Solids-corrected Milk Production Research Articles

Evaluation of lower-starch diets for lactating Holstein dairy cows

The objective of this experiment was to measure ruminal and lactational responses of Holstein dairy cows fed diets containing 3 different starch levels: 17.7 (low; LS), 21.0 (medium; MS), or 24.6% (high; HS). Twelve multiparous cows (118±5 d in milk) were assigned randomly to dietary treatment sequence in a replicated 3×3 Latin square design with 3-wk periods. All diets were fed as total mixed rations and contained approximately 30.2% corn silage, 18.5% grass silage, and 5.0% chopped alfalfa hay. Dietary starch content was manipulated by increasing dry ground corn inclusion (% of dry matter) from 3.4 (LS) to 10.1 (MS) and 16.9 (HS) and decreasing inclusion of beet pulp and wheat middlings from 6.7 and 13.4 (LS) to 3.4 and 10.1 (MS) or 0 and 6.8 (HS). In vitro 6-h starch digestibility of the diet increased as nonforage sources of fiber replaced corn grain (% of dry matter; 73.6, HS; 77.3, MS; 82.5, LS) resulting in rumen-fermentable starch content by 14.6, 16.2, and 18.1% for the LS, MS, and HS diets, respectively. Diets had similar neutral detergent fiber from forage and particle size distributions. Dry matter intake, solids-corrected milk yield, and efficiency of solids-corrected milk production were unaffected by diet, averaging 26.5±0.8, 40.8±1.6, and 1.54±0.05kg/d, respectively. Reducing dietary starch did not affect chewing time (815±23min/d), mean ruminal pH over 24h (6.06±0.12), acetate-to-propionate ratio (2.4±0.3), or microbial N synthesized in the rumen (585±24g/d). Total tract organic matter digestibility was higher for HS compared with MS and LS diets (69.2, 67.3, and 67.0%, respectively), but crude protein, neutral detergent fiber, and starch digestibilities were unaffected. As dietary starch content decreased, in vitro ruminal starch fermentability increased and, consequently, the range between HS and LS in rumen-fermentable starch (3.5 percentage units) was less than the range in starch content (6.9 percentage units). Under these conditions, dietary starch content had no measurable effect on ruminal fermentation or short-term lactational performance of high-producing Holstein dairy cows.

Performance of lactating dairy cows fed corn as whole plant silage and grain produced from genetically modified corn containing event DAS-59122-7 compared to a nontransgenic, near-isogenic control

The nutritional equivalency of grain plus whole plant silage from genetically modified corn plants containing the DAS-59122–7 (59122) event expressing the Cry34Ab1 and Cry35Ab1 proteins to grain and silage from a near-isogenic corn hybrid without this trait (control) was assessed using lactating dairy cows. Corn plants with event 59122 are resistant to western corn rootworm and tolerant to the herbicide active ingredient glufosinate-ammonium. Effects on feed intake, milk production, and milk composition were determined. The 59122 grain and the control grain were produced in 2005 from isolated plots in Richland, Iowa. Whole plant corn silage for the 59122 and control treatments were grown in isolated plots at the Kansas State University Dairy Center and ensiled in Ag-Bags. Thirty lactating Holstein cows blocked by lactation number, day of lactation, and previous energy-corrected milk production were used in a switchback design. All cows were fed diets that contained 22.7% grain plus 21.3% whole plant silage from either the 59122 or the control hybrid, in addition to 21% wet corn gluten feed, 12.3% protein mix, 8.0% whole cottonseed, and 14.7% alfalfa hay. Each period of the switchback trial included 2 wk for diet adjustment followed by 4 wk for data and sample collection. Milk samples (a.m. and p.m.) collected from 2 consecutive milkings of each collection wk were analyzed for fat, protein, lactose, solids-not-fat, milk urea nitrogen, and somatic cell count. Percentages of milk fat, protein, lactose, and solids-not-fat were not affected by dietary treatment. Yields of milk, 4% fat-corrected milk, energy-corrected milk, solids-corrected milk, and the concentrations and yields of milk fat, milk protein, milk solids, and milk lactose were not significantly different between treatments. Efficiencies of milk, fat-corrected milk, energy-corrected milk, and solids-corrected milk production also were not different when cows were fed crops from 59122 than when they were fed the control hybrid. Milk production efficiency averaged 1.48 and 1.50kg/kg of dry matter intake for cows fed diets containing the control and 59122 corn, respectively. These data indicate that the nutritional value for milk production was not different between a diet containing grain plus whole plant corn silage produced from a 59122 corn hybrid versus a diet containing grain and corn silage from its near-isogenic control corn hybrid.

