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Effects of dietary enrichment with a marine oil-based n-3 LCPUFA supplement in sows with predicted birth weight phenotypes on growth performance and carcass quality of offspring
- M. N. Smit, J. D. Spencer, J. L. Patterson, M. K. Dyck, W. T. Dixon, G. R. Foxcroft
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Effects of a marine oil-based n-3 LCPUFA supplement (mLCPUFA) fed from weaning until the end of the next lactation to sows with a predicted low litter birth weight (LBW) phenotype on growth performance and carcass quality of litters born to these sows were studied, based on the hypothesis that LBW litters would benefit most from mLCPUFA supplementation. Sows were allocated to be fed either standard corn/soybean meal-based gestation and lactation diets (CON), or the same diets enriched with 0.5% of the mLCPUFA supplement at the expense of corn. The growth performance from birth until slaughter of the litters with the lowest average birth weight in each treatment (n=24 per treatment) is reported in this paper. At weaning, each litter was split between two nursery pens with three to six pigs per pen. At the end of the 5-week nursery period, two barrows and two gilts from each litter that had individual birth weights closest to their litter average birth weight, were moved to experimental grow–finish pens (barn A), where they were housed as two pigs per pen, sorted by sex within litter. Remaining pigs in each litter were moved to another grow–finish barn (barn B) and kept in mixed-sex pens of up to 10 littermates. After 8 weeks, one of the two pigs in each pen in barn A was relocated to the pens holding their respective littermates in barn B. The remaining barrows and gilts were individually housed in the pens in barn A until slaughter. Maternal mLCPUFA supplementation increased docosahexaenoic acid (DHA) concentration in the brain, liver and Semitendinosus muscle of stillborn pigs (P<0.01), did not affect eicosapentaenoic acid and DHA concentrations in sow serum at the end of lactation, and did not affect average daily gain, average daily feed intake or feed utilization efficiency of the offspring. BW was higher (P<0.01) in the second half of the grow–finish phase in pigs from mLCPUFA sows compared with controls in barn A, where space and competition for feed was minimal, but not barn B. Carcass quality was not affected by treatment for pigs from barn A, but maternal mLCPUFA supplementation negatively affected carcass quality in pigs from barn B. Collectively, these results suggest that nutritional supplementation of sows can have lasting effects on litter development, but that feeding mLCPUFA to sows during gestation and lactation was not effective in improving growth rates or carcass quality of LBW litters.
Effects of dietary enrichment with a marine oil-based n-3 LCPUFA supplement in sows with predicted birth weight phenotypes on birth litter quality and growth performance to weaning
- M. N. Smit, J. D. Spencer, J. L. Patterson, M. K. Dyck, W. T. Dixon, G. R. Foxcroft
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The effects of a marine oil-based n-3 long-chain polyunsaturated fatty acid (mLCPUFA) supplement fed to the sow from weaning, through the rebreeding period, during gestation and until end of lactation on litter characteristics from birth until weaning were studied in sows with known litter birth weight phenotypes. It was hypothesized that low birth weight (LBW) litters would benefit more from mLCPUFA supplementation than high birth weight litters. A total of 163 sows (mean parity=4.9±0.9) were rebred after weaning. Sows were pair-matched by parity and litter average birth weight of the previous three litters. Within pairs, sows were allocated to be fed either standard corn/soyabean meal-based gestation and lactation diets (CON), or the same diets enriched with 0.5% of the mLCPUFA supplement at the expense of corn. Each litter between 9 and 16 total pigs born was classified as LBW or medium/high average birth weight (MHBW) litter and there was a significant correlation (P<0.001) between litter average birth weight of the current and previous litters within sows (r=0.49). Sow serum was harvested at day 113 of gestation for determination of immunoglobulin G (IgG) concentrations. The number of pigs born total and alive were lower (P=0.01) in mLCPUFA than CON sows, whereas the number of stillborn and mummified pigs were similar between treatments. Number of stillborns (trend) and mummies (P<0.01) were higher in LBW than MHBW litters. Tissue weights and brain : tissue weight ratios were similar between treatments, but LBW litters had decreased tissue weights and increased brain : tissue weight ratios compared with MHBW litters. Placental weight was lower (P=0.01) in LBW than MHBW litters, but was not different between treatments. Average and total litter weight at day 1 was similar between treatments. mLCPUFA increased weaning weight (P=0.08) and average daily gain (P<0.05) in MHBW litters, but not in LBW litters. Pre-weaning mortality was similar between treatments, but was higher (P<0.01) in LBW than MHBW litters. IgG concentration in sow serum was similar between treatments and litter birth weight categories. In conclusion, litter birth weight phenotype was repeatable within sows and LBW litters showed the benchmarks of intra-uterine growth retardation (lower placental weight and brain sparing effects). As maternal mLCPUFA supplementation decreased litter size overall, only improved litter growth rate until weaning in MHBW litters, and did not affect pre-weaning mortality, maternal mLCPUFA supplementation was not an effective strategy in our study for mitigating negative effects of a LBW litter phenotype.
