Abstract:
3A Blowfly strike and wool growth. 2. Potential mediators of effects, other than anorexia S.W. Walkden_Brown1, B. Daly1, I.G. Colditz2, J.R. McFarlane3 and K.G. Kauter 1 3 3 Animal Science, UNE, Armidale NSW 2351; 2CSIRO Animal Production, Locked Bag, Armidale NSW 2350; Animal Physiology, UNE, Armidale NSW 2351 Blowfly strike or other febrile conditions in sheep are typically associated with reductions in staple strength or a frank break in the wool. The most likely causes of these effects include feverinduced anorexia and elevated cortisol secretion, since cortisol in supra physiological concentrations has welldocumented inhibitory effects on wool growth. WalkdenBrown et al. (1999) showed that only 27% of the reduction in wool growth caused by moderate flystrike was caused by reduced feed intake. In that experiment a wide range of physiological variables, some of which may potentially influence wool growth directly, were also monitored and are reported here. Infection with 500 L. cuprina larvae from days 07 induced significant elevations in temperature and plasma cortisol, interleukin6 (IL6), bilirubin and a significant depression in plasma glucose (Figure 1). Control sheep pair fed with struck sheep did not differ from uninfected controls. No significant effects were observed for plasma IL1a, IL8, tumour necrosis factora and leptin, although there was a trend towards lower leptin concentrations in fly struck sheep. Elevated cortisol remains a very likely mechanism for reduced wool growth. Elevated temperature alone should increase wool growth while effects on bilirubin, glucose and leptin are likely to be secondary to reduced feed intake and cytokineinduced fever. This is the first report of elevated peripheral IL6 in fly struck sheep and this, and other cytokines, is a promising additional mediator of the inhibitory effect of blowfly strike and other febrile conditions on wool growth. WalkdenBrown, S.W., Daly, B.L., Crook, B.J. and Colditz, I.G. (1999). Blowfly strike and wool growth. 1. Role of anorexia in mediating effects on wool. Recent Advances in Animal Nutrition in Australia 12, 2A. Figure 1 Mean (� SEM) rectal temperature (a) and plasma concentrations of cortisol (b), interlelukin_6 (c), bilirubin (d) glucose (e) and leptin (Struck treatment) from days _2 to 14. Struck sheep were infected on days 0_7 (*P<0.05). Recent Advances in Animal Nutrition in Australia, Volume 12 (1999) 4A 4A Body composition explains only part of the intake difference between high and low efficiency Angus steers E.C. Richardson1, R.M. Herd2, V.H. Oddy2, R.T. Woodgate2, J.A. Archer3 and P.F. Arthur3 Agriculture, Wagga Wagga NSW 2650; 2NSW Agriculture, and Cattle and Beef CRC, University of New England, Armidale NSW 2351; 3NSW Agriculture, Trangie NSW 2823 1NSW Angus steers from parents selected for high net feed efficiency (NFE; HE steers) were as heavy and grew as fast during feedlot finishing as steers from parents selected for low NFE (LE steers), yet ate significantly less and consequently were more efficient (Richardson et al. 1998). The HE steers had significantly less subcutaneous rib and rump fat thickness at the start and end of the 114 d test period. This implies that body composition might be important in explaining differences in feed efficiency that accompany selection for NFE. At the end of the test period the steers were slaughtered, minced and their protein (as N x 6.25), fat (soxhlet extraction) and energy (protein 23.6 MJ/kg; fat 39.3 MJ/kg) contents determined. The chemical composition of hide and bones was calculated from published values. No results for the tail, head, lower leg and hooves are included. The initial chemical composition of each animal was calculated using its initial liveweight and assuming that its chemical composition was the same as at the end of the test. Heat production (HP) was calculated as the difference between ME intake (MEI) and energy