Details

Autor(en) / Beteiligte

• Gross, Megan A
• Holder, Amanda L
• Moehlenpah, Alexi N
• Freetly, Harvey C
• Goad, Carla L
• Beck, Paul A
• DeVuyst, Eric A
• Lalman, David L

Titel

Predicting feed intake in confined beef cows

Ist Teil von

• Translational animal science, 2024-01, Vol.8, p.txae001-txae001

Ort / Verlag

US: Oxford University Press

Erscheinungsjahr

2024

Link zum Volltext

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Abstract Six existing equations (three for nonlactating and three for lactating; NRC, 1987, Predicting feed intake of food-producing animals. Washington, DC: The National Academies Press, National Academy of Science; doi: 10.17226/950; NRC, 1996, Nutrient requirements of beef cattle, 7th Revised Edition: Update 1996. Washington, DC: The National Academies Press; doi: 10.17226/9791; Hibberd and Thrift, 1992. Supplementation of forage-based diets. J. Anim. Sci. 70:181. [Abstr]) were evaluated for predicting feed intake in beef cows. Each of the previously published equations are sensitive to cow-shrunk BW and feed energy concentration. Adjustments in feed intake prediction are provided for level of milk yield in NRC (1987. Predicting feed intake of food-producing animals. Washington, DC: The National Academies Press, National Academy of Science; doi: 10.17226/950) and NRC (1996 Nutrient requirements of beef cattle, 7th Revised Edition: Update 1996. Washington, DC: The National Academies Press; doi: 10.17226/9791) equations. The equation published in 1996 used data generated between 1979 and 1993. Our objectives were to validate the accuracy of the published equations using more recent data and to propose alternative prediction models. Criteria for inclusion in the evaluation dataset included projects conducted or published since 2002, direct measurement of feed intake, adequate protein supply, and pen feeding (no metabolism crate data). After removing outliers, the dataset included 53 treatment means for nonlactating cows and 32 treatment means for lactating cows. Means for the nonlactating dataset were dry matter intake (DMI) = 13.2 ± 2.9 kg/d, shrunk body weight (SBW) = 578 ± 83.9 kg, body condition score = 5.7 ± 0.73, and Mcal net energy for maintenance (NEm)/kg of feed = 1.27 ± 0.15 Mcal/kg. Means for the lactating dataset were DMI = 14.6 ± 2.24 kg/d, SBW = 503 ± 73.4 kg, body condition score = 4.7 ± 0.58, and Mcal NEm/kg feed = 1.22 ± 0.16. Simple linear regression was used to determine slope, intercept, and bias when observed DMI (y) was regressed against predicted DMI (x). The NRC (1996. Nutrient requirements of beef cattle, 7th Revised Edition: Update 1996. Washington, DC: The National Academies Press; doi: 10.17226/9791) nonlactating equation underestimated feed intake in diets moderate to high in energy density with intercept differing from 0 and slope differing from one (P ≤ 0.01). Average deviation from observed values was 2.4 kg/d. Similarly, when the NRC (1996. Nutrient requirements of beef cattle, 7th Revised Edition: Update 1996. Washington, DC: The National Academies Press; doi: 10.17226/9791) equation was used to predict DMI in lactating cows, the slope differed from one (P < 0.01) with average deviation from observed values of 3.0 kg/d. New models were developed by pooling the two datasets and including a categorical variable for stage of production (0 = nonlactating and 1 = lactating). Continuous variables included study-average SBW0.75 and diet NEm, Mcal/kg. The best-fit empirical model accounted for 68% of the variation in daily feed intake with standard error of the estimate Sy root mean squared error = 1.31. The proposed equation needs to be validated with independent data. An independent dataset was used to evaluate equations available to estimate feed intake in beef cows. One equation (Hibberd and Thrift, 1992. Supplementation of forage-based diets. J. Anim. Sci. 70:181. [Abstr]) provided a reasonably accurate estimate of feed intake for lactating cows, although the equation from the same authors overestimated feed intake in nonlactating cows. Lay Summary An accurate estimate of feed intake is a critical component in developing cost-effective, sustainable management systems and supplementation programs for beef cows. Equations currently being used to estimate feed intake in beef cows were generated using data published between 1979 and 1993. In an effort to evaluate the accuracy and precision of six previously published equations, we reviewed the literature and generated a validation dataset restricted to studies either conducted or published since 2002. The final dataset included 53 treatment means for nonlactating cows and 32 treatment means for lactating cows. None of the three published equations for nonlactating cows provided an accurate estimate of feed intake. However, the equation developed by Hibberd and Thrift (1992. Supplementation of forage-based diets. J. Anim. Sci. 70:181. [Abstr]) performed well for lactating beef cows. The National Research Council (Nutrient requirements of beef cattle. 7th revised ed.: Update 1996. Washington, DC: Natl. Acad. Press; doi: 10.17226/9791) equation underestimated feed intake substantially in lactating beef cows. A new prediction model was developed using the evaluation dataset. Predictor variables in the new equation included stage of production, body weight, and diet energy concentration. This equation accounted for 68% of the variation in daily feed intake and may represent an improvement in prediction of feed intake for beef cows, although independent validation is needed.