Segmented polynomial model for estimation of egg production curves in laying hens.

1. A model for estimating egg production curves in layers was developed and tested against other existing models. The model uses a three segment polynomial (constant-cubic-linear) and is reparameterised to estimate variables of practical importance. 2. The model predicted future production based on partial data better and estimated egg production curves as well as the currently existing models.

Effect of the time of artificial insemination with frozen-thawed or fresh semen on embryo viability and early pregnancy rate in gilts.

The aim of the present study was to evaluate the effect of artificial insemination time (before or after ovulation) using either fresh or frozen-thawed boar semen on embryo viability and early pregnancy rate. Seventy-seven prepubertal crossbred (Landrace x Large White x Duroc) gilts were inseminated in 4 treatments. Artificial inseminations were performed 6 h either after (A) or before (B) ovulation using frozenthawed (A-frozen, n = 19; B-frozen, n = 19) or fresh semen (A-fresh, n = 21; B-fresh, n = 18). The gilts were induced to puberty by administration of 400 IU of eCG and 200 IU hCG (sc) followed by 500 IU of hCG (sc) 72 h later. Ovulation was predicted to occur 42 h after the second injection. All animals were slaughtered 96 h after AI. Embryos were collected and classified as viable (5- to 8-cells, morulae, compacted morulae and early blastocysts) and nonviable (fragmented, degenerated and 1- to 4-cell embryos). The total embryo viability rate was: 64.3% (A-frozen), 54.2% (A-fresh), 76.0% (B-frozen), 91.9% (B-fresh); (A-fresh vs B-fresh, P = 0.018; A-frozen vs B-frozen, P = 0.094). It was observed that AI before ovulation resulted in a higher percentage of total viable embryos than AI after ovulation (P = 0.041). The early pregnancy rate, defined as presence of at least one viable embryo, was 78.9, 80.9, 84.2 and 94.4% for A-frozen, A-fresh, B-frozen, B-fresh, respectively. There was no significant difference in the early pregnancy rate among groups. In conclusion, there was a detrimental effect upon total embryo viability rate when AI was performed after ovulation with either frozen-thawed or fresh semen. The total embryo viability rate and the early pregancy rate were not affected by AI with either frozen-thawed or fresh semen regardless of the time of AI.

Patogenicidade de amostras de Mycoplasma synoviae isoladas no Brasil / Pathogenicity of Mycoplasma sinoviae strains isolated in Brazil

Comparou-se, em ovos embrionados, a virulência de quatro amostras brasileiras de Mycoplasma sinoviae (Ms) com a da amostra padräo MS WVU 1853. Um dos isolados e a amostra padräo tiveram o mesmo índice de mortalidade embrionária indicando alta virulência. Dois isolados tiveram virulência semelhante à do grupo controle, näo detectável pelo método utilizado, e o quinto isolado apresentou virulência intermediária