retained in tissue gain (ER). Maintenance energy expenditure was estimated as HP less energy expended in tissue gain calculated as (tissue mass x energy content/kf or kp) where kf = 0.75, and kp = 0.2 (rather than the textbook value of 0.45 derived from rats). There was a trend for LE steers to be fatter at the start and end of the test. The gains in protein and fat were similar for HE and LE steers, and as a result, ER was similar. The difference in ER (0.03 GJ) represented 5% of the difference in MEI (0.64 GJ). There were no differences in protein mass maintained over the test period but estimated maintenance costs were 9.5% higher for LE steers. Divergence selection for NFE has produced small changes in fatness in steers but these results suggest that they account for only a small fraction of the observed differences in MEI and feed efficiency. Rather the differences are due to higher HP likely to be associated with differences in feed intake, tissue turnover and activity. Richardson, E.C., Herd, R.M., Archer, J.A., Woodgate, R.T. and Arthur, P.F. (1998). High net feed efficient steers eat less for the same feedlot performance. Animal Production in Australia 22, 21316. Table 1 Chemical composition and energy balance for high and low NFE Angus steers over a 114 day test (values are means � SE). Trait High efficiency 284.00 61.90 32.80 423.00 92.50 49.10 12.10 1.59 10.50 7.01 � 7.00 � 3.20 � 0.90 � 6.00 � 4.10 � 1.20 � 0.20 � 0.08 � 0.20 � 0.33 Low efficiency 293.00 69.50 32.40 428.00 101.80 47.40 12.80 1.62 11.20 7.68 � 7.00 � 2.20 � 0.70 � 8.00 � 2.90 � 0.50 � 0.30 � 0.06 � 0.30 � 0.39 Significance ns P=0.05 ns ns P<0.1 ns P<0.05 ns P=0.1 P<0.2 Start test liveweight (kg) Start test chemical fat (kg) Start test chemical protein (kg) End test liveweight (kg) End test chemical fat (kg) End test chemical protein (kg) ME Intake (GJ) Energy Retained (GJ) Heat production (GJ) Estimated maintenance costs (GJ) Recent Advances in Animal Nutrition in Australia, Volume 12 (1999) 5A Environmental factors affecting the apparent metabolisable energy of feed wheat in broiler diets L. Acone1 and M. Wootton 1 2 2 Agrifood Technology (Division of AWB Limited) Werribee Vic 3030 Department of Food Science and Technology, University of NSW, Sydney NSW 2052 Establishing procedures for identifying low AME wheats would greatly benefit the poultry industry, allow for better selection and marketing of high AME wheats, and enable more accurate feed formulation. There is evidence that the physicochemical properties of barley are affected by climatic conditions (Willingham et al. 1960). Similarly, wheat grown in cool and moist regions contained lower levels of nonstarch polysaccharides (NSP) than that given in hotter and drier conditions (Coles et al. 1997). Choct (1995) speculated that heat stress during grain filling may be responsible for the high level of NSP in low AME wheat. These observations suggest that high AME wheat may be grown under favourable environmental conditions. Wheats from the 93/94, 94/95, 95/96 and 96/97 season were assayed for AME, using feeding trials. Monthly rainfall and temperature data were obtained from the Bureau of Meteorology. The AME for a total of 40 wheat samples (13 varieties, 35 sites) varied between 10.7 and 15.0 MJ/kg DM. A significant positive correlation between AME and total rainfall was observed (Table 1) for the months of January, September, December and for total annual rainfall (r = 0.327, P<0.05). An inverse relationship was observed between mean daily maximum temperature and the AME of 14 wheat samples (7 varieties, 12 sites) for all months of the year. In particular, correlations were highly significant for the months of January, February and December. These data suggest that cool and high rainfall growing conditions may favour the production of high AME wheats. The correlations observed in this study did not, however, allow accurate prediction of the AME