Proc. Aust. Soc. Anim. Prod. Vol. 19 CONTRACT REVIEW TWINNING IN CATTLE

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1 Proc. Aust. Soc. Anim. Prod. Vol. 19 CONTRACT REVIEW TWINNING IN CATTLE L. J. CUMMINS Dept of Food and Agriculture, Pastoral and Veterinary Institute, PB 105, Hamilton, Vic INTRODUCTION The biological efficiency of traditional systems of beef production is low due to the low reproductive rate and the high proportion of total energy which is required for maintenance of the breeding herd. Dickerson (1978) estimated that 56% of the total feed energy intake for adult and market cattle is required solely for body maintenance (the non-productive energy requirement rises to 73% when replacements are considered). He also estimated that increasing reproductive rate from 0.8 to 1.8 could reduce the feed energy required by 25% per kg of edible meat protein. Preliminary experimental results from embryo transfer (Dickerson et al. 1988) and genetic studies (Gregory et al. 1990) show that gains of this order seem possible. The Meat Research Corporation (MRC) has sponsored a co-ordinated project on the application of advanced reproductive technology in temperate zone cattle which has focussed on beef twinning. While twinning has been the subject of a number of reviews (e.g. Hendy and Bowman 1970, Gordon 1983 and Morris 1984), the major stimuli for the current project were the finding that immunisation with ovarian follicular fluid (Cummins et al. 1986) and purified inhibin (Bindon et al. 1988) could stimulate multiple ovulation in cattle and from the development (Lu et al. 1987) and cornmercialisation of in vitro fertilisation and embryo transfer to induce twinning by Ovamass Ltd in Ireland. Alternative pathways to twinning are shown in Fig. 1. Twinning is relatively rare in cattle and producers generally have had little opportunity to learn how best to manage twin-bearing cows. Successful application of a twinning technology would require generally improved management and nutrition (Gordon et al. 1962) and a clear demonstration of the profitability of twinning under local conditions. This contract gives preliminary results from several studies on twinning in beef cattle. 438

2 Proc. Aust. Soc. Anim. Prod. Vol. 19 HORMONAL INDUCTION OF TWINS IN BEEF CATTLE B. M. BINDON and M. A. HILLARD CSIRO Division of Animal Production, Armidale, N.S.W Serious attempts to induce twinning in cattle by treatment with exogenous gonadotrophin began nearly 30 years ago (Gordon et al. 1962) when dairy cattle were given a single injection of pregnant mare s serum gonadotrophin (PMSG) during the follicular phase of the cycle. The next development refined the PMSG treatment schedule to include an injection on days 3 (1500 iu) and (2000 iu) of the oestrous cycle. In 2 replicates of the same design (Turman et al and Johnson et al. 1973) between 1824% of treated cows produced multiple births. However, of these 46% were triplets, quads or quintuplets with low birth weights and survival. Further investigations examined the use of partially purified porcine follicle stimulating hormone (FSHP; Armour) injected in divided doses at known stages of the oestrous cycle (Vincent and Mills 1972). This strategy is simply a low dose version of the superovulation program used for embryo transfer donors. Fertility at the synchronised oestrus was poor, but a useful (12%) proportion of twins resulted, with good survival. Recently, we have evaluated highly purified ovine FSH (Embryo S; Bunge Australia; LH contamination < 0.1%) for induced twinning. Following dose response investigations (Bindon et al. 1986) 3-year-old Hereford heifers were injected with 8-10 mg of this product, given as 8 injections over 4 days beginning on day 8-10 of a synchronised cycle, with luteolysis induced by prostaglandin injection on the morning of the third day. The mean ovulation rate of was close to the desired level, but about half the treated animals had a single ovulation and some had ovulation rates outside the desired range of 2-4. With present knowledge it is difficult to see how the precision of this technique could be improved. Simply increasing the dose of FSH will not help because a larger proportion of the population will then have ovulation rates in the undesirable high range. It is likely that increased precision will only come when we have a better understanding of the feedback and intraovarian regulatory substances responsible for ovarian control in the bovine. When cattle of mixed age (including 15 month old heifers) were treated over 4 days as above with a fixed dose of 8.0 mg ovine FSH an ovulation rate distribution, fertility rate and calving rate as shown in Table 1 was observed. These are synchronised females naturally mated only at the synchronised oestrus. With ovulation rate in the range 2-4, fertility is comparable to that of single ovulators and 27% of treated females produce multiple births. When ovulation rates exceeded 4 (largely confined to the 15month-old heifers), fertility was poor and few cases of twins resulted. Table 1. FSH-induced twin pregnancies in synchronised, mixed-age beef females treated with 8.0 mg ovine FSH In this experiment, from 109 animals treated, 34 calved and 15 produced multiples (12 sets twins, 3 sets triplets). If it can be assumed 75 cows which did not conceive to the treatment cycle would have normal fertility at subsequent cycles (say 0.9 calves born per cow joined), then the treatment would yield an increase of around 20 extra calves per 100 cows treated compared to the average calf turnoff from beef females. Such a result may not be sufficient to offset the costs of the synchronisation treatment, the FSH injections and the additional management costs of rearing calves arising from mu1 tiple births. Twins by inhibin vaccine A new approach to induced twinning is to develop a vaccine against the protein hormone inhibin, a natural peptide produced by the ovary, which inhibits FSH synthesis. Preliminary studies (Bindon et al. 1988) confirm that immunisation of cattle against native ovine inhibin causes increased ovulation rate. 439

3 Immunogens based on synthetic fragments of the alpha-inhibin chain are not successful in the cow even though they are most effective in sheep (Bindon and Piper 1989). Recent studies in collaboration with Biotechnology Australia at this laboratory have evaluated a range of recombinant inhibin immunogens. A prototype vaccine for twinning is now ready for field evaluation. Current experiments will resolve whether the vaccine requires administration at a known stage of cycle and if acceptable frequencies of twin births (without undesirable larger litters) follow from its use in beef cattle. INDUCED TWINS BY EMBRYO TRANSFER L. J. CUMMINS*, A. J. CLARK*, I. K. MCLEODA, J. E WILKINSB, I? J. WILLIAMSONB, D. W HENNESSYB, M. A. HILLARDc, R. L. PASHEND and M. D. DARROWD *Dept of Food and Agriculture, Pastoral and Veterinary Institute, PB 105, Hamilton, Vie BNSW Agriculture, Agricultural Research and Advisory Station, Grafton, N.S.W CCSIRO Divison of Animal Production, Armidale, N.S.W DAnimal Genetic Services, 26 Caraar Creek Lane, Mornington, Vie We used commercially available superovulation and embryo transfer techniques to generate the twins required for the production experiments in this project. This was relatively expensive but developments in embryo multiplication and transfer may eventually reduce these costs.this report summarises the responses, but since the work has involved a range of treatment schedules a detailed statistical analysis accounting for all effects will be reported later. Embryos were collected from Hereford heifers, once calved at Grafton and non-parous, months old, at Hamilton. At each site heifers were treated and flushed, some on several occasions. Oestrus synchronisation utilised either prostaglandins (mainly Estrumate - Pitman Moore) or intravaginal progesterone releasing devices (Eazi-breed CIDR B Carter Holt Harvey Plastic Products) plus prostaglandins. The duration of CIDR treatment was either 7 or 14 days. In 85% of cases ovarian stimulation utilised preparations in standard use and at standard dose rates. FSH-P (Heriot), Folltropin-V (Vetrepharm) and Embryo-S were given as intramuscular injections, twice daily over 4 days in a declining dose regime. The other 15% of cases used these or other preparations in experimental schedules. Oestrus was detected, mostly on the day after final FSH treatment, and the cows artificially inseminated twice with Murray Grey semen. Cows were flushed 7 days later. Table 2. Mean superovulation response per cow flushed The responses in different runs were quite variable, but overall, standard treatments yielded 3.9 useable embryos per cow flushed while the experimental treatments only yielded 2.2 per donor. The variability of response to superovulation is typical of that obtained in the industry, but the useable embryo yield seems slightly lower than often quoted (e.g. Seidel 1989 indicates an average of 6 useable embryos is typical). 440

