A.J. Heinrichs

A prospective study of calf factors affecting first-lactation and lifetime milk production and age of cows when removed from the herd1

This prospective study was designed to investigate possible carryover effects of calf management practices and how events occurring during the first 16 wk of life affect first-lactation and lifetime milk production as well as age when animals are removed from production. This is the final of 3 stages in a longitudinal study that encompassed 10 yr of data collection. First, management and nutritional data were collected in the first 16 wk of life. The second part of this study evaluated conditions of animals at the time of first calving as affected by calf management, nutrition, and health. Both of these studies have been previously reported. This third portion covers the same calf effects on lactation performance and age at culling. Observations for the current study were collected from on-farm and Dairy Herd Improvement records. The multiple imputation technique was used in this analysis to avoid bias due to missing data. This study concluded that delivery score, weaning dry matter intake, days of illness before 4 mo, days treated before 4 mo, and body weight at first calving all had significant effects on first-lactation production of Holsteins. Delivery score and grain intake at a young age affected lifetime production. Age at culling was only affected by early grain intake in this study.

Short communication: Heritability of gross feed efficiency and associations with yield, intake, residual intake, body weight, and body condition score in 11 commercial Pennsylvania tie stalls

The objectives of this study were to calculate the heritability of feed efficiency and residual feed intake, and examine the relationships between feed efficiency and other traits of productive and economic importance. Intake and body measurement data were collected monthly on 970 cows in 11 tie-stall herds for 6 consecutive mo. Measures of efficiency for this study were: dry matter intake efficiency (DMIE), defined as 305-d fat-corrected milk (FCM)/305-d DMI, net energy for lactation efficiency (NELE), defined as 305-d FCM/05-d NEL intake, and crude protein efficiency (CPE), defined as 305-d true protein yield/305-d CP intake. Residual feed intake (RFI) was calculated by regressing daily DMI on daily milk, fat, and protein yields, body weight (BW), daily body condition score (BCS) gain or loss, the interaction between BW and BCS gain or loss, and days in milk (DIM). Data were analyzed with 3- and 4-trait animal models and included 305-d FCM or protein yield, DM, NEL, or CP intake, BW, BCS, BCS change between DIM 1 and 60, milk urea nitrogen, somatic cell score, RFI, or an alternative efficiency measure. Data were analyzed with and without significant covariates for BCS and BCS change between DIM 1 and 60. The average DMIE, NELE, and CPE were 1.61, 0.98, and 0.32, respectively. Heritability of gross feed efficiency was 0.14 for DMIE, 0.18 for NELE, and 0.21 for CPE, and heritability of RFI was 0.01. Body weight and BCS had high and negative correlations with the efficiency traits (-0.64 to -0.70), indicating that larger and fatter cows were less feed efficient than smaller and thinner cows. When BCS covariates were included in the model, cows identified as being highly efficient produced 2.3 kg/d less FCM in early lactation due to less early lactation loss of BCS. Results from this study suggest that selection for higher yield and lower BW will increase feed efficiency, and that body tissue mobilization should be considered.

Genetic parameters of feed intake, production, body weight, body condition score, and selected type traits of Holstein cows in commercial tie-stall barns.