of wheats. This suggests that rainfall and temperature per se are not the only factors affecting AME, and that other variables such as wheat variety or soil type may be responsible for the observed variation. Choct, M. (1995). Role of soluble and insoluble fibre in broiler nutrition. Chicken Meat Research and Development CouncilFinal Report. Project Number CSN 2CM, CSIRO. Coles, G.D., HartunianSowa, S.M., Jamieson, P.D., Hay, A.J., Atwell, W.A. and Fulcher, R.G. (1997). Environmentallyinduced variation in starch and nonstarch polysaccharide content in wheat. Journal of Cereal Science 26, 4754. Willingham, H.E., Leong, K.C., Jensen, L.S. and McGinnis, J. (1960). Influence of geographical area of production on response of different barley samples to enzyme supplements or water treatment. Poultry Science 39, 103108. Table 1 Correlations between AME and mean daily maximum temperature (�C) and total monthly rainfall (mm). Temperature Rainfall Correlation _0.680, P<0.01 _0.665, P<0.01 _0.469, P<0.1 _0.379, P<0.2 _0.396, P<0.2 _0.409, P<0.2 _0.355, NS _0.319, NS _0.425, P<0.2 _0.436, P<0.2 _0.490, P<0.1 _0.690, P<0.01 Range 0 _ 242 2 _ 147 0_ 0_ 69 55 Correlation 0.308, P<0.05 NS NS NS NS NS NS NS 0.331, P<0.05 NS NS 0.426, P<0.01 Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Range 22.7 _ 39.0 23.4 _ 35.5 20.9 _ 33.5 19.3 _ 29.8 15.0 _ 26.3 10.3 _ 21.2 11.0 _ 20.9 12.4 _ 22.5 13.5 _ 23.9 15.6 _ 27.4 18.0 _ 30.8 20.3 _ 33.7 1 _ 108 12 _ 140 0 _ 213 0_ 80 13 _ 136 4 _ 124 0 _ 221 0 _ 177 NS: No significant correlation. Recent Advances in Animal Nutrition in Australia, Volume 12 (1999) 6A 6A Seasonal variation in carcass quality of pigs: does pattern of nutrition play a role? M. Trezona1, B.P. Mullan2, R.H. Wilson3 and I.H. Williams1 1Faculty 2Animal of Agriculture, The University of Western Australia, Nedlands WA 6907 Services, Agriculture WA, Locked Bag No. 4, Bentley Delivery Centre WA 6983 3Wandalup Farms, PO Box 642, Mandurah WA 6210 Carcass quality in pigs, and hence price per kg, is currently determined by the P2 measurement, the depth of subcutaneous fat 65 mm down from the midline at the last rib. Records from producers and processors over a number of years indicate that P2 varies during the year without any apparent change in the management or feeding of pigs. Data collected over 12 years from a major Western Australian piggery indicate (Figure 1) that there is a consistent seasonal fluctuation in P2 and hence carcass quality. Similar patterns have been identified for other herds in Australia, the UK and the USA. Corresponding fluctuations in liveweight could be one explanation for the fluctuations in P2 because as pigs get heavier they become fatter. However, regression analysis indicated that weight accounted for less than 20% of the variation in P2. The voluntary food intake of pigs is sensitive to changes in ambient temperature, but it is nutrient intake per se which we believe is having the major effect on carcass composition at slaughter. One explanation for fatter pigs in spring involves a depression of growth early in life followed by a compensatory increase at heavier weights. As pigs grow they deposit proportionately more fat and less lean. It follows that the leanest carcasses at slaughter are from those pigs that have relatively high growth rates early in life, when the gain of fat:lean is low, and then experience a depression in growth during the finishing phase when the gain of fat:lean is highest. Pigs sold in spring spend most of their early life in summer, a period when high temperatures may reduce food intake. With the onset of cooler weather, these pigs have the opportunity to compensate by increasing their food intake and consequently their growth. Growth at this later stage of life is associated with a higher fat:lean gain and hence an increase in P2. If this hypothesis is correct, then producers must minimise variation in voluntary food intake to