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Short-Term Effects of Divergent Selection for Parasite Resistance in F1 Kiko × Boer Doe Progeny
Future prospects of the goat industry appear optimistic as demand for goat meat has consistently overwhelmed domestic supply in recent years. However, parasitism is arguably the most serious economic restriction limiting goat production in the U.S. One approach to combat internal parasites is utilizing the host animal’s natural immunity in a selection program to increase the level of parasite resistance in a herd. The objective of this study was to evaluate the short-term effects of divergent selection for parasite resistance in F1 Kiko × Boer doe progeny. First generation Kiko × Boer progeny (n = 41) from two lines of does selected for high resistance to internal parasites (HL; n = 22) or low resistance to internal parasites (LL; n = 19) were compared. Fecal egg counts (FEC), FAMACHA© scores (FAM), and packed cell volumes (PCV) were measured at weaning, 28 d post-weaning, pre-breeding, during breeding, and at end of breeding. No differences (P ≥ 0.12) were found between HL and LL for FEC, FAM, or PCV at all measurement times except for PCV at 28 d post-weaning, which tended (P = 0.09) to be higher for HL vs. LL. Consequently, number of times dewormed and survival rates were similar (P ≥ 0.19) between lines. Reproductive rate, litter size, kidding date, and F2 kid birth weight did not differ (P ≥ 0.23) across lines. A sex effect (P ≤ 0.04) was detected, with males weighing more vs. female kids. Correlations between FEC and FAM were significant (P < 0.05) and positive for LL (R = 0.26), but were insignificant (P = 0.74) for HL; correlations between FEC and PCV were significant (P < 0.01) and negative for LL (R = -0.30), but were insignificant (P = 0.25) for HL; correlations between FAM and PCV were significant (P < 0.001) and negative for LL (R = -0.46) and tended to be significant (P = 0.10) and negative for HL (R = -0.16). Short-term effects of divergent selection for parasite resistance resulted in minimal differences in parasitism, survival rate, and reproductive performance. Associations between indicators of parasitism were moderate in some cases, but varied by doe line. This research is part of an ongoing long-term selection project for parasite resistance.
Keywords: divergent selection, F1 Kiko × Boer, parasite resistance