Mårten Hetta

In vitro degradation characteristics of Timothy and Red Clover at different harvest times

The nutritional value of red clover (Trifolium pratense L.) and timothy (Phleum pratense L.) were studied over two consecutive growing seasons (1995 and 1996) with an in vitro gas production technique and chemical analysis. The decline in degradability was more pronounced with increasing maturity in timothy than in red clover during spring growth, but similar during summer growth. Red clover contained more components soluble in neutral detergent solution (NDS) at all harvest occasions. The fractional degradation rate for the NDS fraction was lower in red clover compared to timothy. Red clover had slightly higher fractional degradation rate for the whole forage, but the total kinetic release of energy was similar for the two species at the same harvest time. The results indicate that timothy and red clover have different intrinsic characteristics limiting degradation. Effects of the treatments with NDS on the allocation of pectins could partially explain the differences in degradation characteristics.

Effects of soybean meal or canola meal on milk production and methane emissions in lactating dairy cows fed grass silage-based diets

This study evaluated the effects of soybean meal (SBM) and heat-moisture-treated canola meal (TCM) on milk production and methane emissions in dairy cows fed grass silage-based diets. Twenty-eight Swedish Red cows were used in a cyclic change-over experiment with 4 periods of 21 d and with treatments in 2 × 4 factorial arrangement (however, the control diet without supplementary protein was not fed in replicate). The diets were fed ad libitum as a total mixed ration containing 600 g/kg of grass silage and 400 g/kg of concentrates on a dry matter (DM) basis. The concentrate without supplementary protein consisted of crimped barley and premix (312 and 88 g/kg of DM), providing 130 g of dietary crude protein (CP)/kg of DM. The other 6 concentrates were formulated to provide 170, 210, or 250 g of CP/kg of DM by replacing crimped barley with incremental amounts of SBM (50, 100, or 150 g/kg of diet DM) or TCM (70, 140, or 210 g/kg of diet DM). Feed intake was not influenced by dietary CP concentration, but tended to be greater in cows fed TCM diets compared with SBM diets. Milk and milk protein yield increased linearly with dietary CP concentration, with greater responses in cows fed TCM diets compared with SBM diets. Apparent N efficiency (milk N/N intake) decreased linearly with increasing dietary CP concentration and was lower for cows fed SBM diets than cows fed TCM diets. Milk urea concentration increased linearly with increased dietary CP concentration, with greater effects in cows fed SBM diets than in cows fed TCM diets. Plasma concentrations of total AA and essential AA increased with increasing dietary CP concentration, but no differences were observed between the 2 protein sources. Plasma concentrations of Lys, Met, and His were similar for both dietary protein sources. Total methane emissions were not influenced by diet, but emissions per kilogram of DM intake decreased quadratically, with the lowest value observed in cows fed intermediate levels of protein supplementation. Methane emissions per kilogram of energy-corrected milk decreased more when dietary CP concentration increased in TCM diets compared with SBM diets. Overall, replacing SBM with TCM in total mixed rations based on grass silage had beneficial effects on milk production, N efficiency, and methane emissions across a wide range of dietary CP concentrations.

Plant development, agronomic performance and nutritive value of forage maize depending on hybrid and marginal site conditions at high latitudes

Abstract The objectives of this investigation were to study the effects of marginal site conditions and hybrid on plant development, agronomic performance and nutritive characteristics of forage maize (Zea mays L.) at high latitudes. Field experiments were conducted in 2008 and 2009 at three experimental sites, Kristianstad, Skara and Västerås, at increasing latitudes from 55°–60° N. Experimental design used two replicated randomized complete blocks at each site with three maize hybrids, Avenir (FAO 180), Isberi (FAO 190) and Burli (FAO 210), which were continuously assessed for plant development and harvested at various levels of maturity. The chemical composition and nutritional characteristics of harvested plant materials were analysed and hybrid responses to advancing maturity in terms of yield and nutritional qualities were evaluated. Results showed that maize hybrids required different numbers of accumulated thermal units at sites on varying latitudes to achieve developmental stages. Lowest thermal unit requirements among hybrids were observed for hybrid Avenir, and for sites it was highest for plants grown in the most northern site, Västerås. The most southern site, Kristianstad, was the only site at which all hybrids reached the dent stage (c. 450 g kg−1 kernel DM), a recommended maturity for ensiling. The DM yields of early maturing hybrid Avenir were consistently lower than those for Isberi and Burli at all the sites. Results also revealed nutritional differences among maize hybrids at a given maturity (DM, g kg−1), indicating that the effects of maturation should be factored into design of hybrid performance trials. This study highlights the effects of marginal site conditions and hybrids on plant development, agronomic performance and nutritional characteristics of maize hybrids at high latitudes. Further studies on marginal sites are recommended to enlighten the understanding of interaction between environmental and genetic factors on the performance of forage maize.

