| Abstrakt: |
The objective of this study was to determine if ruminal fermentation characteristics differed in goat lines selected for high (HIGH) or low (LOW) juniper-consumption. Five Boer × Spanish-composite bucks (age = 2 yr; initial BW = 67.2 ± 4.3 kg) selected from each line were subjected to three different 25-d periods: 1) native range infested with juniper (Period 1); 2) group fed ad libitum sorghum × sudangrass hay (Period 2); 3) individually fed 3% BW of sorghum × sudangrass hay and ad libitum redberry juniper foliage offered fresh daily (Period 3). During each period, rumen fluid was evaluated for pH, VFA, ammonia N (NH3–N), and IVDMD of juniper foliage. There was a period effect (P< 0.02) for all response variables. A selection line × Period interaction was observed for total VFA (P< 0.01) because HIGH, which exceeded LOW during Periods 1 and 3 was lower in Period 2. However, total VFA did not differ within period between HIGH and LOW. During Period 1, when goats grazed juniper infested native rangelands, rumen fluid from HIGH contained greater (P< 0.05) ruminal isovalerate, and tended to have greater ruminal isobutyrate (P= 0.09) and NH3–N (P= 0.07) than LOW. When transitioned to a sorghum × sudangrass hay diet (Period 2), total ruminal VFA concentrations declined 26 and 4% for HIGH and LOW, respectively, and total VFA (P= 0.08) and valerate (P= 0.09) tended to be greater for LOW compared to HIGH. In vitro digestibility of juniper did not differ (P= 0.48), but declined 13 and 12% for HIGH and LOW, respectively, from Period 1 to 2. During Period 3, when transitioned to individual pens with ad libitum access to sorghum × sudan hay and juniper foliage, juniper intake did not differ (P= 0.16) with HIGH consuming 1.2 g/kg BW of juniper compared to 0.62 g/kg BW for LOW. Although no differences were detected (P> 0.05) for VFA, NH3–N, pH, and IVDMD between HIGH and LOW goats during Period 3, total VFA from HIGH increased 48% vs. 7% in LOW from period 2 to 3. Propionate increased 16% in HIGH compared to a 5% decrease in LOW from Period 2 to Period 3. Overall, results indicate that ruminal fermentation characteristics differ between divergent goat lines selected for high and low juniper consumption when consuming diets with and without juniper. |