4 The recipient cows were Hereford x Angus or Hereford x Friesians which had calved previously. These cows were synchronised using prostaglandins or prostaglandins plus CIDR B s with a 7 day period of insertion. These cows were inseminated or mated naturally to Hereford bulls. On day 7 post mating, the cows were examined to determine the side of ovulation and suitability for transfer and an embryo transferred to the contra-lateral uterine horn. Both freshly collected and frozen/thawed embryos were transferred with no obvious differences in success rate of twin conception. Pregnancy rate and foetal numbers were determined using real time ultrasound between days 35 and 100 of pregnancy. These have been confirmed by calving results as they became available. Over the years 1989, 1990 and 199 1, data are available from 48 1 cows which received supplementary embryos at Grafton and 541 at Hamilton. At Grafton 65% of these cows calved and 56% of the cows calving produced twins. The comparable values at Hamilton were 63% of cows calved and 52% of those produced twins. These results show there is considerable scope for strategies to reduce embyonic loss. Overall, 35% of the cows receiving supplementary embryos have produced twin calves. These results are consistent with published data for such synchronised mating/transfer systems (Gordon 1983). Non-pregnant cows in this system could be re-mated in a similar way using residual synchrony or following re-treatment with CIDRs or simply being placed with bulls for natural mating. For comparison with Bindon and Hillard s predicted FSH response, we have assumed that non pregnant cows following treatment were joined naturally and had normal fertility at subsequent cycles (0.9 calves born per cow joined). Only 73% of cows which started a treatment cycle received a transferred embryo (due to failure to detect oestrus or rejection at transfer because of presumed inadequate luteal function). Taking these and the non-pregnant transferred cows into consideration we can predict the final outcome of a 1 round supplementary embryo transfer program plus natural mating to be 120%. This increase of 30 calves per 100 cows joined represents a significant increase in the fertility of the beef breeder herd. CALVING PERF ORMANCE IN TWINNING HERDS I. K. MCLEOD*, A. J. CLARK*, L. J. CUMMINS*, J. E WILKINSB, D. W HENNESSP, C. M. ANDREWP and I? J. WILLIAMSOP *Dept of Food and Agriculture, Pastoral and Veterinary Institute, PB 105, Hamilton, Vie. BNSW Agriculture, Agricultural Research and Advisory Station, Grafton, N.S.W Complications during calving, the lower birth weight of twins, and poor dam-offspring bonding are seen as potential problems associated with multiple births. Twin calving has also been associated with a high incidence of retained placentae (Hendy and Bowman 1970). Thus the potential increase in productivity and efficiency offered by multiple births may be eroded by reduced calf survival and increased labour costs. The performance of single and twin bearing cows at calving time has been observed over 2 calvings at Grafton and Hamilton (Table 3). Birth weights of twin calves were approximately 80% of singles. Gestation length was shorter in twin-calving cows by 4 to 7 days. There was a low incidence of dystocia with little difference between twins and singles. Entanglement of calves during parturition by twin-bearing cows was not a problem. However 8-17% of twin-born calves required assistance to initiate suckling and/or to assist mothering. Retained placentae occurred only in the twin-calving cows (12-25%). At Grafton most cases did not require treatment but at Hamilton 60% of retained placentaes in required some form of veterinary intervention when clinical judgement suggested the cow was being affected. At Hamilton in 1990 detailed behavioural observations were carried out around parturition, on cows on their second or later calving (Table 4). Seventeen twin-bearing cows and 17 cows with single foetuses were observed during the per-i-parturient period. Small groups of cows were kept under continuous observation in a small floodlit paddock from just prior to calving until 2 to 3 days after birth. Cows were drafted into the calving area on the basis of their due date, appearance, and the degree of laxity of the sacrosciatic pelvic ligament (Dufty 197 1). Our experience has shown that high rates of survival among twin-born calves can be achieved given adequate nutrition and commitment to extra labour inputs at calving; the level of supervision required 441

