Z. Wang, M. L. Eastridge1, and X. Qiu
The Ohio State University Department of Animal Sciences
Sixty Holstein cows were assigned to two treatments at 21 days before calving and were group fed a prepartum diet with or without yeast culture (YC). Cows fed YC prepartum also were fed YC postpartum (60 g/day). After parturition, cows were individually fed one of five treatments for 140 days: (1) 21% forage NDF (FNDF) without YC; (2) 21% FNDF with YC; (3) 17% FNDF without YC; (4) 17% FNDF with YC; and (5) 25% FNDF with YC for 30 days then switched to diet 4 for 110 days. A quadratic response to 25, 21, and 17% FNDF occurred during the first 30 days in milk (DIM) for DM intake, milk yield, and milk-protein yield. No differences were observed for YC or interaction of YC and forage NDF for the first 30 DIM. Feeding 17 vs. 21% FNDF increased milk-protein percentage and tended to increase DM intake as a percentage of body weight (BW) from 31 to 140 DIM. During this time period, YC tended to increase milk-fat percentage and appeared to have positive effects on DM intake, milk yield, and milk-fat yield when supplemented to diets with 21% FNDF but not with 17% FNDF. Feeding 17% FNDF may be too low for the first 30 DIM but may improve animal performance after 30 DIM compared to 21% FNDF.
Provision of forage fiber in the diet is important for optimizing milk production and maintaining rumen health. The NRC (1989) recommends a minimum of 28% NDF in the diet, of which at least 75% should be supplied by forage. This recommendation suffices for traditional forage and concentrate combinations but is not proper when substantial amounts of nonforage fiber sources are fed. Sarwar et al. (1992) replaced FNDF with NDF from soybean hulls and found that 18.6% FNDF was adequate for ruminal function and milk production when the total diet contained 31% NDF. Zhu et al. (1997) lowered FNDF to 17% for Holstein dairy cows when 31% total NDF was partially supplied with corn gluten feed, wheat middlings, or a blend of distillers dried grains and hominy. Other studies have reduced FNDF concentration to 16% with 30 to 35 % total NDF fed to Jersey (Harmison et al., 1997) and Holstein (Slater, 1998) cows; however, information on FNDF concentration for cows between parturition and peak lactation is limited.
Improvements in DM intake and milk yield (Erasmus et al., 1992; Putman et al., 1997; Robinson and Garrett, 1999; Wohlt et al., 1991), NDF digestibility (Carro et al., 1992; Plata et al., 1994; Robinson, 1997; Wohlt et al., 1991), and milk-fat yield (Putman et al., 1997) have been reported when supplementing diets with YC, but in other studies (Arambel and Kent, 1990; Swartz et al., 1994), no beneficial responses were found. Wohlt et al. (1991) suggested that supplementing YC prior to parturition and extending through the period of peak lactation was necessary to evaluate the effect of YC on lactating cows. Robinson (1997) repeated this method in a shorter period and found that YC lessened the body condition loss during the close-up dry period. The objective of this research was to determine the effects of altering the concentration of FNDF and supplementing diets with YC on the performance of lactating cows during early lactation.
Sixty dry cows and heifers were assigned to two treatments at 21 days before calving. Thirty-six of the dry cows and heifers were fed a transition diet with 60 g/day of YC (Diamond V Mills, Cedar Rapids, Iowa), and 24 were fed a diet without YC. After parturition, cows were blocked based on parity, projected milk yield, and calving date. Cows in each block received one of five treatments for 140 days: (1) 21% FNDF without YC; (2) 21% FNDF with YC; (3) 17% FNDF without YC; (4) 17% FNDF with YC; and (5) 25% FNDF with YC for 30 days then switched to diet 4 for an additional 110 days.
Dry cows and heifers were group fed, but after calving, cows were moved into a tie-stall barn and individually fed. The ingredient composition of diets is shown in Table 1. Prepartum and postpartum diets were fed as total-mixed rations. Cows were milked twice daily, and milk samples were taken weekly from four consecutive milkings and analyzed for milk fat and milk protein by infrared spectroscopy (DHI Cooperative, Inc., Powell, Ohio). After calving, cows were weighed once weekly, and body condition scores (BCS) were recorded at 21 days before parturition, at parturition, and at 28, 56, 84, 112, and 140 DIM using the 1 (thin) to 5 (fat) scale. The NEL concentration of the diets was calculated according to Weiss et al. (1998).
