Paper Title
The Effect of Lactation Number and Calving Season on The Numbers of Services Per Conception in Holstein Crossbreed Dairy Cattle

The aim of this study was to determine the effect of calving season (CS) and lactation number (LN) on the number of services per conception (NSC) in Holstein crossbreed dairy cattle. The NSC is an important parameter for herd fertility, because it may cause huge economic losses for the farm. Data used in the current study were obtained from a commercial dairy farm in Kırşehir province in Turkey. The CS and NSC data from 115 cow were used for analysis. Number of animals were 115 for 1st, 2nd and 3rd lactations, 41 for 4th and 16 for 5th lactation. Calving seasonis divided into 1st (December, January, and February), 2nd (March, April, and May), 3rd (June, July, and August) and 4th (September, October, and November) seasons. One-way analysis of variance (ANOVA) and Duncan test were used for statistical analysis. There was a significant difference between 4th and 5th LN. There wasn't any difference between the other groups. The 5th (2,00±0,33), 1st (2,23±0,12), 2nd (2,37±0,13), 3rd (2,60±0,14) and 4th (2,76±0,26) lactation means were ranked from minimum to maximum in terms of NSC, respectively. Shortly, NSC increases as LN increases but this correlation was not significant. It is believed that difference between 4th and 5th lactations were caused by the difference innumbers of animals evaluated. The 1st season was significantly different from the 2nd and 4th seasons. There was not any difference between the other seasons. The 1st (2,07±0,13), 3rd (2,43±0,12), 2nd (2,56±0,19) and 4th (2,63±0,14) calving seasons were ranked from minimum to maximum in terms of NSC, respectively. The NSC found lowest in the winter season. According to the results, it was found that NSC can be affected by LN and CS. Keywords - Lactation number, Calving season, Number of services per conception