Trop Anim Health Prod DOI 10.1007/s11250-014-0704-4

REGULAR ARTICLES

Starch levels on performance, milk composition and energy balance of lactating dairy cows Carolina Almeida Carmo & Fernanda Batistel & Jonas de Souza & Junio Cesar Martinez & Paulo Correa & Alexandre Mendonça Pedroso & Flávio Augusto Portela Santos

Received: 20 June 2014 / Accepted: 5 October 2014 # Springer Science+Business Media Dordrecht 2014

Abstract The objective of this experiment was to evaluate the effects of starch levels in diets with the replacement of citrus pulp for corn on milk yield, milk composition, and energy balance of lactating dairy cows. Twenty-eight multiparous Holstein cows were used in seven 4×4 Latin squares conducted concurrently, and each experimental period consisted of 20 days (16 days for adaptation and 4 days for sampling). The experimental treatments comprised four starch levels: 15, 20, 25, and 30 % in the diet. The dry matter intake increased linearly with increasing starch levels. The milk yield and 3.5 % fat-corrected milk yield showed quadratic response to increasing starch levels. The milk protein content and milk total solids content responded linearly to increasing starch levels. The feed efficiency, milk lactose content, milk urea nitrogen, plasma urea nitrogen, and plasma glucose concentration were not affected by starch levels. The estimated net energy for lactation (NEL) intake increased linearly as the starch level was raised. Although the milk NEL output per kilogram of milk was not affected by starch, the milk NEL output daily responded quadratically to starch levels. In addition, the NEL in body weight gain also responded quadratically to increasing starch levels. The efficiency of energy use for milk yield and the NEL efficiency for production also responded quadratically to increasing starch levels. Diets for mid-lactating dairy cows producing around 30 kg/day of milk C. A. Carmo : F. Batistel : J. de Souza : P. Correa : F. A. P. Santos (*) Department of Animal Science, University of São Paulo, Piracicaba, São Paulo, Brazil e-mail: [email protected] J. C. Martinez Department of Animal Science, Mato Grosso State University, Pontes e Lacerda, Mato Grosso, Brazil A. M. Pedroso Embrapa Southeast Livestock, São Carlos, São Paulo, Brazil

should be formulated to provide around 25 % starch to optimize performance. Keywords Citrus pulp . Energy balance . Performance . Starch levels

Introduction Starch is a major energy source in diets of lactating dairy cows, and diets of high-producing dairy cows usually contain between 20 and 30 % starch on dry matter (DM) basis (Akins et al. 2014; Vargas-Rodriguez et al. 2014). Corn is the grain most commonly used in Brazil to formulate energy-dense diets required by dairy cows, promoting extensive microbial protein synthesis in the rumen due to its high-starch content (NRC 2001). Although there is no apparent limit in terms of rumen capacity to digest starch, problems associated with high-starch diets result from excessively rapid fermentation of starch to organic acids reducing ruminal pH and, as a result, lower ruminal pH and decreasing appetite, fiber digestion, microbial yield, and milk fat concentration (Calsamiglia et al. 2012; Monnerat et al. 2013). The use of corn grain in the biofuel industry is growing, and, in turn, increased competition for corn is pushing up feed costs (Farmers et al. 2014). The partial replacement of starch with cost-effective, low-starch, nonforage fiber sources represents a potential alternative to help overcome these issues (Hall and Chase 2014). Previous studies were conducted on partial substitution of starch for nonforage fiber sources such as soybean hulls (Aikman et al. 2006), beet pulp (Voelker and Allen 2003), and citrus pulp (Leiva et al. 2000). However, data reporting nonforage pectin-rich fiber sources, such as citrus pulp replacing corn in diets, are scarce in the literature for lactating dairy cows.

Trop Anim Health Prod

The objective of this experiment was to evaluate the effects of starch levels in diets with the replacement of citrus pulp for corn on milk yield, milk composition, and energy balance of lactating dairy cows.

The cows were housed in a free stall barn grouped in four pens equipped with water bowls. The cows were milked twice a day at 0600 and 1800 hours. Each pen was composed by cows from the seven Latin squares. Sampling, measurements, and analyses

Material and methods Animals, experimental design, and diets All procedures were approved by the Ethical Committee for Animal Research of the University of São Paulo. Twenty-eight multiparous Holstein cows, averaging 602± 32 kg of BW and 180±70 days in milk (DIM) at the onset of the experiment, were used in seven 4×4 Latin squares conducted concurrently. Each trial period consisted of 16 days of adaptation and 4 days for data collection. Milk production at the 21-day pretrial period was the criteria used to assign cows to the seven Latin squares. During the trial period, the average temperature was 24.9 °C. Within each square, cows were randomly assigned to treatment sequences. The treatments consisted of 15, 20, 25, and 30 % of starch in the diets, identified as 15S, 20S, 25S, and 30S, respectively. Starch levels were increased by replacing citrus pulp for ground corn (geometric mean diameter of corn=1.2 mm; Table 1). The diets were fed as total mixed ration (TMR) twice a day at 0600 and 1800 hours at amounts to ensure 10 % orts. The diets were adjusted weekly to reflect changes in DM content of silage and concentrate mixtures by drying the forages and concentrates overnight at 105 °C. Table 1 Diet ingredient and chemical composition (DM basis) Percent

