Forage and protein use efficiency in dairy cows grazing a mixed grass-legume pasture and supplemented with different levels of protein and starch
| Autor: | J. Castro-Montoya, S. Glowacki, Uta Dickhoefer, Carlos Gómez |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
0301 basic medicine
chemistry.chemical_classification geography Meal geography.geographical_feature_category General Veterinary Silage Starch 0402 animal and dairy science food and beverages Forage 04 agricultural and veterinary sciences 040201 dairy & animal science Pasture 03 medical and health sciences chemistry.chemical_compound 030104 developmental biology Animal science chemistry Grazing Animal Science and Zoology Organic matter Legume |
| Zdroj: | Livestock Science. 216:109-118 |
| ISSN: | 1871-1413 |
| DOI: | 10.1016/j.livsci.2018.08.004 |
| Popis: | The aim was to analyze the effects of a supplementation of concentrate mixtures (CM) differing in their concentrations of rumen-degradable crude protein and readily fermentable carbohydrates on feed intake, diet digestibility, milk performance, and nitrogen (N) partitioning in lactating dairy cows grazing a mixed grass-legume sward. Three dietary treatments were tested with two groups of dairy cows during three experimental periods (14 d adaptation and 5 d sampling) following a 2 × 3 Youden square design. Each cow daily received 4.12 kg CM (as-fed basis) distributed over two meals in addition to maize silage and the grazing of an alfalfa-clover-rye grass sward. The three CM contained (as-fed basis): 4 kg/d of dried distillers’ grains with solubles (DDGS) and no maize kernel meal (MM) (HPLS; high protein-low starch), 2.5 kg/d DDGS and 1.5 kg/d MM (MPMS; medium protein-medium starch), and 1 kg/d DDGS and 3 kg/d MM (LPHS; low protein-high starch). Additionally, 0.12 kg/d of a mineral-vitamin mixture was added to each CM. Fecal excretion was determined using the external marker titanium dioxide and apparent total tract digestibility of ingested organic matter (OM) estimated from crude protein concentration in fecal spot samples in order to calculate daily OM and N intakes of cows. Total OM intake and OM intake during grazing did not differ between CM. However, digestibility of ingested OM and daily milk yield were lowest for LPHS. Total N intake and urinary N excretion decreased from HPLS to MPMS and LPHS. Accordingly, N use efficiency (in g milk N per g of N intake) was higher for LPHS (0.249) than for HPLS (0.189) and MPMS (0.209). Feeding CM low in rumen-degradable crude protein and rich in readily fermentable carbohydrates may slightly reduce diet digestibility and milk yield in dairy cows grazing mixed grass-legume swards, but can greatly improve N use efficiency and lower the risk of N emissions into the environment. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect