Comparison of four techniques to estimate milk production in singleton-rearing non-dairy ewes |
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| Institution: | 1. Sheep Research Group, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand;2. National Research Centre for Growth and Development, Massey University, Private Bag 11222, Palmerston North, New Zealand;3. Liggins Institute, University of Auckland, Private Bag 92019, Auckland, New Zealand;1. Palaeontological Institute and Museum, University of Zurich, 8006 Zurich, Switzerland;2. Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland;1. Campo Experimental La Laguna, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP), Blvd. José Santos Valdez No.1200 Poniente, C.P 27440, Matamoros, Coahuila, Mexico;2. Centro de Investigación en Reproducción Caprina (CIRCA), Posgrado en Ciencias Agrarias, Universidad Autónoma Agraria Antonio Narro, Periférico Raúl López Sánchez y Carretera a Santa Fe, C.P. 27054, Torreón, Coahuila, Mexico;1. Department of Medical Neuroscience, Dalhousie University, Halifax, N.S. B3H 4R2, Canada;2. Department of Biology, Mount Saint Vincent University, 166 Bedford Highway, Halifax, N.S. B3M 2J6, Canada;1. Department of Animal Science, “Luiz de Queiroz” College of Agriculture, University of São Paulo, Pádua Dias Avenue, n 11, PO Box 09, Piracicaba, São Paulo, 13418-900, Brazil;2. Department of Nutrition and Animal Production, FMVZ, University of São Paulo, Duque de Caxias North Avenue, n 225, Pirassununga, São Paulo, 13635-000, Brazil;3. GRASP Ind. & Com. LTDA, Curitiba, Paraná 81260-000, Brazil;1. Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias. Campo Experimental San Luis, San Luis Potosí, San Luis Potosí 78431, Mexico;2. Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias. Centro Nacional de Investigación Disciplinaria Fisiología y Genética Animal, Ajuchitlán, Querétaro 76280, Mexico;1. Universidad Autónoma Chapingo-URUZA, Bermejillo, Durango, 35230, Mexico;2. Universidad de Córdoba-IDEP, Córdoba, 14014, España;3. Universidad Autónoma Agraria Antonio Narro-UL, Torreón, Coahuila, 27054, Mexico;4. Universidad Juárez del Estado de Durango, Facultad de Ciencias Biológicas, Gómez Palacio, Durango, 35010, Mexico;5. INIFAP-Campo Experimental San Luis Potosí, SLP, 78431, Mexico;6. Universidad Autónoma de Baja California-ICA, Mexicali, BC, 21705, Mexico |
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| Abstract: | Accurate estimates of milk production or milk intake are difficult, as all methods interfere to some degree with the natural behaviour of the dam and her young, and potentially alter milk yield itself. The present study compared milk yield obtained by the “oxytocin” method, udder dimensions (UD), the isotope dilution method, and live weight change of the lamb, in an attempt to select the most accurate and convenient way of measuring milk production in non-dairy sheep. In addition, the study investigated which of the three milk-estimation techniques was an accurate predictor of growth rates of lambs. Thirty-seven singleton-bearing and rearing ewes were milked once a week, for seven consecutive weeks, using the “oxytocin” method. Prior to each afternoon milking, the external dimensions of the ewe's udder were measured. Lambs were weighed weekly for the first seven weeks of life and live weight change was calculated. The deuterium oxide (D2O) dilution technique was used to estimate milk intake of the lambs and performed at approximately 7 days post-partum and finishing on approximately day 14. Pearson's correlation coefficients and multiple regression coefficients among techniques were calculated. The UD-models at d7 (R2 = 0.35), d35 (R2 = 0.36) and d42 (R2 = 0.34), were the best models explaining variation in milk yield (concordance correlation coefficient (CCC) = 0.49; 0.53; 0.51; for d7, d35 and d42, respectively). The lamb live weight-change model explained the variation in milk yield best at d28 (R2 = 0.32; CCC = 0.49), at d35 (R2 = 0.22; CCC = 0.36) and at d42 (R2 = 0.28; CCC = 0.44). At d14, the intake of milk by lambs as measured by the D2O technique, did not explain the variation in milk yield. In conclusion, udder dimensions, lamb live weight change and lamb milk intake are relatively poor estimators of the milk yield of singleton-rearing ewes obtained by the “oxytocin” method. Additionally, udder dimensions, milk yield and lamb milk intake do not give an accurate prediction of growth rates of singleton lambs. These results emphasize that there is a difference between ewe milk production potential and lamb milk intake, which need to be considered when estimating milk production in non-dairy animals. |
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