reduce variation in carcass fat. 18 16 P2 (mm) 14 12 10 8 Jan Jul Jan Month Jul 1985&1986 1987&1988 1989&1990 1991&1992 1993&1994 1995&1996 Figure 1 Average monthly P2 depths of bacon weight pigs at slaughter (81 to 101 kg liveweight). Recent Advances in Animal Nutrition in Australia, Volume 12 (1999) 7A Leptin a potential marker for body composition in sheep K.G. Kauter1, M. Ball1, R. Tellam2 and J.R. McFarlane 1 1 2 Division of Animal Physiology, University of New England, Armidale NSW 2351 Division of Tropical Agriculture, CSIRO, Long Pocket Laboratories, Indooroopilly Qld 4068 Leptin, a recently discovered hormone secreted from adipose tissue (Zhang et al. 1994) was first described as a regulator of adiposity, food intake and energ y metabolism. The ob gene encodes a 4.5 kbp mRNA which appears to be expressed almost solely in adipose tissue, encoding a protein of approximately 16 kDa. There is no known homology with other proteins and the homology of the derived leptin amino acid sequence across the different species ranges from 95% to 84%. It is now apparent that leptin physiology is much more complex and is likely to play an important role in many other systems including reproduction, haematopoiesis and the immune system. Leptin levels have been shown to be well correlated with body fat in humans and rodents, and exogenous leptin administered to both rats and mice results in loss of body fat. Leptin is likely to be an important humoral signal to the central nervous system on body composition, thus regulating food consumption. The currently available assays for leptin have limited or no cross reactivity with bovine leptin. This has restricted leptin research to work on rodents and humans, or to studies of mRNA levels in fat tissue. The aim of this study was to develop a leptin immunoassay suitable for use with sheep to allow the investigation of its role in body composition in ruminants. Bovine recombinant leptin (brLeptin) which has a single amino acid difference from ovine leptin was used to immunise chickens. An antiserum (jmck#16) was used to develop a variation of a competitive ELISA. Using brLeptin as standard the assay has a sensitivity of 1 ng/ml with inter and intra assay variation of 15% and 7% respectively. The dose response curve of ewe plasma was linear and parallel to brLeptin dose response curve as shown in Figure 1. Dose response curves from rams, and male castrate (wethers) plasma (data not shown) and an extract of sheep fat were also parallel to brLeptin (Figure 1). Using this assay, plasma from ewes, rams and wethers (n = 5) had mean (� SD) concentrations of leptin of 6.2 � 1.3, 4.5 � 1.2 and 5.3 � 1.5 respectively. These data are consistent with previous reports that leptin levels in males are lower than females. The availability of this assay will allow the large scale investigation of leptin levels in sheep to test the hypothesis that plasma leptin levels will reflect the amount of fat, which may assist in the selection of lines of sheep with differing body compositions suitable for various markets. Zhang, Y.Y., Proenca, R., Maffei, M., Barone, M., Leopold, L. and Friedman, J.M. (1994). Positional cloning of the mouse obese gene and its human homologue. Nature 372, 425432. 2 1 Logi t B /B0 0 -1 l epti n se r u m -2 fa t 1 10 1 00 D o s e ( ng or � l) Figure 1 Dose response curves of recombinant leptin (ng), sheep serum (ml) and sheep fat (ml) extract. Recent Advances in Animal Nutrition in Australia, Volume 12 (1999) 8A 8A Effects of early life nutrition of Brahman crossbred steers on subsequent feedlot performance J.A. Lindsay, N.C. Cooper and I. Batterham Qld Beef Industry Institute, Dept of Primary Industries, Swan's Lagoon, Millaroo Qld 4807 A recent review (Ball et al. 1997) has highlighted the importance of nutrition in early life (the first six to twelve months) on subsequent growth rates of beef cattle. The present experiment used earlyweaned