Grazing beef cows identified as efficient using a nutrition model partition more energy to lactation
B. R. dos Reis A , L. O. Tedeschi B , A. Saran Netto
A , S. L. Silva A and P. A. Lancaster C *
+ Author Affiliations
- Author Affiliations
A Faculdade de Zootecnia e Engenharia de Alimentos, Universidade de São Paulo, Pirassununga, SP 13635-900, Brazil.
B Department of Animal Sciences, Texas A&M University, College Station, TX 77843-2471, USA.
C Range Cattle Research and Education Center, University of Florida, Gainesville, FL 33865-9706, USA.
Animal Production Science 62(1) 40-54 https://doi.org/10.1071/AN20558
Submitted: 26 March 2020 Accepted: 5 July 2021 Published: 30 September 2021
© 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing
Abstract
Context: The efficiency of the cow–calf sector could be enhanced by matching cow biological type to the production environment; however, methods to estimate the biological efficiency of grazing beef cows are not available.
Aims: This study utilised a mathematical nutrition model for ranking beef cows for estimated biological efficiency, determining energetic efficiency and evaluate relationships with other production traits.
Methods: Cow live weight, calf birth and weaning weight, calf birth and weaning date, and forage nutritive value of hay and pasture were collected for 69 Brangus crossbred beef cows over a complete production cycle. The Cattle Value Discovery System for Beef Cow (CVDSbc) model was used to compute metabolisable energy required (MER) for the cow, and energy efficiency index (EEI) was computed as the ratio of MER to calf weaning weight. Pearson correlation coefficients were computed among performance traits. During late lactation and gestation, low (n = 8) and high (n = 8) EEI cows were individually fed ad libitum for 44 and 32 days, respectively, then fed 0.5× the estimated metabolisable energy required for maintenance for 7 days (gestation experiment only). Apparent nutrient digestibility, heat production, and milk yield were measured.
Key results: EEI was strongly negatively correlated (P < 0.05) with model predicted peak milk (−0.62) and calf weaning weight (−0.65), but moderately correlated (P < 0.05) with cow live weight (0.46). Dry matter intake was not different (P > 0.75) between low and high EEI cows even though low EEI cows weighed less (P < 0.05) during late lactation and gestation experiments. Low EEI cows tended to have greater efficiency of metabolisable energy use for maintenance and gain (P < 0.10), and EEI was negatively correlated (P < 0.05) with the efficiency of metabolisable energy use for maintenance (−0.56) and gain (−0.57).
Conclusion: The CVDSbc model identified cows that weaned heavier calves due to greater dry matter intake of cows relative to live weight allowing more energy apportioned towards lactation, and more efficient use of metabolisable energy for maintenance and gain.
Implications: Energy efficiency index might provide a logical assessment of biological efficiency of beef cows in grazing production systems.
Keywords: beef cattle, biological efficiency, cow efficiency, cow size, energy efficiency index, energy metabolism, grazing systems, heat production.
References
Abdelsamei AH, Fox DG, Tedeschi LO, Thonney ML, Ketchen DJ, Stouffer JR (2005) The effect of milk intake on forage intake and growth of nursing calves. Journal of Animal Science 83, 940–947.| The effect of milk intake on forage intake and growth of nursing calves.Crossref | GoogleScholarGoogle Scholar | 15753351PubMed |
Aguiar AD, Tedeschi LO, Rouquette FM, McCuistion K, Ortega-Santos JA, Anderson R, DeLaney D, Moore S (2011) Determination of nutritive value of forages in south Texas using an in vitro gas production technique. Grass and Forage Science 66, 526–540.
| Determination of nutritive value of forages in south Texas using an in vitro gas production technique.Crossref | GoogleScholarGoogle Scholar |
Arthur PF, Archer JA, Herd RM (2004) Feed intake and efficiency in beef cattle: overview of recent Australian research and challenges for the future. Australian Journal of Experimental Agriculture 44, 361–369.
| Feed intake and efficiency in beef cattle: overview of recent Australian research and challenges for the future.Crossref | GoogleScholarGoogle Scholar |
Baldwin RL (1968) Estimation of theoretical calorific relationships as a teaching technique. A review. Journal of Dairy Science 51, 104–111.
| Estimation of theoretical calorific relationships as a teaching technique. A review.Crossref | GoogleScholarGoogle Scholar |
Blaxter KL, Clapperton JL (1965) Prediction of the amount of methane produced by ruminants. British Journal of Nutrition 19, 511–522.