Responses to n-3 fatty acid (LCPUFA) supplementation of gestating gilts, and lactating and weaned sows
- M. N. Smit, J. L. Patterson, S. K. Webel, J. D. Spencer, A. C. Cameron, M. K. Dyck, W. T. Dixon, G. R. Foxcroft
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Feeding n-3 long-chain polyunsaturated fatty acids (LCPUFA) to gilts or sows has shown different responses to litter growth, pre-weaning mortality and subsequent reproductive performance of the sow. Two hypotheses were tested: (1) that feeding a marine oil-based supplement rich in protected n-3 LCPUFAs to gilts in established gestation would improve the growth performance of their litters; and (2) that continued feeding of the supplement during lactation and after weaning would offset the negative effects of lactational catabolism induced, using an established experimental model involving feed restriction of lactating primiparous sows. A total of 117 primiparous sows were pair-matched at day 60 of gestation by weight, and when possible, litter of origin, and were allocated to be either control sows (CON) fed standard gestation and lactation diets, or treated sows (LCPUFA) fed the standard diets supplemented with 84 g/day of a n-3 LCPUFA rich supplement, from day 60 of first gestation, through a 21-day lactation, and until euthanasia at day 30 of their second gestation. All sows were feed restricted during the last 7 days of lactation to induce catabolism, providing a background challenge against which to determine beneficial effects of n-3 LCPUFA supplementation on subsequent reproduction. In the absence of an effect on litter size or birth weight, n-3 LCPUFA tended to improve piglet BW gain from birth until 34 days after weaning (P = 0.06), while increasing pre-weaning mortality (P = 0.05). It did not affect energy utilization by the sow during lactation, thus not improving the catabolic state of the sows. Supplementation from weaning until day 30 of second gestation did not have an effect on embryonic weight, ovulation rate or early embryonic survival, but did increase corpora lutea (CL) weight (P = 0.001). Eicosapentaenoic acid and docosahexaenoic acid (DHA) levels were increased in sow serum and CL (P < 0.001), whereas only DHA levels increased in embryos (P < 0.01). In conclusion, feeding n-3 LCPUFA to gilts tended to improve litter growth, but did not have an effect on overall subsequent reproductive performance.
Maternal experiences of racial discrimination and child weight status in the first 3 years of life
- B. Dixon, S. L. Rifas-Shiman, T. James-Todd, K. Ertel, N. Krieger, K. P. Kleinman, J. W. Rich-Edwards, M. W. Gillman, E. M. Taveras
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- Journal:
- Journal of Developmental Origins of Health and Disease / Volume 3 / Issue 6 / December 2012
- Published online by Cambridge University Press:
- 07 June 2012, pp. 433-441
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Among US racial/ethnic minority women, we examined associations between maternal experiences of racial discrimination and child growth in the first 3 years of life. We analyzed data from Project Viva, a pre-birth cohort study. We restricted analyses to 539 mother–infant pairs; 294 were Black, 127 Hispanic, 110 Asian and 8 from additional racial/ethnic groups. During pregnancy, mothers completed the Experiences of Discrimination survey that measured lifetime experiences of racial discrimination in diverse domains. We categorized responses as 0, 1–2 or ⩾3 domains. Main outcomes were birth weight for gestational age z-score; weight for age (WFA) z-score at 6 months of age; and at 3 years of age, body mass index (BMI) z-score. In multivariable analyses, we adjusted for maternal race/ethnicity, nativity, education, age, pre-pregnancy BMI, household income and child sex and age. Among this cohort of mostly (58.2%) US-born and economically non-impoverished mothers, 33% reported 0 domains of discrimination, 33% reported discrimination in 1–2 domains and 35% reported discrimination in ⩾3 domains. Compared with children whose mothers reported no discrimination, those whose mothers reported ⩾3 domains had lower birth weight for gestational age z-score (β −0.25; 95% CI: −0.45, −0.04), lower 6 month WFA z-score (β −0.34; 95% CI: −0.65, −0.03) and lower 3-year BMI z-score (β −0.33; 95% CI: −0.66, 0.00). In conclusion, we found that among this cohort of US racial/ethnic minority women, mothers’ report of experiencing lifetime discrimination in ⩾ 3 domains was associated with lower fetal growth, weight at 6 months and 3-year BMI among their offspring.
