Effect of protein on growth of Holstein heifer calves from 2 to 10 months

Dietary protein to metabolizable energy ratios on feed efficiency and structural growth of prepubertal Holstein heifers

Sixty Holstein heifers, 124.5 +/- 1.1 d of age and 124.9 +/- 2.5 kg of BW, were used to evaluate the influence of dietary crude protein to metabolizable energy ratio (CP:ME) on feed efficiency, structural growth, and body condition score. Treatment rations containing a specific CP:ME ratio were assigned to heifers in a complete randomized block design with treatment periods lasting 20 wk. The CP:ME ratios were 48.3, 59.1, 67.5, and 76.5 g of CP per Mcal of ME. The CP:ME ratios were altered by adjusting the concentration of CP (12.0,15.2, 17.4, and 19.7% CP) with similar amounts of ME (2.6 Mcal/kg DM) across all treatment rations. BW was recorded weekly on two consecutive days and used to adjust dry matter intake to allow approximately 0.80 kg/d gain. Average daily gain did not differ between the treatment rations, 0.74, 0.81, 0.81, 0.77 kg/d, low to highest CP:ME ratio, respectively. Dry matter intake showed a quadratic effect for the treatment rations, 3.30, 3.41, 3.48, and 3.39 kg/d, low to highest CP:ME ratio, respectively, and averaged 2.0% BW. Feed efficiency improved linearly with increasing CP:ME ratios, 4.76, 4.42, 4.35, and 4.33, respectively. The increased CP:ME ratios were accompanied by increasing levels of plasma urea N, 9.88, 13.34, 14.94, and 16.57 mg/dl, respectively. A trend toward linear increases in wither and hip height growth resulted with increasing CP:ME. Hip width growth was quadratic with increasing CP:ME ratios. Observed linear effects in feed efficiency and some structural growth measurements demonstrate positive results when feeding CP:ME ratios >48.3 to Holstein heifers between 125 and 234 kg of BW and gaining 0.80 kg/d.

Short Communication: Effect of Dietary Protein on Growth and Nitrogen Balance of Holstein Heifers

A growth study and a companion N balance study were conducted to evaluate the effect of dietary protein on growth and N utilization of postpubertal Holstein heifers. Forty heifers (398 +/- 9.4 kg) were fed one of four diets containing 8, 11, 13, or 15% crude protein (CP) for 121 d. Body measurements were taken at the beginning and end of the experimental period. Blood was collected via jugular vein every 28 d and evaluated for serum protein, albumin, and urea nitrogen. Curvilinear relationships were observed between dietary CP and gains in wither height and hip width, with maximal gains occurring at 13% CP. Feeding heifers higher amounts of dietary CP resulted in linear increases in heart girth gain, serum protein, albumin, and blood urea nitrogen. In the companion N balance study, feeding increasing amounts of dietary CP to heifers resulted in linear increases in N intake, fecal-N, urinary-N, and absorbed-N. There was a numerical trend towards maximal N retention in heifers fed diets containing 13% CP. Curvilinear relationships also were observed between dietary CP and dry matter, organic matter, and CP digestibility with maximal nutrient digestibilities occurring when heifers were fed diets containing 13% CP. Data suggest 13% dietary CP was optimal for postpubertal (400 kg) Holstein heifers.

The response of altering the ratio of dietary protein to energy on growth, feed efficiency, and mammary development in rapidly growing prepubertal heifers