Brahman crossbred calves, 3 to 4 months old, to study the effect of three planes of nutrition after weaning on subsequent growth rates under a feedlot finishing system. The steers grazed unimproved native pastures, predominantly Heteropogon contortus, and were supplemented with a mixture (w/w) of crushed sorghum (77), cottonseed meal (14.2), urea (1.2), salt (0.5), bentonite (3), and minerals and vitamins plus monensin. Three levels of supplement were chosen to give growth rates of 0.3 (Low), 0.5 (Medium) and 0.8 kg/day (High) from weaning in April 1994 to December 1994. All steers then grazed native pastures until July 1995 when steers in the Medium and High groups were supplemented ad lib. with molasses plus 8% urea for 60 days, and then molasses plus 3% urea and 10% cottonseed meal until December 1995. The High steers reached a target weight of 420 kg at 22 months of age and the Low group took 4 months longer. Each group then entered the feedlot when the group mean weight was 420 kg. The growth rate of the Low steers in the feedlot was significantly lower when compared with the Medium and High groups. It was also observed that the carcasses in the Low group were more variable in weight i.e. there was a higher proportion of underweight carcasses. These results show that Brahman crossbred steers need to gain a minimum of 0.5 kg/day during the immediate postweaning stage to achieve optimum feedlot growth rates and consistent carcass weights. The Cattle and Beef Industry CRC provided partial funding for this work. Ball, A.J., Oddy, V.H. and Thompson, J.M. (1997). In: Recent Advances in Animal Nutrition in Australia 1997, pp. 192208 (eds. J.L. Corbett, M. Choct, J.V. Nolan and J.B. Rowe). University of New England, Armidale NSW. Table 1 Liveweight gains, kg/d, during feedlot finishing of early_weaned steers. Days 0_98 1.63 1.56 1.36 0.06 a a b Treatment High Medium Low s.e. Days 14_98 1.49 1.46 1.21 a a b Overall 1.59 1.56 1.32 a a b 0.05 0.06 Within column values followed by different letters are significantly different (P<0.05). Recent Advances in Animal Nutrition in Australia, Volume 12 (1999) 9A Dietary manipulation using AUSPIG to optimise pig production C.E. Foote1, B. Hosking2, J.Gaughan1 and J.E. Riley 3 1School of Veterinary Science and Animal Production, University of Queensland, Gatton College, Lawes Qld 4343; 2Better Blend Stockfeeds, Oakey Qld 4401; 3JCR Associates International, `Warreners' M.S. 150, Pittsworth Qld 4356 With a constant drive for improved efficiency, pig producers are being forced to consider the many factors such as genotype, piggery environment, nutrition and market requirements that account for the variation seen in their herds (Patience et al. 1996; Willis, 1998). Because of these complex interactions, effective management in industry can only be achieved using simulation models such as AUSPIG (DSL Systems Centre, CSIRO Animal Production, Blacktown NSW 2148) which bring together a depth of knowledge about the factors determining animal performance and enterprise profitability (Black et al. 1993). In an experiment conducted to investigate the optimal dietary formulation to meet herd requirements, AUSPIG was used to design three diets to supply 100, 115 and 130% of the requirements of the average male in the herd. AUSPIG 100 satisfies the mean animal in the herd, while AUSPIG 115 and 130 support a higher than average rate of protein deposition allowing for a greater number of animals in the herd to express their genetic potential. Results are shown in Table 1. Table 1 A difference is clearly shown in the way each sex responded to each treatment; significant effects (P<0.05) of sex and treatment on weight gain and backfat support this observation. These results suggest that split-sex feeding might be considered as a method of improving productivity within this piggery. AUSPIG has the capacity to interpret what-if scenarios and assist producers in