The effect of an exogenous amylase on performance and total tract digestibility in lactating dairy cows
| Author(s) | McCarthy, Maris M. | |
| Date Accessioned | 2012-11-07T22:52:12Z | |
| Date Available | 2012-11-07T22:52:12Z | |
| Publication Date | 2011 | |
| Abstract | This thesis consisted of 2 experiments. The objective of Experiment 1 was to determine performance and digestibility response of lactating dairy cows to a reduced starch diet containing a commercial amylase product. The objective of Experiment 2 was to determine the effect of various levels of amylase on in vitro starch digestibility of 3 substrates. In Experiment 1, 19 multiparous (86 ± 46 DIM) and 5 primiparous (93 ± 8 DIM), were blocked by parity and DIM and assigned to treatments in a 3 × 3 Latin square design, with 28 d periods. Treatments were a normal starch TMR (NS), a reduced starch TMR (RS), and a reduced starch TMR with (351 KNU/ kg TMR DM) exogenous amylase added to the concentrate (RSE). The hypothesis was that reducing ration starch content would decrease milk production and diet digestibility compared to NS due to a decrease in available energy, and that RSE would alleviate some of this decrease by increasing nutrient digestibility. Rations were 41% concentrate and the NS TMR contained 12.8% corn grain, 2.9% soyhulls, and 2.9% citrus pulp. The RS and RSE TMR contained 6.0% corn grain, 6.9% soyhulls, and 6.9% citrus pulp. Starch concentrations in NS, RS, and RSE TMR were 27.5, 23.2, and 22.4%, respectively. Data were analyzed using a mixed model containing the fixed effects of treatment, week, period, and their interactions, and the random effects of cow and block. Feeding a RS diet compared with a NS diet resulted in decreased milk, FCM, milk protein yield, milk lactose yield, and increased MUN and NDF digestibility. Feeding the RSE diet resulted in increased milk protein percentage and increased DM, NDF, and CP digestibility. Exogenous amylase decreased milk lactose yield and tended to decrease milk yield and 3.5% FCM yield. In Experiment 2, NS and RS grain samples and corn starch were pre-incubated (18 h prior to start of in vitro) or co-incubated (during in vitro) with 4 levels of liquid amylase (0, 382, 1274, 3833 KNU/ kg substrate DM) and 7 h in vitro starch digestibility was measured. Data were analyzed using a mixed model including the fixed effects of substrate, amylase, preincubation, day, and all multi-way interactions. Pre-incubation of amylase with substrate for 18 h prior to in vitro resulted in increased starch digestibility compared to co-incubated samples. The starch digestibility for co-incubated samples was greatest at amylase application of 383 and 1274 KNU/kg substrate DM. While the addition of exogenous amylase increased in vitro starch digestibility as well as increased the digestibility of some nutrients during the lactation trial, this did not result in improved animal production performance. | en_US |
| Advisor | Gressley, Tanya | |
| Degree | M.S. | |
| Department | University of Delaware, Department of Animal Science | |
| URL | http://udspace.udel.edu/handle/19716/11704 | |
| Publisher | University of Delaware | en_US |
| Keywords | Digestibility | en_US |
| dc.subject.lcsh | Dairy cattle -- Feeding and feeds. | |
| dc.subject.lcsh | Digestion. | |
| dc.subject.lcsh | Amylases. | |
| dc.subject.lcsh | Starch. | |
| Title | The effect of an exogenous amylase on performance and total tract digestibility in lactating dairy cows | en_US |
| Type | Thesis | en_US |