Genetic variation in the feeding efficiency of maize genotypes evaluated from experiments with fattening bulls

Abstract

Summary — Genetic variation in the feeding efficiency of maize genotypes was evaluated from experiments with fattening bulls. Maize genotypes were chosen to represent a range of digestibilities from previous experiments with standard sheep. The variation in daily gains observed when bulls were fattened with hybrids of low digestibilities or high energy values was about 65 g per animal. When fed to bulls, the voluntary silage maize intake could be different in hybrids with similar energy values. Thus, differences in feeding efficiency of maize hybrids were related both to digestibility and ingestibility, especially for late hybrids among which variations for digestibility appeared lower than among earlier ones. As observed with brown-midrib (bm3) hybrids, genotypes with a greater digestibility and/or ingestibility might allow a reduced supply of energy-giving concentrates in the diet. Bull performances appeared to be related to both sheep digestibility estimates and the enzymatic solubility values of the whole plants, but this link could have been overestimated due to the similarity among hybrids in grain and dry-matter content of the silages. For maize breeders, the prediction of hybrid efficiency in cattle rearing must include both digestibility and ingestibility factors. Because the stover digestibility and the starch content can be predicted reliably with the use of NIRS (near infrared reflectance spectroscopy) calibration, the most important challenge for maize breeders in the future will probably be the development of a criterion for the intake prediction.

Genetic variation and breeding strategies for improved cell wall digestibility in annual forage crops. A review

“…When fed to cattle, intake of maize hybrids of significantly lower cell wall digestibility was lower than the intake of hybrids of rather good cell digestibility [35,36,53,95]. Although it has been reported in very few experiments, some hybrids have indeed a higher intake in dairy cows.…”

“…Breeding annual forage for cell wall digestibility 197 Based on European or Northern America experiments, the genetic variation in the NDFD value of maize silage was also proved to have consequences on young bull or dairy cow performances, even if maize was not the only constituent of the diet, [35,36,53,95,118,120]. All other factors being equal, when comparing hybrids with poor or good cell wall digestibility in dairy cows, fat corrected milk (FCM) yields differed from 1 to 3 kg among hybrids.…”

Effets du génotype de maïs ensilage sur les performances zootechniques de vaches laitières

“…En fait, une étude ultérieure de la variabilité génétique de la digestibilité et de la valeur énergétique des ensilages de maïs a montré que la gamme de variation de ces deux caractéristiques était nettement plus élevée si l'on s'intéressait à un plus grand nombre d'hybrides de maïs. Ainsi, pour les hybrides précoces et demi-précoces inscrits au catalogue officiel des variétés, le CUD de la matière organique varie de 65,1 à 73,8 %, et les valeurs énergétiques de 0,79 à 0,94 UFL (Barrière et al 1992a(Barrière et al , 1992b) ; ces résultats ont été confirmés par d'autres mesures faites plus récemment. Si cette variabilité génétique de la digestibilité et de la valeur énergétique est maintenant clairement établie à partir des mesures de référence sur moutons standards, il fallait en mesurer les conséquences en terme de production de lait (ou de viande, Barrière et al 1995a). L'objectif de ce travail était donc de comparer, avec des vaches laitières à haut potentiel, des ensilages de maïs réalisés à partir de variétés présentant des différences notables de digestibilité et de valeur énergétique selon les résultats obtenus avec des moutons standards.…”