Effect of a grain challenge on ruminal, urine, and fecal pH, apparent total-tract starch digestibility, and milk composition of Holstein and Jersey cows

Abstract

The effects of a grain challenge on ruminal, urine, and fecal pH, apparent total-tract starch digestibility, and milk composition were determined. Six Holstein cows, 6 rumen-cannulated Holstein cows, and 6 Jersey cows were used in a replicated 3 × 3 Latin square design balanced to measure carryover effects. Periods (10 d) were divided into 4 stages (S): S1, d 1 to 3, served as baseline with regular total mixed ration ad libitum; S2, d 4, served as restricted feeding, with cows offered 50% of the total mixed ration fed on S1 (dry matter basis); S3, d 5, a grain challenge was performed, in which cows were fed total mixed ration ad libitum and not fed (CON) or fed an addition of 10% (MG) or 20% (HG) pellet wheat-barley (1:1) top-dressed onto the total mixed ration, based on dry matter intake obtained in S1; S4, d 6 to 10, served as recovery stage with regular total mixed ration fed ad libitum. Overall, cows had a quadratic treatment effect for milk yield where CON (22.6 kg/d) and HG (23.5 kg/d) had lower milk yield than cows in MG (23.7 kg/d). Jersey cows had a quadratic treatment effect for dry matter intake where cows in CON (13.2 kg/d) and HG (12.4 kg/d) had lower dry matter intake than cows in MG (14 kg/d). Holstein cows had a linear treatment effect for dry matter intake (17.7, 18.4, and 18.6 kg/d for CON, MG, and HG, respectively). Rumen pH for the rumen-cannulated cows had a linear treatment effect (6.45, 6.35, and 6.24 for CON, MG, and HG, respectively). Cows in HG spent more time with rumen pH below 5.8 (4.33 h) than MG (2 h) or CON (2.17 h) as shown by the quadratic treatment effect. Holstein cows in HG (8.46) had lower urine pH than MG (8.51) or CON (8.54) as showed by the linear treatment effect for urine pH. Apparent total-tract starch digestibility had a tendency for a linear treatment effect on S3 (97.62 ± 1.5, 97.47 ± 1.5, and 91.84 ± 1.6%, for CON, MG, and HG, respectively). Fecal pH was associated with rumen pH depression as early as 15 h after feeding for Holstein cows. In conclusion, a grain challenge reduced urine pH in Holstein cows but not in Jersey cows. Holstein cows' health were not affected when rumen pH was depressed. A potentially useful link between rumen pH and systemic (urine) pH within 2 h after feeding was quantified in Holstein cows.

Grain challenge affects systemic and hepatic molecular biomarkers of inflammation, stress, and metabolic responses to a greater extent in Holstein than Jersey cows

“…The release of fatty acids into plasma is caused by the mobilization of adipose TAG stores through the process of lipolysis, and the small 0.03 mmol/L difference in Holsteins induced to develop SARA could have been related to the small differences in DMI compared with controls (Luan et al, 2016). The lack of change in plasma BHB and glucose or TAG in liver of Holsteins and Jerseys indicated no marked effects of the acute grain challenge.…”

“…The experimental protocol was approved by the Institutional Animal Care and Use Committee at the University of Illinois at Urbana-Champaign. The experimental design and the feeding management of cows were previously described in detail (Luan et al, 2016). Briefly, cows for the present study were 6 Holstein (2.67 parity; BW 717 ± 30 kg and 258 ± 16 DIM) and 6 Jersey (2.50 parity; 471 ± 30 and 190 ± 86 kg) fed a basal diet or the basal diet plus the highest level of grain in the study of Luan et al (2016).…”

“…The experimental design and the feeding management of cows were previously described in detail (Luan et al, 2016). Briefly, cows for the present study were 6 Holstein (2.67 parity; BW 717 ± 30 kg and 258 ± 16 DIM) and 6 Jersey (2.50 parity; 471 ± 30 and 190 ± 86 kg) fed a basal diet or the basal diet plus the highest level of grain in the study of Luan et al (2016). Periods (10 d) were divided into 4 stages (S): S1, d 1 to 3, served as the baseline with TMR ad libitum; S2, d 4, served as restricted feeding, with cows offered 50% of the average daily intake observed in S1; S3, d 5, a grain challenge was performed, in which cows were fed a TMR ad libitum without (control) or with an additional 20% pellet wheat-barley (1:1; HIG) top-dressed onto the TMR; S4, d 6 to 10, served as recovery during which cows were allowed ad libitum access to the TMR.…”

“…The focus on the mTOR pathway in the liver is of importance because of its role in the regulation of protein synthesis (Laplante and Sabatini, 2013;, and the fact that inflammation is well known to shift the utilization of AA for the synthesis of positive APP. Therefore, the aim of this study was to use liver tissue from cows in the control group or cows receiving a grain challenge of 3.2 kg of wheat-barley (1:1) in the study of Luan et al (2016) to perform analyses of systemic and molecular biomarkers of metabolism, inflammation, and oxidative stress responses.…”

Combinations of non-invasive indicators to detect dairy cows submitted to high-starch-diet challenge

“…In comparison with other standard methods, it can be faster and cheaper. The pH measurements in faeces and urine are heterogeneously affected during SARA challenge (Luan et al, 2016), but such measures can improve detection of animals affected by HSD challenge on-farm when combined with other indicators.…”