Table 1. Ingredient and Chemical Composition of Diets Fed to Cows Before and After Parturition1.
|25% FNDF||17% FNDF||21% FNDF||25% FNDF2|
|Ingredient||No YC||YC2||No YC||YC||No YC||YC||YC|
|% of DM|
|Dry shelled corn||17.8||17.1||17.8||17.6||25.0||24.8||19.4|
|Soybean meal, 44% CP||8.88||8.88||13.56||13.56||17.15||17.15||14.24|
|Corn gluten meal||...||...||2.25||2.25||0.29||0.29||2.25|
|Minerals and vitamins||1.05||1.10||2.60||2.63||2.59||2.52||2.49|
|1 FNDF=forage NDF and YC=yeast culture.
2 25% FNDF fed for 30 days and then cows were switched to 17% FNDF with YC for 110 days.
3 Provided by Diamond V Mills, Cedar Rapids, Iowa.
4 NSC=nonstructural carbohydrates, enzymatically analyzed value.
5 NFC=nonfiber carbohydrates calculated by difference; NFC=100 - NDFN-free - CP - ash - (fatty acids / 0.9).
6 Calculated using the model described by Weiss et al. (1998).
The lactation period was divided into the first 30 DIM and a period from 31 to 140 DIM. For the dry period, no statistical analyses were conducted because animals were group fed. The MIXED model procedure of SAS (1988) with repeated measures of week in milk was used for parameters measured during the first 30 DIM and the period from 31 to 140 DIM. The main effects of FNDF and YC and the interaction of FNDF and YC on feed intake, BW change, and milk yield and composition were evaluated using orthogonal contrasts. For the first 30 DIM, the effects of YC and the interaction between YC and FNDF were examined using treatments 1 and 3 against treatments 2 and 4, and the linear and quadratic effects of FNDF were evaluated using treatments 2, 4, and 5. For the period from 31 to 140 DIM, the contrasts were made on treatments 1, 2, 3, and 4 to analyze effects of FNDF, YC, and the interaction of YC and FNDF and on treatments 2 and 5 to measure the effect of feeding 17 or 25% FNDF with YC during the first 30 DIM on subsequent animal performance and feed efficiency.
The actual FNDF levels in the diets were similar to the expected levels for the five treatments (Table 1). The high amount of soybean hulls in the diet with 17% FNDF resulted in the lowest NSC concentration. The ratio of FNDF:NSC was 0.55 for 17 and 21% FNDF diets and 0.72 for the diet with 25% FNDF.
The average DM intake (32.1 vs. 30.6 lb/day) was numerically higher for dry cows fed the diet with YC than those not fed YC, respectively. Wallace (1994) proposed that YC increased rate of cellulolysis and flow of microbial protein, by which to increase DM intake, but effects of YC on ruminal fermentation and animal performance have been variable. Robinson (1997) did not find any improvement in DM intake prepartum when YC was fed to cows from 14 days prepartum to calving. Similar results were reported by Robinson and Garrett (1999) and Soder and Holden (1999), but the FNDF level was between 38.2 to 55.5% of dietary DM across the experiments, which is higher than that present in our trial (25% FNDF). The physical limitation to DM intake due to the high FNDF level in the diets (Ruiz et al., 1995) may overcome the effect of YC on DM intake (Carro et al., 1992).
A quadratic effect of 17, 21, and 25% FNDF occurred in diets containing YC for DM intake (40.7, 46.9, and 41.1 lb/day, respectively) during the first 30 DIM (Table 2). Dairy cows adapt to the change of dietary composition by altering microbial population and ruminal papillae development to tolerate high acid production, but complete adaptation of ruminal flora to a high-starch diet requires three to four weeks (Huntington et al., 1981) and development of the ruminal papillae takes four to six weeks (Dirksen et al., 1985). In the current study, the high concentrate diets were fed for three weeks before the projected calving date, which is less than the recommended time for ruminal papillae development. An adequate level of FNDF also should be provided to stimulate saliva secretion and increase buffering capacity. The 21% FNDF was necessary to mediate the reduction from 25% FNDF prepartum compared to 17% FNDF postpartum when soybean hulls were used as the primary source of nonforage fiber in this trial.
