Two surveys evaluated heifer management practices in dairy herds and custom grower operations. The NC-119 Heifer Management Survey conducted through the North Central Regional Research Project 119 included 226 Holstein and 67 Jersey herds from MN, MO, PA, VA, and WA. Mean rolling herd average for milk was 8,838 and 6,251 kg for Holstein and Jersey herds, respectively. Calf mortality rates from birth to first calving were 15.3 % for Holsteins and 15.8% for Jerseys. High producing herds had more aggressive, preventive health programs, hand-fed colostrum to newborn calves, and used prepartum groups and separate postpartum groups for first calf heifers. Practices associated with low calf mortality included using maternity pens in barns separate from the dairy herd as a calving facility and vaccination for brucellosis, an indicator of the level of overall management. Larger herds weaned calves earlier, placed more importance on heifer size as a criterion for first breeding, and used prepartum groups and separate postpartum groups for first calf heifers States differed in calving facility and calf housing choices. Calf mortality rates were similar among states. The Virginia Custom Dairy Heifer Rearing Survey included 24 growers. Average herd size was 194 head. Seven growers contracted with dairy producers, nine purchased, raised, and resold heifers, and eight did both. Survey results indicated a need for increased emphasis in several management areas. Only two contract growers had written contracts. Fifty-eight percent never monitored growth and 42% did not have forages tested or rations balanced. Fifty-seven percent used AI. / Master of Science

6 pp.

Revised; Originally Published: 2000 / 8 pp.

No description available.

No description available.

By tradition, the scramble heifer program has been portrayed as a strong animal project for which youth participate. These projects are yearlong; require a time commitment, monetary support, and dedication from the students. Animal science projects are well known for teaching life skills such as leadership, communication, working with groups, making decisions, and work ethic. Therefore, this study was developed to determine the life skills gained and the educational influence youth acquire as a result of raising a breeding heifer from the scramble program and the associated economic costs. The development of a participant questionnaire was used to address the above aforementioned purpose. The questionnaire was developed by Dr. Chris Boleman and the researcher, in conjunction with the Houston Livestock Show & Rodeo. The questionnaire was administered via (web) mailing techniques through the assistance of the Houston Livestock Show & Rodeo. The census included 400 calf scramble participants for the years 2005, 2006, and 2007. The survey consisted of 60 items and included scales on demographics, life skills obtained, management of project, and educational and/or career goals questions. Conclusions showed that the calf scramble program enhanced the youth?s life skills in many areas. Focusing on the development of accepting responsibility was the life skill that was most influenced. In addition to the life skills gained, the calf scramble had an impact on the educational goals of youth. 84% of respondents said that participating in the Houston Livestock Show & Rodeo Calf Scramble Program contributed to their educational goals. Contributions included increased motivation, focused goals; livestock knowledge gained, allowed them to start a college fund, and influenced their career choice. The associated economic cost concluded for maintaince of a project was an average of $5,443. Therefore the cost for the youth is known to be spread out across multiple areas. As a result of this study, the researcher recommends that youth should be encouraged to take part in the calf scramble program at the Houston Livestock Show & Rodeo. In addition, it should be promoted to youth to involve themselves in other leadership-developmental activities through other programs to further enhance their life skill development.

Apparent digestibility of forage soybean silage was evaluated utilizing a dual continuous flow apparatus in a Latin Square design. The fermenters were inoculated with a mixture of rumen fluid from two ruminally cannulated Angus cows. Fermenters were randomly assigned to one of the following treatments: 1) 76.1% alfalfa silage, 16.1% corn stover, 6.7% dry distiller’s grains (CON); 2) 75.1% soybean silage, 6.5% corn stover, 17.3 % soyhulls (SB); 3) 63.5% soybean pearl millet mixed silage, 15.2% corn stover, 20.2 % soyhulls (SBPM);4) 61.4 % rye grass, 14.8% corn stover, 4.8% dried distiller’s grains, 18.0 % soyhulls (RYE). All diets contained 1.1 % Purdue Heifer developer and were balanced to meet or exceed NRC requirements for a developing heifer and to contain 13.9% crude protein. Treatment had no effect (P ≥ 0.43) on the apparent ruminal digestibility of dry matter (DM), neutral detergent fiber (NDF), acid detergent fiber (ADF) or crude protein (CP). The SB forage source had the greatest (P = 0.03) fat digestibility compared to SBPM but similar to CON and RYE. Data suggests that the digestibility of forage soybean silage is similar to the digestibility of alfalfa silage. Additionally, if a producer is interested in planting a mixture of forage soybeans and pearl millet silage it too is similar in digestibility when compared to forage soybean alone and alfalfa silage.

