Conception Rate

The purpose of this study was to investigate the relationship between conception rate (CR) and climate variables. Data consisted of 24,380 inseminations of Holstein dairy herd in Hidalgo, Mexico. Weather records, including daily temperature (T), relative humidity (RH), rainfall, wind speed, and solar radiation, were obtained from a nearby weather station. Means for each climatic variable from 2 days before artificial insemination (AI) to the AI day were calculated for each conception date represented in the study. A significant negative correlation was observed between the CR and mean and minimum T, mean and minimum RH, mean and minimum temperature–humidity index (THI), and rainfall. The overall mean CR was 34.3%. The CR in lactating dairy cows followed a seasonal pattern, lower CRs were observed in summer months than during winter (32.1% vs. 36.9%; P < 0.01). The variables that had the greatest influence on CR were minimum and maximum T, minimum RH, minimum THI, wind speed, and ...

Effects of Dorset, Finnsheep, Romanov, Texel, and Montadale breeds for performance as sires were estimated in the initial phase of a comprehensive evaluation of these breeds as contributors to sheep crossbreeding systems. Objectives were to evaluate the effects of ram breed, ewe breed, season of mating, and two-way interactions. Rams from the five breeds were single-sire-mated with ewes from two breed types to produce lambs over a 3-yr period. Ewes were assigned to one of three distinct 35-d mating seasons initiated each year in August, October, and December. A different sample of six rams per breed was used each year across all three seasons, and each ram was penned with ewes of both breeds. Traits evaluated and number of ewe records were conception rate and litter weaning weight per ewe exposed (n = 3,261) and number born, litter birth weight, average birth weight, number weaned, and litter weaning weight per ewe lambing (n = 2,751). Ram breed and ewe breed interacted (P < .01)...

Our objective was to determine whether progesterone (P4) supplementation during an Ovsynch protocol would enhance fertility in lactating dairy cows. Lactating dairy cows (n = 634) at 6 locations were assigned randomly within lactation number and stage of lactation to receive the Ovsynch protocol [OVS; synchronization of ovulation by injecting GnRH 7 d before and 48 h after PGF(2alpha), followed by one fixed-time AI (TAI) 16 to 20 h after the second GnRH injection] or Ovsynch plus a controlled internal drug release (CIDR) P4-releasing insert for 7 d, beginning at the first GnRH injection (OVS + CIDR). Blood was sampled to quantify P4 10 d before the first GnRH injection, immediately before the first GnRH injection, at the time of CIDR removal, before the PGF(2alpha) injection (1 to 2 h after CIDR insert removal), and 48 h after the PGF(2alpha) injection to determine cyclicity status before initiation of treatment, luteal status at the PGF(2alpha) injection, and incidence of luteal re...

Seasonal patterns in conception rates have been documented in several recent studies. In this paper, a mathematical model of the reproductive process is developed through which the impact of such variation in conception rates is assessed. It is found that the effect on fertility can be quite substantial, but that the birth rate when seasonal variation is occurring is approximated well by the birth rate calculated when conception rates are constant at their mean. These results indicate that further documentation of seasonality in conception rates and exploration of the causes of these patterns and their change is an important area for demographic research.

In order to determine some physiological responses 60 d prepartum and production responses postpartum to a cooling system in summer, 24 multiparous Holstein cows were allocated to two groups: one group with (n=12) and a second group without (n=12) cooling. Cooled cows showed a lower (P 0.05). Reproductively, only total conception rate was higher (P<0.05) in cooled cows than in non-cooled cows (100 vs 63.6 %). Non-cooled cows showed a 42 % culling rate, while no cow was culled in the cooled group (P<0.05). An economic analysis showed a net profit of 75 dollars cow/year for the cooling system. Results show that cooling dry cows reduce heat stress, that resulted in higher fat-corrected milk and milk fat production in the subsequent lactation and in higher economical benefits for dairy producers.

