Effects of protein content and rumen-undegradable to rumen-degradable protein ratio in finely ground calf starters on growth performance, ruminal and blood parameters, and urinary purine derivatives

This study investigated the effects of feeding finely ground starter diets containing either 18 or 22% crude protein (CP) content [dry matter (DM) basis] and high or low ratios of rumen-undegradable protein to rumen-degradable protein (RUP:RDP) on growth performance, nutrient digestibility, ruminal fermentation, blood metabolites, and urinary purine derivatives in dairy calves. A total of 48 three-day-old female Holstein dairy calves with 40.2 ± 2.5 kg of initial body weight (BW) were randomly assigned in a complete randomized block design to a 2 × 2 factorial arrangement of treatments (12 calves/treatment). Treatments were as follows: (1) finely ground starter diet (mean particle size = 0.69 mm) with 18% CP and low RUP:RDP ratio [low ratio (LR) = 26:74; 18CP-LR]; (2) finely ground starter diet with 18% CP and high RUP:RDP ratio [high ratio (HR) = 35:65; 18CP-HR]; (3) finely ground starter diet with 22% CP and low RUP:RDP ratio (22CP-LR); (4) finely ground starter diet with 22% CP and high RUP:RDP ratio (22CP-HR) on DM bases. Blocking was based on the day of treatment assignment, and treatments were randomly assigned within each block. Calves received 4 L of milk daily from d 3 to 10, 7 L/d from d 11 to 40, 4 L/d from d 41 to 49, and 2.5 L/d from d 50 to 53, and then all calves were weaned but remained in the experiment until d 83 of age. The results showed that overall average daily gain (ADG), weaning BW, and feed efficiency (FE) were greater in 22% CP treatments than in 18% CP. Increasing the starter CP content from 18 to 22% of DM did not influence overall starter feed intake, milk intake, total dry matter intake (DMI), postweaning ADG, and FE of calves. No effect of RUP:RDP ratio was observed for starter feed intake, milk intake, total DMI, preweaning ADG, FE, and grams of CP per megacalorie of metabolizable energy. The RUP intake and postweaning ADG were greater for calves fed the HR diets than for those fed the LR diets. The digestibility of neutral detergent fiber was greater, and the digestibility of OM tended to be greater, and the ruminal concentrations of total short-chain fatty acids (SCFA), acetate proportion, and acetate-to-propionate ratio were greater in 22% CP than in 18% CP. A 2-way interaction between starter protein content and time was observed for total ruminal SCFA, acetate proportion, and acetate-to-propionate ratio, indicating that starter CP concentration had more effect on ruminal parameters. Preweaning urinary purine derivatives, preweaning microbial protein synthesis, and postweaning urinary nitrogen were greater for calves fed the 22CP diets than for those fed the 18CP diets but were not affected by the different RUP:RDP ratios. The concentrations of blood glucose and insulin were greater in 22% CP than in 18% CP diets. The blood insulin concentration was greater when calves received the HR diets compared with the LR diets. Therefore, we conclude that greater starter protein content can have beneficial effects on growth performance, probably through increased microbial protein synthesized and preweaning blood insulin concentration; however, a greater RUP:RDP ratio showed marginal effects on growth performance during the postweaning period.

The crude protein requirement of the early-weaned calf given urea, meat meal or soya bean meal with and without sulphur supplementation

Two experiments were conducted with 84 male British Friesian calves to estimate their nitrogen and sulphur requirements between 5 and 11 weeks of age. A basal 12 % crude protein (CP) diet was supplemented with meat meal, soya bean meal or urea to 15 or 18 % CP, and with sulphur to reduce the nitrogen to sulphur ratios of the diets to about 10 to 1.

The weight gains and feed conversion ratios of the calves given the 12% CP diets were significantly poorer than those of the calves fed on the diets containing 15 or 18% CP, irrespective of the CP supplement used. The supplementation of the urea-containing diets with sulphur caused a significant increase in feed intake and weight gain.

The digestibility of nitrogen and dry matter increased with increasing CP content of the diets and was greater for the diets supplemented with urea than for those supplemented with meat meal or soya bean meal. Sulphur additions also increased the nitrogen digestibility. The retention of nitrogen, when corrected for feed intake, was greater in the calves fed on the diets containing 18% CP than in those fed on the 15% and 12% CP diets.

The supplementation of the diets with sulphur increased the digestibility of sulphur, its excretion in urine and its retention. The concentration of urea in the blood plasma increased with increasing dietary CP content, and was higher in calves given urea.

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.

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.