The objectives of this study were to determine the feasibility of measuring feed intake in commercial tie-stall dairies and infer genetic parameters of feed intake, yield, somatic cell score, milk urea nitrogen, body weight (BW), body condition score (BCS), and linear type traits of Holstein cows. Feed intake, BW, and BCS were measured on 970 cows in 11 Pennsylvania tie-stall herds. Historical test-day data from these cows and 739 herdmates who were contemporaries during earlier lactations were also included. Feed intake was measured by researchers once per month over a 24-h period within 7 d of 6 consecutive Dairy Herd Information test days. Feed samples from each farm were collected monthly on the same day that feed intake was measured and were used to calculate intakes of dry matter, crude protein, and net energy of lactation. Test-day records were analyzed with multiple-trait animal models, and 305-d fat-corrected milk yield, dry matter intake, crude protein intake, net energy of lactation intake, average BW, and average BCS were derived from the test-day models. The 305-d traits were also analyzed with multiple-trait animal models that included a prediction of 40-wk dry matter intake derived from National Research Council equations. Heritability estimates for 305-d intake of dry matter, crude protein, and net energy of lactation ranged from 0.15 to 0.18. Genetic correlations of predicted dry matter intake with 305-d dry matter, crude protein, and net energy of lactation intake were 0.84, 0.90, and 0.94, respectively. Genetic correlations among the 3 intake traits and fat-corrected milk yield, BW, and stature were moderate to high (0.52 to 0.63). Results indicate that feed intake measured in commercial tie-stalls once per month has sufficient accuracy to enable genetic research. High-producing and larger cows were genetically inclined to have higher feed intake. The genetic correlation between observed and predicted intakes was less than unity, indicating potential variation in feed efficiency.

Digestion and nitrogen utilization in dairy heifers limit-fed a low or high forage ration at four levels of nitrogen intake.

The hypothesis of this experiment is that a low-forage (LF) ration will be utilized with greater efficiency than a high-forage ration (HF) by dairy heifers and that the response will be affected by level of N intake. To test this hypothesis, 8 Holstein heifers (beginning at 362 +/- 7 kg and 12.3 +/- 0.4 mo) were fed 8 rations according to a split-plot, 4 x 4 Latin square design. Treatments were formulated to contain 25 or 75% forage (corn silage and chopped wheat straw) and fed at 4 levels of N intake [0.94 (Low), 1.62 (MLow), 2.30 (MHigh), 2.96 (High) g of N/kg of metabolic body weight per day]. Diets were limit-fed to maintain equal intake of metabolizable energy. Blood samples were collected over d 19 to 20, and feces and urine were collected for 8 d per 28-d period. Organic matter (OM) intake was greater for heifers fed HF, but, due to increased OM digestibility of LF (74.0 vs. 67.6% +/- 0.9), digestible OMI was unaffected by forage level. Organic matter digestibility was affected by an interaction between forage level and N intake, increasing to a plateau of 78.01% at 18.43% crude protein for LF-fed and 68.78% at 13.90% crude protein for HF-fed heifers. Apparent N digestibility was greater for heifers fed LF and increased from 47.7 to 80.8% between Low and High N intake. Less N appeared in the feces of heifers fed LF than HF (45.56 vs. 52.60 g/d). Urea-N excretion was not different between forage levels, but increased linearly with N intake. Concentration of plasma urea-N was significantly higher for LF and with increasing N intake. Urea clearance rate (L/h) did not differ between forage levels and increased, but at a decreasing rate, as N intake increased. A significant interaction resulted from urea clearance increasing at a greater rate and resulting in higher values for HF, whereas clearance of urea for heifers fed LF resulted in significantly lower maximal values. Like urea-N excretion, daily urinary N excretion was affected only by N intake. Retained N responded linearly to increased levels of N intake. The significant reduction observed in fecal N excretion for LF was counterbalanced by numerical increases in urinary N excretion so that total N excretion and retention were not different between forage levels. The percentage of N intake that was retained only tended to be affected by an interaction and was not significantly affected by forage level. It is concluded that increasing N intake increases the digestibility of OM, the magnitude of which depends on the level of dietary forage provided. Furthermore, differences in N utilization between LF and HF in this trial were small and were not evident until N intake increased to impractical levels.