5 Table 3. Calving performance cows bearing singles or twins, unadjusted means with (s.e.) where appropriate Table 4. Peri-parturient observations (Hamilton 1990) by a twin calving herd seems similar to that required by first calf heifers. Rejection of some calves can be expected (see Table 3) but this can be successfully treated in a couple of days by techniques such as close confinement or chaining calves together (as used in multiple suckling in the dairy industry). PRODUCTIVITY OF COWS WITH TWINS IN A WINTER RAINFALL ZONE A. J. CLARK, J. I;: GRAHAM, L. J. CUMMINS and I. K. MCLEOD Dept of Food and Agriculture, Pastoral and Veterinary Institute, PB 105, Hamilton, Vie We have previously compared small groups of cows bearing twin or single calves using individual animal feeding experiments. During late pregnancy and after calving cows with twins had higher energy requirements than their single counterparts (Graham et al. 1990). 442

6 In 1988 autumn calving crossbred cows were fed in a feedlot for 2 months pre and post calving before being grazed at pasture. All subsequent experiments were conducted at pasture with twinning cows receiving additional supplements. Cows in 1989 calved in autumn and spring. Table 5. Mean liveweights comparison of single (S) and twin (T) calves born in 1988 and 1989 In 1988 there was no significant difference in weaning and final weight of single or twin calves. II 1989 the twin bearing cows required kg more lupins/head.day supplementation during late pregnancy and early lactation than those bearing singles to maintain blood ketone levels around 0.7 mmol/l. The weight difference between twins and singles at weaning and 20 months was greater in spring calving cows than those calving in autumn. In 1990, autumn born twin and single calves were reared at pasture until weaning at 9 months after which they were sold to a commercial feedlot where growth rate and final weight data were collected (Table 6). Table 6. Mean liveweights and liveweight gains (LWG) from a 1990 study of single (S) and twin (T) heifers and steers that were fed in a feedlot after weaning 1990 twin calves were lighter than singles at weaning. When compared on the basis of per cow successfully calving, the twin cows weaned 434 kg of calf liveweight compared with 270 kg for single rearing cows. The growth rate of female twin and single calves after weaning was similar but the steer twin calves grew 9.7% slower than their single contemporaries. Table 7. The effect of birth type of twins on mean birth weight (kg), growth rate (ADG) (kg/day) to weaning Steer Heifer Mean s.e. Male Male Male Female Female Female Female Male Number Birth weight (kg) ADG to weaning The sex of the other twin has little effect on growth to weaning. Vaginal length was measured to detect freemartins (David et al. 1976). This was a simple technique, inserting a smooth rounded probe into the vagina until resistance was felt. At weaning female/female pairs had an average vaginal length of 27 cm, while all females born co-twin with a male had shortened vaginas with an average length of 10 cm. Over the 3 groups twins averaged 23% lighter at birth, 17% lighter at weaning at around 10 months of age, but only 3% lighter by the time of final weight. Twin bearing cows produced 104%, 88% and 97% more final progeny liveweight than single bearing cows in 1988, 1989 and 1990 respectively. 443

7 Proc. Aust. Soc. Anim. Prod. Vol. 19 PRODUCTION OF COWS WITH TWINS FROM IRRIGATED PASTURES AND THE IMPORTANCE OF EARLY WEANING FOR COWS ON HIGH LEVELS OF NUTRITION D. W. HENNESSY, J. F. WILKINS, P. J. WILLIAMSON, C. M. ANDREWS and B. J. MAKINGS NSW Agriculture, Agricultural Research and Advisory Station, Grafton, N.S.W This paper reports on 2 studies at Grafton NSW. In the first, twinning cows were compared with single birthing and rearing cows on irrigated pastures from November to February. In the second, an early weaning study 2 other groups of twin rearing cows and one of single rearing were compared from November to March when grazing summer growing grasses. The herd was assembled in 1989 by purchasing lactating Angus x Hereford cows. They were mated using procedures described by Cummins et al. (lot. cit.) between September and December. Prior to the first experiment they grazed irrigated ryegrass pastures (Lulium multijlorum) at a stocking rate of 2.8 cows/ha. On 8 November 1990,4 groups of 8, single rearing cows were allocated to pastures with 