developing strategies for improving efficiency and profitability. Black, J.L., Davies, G.T. and Fleming, J.F. (1993). Role of computer simulation in the application of knowledge to animal industries. Australian Journal of Agricultural Research 44, 541-55. Patience, J.F. and de Lange, D.F.M. (1996). Swine nutrition in the 21st century. Animal Feed Science and Technology 19-27. Willis, S. (1998). AUSPIG In action a Queensland experience. In: Pan Pacific Pork Expo Seminar Day Proceedings, pp. 4147 (eds. S. Kratzmann and P. Fearon). Department of Primary Industries, Toowoomba, Qld. Results of dietary experiment with male and female pigs. AUSPIG 100 Male Female 71 32.7 9 92 49.6 1.73 2.15 133 91.0 1010 2.99 2.96 15 940 2.72 144.00 30.25 113.75 AUSPIG 115 Male 68 32.0 9 89 49.8 1.71 2.02 130 92.1 1032 3.11 3.02 14 969 2.72 142.50 33.35 109.15 Female 67 30.4 8 88 47.6 1.65 2.02 129 87.2 966 3.06 3.16 14 916 2.82 141.60 32.65 108.95 Male 70 33.4 8 91 51.5 1.66 1.92 132 95.6 1076 2.95 2.75 13 1003 2.51 148.75 34.05 114.70 AUSPIG 130 Female 71 30.6 9 92 47.3 1.77 2.23 134 86.3 951 2.96 3.11 14 898 2.84 140.20 34.65 105.55 Starting Age (days) Liveweight (kg) P2 (mm) End Grower Phase Age (d) Liveweight (kg) Feed Offered (kg/d) Feed Efficiency End Finisher Phase Age (d) Liveweight (kg) ADG (g/d) Feed Offered (kg/d) Feed Efficiency P2 farm Overall ADG (g/d) Feed Efficiency Profitability ($/pig) Net return Feed Cost Margin over feed 69 27.4 8 90 44.0 1.74 2.20 131 87.2 1054 3.15 2.99 13 965 2.77 141.20 31.50 109.70 Recent Advances in Animal Nutrition in Australia, Volume 12 (1999) 10A 10A The effects of phytase supplementation and available lysine content of weaner diets on pig growth performance D.J. Cadogan1, P.H. Selle2 and R.G. Campbell 1Bunge 1 Meat Industries, Corowa NSW 2646; 2BASF Animal Nutrition, Auburn NSW 2144 Microbial phytase supplementation of phosphorus adequate weaner diets has improved growth performance (Campbell et al. 1995) and responses in feed conversion have increased with dietary substrate concentrations of phytateP or phytic acid (Cadogan et al. 1997). The release of phytate bound amino acids by the enzyme may improve protein digestibility (Officer and Batterham 1992) and, consequently, feed efficiency. To investigate this hypothesis 14.8 MJ/kg DE wheatbased diets were formulated to contain three levels of available lysine (0.90, 0.85 and 0.80 g/MJ DE) with and without phytase (0 and 550 FTU/kg; Natuphos� Granulate). The nonsupplemented diets contained 0.89% Ca and 0.49% available P; these levels were reduced to 0.77% and 0.37% respectively with added phytase. The pelleted (75�C) diets had substrate levels of 0.24% phytateP with Ca:P ratios of 1.25:1. The six dietary treatments were of fered to 72 individually housed male pigs from weaning (6.0 kg liveweight at 26 days of age) and their performance was recorded over a feeding period of 21 days. The results are presented in Table 1. Phytase improved (P <0.01) feed efficiency with a trend (P <0.10) towards increased growth rates. Unexpectedly, lysine levels did not have any significant effects on performance, possibly because essential amino acids were in excess of requirements.At the lowest lysine level, phytase significantly improved feed efficiency which may be related to increased protein and/or energy availability because phytase increased the digestibility of all three diets regardless of their essential amino acid content. The antinutritive properties of phytic acid (and excess Ca and P) and the response of weaner pigs to added phytase is again demonstrated in this study. Cadogan, D.J. Selle, P.H. Campbell, R.G. and Walker, A.R. (1997). Effects of dietary phytate phosphorus and microbial phytase on the performance of weaner pigs. In: Manipulating Pig Production VI, p. 245 (ed. P.D. Cranwell). Australasian Pig Science Association, Werribee Vic 3030. Campbell, R.G. Harrison, D.T. Butler, K.J. and Selle, P.H. (1995). Effects