Effect of limit feeding high- and low-concentrate diets with Saccharomyces cerevisiae on digestibility and on dairy heifer growth and first-lactation performance

Growth and digestibility were examined for heifers limit fed high- (HC; 60%) and low-concentrate (LC; 20%) diets with or without yeast culture (YC) addition in 2 experiments. A third experiment was undertaken to monitor first-lactation production of heifers limit fed HC or LC diets. In experiment 1, 32 Holstein heifers were individually fed at controlled intakes for 133 d to maintain a targeted average daily gain of 0.80 kg/d for all 4 treatments [HC; LC with and without Saccharomyces cerevisiae; Yea-Sacc(1026) (Alltech Inc., Nicholasville, KY), 1 g/kg as fed]. Targeted average daily gain was achieved for all treatments during the individual feeding period (0.80 +/- 0.01 kg/d). Average dry matter intake needed to maintain constant gain was slightly reduced for HC and YC treatments. Reduced dry matter intake and similar targeted average daily gain resulted in a tendency for improved feed efficiency of HC-fed heifers. Skeletal measurements and targeted average daily gain were not affected by concentrate level or YC. The objective of experiment 2 was to elucidate effects of concentrate level and YC on nutrient digestibility. Four young (284.35 +/- 4.51 d) and 4 older (410.28 +/- 2.14 d) heifers were allocated to the 4 treatments used in experiment 1. Heifers fed the HC diet had increased dry matter digestibility (75.67 vs.72.96 +/- 0.72%), and YC addition increased dry matter digestibility (74.97 vs. 73.65 +/- 0.71%). Intake of N and apparent N digestibility were similar for all treatments. High-concentrate diets and YC addition decreased wet and dry matter output of feces. Urine excretion was not different; therefore, total manure output was lower for HC-fed heifers as compared with LC-fed heifers. Results suggest that HC diets can improve feed efficiency without affecting growth when limit fed to dairy heifers. Yeast culture increased dry matter digestibility in HC- and LC-fed heifers; HC diets were more digestible and reduced fecal output, with YC enhancing this effect. In experiment 3, heifers from experiment 1 were group fed the same diets (HC or LC) without YC until parturition, and milk production was measured through 154 d of lactation. Group-fed average daily gain was not different between treatments (HC = 1.11 vs. LC = 1.04 kg/d, SE = +/-0.06 kg/d). Heifers fed the HC and LC diets calved at 23.50 and 23.79 +/- 0.50 mo, respectively. Peak milk was lower and there was a tendency for reduced daily milk and protein yield for primiparous cows fed HC diets from 8 mo of age to the dry/prefresh period (long term), but predicted yields of milk and components were similar in the first 154 d of lactation.

A review of the importance and physiological role of curd formation in the abomasum of young calves

Abstract The importance of abomasal protein clotting for optimal nutrient utilization, health and growth of milk-fed calves remains a controversial issue. Clotting of casein in whole, waste and colostral milks was thought to be responsible for improved digestibility, greater daily gains and improved calf health. Early milk replacers were formulated with casein containing protein sources. The milk replacer industry in the United States is currently using protein sources that are non-clotting, primarily whey and soy protein, in the formulations of replacers. In the past, milk replacers that exhibited no curd formation were characterized as inferior because of their association with poor growth rates and high incidences of diarrhea. Research suggests that factors other than clotting are directly responsible for this decreased performance. The calfs immature digestive system during the first three weeks of life indicates a physiological need for clotting in the abomasum to fully utilize complex proteins. Thus whole milk proteins are suggested by some as the most suitable liquid diets for this age. Enzymatic secretion is limited up to one month of age, restricting digestion of carbohydrate, fat and protein. After three weeks of age most calves can perform comparably when fed non-clotting milk replacers. Inhibition of coagulation with an oxalate–sodium buffer illustrated that clotting may only affect nutrient flow and not nutrient digestibility or performance of calves. Therefore, clotting may not be the fundamental element causing poor performance. Evidence suggests that the types of protein sources, the manufacturing methods and the inclusion of other less digestible sources of nutrients in the milk replacer may be the components hindering the growth and health of calves less than one month of age. The physical or chemical nature of milk substitutes as well as their digestibility may influence the nutrient delivery from the abomasum to the small intestine. The milk replacer industry in the US has been formulating milk replaces based on calf performance rather than only analyzed quality.