Ingredients Corn silage Fine ground corn Citrus pulp Soybean meal Cottonseed meal Sodium bicarbonate Min. vit. premix Chemical composition Dry matter Organic matter Crude protein Neutral detergent fiber Acid detergent fiber Starch

Level of starch (%) 15

20

25

30

45.0 6.6 19.6 9.8 15.5 0.7 2.8

45.0 13.1 13.1 9.8 15.5 0.7 2.8

45.0 19.2 7.0 9.8 15.5 0.7 2.8

45.0 26.2 0.0 9.8 15.5 0.7 2.8

47.7 92.8 18.1 32.6 18.8 14.8

47.7 93.0 18.1 31.8 17.9 20.0

47.6 93.2 18.2 30.7 16.9 25.1

47.5 93.7 18.3 29.9 15.8 30.4

The feed offered and refused was recorded daily. The dry matter intake (DMI) per pen was measured through the difference between the DM feed offered and DM feed refused (orts). Samples of TMR and orts were collected daily, and the DM content was determined by drying samples from each experimental group of cows at 105 °C for 24 h. Samples of forages, concentrates, and TMR were collected once a week and stored frozen at −18 °C for later analyses. At the end of each experimental period, feed subsamples from the weekly collections were thawed, combined on an equal weight basis, and analyzed for ash content after combustion at 550 °C for 8 h. The total nitrogen was determined in the Dumas method, and neutral detergent fiber (NDF) was determined according to Van Soest et al. (1991) with heat-stable αamylase and sodium sulfite. The starch content was determined according to Poore et al. (1991). The net energy for lactation (NEL) concentration of TMR was estimated using chemical composition of individual ingredients, in accordance to DMI and NRC (2001) summative equations. The NEL intake was calculated as NEL concentration of the diet× DMI. The output of NEL in the milk (Mcal/kg) was calculated as 0.0929×fat %+0.0563×true protein %+0.0395×lactose %, and NEL in the milk (Mcal/day) was obtained by multiplying milk yield for NEL in the milk (Mcal/kg) according to NRC (2001). The NEL in body weight gain (BWG) was calculated as BWG×5.34 Mcal/kg (NRC 2001). The NEL available for maintenance was NEL intake (Mcal/day)−NEL in the milk (Mcal/day)−NEL in BWG (Mcal/day). Milk production was recorded daily and milk samples were collected at each milking between day 16 and 20 of each period. The samples were preserved with 2-bromo-2nitropropane-1,3-diol and stored at 4 °C. The samples were analyzed for fat, protein, lactose, total solids, and milk urea nitrogen (MUN) using infrared procedures (Foss 4000; Foss North America, Eden Prairie, MN). Blood samples from the coccygeal vessels were obtained 4 h after morning feeding of the last day of each sampling period. The samples were collected using vacutainers with potassium oxalate as anticoagulant. After collection, samples were centrifuged for 20 min at 2,000×g at 4 °C. Plasma samples were stored at −10 °C until the glucose analysis in the plasma using an auto-analyzer (YSI 2700 Select – Biochemistry analyzer, Yellow Spring, OH, USA). The plasma urea nitrogen (PUN) was analyzed in a commercial laboratory using a Sigma N-535 kit (Sigma Chemical Co., St. Louis, MO, USA).

Trop Anim Health Prod

Statistical analyses Data were analyzed using the PROC MIXED of SAS. The DMI was measured on a pen basis, with one pen per treatment during each period because cows were group fed. Therefore, a pen was considered as the experimental unit for statistical analysis of DMI. The cows were considered the experimental unit for statistical analysis of milk yield and composition, blood parameters, body condition score variation, and energy balance. For temporal analyses (milk yield, milk composition, and DMI), the data were analyzed as repeated measures. The covariance structure used for each repeated measures analysis was chosen based on the parameters Akaike information criterion, corrected Akaike information criterion, and Bayesian information criterion of SAS. The model included treatments as fixed effects, while animal, period, and square were random effects. The treatment means were compared using orthogonal polynomial coefficients and the linear and quadratic effects were tested.

Results The chemical composition of the experimental diets is shown in Table 1. The contents of CP, DM, and OM were similar among treatments. However, the NDF diet was slightly increased as with the replacement of corn for citrus pulp. Starch levels were close to expectation: 14.8, 20.0, 25.1, and 30.4 % for 15S, 20S, 25S, and 30S, respectively. The DMI and DMI in relation to metabolic body weight increased linearly (P=0.03 and P=0.02, respectively) as starch levels increased (Table 2). Milk yield (P

Starch levels on performance, milk composition and energy balance of lactating dairy cows.

The objective of this experiment was to evaluate the effects of starch levels in diets with the replacement of citrus pulp for corn on milk yield, mil...
157KB Sizes 0 Downloads 5 Views