There are concerns with feeding young dairy calves amounts of milk solids approaching 0.9kg of dry matter (DM) or more because of slumps in average daily gain (ADG) at weaning and low starter intakes. Additionally, programs feeding more than 0.6kg of DM have not been thoroughly tested for success at different weaning ages. Four milk replacer (MR) programs were compared in trial 1. Program A was 0.44kg of DM of a 21% crude protein (CP), 21% fat MR powder fed daily for 42 d. Program B was 0.66kg of DM of a 27% CP, 17% fat MR powder fed daily for 42 d. Program C was 0.66kg of DM of a 27% CP, 17% fat MR powder daily fed for 28 d. Program D was up to 1.09kg of DM of a 29% CP, 21% fat MR daily fed for 49 d. Digestibility estimates were made and blood was sampled for serum constituents on d 53 to 56, and performance was measured for 84 d. Three programs feeding a 27% CP, 17% fat MR powder were compared in trial 2 over 56 d. Calves on program A were fed 0.66kg of DM powder daily and weaned at 28 d. Calves on program B were fed 0.66kg of DM powder daily and weaned at 42 d. Calves on program C were fed up to 1.09kg of DM powder daily and weaned at 42 d. Digestibility estimates were made and blood was sampled for serum constituents d 21 to 24, d 36 to 39, and d 53 to 56. In trial 1, calves fed program A had the least overall ADG. Calves fed program D had the greatest ADG from 0 to 56 d, the least ADG from d 56 to 84, the least digestibility estimates, and the least concentrations of serum amylase. At 84 d, there were no differences in body weights of calves fed programs B, C, and D. In trial 2, calves fed program A had the greatest starter intake and greatest concentrations of serum amylase. Calves fed program C had the least estimates of digestibility from d 53 to 56 and the least serum concentrations of amylase. Calves fed up to 1.09 kg/d of 27 to 29% MR powders and weaned at 42 or 49 d had lower starter intakes, concentrations of serum amylase, and digestion of starter postweaning compared with calves fed conventional 21% CP, 21% fat MR powders fed at 0.44 kg/d. Calves fed 0.66 kg/d of a 27% CP, 17% fat MR powder and weaned at 28 or 42 d of age had no reductions in intake or digestion compared with calves fed conventional MR and gained as much total body weight from 0 to 84 d as calves stepped up to 1.09kg of MR.

Four trials were conducted to compare the concentrations of cottonseed hulls (CSH) and chopped hay in textured starters on calf body weight gain, intake, and efficiency. Holstein bull calves (initially 3 and 4 d old in studies 1, 2, and 3, and 59 to 60 d old in study 4) were fed ad libitum starters (geometric mean particle size of approximately 2,000 22mim; equal at 18% crude protein as-fed; digestible energy concentration declined with increasing roughage). All calves were weaned at 31 to 32 d of age. Calves were housed in individual pens bedded with straw within an unheated, curtain-sided nursery for d 0 to 56 and then grouped in pens of 6 calves for d 56 to 84. Study 1 compared textured starters containing A) 0% or B) 5% CSH for the first 56 d. On d 56 (through d 84), calves fed diet A were switched to diet C, which contained 0% CSH and 5% chopped hay; calves fed diet B were switched to diet D, which contained 5% CSH and 5% hay. Study 2 compared textured starters fed from 0 to 84 d that contained A) 0% CSH and 0% chopped hay, B) 5% CSH, C) 10% CSH, or D) 5% chopped hay. Study 3 compared textured starters fed from 0 to 56 d that contained A) 0%, B) 2.5%, and C) 5% chopped hay. Study 4 compared textured starters fed from d 56 to 84 that contained A) 5% and B) 15% chopped hay. In study 1, calves fed the diet with 5% CSH consumed less starter and were less efficient from 28 to 56 d than calves fed 0% CSH. Calves fed the diet with 0% CSH tended to have a greater average daily gain (ADG) and empty body weight ADG (EBWADG) from 28 to 84 d than calves fed the starter with 5% CSH. In study 2, EBWADG declined linearly from 0 to 28 d, and both ADG and EBWADG decreased from 28 to 56 d as CSH percentage increased in the starter. Both ADG and EBWADG responded quadratically to CSH percentage in the starter from 56 to 84 d, with calves fed the starter containing 10% CSH having the slowest ADG and EBWADG. Calves between 56 and 84 d that were fed starters with 5% roughage appeared more efficient than calves fed starters with 0 or 10% roughage. In study 3, ADG, EBWADG, starter intake, and efficiency declined linearly as hay percentage increased in the starter from 28 to 56 d. In study 4, ADG, EBWADG, and starter intake were less for calves fed starters with 15 vs. 5% hay. In conclusion, adding low-energy fibrous feeds to starters with adequate coarseness (approximately 2,000 microm) reduced ADG in weaned calves less than 3 mo old bedded on straw.