Effects of feeding different levels of dietary fiber through the addition of corn stover on nutrient utilization of dairy heifers precision-fed high and low concentrate diets

The objective of this experiment was to assess the effects of manipulating dietary fiber by replacing corn silage (CS) with lower quality forage as corn stover (CST) when used in high concentrate (HC) and low concentrate (LC) diets for precision-fed dairy heifers. Eight Holstein heifers (335.6 ± 7.41 kg of body weight) were randomly assigned to 2 levels of concentrate: HC (20% forage) and LC (80% forage), and to a forage type sequence [0% of forage as corn stover (CST), 100% corn silage (CS); 20% CST, 80% CS; 40% CST, 60% CS; and 60% CST, 40% CS] within concentrate level administered according to a split-plot, 4 × 4 Latin square design (21-d periods). Heifers fed HC had higher apparent total-tract dry matter digestibility (DMD). Increasing the fiber level by increasing the amount of CST in the diet resulted in a linear decrease of DMD and organic matter digestibility. Heifers fed LC diets had higher neutral detergent fiber (NDF) digestibility and tended to have lower acid detergent fiber (ADF) digestibility than those fed HC diets. Substituting CS with 20% CST resulted in the highest NDF and ADF digestibilities. Digestibility of N was not different, but N retention increased for HC and decreased quadratically for LC diets. Heifers fed HC diets decreased fecal output, and CST linearly increased these parameters. Urine volume tended to be higher for HC-fed heifers, and increasing dietary fiber through CST inclusion tended to decrease urine output. This shift in water excretion resulted in similar total manure output. Total purine derivative excretion did not differ between treatments, but interacted with CST addition, resulting in a linear increase in microbial protein flow to the duodenum in HC-fed heifers and in a linear decrease in LC diets as CST increased. In conclusion, increasing dietary fiber through CST decreased DMD and organic matter digestibility linearly, whereas NDF and ADF digestibility were maximized when 20% CST was added to HC and LC diets. Microbial protein synthesis increased and decreased linearly with CST addition in HC and LC diets, respectively. Retention of N increased and decreased quadratically with CST addition in HC and LC diets, respectively. Total manure excretion was not different between HC or LC diets.

Rumen Digestion and Nutritional Efficiency of Dairy Heifers Limit-Fed a High Forage Ration to Four Levels of Dry Matter Intake

Eight rumen-cannulated Holstein dairy heifers [beginning body weight (BW) 340 (+/-5) kg and age 14.5 (+/-1) mo] were fed a high forage diet at 4 levels of intake. Diets were composed of grass silage, grass hay, and corn silage as the forage components and offered at 1.25, 1.50, 1.75, and 2.00% of BW to heifers in a replicated Latin square design. Diets were incubated in situ in heifers receiving all 4 levels of feed. Blood and rumen were sampled at 2-h intervals for 24 h, rumen contents were emptied, and total fecal and urine collection was made. Dietary intake increased in proportion to feed offered until dry matter intake (DMI) was 1.92% BW, after which a statistically determined plateau was evident due to greater refusals when feed was offered at 2.00% BW. In situ degradation of feed was not affected by intake level, which, combined with the greater turnover rate of rumen contents, leads to the inference that rate of passage was increased with increasing intake. Rumen pH decreased and rumen volatile fatty acid concentration and microbial protein flow to the small intestine (estimated using urinary purine derivative excretion) increased as intake increased. Manure excretion increased as DMI increased at a rate 2.54 times greater than increases in DMI; this increase was entirely due to greater excretion of wet feces because urine excretion did not change with intake level. Nitrogen digestibility decreased and N retention increased linearly as the level of feed offered increased. Efficiency of N retention was minimized when feed was offered at 1.25% BW; all levels of feed offered above this level resulted in equivalent efficiencies. From the results of this experiment it can be concluded that when dairy heifers are limit-fed a high forage diet, the efficiency of nutrient utilization is increased as intake decreases, but reducing DMI below 1.50% BW reduced efficiency.

