Biological mechanisms related to differences in residual feed intake in dairy cows

Abstract

Residual feed intake (RFI), defined as the difference between an animal's actual feed intake and expected feed intake over a specific period, is an inheritable character of feed conversion efficiency in dairy cows. Research has shown that a lower RFI could improve the profitability of milk production. This study explored variation in RFI by comparing the differences in body size, milk performance, feeding behavior, and serum metabolites in 29 Holstein cows in mid lactation. The cows were selected from a total of 84 animals based on their RFI following feedlot tests. Selected cows were ranked into high RFI (RFI > 1 SD above the mean, n = 14) and low RFI (RFI < 1 SD below the mean, n = 15). The low RFI cows (more efficient) consumed 1.59 kg/day less dry matter than the high RFI group ( P < 0.01), while they produced nearly equal 4% fat-corrected milk. The milk : feed ratio was higher for the low RFI group than for the high RFI group ( P < 0.05). The levels of milk protein ( P < 0.01), total solids ( P < 0.05), and nonfat solids ( P < 0.05) were also higher for the low RFI group, whereas milk urea nitrogen was lower ( P < 0.01). The daily feeding duration was shorter for the low RFI group than for the high RFI group ( P < 0.01). No significant differences were found in levels of glucose, β-hydroxybutyrate, prolactin, insulin, IGF-1, growth hormone or ghrelin, but the level of neuropeptide Y was higher ( P < 0.01) and levels of leptin and non-esterified fatty acid ( P < 0.05) were lower for the low RFI group than for the high RFI group. There were substantial differences between cows with different RFI, which might affect the efficiency of milk protein metabolism and fat mobilization.

Eating behavior, milk production, rumination, and digestibility characteristics of high- and low-efficiency lactating cows fed a low-roughage diet

“…The moderate correlation coefficients between eating rate and visit or meal size to daily DMI in our study was in accordance with previous studies showing eating behavior of lactating cows fed a high-concentrate TMR (Azizi et al, 2009;Connor et al, 2013;Halachmi et al, 2016) and supports our hypothesis. However, Xi et al (2016) stated that the higher (by 8.1%) DMI of LEf over HEf cows originated from the greater daily eating duration of the LEf cows without a significant difference in eating rate. A possible explanation for the discrepancy between our study and that of Xi et al (2016) might be associated with differences in the management systems.…”

“…These limits for RFI and ECM/DMI values used to characterize HEf and LEf cows were chosen based on the study of Ben Shabat et al (2016). The decision to select the upper and lower 20% as HEf or LEf cows was based on previous studies (Ben Shabat et al, 2016;Xi et al, 2016). The remaining 60% in the range of RFI between 0 to 2.75 or ECM/DMI between 1.4 to 1.57 were defined as mid-efficiency (MEf) cows.…”

“…Two main methods are widely used to determine feed efficiency. The first is RFI, defined according to NRC (2001) as the difference between animal's actual DMI and predicted DMI according to FCM yield, BW, and week of lactation (Connor et al, 2013;Potts at al., 2015;Xi et al, 2016); whereas the second is ECM divided by DMI (Jewell et al, 2015;Contreras-Govea et al, 2016;Nasrollahi et al, 2017). The ECM/DMI method is limited to a comparison between cows with similar DIM and BW characteristics.…”

“…The main limit in building a breeding program for HEf dairy cows is that the efficiency trait is mostly influenced by DMI rather than by milk production (Potts et al, 2015;Xi et al, 2016). In modern, commercial dairy herds, milk production and milk composition are measured automatically and accurately for each individual cow (Weller and Ezra., 2016), but the individual measurement of DMI is still an obstacle, as the nutrition management is based on group feeding of a TMR.…”

“…Therefore, a need exists to measure eating behavior parameters that can predict individual DMI and efficiency of each cow in the herd (Halachmi et al, 2016). Recently, it was suggested that eating behavior characteristics, such as daily eating time and rate of eating, are related to DMI and feed efficiency (Connor et al, 2013;Halachmi et al, 2016;Xi et al, 2016). However, in those studies it was unclear whether daily eating time was longer in HEf than LEf cows (Xi et al, 2016) or similar in both groups (Connor et al, 2013).…”