We evaluated expression of 50 genes encoding enzymes involved in metabolism, cellular growth, and various transporters in ruminal epithelium tissue when calves were fed conventional milk replacer (MR) and starter (control) or enhanced MR and enhanced starter. Male Holstein calves were fed reconstituted control MR [20% crude protein (CP), 20% fat; 0.57 kg of solids/calf] plus conventional starter (19.6% CP, dry matter basis) or a high-protein MR (ENH; 28.5% CP, 15% fat; at ∼2% of body weight) plus high-CP starter (25.5% CP, dry matter basis). Groups of calves in control and ENH were harvested after 43 d (wk 5) and 71 d (wk 10) of feeding. Ruminal epithelium from 5 calves (3 to 42 d age) in each group was used for transcript profiling using quantitative reverse transcription PCR. No differences were observed for plasma β-hydroxybutyrate (BHBA) concentration but BHBA increased by wk 10 regardless of treatment. Reticulorumen mass postweaning was greater in calves consuming the ENH diet and corresponded with overall greater serum insulin. A marked upregulation of the ketogenic genes HMGCS2, HMGCL, and BDH1 was observed, concomitant with downregulation of expression of genes involved in fatty acid oxidation (CPT1A, ACADVL) at wk 10. Higher relative percentage mRNA abundance of HMGCS2 (∼40% of total genes assayed), the rate-controlling enzyme in hepatic ketogenesis, underscored its importance for ruminal cell energy metabolism. Higher PPARA expression and blood nonesterified fatty acids at wk 5 due to ENH were suggestive of more extensive long-chain fatty acid oxidation in ruminal epithelial cells during the milk-fed phase. In contrast, calves fed control consumed more starter during the milk-fed phase, which likely increased production of volatile fatty acids and accounted for higher expression of propionyl-CoA carboxylase (PCCA) and the Na(+)/H(+) exchanger 2 (SLC9A2) at wk 5. Expression of G-coupled protein receptors for short-chain fatty acids was undetectable. The expression of the urea transporter (SLC14A1) increased markedly with age and was correlated with the increase in blood urea N. Expression of genes involved in cell proliferation (INSR, FOXO1, AKT3) was greater for ENH primarily during the milk-fed period and corresponded with greater serum insulin. The greater reticuloruminal mass in calves fed ENH postweaning underscores the importance of feeding high-quality starter and indicates that fermentability of the diet, by providing metabolic fuel for ruminal epithelial cells, is a primary driver of ruminal development postweaning. From a mechanistic standpoint, the 7-fold increase in expression of the nuclear receptor PPARD (∼40-fold more abundant than PPARA) suggests a key role in controlling biological processes driving ruminal epithelial cell development. Elucidating ligands of PPARD may provide the means for nutritional regulation of rumen development.

Our objectives were to determine the effect of starter crude protein (CP) content on growth of Holstein calves from birth to 10 wk of age in an enhanced early nutrition program, and to compare the enhanced program to a conventional milk replacer program. Calves (64 female, 25 male) were assigned to 3 treatments in a randomized block design: 1) conventional milk replacer (20% CP, 20% fat) plus conventional starter [19.6% CP, dry matter (DM) basis], 2) enhanced milk replacer (28.5% CP, 15% fat) plus conventional starter, and 3) enhanced milk replacer plus high-CP starter (25.5% CP, DM basis). Calves began treatments (n=29, 31, and 29 for treatments 1 to 3) at 3 d of age. Conventional milk replacer (12.5% solids) was fed at 1.25% of birth body weight (BW) as DM daily in 2 feedings from wk 1 to 5 and at 0.625% of birth BW once daily during wk 6. Enhanced milk replacer (15% solids) was fed at 1.5% of BW as DM during wk 1 and 2% of BW as DM during wk 2 to 5, divided into 2 daily feedings. During wk 6, enhanced milk replacer was fed at 1% of BW as DM once daily. Calves were weaned at d 42. Starter was available for ad libitum intake starting on d 3. Starter intake was greater for calves fed conventional milk replacer. For calves fed enhanced milk replacer, starter intake tended to be greater for calves fed enhanced starter. During the weaning period, enhanced starter promoted greater starter DM intake than the conventional starter. Over the 10-wk study, the average daily gain of BW (0.64, 0.74, and 0.80 kg/d) was greater for calves fed enhanced milk replacer with either starter and, for calves fed enhanced milk replacer, tended to be greater for calves fed high-CP starter. Rates of change in withers height, body length, and heart girth were greater for calves fed enhanced milk replacer but did not differ between starter CP concentrations. The postweaning BW for enhanced milk replacer treatments was greater for calves receiving the enhanced starter at wk 8 (73.7, 81.3, and 85.8 kg) and wk 10 (88.0, 94.9, and 99.9 kg). Starter CP content did not affect height, length, or heart girth within enhanced milk replacer treatments. Regression analysis showed that gain of BW during the first week postweaning (wk 7) increased with greater 3-d mean starter intake in the week before weaning. Starter with 25.5% CP (DM basis) provided modest benefits in starter intake (particularly around weaning) and growth for dairy calves in an enhanced early nutrition program compared with a conventional starter (19.6% CP).

Fish oil is used as a ration additive to provide n-3 fatty acids to dairy cows. Fish do not synthesize n-3 fatty acids; they must consume microscopic algae or other algae-consuming fish. New technology allows for the production of algal biomass for use as a ration supplement for dairy cattle. Lipid encapsulation of the algal biomass protects n-3 fatty acids from biohydrogenation in the rumen and allows them to be available for absorption and utilization in the small intestine. Our objective was to examine the use of algal products as a source for n-3 fatty acids in milk. Four mid-lactation Holsteins were assigned to a 4×4 Latin square design. Their rations were supplemented with 1× or 0.5× rumen-protected (RP) algal biomass supplement, 1× RP algal oil supplement, or no supplement for 7 d. Supplements were lipid encapsulated (Balchem Corp., New Hampton, NY). The 1× supplements provided 29 g/d of docosahexaenoic acid (DHA), and 0.5× provided half of this amount. Treatments were analyzed by orthogonal contrasts. Supplementing dairy rations with rumen-protected algal products did not affect feed intake, milk yield, or milk component yield. Short- and medium-chain fatty acid yields in milk were not influenced by supplements. Both 0.5× and 1× RP algae supplements increased daily milk fat yield of DHA (0.5 and 0.6±0.10 g/d, respectively) compared with 1× RP oil (0.3±0.10 g/d), but all supplements resulted in milk fat yields greater than that of the control (0.1±0.10g/d). Yield of trans-18:1 fatty acids in milk fat was also increased by supplementation. Trans-11 18:1 yield (13, 20, 27, and 15±3.0 g/d for control, 0.5× RP algae, 1× RP algae, and 1× RP oil, respectively) was greater for supplements than for control. Concentration of DHA in the plasma lipid fraction on d 7 showed that the DHA concentration was greatest in plasma phospholipid. Rumen-protected algal biomass provided better DHA yield than algal oil. Feeding lipid-encapsulated algae supplements may increase n-3 content in milk fat without adversely affecting milk fat yield; however, preferential esterification of DHA into plasma phospholipid may limit its incorporation into milk fat.