Comparison of milk production, intake, and total-tract nutrient digestion in lactating dairy cattle fed diets containing either wheat middlings and urea, commercial fermentation by-product, or rumen-protected soybean meal

Feed-food and land use competition of lowland and mountain dairy cow farms

Dairy cows and other ruminants contribute to human nutrition as they are able to convert feed components containing human inedible fibre concentrations (e.g. roughage and by-products from the food processing industry) into valuable animal-sourced food. A number of crops often fed to dairy cows (e.g. soy or cereals) are however potentially edible by humans too. Additionally, land used to grow dairy cattle feed may compete with crop production for human consumption. Two different methods to assess the competition between feed consumption of dairy cows and human food supply were thus refined and tested on 25 Swiss dairy farms. With respect to the potential human edibility of the feeds used in dairy production, the human-edible feed conversion ratio (eFCR) was applied. The land use ratio (LUR) was used to relate the food production potential, per area of land utilised, with the dairy production output. Low to medium eFCR, with values ranging from 0.02 to 0.68 were found, as an average proportion of 0.74 of total DM intake consisted of roughage. In contrast, we found relatively high LUR (0.69-5.93) for most farms. If the land area used to produce feed for cows was used for crop production (applying a crop rotation), 23 of the 25 farms could have produced more edible protein and all farms more human-edible energy. Indicator values strongly depend on the underlying scenarios, such as the human-edible proportion of feeds or the suitability of land and climate for crop production. Reducing the amount of human-edible feeds in dairy farming by feeding by-products from the food processing industry and improving forage quality may be suitable strategies to reduce eFCR, but relying on low-opportunity cost feeds may restrict milk performance level per cow. On farm level, improving overall efficiency and therefore using less land (especially area suitable for crop production) per kg product decreases LUR. However, the most promising strategy to mitigate land use competition may be to localise dairy production to land areas not suitable for crop production. Both methods (eFCR and LUR) should be used in parallel. They offer an opportunity to holistically evaluate the net contribution of dairy production to the human food supply under different environmental conditions and stress the importance of production systems well suited to specific farm site characteristics.

Predicting fibre digestibility in Holstein dairy cows fed dry-hay-based rations through machine learning

Calculating the requirements and predicting the feed digestibility are essential to building robust dairy cattle rationing programmes. In the field, a huge number of in vivo observations are needed to develop accurate equations and reliable predictions. The aim of this study was to develop an equation to estimate total-tract potentially digestible NDF digestibility (TTpdNDFD) for lactating cows fed hay-based rations. Individual data from 11 studies, 69 cows, 35 different treatments, and 1 614 observations were included in this study. To develop the prediction equation, the following traits, descriptors of the total mixed ration, were used: ash, starch, CP, NDF, acid detergent fibre, acid detergent lignin, undegradable NDF and potential degradable NDF. Before building the equation with bidirectional stepwise selection in the JMP software, outliers were removed and multicollinearity was checked for all the predictors of fibre digestibility. The model was trained with 10-folds cross-validation. Results showed an R2 of 0.91 and 0.90, and a RMSE of 2.99 and 3.26 in the model for training and validation, respectively. The promising performance of the model suggested that, the fibre digestibility in lactating dairy cows fed dry-hay-based rations can be accurately predicted in advance just by using the diet characteristics. From the obtained equation, we predicted the weight and slope of the included covariates, and outcomes confirm that in general the TTpdNDFD is reduced as dietary starch and fast-fermentable fibre increase. This study found that the equation extracted from a neural network, when combined with precision farming techniques, can improve the management of lactating cows and optimise feed planning, monitoring, and cost. It can be used in areas where silages are not used in rations. This provides evidence that accurate equations can be developed from historical data for precision feeding implementation. Further research is needed to expand the dataset and develop equations that can be applied on a large scale. Improving accuracy would involve incorporating representative data from other areas with similar diets into the training set.

Poultry by-product meal as a replacement to xylose-treated soybean meal in diet of early- to mid-lactation Holstein cows

The objectives were to compare the effectiveness of poultry by-product meal (PBM) with xylose-treated soybean meal (x-SBM) as a conventional protein source and rumen-undegraded protein (RUP):rumen-degraded protein (RDP) ratio on nutrient digestibility, nitrogen metabolism, and production of early- to mid-lactation Holsteins. Twelve multiparous cows averaging (mean ± SD) 50 ± 9 days in milk were randomly assigned to a replicated 4 × 4 Latin square design within a 2 × 2 factorial arrangement of treatments. Each period was 28 days in length. Treatments were RUP sources (PBM or x-SBM) with either a high or a low RUP:RDP ratio (high ratio = 40:60 or low ratio = 36:64; based on % of crude protein (CP)). Experimental diets were balanced to be similar in protein and energy contents (CP = 16.7% of DM; NEL = 1.67 Mcal/kg DM). Prior to diet formulation, an in situ pilot experiment was conducted to estimate the RUP fractions of x-SBM and PBM as 63.9% and 54.1% of CP, respectively. Treatments had no effect on ruminal pH and total volatile fatty acid (VFA) and molar percentage of individual VFAs. Treatments had no effect on total tract apparent digestibility of DM, OM, and neutral detergent fiber (NDF), with the exception of N that was greater in diets with a low RUP:RDP ratio (68.2 vs. 70.1% of DM). DM consumption was 0.70 kg/day higher when cows were fed PBM diet compared with x-SBM diet. No treatment effect was observed on milk yield and milk composition; however, milk protein yield and milk urea N were greater in cows fed PBM. Inclusion of PBM in the diet in substitution to x-SBM resulted in increased blood levels of urea N, cholesterol, and non-esterified fatty acid (NEFA). There was no interaction between the RUP source and the RUP:RDP ratio for urinary and fecal N excretion. Efficiency of N utilization expressed as milk N secretion as a proportion of N intake tended to be greater in cows fed PBM. Feeding diets with a low ratio of RUP:RDP increased efficiency of milk production expressed as milk yield as a proportion of total N excretion (fecal and urinary N). Feeding a diet with PBM supported milk production comparable with x-SBM and had positive effects on feed intake, milk protein yield, and milk N efficiency.