Effect of Forage Amount and Particle Size in Diets of Lactating Dairy Cows on Site of Digestion and Microbial Protein Synthesis

Abstract

Roor, L. M., Wnerlnv, D. C. eNo S.lrrnn, L. D. 1985. Effect of forage amount and particle size in diets of lactating dairy cows on site of digestion and microbial protein synthesis. Can. J. Anim. Sci. 65: l0l-111.Lactating Holstein cows fitted with ruminal and duodenal T-type cannulae were used in two studies to determine the effect of forage: concentrate ratio and forage particle size on site of nutrient digestion and microbial protein synthesis. In exp.1, cows were fed alfalfa hay at 24, 38,58 and SOVo of total dry matter intake.Organic matter (OM) digestion in the total tract (OMD) increased with increasing concentrate level but apparent ruminal OM digestion (AROMD) was unaffected by diet. Digestion of acid detergent fiber (ADF) was similar among the higher forage diets, but was depressed at the 24Vo forage level. Efficiency of microbial Protein synthesis (MPS) was depressed by high concentrate diets and was positively correlated (P<0.05) to turnover rate within the rumen. ln exp. 2, cows were fed 20Vo concentrate and SOVo alfalfa hay in long, chopped or ground and pelleted form.AROMD was lower with ground hay but OMD was unaffected by diet. Digestibility of ADF in the rumen was lower with ground hay, but was partially compensated for by increased hindgut digestion of ADF. Flow of feed plus endogenous nitrogen (N) at the duodenum was 37Va and 47Vo on N intake with long and ground hay, respectively. Efficiency of MPS increased 75Va and postruminal N digestion increased 36Vo when ground hay replaced long hay. Efficiency of MPS was directly related to ruminal solids turnover rate and inversely related to liquid dilution rate.These results demonstrate improvements in efficiency of MPS with either increasing amounts of forage in the diet or increased ruminal passage of solids.

Effects of barley silage particle size and concentrate level on rumen kinetic parameters and fermentation patterns in steers

“…Similar results were obtained by using ground and pelleted alfalfa instead of long alfalfa hay or alfalfa silage in diets fed to dairy cows (Rode et al 1985;Woodford and Murphy 1988;Le Liboux and Peyraud 1998). The effect of reduced forage particle size on total tract digestibility can be explained by an increase in particulate passage rates.…”

“…receiving total mixed rations, the effects of reduced feed particle size on retention time have been variable. Some authors have linked the drop in digestibility of feeds with reduced particle size to acceleration in the passage of particles (Rode et al 1985; Le Liboux and Peyraud 1998); however, it is difficult to compare results from different experiments because the methods for determination of the particle size of the diets are not standardized. The effect of reducing particle size of the forage on fermentation patterns has been studied mainly using mixed diets with corn or wheat as the concentrate.…”

“…matter were observed (Rode et al 1985). Changes in the physical characteristics of feeds will also modify the fermentation pattern, resulting in changes to the molar proportion of propionic and acetic acid (Grant et al 1990).…”

Bovinos mestiços alimentados com diferentes proporções de volumoso:concentrado. 1. Digestibilidade aparente dos nutrientes, ganho de peso e conversão alimentar

“…Conclusão semelhante obteve RODE et al (1985), que utilizaram diferentes níveis de concentrado na dieta, observando que os CDAMS e CDAMO elevaram-se, à medida que aumentou o concentrado na dieta, provavelmente em virtude da redução de carboidratos estruturais e do aumento no teor de carboidratos não-estruturais na dieta. CARVALHO et al (1997) verificaram que houve efeito quadrático para as digestibilidades aparentes da MS, MO e dos carboidratos totais (CHT), estimando as digestibilidades máximas desses nutrientes aos níveis de 42, 40 e 43% de concentrado nas rações totais, respectivamente.…”

Reassessing the manipulation of protein synthesis by rumen microbes

“…Length of forage must also be considered. The feeding of chopped hay decreases the EMPS through a decrease in the turnover rate of particles (Rode et al, 1985;Rode and Satter, 1988).…”