of dietary available phosphorus and phytase (Natuphos) on the performance of pigs from 19 to 40 days postweaning. In: Manipulating Pig Production V, p. 193 (eds. D.P. Hennessy and P.D. Cranwell). Australasian Pig Science Association, Werribee Vic 3030. Officer, D.I. and Batterham, E.S. (1992). Enzyme supplementation of Linola� meal for grower pigs. Proceedings of the Australian Society of Animal Production 9, 288. Table 1 Effects of phytase and lysine on the performance of male pigs for 21 days post_weaning. Available lysine (g avail lys/MJ DE) 0.90 0.90 0.85 0.85 0.80 0.80 Microbial phytase (MP) Available lysine (AL) Interaction (MP x AL) Performance Daily gain (g) 361 437 373 359 353 393 0.072 0.329 0.154 Feed intake (g/day) 427 489 436 398 437 446 0.592 0.385 0.165 Feed:Gain Treatments Microbial phytase (FTU/kg) 0 550 0 550 0 550 Probability (P =): 1.18 ab 1.13 b 1.17 ab 1.11 b 1.24 a 1.14 b 0.009 0.294 0.777 a,b P <0.05 Recent Advances in Animal Nutrition in Australia, Volume 12 (1999) 11A The effect of molasses on the fermentation quality of wheat straw and poultry litter ensiled with citrus pulp P.K. Migwi1, J.R. Gallagher2 and R.J. van Barneveld 1 2 3 3 Egerton University, Animal Science Department, P.O. Box 536, Njoro, Kenya University of Adelaide, Animal Science Department, Roseworthy SA 5371 SARDI, Pig and Poultry Production Institute, Roseworthy SA 5371. Present address: Barneveld Nutrition Pty Ltd, PO Box 42, Lyndoch SA 5351 Poultry litter and citrus pulp are useful cheap local sources of nutrients for ruminants, especially during drought periods. In contrast, molasses to be used in S. Australia has to be transported over long distances and is an expensive feed supplement. Studies were conducted to find out whether inclusion of molasses had any effect on the fermentation quality and potential nutritive value of silage when wheat straw and poultry litter were ensiled with citrus pulp. In a 4x2 factorial, randomised complete block design, four treatments containing wheat straw, poultry litter and citrus pulp respectively on DM basis with 0 and 5% molasses were prepared as follows: T1(75:25:0); T2(60:25:15); T3(45:25:30) and T4(30:25:45). Thoroughly mixed material of each treatment, 510 kg, were ensiled for a period of 60 days in 20 litre hard plastic container laboratory silos that were lined with a double layer of polythene bags. Inclusion of 5% molasses when ensiling wheat straw and poultry litter with 0, 15, 30 and 45% citrus pulp had no significant effect on silage pH, neutral detergent fibre, acid detergent fibre, acid detergent lignin and in vitro OM digestibility. However, molasses resulted in a significant decrease in volatile fatty acids including Nbutyric acid. There was also a complete elimination of coliforms in all treatments, except in silage that had neither molasses nor citrus pulp. There was a significant difference in titratable acidity levels between silage with 0 and 5% molasses but this was only in silage with 30% citrus pulp. As the proportion of citrus pulp in silage increased there was a very highly significant increase in silage acidity and also a decrease in pH, though there was no significant difference in pH between silage with 30% or 45% citrus pulp. There was a very highly significant increase in in vitro OM digestibility from 0.33 to 0.56 for silage with 0 and 45% citrus pulp respectively. It was concluded that when wheat straw and poultry litter were ensiled with citrus pulp, the addition of molasses offered no significant benefit to offset the additional cost associated with its use. However, when no citrus pulp is included in the premix, addition of some molasses would appear desirable, so as to stimulate favourable fermentation. This practice can produce silage that is safe from potentially pathogenic microorganisms such as coliforms and is potentially a useful feed resource for ruminants. Recent Advances in Animal Nutrition