Effect of feed sorting on chewing behavior, production, and rumen fermentation in lactating dairy cows.

Ration sorting is thought to allow cows to eat different rations throughout the day, causing fluctuations in rumen fermentation patterns that can be detrimental to production and possibly animal health. The objective of this experiment was to study the effects of varying total mixed ration (TMR) particle size on sorting behavior of lactating dairy cows and to evaluate effects on chewing behavior, milk yield, milk components, and rumen fermentation. Eight multiparous, Holstein cows (90±32 d in milk; 4 rumen cannulated) were randomly assigned to replicated 4×4 Latin squares. Cows were fed diets that varied in the chop length of dry grass hay. The diet consisted of 29.4% corn silage, 22.9% ground corn, 17.6% alfalfa haylage, and 11.8% dry grass hay on a dry matter basis. The percentage of hay particles >26.9 mm was 4.2, 34.1, 60.4, and 77.6% for the short (S), medium (M), long (L), and extra long (XL) hays, respectively. This resulted in the TMR of each diet having 1.5 (S), 6.5 (M), 8.6 (L), and 11.7% (XL) of particles >26.9 mm. Daily ruminating time [19.3, 19.2, 22.4, and 21.3 min/kg of dry matter intake (DMI) for S, M, L, and XL] and eating time (13.9, 14.6, 17.2, and 16.1 min/kg of DMI for S, M, L, and XL) increased linearly as TMR particle size increased. Daily DMI decreased linearly as TMR particle size increased and was 26.9 (S), 27.0 (M), 24.1 (L), and 25.1 (XL) kg/d. No differences were found in rumen volatile fatty acids and NH(3), and only slight changes were found in rumen pH. Milk production and milk components were also similar among diets. Despite large differences in particle size among these diets and certain chewing and ruminating differences, no changes in rumen fermentation, milk production, or milk components were found in this study.

Effect of varying total mixed ration particle size on rumen digesta and fecal particle size and digestibility in lactating dairy cows1

The objective of this experiment was to evaluate the effects of feeding rations of different particle sizes on rumen digesta and fecal matter particle size. Four rumen-cannulated, multiparous, Holstein cows (104±15 d in milk) were randomly assigned to treatments in a 4×4 Latin square design. The diets consisted of 29.4% corn silage, 22.9% ground corn, 17.6% alfalfa haylage, and 11.8% dry grass hay [20% of forage dry matter (DM)] on a DM basis. Dry grass hay was chopped to 4 different lengths to vary the total mixed ration (TMR) particle size. Geometric mean particle sizes of the rations were 4.46, 5.10, 5.32, and 5.84 mm for short, medium, long, and extra long diets, respectively. The ration affected rumen digesta particle size for particles ≥3.35 mm, and had no effect on distribution of particles <3.35 mm. All rumen digesta particle size fractions varied by time after feeding, with soluble particle fractions increasing immediately after feeding and 0.15, 0.6, and 1.18-mm particle size fractions decreasing slightly after feeding. Particle fractions >1.18 mm had ration by time interactions. Fecal neutral detergent fiber (NDF) and indigestible NDF concentrations decreased with increasing TMR particle size. Fecal particle size expressed as total geometric mean particle length followed this same tendency. Fecal particle size, expressed as retained geometric mean particle length, averaged 1.13 mm with more than 36% of particles being larger than 1.18 mm. All fecal nutrient concentrations measured were significantly affected by time after feeding, with NDF and indigestible NDF increasing after feeding and peaking at about 12h later and then decreasing to preprandial levels. Starch concentrations were determined to have the opposite effect. Additionally, apparent digestibility of diet nutrients was analyzed and DM digestibility tended to decrease with increasing TMR particle size, whereas other nutrient digestibilities were not different among rations. These results show that the critical size for increased resistance to rumen escape is larger than 1.18 mm and this critical size is constant throughout the day. This study also concludes that, when using average quality grass hay to provide the range of particle sizes fed, DM digestibility tends to decrease with increasing ration particle size.