Contributors
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- By Graeme J.M. Alexander, Heung Bae Kim, Michael Burch, Andrew J. Butler, Tanveer Butt, Roy Calne, Edward Cantu, Robert B. Colvin, Paul Corris, Charles Crawley, Hiroshi Date, Francis L. Delmonico, Bimalangshu R. Dey, Kate Drummond, John Dunning, John D. Firth, John Forsythe, Simon M. Gabe, Robert S. Gaston, William Gelson, Paul Gibbs, Alex Gimson, Leo C. Ginns, Samuel Goldfarb, Ryoichi Goto, Walter K. Graham, Simon J.F. Harper, Koji Hashimoto, David G. Healy, Hassan N. Ibrahim, David Ip, Fadi G. Issa, Neville V. Jamieson, David P. Jenkins, Dixon B. Kaufman, Kiran K. Khush, Heung Bae Kim, Andrew A. Klein, John Klinck, Camille Nelson Kotton, Vineeta Kumar, Yael B. Kushner, D. Frank. P. Larkin, Clive J. Lewis, Yvonne H. Luo, Richard S. Luskin, Ernest I. Mandel, James F. Markmann, Lorna Marson, Arthur J. Matas, Mandeep R. Mehra, Stephen J. Middleton, Giorgina Mieli-Vergani, Charles Miller, Sharon Mulroy, Faruk Özalp, Can Ozturk, Jayan Parameshwar, J.S. Parmar, Hari K. Parthasarathy, Nick Pritchard, Cristiano Quintini, Axel O. Rahmel, Chris J. Rudge, Stephan V.B. Schueler, Maria Siemionow, Jacob Simmonds, Peter Slinger, Thomas R. Spitzer, Stuart C. Sweet, Nina E. Tolkoff-Rubin, Steven S.L. Tsui, Khashayar Vakili, R.V. Venkateswaran, Hector Vilca-Melendez, Vladimir Vinarsky, Kathryn J. Wood, Heidi Yeh, David W. Zaas, Jonathan G. Zaroff
- Edited by Andrew A. Klein, Clive J. Lewis, Joren C. Madsen
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- Book:
- Organ Transplantation
- Published online:
- 07 September 2011
- Print publication:
- 11 August 2011, pp vii-x
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- By Charles E. Argoff, Gerard A. Banez, Samantha Boris-Karpel, Barbara K. Bruce, Alexandra S. Bullough, Annmarie Cano, Victor T. Chang, Elizabeth A. Clark, Daniel J. Clauw, June L. Dahl, Tam K. Dao, Amber M. Davis, Courtney L. Dixon, Michael H. Ebert, Robin M. Gallagher, Gerald W. Grass, Carmen R. Green, Jay Gunkelman, Bradford D. Hare, Jennifer A. Haythornthwaite, Jaclyn Heller Issner, W. Michael Hooten, Mark P. Jensen, Mark E. Jones, Robert D. Kerns, Raphael J. Leo, Morris Maizels, Mary E. Murawski, Brooke Myers-Sorger, Akiko Okifuji, Renata Okonkwo, John D. Otis, Stacy C. Parenteau, Laura E. Pence, Donald B. Penzien, Donna B. Pincus, Ellyn Poltrock Stein, Wendy J. Quinton, Jeanetta C. Rains, M. Carrington Reid, Thomas J. Romano, Jeffrey D. Rome, Robert L. Ruff, Suzanne S. Ruff, Steven H. Sanders, Ingra Schellenberg, John J. Sellinger, Howard S. Smith, Brenda Stoelb, Jon Streltzer, Mark D. Sullivan, Kimberly S. Swanson, Gabriel Tan, Stephen Thielke, Beverly E. Thorn, Cynthia O. Townsend, Dennis C. Turk, Stephanie C. Wallio, Lawrence J. Weinberger, David A. Williams, Hilary Wilson
- Edited by Michael H. Ebert, Yale University, Connecticut, Robert D. Kerns, Yale University, Connecticut
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- Behavioral and Psychopharmacologic Pain Management
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- 10 January 2011
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- 25 November 2010, pp ix-xii
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Effects of temperature and salinity on growth and uptake of 65Zn and 137Cs for six marine algae
- C. E. Styron, T. M. Hagan, D. R. Campbell, J. Harvin, N. K. Whittenburg, G. A. Baughman, M. E. Bransford, W. H. Saunders, D. C. Williams, C. Woodle, N. K. Dixon, C. R. McNeill
