North
Dakota State University Department of Animal and Range Sciences
Dairy Research
North
Dakota State University
Department
of Animal and Range Sciences
Dairy
Research
Current Projects
4. Coproduct and Emerging Crop Utilization
Recent development of hull-less "naked" oat varieties with unique nutrient composition could increase the use of these oats in the diets of high producing dairy cattle. There are but a few cultivars of hull-less oats currently on the world market. Of those, Paul (var.), a recent release by the North Dakota State University Experiment Station, is the predominant variety in our region. In addition, existing varieties of hull-less oats vary considerably in their composition, especially lipid (fat) content and protein level. Of these two nutrients of interest, little is known about the true digestibility of the protein.
4.1 Effect of Feeding Hull-less Oats with Varying Levels of Rumen-undegradable Protein on Performance of Early Lactation Holstein Cows
Hull-less oat (HO) is a relatively new crop with a unique nutrient composition of approximately 18% crude protein (CP) and 10% fat. The objective of this research was to examine the effects of HO, with two levels of rumen-undegradable protein (RUP), on lactation performance, milk composition, blood metabolites, and rumen parameters of early lactation cows. Twelve multiparous Holstein cows averaging 644 kg of body weight and 58 days in lactation were randomly assigned to one of four treatments in a triplicated 4 x 4 Latin square design. Treatments consisted of 1) corn-barley (CB) based, 2) CB with additional RUP, 3) HO based, and 4) HO with additional RUP. Treatments were formulated to contain 0.76 Mcal net energy for lactation (NEL) per lb of dry matter and to be nearly isonitrogenous within grain type. The supplemental RUP treatments contained an additional 6% RUP (percent of CP). Cows were housed individually in tie stalls and fed twice daily for 16 weeks. Dietary dry matter intake, milk yield, and milk composition was determined during the last week of each 4-week experimental period. Rumen and blood samples were also collected at this time. Milk yield, dry matter intake, ruminal pH, milk fat, milk protein, and milk lactose did not differ between treatments. HO inclusion increased milk urea nitrogen, serum triglycerides, and blood urea nitrogen (P < 0.01), irrespective of additional RUP. HO inclusion tended to decrease ruminal ammonia (P < 0.05) at 3 hours post-feeding. Treatment had no effect on serum insulin or non-esterified fatty acids. HO appears to be a suitable replacement for corn-barley grain in lactating cow diets.
4.2 Comparing Tempered and Dry-rolled Barley with and without the Inclusion of Yeast Culture Supplements in Total Mixed Diets of Early Lactating Dairy Cows
Objectives were to determine if barley tempered and amended with a combination
of both a live yeast culture and a fungal extract preparation 1) enhances the
utilization of barley and 2) alters the yield or composition of milk. Barley
use promotes more rapid fermentation and lower ruminal pH. Tempering improves
apparent dietary digestibility, while adding certain yeast cultures reduces
lactic acid production and(or) improves nutrient utilization of forages in ruminants.
Barley was tempered for 24 hours at 20% moisture and rolled before adding to
completely blended diets. Twenty-four primiparous and multiparous Holstein cows
averaging 575 kg body weight and 46 day in lactation were stratified by age,
days in milk, milk yield, and randomly assigned to one of four isonitrogenous,
isocaloric barley-based diets: 1) tempered rolled barley (TRB-W); and 2) dry-rolled
barley (DRB-W) with additives (a yeast culture and a source fibrolytic enzyme,
9 and 15 g/day per cow, respectively); 3) tempered rolled barley (TRB-O); and
4) dry rolled barley (DRB-O) without additives. Cows were fed the respective
diets in Calan gates for nine weeks. A univariate analysis was conducted for
a fixed model blocked for variation due to feeding period. Substituting tempered
for dry-rolled barley did not alter milk yield, dry matter intake (DMI), or
body condition. Cows fed TRB-O had greater (P < 0.01) concentrations of milk
protein, lactose, solids-non-fat, and casein than cows fed DRB-O. Additives
tended to diminish differences in milk components of cows fed tempered or dry-rolled
barley, but did not affect fat-corrected milk yield or body condition. Milk
urea nitrogen (MUN) levels were greatest (P < 0.01) for cows on the DRB-O
diet. Collectively, tempering and the addition of yeast and enzyme supplements
lowered ruminal ammonia (P < 0.001) and subsequent MUN (P < 0.001). Cows
fed TRB-W had the lowest DMI, but no differences existed among treatments for
corrected milk yield. Yeast and enzyme additives increased (P < 0.02) both
energy and protein efficiency, especially when used in combination with barley
that was tempered versus dry-rolled prior to feeding.