Feed efficiency of lactating Holstein cows is repeatable within diet but less reproducible when changing dietary starch and forage concentrations

Authors: FISCHER, AMELIE - Oak Ridge Institute For Science And Education (ORISE); DAI, XIAOXIA - Former ARS Employee; Kalscheur, Kenneth

Submitted to: Animal-The International Journal of Animal Biosciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2022
Publication Date: 7/27/2022
Citation: Fischer, A., Dai, X., Kalscheur, K. 2022. Feed efficiency of lactating Holstein cows is repeatable within diet but less reproducible when changing dietary starch and forage concentrations. Animal-The International Journal of Animal Biosciences. 16(8). Article 100599. https://doi.org/10.1016/j.animal.2022.100599.
DOI: https://doi.org/10.1016/j.animal.2022.100599

Interpretive Summary: Improving feed efficiency is key for dairy farmers to maintain their production by using fewer resources, especially by decreasing feeds that are directly edible for human consumption. This study analyzed the ability of lactating dairy cows to maintain their feed efficiency when changing the dietary starch and forage concentrations. Cows were able to maintain their feed efficiency over time when fed the same diet, but fewer cows maintained their efficiency when the diet was changed. These results suggest that feed efficiency should be considered within the same diet to avoid any misidentification of cows as most or least efficient. This research will be of interest to dairy producers, nutritionists, and researchers interested in developing nutritional strategies that may affect feed efficiency in lactating dairy cows.

Technical Abstract: Improving feed efficiency has become an important target for dairy farmers to produce more milk with fewer feed resources. With decreasing availability of arable land to produce feeds that are edible for human consumption, it will be important to increase the proportion of feeds in the diets for dairy cattle that are less edible for human consumption. The current research analysed the ability of lactating dairy cows to maintain their feed efficiency when switching between a high starch diet (HS diet: 27% starch, 29% NDF, 47.1% forages on a DM basis) and a low starch diet (LS diet: 13% starch, 37% NDF, 66.4% forages on a DM basis). Sixty-two lactating Holstein cows (137 +/- 23 days in milk (DIM) at the start of experiment), of which 29 were primiparous cows, were utilized in a crossover design with two 70-d experimental periods, including a 14-d adaption period for each. Feed efficiency was estimated as the individual deviation from the population average intercept in a mixed model predicting dry matter intake (DMI) with net energy in milk, maintenance and body weight gain and loss. Repeatability was estimated within each diet by comparing feed efficiency estimated over the first 28-day period and the second 28-day period within each diet, using Pearson’s and intraclass correlations, and the estimation of error of repeatability. Similarly, reproducibility was estimated by comparing the second 28-day period of one diet with the first 28-day period of the other diet. Feed efficiency was less reproducible across diets than repeatable within the same diet. This was shown by lower intraclass correlations (0.399) across diets compared to that in the HS diet (0.587) and LS diet (0.806), as well as lower a Pearson’s correlation coefficient (0.418) across diets compared to that in the HS diet (0.630) and LS diet (0.809). In addition, the estimation of error of repeatability was higher (0.830 kg DM/d) across diets compared to that in the HS diet (0.761 kg DM/d) and LS diet (0.504 kg DM/d). This means that feed efficiency of dairy cows is more likely to change after a diet change than over subsequent lactation stages. Other determinants, such as digestive processes, needs to be further investigated to determine its effects on estimating feed efficiency.