Estudos foram conduzidos com o objetivo de avaliar os efeitos da relação proteína metabolizável: energia metabolizável (PM:EM) sobre o crescimento acelerado de novilhas pré-púberes, assim como, estimar o peso corporal por meio de equações de regressão que utilizam medidas indiretas de desenvolvimento corporal. Inicialmente doze novilhas Holandês-Jersey (idade média de 90 dias) foram alocadas em baias individuais, com livre acesso a água e sombra, até o início da puberdade (aproximadamente 300 kg). Os animais foram distribuídos em delineamento inteiramente casualizado em dois tratamentos, de acordo com a relação proteína metabolizável:energia metabolizável: controle (PM:EM = 39 g/Mcal); e alta relação (PM:EM = 44,5 g/Mcal). Quinzenalmente, os animais foram pesados e as medidas de desenvolvimento corporal avaliadas. Mensalmente, foram medidos o tamanho e comprimento dos tetos, como método indireto de aferição do desenvolvimento mamário, e colhidas amostras de sangue para avaliação das concentrações plasmáticas de glicose, nitrogênio uréico e progesterona. As relações de PM:EM observadas foram superiores as inicialmente preditas pelo NRC (2001) 44,39 vs 39 g/Mcal e 52,98 vs 44,5 g/Mcal, respectivamente para os tratamentos controle e alta relação. Não foram observadas diferenças estatísticas entre os tratamentos para consumo de matéria seca, peso corporal (PC), perímetro torácico (PT), altura na cernelha (AC), largura da garupa (LG), largura e comprimento dos tetos (P< 0,05). Posteriormente, os dados de PC, AC, LG e PT monitorados até a obtenção de 300 kg de PC, foram avaliados em análises de regressão, sendo o peso a variável dependente e as medidas de desenvolvimento corporal as variáveis independentes. Foram considerados os efeitos lineares, quadráticos e cúbicos destas variáveis. Não foram observados efeitos significativos (P<0,05) do método de estimação do PC sobre esta variável. No entanto efeitos significativos são observados para idade e interação ente idade e método de estimação (P< 0,0001). As equações lineares de AC e LG subestimaram (P<0,05) PC na faixa de idade de 11-13 meses. Entre 6-7,9 meses todas as equações lineares de desenvolvimento corporal superestimam (P< 0,05) os valores de PC. Na faixa etária de 3-5,9 meses apenas as equações lineares de AC superestimaram os valores de peso (P< 0,05). A equação proposta por Heinrich; Rogers; Cooper (1992) subestimou os valores de peso em relação à aferição em balança mecânica na faixa etária de 6-7,9 meses (P<0,05). Em conclusão, medidas de crescimento e desenvolvimento corporal não foram influenciadas pela relação PM:EM da dieta. O uso de medidas indiretas de estimação do peso corporal mostrou-se eficiente na estimação do PC de fêmeas mestiças, assim como a estimação por meio da equação proposta por Heinrich; Rogers; Cooper (1992).; Cooper (1992). / Trials were conducted in order to evaluate the effects of metabolizable protein: metabolizable energy (MP:ME) ratio on accelerated growth of prepubertal dairy heifers, and also the use of indirect methods of corporal growth for body weight estimation. First, twelve Holstein-Jersey heifers (90 days of average age) were housed in individual pens, with free access to water and shadow, until beginning of puberty (around 300 kg). Heifers were allocated on one of the two treatments, control (MP:ME = 39 g/Mcal) and high MP:ME ratio (MP:ME = 44,5 g/Mcal), according to a completely randomized statistical design. Biweekly, heifers were weighed and growth parameters were measured. Monthly, size and length of teats were taken, as indirect method for mammary growth assessment. Blood samples were also collected monthly to evaluate the plasmatic concentration of glucose, and urea nitrogen and progesterone. The MP:ME ratio observed were higher than those firstly predict by NRC (2001): 44.39 vs 39 g/Mcal and 52.98 vs 44.5 g/Mcal, respectively for control and high MP:ME treatment. There were no statistical effects of diet MP:ME ratio on dry matter intake, body weight (BW), hearth girth (HG), withers height (WH), hip width (HW), size and length of teats (P< 0.0001). With the same data a second study was conducted. Data of BW, WH, HW and HG monitored until 300 kg of BW, were used for regression analysis. BW was considered the dependent variable and growth parameters the independent one. Linear, quadratic and cubic effects of the independent variable were considered. There was no statistical effect of method for estimation BW (P<0.05). However, statistical effects were found to age and interaction of age and method for estimation BW (P< 0.0001). Linear regression of WH and HW underestimated the BW on age range from 11-13 months. For 6-7.9 months all linear regression of corporal parameters overestimate the values of BW (P<0.05). On age range from 3-5.9 months only linear regression of WH overestimate the values of weight (P<0,05). Between 6-7.9 months, the regression equation proposed by Heinrich; Rogers; Cooper (1992) underestimated the BW compared with mechanic scale. In conclusion, measures of growth and corporal parameters were not influenced by diet MP:ME ratio. Use of indirect methods of body weight estimation is efficient to estimate the BW of crossbreed heifers, at the same manner as the Heinrich; Rogers; Cooper (1992) proposed equation.

