Submitted to: Small Ruminant Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/21/2004
Publication Date: 10/1/2006
Citation: Burke, J.M., Rosenkrans, C.F., Rorie, R.W., Golden, C., Apple, J.K. 2006. Reproductive responses of ram lambs fed endophyte-infected tall fescue. Small Ruminant Research. 66:121-128. Interpretive Summary: Tall fescue toxicosis is a condition associated with grazing endophyte-infected tall fescue that can reduce economic outcome of a ruminant production system. Reduced income results from decreased pregnancy rates and reduced growth rate. The current study determined the influence of endophyte-infected tall fescue on reproductive development and function and carcass characteristics of ram lambs fed a diet free of endophyte-infected seed or a diet with infected tall fescue seed during a six week period in autumn. Feeding endophyte-infected fescue seed to ram lambs was associated with decreased concentrations of spermatozoa in semen. This study informs producers and extension agents that male fertility can potentially be enhanced when ruminants are grazing endophyte-free tall fescue, as compared to endophyte-infected.
Technical Abstract: Our objective was to determine the influence of endophyte-infected tall fescue on reproductive development and function and carcass characteristics of ram lambs. Hampshire and Suffolk rams that were approximately 214 d of age were fed a diet of endophyte-free (EF; n = 8) or infected (EI; n = 9) fescue seed (34% of diet; 4.8 microgram/g ergovaline). Daily high temperature during the six week feeding period ranged from 16 to 27°C. Rams were slaughtered after six weeks of feeding and carcass characteristics and organ weights were determined. Signs of fescue toxicosis in EI fed rams included increased rectal temperature (P < 0.001), increased respiration rate at higher ambient temperatures (P < 0.003), and reduced serum concentrations of prolactin (P < 0.001). Body weight of EI fed rams tended to decrease after 36 d of feeding compared with EF fed rams (-3.0 vs 0.51 kg; P < 0.07) and BCS was similar between treatments throughout the trial. Serum concentrations of testosterone were greater in EI compared with EF fed rams (P < 0.005). Scrotal skin temperature, scrotal circumference, semen volume, percent sperm motility, and percent abnormal sperm were similar between treatments. Spermatozoa concentration tended to be greater in EF compared with EI fed rams after 43 days of feeding (P < 0.07). Rate of forward movement of spermatozoa tended to be greater in EF compared with EI fed rams between Days 15 and 29 of feeding (P < 0.08). Weights of reproductive and vital organs, carcass cutability and quality characteristics were similar between EF and EI fed rams. Feeding endophyte-infected fescue seed to ram lambs was associated with decreased concentrations of spermatozoa in semen and increased serum concentrations of testosterone, perhaps because of decreased clearance rate of this steroid.