Crop genotype-environment modelling to evaluate forage maize cultivars under climate variability

A crop model and environmental data were used to simulate genotype-environment interactions for commercial forage maize cultivars. Genotype parameters defined by the MAISPROQ model were calibrated to observed aboveground dry matter (DM) yield and quality (concentrations of DM and starch) data from Swedish field experiments 2009–2011 on four forage maize cultivars with different maturation rates (Avenir, Isberi, Jasmic and Burli). The model calibration predictability (coefficient of determination, R2) ranged from 0.18 to 0.45 for yield and 0.40 to 0.86 for quality. The corresponding values for validation were in a similar range for the growth model but less for the quality model (0.36–0.38 and 0.25–0.54, respectively). Thereafter the model was used to assess the cultivar performance for different locations and future climate conditions. The simulated DM yield averaged for 2003–2009 varied between 5% and 25% among nine locations in Sweden due to differences in weather conditions, depending on cultivar. The proportion of years with successful harvest (34% DM concentration being achieved by 31 October) varied between 60% and 100% for the early cultivar (Avenir) and 0% and 70% for the late cultivar (Jasmic). Under future climate conditions, harvest of the early-maturing cultivar (Avenir) will occur earlier (by up to 19 days in Lund [55.6°N] and 24 days in Uppsala [59.8°N] by 2085), but with unchanged or even slightly decreased DM yields compared with current levels. The starch concentration will remain almost unchanged in Lund but increase in Uppsala, especially for the late-maturing cultivar. We regard the model predictions of quality to be reasonably satisfactory, whereas those of DM yields are less reliable due to observations for calibration being available only for the period after flowering. Therefore, more frequent sampling in the early growing season is required to improve the predictive power of the model, especially for DM yield.

Responses in dairy cows to increased inclusion of wheat in maize and grass silage based diets

Abstract The effects of including wheat in the total mixed rations of dairy cows were evaluated using a 4×4 Latin square dose response experiment with 28 dairy cows (Swedish red). The animals were averaging 150 days in milk at the start of the experiment. Diets consisted of mixtures of maize and grass silage with wheat grain at four levels (8, 16, 24 and 32% of dry matter (DM)). The animals consumed 17.8, 19.7, 21.1 and 23.8 kg of DM and produced 28.1, 29.1 29.6 and 30.2 kg of energy corrected milk, respectively. Digestibility of DM and neutral detergent fibre (NDF) was determined using indigestible NDF (iNDF) as a marker. DM digestibility, feed intake and milk and protein yields increased with increasing wheat content while the milk fat concentration, the digestibility of NDF and the feed efficiency of the diets decreased.

Evaluation of the feed intake models in the Nordic feed evaluation system NorFor

Abstract The objective of this study was to evaluate the feed intake models in the Nordic feed evaluation system NorFor. Data from 196 feeding experiments with dairy cows, and 17 experiments of periodical data, and 135 experiments of complete data with growing cattle were used in the evaluation by mixed model regression. The feed intake by both dairy cows and growing cattle were overestimated by the models. A linear bias indicated that over prediction increased with level of intake both by dairy cows and growing cattle. Most animal and diet factors were significantly related to the residuals, which indicated that those factors did not act independently in the predictions of feed intake. This kind of errors can restrict future ration formulation and animal performance, since animal production parameters included in the prediction models will be a consequence of the diet fed at the time they were measured.

Prediction of nutritive values, morphology and agronomic characteristics in forage maize using two applications of NIRS spectrometry

ABSTRACT This study evaluates nutritive, morphological and agronomic characteristics of forage maize predicted by using a high-quality near-infrared (NIR) spectrometer and an NIR hyperspectral-imaging technique using partial least squares (PLS) regression models. The study includes 132 samples of dried milled whole-plant homogenates of forage maize with variation in maturity, representing two growing seasons, three locations in Sweden and three commercial maize hybrids. The samples were measured by a classical sample cup NIR spectrometer and by a pushbroom hyperspectral-imaging instrument. The spectra and a number of variables (crude protein, CP, neutral detergent fibre, starch, water soluble carbohydrates (WSC) and organic matter digestibility), morphological variables (leaves, stems & ears) and crop yield were used to make PLS calibration models. Using PLS modelling allowed the determination of how well maize variables can be predicted from NIR spectra and a comparison of the two types of instruments. Most examined variables could be determined equally well, by both instruments, but the pushbroom technique gave slightly better predictions and had higher analytical capacity. Predictions of CP, starch, WSC and the proportions of ears in the maize gave robust. The findings open new possibilities to further utilise the technology in plant breeding, crop management, modelling and forage evaluation.

Effects of morphological fractions on estimated milk yields in forage maize depending on growing site and plant maturity

Abstract This study was undertaken to determine the effects of the morphological fractions of forage maize for milk production as predicted by the spread sheet model called MILK 2006. The plants were harvested at increasing maturities at three different sites in Sweden and separated into stems, leaves, kernels and cobs. Chemical and in vitro analyses of the plant fractions as specified in the MILK 2006 model for predicting estimated milk yields Milk Mg−1 dry matter (DM) and Milk ha−1 were undertaken. Partial least squares regression analysis was used to evaluate the impact of the proportions and qualities of the fractions on Milk Mg−1 DM and Milk ha−1. Estimated milk yields could not be predicted based on the proportions of the fractions and their nutritional values. The most important parameters for determining Milk ha−1 was the DM yield, and for the estimated Milk Mg−1 were the concentrations of starch and the fibre digestibility of the whole crop.