Relationships of feedlot feed efficiency, performance, and feeding behavior with metabolic rate, methane production, and energy partitioning in beef cattle1

Feed efficiency is an important trait in the future sustainability of pig production, however, the mechanisms involved are not fully elucidated. The objective of this study was to examine nutrient digestibility, organ weights, select bacterial populations, volatile fatty acids (VFA's), enzyme and intestinal nutrient transporter gene expression in a pig population divergent in feed efficiency. Male pigs (n = 75; initial BW 22.4 kg SEM 2.03 kg) were fed a standard finishing diet for 43 days before slaughter to evaluate feed intake and growth for the purpose of calculating residual feed intake (RFI). Phenotypic RFI was calculated as the residuals from a regression model regressing average daily feed intake (ADFI) on average daily gain (ADG) and midtest BW 0.60 (MBW). On day 115, 16 pigs (85 kg SEM 2.8 kg), designated as high RFI (HRFI) and low RFI (LRFI) were slaughtered and digesta was collected to calculate the coefficient of apparent ileal digestibility (CAID), total tract nutrient digestibility (CATTD), microbial populations and VFA's. Intestinal tissue was collected to examine intestinal nutrient transporter and enzyme gene expression. The LRFI pigs had lower ADFI ( P < 0.001), improved feed conversion ratio ( P < 0.001) and an improved RFI value relative to HRFI pigs (0.19 v. −0.14 SEM 0.08; P < 0.001). The LRFI pigs had an increased CAID of gross energy (GE), and an improved CATTD of GE, nitrogen and dry matter compared to HRFI pigs ( P < 0.05). The LRFI pigs had higher relative gene expression levels of fatty acid binding transporter 2 ( FABP2) ( P < 0.01), the sodium/glucose co-transporter 1 ( SGLT1) ( P < 0.05), the glucose transporter GLUT2 ( P < 0.10), and the enzyme sucrase-isomaltase (SI) ( P < 0.05) in the jejunum. The LRFI pigs had increased populations of lactobacillus spp. in the caecum compared with HRFI pigs. In colonic digesta HRFI pigs had increased acetic acid concentrations ( P < 0.05). Differences in nutrient digestibility, intestinal microbial populations and gene expression levels of intestinal nutrient transporters could contribute to the biological processes responsible for feed efficiency in pigs.

Section: Nutrient Digestibilitysupporting

confidence: 89%

Pigs that are divergent in feed efficiency, differ in intestinal enzyme and nutrient transporter gene expression, nutrient digestibility and microbial activity

Vigors

Sweeney

O’Shea

et al. 2016

“…However, selection for RFI, has been reported to lead to reductions in methane emissions (Hegarty et al, 2007). Similar results were reported by Nkrumah et al (2006), in 27 steers they estimated a phenotypic correlation of 0.44 (P < 0.05) between RFI and methane production. In dairy cattle, de Haas et al (2011) suggested that by selecting for more efficient cows, methane production could be reduced by up to 26% over a 10-year time frame.…”

Section: Methanesupporting

confidence: 73%

Genomic selection for feed efficiency in dairy cattle

Pryce

Wales

Haas

et al. 2014

Feed is a major component of variable costs associated with dairy systems and is therefore an important consideration for breeding objectives. As a result, measures of feed efficiency are becoming popular traits for genetic analyses. Already, several countries account for feed efficiency in their breeding objectives by approximating the amount of energy required for milk production, maintenance, etc. However, variation in actual feed intake is currently not captured in dairy selection objectives, although this could be possible by evaluating traits such as residual feed intake (RFI), defined as the difference between actual and predicted feed (or energy) intake. As feed intake is expensive to accurately measure on large numbers of cows, phenotypes derived from it are obvious candidates for genomic selection provided that: (1) the trait is heritable; (2) the reliability of genomic predictions are acceptable to those using the breeding values; and (3) if breeding values are estimated for heifers, rather than cows then the heifer and cow traits need to be correlated. The accuracy of genomic prediction of dry matter intake (DMI) and RFI has been estimated to be around 0.4 in beef and dairy cattle studies. There are opportunities to increase the accuracy of prediction, for example, pooling data from three research herds (in Australia and Europe) has been shown to increase the accuracy of genomic prediction of DMI from 0.33 within country to 0.35 using a three-country reference population. Before including RFI as a selection objective, genetic correlations with other traits need to be estimated. Weak unfavourable genetic correlations between RFI and fertility have been published. This could be because RFI is mathematically similar to the calculation of energy balance and failure to account for mobilisation of body reserves correctly may result in selection for a trait that is similar to selecting for reduced (or negative) energy balance. So, if RFI is to become a selection objective, then including it in an overall multi-trait selection index where the breeding objective is net profit is sensible, as this would allow genetic correlations with other traits to be properly accounted for. If genetic parameters are accurately estimated then RFI is a logical breeding objective. If there is uncertainty in these, then DMI may be preferable.

“…These results demonstrated that in comparison with low genetic merit cows, high genetic merit cows had a lower enteric CH 4 emission per kg of DM intake and milk yield, and lower CH 4 -E outputs as a proportion of GE intake. Similar results have also been reported with beef cattle, namely that increasing production efficiency reduces daily enteric CH 4 (L/kg 0.75 ) production rate (Nkrumah et al, 2006) or CH 4 CH 4 = methane emission; PIN = profit index; PLI = profitable lifetime index; CH 4 -E = methane energy output; DM = dry matter; OM = organic matter; GE = gross energy; ME = metabolisable energy; ECMY = energy corrected milk yield. a,b,c Within a row, means without a common superscript letter differ significantly (P<0.05).…”

Section: Discussionsupporting

confidence: 80%

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

Dong

Yan

Ferris

et al. 2015

The present study was undertaken to examine the effect of cow genetic merit on enteric methane (CH 4 ) emission rate. The study used a data set from 32 respiration calorimeter studies undertaken at this Institute between 1992 and 2010, with all studies involving lactating Holstein-Friesian dairy cows. Cow genetic merit was defined as either profit index (PIN) or profitable lifetime index (PLI), with these two United Kingdom genetic indexes expressing the expected improvement in profit associated with an individual cow, compared with the population average. While PIN is based solely on milk production, PLI includes milk production and a number of other functional traits including health, fertility and longevity. The data set had a large range in PIN (n = 736 records, −£30 to +£63) and PLI (n = 548 records, −£131 to +£184), days in milk (18 to 354), energy corrected milk yield (16.0 to 45.6 kg/day) and CH 4 emission (138 to 598 g/day). The effect of cow genetic merit (PIN or PLI) was evaluated using ANOVA and linear mixed modelling techniques after removing the effects of a number of animal and diet factors. The ANOVA was undertaken by dividing each data set of PIN and PLI into three sub-groups (PIN: <£3, £3 to £15 and >£15, PLI: <£23, £23 to £67 and >£67) with these being categorised as low, medium and high genetic merit. Within the PIN and PLI data sets there was no significant differences among the three sub-groups in terms of CH 4 emission per kg feed intake or per kg energy corrected milk yield, or CH 4 energy (CH 4 -E) output as a proportion of energy intake. Linear regression using the whole PIN and PLI data sets also demonstrated that there was no significant relationship between either PIN or PLI, and CH 4 emission per kg of feed intake or CH 4 -E output as a proportion of energy intake. These results indicate that cow genetic merit (PIN or PLI) has little effect on enteric CH 4 emissions as a proportion of feed intake. Instead enteric CH 4 production may mainly relate to total feed intake and dietary nutrient composition.