Estudos foram conduzidos com o objetivo de avaliar os efeitos da relação proteína metabolizável: energia metabolizável (PM:EM) sobre o crescimento acelerado de novilhas pré-púberes, assim como, estimar o peso corporal por meio de equações de regressão que utilizam medidas indiretas de desenvolvimento corporal. Inicialmente doze novilhas Holandês-Jersey (idade média de 90 dias) foram alocadas em baias individuais, com livre acesso a água e sombra, até o início da puberdade (aproximadamente 300 kg). Os animais foram distribuídos em delineamento inteiramente casualizado em dois tratamentos, de acordo com a relação proteína metabolizável:energia metabolizável: controle (PM:EM = 39 g/Mcal); e alta relação (PM:EM = 44,5 g/Mcal). Quinzenalmente, os animais foram pesados e as medidas de desenvolvimento corporal avaliadas. Mensalmente, foram medidos o tamanho e comprimento dos tetos, como método indireto de aferição do desenvolvimento mamário, e colhidas amostras de sangue para avaliação das concentrações plasmáticas de glicose, nitrogênio uréico e progesterona. As relações de PM:EM observadas foram superiores as inicialmente preditas pelo NRC (2001) 44,39 vs 39 g/Mcal e 52,98 vs 44,5 g/Mcal, respectivamente para os tratamentos controle e alta relação. Não foram observadas diferenças estatísticas entre os tratamentos para consumo de matéria seca, peso corporal (PC), perímetro torácico (PT), altura na cernelha (AC), largura da garupa (LG), largura e comprimento dos tetos (P< 0,05). Posteriormente, os dados de PC, AC, LG e PT monitorados até a obtenção de 300 kg de PC, foram avaliados em análises de regressão, sendo o peso a variável dependente e as medidas de desenvolvimento corporal as variáveis independentes. Foram considerados os efeitos lineares, quadráticos e cúbicos destas variáveis. Não foram observados efeitos significativos (P<0,05) do método de estimação do PC sobre esta variável. No entanto efeitos significativos são observados para idade e interação ente idade e método de estimação (P< 0,0001). As equações lineares de AC e LG subestimaram (P<0,05) PC na faixa de idade de 11-13 meses. Entre 6-7,9 meses todas as equações lineares de desenvolvimento corporal superestimam (P< 0,05) os valores de PC. Na faixa etária de 3-5,9 meses apenas as equações lineares de AC superestimaram os valores de peso (P< 0,05). A equação proposta por Heinrich; Rogers; Cooper (1992) subestimou os valores de peso em relação à aferição em balança mecânica na faixa etária de 6-7,9 meses (P<0,05). Em conclusão, medidas de crescimento e desenvolvimento corporal não foram influenciadas pela relação PM:EM da dieta. O uso de medidas indiretas de estimação do peso corporal mostrou-se eficiente na estimação do PC de fêmeas mestiças, assim como a estimação por meio da equação proposta por Heinrich; Rogers; Cooper (1992).; Cooper (1992). / Trials were conducted in order to evaluate the effects of metabolizable protein: metabolizable energy (MP:ME) ratio on accelerated growth of prepubertal dairy heifers, and also the use of indirect methods of corporal growth for body weight estimation. First, twelve Holstein-Jersey heifers (90 days of average age) were housed in individual pens, with free access to water and shadow, until beginning of puberty (around 300 kg). Heifers were allocated on one of the two treatments, control (MP:ME = 39 g/Mcal) and high MP:ME ratio (MP:ME = 44,5 g/Mcal), according to a completely randomized statistical design. Biweekly, heifers were weighed and growth parameters were measured. Monthly, size and length of teats were taken, as indirect method for mammary growth assessment. Blood samples were also collected monthly to evaluate the plasmatic concentration of glucose, and urea nitrogen and progesterone. The MP:ME ratio observed were higher than those firstly predict by NRC (2001): 44.39 vs 39 g/Mcal and 52.98 vs 44.5 g/Mcal, respectively for control and high MP:ME treatment. There were no statistical effects of diet MP:ME ratio on dry matter intake, body weight (BW), hearth girth (HG), withers height (WH), hip width (HW), size and length of teats (P< 