Effect of pasteurized egg yolk and rosemary honey supplementation on quality of cryopreserved ram semen

• The incorporation of pasteurized egg in freezing extender increase ram sperm quality.
• Rosemary honey has a beneficial effect on motility and viability after sperm freezing.
• Pasteurized egg instead of fresh egg yolk facilitates the ram sperm cryopreservation.

The aim of this study was to determine the effect of pasteurized egg yolk and the supplementation with rosemary honey on ram sperm quality after cryopreservation process. Ejaculates were obtained from three rams (Rasa Aragonesa), and semen samples were processed using straw freezing procedure. In experiment 1, semen samples were frozen in four different extenders: (D1) Fiser egg yolk extender as control, and three experimental extenders: (D2) pasteurized egg yolk in fraction 1 (F1); (D3) rosemary honey in F1 and fraction 2 (F2); D4) pasteurized egg yolk and rosemary honey in F1 and honey in F2. Total and progressive motility, viability, acrosome integrity and hypoosmotic swelling test response (HOST test) were evaluated post-thawing and 2 h post-thawing. A significant increase in percentage of total motile sperm was observed in the presence of pasteurized egg yolk, alone or in combination with rosemary honey. Acrosome integrity was significantly higher in pasteurized egg yolk extenders (p < 0.05), however rosemary honey decreased HOST positive sperm after thawing. In experiment 2, embryo development was tested. D2 extender showed that the embryo development rate was significantly (p < 0.05) higher than both D1 and D4 extenders. It could be suggested that Fiser extender composition can be modified replacing fresh egg yolk by pasteurized egg yolk and fructose by honey, without detrimental effects on sperm quality after cryopreservation.