Table 2. Effects of Dietary Forage neutral Detergent Fiber (FNDF) Concentration and Yeast Culture (YC) Supplementation on Lactation Performance.
|17% FNDF||21% FNDF||25% FNDF||25% FNDF2|
|Item1||No YC||YC2||No YC||YC||YC||YC2||FNDF *YC2||Linear3||Quadratic3|
|0 to 30 DIM|
|DM intake lb/day||39.8||40.7||42.7||46.7||41.1||0.20||0.39||0.86||0.01|
|DM intake % of BW||3.18||3.20||3.30||3.52||3.33||0.42||0.50||0.57||0.17|
|Milk yiel, lb/day||80.5||78.3||84.0||90.2||80.1||0.62||0.31||0.75||0.03|
|3.5% FCM, lb/day||87.6||86.7||91.3||96.4||86.2||0.61||0.48||0.92||0.05|
|Milk fat, %||4.21||4.22||4.07||4.04||3.97||0.94||0.91||0.34||0.79|
|Milk protein, %||3.24||3.34||3.35||3.38||3.43||0.49||0.71||0.49||0.98|
|Milk fat, lb/day||3.26||3.26||3.39||3.54||3.17||0.64||0.67||0.71||0.13|
|Milk protein, lb/day||2.55||2.57||2.77||2.99||2.68||0.39||0.46||0.56||0.03|
|BW change, lb/day||-1.28||-0.70||-0.66||-0.92||-1.34||0.89||0.68||0.65||0.94|
|31 to 140 DIM||FNDF||YC||FNDF *YC2||Transition4|
|DM intake lb/day||55.9||52.8||51.5||54.3||54.6||0.45||0.97||0.14||0.53|
|DM intake % of BW||4.08||3.81||3.63||3.77||4.06||0.06||0.63||0.12||0.20|
|Milk yiel, lb/day||95.9||90.4||91.7||100.3||92.8||0.52||0.73||0.11||0.71|
|3.5% FCM, lb/day||93.5||90.6||88.9||99.2||90.4||0.60||0.35||0.10||0.97|
|Milk fat, %||3.36||3.53||3.33||3.48||3.36||0.65||0.08||0.85||0.18|
|Milk protein, %||3.10||3.19||3.07||3.04||3.12||0.02||0.43||0.14||0.19|
|Milk fat, lb/day||3.19||3.17||3.04||3.45||3.10||0.70||0.16||0.12||0.70|
|Milk protein, lb/day||2.97||2.88||2.79||3.04||2.86||0.92||0.55||0.19||0.39|
|BW change, lb/day||0.31||0.31||0.64||-0.11||0.57||0.91||0.39||0.39||0.65|
|1 DIM=days in milk, BW=body weight,
and FCM=fat-corrected milk.
2 21% FDNF without YC, 21% FNDF with YC, 17% FNDF without YC, and 17% FNDF with YC were used for contrast.
3 Linear and quadratic effects of FNDF using treatments with 17, 21, and 25% FNDF with YC.
4 Transition: Cows fed 17% FNDF with YC during 0 to 140 DIM vs. cows fed 25% FNDF with YC during the first30 DIM and 17% FNDF with YC during 31 to 140 DIM.
After 30 DIM, cows fed diets with 17% FNDF tended to have higher DM intake as a percentage of BW (3.95 vs. 3.70%) than those fed diets with 21% FNDF. Slater (1998) reported no difference in DM intake for cows at 60 DIM fed diets with 21% FNDF compared to those fed diets with 16% FNDF. Harmison et al. (1997) reported that DM intake decreased linearly as FNDF decreased from 21 to 11%, but most of the DM intake reduction was when the level of FNDF dropped from 16 to 11%. No effect was found for feeding cows 25 vs. 17% FNDF with YC during the first 30 DIM on subsequent feed intakes during 31 to 140 DIM.