The efficacy of two programs for treating noncyclic cows was compared. In trial 1, 478 cows in five herds were randomly divided into two groups. Cows in one group (C group) were treated with an intravaginal progesterone device for 8 d followed in 48 h by 1 mg of estradiol benzoate to cows that had not been detected in estrus since device removal. Those in the other group (CGP group) were treated with progesterone and estradiol as for the C group plus 10 micrograms of a GnRH agonist (buserelin) at device insertion and 25 mg of PGF2 alpha 7 d after device insertion. In trial 2 with 729 cows in nine herds, the treatments were similar to those in trial 1 except that the duration of progesterone treatment was 7 d. No significant difference was found between trials and results from both trials were combined. Compared with C group cows, CGP group cows had a greater estrous response rate (93.2 vs. 89.1%), a greater conception rate to first artificial insemination (AI, 47.1 vs. 29.4%), margi...

Avaliou-se a relação entre os testes complementares (teste hiposmótico, teste de termorresistência lento e teste de reação acrossômica) e os testes de avaliações convencionais (aspectos físicos e morfológicos) de sêmen bovino congelado/descongelado e os índices de prenhez. Os valores médios da motilidade espermática progressiva retilínea avaliados pelo teste de termorresistência foram de 53,48 (pós-descongelamento), 43,69 (60 minutos), 35,88 (120 minutos) e 33,04% (180 minutos) e a porcentagem de células reativas ao teste hiposmótico foi de 37,89%. Correlação positiva e de média intensidade foi encontrada para a motilidade espermática progressiva retilínea pós-descongelamento e o teste hiposmótico (0,21). Entretanto, a correlação da motilidade aos 180 minutos com o teste hiposmótico foi alta (0,64). A porcentagem de células que tiveram acrossoma reagido pós-descongelamento foi de 9,85%, apresentando correlações negativas de média e alta intensidade (-0,25 e -0,46, respectivamente) c...

In this study GnRH and propylene glycol respectively used as hormonal treatment and to supply precursor material of glucose. Animals (56 crossbred ewes, Arkhamerino-Ghezel (AG) and Arkhamerino-Moghani (AM), 2.5 years old) were classified to 1 control and 3 treatment groups randomly. After estrus detection and before mating; one milliliter of physiological saline (0.9% NaCl, placebo) was administered to each ewe in control group, group 1 were injected with 2.5 ml GnRH and after 2 hours they were mated by ram; group 2 were injected with 5 ml GnRH 12 days after mating; group 3 were received 30 ml propylene glycol for 5 days after mating. Blood samples were taken on 6 d after mating by using vacuum tube. Glucose, urea, phosphorus, total protein, β-hydroxybutyrate (BHBA) and progesterone concentrations in blood serum were measured. Results shows that glucose in AM was significantly higher than AG (P<0.01). Urea and BHBA in AM were significantly (P<0.01) lower than AG. In repeat breeder ewes, progesterone concentration in estrus 2 was significantly (P<0.05) higher than estrus 1, and urea and BHBA concentrations in estrus 2 were significantly (P<0.05) lower than estrus 1. Administration 5 ml of GnRH on day-12 after mating was effective on reproductive performance than others. In conclusion, results showed that only one sheep in GnRH-2.5 ml treatment at estrus and five sheep in GnRH-5 ml on day-12 after mating showed repeat estrus and suggested that using 2.5 ml of GnRH before mating had better effect to prevent of repeat breeder .

The effect of husband&amp;#39;s age on the probability of conception is evaluated from World Fertility Survey data in five developing countries: the Ivory Coast, Ghana Kenya, the Sudan, and Syria. Proportional hazards models, which include wife&amp;#39;s age, husband&amp;#39;s age, marriage duration, union type, and post-partum exposure as covariates, are used to describe the monthly conception rate for second and higher-order birth intervals in which no contraception was used. With the exception of Syria, the resulting models indicate that the effects of male age are generally small in relation to the influences of marital duration and the age of the woman.

The objective was to determine the efficacy of a previously used CIDR or melengestrol acetate (MGA; 0.5mg/head/day) for resynchronization of estrus in beef heifers not pregnant to timed-AI (TAI). In three experiments and a field trial, heifers were reinseminated 6–12h after first detection of estrus. Pregnancy diagnosis was done from approximately 25–43 days after either TAI or reinsemination. In Experiment