Effect of dietary protein on responses of lambs to repeated Haemonchus contortus infection

Effect of increased dietary protein supply on repeated Haemonchus contortus infection was assessed in growing native Chokla lambs in the semi-arid Rajasthan state of India. In a 2 x 3 factorial design, 48 Chokla lambs (4-5 mo, 14.9 +/- 1.0 kg) were distributed in two main groups (24 animals each). control (C) and infected (I) and were fed on complete diets (at 3% of live weight (LW)) with three levels of protein (CP, g/kg dry matter) high (HP; 150), moderate (MP 115) and low (LP; 95), thus constituting six treatment groups HPC, HPI, MPC, MPI, LPC and LPI having eight animals each. Lambs of infected groups were drenched with 200 infective larvae (L3)/kg LW after one month of experimental feeding, and subsequently with 300 L3/kg LW three times a week for 13 consecutive weeks. The experiment lasted for 21 weeks with record of feed intake and weekly LW change along with collection of blood and faecal samples for analysis. Body condition score (BCS) of animals were recorded at the end of infection regime. A digestibility trial was conducted during 13 weeks of infection to assess plane of nutrition. The mortality was greater and adverse clinical signs such as inappetance, weight loss and submandibular oedema were more frequent in the LPI group. The LPI group also had more severe anaemia, hypoproteinaemia and hypoalbumenaemia. Faecal egg counts, worm burden, establishment of larvae and fecundity were not significantly (P>0.05) different between the groups of infected lambs. However, higher protein levels in the diet enhanced feed and nutrient intake and supported higher LW gain with better feed efficiency and improved BCS. It may thus be concluded that lambs on LP diet were less able to withstand the patho-physiological effects of H. contortus than lambs on MP and HP diets. (C) 2012 Elsevier B.V. All rights reserved.