Influence of estrus on rumination, activity, feed and water intake of dairy cows
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The detection of estrus is one of the major factors affecting the reproductive performance of dairy cows, especially in farms using AI. Failure to detect estrous behaviors and false positive results leads to missed inseminations and, thus, economic losses. Technical methods providing detailed information and continuous monitoring of the individual cow have been developed to support herd managers in determining the onset of estrus. Whereas increased activity behavior is regarded as indicative of estrus, little to nothing is known about the effect of estrus on daily rumination or feed and water consumption. The overall objective of the studies presented in this thesis was to investigate whether these traits were associated with estrus in dairy cattle. To ensure true estrus, only estruses leading to conception after AI were included in the investigations. Values of the estrous day (d 0) were compared with the reference period defined as the mean of 3 days prior and 3 days post d 0. Recording of data in 2-h time intervals provided information on circadian rhythms. For measurement of individual RT, cows of five commercial farms were equipped with the HR-Tag monitoring system (SCR Engineers Ltd., Netanya, Israel) containing a microphone attached to the neck collar of each cow. In study 1, it was found for the first time that RT was - with large inter-individual variation - significantly influenced by cow s estrus as animals spent less time ruminating on d 0 relative to the base level during the reference period (374 versus 442 min). Rumination time decreased gradually starting two days before the onset of estrus. The minimum level was identified on d 0, after which RT returned to base level again. As RT is closely linked to feeding characteristics, these results predicted that further feeding characteristics may also be reduced at estrus. Hence, study 2 carried out on a research farm focused on cow s feed and water consumption which were automatically measured by troughs placed on an electronic floor scale. Indeed, with a decline of on average 14.6%, most cows (85%) consumed 70 significantly less dry matter of the forage ration - CI was not affected by estrus - during estrus in comparison to non-estrous days (20.4 versus 23.0 kg). Similarly, estrual cows drank less water. WI was reduced by 15.3% in 67% of all cows, with the lowest value determined on the day before estrus relative to the reference period. Consequently, BW recorded by a walk-through scale showed lower values in 69% of the animals at estrus, reflecting the decrease in rumen content caused by reduced DMI and WI. Simultaneous analysis of RT and activity behavior in study 3 verified our hypothesis of a direct relationship between the alterations in these traits. Monitoring of activity was performed by a collar-mounted system that continuously measures estrus-related accelerations resulting from upward movements of the head and neck during walking and mounting. With no difference between Holstein and Simmental cows activity enhanced on average by 38.7%. On d 1 activity declined to base level again, concomitant with the increase in RT. The percentage of estrual cows with increased activity was lower than of those with shorter RT (76.5 versus 86.2%). Both RT and activity behavior during estrus were correlated with parity as well as average daily milk yield. Changes during estrus were more pronounced in primiparous cows than in multiparous herd mates. Additionally, study 3 revealed that cows with a daily milk yield > 40 kg exhibited the greatest decline in time spent ruminating compared to those with a production ≤ 40 kg per day. A weak trend for a less pronounced activity increase was detected in high-yielding cows. The circadian rhythms of RT and activity behavior were bimodal. Activity behavior was found to be decreased in the afternoon and during nocturnal hours in the reference period when cows spent most time ruminating. Cows expressed highest activity and lowest RT between 0200 and 0800 and 0400 and 1000 h on the day of estrus. In conclusion, previously unknown as being indicative for estrus, rumination was found to be significantly reduced at the onset of cow s estrus. Furthermore, feed and water 71 consumption as well as BW were markedly decreased by estrus, whereas activity behavior measured by collar-mounted acceleration technology was significantly increased. Comprehensive knowledge of the behavioral characteristics of cow s estrus is essential to recognize cows in estrus. The results of the presented studies give rise to further research including the development of algorithms to determine how the analyzed traits may support herd managers in detecting estrual animals and, thus, to improve daily reproductive management.Verknüpfung zu Publikationen oder weiteren Datensätzen
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Giessen : VVB Laufersweiler Verlag