Effects of Increasing Milking Frequency During the Last 28 Days of Gestation on Milk Production, Dry Matter Intake, and Energy Balance in Dairy Cows

Forty-eight Holstein cows were used in a randomized block design to evaluate different dry period lengths and prepartum milking frequencies (MF) on subsequent milk production, milk composition, solids-corrected milk production, dry matter intake (DMI), and energy balance. Lactating cows, milked 2 times/d, began a 7-d covariate period 35 d prior to the expected calving date. Cows were milked 0 times/d (0×), 1 time/d (1×), and 4 times/d (4×) for the last 28 d of gestation. If milk production decreased to less than 0.5 kg/milking or 1 kg/d, milking via machine ceased; however, teat stimulation continued 1 or 4 times/d according to the treatment assignment. All cows were milked 2 times/d postpartum (wk 1 to 10). Prepartum DMI tended to be greater for 1×and 4×compared with 0×. Prepartum, cows milked 1×produced 17% less milk than cows milked 4×(5.9 and 7.1 kg/d, respectively). There were no differences in prepartum and postpartum body condition scores, body weights, and DMI. Postpartum milk production by cows following their third or greater gestation was greater for 0×and 4×compared with 1×. Postpartum milk production by cows following their second gestation was significantly decreased with increased MF (0×vs. 1×and 4×). Regardless of parity, postpartum solids-corrected milk was greater for 0×compared with 1×and 4×. Postpartum fat yield was greater for 0×vs. 4×, with 1×being intermediate. Postpartum protein yield was greater for 0×vs. 4×, whereas 0×tended to have greater protein yield than 1×. Postpartum energy balance was greater for 1×and 4×relative to 0×. Continuous milking (1×and 4×) resulted in a loss of milk production in the subsequent lactation for cows following their second gestation; however, for cows following their third or greater gestation, increasing the MF from 1×to 4×in the last 28 d of gestation alleviated the loss in milk production.

Effect of a Mixture of Feather and Blood Meals on Lactational Performance of Dairy Cows

An experiment was conducted over 18 wk of lactation to determine the effect of supplemental feather and blood meals (85:15, wt/wt, dry matter basis) fed at two dietary concentrations of crude protein (CP) on dry matter intake and milk protein production. Forty-eight Holstein cows were grouped by parity and assigned randomly at 3 wk postpartum to one of four diets following a 2-wk covariate period. Diets consisted of 50% alfalfa silage and 1) no feather or blood meals, 17.6% CP, and 5.1% ruminally undegradable protein (RUP); 2) 4% mixture of feather and blood meals, 17.6% CP, and 6.3% RUP; 3) no feather or blood meals, 19.6% CP, and 6.3% RUP; and 4) 4% mixture of feather and blood meals, 19.6% CP, and 6.9% RUP. According to the National Research Council, diet 1 was deficient in RUP, diets 2 and 3 were adequate in RUP, and diet 4 contained excessive CP and RUP. Intakes of dry matter and CP were depressed by 11% for cows fed the 19.6% CP diet supplemented with feather and blood meals. For cows fed the 17.6% CP diet, the supplementation of feather and blood meals increased RUP intake, but the supplementation of feather and blood meals to the 19.6% CP diet had no effect on RUP intake. Supplemental feather and blood meals increased the production of milk protein and 3.5% solids-corrected milk by cows fed the 17.6% CP diet. Diets 2, 3, and 4 resulted in similar efficiencies of solids-corrected milk production, but the efficiency of milk protein production specifically was increased by the supplementation of feather and blood meals to the 17.6% CP diet only. Results of this experiment indicate that a mixture of feather and blood meals improves the production of milk protein when supplemented to a diet that meets, but does not greatly exceed, the requirements established by the National Research Council for RUP and that contains alfalfa as the sole forage.

Complete Rations for Dairy Cattle. I. Methods of Preparation and Roughage-to-Concentrate Ratios of Blended Rations with Corn Silage

Treatment means for dry matter intake, milk production, fat-corrected milk, milk fat test and body weight gains did not differ significantly when rations containing comparable proportions of corn silage and concentrate mixture (30% roughage and 70% concentrate) were fed ad libitum as an ensiled complete ration, a complete ration blended at feeding time, or as separate components in a switchback-type experiment. Ensiling dry matter loss and pH averaged 2.9% and 3.85 for the ensiled cpmplete ration, and 5.0% and 3.75 for the urea-treated silage. Dry matter density of the ensiled complete ration was 81% greater than that of urea-treated silages.In the second experiment, widening roughage-to-concentrate ratios of complete rations from 40:60 to 30:70 to 20:80, was accompanied by stepwise increases in milk production and non-significant increases in dry matter intake under ad libitum feeding. Solids-corrected milk production was higher on the 20:80 than on the 40:60 roughage-to-concentrate ration. Milk fat tests were lower and body weight gains higher on the 20:80 and 30:70 roughage-to-concentrate rations than on the 40:60 ration. Solids-not-fat percentages were similar on all rations.