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- Journal:
- Journal of the Marine Biological Association of the United Kingdom / Volume 56 / Issue 1 / February 1976
- Published online by Cambridge University Press:
- 11 May 2009, pp. 13-20
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Population growth and concentration factors for 65Zn and 137Cs have been measured for Achnanthes brevipes Agardh, Carteria sp. Diesing, Chlamydomonas sp. Ehrenberg, Dunaliella salina Teod., Nannochloris atotnus Butcher, and Phaeodactylum tricornutum Lewin subjected to factorial combinations of eight temperatures (6–40 °C) and ten salinities (3.5–44.0 p.p.t.). Regression coefficients were calculated for polynomial models describing response surfaces for growth and radionuclide concentration. Salinity was more important than temperature in describing population growth for Carteria, Dunaliella, Nannochloris and Phaeodactylum. No independent variable was consistently of primary importance in describing 137Cs concentration factors, while temperature accounted for more variation in 65Zn concentration factors than salinity or population growth in all algae except Dunaliella. Concentration factors for 65Zn were uniformly higher than 137Cs concentration factors.
Interaction of soil burial and smoke on germination patterns in seeds of selected Australian native plants
- A. Tieu, K. W. Dixon, K. A. Meney, K. Sivasithamparam
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- Journal:
- Seed Science Research / Volume 11 / Issue 1 / March 2001
- Published online by Cambridge University Press:
- 22 February 2007, pp. 69-76
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Patterns of dormancy and smoke responsiveness in artificially buried seeds were investigated in eight native plant species from the species-rich mediterranean-type climate zone of south-western Australia. A comparison was made between germination and viability behaviour of shelf- and field-soil-stored seed, with and without smoke treatment, at least every 3 months. These comparisons corresponded with each of the four seasons. The species chosen germinated with the aid of smoke under field or glasshouse conditions (termed ‘dormant’; n = 4) or produced low and variable germination under glasshouse conditions with smoke (termed ‘deeply dormant’; n = 4). Three trends were observed in viability of soil-stored seeds over 450 d: no decline, gradual decline or late-onset decline. In addition, various germination responses to soil burial and aerosol smoke were observed. Burial was not required for optimal germination in Anigozanthos manglesii. However, for all other species tested, maximum germination was observed only following a period of burial. This was manifested in a germination response without smoke after a short period of burial (Stylidium affine and Conospermum triplinervium) or a longer period of burial (Conostylis neocymosa, Hibbertia commutata, Leucopogon conostephioides, Stirlingia latifolia and Stylidium crossocephalum). Smoke treatment led to high germination in buried seed of S. affine, S. crossocephalum and H. commutata. The patterns of germination detected in this limited number of species indicate that a variety of mechanisms may exist, both temporally and spatially, in south-western Australian species, and support further research of this type for horticulture and land restoration.
