Effect of forage digestibility and type of concentrate on nutrient utilization by lactating dairy cattle

Abstract

SummarySix lactating dairy cows were used in a three period, part balanced changeover design experiment to investigate the effects of forage digestibility and concentrate composition on the efficiency of nutrient utilization in lactating dairy cows. Six treatments comprising three forage regimens and two concentrate types (starch υ. fibre) were examined in a 3 × 2 factorial design. The three forage regimens were high digestibility grass silage offered ad lib. (HA) or restricted to 6·5 kg dry matter/d (HR) and a low digestibility grass silage offered ad lib. (LA). Within each forage regimen animals were offered 10 kg·d of supplements containing either high-starch or high-fibre concentrations. Experimental periods lasted 28 d with a 10 d recording period, during which animal performance, ration digestibility and nitrogen and energy utilization were measured. Respiratory exchange measurements were made over a 72 h period using indirect open-circuit calorimetry. Throughout the experiment, there were no significant forage × concentrate interactions in any of the intake, production or nutrient utilization results. Milk yield was significantly influenced by forage regimen (24·1, 21·7 and 21·9 kg/d for HA, HR and LA respectively) and concentrate type (21·6 and 23·5 kg/d for high-starch and high-fibre respectively). Concentrate type also significantly influenced milk protein concentration (32·8 and 30·9 g/kg for high-starch and high-fibre respectively). Forage regimen significantly influenced the efficiency of utilization of metabolizable energy (ME) for milk production (κ1) with values of 0·62, 0·64 and 0·59 for HA, HR and LA respectively. Concentrate type had no significant effect on ME intake, heat production or κ1, although animals receiving the high-fibre concentrates synthesized proportionately 0·11 more milk energy per unit of available energy (ME intake – heat production) than those receiving the high-starch concentrates. Interpolation of the values obtained with the two high digestibility forage regimens indicated that at similar ME intakes there was a trend towards a higher κ1 with the diet based on high digestibility silage, and this was in line with the higher metabolizability of the overall diet with this silage.

Effect of dietary energy source on energy balance, production, metabolic disorders and reproduction in lactating dairy cattle

“…On the contrary, 22 out of 31 studies [8, 9, 15, 60, 61, 63-65, 67, 68, 78, 82, 99-107] reported a decrease in DMI after feeding extra lipogenic nutrients compared to 7 out of 14 studies [60,61,68,72,77,78,[108][109][110][111][112][113][114][115][116] on extra glycogenic nutrients which showed a decrease in DMI in the treatment group. In general, the negative effect of extra lipogenic sources on dry matter intake is higher when the degree of saturation of fatty acids is lower, probably because of the more pronounced negative effects of unsaturated fatty acids on rumen carbohydrate fermentation.…”

“…Eight of the 12 studies reported an increase in EB after feeding extra lipogenic nutrients [8, 9, 12, 15, 64,66,106]. In contrast to feeding extra glycogenic nutrients where 12 out of 13 studies were able to improve, not-significantly, the calculated EB [66,69,71,72,77,107,108,110,112,116,120].…”

Estimation of the maintenance energy requirements, methane emissions and nitrogen utilization efficiency of two suckler cow genotypes

“…November 2010 to January 2011 and January 2012 to March 2012), by releasing known quantities of standard CO 2 , CH 4 and N 2 (used to reduce O 2 concentration) into the chambers. All equipment, procedures, analytical methods, and calculations used in the calorimetric study were as reported by Gordon et al (1995).…”

Is there a relationship between genetic merit and enteric methane emission rate of lactating Holstein-Friesian dairy cows?

“…Animals were then housed in calorimeter chambers for 3 to 5 days with measurement of total gaseous exchange (CH 4 , CO 2 and O 2 ) taking place during the final 2 to 4 days. All equipment, sampling procedures, analytical methods and calculations used in the calorimetric studies were described by Gordon et al (1995) and calibration of the chambers by Yan et al (2000). Energy corrected milk yield (ECMY) was calculated from measured milk energy output (E l , MJ/day) divided by the calculated energy concentration (MJ/kg) of 1 kg of standard milk (concentrations of fat, protein and lactose = 40, 32 and 48 g/kg, respectively).…”