The effect of harvesting strategy of grass silage on digestion and nutrient supply in dairy cows

Abstract

This study examined the effects of primary growth (PG) and regrowth (RG) timothy-meadow fescue silages harvested at 2 stages of growth on feed intake, cell wall digestion and ruminal passage kinetics in lactating dairy cows. Four dairy cows equipped with rumen cannulas were used in a study designed as a 4 x 4 Latin square with 21-d periods. The experimental silages were offered ad libitum with 8 kg/d of concentrate. Ruminal digestion and passage kinetics were assessed by the rumen evacuation technique. Silages of PG were on average more digestible than RG silages. The concentration of neutral detergent fiber (NDF) and indigestible NDF (iNDF) increased and the concentration of digestible organic matter in dry matter (DM) of silages decreased with advancing maturity in PG and RG. Cows consumed more feed DM, energy, and protein and produced more milk when fed PG diets rather than RG diets. Delaying the harvest decreased DM intake and milk production in PG and RG. There were no differences between PG and RG in rumen pH, ammonia N, or total volatile fatty acid concentrations. The intake of N, omasal canal flow of total nonammonia N and microbial N, excretion of N in feces, and ruminal true digestibility of N were higher for PG than for RG diets. The efficiency of microbial N synthesis was not different between PG and RG. Intake and omasal canal flow of organic matter, NDF, and potentially digestible NDF (pdNDF) were higher in PG than in RG. Whole-diet digestibility of organic matter, NDF, or pdNDF in the rumen or in the total tract was not different between PG and RG despite the higher digestibility of PG silages measured in sheep. Rumen pool sizes of crude protein and iNDF were lower for PG diets, whereas the pool size of pdNDF was higher for PG diets than for RG diets. The rate of passage of iNDF was higher for PG diets than for RG diets, with no difference between them in rate of digestion or passage of pdNDF. The lower milk production in cows fed regrowth grass silages compared with primary growth silages could be attributed to the lower silage DM intake potential. Chemical composition of the silages, rumen fill, digestion and passage kinetics of NDF, or the ratio of protein to energy in absorbed nutrients could not explain the differences in DM intake between silages made from primary and regrowth grass.

Effects of partial replacement of corn and alfalfa silage with tall fescue hay on total-tract digestibility and lactation performance in dairy cows

“…Milk production followed a similar pattern and was decreased compared with the lower NDF diets. The week × treatment interaction for DMI in the present study was not observed, to our knowledge, in other studies feeding grasses; however, many of these are Latin square design (Fisher et al, 1993;Broderick et al, 2002;Rinne et al, 2002;Kuoppala et al, 2008Kuoppala et al, , 2010 or other trial designs of shorter periods (Hoffman et al, 1998;Cherney et al, 2004), which do not allow for a pronounced interaction over time. Strahan et al (1987;4 or 8 wk) and Verbeten (2012;98 d) conducted trials of longer duration and did not report an interaction over time.…”

“…However, the diets in the present study incorporating tall fescue grass are all higher in NDF than Verbeten (2012), suggesting that gut fill could potentially be limiting DMI (Allen, 1996) in the diets incorporating tall fescue. Similarly, 2 Finnish studies (Kuoppala et al 2008(Kuoppala et al , 2010) fed a combination of timothy and meadow fescue silages to lactating cows and observed that the silages with higher NDF limited DMI as well; however, these studies saw a corresponding decrease in milk production concomitant with the decreased DMI. Cherney et al (2004) evaluated the effects of feeding alfalfa silage Least squared means of DMI by week for cows consuming TMR with the forage portion composed (DM basis) of 33% alfalfa silage and 67% corn silage (control; 33AS67CS), 60% tall fescue hay and 40% alfalfa silage (60TF40AS), 60% tall fescue hay and 40% corn silage (60TF40CS), and 33% tall fescue hay and 67% corn silage (33TF67CS).…”

“…Cherney et al (1993) reported that DM digestibility of cool season grasses declined as maturity increased; however, that was in an in vitro setting. Rinne et al (2002) and Kuoppala et al (2008Kuoppala et al ( , 2010) evaluated apparent nutrient digestibilities by dairy cows of DM, OM, and NDF and found that as maturity of grass silage increased, digestibility of the respective nutrients decreased. Cherney et al (2004) compared cool season grasses as a replacement for alfalfa in lactating cows.…”

The effect of cutting time of grass silage in primary growth and regrowth and the interactions between silage quality and concentrate level on milk production of dairy cows

“…Although the general responses to concentrate supplementation on forage-based diets are well documented (Thomas, 1987;Huhtanen, 1998), the magnitude of responses with varying silage quality requires further study. A preliminary report of the present results has been presented by Kuoppala et al (2005).…”

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

“…In favor of NorFor's feed intake model, experimental data support that at higher Dvalue the animals still have capacity to increase rumen fill, but metabolic load exerts a regulatory effect on intake. Rinne et al (2002) and Kuoppala et al (2010) observed a decrease in intake and an increase in rumen pool size of NDF when the digestibility of grass silage decreased, supporting that the importance of physical fill in limiting feed intake increased as silage digestibility decreased. Further, a reduced rumen fill with improved silage quality indicated that rumen fill was not the only factor limiting intake, that is, metabolic load also influenced intake.…”