Date of Award
Program or Major
Doctor of Philosophy
Within a dairy enterprise, one major cost is raising young heifers. Optimizing feeding programs of dairy heifers is imperative for the sustainability and profitability of dairy operations. Studies have shown that preweaned calves fed milk replacers (MR) with crude protein (CP) concentrations greater than the 20% typically found in conventional MR, have greater dry matter intakes (DMI) and average daily gains (ADG), but consume less starter which can lead to stress during weaning and reduced rumen development. The greater amount of CP being fed to preweaned calves may alter their nitrogen (N) balance and body composition. Deuterium oxide (D2O) dilution methods have been used for assessment of body composition because it is an alternative method to direct chemical analysis and considered a noninvasive technique that provides for economical and repeatable methods. Estimated body water content can be used to predict body fat and protein, and thus, the amount of energy reserves. The objectives of chapter II and chapter III were to determine N utilization, preweaning nutrient digestibility, and body composition in preweaned calves fed diets varying in the amount of CP and MR fed. This study used 24 newborn dairy heifer calves blocked by birth and randomly assigned to 1 of 3 treatments: (1) 446 g dry matter (DM) of a conventional MR (CON; 20% CP, 20% fat), (2) 669 g DM of a moderately high protein MR (MOD; 26% CP, 18% fat), or (3) 892 g DM of a moderately high protein MR (AGG; 26% CP, 18% fat). All calves had free choice access to starter and water. At wk 5 of age, urine was collected using urinary catheters for 3 d and chromium oxide was administered by bolus at 2 g/d for 7 d to estimate N efficiency and nutrient digestibility. When calves turned 50 d of age, a baseline blood sample was taken followed by injection of 300 mg of D2O/kg of body weight (BW) in sterile physiological saline (0.9%). After injection, the D2O was allowed to equilibrate with body water for 1 h. Six blood samples were taken over 6 d (1/d) at 1630 h to estimate the dilution of the tracer through nuclear magnetic resonance spectroscopy (NMR). There were no differences in total body water, protein, fat, or mineral content in calves fed CON, MOD, or AGG; however, results showed evidence that D2O dilution technique analyzed by NMR is appropriate and easy to estimate body composition in young calves.
Intake, growth, N utilization and nutrient digestibility phase of the experiment showed that calves fed MOD and AGG had similar starter intakes, feed efficiencies, and ADG; with the combined treatments having reduced starter intakes (258 g/d vs. 537 g/d), greater ADG (674 g/d vs. 422 g/d), and improved feed efficiency’s (0.57 vs. 0.45) compared with CON calves preweaning. However, DMI and water intake were similar across all treatments. Calves fed MOD and AGG treatments had similar but lower N efficiency than CON calves (45.5% vs. 52.7%). This could be due to MOD and AGG fed calves having greater urine volume; and thereby, greater combined urine N output compared with CON calves (17.6 g/d vs. 12.1 g/d). In summary, feeding a moderately high protein MR increased ADG and improved feed efficiency during the preweaning period, but reduced starter intake and lowered N efficiency.
Essential oils are secondary metabolites obtained from plants and appear to be natural alternatives to antibiotics. They are gaining interest in dairy nutrition because of their similar functions to ionophores. Supplemental antibiotic ionophores have been very successful in improving feed efficiency and rate of gain in calves, as well as decreasing disease incidences; however, calves may be developing resistance to ionophores and the use of antibiotics in animal feeds has been a major concern for consumers. No current research has looked into the value or palatability of supplementing essential oils to dairy heifers and their effects on intake and performance. The objective of chapter IV was to evaluate the taste preferences of 6 post-weaned dairy heifers (approximately 3-mo. old; 95 ± 10.8 kg BW) provided with 0 (control), 1, 2, 3, or 4 mg/kg BW of cinnamaldehyde daily using sequential elimination. Before the experiment started, the heifers were fed a different diet to decrease any potential bias. It consisted of 50% corn silage and 12.5% haylage. During the experiment, heifers were fed 57% corn silage and 22% haylage diet. Heifers had 2 d of adaptation to the new feeding regimen before the 14-d experiment started. They were offered the 5 experimental diets for 5 d and the most preferred diet was removed and the study continued with the 4 remaining diets. The most preferred diets were again eliminated sequentially, so that only 2 diets remained on d 13 and 14. Each diet was ranked based on the weight of feed refused at the end of each feeding segment. Overall ranking of the 5 treatments were control, 2, 1, 3, and 4 mg/kg BW of cinnamaldehyde. Results indicate that heifers preferred diets without cinnamaldehyde; however, when only cinnamaldehyde diets remained, DMI was not negatively impacted regardless of the concentration of cinnamaldehyde provided.
The objective of chapter V was to determine the effects of the essential oil, cinnamaldehyde, compared to the ionophore, monensin sodium on performance of weaned Holstein dairy heifers. Eighty-four approximately 13 wk-old Holstein dairy heifers (109 ± 7.55 kg BW) were housed in a naturally ventilated curtain side-wall barn in 12 pens with 7 heifers/pen. Heifers were randomly assigned to 1 of 4 treatments in a completely randomized design: (1) control (CON; carrier, 908 g of ground corn), (2) monensin sodium (MON; 1 mg/kg of BW + carrier), (3) cinnamaldehyde (CIN1; 1 mg/kg of BW + carrier), or (4) cinnamaldehyde (CIN2; 2 mg/kg of BW + carrier). The 2 preferred cinnamaldehyde doses from chapter IV were then chosen for this 70-d study. The treatments were hand mixed into a 20% CP whole shell corn and protein pellet mix fed daily at 2.21 kg/head/d. Heifers had access to free choice hay and water daily. There were no performance effects of cinnamaldehyde on growth, hay intake, hip heights (HH), or blood metabolites compared to heifers offered MON or CON. Average daily gains were 0.98, 0.99, 1.01, and 1.03 kg/d and average hay intakes per pen were 17.08, 16.34, 18.11, and 17.60 kg/d for CON, MON, CIN1, and CIN2, respectively. Fecal samples by pens indicated the presence of viable coccidia, but the number of counts were low and not consistent across heifers within each pen. Feeding monensin sodium to post-weaned dairy heifers did not affect any of the performance parameters measured when compared to the control. Under the conditions of this study, there were also no benefits of supplementing cinnamaldehyde into grain mixes for post-weaned heifers. Increasing the dose of cinnamaldehyde or changing the way it was administered to feed may have resulted in a different outcome. Future research regarding supplemental essential oils to dairy heifers should focus on different doses of essential oils and a new way to administer the treatment, which may affect feed efficiency and disease incidence in dairy heifers.
The cost of heifer rearing is expensive and supplementing with essential oils, such as cinnamaldehyde, and optimizing the amount of protein and amount of MR fed, may improve heifer health status and feed utilization. Thus, through increasing the rate of gain and improving nutrient utilization, dairy operations can decrease their overall costs of feeding and managing replacement heifers.
Chapman, Colleen, "Improving Nutrient Utilization and Growth in Dairy Heifers" (2016). Doctoral Dissertations. 1370.
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