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Introduction: the objectives were to evaluate estrus and gestation in Bos taurus cows, treated with a fixed-time artificial insemination protocol (FTAI) that included or not equine chorionic gonadotropin (eCG). Cumulative gestation with resynchronization at 30 days after the first FTAI was also evaluated. Method: the cows were divided into: Treatment 1 (n = 60), synchronized with 2 mg of estradiol benzoate and an intravaginal device (IVD) of progesterone (1.3 g) on day 0; IVD was removed on day 8 and 25 mg of prostaglandin F2-alpha, 1 mg of estradiol cypionate and 300 IU of eCG were injected; 48-52 hours later the FTAI was performed. Treatment 2 (n = 50) consisted in the same protocol, not including eCG. Ovulation was resynchronized in cows that were no pregnant in the pregnancy diagnosis, performed 30 days after the first FTAI. The same protocol applied in Treatment 1 for the first FTAI was used in all animals. The second FTAI was performed 40 days after starting the program. Body condition score (BCS) was classified as low (< 2.5), moderate (2.5 to 3.5) and high (> 3.5). On the day of the FTAI, the preovulatory follicle diameter (DFP) was classified into three categories (DFP1: < 11 mm; DFP2: 11 to 14 mm; DFP3: > 14 mm). Results: the gestation percentage was different between treatments (p = 0.04; 73 % Group 1 and 53 % Group 2). The proportion of cows in estrus before the FTAI was 75 % in the eCG treatment and 57 % in the control (p = 0.04). Cows with DFP2 and DFP3 registered a higher gestation rate (p = 0.03) than DFP1. The percentage of pregnancies was higher (p = 0.04) in cows with moderate and high BCS. Overall gestation in the first FTAI was 63 %. The gestation percentage with the second FTAI was 51.61 %, accumulating 82.1 % in 40 days. Conclusion: eCG increased the proportion of cows in estrus and gestation; and resynchronization allows the accumulation of an additional percentage of pregnant cows. [ABSTRACT FROM AUTHOR]

Nonlinear models (NLM) have been used to evaluate dairy cattle lactation curves (LC), and nonlinear mixed models are increasingly applied. The most appropriate model for estimating LC components in Siboney cattle was identified by applying a NLM for LC to 240 d; comparing a non-mixed NML vs a mixed NML; and estimating peak production (PMAX), total production at 240 d (PTOTAL) and days to maximum production (DPMAX). The database consisted of 15,324 records for daily milk production (kg) corresponding to first lactation in 2,809 Siboney cows (calving date in 2000-2012) in 28 herds in Cuba. Five NLM were evaluated: Wood, Wiltmink, Cobby, Brody and Sikka. Two SAS NLMIXED analyses were run: ANA1, including only the random effect of residuals; and ANA2, including a regression coefficient random effect plus residuals. Selection of the best fitting model was done based on average prediction error; prediction error variance; the Durbin Watson statistic; the determination coefficient (R2); the Akaike information criterion (AIC); and the Bayesian information criterion (BIC). The mixed NLM (ANA2) had the best fit: a) its R2 was higher (9 to 12 %); b) residual variance was notably reduced; and c) the AIC and BIC criteria exhibited a better fit. The model with the overall best fit was the ANA2 WOD, with estimates of 7.71 kg for PMAX, 40 d for DPMAX and 1,653 kg for PTOTAL. [ABSTRACT FROM AUTHOR]