Abstract:
Proc. Aust. Soc. Anim. Prod. Vol. I6 RELATIONSHIPS BETWEEN ADAPTIVE TRAITS AND WEIGHT IN DIFFERENT CATTLE BREEDS B.M. BURNS*, C.J. HOWITT and C.R. ESDALE* SUMMARY The effect of sire on liveweight, helminth egg per gram (epg) counts, tick counts and rectal temperature together with correlations between these adaptive traits were estimated over three breeds of cattle. Sire effects were significant for live weight, endo- and ecto- parasite counts in the Hereford (H) and Africander-Hereford (AH) groups but not in the Simmental (S) group. Rectal temperature was significantly affected by sire only in the H group, but ambient temperatures were probably too low to cause a sufficient rise in rectal temperature in the AH to reliably discriminate between animals. Correlations between the adaptive traits and with live weight were significant for only rectal temperature with live weight and tick count (r = 0.34 and 0.30, respectively P<O.O5) in the H group but not in S or AH groups. (Key words: Sire effects, live weight, rectal temperature.) INTRODUCTION importance of environmental adaptation in beef cattle reared in and sub-tropical environments is well documented (Frisch and Vercoe However, there is limited information to define the extent of the 1982). correlations between adaptive traits (e.g. heat tolerance, tick and helminth resistance) and with live weight in various environments. Knowledge of these correlations for different environments in the tropics and sub tropics is needed to improve the efficiency of selection programmes for beef herds. Preliminary results from an experiment designed to estimate correlations between adaptive traits and with live weight are presented in this paper. MATERIALS AND METHODS Location and experimental animals The experimental cattle were reared at Brigalow Research Station, Theodore. Location, pastures and herd management have been described elsewhere (Rudder et al. 1 98 6) l ecto- and endo- parasite counts, The tropical Fifty-nine of the heifers (H) were from Hereford dams and were by four generation local commercially bred Hereford sires and two F5 et seq. Herefordxshorthorn sires bred in a random selection herd by CSIRO, Rockhampton, There were no objective comparative performance data available for Queensland. Fifty-two of the heifers (S) were from dams of half and higher these sires. grade Simmental (the residue was Hereford) breeding and by seven Simmental sires These sires were that had live weight for age ratios ranging from 93 to 111. bred in mid-western New South Wales. Sixty-two of the heifers (AH) were from Fl et seq. generation Africander-Hereford dams by six locally bred AfricanderHereford sires that had yearling live weight for age ratios ranging from 89 to * t Brigalow Research Station, D.P.I., M.S. 586, Theodore, 4719, Queensland. Biometry Branch, D.P.I., P.O. Box 46, Brisbane, 4001, Queensland. 163 Proc. Aust. Soc. Anim. Prod. Vol. 16 105, helminth egg per gram (epg) counts [log IO (count + l)] ranging from log 0.94 to 2.80, and tick counts ranging from log 0.00 to 1.23. Experimental procedures Tick resistance was estimated by two artifical infestations of c. 20,000 larvae on January 4 and January 24, 1985 followed by counts on day 20 and 21 after infestation. Tick counts, by four experienced operators, were based on the number of female ticks in the size range 4.5 - 8 mm. Helminth epg counts were estimated by standard laboratory techniques (Whitlock 1948) from faecal samples taken on August 21, September 12, October 21 and December 6, 1984. (Model BAT-12) Microprobe Rectal temperatures were recorded using a Baileys Electronic Thermometer with a short response time. Ten recordings were used to estimate animal variation and were taken between January 2 and February 15, Ambient temperatures at the yards ranged from 39.3OC to 34.1�C when these 1985. recordings were made. Yearling live weight was adjusted to the average age of the group. Helminth epg and tick counts were transformed to log 10 (count + 1) and then recordings were averaged. Rectal temperatures were averaged over the 10 recordings. These variables were analysed separately for each of the three breed groups using standard analyses of variance for unequal subclass numbers. The sire by age of dam The factors used were sires and age of dam classes. interaction and age of dam effects were non-significant except for age of dam effects on yearling live weight and rectal temperatures of the H (P < 0.05). Correlations were estimated between these four variables after removing the effects of sires. RESULTS AND DISCUSSION There was significant variation amongst the H and AH sires for live weight The variation and parasitic burdens but not amongst the S sires (Table 1). amongst the H and AH sires is consistent with previous work by Seifert (1971a, 1977) on variation within breeds for tick counts, liveweight for age and 1975, Turner (1984) reported sire variation in helminth epg counts, respectively. rectal temperatures and the results from the H group agree with this finding. The absence of significant differences amongst the S sires is probably a reflection of the sires sampled rather than real differences in variation Lack of between sires in this breed when compared with other breeds. discrimination between the AH sires is probably because these cattle were not heat stressed. Turner (1984) indicated that mean rectal temperatures of >39.5% were needed to discriminate reliably between animals. These data generally support the findings that genetic variation exists between sires for live weight for age, endo- and ecto parasitic counts and rectal temperatures. Correlations between adaptive traits (Table 2) were low and not significant (P > 0.05) except for rectal temperature with tick counts and live Past research has shown that within breeds the weight in the H group. relationships between parasite burdens and production losses have not been consistent. Seifert (1971b), Turner and Short (1972), Sutherst et al. (1979) and O'Rourke (1982) found no significant relationship between tick count and growth, while Frisch and Vercoe (1982) did. Turner and Short (1972) and Frisch and Vercoe (1982) observed no significant relationship between helminth epg counts and growth, but Seifert (1971b) found a correlation between helminth epg counts and growth rate. The variable relationship between individual resistance and production may be due to level of parasite infestations and reliability of 164 Proc. Aust. Soc. Anim. Prod. Vol. 16 Table 1 Live weights, helminth epg and tick counts, significance of sire effects within breeds rectal temperatures and t Transformed as log 10 (count + 1) with back transformed means in brackets. tt Standard deviation. Table 2 Correlations between yearling live weight, mean helminth epg and tick counts and rectal temperature 165 Proc. Aust. Soc. Anim. Prod. Vol. 16 assessment of resistance. The reliability of helminth epg counts as an index of resistance has not been generally established (Seifert, 1971b). Turner (1984) found that the relationships between growth rate and rectal temperature were similar in different breeds of cattle. O'Kelly and Spiers (1984) demonstrated a negative phenotypic correlation between rectal temperature and tick resistance, the mechanism of which was not clear. If the index of productivity is live weight,in environments where this factor is not influenced by adaptive traits, there appears to be little value in using these traits in selection programmes. However, in environments of higher nutritional, parasitic and temperature stresses high correlations may be Therefore, these correlations should be estimated over a number of present. calf crops to obtain a range of seasonal conditions. ACKNOWLEDGEMENTS Thanks are due to colleagues who assisted in the collection of data and preparation of this paper. REFERENCES FRISCH, J.E. (1981). J. Agric. Sci. 96: 23. FRISCH, J..E., and VERCOE, J.E. (1982). World Congress on Genetics Applied to Livestock Prod., 2nd, Madrid pp 307-321. O'KELLY, J.C. and SPIERS, W.G. O'ROURKE, P.K. (1982). (1984). J. med. Entomol. (In press.) Proc. Aust. Soc. Anim. Prod. c 305. 14: and BURROW, H.M. (1986). RUDDER, T.H., SEIFERT, G.W. Prod. 16: (In press). SEIFERT, G.W. (1971a). Proc. Aust. Soc. Anim. Aust. J. Agric. 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