Four multiparous Holstein cows fitted with rumen and duodenal cannulas were used in a 4 x 4 Latin square with 20-d periods. Four diets were formulated for high and low rumen availabilities of nonstructural carbohydrate and protein. Cows were milked and fed three times daily. Milk production averaged 39 kg/d and was unaffected by treatment. Dry matter intake and 4% FCM production were increased by 1 kg/d for cows fed the low rumen-available nonstructural carbohydrate diets. Milk protein percentage was elevated when either the high rumen-available nonstructural carbohydrate or high rumen-available protein diets were fed. Low rumen-available protein diets increased duodenal passage of total essential AA but did not increase passage of Arg, Ile, and Met. Passage of bacterial N was highest (262 g/d) when high rumen-available nonstructural carbohydrate was combined with high rumen-available protein and was lowest when high rumen-available nonstructural carbohydrate was combined with low rumen-available protein (214 g/d). Diets with low rumen availabilities of protein were not advantageous, possibly because duodenal passage of one or more of the limiting AA was not increased. Passage of bacterial N to the duodenum was highest when rumen availabilities of both nonstructural carbohydrate and protein were high.

The AA requirements of herd-replacement calves less than 5 wk old and fed milk replacers are not clearly defined and have been estimated in a limited number of studies using milk-fed calves ranging from 5 to 20 wk of age. The objective of these 4 studies was to investigate the effect of supplementing milk replacers containing 24 to 28% crude protein (CP; from milk sources) and 17% fat with Lys, Met, and Thr to estimate the optimum requirements for calves less than 5 wk of age. Holstein bull calves (initially 3 and 4 d old, 43 +/- 1 kg of body weight, BW) were fed an 18% CP (as-fed) starter ad libitum and weaned at 31 to 32 d of age (28-d studies). Calves were housed in an unheated, curtain-sided nursery. In study 1, 6 milk replacer treatments were fed based on the combination of 3 CP concentrations (24, 26, and 28% CP) each with or without added Lys and Met. In studies 2 and 3, 26% CP and 2.34% Lys milk replacer treatments were fed to test the concentration of Met (0.64, 0.68, and 0.72% Met in study 2 and 0.64, 0.72, and 0.80% Met in study 3). In study 4, 26% CP, 2.34% Lys, and 0.72% Met milk replacer treatments were fed to test the concentration of Thr (1.06, 1.43, and 1.80%). There was a 17% improvement in average daily gain (ADG) in study 1 from adding Lys and Met that was maximized with 2.34% Lys. The ADG response to added Met in studies 2 (linear) and 3 (quadratic) were 13 and 7%, respectively, with a plateau at 0.72% Met. There was no ADG or efficiency response to added Thr in study 4. Formulating 17% fat, whey-based milk replacers fed at 0.68 kg/d to 26% CP, 2.34% Lys, and 0.72% Met appeared optimum based on responses of body weight gain, feed efficiency, and serum concentrations of urea nitrogen, while feeding calves more CP and essential AA did not improved ADG and efficiency. Requirements for calves less than 5 wk old, averaging 48 kg of BW, consuming 204 g of CP/d, and gaining 0.46 kg of BW/d, appeared to be met with 17 g of Lys, 0.31 Met:Lys ratio, 0.54 Met+Cys:Lys ratio, and a Thr:Lys ratio less than 0.60.

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