EFFECT OF ORGANIC AND INORGANIC MINERAL SUPPLEMENTATION ON SEMINAL QUALITY OF BOARS EXPOSED TO HEAT STRESS

Abstract

Seasonal high temperatures or inadequate nutrition can decrease reproductive efficiency in boars, especially through a reduction in spermatozoal number / ejaculate and percentage of normal spermatozoa. The aim of this study was to evaluate the effect of organic and inorganic trace mineral supplementation on seminal quality in boars exposed to high environmental temperatures. The experiment was conducted in Southern Brazil, west of Parana State. Boars (2 years of age) were divided into three groups to receive: inorganic (GIn, n=4) and organic (GOr, n=4) mineral supplementation and a lactation diet (GCo, n=5). Inorganic and organic diets contained a premix of inorganic and organic trace minerals, respectively, with the same quantity of each trace mineral, based on NRC (NRC, 1998) for boars. The lactation diet was based on NRC for lactating sows and contained a higher level of inorganic trace minerals, protein and metabolic energy. Maximum mean environmental temperatures were higher than the normal thermal comfort temperature for boars (26oC) during the experimental period, and were associated with a reduction in semen quality. Results are expressed as mean ± SEM. The semen volume of Inorganic and Organic diet groups were higher than Lactation group animals (345.7 ± 92.6 mL and 338.4 ± 67.8 mL versus 302.5 ± 81.4 mL, respectively; P=0.02). Boars in the Organic diet group had higher sperm concentration when compared to the Inorganic diet group (233.5 ± 76.7 X 106 sptz/mL versus 181.2 ± 77.3 X 106 sptz/mL, respectively; P=0.006). Percentage of normal spermatozoa, averaged higher in the Organic group than both Inorganic and Lactation groups (93.31 ± 5.20% versus 78.48 ± 12.15% and 82.59 ± 17.27%, respectively; P=0.00021). High temperatures (>34.5 oC) reduced normal spermatozoa number in all groups, but with significant differences only in the Inorganic and Lactation groups (P=0.03). Organic minerals were benefic to seminal quality, reducing some of the heat stress effects in exposed boars.
KEY WORDS: Heat stress, organic minerals, semen, swine.