| Prediction of the amount of methane produced by ruminants.Crossref | GoogleScholarGoogle Scholar |
Blaxter KL, Clapperton JL, Martin AK (1966) The heat of combustion of the urine of sheep and cattle in relation to its chemical composition and to diet. British Journal of Nutrition 20, 449–460.
| The heat of combustion of the urine of sheep and cattle in relation to its chemical composition and to diet.Crossref | GoogleScholarGoogle Scholar |
Bourg BM (2011) Determination of energy efficiency of beef cows under grazing conditions using a mechanistic model and the evaluation of a slow-release urea product for finishing beef cattle. Dissertation, Texas A&M University, College Station, TX, USA. Available at https://oaktrust.library.tamu.edu/handle/1969.1/ETD-TAMU-2011-12-10279
Brosh A, Aharoni Y, Holzer Z (2002) Energy expenditure estimation from heart rate: validation by long-term energy balance measurement in cows. Livestock Production Science 77, 287–299.
| Energy expenditure estimation from heart rate: validation by long-term energy balance measurement in cows.Crossref | GoogleScholarGoogle Scholar |
Buckley B (1982) Repeatability of cow efficiency, weaning weight and milk production in Angus, Charolais and reciprocal cross cows. M.S., South Dakota State University, Brookings, SD, USA. Available at https://openprairie.sdstate.edu/etd/4129
Bullock KD, Bertrand JK, Benyshek LL (1993) Genetic and environmental parameters for mature weight and other growth measures in Polled Hereford cattle. Journal of Animal Science 71, 1737–1741.
| Genetic and environmental parameters for mature weight and other growth measures in Polled Hereford cattle.Crossref | GoogleScholarGoogle Scholar | 8349501PubMed |
Chalk CD (2019) Role of methionine in fetal development of beef cattle. MSU Graduate Theses, Missouri State University, Springfield, MO, USA. Available at https://bearworks.missouristate.edu/theses/3377
Clutter AC, Nielsen MK (1987) Effect of level of beef cow milk production on pre- and postweaning calf growth. Journal of Animal Science 64, 1313–1322.
| Effect of level of beef cow milk production on pre- and postweaning calf growth.Crossref | GoogleScholarGoogle Scholar | 3583941PubMed |
Cole NA, McCuistion K, Greene LW, McCollum FT (2011) Effects of concentration and source of wet distillers grains on digestibility of steam-flaked corn-based diets fed to finishing steers. The Professional Animal Scientist 27, 302–311.
| Effects of concentration and source of wet distillers grains on digestibility of steam-flaked corn-based diets fed to finishing steers.Crossref | GoogleScholarGoogle Scholar |
Cortés-Lacruz X, Casasús I, Revilla R, Sanz A, Blanco M, Villalba D (2017) The milk yield of dams and its relation to direct and maternal genetic components of weaning weight in beef cattle. Livestock Science 202, 143–149.
| The milk yield of dams and its relation to direct and maternal genetic components of weaning weight in beef cattle.Crossref | GoogleScholarGoogle Scholar |
Davis ME, Rutledge JJ, Cundiff LV, Hauser ER (1983a) Life cycle efficiency of beef production: I. Cow efficiency ratios for progeny weaned. Journal of Animal Science 57, 832–851.
| Life cycle efficiency of beef production: I. Cow efficiency ratios for progeny weaned.Crossref | GoogleScholarGoogle Scholar | 6643301PubMed |
Davis ME, Rutledge JJ, Cundiff LV, Hauser ER (1983b) Life cycle efficiency of beef production: II. Relationship of cow efficiency ratios to traits of the dam and progeny weaned. Journal of Animal Science 57, 852–866.
| Life cycle efficiency of beef production: II. Relationship of cow efficiency ratios to traits of the dam and progeny weaned.Crossref | GoogleScholarGoogle Scholar | 6643302PubMed |
Davis ME, Rutledge JJ, Cundiff LV, Gearheart W, Hauser ER (1987) Life cycle efficiency of beef production: VII. Prediction of cow efficiency ratios for progeny weaned and slaughtered. Journal of Animal Science 64, 50–64.
| Life cycle efficiency of beef production: VII. Prediction of cow efficiency ratios for progeny weaned and slaughtered.Crossref | GoogleScholarGoogle Scholar |
Diaz C, Notter DR, Beal WE (1992) Relationship between milk expected progeny differences of polled Hereford sires and actual milk production of their crossbred daughters. Journal of Animal Science 70, 396–402.