Looking Backward, Looking Forward: MLA Members Speak
- April Alliston, Elizabeth Ammons, Jean Arnold, Nina Baym, Sandra L. Beckett, Peter G. Beidler, Roger A. Berger, Sandra Bermann, J.J. Wilson, Troy Boone, Alison Booth, Wayne C. Booth, James Phelan, Marie Borroff, Ihab Hassan, Ulrich Weisstein, Zack Bowen, Jill Campbell, Dan Campion, Jay Caplan, Maurice Charney, Beverly Lyon Clark, Robert A. Colby, Thomas C. Coleman III, Nicole Cooley, Richard Dellamora, Morris Dickstein, Terrell Dixon, Emory Elliott, Caryl Emerson, Ann W. Engar, Lars Engle, Kai Hammermeister, N. N. Feltes, Mary Anne Ferguson, Annie Finch, Shelley Fisher Fishkin, Jerry Aline Flieger, Norman Friedman, Rosemarie Garland-Thomson, Sandra M. Gilbert, Laurie Grobman, George Guida, Liselotte Gumpel, R. K. Gupta, Florence Howe, Cathy L. Jrade, Richard A. Kaye, Calhoun Winton, Murray Krieger, Robert Langbaum, Richard A. Lanham, Marilee Lindemann, Paul Michael Lützeler, Thomas J. Lynn, Juliet Flower MacCannell, Michelle A. Massé, Irving Massey, Georges May, Christian W. Hallstein, Gita May, Lucy McDiarmid, Ellen Messer-Davidow, Koritha Mitchell, Robin Smiles, Kenyatta Albeny, George Monteiro, Joel Myerson, Alan Nadel, Ashton Nichols, Jeffrey Nishimura, Neal Oxenhandler, David Palumbo-Liu, Vincent P. Pecora, David Porter, Nancy Potter, Ronald C. Rosbottom, Elias L. Rivers, Gerhard F. Strasser, J. L. Styan, Marianna De Marco Torgovnick, Gary Totten, David van Leer, Asha Varadharajan, Orrin N. C. Wang, Sharon Willis, Louise E. Wright, Donald A. Yates, Takayuki Yokota-Murakami, Richard E. Zeikowitz, Angelika Bammer, Dale Bauer, Karl Beckson, Betsy A. Bowen, Stacey Donohue, Sheila Emerson, Gwendolyn Audrey Foster, Jay L. Halio, Karl Kroeber, Terence Hawkes, William B. Hunter, Mary Jambus, Willard F. King, Nancy K. Miller, Jody Norton, Ann Pellegrini, S. P. Rosenbaum, Lorie Roth, Robert Scholes, Joanne Shattock, Rosemary T. VanArsdel, Alfred Bendixen, Alarma Kathleen Brown, Michael J. Kiskis, Debra A. Castillo, Rey Chow, John F. Crossen, Robert F. Fleissner, Regenia Gagnier, Nicholas Howe, M. Thomas Inge, Frank Mehring, Hyungji Park, Jahan Ramazani, Kenneth M. Roemer, Deborah D. Rogers, A. LaVonne Brown Ruoff, Regina M. Schwartz, John T. Shawcross, Brenda R. Silver, Andrew von Hendy, Virginia Wright Wexman, Britta Zangen, A. Owen Aldridge, Paula R. Backscheider, Roland Bartel, E. M. Forster, Milton Birnbaum, Jonathan Bishop, Crystal Downing, Frank H. Ellis, Roberto Forns-Broggi, James R. Giles, Mary E. Giles, Susan Blair Green, Madelyn Gutwirth, Constance B. Hieatt, Titi Adepitan, Edgar C. Knowlton, Jr., Emanuel Mussman, Sally Todd Nelson, Robert O. Preyer, David Diego Rodriguez, Guy Stern, James Thorpe, Robert J. Wilson, Rebecca S. Beal, Joyce Simutis, Betsy Bowden, Sara Cooper, Wheeler Winston Dixon, Tarek el Ariss, Richard Jewell, John W. Kronik, Wendy Martin, Stuart Y. McDougal, Hugo Méndez-Ramírez, Ivy Schweitzer, Armand E. Singer, G. Thomas Tanselle, Tom Bishop, Mary Ann Caws, Marcel Gutwirth, Christophe Ippolito, Lawrence D. Kritzman, James Longenbach, Tim McCracken, Wolfe S. Molitor, Diane Quantic, Gregory Rabassa, Ellen M. Tsagaris, Anthony C. Yu, Betty Jean Craige, Wendell V. Harris, J. Hillis Miller, Jesse G. Swan, Helene Zimmer-Loew, Peter Berek, James Chandler, Hanna K. Charney, Philip Cohen, Judith Fetterley, Herbert Lindenberger, Julia Reinhard Lupton, Maximillian E. Novak, Richard Ohmann, Marjorie Perloff, Mark Reynolds, James Sledd, Harriet Turner, Marie Umeh, Flavia Aloya, Regina Barreca, Konrad Bieber, Ellis Hanson, William J. Hyde, Holly A. Laird, David Leverenz, Allen Michie, J. Wesley Miller, Marvin Rosenberg, Daniel R. Schwarz, Elizabeth Welt Trahan, Jean Fagan Yellin