This study was conducted to evaluate the effects of increasing the ratio of dietary protein to energy above National Research Council recommendations on average daily gain, feed efficiency, structural growth, and indirect measurements of mammary growth. Forty-five Holstein heifers were randomly assigned to either a low, medium, or high ratio of dietary crude protein (CP) to metabolizable energy of 46:1, 54:1, and 61:1 g/Mcal, respectively. The ratio of dietary protein to energy was altered by adjusting the concentration of CP with a similar amount of energy across all diets. Heifers were individually fed and began the treatment period at 200 kg of body weight and 28 wk of age. During the 3-wk adaptation period and 20-wk treatment period, all heifers were fed for a daily dry matter intake (DMI) of 2.45% of body weight. Body weight was monitored for two consecutive days each week and was used to adjust the dry matter offered on a weekly basis. The high versus low ratio of dietary protein to energy increased feed efficiency 6%, which resulted in larger heifers that were subsequently fed 3% more DMI over the course of the trial. The increased feed efficiency and DMI increased average daily gain by 9% for the high versus low ratio of dietary protein to energy. For the high versus low ratio of dietary protein to energy, hip width, hip height, wither height, and heart girth growth was increased 13, 16, 18, and 12%, respectively. The heifers fed the high ratio of dietary protein to energy had a lower rate of increased body condition score compared with the heifers fed the low ratio of dietary protein to energy. Teat length growth was used as an indirect measurement of mammary ductal development and was increased by 35 to 38% for heifers on the high versus low ratio of dietary protein to energy. Feeding dietary ratios of protein to energy above NRC recommendations improved feed efficiency and increased average daily gain, structural growth, and mammary development while decreasing body condition scores in heifers between 28 and 48 wk of age.

Evaluation of National Research Council and Cornell Net Carbohydrate and Protein Systems for predicting requirements of Holstein heifers

This experiment evaluated the effects of prepubertal energy intake and dietary protein source on average daily gain of Holstein heifers. Holstein heifers (n = 273) were assigned to one of three dietary energy treatments that were designed to achieve average daily gains of 0.6, 0.8, and 1.0 kg/d from 90 to 320 kg of body weight. Within each energy treatment, heifers were assigned to diets that were supplemented with animal and plant proteins or plant protein and urea. Diets were formulated using the Cornell Net Carbohydrate and Protein System. Actual mean daily gains by heifers on each energy treatment were 0.68, 0.83, and 0.94 kg/d and were not affected by protein source. Undegradable intake protein was predicted by the Cornell Net Carbohydrate and Protein System to be adequate to support the observed daily gain that was allowed by the amount of energy in the diet and was 13 to 25% lower than the recommendations for undegradable intake protein by the National Research Council. These results suggested that requirements for undegradable intake protein may be met at concentrations that are less than 35% of the dietary crude protein. Energy equations from the National Research Council and Cornell Net Carbohydrate and Protein System were evaluated and accounted for 87 and 86% of the variation in body weight gain that was allowed by the amount of energy in the diet with biases of -7.7 and -5.7%, respectively. The Cornell Net Carbohydrate and Protein System has the primary advantage of improved accuracy in the prediction of nutrient requirements in each unique production situation.

Influence of undergradability of protein in the diet on intake, daily gain, feed efficiency, and body composition of Holstein heifers

Thirty-two Holstein heifers with body weights (BW) between 213 and 231 kg were randomly assigned to one of four treatments for the 50-d trial. Treatments consisted of four percentages of rumen-undegradable protein (RUP) (31, 43, 50, and 55% of total N) at 100% of National Research Council recommendations for total digestible nutrients and crude protein. Total mixed diets composed of corn silage, ground barley straw, soybean meal, blood meal, urea, and minerals were formulated for a mean daily BW gain of 0.60 kg. Ration RUP percentage was varied by shifting protein sources. Mean dry matter intake (grams per kilogram of BW0.75) was 97.6, 84.4, 77.8, and 73.5 for 31% RUP (soybean meal), 43% RUP (blood and soybean meal), 50% RUP (blood meal with urea), and 55% RUP (blood meal) treatments, respectively. Daily gain was 0.84, 0.89, 0.91, and 0.96 kg/d, respectively. Intake of digestible energy (megacalories per kilogram of BW0.75 per day) was 0.28, 0.24, 0.22, and 0.21, respectively, and feed efficiency (megacalories of digestible energy per kilogram of BW gain) was 20.6, 16.1, 15.2, and 13.3, respectively. Dry matter intake (grams per kilogram of BW0.75), digestible energy intake, feed efficiency, daily BW gain, and hip height differed with respect to treatment. There were no differences in growth, wither height, or heart girth because of treatments. Changes in percentage of empty body fat as estimated by urea space procedures was 6.73, 4.67, 6.67, and 7.32, respectively, and did not differ with respect to treatments. These results indicate that increasing the RUP percentage in the diets of growing heifers improves feed efficiency and increases BW gain.

