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Effect of Plane of Nutrition upon Reproductive Performance of Boars¹

University of Kentucky, Lexington

Abstract

Three groups of three weanling Hampshire boars were placed on 100%, 70% and 50% of the National Research Council's recommended T.D.N. intake for growing boars, and the effect upon growth, age at puberty and reproductive performance were studied. The boars remained on their respective-nutritional planes for 312 days. Average daily gains and final weights were 1.13 and 382 lb., 0.85 and 293 lb., and 0.69 and 243 lb., respectively, for the three groups. Average ages at puberty were 203, 212 and 219 days, and average weights were 223, 171 and 135 lb., respectively. Weight but not age at puberty was significantly different among the boar groups on the different planes of nutrition.

Boars on the higher plane of nutrition produced larger semen volume, but motility, sperm cell concentration and percent morphologically abnormal cells were not significantly affected. During weekly semen collections average semen volumes were 173, 137 and 121 ml., respectively. Average sperm counts were 378,000; 417,000 and 398,000 cells/mm³, respectively. Average motility was above 80% for all groups, and percent abnormal cells ranged from 6.5 to 8.6. The proportion of total semen volume composed of gelatinous material was 15.3, 15.4 and 15.7% for the three groups and appeared to be unaffected by nutritional treatment.

Fertility levels of the boars, using as a criterion the percent of corpora lutea represented by normal embryos in gilts at 25 to 28 days of gestation, were 54.9, 63.1 and 55.7%, respectively, for the three groups. For pregnant gilts only the percentages were 75.7, 74.7 and 70.2, respectively. Fertility did not differ significantly among the boar groups.

Time-series regression coefficients calculated on the various semen characteristics during a seven-day collection period revealed daily changes which were of similar magnitude for all treatment groups. Concentration was the only characteristic for which the group regressions differed significantly (P <.05). Restricting the plane of nutrition did not adversely affect libido of the boars as judged by their breeding behavior during a seven-day test period.

This study demonstrates that development and functional capacity of the reproductive system of boars are relatively resistant to the effects of underfeeding which resulted in reduced body growth and size.

¹ This investigation is in connection with a project of the Kentucky Agricultural Experiment Station and is published by permission of the Director.