COSTS AND BENEFITS OF BREED UTILIZATION STRATEGIES IN SHEEP

Problems involved in choosing appropriate criteria and procedured for economic analyses of breed and mating system evaluation experiments in sheep are described. Literature is reviewed of experiments in which biological or economic efficiency has been investigated. The range in relative economic merit from the poorest to the best group in an experiment typically is from 100 to 120, with values over 140 not uncommon for the best group in an experiment. Heterosis for exonomic traits per ewe mated has ranged from 2% to 26%. Suggestions are presented for consideration in future studies on the economic ramifications of mating system and breed utilization strategies. Particularly critical is the need to assess accurately the feed costs of individual grazing sheep. Also critically needed are bioeconomic simulation models for each major physical environment and management system for sheep productio

Estimation of genetic variation in residual variance in female and male broiler chickens

In breeding programs, robustness of animals and uniformity of end product can be improved by exploiting genetic variation in residual variance. Residual variance can be defined as environmental variance after accounting for all identifiable effects. The aims of this study were to estimate genetic variance in residual variance of body weight, and to estimate genetic correlations between body weight itself and its residual variance and between female and male residual variance for broilers. The data sets comprised 26 972 female and 24 407 male body weight records. Variance components were estimated with ASREML. Estimates of the heritability of residual variance were in the range 0.029 (s.e.50.003) to 0.047 (s.e.50.004). The genetic coefficients of variation were high, between 0.35 and 0.57. Heritabilities were higher in females than in males. Accounting for heterogeneous residual variance increased the heritabilities for body weight as well. Genetic correlations between body weight and its residual variance were 20.41 (s.e.50.032) and 20.45 (s.e.50.040), respectively, in females and males. The genetic correlation between female and male residual variance was 0.11 (s.e.50.089), indicating that female and male residual variance are different traits. Results indicate good opportunities to simultaneously increase the mean and improve uniformity of body weight of broilers by selection

The effects of age at first lambing on production and longevity of Columbia and Targhee ewes

Published May 1977. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalo

Management considerations for accelerated lambing in western Oregon

Published February 1979. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalo

Evaluation of Border Leicester and Targhee crossbred ewes for the Pacific coastal Northwest

Published November 1978. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalo

In vitro characterisation of fresh and frozen sex-sorted bull spermatozoa

peer-reviewedThis study sought to compare the in vitro characteristics of fresh and frozen non-sorted (NS) and sex-sorted (SS) bull spermatozoa. Experiment 1: Holstein–Friesian ejaculates (n = 10 bulls) were split across four treatments and processed: (1) NS fresh at 3 × 106 spermatozoa, (2) X-SS frozen at 2 × 106 spermatozoa, (3) X-SS fresh at 2 × 106 spermatozoa and (4) X-SS fresh at 1 × 106 spermatozoa. NS frozen controls of 20 × 106 spermatozoa per straw were sourced from previously frozen ejaculates (n = 3 bulls). Experiment 2: Aberdeen Angus ejaculates (n = 4 bulls) were split across four treatments and processed as: (1) NS fresh 3 × 106 spermatozoa, (2) Y-SS fresh at 1 × 106 spermatozoa, (3) Y-SS fresh at 2 × 106 spermatozoa and (4) X-SS fresh at 2 × 106 spermatozoa. Controls were sourced as per Experiment 1. In vitro assessments for progressive linear motility, acrosomal status and oxidative stress were carried out on Days 1, 2 and 3 after sorting (Day 0 = day of sorting. In both experiments SS fresh treatments had higher levels of agglutination in comparison to the NS fresh (P < 0.001), NS frozen treatments had the greatest PLM (P < 0.05) and NS spermatozoa exhibited higher levels of superoxide anion production compared with SS spermatozoa (P < 0.05). Experiment 1 found both fresh and frozen SS treatments had higher levels of viable acrosome-intact spermatozoa compared with the NS frozen treatments (P < 0.01).ACCEPTEDpeer-reviewe

Effects of the level of early productivity on the lifespan of ewes in contrasting flock environments

Selection for high levels of prolificacy has allowed substantial improvements in the production efficiency of New Zealand (NZ) sheep farms, but the consequences on ewe lifetime performance are mostly unknown. In this study, the relationship between the level of prolificacy early in ewes' productive lives and their probability to survive later (i.e. stayability) was evaluated in two contrasting NZ flock environments. Records were obtained from 6605 ewes from four ram breeder flocks representing either a moderate (n = 2) or a highly variable (n = 2) nutritional environment. All ewes lambed for the first time at 2 years of age and were mated the following year. The number of lambs born during the first 2 years of productive life (NLB2-3) was used as a measure of early prolificacy. Effects of NLB2-3 on stayability to 4, 5, 6, 7 and 8 years old were analysed using logistic regression. Curvilinear effects (logit-transformed) were detected (P < 0.05) until stayability to 6 years and to 8 years old in the highly variable and the moderate environment, respectively. The NLB2-3 that resulted in maximum expected stayability to various ages was 3.9 to 4.2, and 4.5 to 4.7 lambs in the highly variable and in the moderate flock environments, respectively. In addition, ewe stayability was reduced when the proportion of the litter that survived from birth to weaning (i.e. ewe rearing ability) was submaximal during the early productive life. High prolific ewes had a low rearing ability whatever the environment whereas the rearing ability of lowly prolific ewes was apparently more sensitive to the nutritional environment. The poor maternal performance of ewes with low levels of NLB2-3 led to a premature culling by breeders whereas the high early reproductive effort associated with high levels of NLB2-3 seemed to be at the cost of ewes' survival, even in the moderate flock environment. In conclusion, the flock environment influenced the level of early prolificacy beyond which ewe longevity was reduced. It is suggested that further selection for high and early prolificacy in NZ flocks is likely to impair ewes' lifetime productivity

