Portal de Pesquisa da BVS Veterinária

Tese em Inglês | VETTESES | ID: vtt-201452

Resumo

The objective of this study was to determine risk-factors affecting increase in physical activity during estrus and pregnancy per AI (P/AI) in lactating dairy cows. Cows were monitored continuously by two automated activity monitors (a collar-mounted accelerometer [Heatime, SCR Engineers; HT] and a leg-mounted pedometer [Boumatic Heat-seeker-TX; BO]). When an increase in activity was detected, body condition score (BCS) and blood samples were collected, ovaries were scanned by ultrasonography and, if the cow was eligible for breeding, AI was performed. Milk production and healthrelated data were recorded throughout the experimental period. Pregnancy diagnosis was performed at 42 ± 7 d of gestation. Data was analyzed using Pearsons correlation, ANOVA and logistic regression with SAS. A total of 1,099 true events of estrus from 318 lactating Holstein cows were recorded, averaging 3.46 ± 1.1 events per cow. Positive predictive value (PPV) for estrus episodes detected by the HT and BO systems were 89.6% and 85.5%, respectively. Mean peak activity at estrus (PA) recorded by the HT system was 71.6 ± 20.7 index-value, and 334.3 ± 155.7% relative increase by the BO system. Compared to primiparous, multiparous cows expressed estrus with lower PA (69.3 ± 0.8 vs. 75.9 ± 1.1 [HT]; 323.9 ± 6.0 vs. 354.8 ± 8.48 [BO]) and shorter duration (DU; 10.7 ± 0.2 vs. 12.0 ± 0.3); DU was measured by HT only. Lower BCS was associated with decreased PA measured by both systems, estrus DU and P/AI. Peak activity was weakly correlated with milk production on the day of AI (r = -0.20), however, when categorized into quartiles, the highest yield cows had lower PA and DU. Follicle diameter was not correlated with PA or DU, but cows with greater concentrations of estradiol had higher PA. Cows with greater PA in both systems had greater P/AI than those with lower PA (36.5 vs. 24.6% [HT], 33.5 vs. 21.4% [BO]). In conclusion, measurements of estrus events captured by AAM are correlated with BCS, parity and secondary behavior signs related to estrus. Surprisingly, estrus intensity and duration were only weakly correlated with milk production, pre-ovulatory follicle diameter and concentrations of estradiol at estrus. Cows that had measurements of high intensity estrus were significantly more fertile than low intensity estrus.

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The objective of this study was to determine risk-factors affecting increase in physical activity during estrus and pregnancy per AI (P/AI) in lactating dairy cows. Cows were monitored continuously by two automated activity monitors (a collar-mounted accelerometer [Heatime, SCR Engineers; HT] and a leg-mounted pedometer [Boumatic Heat-seeker-TX; BO]). When an increase in activity was detected, body condition score (BCS) and blood samples were collected, ovaries were scanned by ultrasonography and, if the cow was eligible for breeding, AI was performed. Milk production and healthrelated data were recorded throughout the experimental period. Pregnancy diagnosis was performed at 42 ± 7 d of gestation. Data was analyzed using Pearsons correlation, ANOVA and logistic regression with SAS. A total of 1,099 true events of estrus from 318 lactating Holstein cows were recorded, averaging 3.46 ± 1.1 events per cow. Positive predictive value (PPV) for estrus episodes detected by the HT and BO systems were 89.6% and 85.5%, respectively. Mean peak activity at estrus (PA) recorded by the HT system was 71.6 ± 20.7 index-value, and 334.3 ± 155.7% relative increase by the BO system. Compared to primiparous, multiparous cows expressed estrus with lower PA (69.3 ± 0.8 vs. 75.9 ± 1.1 [HT]; 323.9 ± 6.0 vs. 354.8 ± 8.48 [BO]) and shorter duration (DU; 10.7 ± 0.2 vs. 12.0 ± 0.3); DU was measured by HT only. Lower BCS was associated with decreased PA measured by both systems, estrus DU and P/AI. Peak activity was weakly correlated with milk production on the day of AI (r = -0.20), however, when categorized into quartiles, the highest yield cows had lower PA and DU. Follicle diameter was not correlated with PA or DU, but cows with greater concentrations of estradiol had higher PA. Cows with greater PA in both systems had greater P/AI than those with lower PA (36.5 vs. 24.6% [HT], 33.5 vs. 21.4% [BO]). In conclusion, measurements of estrus events captured by AAM are correlated with BCS, parity and secondary behavior signs related to estrus. Surprisingly, estrus intensity and duration were only weakly correlated with milk production, pre-ovulatory follicle diameter and concentrations of estradiol at estrus. Cows that had measurements of high intensity estrus were significantly more fertile than low intensity estrus.

Biblioteca responsável: BR68.1