Feeding behavior, ruminal fermentation, and performance of pregnant beef cows differing in phenotypic residual feed intake offered grass silage1

Abstract

This study examined the relationship of residual feed intake (RFI) and performance with feeding behavior and ruminal fermentation variables in pregnant beef cows offered a grass silage diet. Individual grass silage DMI (dry matter digestibility = 666 g/kg) was recorded on 47 gestating (mean gestation d 166, SD = 26 d) Simmental and Simmental × Holstein-Friesian beef cows for a period of 80 d. Cow BW, BCS, skeletal measurements, ultrasonically scanned muscle and fat depth, visual muscular score, ruminal fermentation, blood metabolites, and feeding behavior were measured. Phenotypic RFI was calculated as actual DMI minus expected DMI. Expected DMI was computed for each animal by regressing DMI on conceptus-adjusted mean BW(0.75) and ADG over an 80-d period. Within breed, cows were ranked by RFI into low (efficient), medium, or high groups. Overall mean (SD) values for DMI (kg/d), RFI, initial conceptus-adjusted BW, and conceptus-adjusted ADG were 8.41 (1.09) kg/d, 0.01 (0.13) kg/d, 646 (70) kg, and -0.07 (0.32) kg, respectively. High-RFI cows ate 25% and 8% more than low- and medium-RFI cows, respectively. Live weight and ADG were not correlated (P > 0.05), and DMI was positively correlated (r = 0.80; P < 0.001) with RFI. The low- and high-RFI groups had similar (P > 0.05) BW, ADG, BCS, visual muscular scores, skeletal measurements, blood metabolites, calf birth weight, and calving difficulty scores. All ultrasonic fat and muscle depth measurements were similar (P > 0.05) for low- and high-RFI cows except for back fat thickness change, where low-RFI cows gained less fat (P < 0.05) than high-RFI cows. Low-RFI cows had greater pH and lower ammonia concentrations in ruminal fluid compared to their high-RFI contemporaries. Low-RFI cows had fewer (P < 0.001) daily feeding events, but these were of longer (P < 0.001) duration (min·feed event(-1)·d(-1)). Despite this, total daily duration of feeding was shorter (P < 0.001; min/d) for low- compared to high-RFI cows. High-RFI cows had more and a longer total duration of nonfeeding events (P < 0.001) than low-RFI cows. This study showed that compared to cows with high RFI, those with low RFI consumed less feed for similar levels of productivity, spent less time engaged in feeding-behavior-related activities, and differed in ruminal fermentation parameters. Feeding events are a significant (17%) contributory factor to variation in RFI in pregnant beef cows offered grass silage.

Growth performance, rumen fermentation, bacteria composition, and gene expressions involved in intracellular pH regulation of rumen epithelium in finishing Hu lambs differing in residual feed intake phenotype1

“…The more acidic rumen environment in the low-RFI lambs may be caused by the difference in feeding behavior. Though we did not measure the animal behavior in the current study, findings had been reported that low-RFI beef cattle chewed less (Kelly et al, 2010;Fitzsimons et al, 2014b), which means they are likely to produce less saliva to neutralize the acid in the rumen, which can result in the accumulation of acid in the rumen.…”

“…Though in both of the studies cattle were offered grass silage, which is different from the diet in our study. However, Fitzsimons et al (2014b) reported that there was no difference in acetate to propionate ratio between the low-and high-RFI pregnant beef cows when they were fed a grass silage diet. In addition, no difference was observed in acetate to propionate ratio when the beef bulls were offered a high-concentrate diet (Fitzsimons et al, 2014c).…”

Residual feed intake in dairy ewes: an evidence of intraflock variability

“…Fitzsimons et al (2014) found changes in backfat thickness, which were negative for low-RFI cows and positive for high-RFI cows. The reduction in backfat thickness in low-RFI cows suggested that these cows were mobilising more body fat to meet their nutritional requirements during pregnancy than high-RFI cows.…”

“…Currently, there are several reports arguing the interest, pertinence and possibilities of using RFI as a selection characteristic to increase feed efficiency and farm profitability in non-ruminants (Patience et al, 2015), but also in ruminants (beef: Fitzsimons et al, 2014; Gomes et al, 2012; dairy: Green et al, 2013; Potts et al, 2015; Pryce et al, 2014). There is a lack of information, however, in small ruminants, although some works have been developed mainly during the growth phase in sheep (Cockrum et al, 2013; Meyer et al, 2015; Redden et al, 2013) and the sheep industry has yet to fully investigate the potential impacts associated with selecting for RFI on carcass merit, growth traits, reproduction traits, and fleece characteristics (Cockrum et al, 2013).…”

“…Thus, there is growing interest among producers with respect to using RFI as a tool for genetic improvement, with a greater experience in swine (Patience et al, 2015) and poultry; (Aggrey and Rekaya, 2013), numerous research efforts have investigated the effectiveness of selecting for feed efficiency using RFI in beef cattle (Fitzsimons et al, 2014; Gomes et al, 2012), dairy cattle (Green et al, 2013; Potts et al, 2015; Pryce et al, 2014) or sheep (Cockrum et al, 2013; Meyer et al, 2015; Redden et al, 2013). The sheep industry, however, has yet to fully investigate the potential impacts associated with selecting for RFI on carcass merit, growth traits, reproduction traits, and fleece characteristics (Cockrum et al, 2013).…”