2 groups stocked at 4.0 cows/ha and 2 at 4.75/ha. Single groups of twin rearing cows were stocked at 3.45 and 4.0 cows/ha, with the former group being supplemented with 2 kg maize grain and 1 kg cottonseed meal per head daily over the 105 day period. Milk consumption by calves (3 months post calving) was estimated by a weigh-suckle-weigh technique. Pasture digestibility was estimated by an in vitro digestion of samples plucked from the sward. Faeces output was estimated by Cr203 dilution from a controlled release device, and forage intake calculated. Body fat was estimated by ultrasonography. Twin rearing cows had a mean intake some 45% greater than single rearing cows and this was related to a pasture yield approximately 24% less than that recorded on single rearing sites (Table 8). Table 8. Effect of calf rearing and cow stocking rate on pasture yield, quality and intake, summer Table 9. Production of cows rearing a single or twin calf at 2 stocking rates Twin rearing cows were leaner than single rearing cows and produced 60% more calf liveweight (Table 9). However this was at the expense of a higher forage intake, so that twin calf gains were only 17.5% higher per unit of intake by the cow than for single calf gains i.e. 116 g v g/kg OM intake. In the early weaning study, cows and calves grazed kikuyu grass (Pennisetum czandestinum) pastures from day 75 (November), when in some cows one of the twins was early weaned, until day 203 post-birth, when all calves were weaned. From day 75 to 115, the early weaned calves were offered daily 2 kg/head of a barley grain: luceme: soyabean meal: sorghum supplement: cottonseed + mineral

8 Production and twin rearing cows at day 203 after calving, and the weaning of 1 twin at day 75 after calving early mix (50:14:20:10:6); from day 115 to 150 it was increased to 2.5 kg and from day 151 onwards to 3.0 kg/head. Results are presented in Table 10. Early weaning of 1 twin increased output per cow by 27 kg or by 8.0%. This small gain from early weaning 1 of a set, versus twin suckling to 203 days, required 278 kg of supplement. The low efficiency of utilising the supplement, and the finding that all cows were in oestrus by day 100, suggests that early weaning is not beneficial to twin rearing cows that are adequately nourished. These early results indicate the improvement in biological efficiency offered by twinning. However, longer term data on reconception and subsequent production are required before critically assessing the economic benefits. ASSESSING THE ECONOMICS OF TWINNING IN BEEF CATTLE R. J. FARQUHARSON* and C. E. McLARENB *NSW Agriculture, Agricultural Research and Advisory Station, Grafton, N.S.W BDept of Food and Agriculture, Victorian Institute of Animal Science, Princes Highway, Werribee, Vie Given that the reproductive technology to induce twinning was almost available, an initial economic analysis was conducted to determine whether twinning was likely to be profitable in the Australian context. The analyses reported here are based on hypothesised responses. METHODS OF ANALYSIS Technology assessments can be performed both with a farm and an industry focus. An initial economic assessment of twinning involved farm-level (partial budget) and industry-level (market simulation model) analyses (Farquharson and Griffith 1991). Subsequently more detailed farm-level analyses were conducted by Farquharson (1991) involving linear programming (LP) and risk analysis and Douglas (1991) used cash flow development budgeting. Herd et al. (1991) used LP to evaluate 26 beef production systems. These systems included purebred and crossbred herds producing weaners and yearlings (both self-replacing and not-self-replacing) and a single sex bred heifer system. A bio-economic simulation model of a self-replacing beef herd (Spath et al. 1987) has also been modified to assess the productivity and profitability of twinning over a range of conditions and management regimes at the farm level. RESULTS At the farm level a partial budget of the beef enterprise indicated a potential advantage for twinning of $A26 to $47 per cow on the N.S.W. northern tablelands. This was extended to a whole-farm analysis using LP for the case study farm. After accounting for fixed farm resources (mainly feed and labour) and competing enterprises, the LP results indicated an increase in total beef gross margin of 7% over the normal beef activity gross margin. It involved a reduction in breeder numbers of 10% in utilising a fixed feed supply (Farquharson 1991). The beef enterprise results from this LP analysis were extended in a risk analysis where distributions rather than point estimates were used for key variables (weaning percentage, weaning weight and beef 445