| Relationship between milk expected progeny differences of polled Hereford sires and actual milk production of their crossbred daughters.Crossref | GoogleScholarGoogle Scholar | 1548201PubMed |
DiCostanzo A, Meiske JC, Plegge SD, Peters TM, Goodrich RD (1990) Within-herd variation in energy utilization for maintenance and gain in beef cows. Journal of Animal Science 68, 2156–2165.
| Within-herd variation in energy utilization for maintenance and gain in beef cows.Crossref | GoogleScholarGoogle Scholar | 2384405PubMed |
DiCostanzo A, Meiske JC, Plegge SD (1991) Characterization of energetically efficient and inefficient beef cows. Journal of Animal Science 69, 1337–1348.
| Characterization of energetically efficient and inefficient beef cows.Crossref | GoogleScholarGoogle Scholar | 2071497PubMed |
Dinkel CA (1988) The interaction of cow size with growth potential of the service sire. Canadian Journal of Animal Science 68, 129–137.
| The interaction of cow size with growth potential of the service sire.Crossref | GoogleScholarGoogle Scholar |
Dinkel CA, Brown MA (1978) An evaluation of the ratio of calf weight to cow weight as an indicator of cow efficiency. Journal of Animal Science 46, 614–617.
| An evaluation of the ratio of calf weight to cow weight as an indicator of cow efficiency.Crossref | GoogleScholarGoogle Scholar |
Dinkel CA, Tucker WL, Marshall DM (1990) Sources of variation in beef cattle weaning weight. Canadian Journal of Animal Science 70, 761–769.
| Sources of variation in beef cattle weaning weight.Crossref | GoogleScholarGoogle Scholar |
Ferrell CL (1988) Contribution of visceral organs to animal energy expenditure. Journal of Animal Science 66, 23–34.
| Contribution of visceral organs to animal energy expenditure.Crossref | GoogleScholarGoogle Scholar |
Ferrell CL, Jenkins TG (1985) Cow type and the nutritional environment: nutritional aspects. Journal of Animal Science 61, 725–741.
| Cow type and the nutritional environment: nutritional aspects.Crossref | GoogleScholarGoogle Scholar | 4066531PubMed |
Fox DG, Sniffen CJ, O’Connor JD (1988) Adjusting nutrient requirements of beef cattle for animal and environmental variations. Journal of Animal Science 66, 1475–1495.
| Adjusting nutrient requirements of beef cattle for animal and environmental variations.Crossref | GoogleScholarGoogle Scholar |
Freetly HC, Nienaber JA (1998) Efficiency of energy and nitrogen loss and gain in mature cows. Journal of Animal Science 76, 896–905.
| Efficiency of energy and nitrogen loss and gain in mature cows.Crossref | GoogleScholarGoogle Scholar | 9535353PubMed |
Freetly HC, Nienaber JA, Brown-Brandl T (2006) Partitioning of energy during lactation of primiparous beef cows. Journal of Animal Science 84, 2157–2162.
| Partitioning of energy during lactation of primiparous beef cows.Crossref | GoogleScholarGoogle Scholar | 16864877PubMed |
Freetly HC, Nienaber JA, Brown-Brandl T (2008) Partitioning of energy in pregnant beef cows during nutritionally induced body weight fluctuation. Journal of Animal Science 86, 370–377.
| Partitioning of energy in pregnant beef cows during nutritionally induced body weight fluctuation.Crossref | GoogleScholarGoogle Scholar | 17998430PubMed |
Garrett WN (1980) Factors influencing energetic efficiency of beef production. Journal of Animal Science 51, 1434–1440.
| Factors influencing energetic efficiency of beef production.Crossref | GoogleScholarGoogle Scholar |
Graham NMcC, Searle TW, Griffiths DA (1974) Basal metabolic rate in lambs and young sheep. Australian Journal of Agricultural Research 25, 957–971.
| Basal metabolic rate in lambs and young sheep.Crossref | GoogleScholarGoogle Scholar |
Hebart ML, Accioly JM, Copping KJ, Deland MPB, Herd RM, Jones FM, Laurence M, Lee SJ, Lines DS, Speijers EJ, Walmsley BJ, Pitchford WS (2018) Divergent breeding values for fatness or residual feed intake in Angus cattle. 5. Cow genotype affects feed efficiency and maternal productivity. Animal Production Science 58, 80–93.
