Calving month and calf sex on the production and efficiency of herds

Vaz, Ricardo Zambarda; Lobato, José Fernando Piva; Restle, João; Costa, Pablo Tavares; Eloy, Lidiane Raquel; Ferreira, Otoniel Geter Lauz; Costa, João Luiz Benavides

doi:10.1590/1809-6891v21e-61977

Cited by 5 publications

(6 citation statements)

References 18 publications

(28 reference statements)

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“…Under natural pasture and a subtropical climate as in the present study, because the calving season is in the spring, the later the birth, the greater the weight and body condition scores of the cows at calving ( Vaz et al, 2020b ) due to the nutritional improvement that occurs at the end of pregnancy. However, productive variables that express pre-partum performance are less significant for the probability of pregnancy than are variables of post-partum performance ( Pacheco et al, 2022 ).…”

Section: Discussionmentioning

confidence: 83%

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Environmental factors on the probability of pregnancy in early or conventionally weaned beef cows

Vaz,

Lobato,

Bethancourt-Garcia

et al. 2023

Anim. Reprod.

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Potential variables for the reproductive success of beef cows were evaluated. Included in the model were the age of the cow at calving; the interval between the Julian calving date and the end of the breeding season; the body weight and conditions at calving, at 75 days post-partum and at the end of the breeding season; and the mean daily variation in weight between these dates. Logistic regression was used in the analysis, with the parameters evaluated using the odds ratio statistic, estimating the chance of pregnancy. The mean rate of pregnancy was 84% and 55% for early and late-weaned cows, respectively. For early weaned cows, the regression variables were the Julian calving date, age of the cow, weight gain from calving to 75 days post-partum, and from 75 days post-partum to the end of the reproductive period. For late-weaned cows, there were only two regression variables, weight at calving and weight gain from calving to the end of the reproductive period. For every year above the average age of the herd, early weaned cows have an 80.9% greater chance of pregnancy, while a reduction of one year reduces the chance of pregnancy by 44.7%. In early weaned cows, every seven days after the mean Julian calving date reduces the chances of pregnancy by 22.6%, whereas every seven days before the mean calving date increases pregnancy by 29.2%. Greater gains in cow body weight, from calving to the end of the reproductive period, determine a greater probability of pregnancy.

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Section: Discussionmentioning

confidence: 83%

“…An early calving date during the calving season determines greater development and performance in the cows and their calves ( Vaz et al, 2020a , b ; Pacheco et al, 2022 ). Late-calving cows have less time for their body and physiology to recover before the next reproductive period.…”

Section: Discussionmentioning

confidence: 99%

Environmental factors on the probability of pregnancy in early or conventionally weaned beef cows

Vaz,

Lobato,

Bethancourt-Garcia

et al. 2023

Anim. Reprod.

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“…The low phenotypic correlations between AFCo and AFCa with W120 may be attributed to a higher in uence of maternal ability in this growth phase than the environment offered to the calf. Hence, milk production in uences the growth of calves and this live weight is assessment at the age that coincides with the peak lactation of Nellore cattle (Vaz et al 2020). On the other hand, sexual precocity-indicator traits display lower maternal in uence than pre-weaning live weight.…”

Section: Resultsmentioning

confidence: 99%

Effect of age at first conception as selection criteria on growth and carcass traits in Nellore cattle

Brunes

Baldi

Costa

et al. 2022

Preprint

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Despite the economic importance of sexual precocity for beef cattle production systems, in heifers, this indicator is commonly assessed indirectly using the scrotal circumference or with age at first calving (AFCa), which can delay the identification of precocious females. The study aimed to investigate the genetic parameters for age at first conception (AFCo), AFCa, and their relationship with growth and carcass traits, to verify the possibility of using AFCo as selection criteria for the genetic improvement of sexual precocity. The AFCo was considered the age at which the female presented the first positive diagnosis for pregnancy. The estimation of (co)variance components and genetic parameters was performed using a linear animal model in two-trait analyzes. The heritability estimates were moderate. The highest genetic and phenotypic correlation were obtained between AFCo and AFCa (0.88 ± 0.13 and 0.96 ± 0.13, respectively). In general, genetic correlations estimates between sexual precocity-indicator and growth and carcass traits were moderate and negative. The results of this study encourage the use of AFCo in Nellore cattle since this trait displayed enough genetic variability in Nelore cattle, can be used as selection criteria to improve sexual precocity, and would not display an unfavorable effect on other profitability traits. Selection for animals with early ages at first conception and calving would increase the carcass yield, fat deposition and growth performance. When the selection objective is to increase the heifer sexual precocity, we could use the first trait as criterion, as the measurement of this trait occurs at a lower age at first calving.

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“…As baixas correlações fenotípicas entre IPC e IPP com P120 podem ser atribuídas a uma maior influência da habilidade materna nesta fase de crescimento do que o ambiente ofertado ao bezerro. Assim, a produção de leite influencia o crescimento dos bezerros e esse peso corporal é avaliado na idade que coincide com o pico de lactação de bovinos Nelore (46) .…”

Section: Discussionunclassified

Efeito da idade a primeira concepção como critério de seleção em características de crescimento e carcaça em bovinos Nelore

Brunes,

Baldi,

Costa

et al. 2024

Ciênc. anim. bras.

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Resumo Objetivou-se identificar características indicadoras de precocidade sexual de fácil mensuração e que podem ser registradas em menor idade (idade à primeira concepção - IPC), além de estimar as correlações genéticas dessa característica com aquelas de crescimento e carcaça em bovinos Nelore. A IPC foi considerada a idade em que a fêmea apresentou o primeiro diagnóstico positivo de prenhez. A estimativa dos componentes de (co)variância e dos parâmetros genéticos foi realizada usando modelo animal linear em análises bicaracterísticas. As estimativas de herdabilidade foram moderadas, indicando viabilidade de seleção genética para características de crescimento, carcaça e precocidade sexual. As correlações genéticas obtidas entre o IPC e a idade ao primeiro parto (IPP) foram altas (0,88), indicando a viabilidade do uso de IPC como critério de seleção para parto em idade precoce de novilhas. As estimativas de correlações genéticas entre IPC e IPP com peso aos 120, 210, 365 e 450 dias de idade e características de carcaça foram moderadas e negativas (-0,33 a -0,62). Assim, a seleção genética para animais com IPC e IPP precoces aumentaria o rendimento de carcaça, a deposição de gordura e o peso corporal, embora não afete o peso ao nascer e o ganho de peso diário. Os resultados deste estudo encorajam o uso de IPC em bovinos Nelore, uma vez que esta característica apresentou variabilidade genética em bovinos Nelore, podendo ser utilizada como critério de seleção para melhorar a precocidade sexual. Quando o objetivo de seleção genética é aumentar a precocidade sexual das novilhas, indica-se o uso de IPC como critério, pois a mensuração desta característica ocorre em idade menor IPP.

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Calving month and calf sex on the production and efficiency of herds

Cited by 5 publications

References 18 publications

Environmental factors on the probability of pregnancy in early or conventionally weaned beef cows

Environmental factors on the probability of pregnancy in early or conventionally weaned beef cows

Effect of age at first conception as selection criteria on growth and carcass traits in Nellore cattle

Efeito da idade a primeira concepção como critério de seleção em características de crescimento e carcaça em bovinos Nelore

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