UVM Theses and Dissertations
Format:
Print
Author:
Nelson, Bron
Dept./Program:
Animal Sciences
Year:
2011
Degree:
MS
Abstract:
During the transition period cows become insulin resistant to spare glucose for fetal development and lactogenesis resulting in the mobilization of adipose tissue which suppresses dry matter intake (DMI). Dietary starch during early lactation may have an effect on insulin sensitivity as well as lactational performance. Multiparous Holstein cows (n = 78) were used to evaluate the effect of dietary starch content in corn silage-based diets fed in early lactation on performance and blood metabolites. Dietary treatments were 1) a low-starch diet (L; 21.0%) for the first 91 days in milk (DIM; LL), 2) a medium-starch diet (M; 23.2%) for first 21 DIM and a high-starch diet (H; 25.5%) for the next 70 DIM (MH), and 3) a high-starch diet (H; 25.5%) for the first 91 DIM (HH). Corn meal was replaced partially with soybean hulls and wheat middlings in the L and M diets. Dry matter intake and milk yield were measured daily. Milk composition was measured weekly starting at wk 2. Serum was collected every other day from 1 to 21 DIM and was analyzed for nonesterified fatty acids (NEFA) and [Greek Beta]-hydroxybutyric acid (BHBA).
A subset of 24 cows (n = 8 per treatment) received an intravenous glucose tolerance test (0.25 g glucose/kg of body weight) at 15 DIM. Data were analyzed as a completely randomized design by ANDVA with the MIXED procedure of SAS using treatment and time (when appropriate for repeated measurements) as fixed factors and cow within treatment as a random factor. Through the first 21 DIM (n =78 cows), there was no treatment effect (P> 0.10) for DMI (20.3 kg/d), milk yield (40.9 kg/d), milk fat (4.34%), milk protein (3.39%), or serum BHBA (8.8 mg/dL). Serum NEFA ([Mu]Eq/L) was higher (P = 0.02) for MH (578) than HH (437); LL was intermediate (452). There was no treatment effect (P> 0.10) on glucose tolerance test measurements: peak glucose concentration (218 mg/dL), nadir glucose concentration (46 mg/dL), glucose clearance rate over 60 min (3.46 %/min), time to reach half maximal glucose concentration (21.4 min), glucose area under the curve for 60 min (AUC₆₀) after glucose infusion (3018 mg/dL x 60 min), peak insulin (119 [MuI]U/mL), or insulin AUC₆₀ (2905 [Mu]IU/mL). Nonesterified fatty acid peak (1151 uEq/L) and nadir (212 [Mu]Eq/L) concentrations were not different (P> 0.10) among treatments.
Through the first 91 DIM (n = 72 cows) treatment affected milk yield with MH (49.9 kg/d) greater than HH (44.2 kg/d); LL was intermediate (47.9 kg/d). A trend (P [less than or equal] to 0.10) in milk fat percentage was observed with LL (3.88%) having a higher percentage than MH (3.64%); HH (3.79%) was intermediate. There was no difference in 3.5% fat-corrected milk (FCM; 50.5 kg/d) among treatments. Dry matter intake tended to be higher for LL (25.2 kg/d) than HH (23.7 kg/d); MH was intermediate (24.9 kg/d). There was no difference in FCM/DMI (2.03). There was a significant difference (P [less than or equal to] 0.05) in milk urea nitrogen (MUN) with LL (15.2 mg/dL) concentrations greater than MH (12.7 mg/dL) and HH (11.9 mg/dL). There was no difference in body weight (682 kg) or body condition (3.11). Dietary starch content did not affect insulin resistance assessed by a glucose tolerance test in early lactation cows. Diets containing 21 to 23% starch fed to cows in early lactation were found to improve DMI and milk yield for the first 91 DIM when corn meal was partially replaced with nonforage fiber sources as long as energy density of the diet was maintained.
A subset of 24 cows (n = 8 per treatment) received an intravenous glucose tolerance test (0.25 g glucose/kg of body weight) at 15 DIM. Data were analyzed as a completely randomized design by ANDVA with the MIXED procedure of SAS using treatment and time (when appropriate for repeated measurements) as fixed factors and cow within treatment as a random factor. Through the first 21 DIM (n =78 cows), there was no treatment effect (P> 0.10) for DMI (20.3 kg/d), milk yield (40.9 kg/d), milk fat (4.34%), milk protein (3.39%), or serum BHBA (8.8 mg/dL). Serum NEFA ([Mu]Eq/L) was higher (P = 0.02) for MH (578) than HH (437); LL was intermediate (452). There was no treatment effect (P> 0.10) on glucose tolerance test measurements: peak glucose concentration (218 mg/dL), nadir glucose concentration (46 mg/dL), glucose clearance rate over 60 min (3.46 %/min), time to reach half maximal glucose concentration (21.4 min), glucose area under the curve for 60 min (AUC₆₀) after glucose infusion (3018 mg/dL x 60 min), peak insulin (119 [MuI]U/mL), or insulin AUC₆₀ (2905 [Mu]IU/mL). Nonesterified fatty acid peak (1151 uEq/L) and nadir (212 [Mu]Eq/L) concentrations were not different (P> 0.10) among treatments.
Through the first 91 DIM (n = 72 cows) treatment affected milk yield with MH (49.9 kg/d) greater than HH (44.2 kg/d); LL was intermediate (47.9 kg/d). A trend (P [less than or equal] to 0.10) in milk fat percentage was observed with LL (3.88%) having a higher percentage than MH (3.64%); HH (3.79%) was intermediate. There was no difference in 3.5% fat-corrected milk (FCM; 50.5 kg/d) among treatments. Dry matter intake tended to be higher for LL (25.2 kg/d) than HH (23.7 kg/d); MH was intermediate (24.9 kg/d). There was no difference in FCM/DMI (2.03). There was a significant difference (P [less than or equal to] 0.05) in milk urea nitrogen (MUN) with LL (15.2 mg/dL) concentrations greater than MH (12.7 mg/dL) and HH (11.9 mg/dL). There was no difference in body weight (682 kg) or body condition (3.11). Dietary starch content did not affect insulin resistance assessed by a glucose tolerance test in early lactation cows. Diets containing 21 to 23% starch fed to cows in early lactation were found to improve DMI and milk yield for the first 91 DIM when corn meal was partially replaced with nonforage fiber sources as long as energy density of the diet was maintained.