| Divergent breeding values for fatness or residual feed intake in Angus cattle. 5. Cow genotype affects feed efficiency and maternal productivity.Crossref | GoogleScholarGoogle Scholar |
Herd RM, Arthur PF (2012) Lessons from the Australian experience. In ‘Feed efficiency in the beef industry’. (Ed. RA Hill) pp. 61–73. (Wiley-Blackwell: Ames, IA, USA)
Houghton PL, Lemenager RP, Hendrix KS, Moss GE, Stewart TS (1990) Effects of body composition, pre- and postpartum energy intake and stage of production of energy utilization by beef cows. Journal of Animal Science 68, 1447–1456.
| Effects of body composition, pre- and postpartum energy intake and stage of production of energy utilization by beef cows.Crossref | GoogleScholarGoogle Scholar | 2365655PubMed |
Jenkins TG, Ferrell CL (1994) Productivity through weaning of nine breeds of cattle under varying feed availabilities: I. Initial evaluation. Journal of Animal Science 72, 2787–2797.
| Productivity through weaning of nine breeds of cattle under varying feed availabilities: I. Initial evaluation.Crossref | GoogleScholarGoogle Scholar | 7730170PubMed |
Jenkins TG, Ferrell CL (2007) Daily dry matter intake to sustain body weight of mature, nonlactating, nonpregnant cows. Journal of Animal Science 85, 1787–1792.
| Daily dry matter intake to sustain body weight of mature, nonlactating, nonpregnant cows.Crossref | GoogleScholarGoogle Scholar | 17400974PubMed |
Jensen RG (1995) Miscellaneous factors affecting composition and volume of human and bovine milks. In ‘Handbook of milk composition’. (Ed. RG Jensen) pp. 237–271. (Academic Press: San Diego, CA, USA)
Kaps M, Herring WO, Lamberson WR (1999) Genetic and environmental parameters for mature weight in Angus cattle. Journal of Animal Science 77, 569–574.
| Genetic and environmental parameters for mature weight in Angus cattle.Crossref | GoogleScholarGoogle Scholar | 10229351PubMed |
Koots KR, Gibson JP, Wilton JW (1994) Analyses of published genetic parameter estimates for beef production traits. 2. Phenotypic and genetic correlations. Animal Breeding Abstracts 62, 825–853.
Krizsan SJ, Huhtanen P (2013) Effect of diet composition and incubation time on feed indigestible neutral detergent fiber concentration in dairy cows. Journal of Dairy Science 96, 1715–1726.
| Effect of diet composition and incubation time on feed indigestible neutral detergent fiber concentration in dairy cows.Crossref | GoogleScholarGoogle Scholar | 23312997PubMed |
Lancaster PA, Tedeschi LO, Buessing Z, Davis ME (2021) Assessment of milk yield and nursing calf feed intake equations in predicting calf feed intake and weaning weight among breeds. Journal of Animal Science 99, skaa406
| Assessment of milk yield and nursing calf feed intake equations in predicting calf feed intake and weaning weight among breeds.Crossref | GoogleScholarGoogle Scholar | 33373428PubMed |
Lighton JRB (2008) ‘Measuring metabolic rates: a manual for scientists’. (Oxford University Press: New York, NY, USA)
MacNeil MD (2005) Genetic evaluation of the ratio of calf weaning weight to cow weight. Journal of Animal Science 83, 794–802.
| Genetic evaluation of the ratio of calf weaning weight to cow weight.Crossref | GoogleScholarGoogle Scholar | 15753333PubMed |
Mallinckrodt CH, Bourdon RM, Golden BL, Schalles RR, Odde KG (1993) Relationship of maternal milk expected progeny differences to actual milk yield and calf weaning weight. Journal of Animal Science 71, 355–362.
| Relationship of maternal milk expected progeny differences to actual milk yield and calf weaning weight.Crossref | GoogleScholarGoogle Scholar | 8440654PubMed |
Marston TT, Simms DD, Schalles RR, Zoellner KO, Martin LC, Fink GM (1992) Relationship of milk production, milk expected progeny difference, and calf weaning weight in angus and simmental cow–calf pairs. Journal of Animal Science 70, 3304–3310.