Effects of energy and protein allowances in the diets of prepubertal heifers on growth and milk production

Sixty-one Italian Friesian heifers between 100 and 300 kg of body weight (BW) were fed one of four diets. Heifers that were fed the diet with low energy and low protein received 90% of the amounts of total digestible nutrients (TDN) and crude protein (CP) recommended by the National Research Council for large breed dairy heifers growing at a rate of 0.7 kg/d. Ninety and 110% of recommended amounts of TDN and CP, respectively, were supplied to heifers fed the diet containing low energy and high protein. The diet with high energy and low protein provided 110 and 90% of recommended amounts of TDN and CP, respectively, and heifers fed high energy and high protein received 110% of the recommended amounts of both TDN and CP. When heifers reached 300 kg of BW, all were fed an identical diet. Heifers were bred at approximately 370 kg of BW. The increase of either TDN or CP improved average daily gain (608.1 g/d for heifers fed the low energy and low protein diet; 658.9 g/d for heifers fed the low energy and high protein diet; 794.4 g/d for heifers fed the high energy and low protein diet; and 847.6 g/d for heifers fed the high energy and high protein diet). Milk production through 36 wk of the first lactation was not influenced by the increased TDN or CP in the diet (22.7 kg/d for heifers fed low energy and low protein, 22.2 kg/d for heifers fed low energy and high protein diet, 20.2 kg/d for heifers fed the high energy and low protein diet, and 21.8 kg/d for heifers fed high energy and high protein diet). Results showed that Italian Friesian heifers can tolerate an average daily gain of approximately 800 g from 100 to 300 kg of BW without any detrimental effect on future milk production.

Nonstructural carbohydrate and undegradable protein sources in the diet: growth responses of dairy heifers

Thirty-five 3-mo-old 150-kg Holstein heifers were fed diets containing two nonstructural carbohydrate sources (corn or barley) with two quantities of undegradable protein (soybean meal or extruded soybean meal) for 9 wk in a 2 x 2 factorial arrangement to evaluate NRC guidelines that the diet contain increased quantities of undegraded intake protein. Total mixed diets fed for ad libitum intake contained approximately 17.4% CP, consisting of 16.7% corn silage (DM basis), 33.3% chopped alfalfa hay, and 50% concentrate mix. Average daily gains were greater for heifers fed extruded soybean meal, but response was greater when heifers were fed barley-extruded soybean meal (1.12, 1.13, 1.05, and 1.23 kg/d for corn-soybean meal, corn-extruded soybean meal, barley-soybean meal, and barley-extruded soybean meal, respectively) than diets of barley-soybean meal. Extruded soybean meal increased DMI (5.9, 6.1, 5.2, and 6.7 kg/d), but DMI were similar when diets based on corn or barley were fed. Diets with greater concentrations of undegraded intake protein fed to dairy heifers resulted in greater DMI and average daily gains, but responses were greater when heifers were fed diets based on barley rather than corn. These results suggest that current NRC recommendations for undegraded intake protein fed to 3- to 6-mo-old dairy heifers are too high; diets containing 35 to 40% undegraded intake protein should be sufficient.

Raising dairy replacements to meet the needs of the 21st century

Producing high quality replacement heifers at minimum cost will be one of the many challenges facing the dairy farm of the 21st century. Because replacement heifers represent a large portion of the total cost of milk production, dairy farmers will have to meet the replacement needs of their lactating herds at minimum cost to maintain the farm's profitability. To keep the US dairy industry competitive into the 21st century, researchers, extension, industry, and producers must examine the database of research in order to determine how to apply the known information to current production and research efforts. Important research is needed to improve the dairy heifers of the future. This review summarizes research of the past 12 yr related to dairy replacements and incorporates those findings into possible scenarios for future dairy calf and heifer management systems. Additional research is needed to determine how dairy replacement raising systems affect the lifetime productivity and profitability of the dairy cow.

