Reproductive response of crossbred Bos taurus × Bos indicus cows to biostimulation by pre-pubertal and pubertal teasers.

Although the beneficial effect of biostimulation on reproduction has been reported, the influence of selectivity and social factors on the response to biostimulation has not received sufficient research attention in both Bos indicus and Bos indicus influenced cattle. Furthermore, 'green and cheap' strategies to improve cattle reproduction are currently in demand while Bos indicus influenced cattle with inferior reproductive performance, and farmers with economic limitations are common in tropical zones. Hence, to assess the reproductive response of crossbred taurus × indicus cows to biostimulation by pre-pubertal (PPM) or pubertal (PM) teasers males, two trials of 2 years each were conducted. Trial 1 n = 187 cows (Year 1:85 cows exposed to PPM and Year 2:102 cows exposed to PM). Trial 2 n = 196 cows (Year 1:101 cows exposed to PPM and Year 2:95 cows exposed to PM). The effect of exposing cows to PPM and PM on the intervals calving to first service (ICFS), calving to conception (ICC) and economic cost of days open (ECDO) was analysed using Kruskal-Wallis ANOVA and the effect of exposing cows to PPM and to PM on reproductive status at 90 days (RS90) and proportion of cows requiring hormonal protocols (PRH) was compared using χ2 analysis. Both ICFS and ICC were shorter (p < .0001) for PM-exposed females (96.12 ± 4.1 and 110.93 ± 2.9 days; respectively) compared with those PPM-exposed (134.41 ± 3.3 and 135.64 ± 2.4 days; respectively). With RS90, more (p < .0001) PM-exposed cows (50.7%) were pregnant compared with PPM-exposed cows (16.1%). The PRH was greater (p < .0001) in PPM-exposed cows (79.0%) compared with PM-exposed (27.9%). The ECDO was less (p < .0001) in PM-exposed cows (US$ 142.9 ± 3.8) compared with PPM-exposed (US$ 176.3 ± 2.9). In conclusion, cows exposed to PM had shorter ICFS and ICC compared with cows exposed to PPM. More cows exposed to PM were pregnant after 90 days, and PRH was less than cows exposed to PPM. Cows exposed to PM had a reduced ECDO than those exposed to PPM.

Seasonal variation of the estrous cycle length, corpus luteum area, and size of the pre-ovulatory follicle in Criollo Limonero heifers.

In order to determine whether seasonal variations may influence the estrous cycle length (ECL), corpus luteum size (CLS), maximum area of CL (MACL), day of cycle with maximum area of CL (DCMACL), and pre-ovulatory follicles size (PFS), ten Criollo Limonero heifers were subjected to daily ultrasound ovary scanning throughout their estrous cycles during three seasons: hot-dry (HD), hot-humid (HH), and wind-rain (WR). The effect of season on ECL, MACL, DCMACL, and PFS was analyzed with an ANOVA (PROC GLM, SAS), whereas, for the effect of season on CLS, an ANOVA with repeated measures (PROC MIXED, SAS) was used. Results showed no effect (P > 0.05) of season on ECL, MACL, and DCMACL. However, size of PFS was larger (P < 0.02) during the WR season and the CLS tended (P < 0.09) to be lower during the HH. In conclusion, the relative stability of ECL, MACL, DCMACL, PFS, and CLS measures suggests no major seasonal variations which could imply adaptation capability of Criollo Limonero cattle to the tropical environment.

The effect of bull exposure on the early postpartum reproductive performance of suckling angus cows

El presente estudio examinó el efecto de la bioestimulación por exposición al toro sobre el desempeño reproductivo durante el postparto temprano de vacas Angus bien alimentadas y sujetas a amamantamiento permanente. A una semana postparto, 90 vacas Angus sin historia de problemas al parto y sus becerros fueron distribuidos según el número de partos, peso y talla corporal en 3 grupos aislados de 30 vacas cada uno. Las vacas de los grupos A y B fueron expuestas permanentemente a toros maduros (BE), en tanto que las vacas del grupo C (NE) sirvieron como control. Las variables analizadas fueron: intervalos parto-reanudación de la actividad ovárica (ICR) y parto-primer celo expresado (ICE), longitud del primer ciclo estral (ECL), número de vacas mostrando celo por grupo y número de celos por vaca durante los 90 días previos a la época de monta (NEP). El ICR (38,1 ± 3,4 vs 51,0 ± 4,4; P<0,02) y el ICE (38,1 ± 3,4 vs 59,9 ± 2,5; P<0,001) fueron más cortos en BE que en NE, y no se hallaron diferencias entre grupos expuestos a toro. Más BE reanudaron la ciclicidad ovárica con ciclos normales en comparación con las NE (A=16/53 por ciento, B=16/53 por ciento, C=8/26,6 por ciento; P<0,01). Durante el experimento, más vacas BE mostraron celo que las NE (A: 29/30= 97 por ciento, B: 30/30 =100 por ciento, C: 24/30= 80 por ciento; P<0,002). Así mismo, el NEP observado en vacas BE fue mayor que en las vacas NE (A=70, B=68, y C=42; P<00,002). Más (P< 0,001) vacas BE tuvieron 3 celos durante el estudio. Se concluyó que, aun bajo condiciones de nutrición adecuada y amamantamiento permanente, hubo un efecto bioestimulatorio positivo sobre el desempeño reproductivo temprano de las vacas Angus postparto.

