@conference {40537,
	title = {A comparison of carcass and meat characteristics and organ weights of castrate and entire male buffalo and cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {53},
	year = {1993},
	month = {Jan},
	pages = {407-412},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Research has shown that sheep from a Massey University flock selected  for increased fleece weight (FW) for thirty-six years have higher faecal egg  counts (FEC) than unselected controls (C). The purpose of this trial was to  determine whether differences in FEC between FW and C sheep accurately  reflected differences in adult worm burdens. In addition levels of mucosal  mast cells, and their relationship with worm burden in each line were examined.   Thirteen one year-old rams from each flock were housed indoors and  artificially infected with larvae of three species of nematode parasite:  Haemonchus contortus, Ostertagia circumcincta, and Trichostrongylus  colubriformis. FECs were monitored and adult worm burdens, and levels of  mucosal mast cells, determined following slaughter 28 days after infection.   FECs were higher in FW than C sheep (4204 vs 300 epg, p<0.0001), as were  numbers of adult Haemonchus (1151 vs 249, p<0.01) and  Ostertagi (2268 vs 600, p<0.05). Numbers of Trichostrongylus  (5838 vs 5266) and total worm burden (9257 vs 6115) were not significantly  different between lines. A {\textquoteright}Total Pathogenic Index{\textquoteright}, calculated from the  number of parasites of each species present in the total burden, was higher  in FW than C sheep (3.8 vs 1.5, p<0.005).   The regression coefficient relating FEC to worm burden was larger in FW than  C sheep (0.35 vs 0.05 eggs per g faeces/worm, p<0.01). Levels of mucosal  mast cells did not differ significantly between lines, but were inversely related  to number of worms in FW sheep. There was no such relationship in C sheep.   It is concluded that while the large differences in FEC between lines  overestimates the difference in total worm burden, FW sheep do carry  significantly more worms of the abomasal species H. contortus and O.  circumcincta than C sheep. FW sheep are able to maintain superior wool  production in spite of this potentially more pathogenic worm burden. The  mucosal mast cell response to parasitic infection also appears to have been  changed by selection.  },
	issn = {1176-5283},
	author = {Purchas RW and Thomson NA and Waghorn GC and Death AF}
}