Predicting body weight and wither height in Holstein heifers using body measurements

Relationships between body weight, wither height, and various other body traits, including heart girth, body length, and hip width, were studied using data from six experiments with 2625 observations. Body weight and wither height were regressed on the other body traits. Regressions of body weight including the linear, quadratic, and cubic effects of a single independent variable (heart girth, wither height, hip width or body length) indicated that each measurement would be useful in predicting body weight (R2 > .95); the regression of body weight on heart girth had the highest R2, followed by hip width. Similarly, regressions of wither height on heart girth, wither height, hip width, or body length, including linear, quadratic, and cubic effects, yielded R2 > .99. Regressions considering multiple traits as independent variables showed that the addition of a second body trait added little to the already high multiple correlations found with a single variable. In management situations for which body weight or wither height cannot be measured, various other traits can be used to estimate these body measurements accurately.

Effect of varying levels of neutral detergent fiber and total digestible nutrients on intake and growth of Holstein heifers

Intake, growth, DM intake, BW, and wither height were recorded from 108 Holstein heifers weighing between 100 and 400 kg. Heifers were divided into two blocks based on beginning BW (mean = 182 kg, light and mean = 270 kg, heavy). Heifers within blocks were assigned randomly to one of five treatments for the 35-d trial to examine effects of dietary NDF and TDN on growth. Light heifer treatments were 35, 45, or 50% of NDF at 100% of NRC TDN recommendation and 85 and 115% of NRC TDN at 45% NDF. Heavy heifer treatments were 40, 50, or 60% of NDF at 100% NRC TDN and 85 and 115% of TDN at 50% NDF. Total mixed rations formulated for .68 kg/d of BW gain were fed. Rations contained corn silage, alfalfa haylage, ground orchardgrass hay, soybean meal, high moisture corn, and a mineral mix. Mean DM intake (kilograms per day) and BW (kg) were 5.9, 217 and 7.28, 311, respectively, for the light and heavy blocks. Mean BW gain (kilograms per day) and growth in wither height (centimeters per day) were 1.07, .122 and .96, .076, respectively, for light and heavy blocks. Maximal DM intake per kilogram of BW.75 occurred at 41% NDF, below which NDF and ADF correlations with DM intake per kilogram BW.75 were -.16 and -.42. Above 41% NDF, correlations were -.28 and -.21. Ration NDF content had more influence than TDN on intake and growth of heifers with less than 200 kg BW. Above 200 kg BW, heifer performance more closely reflected the changes in ration energy content (TDN); NDF had less effect.

Increased weight gain and effects on growth parameters of Holstein heifer calves from 3 to 12 months of age

Two trials involving 280 Holstein heifer calves were to determine effects of increasing nutrient intake on growth (weight, height, and heart girth), dry matter intake, and water intake. In trial 1, 80 calves were fed from 60 to 172 d of age. More calf grower fed increased daily gain from .87 to .92 kg. Gain was further increased to .97 kg with higher energy content and to .99 kg with higher energy and higher protein content of calf growers. Alfalfa hay intake decreased as calf grower intake increased. Wither height and heart girth increased proportionally to body weight. Water intake was variable but proportional to dry matter intake. In trial 2, 114 heifers were fed alfalfa hay with either control or higher protein and higher energy heifer (accelerated program) growers from 187 to 369 d of age. Grass hay was fed to 86 heifers from 230 to 369 d of age with the same grower rations. Daily gain increased from .83 to .93 kg with the accelerated program. Hay intake decreased with higher grower intake on the accelerated program. When fed ad libitum on both programs, grass hay intake was about 5% lower than alfalfa hay. Heart girth at 369 d of age was increased on the accelerated program but there was no effect on wither height. Growth of Holstein heifers can be accelerated up to 1 kg daily gain from 3 to 12 mo of age without excessive fattening.