Evaluation and quantification of associations between commonly suggested milk biomarkers and the proportion of grassland-based feeds in the diets of dairy cows.

This study is a first step approach towards the prediction of the proportion of grassland-based feeds (%GB) in dairy cow diets with the aid of three different groups of milk biomarkers. We aimed to evaluate and quantify the associations between biomarkers commonly suggested in the literature and %GB in individual cows as a hypothesis-generating stage for the prospective establishment of accurate %GB prediction models. Consumers and governments financially encourage sustainable, local milk production making grass-based feeding, in grassland-dominated regions, of major interest. Milk from grassland-fed cows differs from that of other feeding systems by inferential fatty acids (FA), ß-carotene content and yellow color; however, these biomarkers have not been evaluated together for their association with %GB. Using approved methods of parametric regression analysis, gas chromatography (GC), mid-infrared spectra (MIR) and color spectroscopy, we aimed to develop a first step towards an easy-to-implement, cost-effective milk-based control to estimate %GB in dairy cow diets. The underlying database was generated with 24 cows each fed one of 24 different diets gradually increasing in grass silage and decreasing in corn silage. Our results indicate that GC-measured α-linolenic acid, total n-3 FA and the n-6:n-3 ratio, MIR-estimated PUFA and milk red-green color index a* are robust milk biomarkers for constructing accurate prediction models to determine %GB. Based on simplified regression analysis, diets containing 75% GB should contain ≥ 0.669 and 0.852 g α-linolenic acid and total n-3 FA per 100 g total FA, respectively, and an n-6:n-3 FA ratio of < 2.02 measured with GC; estimated with MIR, polyunsaturated FA should be ≥ 3.13 g/100 g total FA. ß-carotene was not a good predictor for estimating %GB. Unexpectedly, the milk became greener with increasing %GB (negative a* values, ‒6.416 for 75% GB), suggesting the red-green color index, not yellow-blue, as a suitable biomarker.

Effects of incremental increases in grass silage proportions from different harvest years on methane emissions, urinary nitrogen losses, and protein and energy utilisation in dairy cows.

Dairy cows, methane and global warming have become publicly related terms. However, appropriate dairy cow management may in fact be part of the climate solution when viewed as part of the biogenic carbon cycle. Accordingly, governments and consumers are encouraging more sustainable, locally produced, climate friendly dairy production that often includes grassland-based feeding. However, this system is presumed to result in greater methane emissions compared to corn silage- or concentrate-based diets. An increase in urine nitrogen, associated with increased ammonia and nitrous oxide emission potential, questions the environmental usefulness of this strategy pertaining to global warming. This study is the first to compare the effects of incremental increases of grass silage proportion on enteric methane production as well as N and energy losses in dairy cows. Twenty-four mid- to end-lactation dairy cows were each fed one of 24 different diets, from two different harvest years, gradually increasing in grassland-based feeds (grass silage and hay) from about 500 to 1000 g/kg and concomitantly decreasing in corn silage. Each cow underwent a 7-day total collection period and was housed for 48 h in respiration chambers. Incremental data were subjected to an approved parametric regression analysis approach. The dietary increase in grassland-based feeds did not impair milk yield, N and energy utilisation. Simplified regression equations revealed that, contrary to current assumptions, there was a decline in methane production from 373 to 303 g/day when increasing grassland-based feeds from 500 to 1000 g/kg diet, and there was a trend for a decline in emission intensity from 20.6 to 17.6 g/kg of energy-corrected milk. However, urine nitrogen emissions clearly increased even when related to nitrogen intake; the latter from 260 to 364 g/kg when increasing grassland-based feeds from 500 to 1000 g/kg. Methane and urine nitrogen emissions were not affected by year of harvest.

Soybean Meal Can Be Replaced by Faba Beans, Pumpkin Seed Cake, Spirulina or Be Completely Omitted in a Forage-Based Diet for Fattening Bulls to Achieve Comparable Performance, Carcass and Meat Quality.

