Water requirements of beef production can be reduced by genetic selection.

Growing concerns regarding sustainability in agriculture include the availability of drinking water, which is putting pressure on livestock production, especially the beef sector, for more efficient practices. Thus, genetic parameters were estimated for traits related to water intake and water use efficiency in Senepol cattle. Senepol females (n = 925) and males (n = 191) were evaluated in performance tests carried out from 2014 to 2019. Daily dry matter intake (DMI) and water intake (WI) were recorded by electronic feed and water bunks (Intergado Ltd.). Other traits assessed included average daily gain (ADG); mid-test metabolic BW (BW0.75); residual water intake based on ADG (RWIADG), estimated as the residual of the linear regression equation of WI on ADG and BW0.75; residual water intake based on DMI (RWIDMI), estimated as the residual of the linear regression equation of WI on DMI and BW0.75 (RWIDMI); water conversion ratio (= WI/ADG); gross water efficiency (GWE = ADG/WI); residual feed intake estimated as the residual of the linear regression equation of DMI on ADG and BW0.75 (RFI); feed conversion ratio (= DMI/ADG) and gross feed efficiency. Genetic (co)variances were estimated with bivariate analyses. The heritabilities for WI, RWIADG and RWIDMI were 0.38, 0.36 and 0.33, respectively. Water conversion ratio, RWIADG and RWIDMI showed positive genetic and phenotypic correlations with WI, whereas GWE was negatively correlated with WI, suggesting that traits related to water use efficiency may be useful to identify cattle with reduced WI. Water intake showed positive genetic (r = 0.79) and phenotypic (r = 0.60) correlations with DMI, suggesting the use of WI to estimate DMI in future studies. Both RWIADG and RWIDMI were genetically correlated with RFI (0.67 and 0.57, respectively) and ADG (0.49 and 0.44, respectively), showing that RWI is positively associated with feed efficiency, but has an antagonistic relationship with growth. This antagonism, however, may be managed using selection indexes. Genetic improvement of water use efficiency in Senepol cattle is possible through selection and may reduce the water requirements of beef production systems.

Genetic parameters for performance, feed efficiency, and carcass traits in Senepol heifers.

Improving feed efficiency is a key breeding goal in the beef cattle industry. In this study, we estimated the genetic parameters for feed efficiency and carcass traits in Senepol cattle raised in tropical regions. Various indicators of feed efficiency [gain to feed ratio (G:F), feed conversion ratio (FCR), residual weight gain (RG), residual intake and body weight gain (RIG), and residual feed intake (RFI)] as well as growth [final BW, average daily gain (ADG), and DM intake (DMI)], and carcass [rib-eye area (REA), backfat thickness (BF), intramuscular fat score, and carcass conformation score] traits were included in the study. After data editing, records from 1 393 heifers obtained between 2009 and 2018 were used for the analyses. We fitted an animal model that included contemporary group (animals from the same farm that were evaluated in the same test season) as the fixed effect, and a linear effect of animal age at the beginning of the test as a covariate; in addition to random direct additive genetic and residual effects. The (co)variance components were estimated by Bayesian inference in uni- and bivariate analyses. Our results showed that feed efficiency indicators derived from residual variables such as RG, RIG, and RFI can be improved through genetic selection (h2 = 0.14 ± 0.06, 0.13 ± 0.06, and 0.20 ± 0.08, respectively). Variables calculated as ratios such as G:F and FCR were more influenced by environmental factors (h2 = 0.08 ± 0.05 and 0.09 ± 0.05), and were, therefore, less suitable for use in breeding programs. The traits with the greatest and impact on genetic progress in feed efficiency were ADG, REA, and BF. The traits with the greatest and least impact on growth and carcass traits were RG and RFI, respectively. Selection for feed efficiency will result in distinct overall effects on the growth and carcass traits of Senepol heifers. Direct selection for lower RFI may reduce DMI and increase carcass fatness at the finishing stage, but it might also result in reduced growth and muscle deposition. Residual BW gain is associated with the highest weight gain and zero impact on REA and BF, however, it is linked to higher feed consumption. Thus, the most suitable feed efficiency indicator was RIG, as it promoted the greatest decrease in feed intake concomitant with faster growth, with a similar impact on carcass traits when compared to the other feed efficiency indicators.

SEXUAL MATURITY AND TESTICULAR BIOMETRIC OF MONTANA TROPICAL® YOUNG BULLS RAISED ON PASTURE. / MATURIDADE SEXUAL E BIOMETRIA TESTICULAR DE TOUROS JOVENS COMPOSTOS MONTANA TROPICAL® CRIADOS A PASTO.

This study aimed at verifying the sexual maturity stage of Montana Tropical® bulls, with average age of 22 months, raised on pasture, based on the seminal quality, as well as to estimate the parameters of testicular biometry of these animals at the moment of the andrological evaluation. Thus, 3636 male animals were evaluated. The composed bovines formation can be considered like one in the best ways to make use of the advantages of the hybrid vigor or heterosis, in an economically- viable way. Inside of this context, to search the alternatives that become the livestock more productive, a program of composed bovines formation was implemented in 1994, called composed Montana Tropical®, with the objective to make use of the advantages of the crossing among breeds to achieve the production levels aimed. The sexual maturity of Montana® males, with average of 22 months, were 65.68%. The testicular shape predominant in the Montana® animals evaluated were long-moderate (65.54%). KEY-WORDS: Adaptation. Andrological ability. Fertility. Scrotal perimeter. Testicular volume.

O presente trabalho teve como objetivo verificar o estádio de maturação sexual de touros Compostos Montana Tropical®, com média de 22 meses de idade, criados a pasto, baseando-se na qualidade seminal, e estimar parâmetros de biometria testicular destes animais, no momento da avaliação andrológica. Para tal, foram avaliados andrologicamente 3636 machos. A formação de bovinos compostos pode ser considerada como uma das melhores formas de se aproveitar as vantagens do vigor híbrido ou heterose, de maneira economicamente viável. Dentro deste contexto de busca de alternativas que tornem a pecuária de corte mais produtiva, efetivou-se um programa de formação de bovinos compostos em 1994, denominado Composto Montana Tropical®, com o objetivo de aproveitar as vantagens dos cruzamentos entre raças para alcançar os níveis de produção desejados. A maturidade sexual de machos Montana®, com média de 22 meses de idade, foi de 65,68%. O formato testicular predominante nos animais Montana® avaliados foi o longo-moderado (65,54%).PALAVRAS-CHAVE: Adaptação. Aptidão andrológica. Fertilidade. Perímetro escrotal. Volume testicular.