Genetic variation in the feeding efficiency of maize genotypes evaluated from experiments with dairy cows

Abstract

Genetic vadation in the feeding efficiency of maize genotypes was evaluated from experiments with dairy cows. Maize genotypes were chosen to represent a range of digestibilities from previous experiments with standard sheep.The vadation in milk yield observed with dairy cows fed genotypes with low or high digestibilities or energy values was about 1.0-2.0 kg per animal per day. Moreover, the range of vadation in body weight was about 10-30 kg during the 3 months ofthe experiments. Hybrids with similar energy values had a similar effect on milk yield, but the intake of each hybdd could be very different when they were fed to dairy cows, even if no difference in intake had been observed in sheep. The higher silage maize intake of 'DK265' was mostly converted into a body weight gain rather than an increased milk yield, probably because the milk yield potential of the animals was soon reached. It appeared that those hybrids whose predicted energy value from sheep measurements was low led to relatively low performances in cows. Dairy cow performances also appeared to be related to the enzymatic solubility values of the whole plants.For maize breeders, the prediction of hybdd efficiency in dairy cow rearing must include digestibility and ingestibility factors. The most important challenge for maize breeders now will probably be the adjustment of a criterion for predicting intake because the stover digestibility and the starch content can be predicted reliably with the use of NIRS calibrations.Maize is nowadays a major forage crop for dairy cattle, and more than 3 300 000 ha are cropped in the European Union for silage-making. Silage maize is used as an energy source and its low protein content is easily corrected with soya or sunflower cattle cakes, as well as lucerne pellets. For a long time, breeders and farmers relied on the assumption that a good grain maize was also the most suitable for silage. But genetic variation in digestibiUty and energy value has been clearly demonstrated among experimental and registered hybrids. As reported by Deinum et al. (1984), Dijkstra and Becker (1960) probably performed one of the first in vivo digestion trials with standard sheep in digestibiUty crates. DigestibiUty of organic matter (DOM) of observed silages ranged from 59.2 to 72.7%. Andrieu and Demarquilly (1974), Gallais et al. (1976), Deinum et al. (1984 and Barriere et al. (1991) reported similar results, but with a narrower range of variation. However, the last two studies also reported values for brown midrib {bm2>) maize hybrids, the DOM of which neared around 4 points more than the best normal maize silages. Variation in DOM, digestibility of crude fibre (DCF) and UFL was investigated with standard sheep on a much broader genetic basis, by Barriere et al. (1992) (where UFL is the INRA fodder energy unit for milk production (Jarrige 1988) equivalent to 7.11 MJ/kg DM). Observed values ranged between 65.1 and 73.5% for DOM, 44.0 and 62.2% for DCF, and 0.79 and 0.94 for UFL, when investigating early and medium-early register...

Genetic variation of maize silage ingestibility in dairy cattle

“…The intake was increased by 0.5 and 1.0 kg respectively, compared to a "commonly used hybrid". The voluntary intake of hybrid DK265, which is of high cell wall digestibility, was also found greater than that of other hybrids, including hybrids of similar digestibility [7]. When maize silage was given as about 80% of the diet, dairy cows fed a DK265 silage had an average intake reaching 1.3 kg·day -1 more than that of a hybrid with the same dry matter and grain contents, and the same cell wall digestibility.…”

“…Recent unpublished data of Inra Lusignan showed that organic matter digestibility measured on wethers in digestibility crates ranged from 65.3 to 74.4% in a set of 232 registered early maize hybrids (mean value was 69.9%), and reached 76.8% in bm3 hybrids. Genetic variation in maize silage efficiency for milk or meat yield and quality was also proved in comparison (i) between normal hybrids [1,7,20], (ii) between normal and bm3 hybrids [4,5,17,26] and (iii) between normal and leafy hybrids [10,22,25] despite the fact that in these last experiments normal and leafy hybrids were not isogenic, and therefore the higher milk yield could not definitely be related to the leafy trait. Efficient methods are available for breeding maize of higher whole plant and cell wall digestibility.…”

“…Twelve hybrids were used in this 3 year experiment (1999,2000,2001), according to the distribution given in Table I, including (i) hybrid DK265, which is of high cell wall digestibility, and which appeared more ingested than control hybrids in previous experiments [7], (ii) 8 hybrids registered in France between 1996 and 2001 (namely Rh hybrids), (iii) a leafy hybrid (Rh390) available on the Northern American market, (iv) a bm3 hybrid and its isogenic counterpart (F7026bm3 is a bm3 isogenic of F7025), and (v) an experimental hybrid, resulting of a cross of a bm3 line (F7026bm3) with the Inra line F4, which is the normal flint line with the highest known cell wall digestibility (higher than that of F2bm3). One hybrid (Rh357) was discarded from the first year experiment, because of erratic results.…”

“…Very few works were then devoted to studies of genetic variation of ingestibility related to plant genotypes in fixed environmental conditions. From feeding experiments previously quoted [1,7], it appeared that the intake of maize hybrids of significantly lower whole plant or cell wall digestibility was lower than the intake of hybrids of rather good cell wall digestibility. But the results when comparing hybrids of higher digestibility were not so clear.…”

Genetic variation in rate and extent of the in situ cell wall degradation of maize stalks at silage harvest time

“…The hybrids NDF degradation kinetics were fitted to an exponential model, according to Orskov and McDonald [29], with a lag time (to) according to Danhoa [10], without any soluble fraction in NDF [30] Previous experiments in dairy cattle feeding [2,5] [15], had a p r index higher than Dk265.…”