Replacing alfalfa hay with triticale hay has minimal effects on lactation performance and nitrogen utilization of dairy cows in a semi-arid region of Mexico

摘要

In the semi-arid highlands of central Mexico, triticale(× Triticosecale L.) is emerging as an alternative,less water-demanding forage crop than alfalfa for dairycattle. Studies reported here were aimed at evaluatingtriticale hay (TH) relative to alfalfa hay (AH) for lactatingcow performance, apparent digestibility, N partition,and ruminal degradation kinetics of dry matter(DM), crude protein (CP), and neutral detergent fiber(NDF). Study 1 was conducted on a privately ownedfarm. Four barns were used to conduct 4 replicated 3 ×3 Latin squares (1 barn = 1 square), where each barnincluded 3 pens (experimental units) receiving 1 of 3 dietarytreatments. Each pen had 62 Holstein dairy cows.All diets included a forage-to-concentrate ratio of 42:58(DM basis), which is typical for intensive dairy farmsof the region. Dietary treatments were formulated toreplace AH with TH on a CP basis, and included (DMbasis) 15.1% AH and 0% TH, 9.0% AH and 7.4% TH,and 0% AH and 16.4% TH. Diets were iso-energetic(1.64 Mcal of net energy for lactation/kg of DM) andiso-nitrogenous (17.9% CP). Pen-level DM intake andmilk production were from all cows in the pen, butpen-level milk composition, apparent digestibility, andN partitioning were from 8 cows (observational units)randomly selected in each pen. Orthogonal contrastswere used to determine linear and quadratic effectsof increasing TH from 0 to 7.4, and 16.4% of dietaryDM. Although DM intake was not affected, there was atendency for CP intake to decline linearly and for NDFintake to increased linearly as TH replaced AH in thediet. Milk production declined linearly by 0.077 kg/dfor each additional percentage unit of TH in the diet,which amounted to a 3.5% decline when TH replacedAH entirely. However, no effect was observed on energycorrectedmilk production because of a compensatorylinear effect of increasing milk fat concentration withthe incorporation of TH in the diet. Total-tract NDFdigestibility tended to increase linearly by 18.5%, butno differences were detected for urinary urea-N excretionand for N utilization estimated as milk N/(fecalN + urinary N + milk N). Study 2 was an in situtrial conducted to determine the degradation kineticsof AH and TH used in study 1. In spite of differencesin degradation kinetics parameters for DM, CP, andNDF, only NDF effective ruminal degradation tendedto be greater for TH than AH. Replacing AH with THat the level typically found in intensive dairy farms ofthe semi-arid regions of Mexico had minimal effects onmilk production and N utilization.