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- Journal:
- PMLA / Publications of the Modern Language Association of America / Volume 115 / Issue 7 / December 2000
- Published online by Cambridge University Press:
- 23 October 2020, pp. 1986-2078
- Print publication:
- December 2000
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Effect of dietary fat supplements on levels of n-3 poly-unsaturated fatty acids, trans acids and conjugated linoleic acid in bovine milk
- N. W. Offer, M. Marsden, J. Dixon, B. K. Speake, F. E. Thacker
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- Journal:
- Animal Science / Volume 69 / Issue 3 / December 1999
- Published online by Cambridge University Press:
- 18 August 2016, pp. 613-625
- Print publication:
- December 1999
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The effects of three fat supplements on milk yield and composition were measured using 12 mid-lactation in-calf Hoistein-Friesian cows in a balanced incomplete change-over design over three periods each of 3 weeks. All cows received a basal diet consisting of 36 kg/day grass silage (dry matter (DM) 270 g/kg, metabolizable energy (ME) 11·6 MJ/kg DM) and 7 kg/day o f a concentrate mixture containing (g/kg) rolled barley (501), molassed sugar-beet pulp shreds (277), soya-bean meal (208) and a standard cow mineral supplement (14). Treatments were CON (control-no supplement); LIN and FISH (250 gl day of either linseed oil or marine oil, providing approximately 0·046 of ME intake) or TOA (95 glday of tuna orbital oil, providing 0·018 of total ME intake).
There were no significant effects on silage DM intake or milk yield (means 9·25 and 17·2 kg/day respectively). The FISH and TOA treatments depressed (F < 0·05) milk fat concentration (45·4, 44·6, 34·5 and 41·6 (s.e.d. 1·08) g/kg for CON, LIN, FISH and TOA respectively; note — the same treatment order is used for all results quoted). Compared with values for CON, yield of f at (glday) was significantly (F < 0·05) greater for LIN and significantly lower for FISH (739, 808, 572 and 732, s.e.d. 28·7). All three oil supplements reduced (F < 0·05) milk protein content (33·6, 32·5, 30·6 and 32·4 (s.e.d. 0·43) g/kg) but, apart from a small increase for LIN, protein yield (glday) was unaffected (545, 586, 510 and 574, s.e.d. 20·2).
The concentrations (g/100 g) of short-chain fatty acids (< C14) and C16 : 0 in milk f at were lower (F < 0·05) for LIN than for the other treatments. All supplements increased the concentrations ofC18:1 (F < 0·05), the value for LIN being greater (F < 0·05) than for the other treatments (21·0, 27·2, 25·3 and 23·7, s.e.d. 0·74). The FISH and TOA treatments increased (F < 0·05) the concentrations of long chain (< C2O) (n-3) poly-unsaturated fatty acids (PUFA), (0·19, 0·17, 0·49 and 0·27, s.e.d. 0·026) but less than proportionately 0·03 of dietary intake of these acids was transferred to milk, probably because they were found to be mostly in the phospholipid and cholesterol ester fractions of plasma. The FISH and TOA treatments increased (F < 0·05) the percentages of total trans fatty acids in milk fat (1·13, 2·19, 10·26 and 3·62, s.e.d. 0·728) whilst a significant (F < 0·05) increase in conjugated linoleic acid (CLA) was observed only for FISH (0·16, 0·28, 1·55, and 0·52, s.e.d. 0·154). Concentrations of CLA and total trans acids in milk were highly correlated (r = 0·91, no. =36, F < 0·001) whilst trans acids in milk were inversely correlated with milk fat content (r = -0·63, no. = 36, F < 0·001) supporting the theory that milk fat depression may be caused by increased supply of trans fatty acids to the mammary gland. The health implications of these changes in milk fat composition are discussed.