Methionine Hydroxy Analog for Lactating Dairy Cows1,2

Fourteen lactating Holstein cows were paired according to expected solids-corrected milk production and randomly assigned to Control or methionine hydroxy analog treatments. Hay, corn silage (treated with .5% urea) and pelleted concentrate (containing .5% urea), either with or without the analog (.357%), were fed. Treatment continued from 2 weeks prepartum to 24 weeks postpartum. During the sixth and tenth week postpartum six pairs of cows were subjected to digestibility and energy (indirect respiration calorimetry) and nitrogen balance trials.Cows supplemented with methionine hydroxy analog produced more milk fat (P<.05), particularly during Weeks 1 to 12, while feed consumption and yields of milk (actual) and solids-not-fat were not significantly affected. Methionine hydroxy analog increased digestibility of fiber and fat (P<.01) but not protein, increased urinary N loss (P<.01), reduced dietary N retention (P<.05), and increased methane energy loss (P<.01). Proportion of dietary gross energy and total N secreted in milk was not affected by treatment. Evidence is presented for higher maintenance energy requirement and higher efficiency of conversion of metabolizable energy to milk when methionine was included in the diet. The data are consistent with enhanced rumen microbial activity, but the specific mechanism by which methionine increases milk fat yield needs further clarification.

Influence of Sucrose on Rumen Fermentation Pattern and Milk Fat Content of Cows Fed a High-Grain Ration

Milk fat content was not increased by replacing milo with sucrose at levels representing 5,10, and 15% of the dry matter in rations containing 10% alfalfa hay and fed in excess of National Research Council requirements. The experiment involving 16 cows was conducted in randomized block design. It consisted of a standardization period of two weeks, a transition period of four weeks, and a comparison period of sixteen weeks. During the standardization period the cows received ad libitum a ration comprised of 40% alfalfa hay (estimated net energy basis) and 60% ground milo plus minerals.There were no significant differences among the covariant-adjusted treatment means for milk and solids-corrected milk production, milk fat, and solids-not-fat content, or production efficiency. In the rumen contents pH was lower (P<0.05) and lactate concentration was higher (P<0.10) with sucrose in the ration. The mean proportions of rumen volatile fatty acids were not significantly different among treatments.

COMPARISON OF CORN AND OAT BASED CONCENTRATES FOR LACTATING DAIRY COWS

Corn-based and oat-based concentrates were each fed with a restricted amount of hay of two qualities to lactating cows. The corn-based concentrate was consumed at a significantly higher rate (P &lt; 0.05), 14.6 vs 11.45 kg/day, and resulted in significantly (P &lt; 0.05) higher solids-corrected milk production, 24.68 vs 20.42 kg/day. Metabolizable energy required per meal of solids-corrected milk produced was significantly greater (P &lt; 0.05) for the corn-based concentrate, 2.48 vs 2.14. However, body weight loss was apparently greater when the oat-based concentrate was fed.

Guar Meal in Dairy Rations

The value of guar meal in rations for dairy animals was studied. In investigations with lactating dairy cows using a replicated 4×4 Latin square design, the average daily solids-corrected milk production was 14.6, 14.5, 14.4 and 14.9kg on concentrate rations containing 15% soybean, cottonseed, raw guar, or processed guar meals, respectively. Similarly, no significant differences were observed in flavor, fat, protein or total solids per cent in milk from cows on these diets. The apparent coefficients of digestion for protein were 81.3, 79.2, 80.0%, and the protein efficiency coefficients were 82.6, 87.7 and 88.4%, respeetively, with rations containing 15% cottonseed meal, raw guar meal and processed guar meal.No marked differences in the palatabilities of rations containing either raw or processed guar meal, or cottonseed meal were observed in group-fed or, after the second day, in stall-fed lactating dairy cows. In calf-starter mixtures flavored, processed guar and cottonseed meal gave slightly better rates of intake and gain than unflavored, processed guar for the first 30 days only.