Effects of Parity and Supply of Rumen-Degraded and Undegraded Protein on Production and Nitrogen Balance in Holsteins

Abstract

Eight Holstein cows (4 primiparous and 4 multiparous) were used in a replicated 4 x 4 Latin square design to determine milk production response and N balance when diets had no NRC-predicted excess of rumen-undegradable protein (RUP) or rumen-degradable protein (RDP), 10% RUP excess, 10% RDP excess, or 10% excess of both RUP and RDP. Diets were fed as a total mixed ration with (dry matter basis) 25% alfalfa silage, 25% corn silage, 19 to 21% corn grain, and varying proportions of solvent soybean meal and expeller soybean meal as primary sources of supplemental RDP and RUP, respectively. Milk yield and dry matter intake (DMI) were recorded daily, and total collection of feces and urine was completed in the last 3 d of each 21-d period. Dietary crude protein averaged 17.5 and 18.5% for the recommended and excess RDP diets, respectively, and 17.3 and 18.4% for the recommended and excess RUP diets, respectively. When cows were fed excess RUP diets in the form of expeller soybean meal, DMI and milk production increased, but the opposite was true when the diets contained excess RDP in the form of solvent soybean meal. Milk composition was not affected by RDP, RUP, or by parity, and there were no parity x RDP interactions for any of the measurements. However, apparent digestibility of neutral detergent fiber, dry matter, and N increased in multiparous cows but not in primiparous cows because of excess RUP. The increase in the yield of milk N with excess RUP was not influenced by parity, but multiparous cows retained more of the additional N apparently absorbed, whereas primiparous cows excreted the additional apparently absorbed N in the urine. Overall, the difference in urinary N due to parity (70 g/d) was about 4 times greater than the impact of dietary treatments (17 g/d). Our results suggest that multiparous cows have either a much larger urea pool or a greater demand to restore body protein mobilized earlier in lactation compared with primiparous cows. Reduction in urinary N excretion in commercial dairy herds could be obtained by separately balancing rations for first and later lactations.

Responses of milk urea nitrogen content to dietary crude protein level and degradability in lactatingHolsteindairy cows

“…The MUN values were significantly affected by dietary treatments (P < 0.01), with the lowest values in cows fed diet A, followed by diets B and C, and the highest in cows fed diet D. The MUN values increased with CP levels. The observation was consistent with some studies (Davidson et al, 2003;Groff and Wu, 2005;Promkot and Wanapat, 2005), while Flis and Wattiaux (2005) found that a 1% change in the dietary protein level did not cause a significant change in the MUN content.…”

Nitrogen and Phosphorus Utilisation and Excretion in Dairy Buffalo Intensive Breeding

“…Assuming a volatilisation loss of 28% (Xiccato et al, 2005), 62.6 kg N are present in the manure management system. The value of 62.6 kg annual N excretion for buffaloes is substantially less than the value of around 85 kg reported for dairy cows (Flis and Wattiaux, 2005;Xiccato et al, 2005).…”

Nitrogen efficiency of dairy cows as affected by diet and milk yield

“…Primiparous cows use some of their energy intake for growth (McDonald et al, 2002) and do not retain as much of additional nitrogen absorbed as multiparous cows do, resulting in more nitrogen excreted in the urine in primiparous cows when additional nitrogen is absorbed (Flis and Wattiaux, 2005). This suggests that primiparous cows have a smaller urea pool or a smaller demand to restore body protein mobilised earlier in lactation compared to multiparous cows (Flis and Wattiaux, 2005). In the model relating animal and feed factors to nitrogen efficiency by the dairy cows in this study, variation among cows, as a percentage of the total variation, in regard to nitrogen efficiency, were smaller for multiparous than for primiparous cows.…”