Phenotypic relationships between type traits and productive life using a piecewise Weibull proportional hazard model

Abstract

Longevity is an important trait due to its relationship with profitability. Type traits have been used as indirect predictors for productive life. The objective of this study was to evaluate the relationship of 20 type traits on length of productive life in Brazilian Holsteins, using a piecewise Weibull proportional hazard model. Three analyses were performed i) productive life was corrected for within herd level of production as a proxy for functional longevity, which included the time-dependent effects of region within year, class of milk production within herdyear, milk production class within lactation number, fat class and protein contents within herd and (variation in) herd size as well as the time-independent fixed effect of age at first calving and the type trait score; ii) the effects related to production were omitted from the first model (true longevity) and iii) with the first model, the effect of type was also studied considering five classes of percentage of type-scored cows within the herd. All analyses were performed using the Survival Kit program. The final score, angularity, top line, udder texture and suspensory ligament showed the strongest relationship with productive life. When type traits were available only for a small fraction of the herd, the cows had a better chance of remaining longer in the herd. The absence of type trait phenotypes was associated with a strong increase of culling risk for the cows. Type traits were not found to be good indirect predictors of productive life in Brazil.Length of productive life and type traits records were obtained from the Brazilian Association of Holstein Cattle Breeders (ABCBRH) and its affiliated state agencies. Two longevity traits were defined as in Ducrocq et al. (1988): true longevity, measured as the number of days from first calving to culling, and functional longevity, approximated by correcting true longevity for within-herd-year level of production.

Caracterização fenotípica de vacas F1 Holandês x Zebu de diferentes bases maternas

“…3; P>0,05), ângulos de garupa e de perna que se enquadram no escore intermediário (World..., 2016). Esses valores são considerados ideais, pois diminuem a probabilidade de descarte involuntário das fêmeas (Kern et al, 2018). Como as vacas F1 Holandês x Gir têm a menor estrutura corporal entre as fêmeas das demais bases maternas, também foram 48,0kg mais leves (P<0,05; peso na balança) do que as F1 que possuem genes da raça Nelore (Tab.…”

“…Apesar de as vacas F1 portadoras de genes da raça Nelore apresentarem menores valores (P<0,05) em comprimento de tetos (Tab. 4), estes se encontravam dentro dos valores aceitáveis para a raça Girolando, que é de 5 a 7cm de comprimento (Silva et al, 2018 De acordo com Kern et al (2018), as características do sistema mamário são as que mais influenciam a produção de leite e a permanência do animal no rebanho. Valores intermediários para profundidade do úbere, comprimento de tetos e distância entre eles refletem a menor suscetibilidade à mastite e a outras doenças infecciosas (Sewalem et al, 2004).…”

“…A avaliação fenotípica do animal por meio de mensurações quantitativas é mais objetiva, pois há pouca influência do avaliador (Essien e Adesope, 2003). Essas características são associadas às características funcionais dos animais, como resistência a doenças (Campos et al, 2012), adaptação do animal ao ambiente (Cardoso et al, 2015), produção de leite e permanência no rebanho (Kern et al, 2018).…”

Evaluation of Models for Longevity in a Closed Nucleus Breeding Programme: A Case Study Kenyan Sahiwal

“…Therefore, since productive longevity is closely related to fertility, it is important to consider the genetic effects of both traits simultaneously. Other traits which influence culling decisions such as body conformation type traits have also been considered as proxy for longevity [4] [12]. Despite its importance in cattle, longevity has not been studied in the Sahiwal cattle and has not been recommended for inclusion in the breed's breeding objective [13] [14] [15].…”

“…Favorable associations between longevity and linear type traits have been reported, indicating selecting for these traits would improve longevity [4]. Based on phenotypic relationships, [12] found those type traits were not a good indirect indicator for a productive life.…”