A comparison of semen quality in Brahman cross and Africander cross bulls.

Abstract

A COMPARISON OF SEMEN QUALITY IN BRAHMAN CROSS AND AFRICANDER CROSS BULLS H.R. CHRISTENSEN* and G.W. SEIFERT** Summary Semen collected from Brahman cross and Africander cross (Belmont Red) bulls in Central Queensland was examined to assess the proportion of live sperm and the proportions of abnormal sperm. Brahman cross bulls produced a lower proportion of live sperm than Africander cross bulls although individual Brahman cross bulls were equal to the best of the Africander cross bulls, Significant breed differences were found in the proportion of total minor abnormalities with AX bulls producing fewer than BX bulls, Proportionately more AX bulls than BX bulls produced semen with above minimum levels of per cent live and with fewer than maximum levels of some abnormalities, The implications of these findings when selecting bulls on semen quality are discussed, I* INTRODUCTION . Substantial gains in production can be achieved by systematic utilization of crossbreeding in Northern Australia (Piper and Latter 1974)o Zebu cattle have already gained popularity in that area, where in Central and Northern Queensland over 5& of breeding bulls in 1973 were Brahman or Brahman derived and 39 holdings carried some Africander breeding stock (Anon, 1973)0 Although zebu introductions in Australia have largely been used to create new breeds (Piper and Latter 1974) there is an increasing trend towards systematic crossbreeding (Rudder, Perso com.13~)~ Limited research has shown that the fertility of Brahman crosses is lower than that of Africander crosses in the F2 generation (Seifert and Kennedy 1972; Seebeck 1974) and part of the decline in fertility is attributable to the bull (Seifert, unpublished data), Semen quality is a component of bull fertility and two measures used to assess semen quality are the proportion of live sperm and the proportion of morphologically abnormal sperm in the semen. This paper records differences observed in these measures between two crossbre,eds, Brahman cross (BX) and Africander cross (AX), II, MATERIALS AND METHODS -Semen samples were collected from A3 and BX bulls on the National Cattle Breeding Station, **BelmonV, Rockhampton, during 1973, 1974 and 19750 The derivation of the crossbred bulls and the environment of the station were described by Kennedy and Turner (1g5g)o The bulls used had been selected from the bull calf drops in 1971, 1972 and 1973 on the basis of their growth performance and tick resistance,, At the time of * CSIRO Division of Animal Health, Tropical Cattle Research Centre, Rockhampton, Qld. ** CSIRO Division of Animal Genetics, Tropical Cattle Research Centre, Rockhampton, Qld0 193 semen collection the average age of the bulls was 24 months in 1973, 22 months in 1974, and 18 months in l975o The bulls were run together from birth and were sampled as they came up the crush. Semen was collected using manual massage of the ampullae per rectum after the methods of Goodwin (197'0) and Parsonson, Hall and Set-t= (lg71)o The density ofthe semen sample collected was assessed visually and scored I-5, very dense semen with visible motion being scored as so The percentage live sperm in each sample was assessed by counting 100 sperm cells on an eosin-nigrosin stained smear using stain prepared according to Swanson and Bearden (1951). The frequencies of sperm,abnormalities were assessed by counting 100 sperm cells on india ink stained smears. The proportion of live sperm, the proportion of each ?f 23 individual types of sperm abnormality, the proportions of major and minor groups of abnormalities as classified by Blom (1972), and density of the semen sample were recorded. The proportions were transformed to the angle = arcsin\/proportion (Snedecor 1967) and were analysed by the least squares method (Harvey 1960) using the following model: 1110 RESULTS AND DISCUSSION Table 1 shows the analysis of variance for the angular transformations