Effect of three feeding levels on the pathogenesis and establishment of Haemonchus contortus in parasite-naïve Pelibuey hair sheep lambs during their first infection.

This study evaluated the effect of three feeding levels on the pathogenesis and establishment of H. contortus upon the first infection of parasite-naïve Pelibuey hair sheep lambs. Forty-two 6-month-old hair sheep lambs (24 ± 4 kg) raised parasite free from birth were used. The lambs were assigned to 3 groups (n = 14), and each was fed a diet designed for different daily weight gain (DWG): 75 g/d (Diet 1), 125 g/d (Diet 2) and 200 g/d (Diet 3). After four weeks of diet adaptation, 10 lambs/group were infected with 450 L3H. contortus/kg BW (infected), and 4 lambs/group were kept parasite-free (NInf). DWG, hematocrit (Ht), hemoglobin (Hb), peripheral eosinophils (EOS), IgG concentration against H. contortus, and eggs per gram (EPG) of feces were measured in each lamb from day 14 before infection until day 29 postinfection (PI). On day 29 PI, the lambs were slaughtered to determine the total number of adult parasites (TAW), the length of the female worms, and the number of eggs in utero (EIU). Each group reached the expected DWG (P = 0.001), and there was no effect of infection or the diet × infection interaction. Ht was lower in infected lambs than in NInf lambs, and this difference was significant for animals on Diets 1 and 2 (P = 0.044). From day 14 PI onward, Hb was lower in the infected lambs than in the NInf lambs (P = 0.001). Furthermore, compared with NInf lambs, the infected lambs had higher EOS from day 7 PI and higher IgG from day 14 PI. Neither EOS nor IgG were affected by diet. Lambs on Diet 3 had lower EPG during patency than those fed Diets 1 or 2 (days 25 and 28 PI; P = 0.002). Furthermore, lambs fed Diet 3 had lower TAW (Diet 1 vs 3 P = 0.037; Diet 2 vs 3 P = 0.049) and EIU (P = 0.004) than lambs fed Diet 1 or 2. Lambs were resilient to infection regardless of diet. Although EOS and IgG were higher in all infected animals than in Ninf animals, EPG, TAW and EIU decreased only in lambs fed Diet 3. Thus, a diet targeting a DWG of 200 g/d can significantly limit the establishment of H. contortus in Pelibuey lambs infected for the first time.

Nitrogen retention in hair sheep lambs with a gradient of Haemonchus contortus infection.

The impact of Haemonchus contortus infections on nitrogen retention (NR) of hair sheep lambs is unknown. This study estimated the feed intake, digestibility, NR, haematocrit (HT), and their relationship with the gradient of H. contortus infection in hair sheep lambs. Twenty-four hair sheep lambs, 3-4 months old, reared parasite-free were used (live weight (LW) 16.7 ± 1.7 kg). Six lambs were kept parasite-free, nine lambs received a dose of 300 H. contortus infective larvae (L3)/kg LW, and the remaining nine lambs received 500 H. contortus L3/kg LW. Infection doses ranged from 3870 to 9,500 L3. Lambs were individually fed for an average daily gain (ADG) of 100 g. On days 1 (P < 0.01) and 7 (P < 0.001) post-infection (PI), the L3 doses were positively associated with HT, possibly due to platelet recruitment. On week 1 PI, the infection (L3) reduced the crude protein (CP) intake (g/kg metabolic LW) (P < 0.05). A reduction of 1% HT corresponded to 1200 eggs per gram of faeces (EPG) for day 21 PI (P < 0.05), 2300 EPG for day 28 PI (P < 0.001), 2400 EPG for day 35 (P < 0.001), and 1300 EPG for day 41 PI (P < 0.001). However, the HT levels were never lower than 21 %. A lower CP digestibility was associated with EPG only on week 5 PI (P < 0.05). There was no significant association between EPG, Total egg in faeces, or worm burden (WB) with intake, dry matter digestibility (DMD), ADG or NR. The NR of lambs was positive along the different weeks of study irrespective of infection level. The WB was negatively associated only with HT on day 41 PI (P < 0.001), where a 1 % HT reduction was estimated for every 257 worms hosted. In conclusion, no relationship was found between H. contortus infection and DMD, ADG or NR in hair sheep lambs. The cost of H. contortus infection resulted only from the HT reduction and depended on the gradient and stage of the infection.