Effect of habitat disturbance on inoculum potential of ericoid endophytes of Western Australian heaths (Epacridaceae)
- B. J. HUTTON, K. W. DIXON, K. SIVASITHAMPARAM, J. S. PATE
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- Journal:
- The New Phytologist / Volume 135 / Issue 4 / April 1997
- Published online by Cambridge University Press:
- 01 April 1997, pp. 739-744
- Print publication:
- April 1997
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The presence of host plants was found to be a key determinant of soil infectivity for endophytes of epacrids growing in south-west Australian jarrah forest carrying a sparse epacrid understorey. A comparable Banksia woodland with higher density of epacrids showed more uniform levels of infective endophytes, presumably because of closer overlap of host-supported patches of endophyte. Disturbed sites in jarrah forest, in which topsoil had been recently returned following bauxite mining, initially showed extremely low endophyte infectivity, probably due to disruption of the hyphal network, absence of host plants and/or increased competition from soil micro-organisms antagonistic to the endophytes. As the system stabilized and epacrids recruited and grew, inoculum potential of the soil re-established and by 12 yr it equalled that of adjacent undisturbed native forest. At disturbed sites with sparsely distributed adult members of the Epacridaceae, endophyte inoculum proved to be adequate only directly adjacent to the epacrids and declined steeply to negligible levels at only 40 cm radially distant from a host plant. The significance of live epacrid root systems on survival of endophyte inoculum in Banksia woodland was examined following removal of shoots of adult plants of the endemic epacrid, Leucopogon conostephioides DC. Coincident with demise of roots of the detopped plants, endophyte inoculum potential of closely adjacent soil declined by 50% during the growing season. However, the effect was short lived and infectivity rose the following year to equal that of undisturbed adjacent woodland as mycelial matrices supported by neighbouring epacrids invaded the depleted study areas.
Fertility in a tropical beef herd divergently selected for pregnancy rate
- D. J. S. Hetzel, M. J. Mackinnon, R. Dixon, K. W. Entwistle
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- Journal:
- Animal Production / Volume 49 / Issue 1 / August 1989
- Published online by Cambridge University Press:
- 02 September 2010, pp. 73-81
- Print publication:
- August 1989
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Selection on the basis of estimated breeding value for cow fertility was successful in establishing two distinct lines of high (H) and low (L) fertility in a herd of Droughtmaster (Brahman × Shorthorn) cattle. The average difference in pregnancy rates over 3 years between the H and L line was 12% (P < 0·01) in the selected cows. In lactating cows this difference was 17% indicating that lactational anoestrus was an important component of the line difference in fertility. The total calf losses between confirmed pregnancy and weaning were 17%, but there were no line differences. Cow mortalities were 5% higher (P < 0·01) in pregnant cows than in empty cows but were similar in the H and L 'lines.
H cows were proportionately 0·06 lighter in body weight (P < 0·01) at mating and 0·075 lighter (P < 0·01) at weaning than L cows. Much of this difference was due to the greater number of calves carried and weaned by H cows during their lifetime. Smaller lactation effects on weight gains and weight losses in H cows indicated that these cows were less sensitive in terms of weight gain to seasonal fluctuations in nutrition. H cows conceived earlier than L cows in 2 out of the 3 years and reared calves which were proportionately 0·04 lighter at weaning (P < 0·01). It is suggested that lower milk production in H cows leading to shorter periods of lactational anoestrous, combined with lower sensitivity to nutritional stress, was responsible for their higher fertility.