Parâmetros genéticos para diferentes relações de peso ao nascer e à desmama em vacas da raça Nelore

O presente estudo foi desenvolvido com o objetivo de estimar herdabilidade e repetibilidade para diferentes medidas de eficiência produtiva de vacas e determinar a melhor maneira de calcular as relações de peso, visando a sua utilização como critério de seleção em rebanhos da raça Nelore. Os dados analisados são de animais da raça Nelore, pertencentes ao Projeto de Seleção das Raças Zebuínas e Caracu do Centro APTA Bovinos de Corte, do Instituto de Zootecnia de Sertãozinho. Os animais são selecionados para maior peso ao sobreano (rebanhos NeS e NeT, analisados como um único rebanho) e para peso ao sobreano próximo da média (NeC) do grupo de contemporâneos, desde 1980. As características utilizadas no estudo foram: 1) RPN = relação de peso ao nascer do bezerro / peso da vaca ao parto; 2) RPN2 = relação do peso ao nascer do bezerro / peso metabólico da vaca ao parto; 3) RPD = relação de peso à desmama do bezerro / peso da vaca à desmama; e 4) RPD2 = relação do peso à desmama do bezerro / peso metabólico da vaca à desmama. Os parâmetros genéticos foram estimados considerando dois arquivos: vacas com bezerros (CB) e vacas com e sem bezerros (SB). A RPN e a RPN2 foram calculadas somente no arquivo CB, enquanto que RPD e RPD2 foram calculadas em ambos os arquivos (CB e SB). Os parâmetros genéticos foram estimados pelo método da máxima verossimilhança restrita. As estimativas de herdabilidade para as características RPN; RPN2; RPD_CB; RPD2_CB; RPD_SB e RPD2_SB foram: 0,17±0,02; 0,16±0,02; 0,22±0,04; 0,19±0,03; 0,20±0,01 e 0,16±0,01, respectivamente. As repetibilidades estimadas variaram de 0,22 a 0,68. A utilização das relações de peso como critério de seleção deve promover, a longo prazo, melhorias na eficiência produtiva das vacas. As relações de peso têm sido consideradas apenas como informações para o descarte de vacas em alguns programas de seleção, mas poderiam ser incluídas em índices de seleção, principalmente quando calculada considerando o peso metabólico da vaca à desmama, incluindo tanto as vacas que desmamaram um bezerro, quanto aquelas que falharam em desmamar.The objective of this study was to estimate heritability and repeatability for different measures of cows' productive efficiency and determine the best way to calculate the weight ratios, in order to use as selection criteria in Nelore herds. Data of Nelore animals from Centro APTA Bovinos de Corte-Sertãozinho, Instituto de Zootecnia were analyzed. The animals are selected for higher yearling weight (NeS and NeT herds, considered as a single herd in this paper) and, for mean yearling weight (NeC) within contemporary group, since 1980. The traits used in this study were: 1) RPN = ratio of birth weight of the calf / cow weight at calving; 2) RPN2 = ratio of birth weight of the calf / metabolic cow weight at calving; 3) RPD = ratio of weaning weight of the calf / cow weight at weaning and, 4) RPD2 = ratio of weaning weight of calf / metabolic cow weaning weight. For estimate genetic and phenotypic parameters, were considered two files: cows with calves (CB) or with and without calves (SB). The RPN and RPN2 were calculated only on CB file, and RPD and RPD2 were calculated in both files (CB and SB). Genetic parameters were estimated by restricted maximum likelihood. Estimates of heritability for traits RPN; RPN2; RPD_CB; RPD2_CB; RPD_SB and RPD2_SB were: 0.17±0.02, 0.16±0.02, 0.22±0.04, 0.19±0.03, 0.20±0.01 and 0.16±0.01, respectively. The repeatability estimates ranged from 0.22 to 0.68. The use of weight ratios as selection criteria should promote, at long-term, improvements in production efficiency. In some breeding programs, weight ratios have been considered only as information for disposal of cows, but could be included in selection indices, especially if it is calculated considering the metabolic weight of cow at weaning from both cows, that weaned a calf as those that failed to wean.Universidade Estadual Paulista (UNESP) Departamento de Zootecnia Faculdade de Ciências Agrárias e VeterináriasAgência Paulista de Tecnologia dos Agronegócios (APTA) Instituto de Zootecnia (IZ) Centro de Apoio a Pesquisa Tecnológica dos Agronegócios de Bovinos de Corte (CAPTA - Bovinos de Corte)Universidade Estadual Paulista (UNESP) Departamento de Zootecnia Faculdade de Ciências Agrárias e Veterinária