9 Proc. Aust. Sot. Anim. Prod. Vol. I9 price) and the outcome was expressed as a probability distribution of total gross margin. At risk aversion levels measured for Australian farmers twinning was still potentially more appealing, depending on the distribution of weaning percentage. The LP analysis of Herd et al. (1991) showed that the more lean-meat-efficient systems used twinning to produce more calves and sold them at yearling rather than weaning age. The systems giving the highest economic returns used twinning and produced crossbred progeny. More efficient production systems were more profitable, with the most efficient being 2.6 times more profitable than the least efficient systems. The cash flow development budgeting approach of Douglas (1991) looked at the changeover period between traditional and twinning enterprises with particular emphasis on extra fencing requirements and fodder costs. The analysis showed that there were potential economic gains from changing to twinning, but that these were not substantial. Efficient management is essential in achieving the financial benefits. A preliminary analysis using the bio-economic simulation model over 25 years for a vealer enterprise in SW Victoria, indicated that, in terms of gross margin per hectare, the optimum stocking rate for cows with twins was about 10% lower than that for a single calving herd. At their respective optimum stocking rates, the average gross margin was $42 per hectare or $46 per cow more for the twinning herd. At the industry level, the analysis of Farquharson and Griffith (1991) assessed the likely impact of an increase in aggregate calving percentage and a reduction in aggregate weaning weight for the Australian beef industry. The market simulation model included supply and demand schedules in domestic and export markets and accounted for potential changes in beef prices resulting from changed beef supplies. If the aggregate Australian beef industry calving percentage increased by 0.25% and calf weaning weight was reduced by 0.7% the Net Present Value of industry net benefits was estimated to be $62 million. CONCLUSIONS The main results presented in this paper have indicated that there are potential economic advantages from changing to twinning, although those advantages might not be very large. The twinning technology is not meant to be applicable to all environments in the Australian beef industry, but rather to be most suitable to more intensively managed properties in higher rainfall regions. The analyses presented here have been based on best estimates of scientists, advisory officers and others in the industry to measure the most likely economic impacts of twinning. The bio-economic simulation model will be validated using data from the experiments at Hamilton and Grafton, and will then be used to make recommendations for the management of twins. ACKNOWLEDGMENTS The Meat Research Corporation has provided financial support for this co-ordinated project. REFERENCES BINDON, B. M., PIPER, L. R., HILLARD, M. A. and NETHERY, R. D. (1986). Proc. Aust. Sot. Reprod. Biol. 18: 44. BINDON, B. M., O SHEA, T., MIYAMOTO, IS., HILLARD, M., PIPER, L. R., NETHERY, R. D. and UPHILL, G. (1988). Proc. Aust. Sot. Reprod. Biol. 20: 28. BINDON, B. M. and PIPER, L. R. (1989). Proc. Beef Imp. Assoc. Aust. 1: 43. CUMMINS, L. J., O SHEA, T. and BINDON, B. M. (1986). Proc. Aust. Sot. Reprod. Biol. 18: 39. DAVID, J. S. E., LONG, S. E. and EDDY, R. (1976). Vet. Rec. 98: DICKERSON, G. E. (1978). Anim. Prod. 27: DICKERSON, G. E., GUERRA-MARTINEZ, P. and GREEN, R. D. (1988). USMARC Beef Research Progress Report No DOUGLAS, 3. (1991). B. Ag. Econ. dissertation University of New England. DUSTY, J. H. (197 1) Aust. Vet..I. 47: FARQUHARSON, R. J. (1991). Rev. Market Agric. Econ. 59(l): FARQUHARSON, R. J. and GRIFFITH, G.R. (1991). Agric. Sys. 36~ GORDON, I. (1983). Controlled Breeding in Farm Animals. (Permagon Press, Oxford.) GORDON, I., WILLIAMS, G. L. and EDWARDS, J. (1962)..I. Agric. Sci. Camb. 59: GRAHAM, J. F., CUMMINS, L. J., CLARK, A. J. and LANG AT, K. A. (1990). Proc. Aust. Sot. Anim. Prod. 18: GREGORY, K. E., ECHTERNKAMP, S. E., DICKERSON, G. E., CUNDIFF, L. V., KOCH, R. M. and VAN VLECK, L. D. (1990). J. Anim. Sci. 68:

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