Evaluation of calf starters containing different amounts of crude protein for growth of Holstein calves

Holstein calves (n = 110) were used to evaluate the effect of calf starters containing 15, 16.8, 19.6, or 22.4% CP, DM basis (diets A, B, C, and D, respectively), on calf performance from d 4 to 56 of life. Preweaning daily gain tended to increase linearly as protein content of diets increased, averaging .37, .39, .38, and .44 kg/d for diets A, B, C, and D, respectively. After weaning, calves fed diet C gained the most (.86 versus .71, .75, and .79 kg/d for A, B, and D, respectively). Overall BW gains from d 4 to 56 averaged .54, .56, .62, and .61 kg/d for A, B, C, and D, respectively. Throughout the experiment, starter consumption tended to increase as CP content of diet increased. Under these conditions, maximum growth was supported by diet C (19.6% CP); no advantage was gained from higher (22.4%) protein content. Calf growth was moderate when calf starters of lower protein contents (15 or 16.8%) were fed.

Response of calves to diets that varied in amounts of ruminally degradable carbohydrate and protein

Holstein calves were used wk 1 to 12 after birth to evaluate three sources of nonstructural carbohydrates that differed in ruminal degradability (corn, barley, and dried whey) with two sources of CP (normal and extruded soybean meal) that also differed in ruminal degradability. Nonstructural carbohydrates were most degradable in the dried whey diets and least degradable in the corn diets, and protein was more degradable in soybean meal than in extruded soybean meal. Pelleted diets were formulated to be isonitrogenous at 18% CP and contained (DM basis) 20% ground alfalfa hay, the respective carbohydrate and protein sources, vitamins, minerals, and antibiotic premix. All calves received 4.5 kg/d of milk during wk 1 to 4 and 2.3 kg/d during wk 5. The BW gains during wk 1 to 12 were higher (.80, .70, and .70 kg/d) for calves fed corn than for those fed barley and dried whey, respectively, and were slightly higher for calves fed extruded versus normal soybean meal (.76 and .71 kg/d). Corresponding DMI (1.47, 1.34, and 1.31 kg/d) were higher for calves fed corn than for those fed barley and dried whey and were higher for calves fed extruded versus normal soybean meal (1.43 and 1.32 kg/d). Trends in BW gains and feed intakes for wk 1 to 5 and 6 to 12 were similar. Feed to gain ratio was similar for all diets in all periods. The BW gains of calves tended to be greater when they were fed diets containing nonstructural carbohydrates and protein that was less ruminally degradable.

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

Two trials involving 44 weaned Holstein heifer calves were to determine effects of protein on growth in weight and wither height, dry matter intake, and digestibility. In trial 1, 24 calves were fed according to requirements from 85 to 182 d of age, then at 80, 100, or 120% of recommended amounts for dietary protein content until 295 d. Weight at 295 d increased linearly with protein (280, 287, 298 kg), but wither height and dry matter intake were unaffected. In trial 2, 20 calves were fed 80, 100, or 120% of recommended protein from 71 to 182 d. Weight and wither height at 182 d responded quadratically to protein with highest values from the medium protein diet. From 183 to 295 d, trial 2 calves were rerandomized to diets of medium or high protein. Weight at 295 d was increased by high protein. An interaction between treatments for wither height indicated responses to high protein after 182 d for calves on low or medium protein before that time and a decrease for calves on high protein throughout. In male calves of similar age, elevated protein increased apparent protein digestibility but had inconsistent effects on digestibility of dry matter. Current protein recommendations appear adequate for calves to 6 mo of age but thereafter may be too generous.

Protein for calves on a limited milk-early weaning system

Complete pelleted calf starter rations were fed to Holstein heifer calves on a limited milk-early weaning program from 3 days to 12 wk of age. Five rations fed to each of 10 calves were to contain crude protein percentages of 10, 12.5, 12.5 with 97% urea, 15, and 15 with 1.1% urea (as fed). The digestible protein:digestible energy ratios (g digestible protein/Mcal digestible energy) of the rations (in same order) were 23.4, 30.7, 28.8, 36.4, and 41.5. Average birth weight was 42.9 kg and weaning weight at 4 wk, 52.8 kg. Treatment effects on feed intake, average daily gain, and feed efficiency were analyzed after adjustment of birth weight and removal of effects of block and location. Feed intake for 12 wk was greater for 15% crude protein with 1.1% urea than for either 12.5% ration but not different from 10% protein. Average daily gain was increased for 15% protein rations compared to 10 or 12.5% protein. Gain by claves fed 10% protein was equal to that by those fed 12.5% protein. Feed efficiency during wk 5 to 12 was improved for 15% with vegetable protein compared to 10% crude protein or the 12.5% crude protein ration with vegetable protein. There were no differences in intake, gain, or efficiency between urea and vegetable protein.