| Relationship of milk production, milk expected progeny difference, and calf weaning weight in angus and simmental cow–calf pairs.Crossref | GoogleScholarGoogle Scholar | 1459890PubMed |
McLean JA, Tobin G (1987) ‘Animal and human calorimetry’. (Cambridge University Press: New York, NY, USA)
Meyer K, Carrick MJ, Donnelly BJP (1994) Genetic parameters for milk production of Australian beef cows and weaning weight of their calves. Journal of Animal Science 72, 1155–1165.
| Genetic parameters for milk production of Australian beef cows and weaning weight of their calves.Crossref | GoogleScholarGoogle Scholar | 8056659PubMed |
Miller SP, Wilton JW, Pfeiffer WC (1999) Effects of milk yield on biological efficiency and profit of beef production from birth to slaughter. Journal of Animal Science 77, 344–352.
| Effects of milk yield on biological efficiency and profit of beef production from birth to slaughter.Crossref | GoogleScholarGoogle Scholar | 10100661PubMed |
Milligan LP (1971) Energetic efficiency and metabolic transformations. Federation Proceedings 30, 1454–1458.
Montaño-Bermudez M, Nielsen MK, Deutscher GH (1990) Energy requirements for maintenance of crossbred beef cattle with different genetic potential for milk. Journal of Animal Science 68, 2279–2288.
| Energy requirements for maintenance of crossbred beef cattle with different genetic potential for milk.Crossref | GoogleScholarGoogle Scholar | 2401650PubMed |
Mourer GL (2012) Effects of cow mature size on intake, calf weight and milk yield in a spring-calving commercial cow/calf operation. M.S. thesis, Oklahoma State University, Stillwater, OK, USA.
National Academies of Sciences, Engineering, and Medicine (2016) ‘Nutrient requirements of beef cattle: eighth revised edition’. (The National Academies Press: Washington, DC, USA)
National Research Council (1987) ‘Predicting feed intake of food-producing animals’. (National Academy Press: Washington, DC, USA) Available at https://www.nap.edu/catalog/950/predicting-feed-intake-of-food-producing-animals
National Research Council (2000) ‘Nutrient requirements of beef cattle’. (National Academy Press: Washington, DC, USA)
Northcutt SL, Wilson DE (1993) Genetic parameter estimates and expected progeny differences for mature size in Angus cattle. Journal of Animal Science 71, 1148–1153.
| Genetic parameter estimates and expected progeny differences for mature size in Angus cattle.Crossref | GoogleScholarGoogle Scholar | 8505247PubMed |
Oss DB, Marcondes MI, Machado FS, Tomich TR, Chizzotti ML, Campos MM, Pereira LGR (2016) Technical note: Assessment of the oxygen pulse and heart rate method using respiration chambers and comparative slaughter for measuring heat production of cattle. Journal of Dairy Science 99, 8885–8890.
| Technical note: Assessment of the oxygen pulse and heart rate method using respiration chambers and comparative slaughter for measuring heat production of cattle.Crossref | GoogleScholarGoogle Scholar | 27544858PubMed |
Pitchford WS, Lines DS, Wilkes MJ (2018) Variation in residual feed intake depends on feed on offer. Animal Production Science 58, 1414–1422.
| Variation in residual feed intake depends on feed on offer.Crossref | GoogleScholarGoogle Scholar |
Reynoso-Campos O, Fox DG, Blake RW, Barry MC, Tedeschi LO, Nicholson CF, Kaiser HM, Oltenacu PA (2004) Predicting nutritional requirements and lactation performance of dual-purpose cows using a dynamic model. Agricultural Systems 80, 67–83.
| Predicting nutritional requirements and lactation performance of dual-purpose cows using a dynamic model.Crossref | GoogleScholarGoogle Scholar |
Ribeiro FRB, Tedeschi LO, Stouffer JR, Carstens GE (2008) Technical note: A novel technique to assess internal body fat of cattle by using real-time ultrasound. Journal of Animal Science 86, 763–767.
| Technical note: A novel technique to assess internal body fat of cattle by using real-time ultrasound.Crossref | GoogleScholarGoogle Scholar |
Rumph JM, Van Vleck LD (2004) Age-of-dam adjustment factors for birth and weaning weight records of beef cattle: a review. Genetics and Molecular Research 3, 1–17.
