Dietary energy, milk yield and milk profile in jennies

Metabolome and proteome were analysed only for low vs. medium energy; why the high level gave less milk remains open, as the authors themselves acknowledge. For the proteome, one figure legend gives n = 4; the group size of the metabolome analyses is not stated explicitly.

The results text describes feed intake as rising and then falling, but Table 2 shows a steady rise (6.80 – 7.20 – 8.02 kg/d). Contrary to the text, lactose was highest at the high level (6.57 %), and fat content did not differ significantly (p = 0.102 and 0.108), although the abstract and text report an increase in milk constituents.

According to the methods section, the forage to concentrate ratio was 30:70; according to Table 1, however, the rations consist of around 70 % millet straw, alfalfa and maize silage. In addition, alfalfa (30.0 vs. 4.5 %), millet straw (26.9 vs. 54.8 %) and crude fat (4.46 vs. 2.82–2.96 %) vary strongly, so energy effects cannot be separated from effects of the feed components.

Free fatty acids in serum are given as 191–403 mmol/L, which appears about 1000 times too high (probably µmol/L). The values for AST (4.2–5.0 U/L) and ALT (315–378 U/L) seem unusual. For OTU clustering, the methods section gives 97 % and the results section 82.35 % similarity, and the number of jointly enriched pathways is given once as 75 and once as 73.

What was recorded was the amount obtained after 6 hours of foal separation; the daily amount is extrapolated. The link between metabolic pathways and milk performance is based on correlations and enrichment analyses and was not tested experimentally. Effects in humans were not the subject of the study.

Three graded energy levels, random allocation, weekly measurement with the pre-period as a covariate and orthogonal contrasts allow a systematic dose–response assessment. Tables contain means, SEM and p-values; the sequence data are publicly deposited.