of proportation of live sperm and minor abnormalities. Analysis of variance for proportion live sperm and proportion minor abnormalities 194 (a) Proportion of live sperm The BX bulls had fewer live sperm than the AX bulls, but one BX bull produced semen with a higher proportion live sperm t n the best of its contemporary AX bulls, However significantly more (X 9 Pc~OOI) BX t bulls produced semen with less than 7% live sperm than did AX bulls, A level of 6% live sperm has been suggested as the minimum acceptable level f o normal bull semen (Galloway 1974) and more BX bulls than AX bulls (XT 9 P<O,l) produced semen with less than 6% live sperm. In all years the BX had lower $ live sperm than the AX (Table 2)p but this difference was particularly large during 1973, causing a significant interaction, The reason for this large difference during 197'3 has not been determined, TABLE 2 Least squares means for percent live sperm and percent minor abnormalitiest t-Includes: elongated narrow, microcephalic, macrocephalic, double, and detached normal heads; distal droplets, bent tails and detached acrosome, These results suggest that when selecting bulls on the basis of semen quality the acceptable proportion of live sperm may need to be lower for BX bulls than for AX bulls, Preferably it may be necessary to sample proportionately more BX bulls than AX bulls to obtain the required number with a common acceptable proportion of live sperm. (b) Proportions of abnormal sperm There were significant @~~05) breed differences noted in the proportion of total minor abnormalities, AX bulls producing fewer abnormalities than the BX bulls (Table 2), Year effects were highly significant for a number of abnormalities indicating that environmental effects could be important sources of variation. Although there was no significant breed differe ce for individual abnormalities in all samples, significantly fewer (Xs 9 P Co05) BX bulls than AX bulls produced semen with less than 1% bent tails; less than 15% tailless heads; and less than 4% proximal droplets, The levels examined are the maximum acceptable normal levels suggested by Galloway (1974)o Thus , proportionately nn,reBX bulls than AX bulls would be rejected if a common acceptable level of abnormalities was used, 195 These results support the work of Chenoweth and Osborne (1975) that Brahman cross bulls have a poorer reproductive function than Belmont Red bulls although some individuals of the BX genotype are equal to the best of the.Belmont Red genotype, . IV0 ACKNOWLEDGEMENTS The able technical assistance of Ms. Mitchell and Messrs, Bean, Kidd and Short plus the efficient handling of the bulls by the 'Belmont*' staff are gratefully acknowledged, vo REFERENCES Anon0 (1973) Blom, E, (lYi'2)o Atti de1 VII Simposio Internazionale de Zootecnia, Milano, p,125-139, Chenoweth, PoJe, and Osborne, HoGo (lg75)o Australian Veterinary Journal, 51: 405. Galloway, D.BeTl974)e *'Bull~~~~ Proceedings od Post Graduate = Veterinary Scienc' Committee (University of Queensland: Brisbane), Goodwin, DOE0 (1970). Journal of the American Veterinary Medical Association, 1 : 831, e Harvey, WeRe (1960FU.SoD9A0, AoReSo Bul. 20-8, Kennedy, J.F@, and Turner, H.eo (1959). C,S.I,R,O,'Division of Animal Health and Production Report No. 8 (Series S.W,-3)o Piper, LoROt and Latter, BOD.Ho (19'4). Proceedings of the Australian Society of Animal Production, 10: 80 Parsonson, IoMO, Hall, CoEO, and Sezergren, `Jo (lg71)o Journal of the American Veterinary Medical Association, 158: l75o Seebeck, ROM0 (1973), Journal of Agricultural~ience, Cambridge, 81: 2530 . Seifez, G,Wo, and Kennedy, JoFo (lg72)o Proceedings of the Australian _ Society of Animal Production, 2: 143 Snedecor, G,W,, and Cochran, Go ($7). *'Statistical Methods*' 6th ed'. (Iowa State University Press: Ames). Swanson, EoWo, and Bearden, HoJo (1951). Journal of Animal Science, 10: M 981. 'Beef Cattle Breeds 31 March 1973 QueenslandTt9 Report l Q161/730 Bureau of Census and Statistics, Brisbane, 196