0.0001). With the same data a second study was conducted. Data of BW, WH, HW and HG monitored until 300 kg of BW, were used for regression analysis. BW was considered the dependent variable and growth parameters the independent one. Linear, quadratic and cubic effects of the independent variable were considered. There was no statistical effect of method for estimation BW (P<0.05). However, statistical effects were found to age and interaction of age and method for estimation BW (P< 0.0001). Linear regression of WH and HW underestimated the BW on age range from 11-13 months. For 6-7.9 months all linear regression of corporal parameters overestimate the values of BW (P<0.05). On age range from 3-5.9 months only linear regression of WH overestimate the values of weight (P<0,05). Between 6-7.9 months, the regression equation proposed by Heinrich; Rogers; Cooper (1992) underestimated the BW compared with mechanic scale. In conclusion, measures of growth and corporal parameters were not influenced by diet MP:ME ratio. Use of indirect methods of body weight estimation is efficient to estimate the BW of crossbreed heifers, at the same manner as the Heinrich; Rogers; Cooper (1992) proposed equation.

This study, being part of a larger project - "Canadian/New Zealand GxE Interaction Trial" - is comparing Canadian and New Zealand sired heifers for growth traits within Canada, since differences for growth traits were found in the Polish strain comparison (Jasiorowski et al., 1987) and due to selection programs in the two countries. Twenty Canadian Holstein and twenty New Zealand Friesian progeny tested, A.I. bulls were randomly mated to over 1,000 cows in 10 Canadian herds. 3,539 records of weight and wither height from 475 heifers (i.e. 241 Canadian and 234 New Zealand sired) were generated. Subsets of the data for different stages of heifer maturity were analyzed separately. Herd and strain effects least squares means were estimated using analysis of variance. Genetic and phenotypic and correlations and heritability for weight and wither height were estimated by a Derivative-Free Restricted Maximum Likelihood (DFREML) algorithm and an animal model (AM). No differences were found between sire strains for weight except at 15 and 18 months where sib groups of Canadian (CN) sires were heavier than their New Zealand (NZ) contemporaries (393 vs 386 kg and 447 vs 445 kg, respectively). CN sired heifers were taller at all ages except at birth, 3 and 9 months of age. At 24 months CN heifers were 136 cm while NZ heifers were 133 cm. Heritability estimates for weight at birth was 0.62 for the CN strain and 0.59 for the NZ strain. CN estimates (3 to 6 months) and NZ estimates (3 to 9 months) were close to zero. Between 9 to 24 months CN strain estimates ranged from 0.44 to 0.69 while NZ estimates were 0.17 to 0.51. The joint estimates ranged from 0.10 to 0.66. Heritability estimates for wither height for CN strain at birth and between 9 to 21 months were between 0.34 to 0.66 and close to zero between 3 to 6 and at 24 months. The NZ estimates at birth, 18, 21 and 24 months were between 0.36 to 0.93 but close to zero between 3 to 15 months. The joint estimates ranged from 0.32 to 0.75 between 12 to 24 months. Genetic correlations between weight and wither height ranged from 0.62 to 1.0 for CN strain and from -0.04 to 0.91 for NZ strain between 4.5 to 21 months. At six months of age the genetic correlation for CN strain was -0.01 and NZ strain was 0.54. At birth, both sire groups had a genetic correlation of 1.0. At 24 months NZ strain had a genetic correlation of 0.84 while that of the CN strain was 0. Genetic correlations for the joint analysis ranged from 0.61 to 1.0 for all ages except at 6 months (0.18). Phenotypic correlations between weight and wither height were between 0.33 to 0.60 for CN group and 0.33 to 0.62 for NZ group. The joint estimates were 0.36 to 0.61. There were no differences in the phenotypic variances except at 9, 12 and 15 months. Genetic variances were different at all ages except at birth for weight. / Land and Food Systems, Faculty of / Graduate