Amounts and sources of protein for dairy calves

Female Holstein calves (178) were fed rations varying from 10 to 17% crude protein (air dry) from 30 to 102 days of age. Ten percent was inadequate resulting in less body weight, gain, withers height, and heart girth than rations containing 12 to 17% crude protein. In trial 1 addition of urea, biuret, or ammonia-molasses to a 12% diet to make a 16% crude protein diet allowed gains and weights indistinguishable from those on a 12 or 16% crude protein soybean meal ration. In another trial, addition of urea, biuret, or ammonium propionate to a 10% ration to make a 14% ration allowed insignificantly greater gains and body weight. Gains and body weight were greater for the 14% soybean meal ration than the three non-protein-nitrogen rations for calves to 71 days of age but equal for 71 to 102 days. Gain, body weight, dry matter, and protein intakes at most dates and intervals were greater for calves fed the 14% soybean meal ration than the 10% ration. When 10, 12, 14, and 16% soybean meal rations were compared simultaneously, only the 10% crude protein ration gave inferior performance. Gains were reduced when average daily crude protein intake for the 72 day trail was 258 g or less. Calves fed lupine or dried poultry waste did not gain or consume as much as those fed comparable soybean meal rations. Calves fed a 17% crude protein ration from several protein sources plus alfalfa hay gained no much than those fed the 12 to 16% crude protein rations. Regression analysis relating dry matter and protein intake to body weight or gains indicated both dry matter intake and protein percentage were about equally important from day 41 to 72 and that after this age dry matter intake was of much greater importance than protein percentage. Protein intake expressed as g/day was not of importance in this regression. Weaning at day 42 allowed for greater body weight and gains than weaning at day 32. The difference in body weight was 2.5 kg at day 42 and 7 kg at day 102.

Methionine hydroxy analog supplementation of low protein calf rations

Thirty-six Holstein calves were randomly assigned at 3 days of age to one of three complete calf rations: ration A, B, C containing 0, .25, or .50% methionine hydroxy analog. All three rations were isonitrogenous at 13.5% crude protein (dry basis) and were offered adlibitum until calves were 12 wk of age. Calves were fed 3.64 kg whole milk oncedaily for 4 wk. Average daily gains (kg) and dry matter intakes (kg) from 4 to 12 wk were .88, 2.49; .77, 2.50; and .56, 1.98 for calves fed A, B, and C. Weight gains differed between all rations while intake was higher for A and B than for C. Dry matter intakes (kg per kg gain) from 4 to 12 wk were 2.85, 3.32, and 3.54. Serum amino acids for five calves on each treatment were similar for A and B. Calves fed C had lower serum values for all individual essential amino acids compared to A and B and 28% lower circulating total essential amino acids. Serum cysteine increased as dietary methionine hydroxy analog increased. Anamino acid imbalance or toxicity may have been produced which severely reduced gain, intake, and serum amino acids on ration C but only reduced gain on ration B.

DIGESTIBILITY, NITROGEN RETENTION AND CALORIC VALUE OF RAPESEED AND SOYBEAN MEALS WHEN FED AT TWO DIETARY LEVELS TO CALVES

Pre-pressed, solvent-extracted rapeseed and solvent-extracted soybean meals were fed with a basal diet to Holstein bull calves at levels to support maintenance or growth. Maintenance requirement was based on digestible energy (DE) = 145 W0.75 (kg). Growth rates of 0.55 and 0.75 kg per day were supported by intakes of 1.66 and 1.92 × maintenance for rape-basal and soy-basal diets. The digestibility of proximate components and energy were determined by the "difference" procedure. The derived crude protein digestion coefficients of rapeseed and soybean meals were 89 and 93%, resulting in digestible protein contents of 35 and 47%, respectively. The gross energy digestion coefficient was lower (P < 0.01) at the maintenance level of intake than at the level for growth, for both mixed rations (81, 89 for rapeseed meal and 78, 88 for soybean meal). The mean caloric values of rapeseed and soybean meals derived by difference were 3213 and 2926 kcal DE/kg dry matter, respectively. It was concluded that rapeseed meal is lower in digestible protein content but equal to or greater in DE value than soybean meal.

TRITICALE IN DIETS FOR YOUNG DAIRY CALVES

A study was conducted to compare feed intake and growth rate of young dairy calves receiving two levels of triticale (27.5 and 55% of a complete ration) with calves receiving barley diets supplemented with urea or soybean meal. Effect of pelleting the 55% triticale diet was also examined. Each experimental diet was fed to 10 dairy calves (five bulls and five heifers) from birth. Experimental diets were fed free choice throughout. Triticale (1967 crop) at both levels reduced weight gain and feed intake relative to the control diets; however, there was little effect on feed efficiency. Low levels of ergot contamination of the triticale may have played a role in feed intake depression. Pelleting the 55% triticale diet resulted in reduced feed intake, similar weight gain and increased feed efficiency. Rations containing urea resulted in reduced rumen levels of isobutyric acid.