Effects of rumen-protected methionine and guanidinoacetic acid supplementation in heat-challenged dairy cattle

Mauck, John D.

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https://hdl.handle.net/2142/127410 Copy

Description

Title

Effects of rumen-protected methionine and guanidinoacetic acid supplementation in heat-challenged dairy cattle

Author(s)

Mauck, John D.

Issue Date

2024-12-10

Director of Research (if dissertation) or Advisor (if thesis)

Loor, Juan J

Committee Member(s)

• Cardoso, Felipe C
• Nolan, Derek T

Department of Study

Animal Sciences

Discipline

Animal Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• heat stress
• methionine
• guanidinoacetic acid
• creatine
• arginine

Abstract

Heat stress presents a significant challenge for the dairy industry, accruing hundreds of millions of dollars in losses for producers every year. Elevated environmental temperatures manifest in serious health and production consequences for the individual cow, affecting milk quality/composition and quantity. Rumen-protected methionine and guanidinoacetic acid are two compounds that have shown promise in helping various livestock species attenuate the metabolically taxing response to heat stress. Ten multiparous Holstein cows (5 with ruminal cannulas) were split into two groups (one cannulated group and the other intact) and used in a replicated 5 × 5 Latin square. Each period of the Latin square lasted 23 days and was split into two parts: 16 days of thermoneutral feeding (thermoneutral period, TN) with the assigned diet followed by 7 days of heat stress challenge in combination with the assigned diet (heat stress period, HS). The five treatments were as follows: 1) no heat stress challenge and no dietary supplement (CON-TN), 2) 7 days of heat stress challenge with no dietary supplement (CON-HS), 3) 7 days of heat stress challenge with rumen-protected methionine supplementation (Mepron®; Evonik Industries AG, Essen, Germany) (RPM-HS), 4) 7 days of heat stress challenge with guanidinoacetic acid supplementation (GuanAMINO®; Evonik Industries AG, Essen, Germany) (GAA-HS), and 5) 7 days of heat stress challenge with both rumen-protected methionine (RPM) and guanidinoacetic acid (GAA) supplementation (MIX-HS). All 10 cows were assigned each treatment once. Heat stress was induced with electric heat blankets. Supplementation of RPM and GAA was conducted via top-dress with the TMR. Rumen-protected methionine was fed at a rate of 1 g/kg dry matter (DM) and GAA was fed at 25g per day. Cows were milked twice daily at approximately 0400h and 1530h and had ad libitum access to the total mixed ration (TMR) daily after the morning milking. Milk samples were taken every four days during TN and on days 2, 5, and 7 of HS. Blood samples were taken on the final day of TN and days 2, 5, and 7 of HS. Ruminal fluid was harvested from the cannulated cows on the last day of HS. Rectal and vaginal temperature and respiration rates were measured daily during HS. A MIXED model ANOVA with preplanned contrast P values was used for statistical analysis. The preplanned contrasts were as follows: CON-TN vs. CON-HS, CON-HS vs. MIX-HS, CON-HS vs. RPM-HS, and RPM-HS vs. GAA-HS. Heat stress was successfully induced in the cattle, with all heat-challenged groups having an upward change (P = 0.02) in rectal temperature (+0.33°C) during HS when compared with the thermoneutral control (CON-TN). CON-HS had a lower (P = 0.01) dry matter intake (DMI) than CON-TN during HS, but the other heat-challenged groups did not differ significantly from CON-HS. No significant differences in milk production between any of the experimental groups were observed during HS. When controlling for DMI, fat-corrected milk (FCM) production was the greatest in the CON-HS group during HS, differing substantially from CON-TN (P = 0.04, 1.66 vs. 1.37 FCM/DMI, respectively). Total energy-corrected milk and fat-corrected milk levels did not differ significantly between groups. Milk protein content was greater in the CON-TN and RPM-HS groups than the other three treatment groups during HS (P ≤ 0.05, +0.1-0.28%). Milk protein yield during HS was also greatest in CON-TN and RPM-HS, with CON-HS being lower than both groups (P = 0.03, -0.11 kg/d and P = 0.02, -0.12 kg/d, compared to CON-TN and RPM-HS, respectively). Milk casein content was lower in CON-HS and the two GAA groups (GAA-HS and MIX-HS) compared with the RPM-HS group during HS (P ≤ 0.06, -0.10-0.12%). CON-HS had a higher milk urea nitrogen (MUN) % during HS than all other groups (P ≤ 0.05, +2.4-1.3%). Plasma aspartate aminotransferase (AST) levels during HS were lowest in RPM-HS, notably so when compared with CON-TN, CON-HS, and GAA-HS (P ≤ 0.04, -11.9-7.9 U/L). Significant changes were detected by treatment and by day in plasma glutamate dehydrogenase (GLDH) levels during HS (P = 0.05), with GLDH levels trending downwards for all groups except CON-TN, in which GLDH levels rose. Relative proportions of iso-butyrate and iso-valerate in ruminal fluid were lower in CON-TN than CON-HS (P = 0.04, -0.15% for Iso-butyrate and -0.14% for Iso-valerate). In conclusion, RPM helped maintain milk protein levels in the RPM-HS group, but similar results were not seen in the other group fed RPM, MIX-HS. This experiment helped confirm the negative consequences for DMI and milk composition in heat-challenged cattle.

Graduation Semester

2024-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/127410

Copyright and License Information

Copyright 2024 John Mauck

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