Grain source and marginal changes in forage particle size modulate digestive processes and nutrient intake of dairy cows

Abstract

This study investigated the effects of, and interactions between, dietary grain source and marginal changes in alfalfa hay (AH) particle size (PS) on digestive processes of dairy cows. A total of eight Holstein dairy cows (175 days in milk) were allocated in a replicated 4 3 4 Latin square design with four 21-day periods. The experiment was a 2 3 2 factorial arrangement with two levels of theoretical PS of AH (fine 5 15 mm or long 5 30 mm) each combined with two different sources of cereal grains (barley grain alone or barley plus corn grain in a 50 : 50 ratio). Results showed that cows consuming diets supplemented with corn had greater dry matter and nutrient intakes (P , 0.01), independent of forage PS. In addition, the apparent digestibility of fiber fractions was greater for diets supplemented with corn (P 5 0.01). The feeding of barley grain-based diets was associated with greater apparent digestibility of non-fiber carbohydrates, and this variable was even greater when long AH was fed (P 5 0.04). Moreover, the feeding of long AH resulted in longer time spent eating (P 5 0.03) and higher pH (P , 0.01), as well as a tendency for higher acetate-to-propionate ratio in the rumen fluid (P 5 0.06) at 3 h post feeding. In conclusion, the results indicated that the marginal increase of PS of AH may prolong eating time and improve rumen fermentation, particularly in diets based on barley grain. Partial substitution of barley grain by corn can improve feed intake and fiber digestibility in mid-lactation dairy cows.Keywords: physically effective NDF, hay particle size, barley, corn ImplicationsThis study tested the hypothesis that grain fermentability and particle size (PS) of alfalfa hay have the potential to modify rumen conditions, digestion and performance of mid-lactation dairy cows. Indeed, the results showed an improved rumen environment and nutrient digestibility in cows fed a diet containing corn grain and long forage PS, respectively.

Effect of forage particle length on rumen fermentation, sorting and chewing activity of late-lactation and non-lactating dairy cows

“…To reduce particle length of forage, cows can either increase time spent eating and ruminating, increase rate of chewing or both (Yang and Beauchemin, 2006). In the present study, minutes per kg of DMI for eating, ruminating and TC are greater than those observed by Kononoff and Heinrichs (2003), Teimouri Yansari et al (2004) and Nasrollahi et al (2012). Greater minutes per kg of DMI of eating, ruminating and TC gives cows an opportunity to reduce particle length by increasing chewing rate as diet particle length increases, rather than needing to increase time spent ruminating.…”

“…Kononoff and Heinrichs (2003) and Teimouri Yansari et al (2004) using lactating cows observed a linear increase in eating time per day and minutes per kg of DMI and NDFI as (alfalfa haylage in the first study and alfalfa hay in the second) particle length increased. Nasrollahi et al (2012) also observed an increase of the same variables for greater alfalfa hay particle length, whereas Yang and Beauchemin (2006) observed no differences when barley silage particle length increased. In the current study, no differences in total ruminating or TC minutes per kg of DMI or NDFI were observed, whereas Teimouri Yansari et al (2004) observed a linear increase of the same Mean length of particles retained on the top screen of the ASABE particle size separator.…”

“…Yang and Beauchemin (2006) observed a linear increase in TC parameters as particle length decreased, but for ruminating parameters only time per day followed this tendency. Nasrollahi et al (2012) observed an increase in TC time for greater particle length and no differences in ruminating. However, comparisons of the current results to these experiments should take into consideration differences between experiments that affect chewing behavior: F : C (De Boever et al, 1990;Tafaj et al, 2005), cows' physiological stage (De Boever et al, 1990), level of feed intake (De Boever et al, 1990;Beauchemin, 1991), forage quality (Welch and Smith, 1970;Zebeli et al, 2012), feeding method (Maekawa et al, 2002) and rumen fermentability of the diet (Allen, 1997;Nasrollahi et al, 2012;Zebeli et al, 2012).…”

“…In spite of large differences in dietary forage particle length, no statistical differences were observed in DMI (Table 4). Failure to detect differences in DMI has been reported in cows averaging 189 6 38 DIM (Beauchemin et al, 2003); 153 6 7 DIM (Leonardi and Armentano, 2003); 189 6 39 DIM (Yang and Beauchemin, 2006); and 175 6 21 DIM (Nasrollahi et al, 2012). In contrast, other studies with cows averaging 19 6 4 DIM (Kononoff and Heinrichs, 2003) and 81 6 15 DIM (Teimouri Yansari et al, 2004) observed an increase in DMI when forage particle length was reduced (reported DIM were at the beginning of the experiments).…”

“…Teimouri Yansari et al (2004) used a stomach probe to measure pH 3 h after feeding and observed a lower pH for shorter length. Nasrollahi et al (2012) also used a stomach Sum of eating and ruminating time (Kononoff and Heinrichs, 2003).…”