A microcomputer simulation was developed as a tool for analyzing the dairy replacement enterprise. The simulation was constructed using a spreadsheet, and equations were developed using stepwise regression procedures. The simulation predicted BW, DMI, and fixed and variable costs for each week of a heifer's life from birth to calving. After calving, milk yield, feed costs, and fixed costs were predicted for first lactation. Variation was estimated for each predicted variable, thus enabling normal distribution of predicted values. The simulation was used to analyze profitability of various growth rate scenarios and marginal costs associated with changing feed costs, heat detection efficiency, death loss, and abortion rate. For the growth analysis, six scenarios were evaluated: 1) normal growth from 5 wk to calving, 2) Accelerated growth from 5 wk to calving, 3) slow growth from 5 wk to calving, 4) normal Growth from 5 wk to 14 mo and accelerated growth from 14 mo to calving, 5) accelerated growth from 5 wk to 14 mo and control growth from 14 mo to calving, and 6) slow growth from 5 wk to 14 mo and accelerated growth from 14 mo to calving. Average daily gain from birth to calving was 0.78, 0.90, 0.62, 0.78,0.75, and 0.80 kg/d, and age at calving was 25.1, 23.1, 27.4, 23.1, 23.0, and 23.1 mo,respectively. Total rearing cost from birth to calving was 1246, 1220, 1275, 1148, 1148, and 1138 $/heifer, and net profit through first lactation was 399, 407, 319, 441, 432, and 463 $/heifer, respectively. Results suggest modest growth rates from birth to calving (0.75 to 0.80 kg/d) with reduced first calving age <24 mo) is most desirable, and delayed calving (>24 mo) is costly and merits higher growth rates with earlier breeding. Increasing feed costs, death loss at birth through weaning, or abortion rate one percentage point increased rearing costs 7.33, 2.40, and 9.10 $/heifer. Improving heat detection efficiency one percentage point reduced rearing costs $2.80/heifer. For the heat detection analysis, the relationship between age at first calving and total rearing costs was -584.38 + 73.49 x calving age in mo (R-squared = 0.97), for ages at first calving from 24.4 to 26.6 mo. Results of this research agree with field observations that managers should strive for early calving (<24 mo) and modest growth rates (0.75 to 0.80 kg/d) to maximize profitability of the replacement enterprise. In addition, death loss, abortion rate, and heat detection efficiency are variables that a manager must control to minimize heifer rearing costs. / Ph. D.

This study was to evaluate effects of milk replacer (MR) composition on: mass and composition of mammary parenchyma (PAR) and fat pad (MFP), growth hormone (GH)/insulin-like growth factor-I (IGF-I) axis gene expression, and putative mammary epithelial stem cells. The hypothesis was that diet during the pre-weaning period alters the development, persistence, or activity of populations of putative mammary epithelial stem cells, possibly through involvement of GH/IGF-I axis molecules. Twenty-four newborn heifers were fed one of four MR diets: CON (20% CP, 21% fat MR fed at 441 g DM/d), HPLF (28% CP, 20% fat MR fed at 951 g DM/d), HPHF (27% CP, 28% fat MR fed at 951 g DM/d), and HPHF+ (27% CP, 28% fat MR fed at 1431 g DM/d). Animals were harvested on d 65 of life and mammary tissue was subjected to biochemical, molecular, and histological examination. By design, the effects of diet were evaluated at a common chronological age, but not necessarily at the same physiological age (body weight). Results from heifers reared on CON were compared to the average results from heifers reared on the other 3 diets. The second comparison evaluated the effect of increased fat in MR when protein content and intake were the same. The final comparison evaluated the effect of increased intake of a high-fat, high-protein MR. Neither diet composition nor nutrient intake in pre-weaned heifers affected PAR weight, PAR composition, GH/IGF-I axis gene expression, or putative mammary epithelial stem cell abundance when assessed at a common chronological age. Changes in MFP size and composition were observed, but no diet effect on GH/IGF-I axis gene expression in MFP was observed. This suggests nutrition is not critical for regulating the expression of local GH/IGF-I axis components or stem cell populations in the developing heifer mammary gland. / Ph. D.

Ovarian secretions and growth hormone (GH) are major endocrine regulators of mammary growth and development in bovine mammary gland; but information on endocrine regulation during early prepubertal period is limited. Our overall objective was to study the regulation of mammary growth and development as well as transcript abundance in early prepubertal bovine mammary gland by ovarian secretions and exogenous bovine somatotropin (bST). In the first study, we determined the effect of staged ovariectomy on mammary growth and development in two to four month old Holstein heifers. In the second study, effects of bST on mammary growth and development, and also on putative stem cell population were evaluated by beginning bST treatment in one month old Holstein heifers. Mammary growth and development was determined by mass of mammary tissue, biochemical analyses, histological examination, transcript abundance and protein expression in mammary parenchyma (PAR) and fat pad (MFP). Ovariectomy reduced mass and lipid content of PAR without affecting the histological characteristics or rate of epithelial cell proliferation. There was a marked reduction in progesterone receptor expression both at the mRNA and protein level. Ovariectomy also reduced transcript abundance in GH receptor (R), insulin-like growth factor (IGF)-1, IGF binding protein -6, estrogen responsive and proliferation marker genes, but increased the mRNA abundance of IGF-1R in PAR. On the other hand, administration of bST did not have an impact on PAR growth, epithelial proliferation, putative stem cell population or transcript abundance of IGF-axis genes. However, bST reduced the relative abundance of GHR, signal transducers and activators of transcription-5b and suppressors of cytokine signaling-2 in mammary PAR. Transcript abundance of IGF-axis molecules, estrogen responsive genes and proliferation markers in MFP was not affected by ovariectomy or bST. Overall, our data suggest that ovary is a predominant regulator of mammary growth and development in prepubertal heifers and that exogenous bST is not effective as a mammary specific mitogen in very young prepubertal heifers. / Ph. D.