene polymorphisms with 305‐day milk yield were observed (P < 0.01). Signal transducers and activators of transcription 5A (STAT5A) gene polymorphism did not show any significant relationships with investigated traits (P > 0.05). With regard to the 305‐day milk yield, GH‐LV, LEP‐AA and AB and MYF5‐GG genotypes were found to be superior over the other genotypes. It was concluded based on present findings that GH, LEP and MYF5 genes could be used as candidate genes for milk yield of Holstein cows.

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Purpose of this study was to investigate the relations of dry period lengths (DPL) with subsequent lactation (305-d) milk yield (MY) and reproductive performance of Holstein cattle. Data were obtained from 800 Holstein cows raised in a private dairy operation and which were in different parity (2 nd , 3 rd and ≥4 th). DPL was classified in 5 categories as; ≤40, 41-50, 51-60, 61-70 and ≥71 days. The differences in lactation milk yields of experimental DPL groups were not significant. The highest MY (7808.6±135.1 Lt) was obtained from ≥71 days DPL group and the lowest MY (7529.4±159.8 Lt) was obtained from ≤40 days DPL group. DPL had significant effect on the number of inseminations resulted in pregnancy (P<0.01). The greatest pregnancy ratio (53.0%) in the first insemination was obtained from ≤40 days DPL group and the lowest pregnancy ratio (30.8%) was obtained from 61-70 days dry period group. There was a positive correlation (0.056) between DPL and 305-d MY and a highly significant positive correlation (0.141) between DPL and the number of insemination resulted in pregnancy. Present findings revealed that longer DPL might have positive effects on lactation MY, but shorter DPL practices might have better outcomes for pregnancy ratios of the first insemination for this farm.

Live weight and body measurements are economically important quantitative traits that affect carcass yield and calf survival in cattle. Four genes, growth hormone gene (GH), myogenic factor 5 (MYF5), fatty acid binding protein 4 (FABP4) and signal transducers and activators of transcription 5A (STAT5A) were chosen as candidate genes for live weight and body measurements due to their important role in growth. The aims of this study were to genotype GH-AluI, MYF5-TaqI, FABP4-HinII and STAT5A-AvaI polymorphisms and to investigate their associations with live weights and body measurements in Holstein young bulls. Genotyping of the single nucleotide polymorphism (SNP) markers in these candidate genes was carried out using the restriction fragment length polymorphism (RFLP) analysis. Frequencies of L allele for GH, A allele for MYF5, G allele for FABP4 and C allele for STAT5A were, 0.96, 0.61, 0.79 and 0.74, respectively in the examined animals. The regression analysis indicated that the GH-AluI polymorphism showed an association with weaning weight (WW), 180 th day weight and hearth girth from birth to 180 days of age. The MYF5-TaqI polymorphism was found to influence body length at birth and birth weight (BW). However, no significant association was detected between the FABP4-HinII genotypes and measured traits. The GH-AluI and MYF5-TaqI polymorphisms may be useful for selection on live weight and body measurement traits in Holstein young bulls.

This study was conducted to investigate the effects of dry period length (DPL) on survival rate, gender, growth performance, mortality of Holstein calves. Data belonged to 800 Holstein cows in different parities (2nd, 3rd and ≥4th) and 800 calves delivered by these cows. DPL were classified in 5 categories (≤40, 41-50, 51-60, 61-70, ≥71 days). Calves were weighed and body dimensions (body length, wither height, hearth girth) at birth and 6th months of age. There were significant relationships between DPL and calf gender (P

Bu çalışma entansif bir süt sığırcılığı işletmesinde bulunan Holstein ineklerde memenin fenotipik özellikleri ile somatik hücre sayısı (SHS) arasındaki ilişkiyi incelemek amacıyla yapılmıştır. Çalışmada ineklerde meme fenotipik ölçüleri alınmış ve inekler GrupI (ideal meme özelliğinde olanlar) ve GrupII (ideal meme özelliğinde olmayanlar) şeklinde sınıflandırılmıştır. Meme özellikleri ile SHS, SHS ile süt verimi ve süt kompozisyonu arasındaki ilişkiye bakılmıştır. Ayrıca her bir grupta laktasyon sırası (1,2,3,4), laktasyon dönemi (1,2,3) ve kontrol haftalarının (1,2..,10) etkisi istatistiki olarak incelenmiştir. SHS üzerinde grup (P<0.01), laktasyon sırası (P<0.05), laktasyon dönemi (P<0.01) ve kontrol haftası etkisi (P<0.05) istatistiki olarak önemli bulunmuş, interaksiyonlar önemli olmamıştır. GrupI' de somatik hücre sayısı 5.04±0.09 Log 10 SHS adet ml-1 ve GrupII' de 5.35±0.08 Log 10 SHS adet ml-1 olarak belirlenmiştir. Süt verimi, pH ve iletkenlik özelliklerinde grup etkisi önemli (P<0.01) bulunmuştur. Grup I ve Grup II için bu değerler sırasıyla; süt veriminde 34.79±0.91 lt gün-1 ve 30.15±0.81 lt gün-1 , pH' ta 6.96±0.02 ve 7.02±0.01, iletkenlikte 5.59±0.26 ve 6.84±0.23 olarak belirlenmiştir. Ayrıca korelasyon değerlerine bakılmış SHS ile süt verimi arasında-0.258 değerinde önemli negatif yüksek korelasyon ve SHS ile pH ve SHS ile iletkenlik arasında sırasıyla +0.552 ve +0.278 önemli pozitif yüksek korelasyon tespit edilmiştir. Elde edilen sonuçlar üretilen sütün kalitesini arttırmak için memenin fenotipik özelliklerinin dikkate alınması gerektiğini, fenotipik olarak ideal olmayan memelerin süt kalitesini olumsuz yönde etkilediğini ortaya koymuştur.

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