Scholljegerdes EJ, Summers AF (2016) How do we identify energetically efficient grazing animals? Journal of Animal Science 94, 103–109.
| How do we identify energetically efficient grazing animals?Crossref | GoogleScholarGoogle Scholar |
Smith SB, Crouse JD (1984) Relative contributions of acetate, lactate and glucose to lipogenesis in bovine intramuscular and subcutaneous adipose tissue. Journal of Nutrition 114, 792–800.
| Relative contributions of acetate, lactate and glucose to lipogenesis in bovine intramuscular and subcutaneous adipose tissue.Crossref | GoogleScholarGoogle Scholar |
Solis JC, Byers FM, Schelling GT, Long CR, Greene LW (1988) Maintenance requirements and energetic efficiency of cows of different breed types. Journal of Animal Science 66, 764–773.
| Maintenance requirements and energetic efficiency of cows of different breed types.Crossref | GoogleScholarGoogle Scholar | 3378932PubMed |
Tedeschi LO, Fox DG, Guiroy PJ (2004) A decision support system to improve individual cattle management. 1. A mechanistic, dynamic model for animal growth. Agricultural Systems 79, 171–204.
| A decision support system to improve individual cattle management. 1. A mechanistic, dynamic model for animal growth.Crossref | GoogleScholarGoogle Scholar |
Tedeschi LO, Fox DG, Doane PH (2005) Evaluation of the tabular feed energy and protein undegradability values of the National Research Council Nutrient Requirements of Beef Cattle. The Professional Animal Scientist 21, 403–415.
| Evaluation of the tabular feed energy and protein undegradability values of the National Research Council Nutrient Requirements of Beef Cattle.Crossref | GoogleScholarGoogle Scholar |
Tedeschi LO, Fox DG, Baker MJ, Long KL (2006) A model to evaluate beef cow efficiency. ‘Nutrient digestion and utilization in farm animals: modelling approaches’. (Eds E Kebreab, J Dijkstra, A Bannink, WJJ Gerrits, J France) pp. 84–98. (CABI Publishing: Cambridge, MA, USA)
Tedeschi LO, Kononoff PJ, Karges K, Gibson ML (2009) Effects of chemical composition variation on the dynamics of ruminal fermentation and biological value of corn milling (co)products. Journal of Dairy Science 92, 401–413.
| Effects of chemical composition variation on the dynamics of ruminal fermentation and biological value of corn milling (co)products.Crossref | GoogleScholarGoogle Scholar | 19109298PubMed |
Thompson WR, Meiske JC, Goodrich RD, Rust JR, Byers FM (1983) Influence of body composition on energy requirements of beef cows during winter. Journal of Animal Science 56, 1241–1252.
| Influence of body composition on energy requirements of beef cows during winter.Crossref | GoogleScholarGoogle Scholar | 6863170PubMed |
Van Soest PJ, Robertson JB, Lewis BA (1991) Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition. Journal of Dairy Science 74, 3583–3597.
| Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition.Crossref | GoogleScholarGoogle Scholar | 1660498PubMed |
Veerkamp RF, Emmans GC (1995) Sources of genetic variation in energetic efficiency of dairy cows. Livestock Production Science 44, 87–97.
| Sources of genetic variation in energetic efficiency of dairy cows.Crossref | GoogleScholarGoogle Scholar |
Wagner JJ, Lusby KS, Oltjen JW, Rakestraw J, Wettemann RP, Waiters LE (1988) Carcass composition in mature Hereford cows: estimation and effect on daily metabolizable energy requirement during winter. Journal of Animal Science 66, 603–612.
| Carcass composition in mature Hereford cows: estimation and effect on daily metabolizable energy requirement during winter.Crossref | GoogleScholarGoogle Scholar | 3378920PubMed |
Walker RS, Martin RM, Gentry GT, Gentry LR (2015) Impact of cow size on dry matter intake, residual feed intake, metabolic response, and cow performance. Journal of Animal Science 93, 672–684.
| Impact of cow size on dry matter intake, residual feed intake, metabolic response, and cow performance.Crossref | GoogleScholarGoogle Scholar | 25548208PubMed |
Wu G (2017) ‘Principles of animal nutrition’. (CRC Press: Boca Raton, FL, USA)
Weiss WP, Conrad HR, St. Pierre NR (1992) A theoretically-based model for predicting total digestible nutrient values of forages and concentrates. Animal Feed Science and Technology 39, 95–110.
| A theoretically-based model for predicting total digestible nutrient values of forages and concentrates.Crossref | GoogleScholarGoogle Scholar |
