Brunstvisningsförmåga hos SRB- och Holsteinkvigor

Sammanfattning: Oestrus in dairy cattle has changed over the last decades, the duration has decreased and the intensity of oestrus has declined. A possible explanation can be their high and increasing milk production. Heifers ability to show oestrus is probably not affected to the same extent. The aim of this study was to estimate and compare oestrus duration and strength in heifers of the Swedish Red and Holstein breeds. Standing oestrus has been the primary oestrus sign during many years. It is important to look for other signs than standing oestrus to get a high conception rate, since the standing oestrus length has decreased and some animals does not even show standing oestrus. The material in this study was collected at Jälla Naturbruksgymnasium in Uppsala between 2010-10-11 and 2010-12-13. It consisted of 20 heifers, 9 Swedish Red breed (45%) and 11 Holstein (55%). The data was analyzed by the SAS program and Microsoft Excel. The starting-point of the oestrus was a visual oestrus confirmed by a progesterone sample with a value < 8.0 nmol/L. The heifers had a mean estrous cycle length of 20 days with an SD of 2.4 days, with a variation of 14-25 days. The mean value for SRB was 19.4 days with an SD of 2.5 days and the mean value for Holstein was 20.5 days with an SD of 2.3 days. The mean estrous cycle length is this study corresponds to a study of Holstein heifers by Diskin & Sreenan, (2000) and a study of SRB heifers by Båge et al. (2002). The oestrus length was somewhat shorter than the results for Holstein cows and heifer in Sartori et al. (2004). A total of 70 progesterone oestruses within normal oestrus cycle length was confirmed by a progesterone sample, 65 of those had a notation of a visual oestrus sign in the protocol i.e. 92.8 % detection efficiency. The heifers showed standing oestrus in 49.2 % of the oestruses. In 42 (65%) of the 65 oestrus periods blood discharge from the vulva was discovered. The mean length between standing oestrus and blood discharge was 59 hours with an SD of 27 hours. SRB had a mean oestrus length of 55 hours with a SD of 33 hours and Holstein had a mean length of 65 hours with a SD of 22 hours. The mean oestrus length was 52 hours with a SD of 32 hours. The variation was 24-110 hours. Swedish Red (53 ± 33) and Holstein (55 ± 32) was found to have similar mean oestrus length, Holstein somewhat longer. Our result is comparable to a study by Båge et al. (2002), despite 8 years between the studies. Higher proportion of Swedish Red was estimated to have normal oestrus strength, while a similar share showed strong oestrus strength. Holstein had the highest percentage of very strong oestrus strength. That Holstein showed similar oestrus length and stronger oestrus strength than Swedish Red is an interesting result. Oestrus in cows from these two breeds has been compared in previous studies and SRB seems to have longer and stronger oestrus. This is to our knowledge the first study that compares oestrus in SRB and Holstein heifers in the same study. The number of heifers in this study was relatively low and it would be interesting to see if these differences between breeds would consist in a larger material.