The aim of the study was to investigate the complete substitution of imported soybean meal in beef cattle diets and the consequences on performance, meat, and adipose tissue quality. Thirty growing crossbred Limousin bulls, with an initial bodyweight of 164 ± 13 kg and 4.3 ± 0.3 months of age, were fed a grass/maize-silage based diet with little additional concentrate (0.5:0.3:0.2). Concentrates contained either soybean meal (positive control), faba beans, pumpkin seed cake, or spirulina (Arthrospira platensis), resulting in about 226 g crude protein (CP)/kg concentrate dry matter (DM) and 158 g CP/kg total diet DM. A grain-based concentrate providing just 135 g CP/kg concentrate DM and 139 g CP/total diet DM served as a negative control. Bulls of all groups had comparable average daily gains (1.43 ± 0.1 kg) and feed intakes (6.92 ± 0.37 kg). Carcass and meat quality did not differ among groups. The fatty acid profile of meat lipids was hardly affected. These results indicate that soybean meal can be replaced by any of the tested protein sources without impairing performance or meat quality. Importantly, bulls fed the negative control achieved a fattening and slaughter performance comparable to that of the protein-supplemented groups without affecting meat and adipose tissue quality. Thus, the present findings suggest that feeding crossbred bulls a grass/maize-silage based diet does not require additional protein supplementation.

Effects of full-time v. part-time grazing on seasonal changes in milk coagulation properties and fatty acid composition.

For this research communication our objective was to investigate to what extent milk coagulation properties and milk fatty acid (FA) composition were affected by different feeding systems, season and their interaction. Eighteen cows in total were subjected to one of three different feeding system treatments: full-time grazing or part-time grazing combined with indoor feeding of fresh grass with low or high concentrate supplementation. Milk was sampled in spring, summer and autumn. Milk coagulation time was 15.0, 19.0 and 17.7 min, coagulation dynamics 1.67, 3.41 and 1.79 min, and curd firmness 52.7, 32.4 and 47.0 mm in spring, summer and autumn, respectively. Thus, milk coagulation properties of the milk were lower during summer. There were strong seasonal effects on milk FA proportions, but there were not always changes with progressing season, or changes were different with respect to the impact of the feeding systems (system × season interaction). The milk fat was favourably rich in oleic acid, conjugated linoleic acid and α-linolenic acid and had a low n-6/n-3 fatty acid ratio in all systems. Factors like seasonal variations in grass composition and the energy balance of the cows were considered relevant for the milk FA composition. Overall, seasonal variations in milk quality were less pronounced with part-time grazing with fresh grass indoors as compared to full-time grazing without concentrate.

Association of specific expansins with growth in maize leaves is maintained under environmental, genetic, and developmental sources of variation.

We aimed to evaluate whether changes in maize (Zea mays) leaf expansion rate in response to environmental stimuli or developmental gradients are mediated by common or specific expansins, a class of proteins known to enhance cell wall extensibility. Among the 33 maize expansin or putative expansin genes analyzed, 19 were preferentially expressed at some point of the leaf elongation zone and these expansins could be organized into three clusters related to cell division, maximal leaf expansion, and cell wall differentiation. Further analysis of the spatial distribution of expression was carried out for three expansins in leaves displaying a large range of expansion rates due to water deficit, genotype, and leaf developmental stage. With most sources of variation, the three genes showed similar changes in expression and consistent association with changes in leaf expansion. Moreover, our analysis also suggested preferential association of each expansin with elongation, widening, or both of these processes. Finally, using in situ hybridization, expression of two of these genes was increased in load-bearing tissues such as the epidermis and differentiating xylem. Together, these results suggest that some expansins may be preferentially related to elongation and widening after integrating several spatial, environmental, genetic, and developmental cues.

Are ABA, ethylene or their interaction involved in the response of leaf growth to soil water deficit? An analysis using naturally occurring variation or genetic transformation of ABA production in maize.

The role of abscisic acid (ABA) and its possible interaction with ethylene in mediating leaf elongation response to soil water deficit are a matter of controversy. To address this question, we used a set of maize genotypes with various levels of ABA either due to natural variability or to genetic transformation targeted on NCED/VP14, a key enzyme of ABA synthesis. The transgenic lines yielded less strong phenotypes than available mutants, making it possible to use them under normal growing conditions. We focused on leaf elongation during night periods in order to avoid the confounding effect of ABA on leaf water status. Our results suggest that over a wide range, internal ABA level (measured in both leaf extracts or xylem sap) has no clear effect on leaf elongation response to soil water deficit, except in the case of an antisense line presenting the strongest reduction in ABA accumulation that showed a slight maintenance of leaf elongation during water deficit. Leaf ethylene production rate was variable and not related to water deficit except in the ABA-deficient transgenic lines where it was increased by water deficit on average but not systematically. Moreover, variability in ethylene production rate was not linked to variability in elongation rate. Our results thus suggest that neither ABA nor ethylene seems to play a major role in the control of leaf elongation response to soil water deficit.