The present study tested the effect of biostimulation by bull exposure on the early postpartum reproductive performance of well fed and permanently suckled Angus cows. At 1 week postpartum, 90 Angus cows with no history of calving problems and their calves were allocated by parity, body weight, and body frame into 3 isolated groups of 30 cows each. Cows from groups A and B were permanently exposed to mature bulls (BE) while cows from Group C (NE) served as a control. Analyzed variables included; intervals from calving to resumption of ovarian activity (ICR), and first behavioral estrus (ICE), length of the first estrous cycle (ECL), number of cows showing estrus/group, and number of estrus periods (NEP) occurred per cow during the 90 days previous to the breeding season. The ICR (38.1 ± 3.4 vs 51.0 ± 4.4; P<0.02) and ICE (38.1 ± 3.4 vs 59.9 ± 2.5; P<0.001) were shorter in BE than in NE cows, and no differences between bull-exposed groups were found. More BE cows resumed reproductive cyclicity with normal ECL than NE cows (A= 16/53%, B=16/53%, C=8/26.6%; P<0.01). During trial, more BE cows showed behavioral estrus than NE cows (A: 29/30= 97%, B: 30/30 =100%, and C: 24/30 = 80%; P<0.002). Similarly, NEP recorded in BE cows was greater than that of NE cows (A=70, B=68, and C=42; P<0.0002). More BE cows (P< 0.001) had 3 estrous periods during trial. It was concluded that, even under conditions involving adequate nutrition and permanent suckling, there was a positive effect of biostimulation on early reproductive performance in postpartum Angus cows.

Effect of ghrelin in dry matter intake and energy metabolism in prepartum sheep: a preliminary study.

The objective of this study was to determine the effect of ghrelin on dry matter intake and energy metabolites in ewes during the last 10d of gestation. Ewes were randomly assigned to either a treatment (n=6) or a control group (n=6). One hour after feeding (08:00 and 16:00), ewes in the treated group were given ovine ghrelin (3 microg/kg, i.m.) and the control group received an equivalent volume of saline. Treatments were continued until lambing. Daily blood samples were taken starting at assignment. The principal findings were that: (1) ewes treated with ghrelin had a higher dry matter intake only on the first day of treatment; (2) treated ewes had lower serum concentrations of non-esterified fatty acids and insulin but higher serum concentrations of growth hormone; (3) serum concentrations of beta-hydroxy butyrate and cortisol were not different between treated and non-treated ewes. In conclusion, treatment with ghrelin affected dry matter intake and energy metabolites of pre-partum ewes during the last 10 d of pregnancy.

Effect of administration of a controlled-release monensin capsule on incidence of calving-related disorders, fertility, and milk yield in dairy cows.

OBJECTIVE: To determine the effect of a controlled-release monensin capsule administered at cessation of lactation on incidence of calving-related disorders, fertility, and milk yield in dairy cows. ANIMALS: 290 dairy cows treated with monensin and 290 untreated control cows. PROCEDURE: Treated cows received a capsule that released monensin at 335 mg/d for 95 days. Incidence of calving-related disorders; daily milk yield up to 20 days postpartum; test-day milk yield, fat, protein, and mature-equivalent 305-day milk production; and body condition score at calving were determined. Reproductive variables were conception rate at first service, pregnancy rate, and calving-to-conception interval. RESULTS: Cows treated with monensin were 2.1 times as likely to develop dystocia and 0.8 times as likely to develop metritis as control cows. For milk yield, there was an interaction of treatment X time X parity. In multiparous cows, monensin significantly improved milk yield at test days 4 and 7. In addition, monensin increased body condition score at calving. CONCLUSIONS AND CLINICAL RELEVANCE: Despite increasing the likelihood of developing dystocia and metritis, administration of monensin improved the lactational performance of multiparous cows and may be a promising additive for use at the time of cessation of lactation.