Semester

Fall

Date of Graduation

2022

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Scott Bowdridge

Committee Co-Chair

Robert Dailey

Committee Member

Robert Dailey

Committee Member

Eugene Felton

Committee Member

Scott Greiner

Committee Member

Domingo Mata–Padrino

Abstract

Nutritional impact of internal parasitism, specifically Haemonchus contortus (Hc), is a significant contributor to production losses in small ruminants. Both chronic and subclinical infections generate millions of dollars of losses worldwide. Understanding the nutritional impact of Hc on lamb performance is crucial in determining the additional nutrient requirements of infected individuals. The aim of this study was to evaluate nutritional impact of Hc on infected Katahdin lambs with extensive genetic selection for parasite resistance and susceptible Suffolk lambs. Growth, feeding behavior, and feed efficiency (RFI. F:G) were evaluated during artificial Hc infection. Katahdin ewes from the Virginia Tech Southwest Agriculture Research and Extension Center in Glade Spring, Virginia were mated to rams (n=8) selected for parasite resistance genotype (PFEC EBV). A subset of lambs was selected for evaluation in a feedlot environment and transported to West Virginia University’s Animal Science Farm in Year 1 (Y1) and Year 2 (Y2). Purebred Suffolk lambs were selected from the West Virginia University flock and reared in parasite free conditions (n = 9). Additional lambs were sourced from purebred Suffolk flocks in West Virginia and had parasite exposure while reared on pasture (n = 31). Lambs sourced from outside flocks were transported to West Virginia University’s Animal Science Farm, acclimated to feed, and monitored for FEC. All lambs were fed a complete pellet (16% CP) ad libitum while individual intake was measured with a modified GrowSafe™ system. Half of the Katahdin lambs from each sire PFEC EBV group were infected with 5,000 Hc L3 larvae and observed for 5 weeks in Y1 and 6 weeks in Y2 alongside uninfected contemporaries. Artificial Hc infection resulted in lambs becoming moderately infected with FEC ranging from (0 – 1208 eggs/g). Half of the Suffolk lambs (n=20) were artificially infected with 5,000 Hc L3 larvae in a 5wk primary and 5wk secondary infection with a 2wk rest period in between. Artificial infections were significant (P < 0.05) between infected and uninfected lambs in all experimentation excluding the Suffolk secondary infection (P = 0.71). Infection intensity measured by PCV remained moderate with values remaining above level of concern. Feed efficiency measured in all feeding trials was measured by RFI and F:G. Differences in feed efficiency was not detected between infection status; however, sire was a significant factor affecting feed efficiency of Katahdin progeny (P < 0.01). Feeding behavior was measured for both duration and frequency during infection in all years. Behavior was not impacted by infection status in Katahdin lambs; however, sex has a significant effect on behavior. Ram lambs exhibited greater duration per visit than ewe lambs in Y1 and Y2 (89.7 vs. 78.6 seconds/visit, 122.8 vs. 82.4 seconds/visit respectively; P < 0.05). Increased feeding durations for ram lambs resulted in rams exhibiting reduced frequency of feeding events compared to ewe lambs in Y1 and Y2 (36.3 vs. 43.9 visits/day, 25.8 vs. 40.8 visits/day respectively; P < 0.01). Increased duration of feeding/visit in ram lambs also resulted in greater feed intake/visit compared to ewe lambs in Y1 (58.7 vs. 42.7 g/visit; P < 0.0001). Suffolk lambs exhibited feeding behavior with significant differences between infection status. Infected lambs had significantly lower duration/visit than uninfected lambs (116.24 vs. 133.64 seconds, respectively; ± 6.11, P < 0.05). Infection status did not impact total feeding duration with daily feeding duration remaining similar between infected and uninfected lambs. Sex was significant for daily feeding duration with ewe lambs spending 638.59 seconds longer feeding than males. Data suggests in susceptible breeds of sheep with moderate Hc infections, feeding behavior is significantly impacted. additionally, lambs with moderate Hc infections do not experience detectable changes in lamb performance for growth, feed efficiency, and PCV while receiving ad libitum access to feed.

Embargo Reason

Publication Pending

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