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In cow-calf beef production systems, the growth and development of replacement heifers deserve special attention because they affect the age at puberty and the onset of reproductive activity. Therefore, the objective of this study was to test if changes in average daily gain (ADG) have an effect on eye muscle area, rump fat depth and back-fat thickness in developing beef heifers. These traits of 42 beef heifers were measured over time. The results of the current study allow inferring that heifers older than 385 days and with high rates of ADG (above 0.950 kg per day) have the greatest impact on longissimus muscle area growth (above 57 cm2). On the other hand, it is observed that younger heifers (less than 230 days old) do not exceed 48 cm2 of the longissimus muscle area, even with ADGs around 1.25 kg. A positive relationship between the rate of ADG and rump fat depth was also evidenced, observing that rump fat depth deposition is influenced by the rate of ADG. The results of the current study show a linear trajectory of rump fat depth, indicating that for every 0.10 kg of ADG during a period exceeding 56 days, an increase of 1.09 mm of rump fat depth occurs. In conclusion, this study illustrates a simple way on how ADG and age affect the body composition traits in beef heifers and shows that changes in average daily gain affect muscle and fat tissue growth, as determined by longissimus muscle area and rump fat depth in growing beef heifers.

Abstract: The objective of this work was to identify relationships of the body mass index (BMI) with the body energy reserves and tissue composition of shoulder and leg cuts of Corriedale lambs. Twenty-two sheep with average age of 18 months were used. Linear regressions were determined between the studied characteristics. The mean body mass, body condition score (BCS), and BMI were 49.09±7.8 kg, 2.69±0.81, and 10.66±0.99, respectively. The BMI was correlated with the BCS (r = 0.51) and internal fat (r = 0.81). Multiple linear equations, involving BMI and BCS, yielded correlation coefficients between 0.50 and 0.76, with significant values for all studied characteristics. The body mass index allows estimating the body energy reserves of Corriedale sheep.

The objective of this study was to evaluate the effects of sexual status on blood testosterone levels and its influence on lamb growth. A total of 49 Texel x Corriedale males, originating of single births, were divided into three groups: uncastrated (n = 16), castrated (n = 17) and cryptorchid (n = 16), in the State of Rio Grande do Sul, in extensive natural pasture, with feed supplementation after weaning. The effect of the sexual status was examined by analysis of variance. Uncastrated and castrated lambs showed higher body weight, thoracic perimeter, and body compactness between the 35th and 203th day of age. Uncastrated lambs had mean weight higher than cryptorchid lambs over the whole period. Cryptorchid lambs had an average weight gain greater than castrated lambs between the 203rd and 259th days. Castrated lambs had a higher body condition score on the 147th day than the cryptorchid lambs, and on the 175th and 203rd days than uncastrated and cryptorchid lambs. Blood testosterone concentrations were higher in the uncastrated and cryptorchid lambs on the 203rd and 231st days and in the overall mean. The findings of this study showed that, with advancing age, the sexual status affects the testosterone production, not showing differences regarding growth at young ages.

O estudo foi realizado com objetivo de avaliar os efeitos da condição sexual nos níveis sanguíneos de testosterona e sua influência no crescimento de cordeiros. Foram utilizados 49 machos cruza Texel x Corriedale, oriundos de partos simples, divididos em três grupos: não castrados (n=16), castrados (n=17) e induzidos ao criptorquidismo (n=16), criados na região do Bioma Pampa, no Estado do Rio Grande do Sul, em condições extensivas de pastagem natural, com suplementação alimentar após o desmame. Foi utilizada a análise de variância para avaliar o efeito da condição sexual. Cordeiros não castrados e castrados apresentaram valores superiores de peso corporal entre o 35º e o 203º dia de idade, assim como no perímetro torácico e compacidade corporal. Cordeiros não castrados foram superiores aos criptorquidas na média de peso no período total. Criptorquidas apresentaram ganho médio de peso superior aos castrados entre o 203º e 259º dias. Castrados apresentaram escore de condição corporal superior, no 147º dia em relação aos criptorquidas, e no 175º e 203º dias em relação a não castrados e criptorquidas. As concentrações de testosterona sanguínea foram superiores nos não castrados e criptorquidas no 203º e 231º dias e na média geral. Conclui-se que, com o avanço da idade, a condição sexual afeta a produção hormonal de testosterona não se observando diferenças em termos de crescimento em idades jovens.

ABSTRACT This study was intended to evaluate body size structure and growth parameters of crossbred heifers fed at four nutritional levels to achieve puberty earlier. Animals were classified depending on their level of crossing between Nelore and Hereford and subjected to four nutritional levels (kg day−1) as follows: 0.5 (light; n = 32), 0.75 (medium; n = 32), 1.00 (high; n = 29), and 1.25 (very high; n = 27). Heifers at puberty and at weaning were individually classified for growth parameters. The fat thickness and longissimus muscle area throughout the experimental period were determined by ultrasonography. The height, heart girth, frame, and weight:height ratio were variables used to evaluate body traits. Univariate analysis of variance using the GLIM MIXED procedure os SPSS was performed and the significance level was set at 0.05. Age and body weight at puberty were 388±1.9 days and 331.4±1.3 kg, respectively. Body condition score demonstrated an interaction between nutritional level and crossbred degree. Heifers with the highest degree of Nelore had higher fat thickness and lower weight:height ratio compared with other racial groups at puberty. Pearson correlation coefficient showed a negative association for body condition score (−0.34) and fat thickness (−0.58) compared with age at puberty. The increased fat thickness at younger ages at puberty was observed in all racial groups. The increased weight:height ratio at younger ages at puberty was observed in all racial groups. We observed higher values for a frame in animals at the higher level of supplementation. There is a greater correlation between live weight gain and phenotypic traits during weaning to achieve puberty at an earlier age in crossbred heifers.

O estudo foi realizado com objetivo de avaliar os efeitos da condição sexual nos pesos e rendimentos dos não constituintes da carcaça de cordeiros cruza Texel x Corriedale. Foram utilizados 46 machos divididos em três grupos: não castrados (n=15), castrados (n=17) e induzidos ao criptorquidismo (n=14). Foi adotado o delineamento experimental inteiramente casualizado com três tratamentos e número variável de repetições. Foi realizada análise de variância para avaliar o efeito da condição sexual sobre as características estudadas. Cordeiros castrados atingiram as condições estipuladas para o abate mais precocemente. Não castrados e induzidos ao criptorquidismo apresentaram pesos superiores de cabeça (kg), pele (kg), pênis (kg) e fígado com vesícula (kg). Não castrados apresentaram valores superiores do conjunto pulmões com traqueia (kg) em relação a animais castrados. Conclui-se que cordeiros não castrados e induzidos ao criptorquidismo apresentam pesos superiores de alguns componentes corporais quando terminados em campo nativo recebendo suplementação de 1% do peso corporal. Proporcionalmente, a condição sexual não interfere nos rendimentos dos componentes corporais de cordeiros Texel x Corriedale.Palavras-chave: Castração; componentes corporais; indução ao criptorquidismo; Ovis aries.