No effects of YC or an interaction of YC and FNDF on DM intake was observed during 31 and 140 DIM. The effect of YC on DM intake has been variable. Erasmus et al. (1992) and Wohlt et al. (1991) reported increased DM intake by YC supplementation, but Arambel and Kent (1990) and Kamalamma et al. (1996) did not observe an effect of YC on DM intake. Besides the factors of stage of lactation and basal diets fed, the viable yeast cell number in YC or amount of YC supplemented should also be considered (Kamalamma et al., 1996).
A quadratic effect of FNDF for yields of milk (78.3, 90.2, and 80.1 lb/day), 3.5% fat-corrected milk (FCM) (86.7, 96.4, and 86.2 lb/day), and milk protein (2.57, 2.99, and 2.68 lb/day) was found for cows receiving YC-containing diets with 17, 21, and 25% FNDF, respectively, during the first 30 DIM. The increased yields of milk and milk protein can probably be explained by the higher DM intake by cows fed YC-containing diets with 21% FNDF than those with 17 or 25% FNDF.
No effect of YC on milk production was found during the first 30 DIM, which was consistent with the report by Soder and Holden (1999) and Wohlt et al. (1998) but not with another report by Wohlt et al. (1991). This may be because there was no effect of YC on DM intake during the first 30 DIM.
Feeding diets with 17% FNDF increased milk-protein percentage (3.15 vs. 3.05%) compared with 21% FNDF during 31 to 140 DIM. Milk yield and milk-protein percentage were increased when nonforage fiber sources were used to reduce FNDF from 22.1 to 12%, but milk-fat percentage decreased as FNDF decreased (Clark and Armentano, 1997). Feeding diets with 17% FNDF compared to 25% FNDF during the first 30 DIM did not affect animal performance when cows were fed the diet with 17% FNDF plus YC during 31 to 140 DIM.
The effects of YC on milk yield and milk composition were generally not significant after 30 DIM. These results agreed with studies of Soder and Holden (1999) and Wohlt et al. (1991) but not with the study of Piva et al. (1993), who reported increased yields of milk and milk fat when cows in midlactation were fed YC in diets with 48% concentrate. Wohlt et al. (1998) showed that 20 g/day YC tended to increase yields of milk, 3.5% FCM, and milk fat compared to diets without YC because of increased DM intake and the higher digestibilities of CP and ADF. Feeding YC in our study tended to increase milk fat percentage. The interaction of FNDF concentration and YC approached significant trends (P = 0.10 to 0.14) for DM intake, yields of milk, 3.5% FCM, and milk fat, and milk-protein percentage during 31 to 140 DIM. Cows fed the diet with 21% FNDF appeared to have better responses to YC supplementation than those fed the diet with 17% FNDF.
There were no effects from YC, FNDF concentration, and interaction between YC and FNDF concentration on BW changes of cows during the first 30 DIM and the period between 31 and 140 DIM. The average BCS during 0 to 140 DIM was 2.55, 2.83, 2.79, 2.91, and 2.93 for cows fed 17% FNDF, 17% FNDF with YC, 21% FNDF, 21% FNDF with YC, and 25% FNDF with YC for 30 DIM and 17% FNDF with YC during 31 and 140 DIM, respectively, and no effects of treatments on BCS were observed.
In conclusion, diets with 21% FNDF may be better for cows during the first 30 DIM. After peak lactation, however, 17% FNDF may be sufficient to maintain DM intake and milk production of cows when total NDF is more than 30% of dietary DM. The responses to YC supplementation after parturition appeared to be higher for cows fed diets with 21% FNDF than for cows fed diets with 17% FNDF. Even though nonstructural carbohydrate (NSC) concentration differed when dietary FNDF concentration changed, diets in this trial were formulated to maintain FNDF:NSC ratio at more than 0.5. It is important to reduce NSC concentration when the level of FNDF is decreased, and therefore, the effect of FNDF on animal performance should be evaluated in conjunction with dietary NSC concentration.
Appreciation is extended to Diamond V Mills (Cedar Rapids, Iowa) for partial support of this research.
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1 For more information, contact at: The Ohio State University, 221B Animal Science Building, 2029 Fyffe Road, Columbus, OH 43210; (614) 688-3059, Fax (614) 292-1515; email:email@example.com