in Australia, Volume 12 (1999) 12A 12A Lathyrus (Lathyrus cicera cv.Chalus): a potential new ingredient in pig grower diets B.P. Mullan, C.D. Hanbury, J.A. Hooper, R.R. Nicholls, C.R. Hagan and K.H.M Siddique Agriculture Western Australia, Locked Bag No 4, Bentley Delivery Centre WA 6983 In low rainfall (<400 mm p.a.) regions of southern Australia field peas are one of the few well adapted pulse crops but, in recent years, problems with fungal diseases have caused a decline in the area sown to this crop. Recent research at the Centre for Legumes in Mediterranean Agriculture in WA suggests that some species of Lathyrus are adapted to low rainfall regions (250 500 mm p.a.), particularly on fine textured alkaline soils. Compared to the chemical composition of lupin seed ( Lupinus angustofolius) , Lathyrus cicera (cv. Chalus) is lower in crude protein (270 vs 320 g/kg) and fat (5 vs 58 g/kg) but has relatively more total lysine (16 vs 13 g/kg) (Hanbury, unpublished). The major concerns are the higher concentrations of trypsin inhibitor activity, chymotrypsin inhibitor activity, and the presence of a neurotoxin identified as bNoxalyl La, bdiaminopropionic acid. Castell et al. (1994) reported a significant linear reduction in voluntary food intake (VFI) and average daily gain (ADG) when grower pigs were fed diets containing up to 400 g/kg Lathyrus sativus, which was attributed to the presence of these antinutritional factors (ANF). In the current experiment, seed from new breeding lines was fed to Table 1 growing pigs as a replacement for soybean meal. Diets were formulated to be isonitrogenous and isoenergetic (14.0 MJ DE/kg, 0.70 g available lysine/MJ DE), and were fed ad libitum to a total of 24 female pigs housed in individual pens. Results indicate that increasing the inclusion level of Lathyrus cicera up to 300 g/kg of the diet had no significant effect on either VFI, ADG or feed conversion ratio (FCR), neither for the initial phase of the experiment nor over the total time of the experiment. There was also no significant effect of inclusion level on carcass weight, dressing percentage or depth of subcutaneous fat. A lack of difference in either weight of liver or kidney, unlike results from other studies (Castell et al. 1994), indicates that the concentrations of ANF in current lines of Lathyr us cicera are sufficiently low not to cause a problem when the seed is fed to pigs of 16110 kg. Castell, A.G., Cliplef, R.L., Briggs, C.J., Campbell, C.G. and Bruni, J.E. (1994). Evaluation of lathyrus (Lathyrus sativus L.) as an ingredient in pig starter and grower diets. Canadian Journal of Animal Science 74, 529539. Performance of growing pigs fed diets with increasing concentrations of Lathyrus. 0 16.0 109.3 899 100 16.0 110.0 896 200 16.1 109.0 895 300 16.0 110.7 912 P= 0.996 0.906 0.956 LSD 1.12 5.01 69.7 Lathyrus (g/kg) Liveweight (kg) _ start Liveweight (kg) _ end ADG (g) VFI (kg/d) Day 0 to 40 Day 0 to 97 FCR Day 0 to 40 Day 0 to 97 Liver wt (g) Kidney wt (g) 1.46 1.96 1.38 1.76 1.38 1.77 1.48 1.81 0.346 0.444 0.148 0.290 1.91 2.18 1794 381 1.87 1.97 1866 360 1.77 2.05 1779 401 2.01 1.99 1780 383 0.480 0.405 0.661 0.651 0.202 0.279 168.8 68.4 Recent Advances in Animal Nutrition in Australia, Volume 12 (1999) 13A Predicting caecal pH from faecal pH E.H. Clayton and J.B. Rowe Animal Science, University of New England, Armidale NSW 2351 The occurrence of acid accumulation and lactic acidosis in the hind gut of ruminants and monogastrics on grain baseddiets is becoming increasingly well recognised. Measurement of pH in the caecum is not possible, however, without euthanasing the animal or surgically inserting a cannula into the caecum. There are several studies in which both faecal and caecal pH has been recorded in sheep on various diets, and this paper examines the use of faecal pH as a possible predictor of pH in the caecum and colon. While the caecum is well defined anatomica