Relationship between feed efficiency indexes and thermography, blood, and ruminal parameters in pre-weaning dairy heifers

Abstract

The objective of this study was to evaluate whether pre-weaning heifer calves divergent for residual feed intake ( RFI ) or residual feed intake and body weight gain ( RIG ) exhibit differences in thermography, blood, and ruminal parameters. Thirty-two Gyr heifer calves were enrolled in a 63-d trial and classified into 2 feed efficiency ( FE ) groups based on RFI and RIG (mean ± 0.5 SD). The groups were classified as high efficiency ( HE ) RFI (HE RFI, n = 9), HE RIG (HE RIG, n = 10), low efficiency ( LE ) RFI (LE RFI, n = 10), and LE RIG (LE RIG, n = 11). The amount of whole milk provided for each calf was calculated based on their metabolic weight at birth (42% x BW 0.75 ). The liquid diet was divided into two meals at 0700 and 1400 h. The total solid diet ( TSD ) was composed of 92% concentrate and 8% of Tifton 85 hay chopped in 5-cm lengths, as fed. Intake was measured daily. Blood concentrations of insulin, beta hydroxybutyrate, urea, and glucose, and ruminal pH, N-NH 3 , and volatile fatty acids ( VFA ) were evaluated at 14, 28, 42, 56, and 70 days of age. Thermal images of the calves were taken with an infrared camera (FLIR T420, FLIR Systems Inc., Wilsonville, OR) on d 56 (±3) at 0600 h, before the morning feeding. Total VFA concentration and propionate as % of total VFA were 24.2% and 22.2% lower in HE RFI compared to LE RFI calves, respectively. On the other hand, acetate as % of total VFA was 10.6% greater in HE RFI than LE RFI calves. Blood urea concentration tended to be greater in LE RFI than HE RFI calves. High efficiency HE RIG tended to have 6.8% greater acetate and 15.4% lower propionate as % of total VFA than LE RIG. Blood insulin concentration was greater and blood glucose tended to be greater for LE RIG than HE RIG group. Low efficiency RIG group had greater left rib, left flank, and anus surface temperature measured by infrared thermography than the HE RIG group. Differences in ruminal fermentation do not seem to be associated with pre-weaning calves efficiency, while differences in protein metabolism seem to affect RFI during this phase. Infrared thermography appears to be correlated to RIG in pre-weaning heifer calves.

Residual Feed Intake as an Efficiency Metric for Pre-Weaning Dairy Calves: What Do We Know?

“…In addition, calves grouped as low RFI were 13% more efficient than animals classified as high RFI. RFI significantly influenced dry matter intake, gas exchanges, and heat production in this study, and subsequent research [ 18 ] also showed differences in nutrient digestibility, nitrogen metabolism, and rumen function between RFI-divergent Gyr pre-weaning calves. Unlike measures of metabolic function, RFI appears to be unrelated to body measurements in the pre-weaning phase [ 16 , 17 , 20 ], indicating that selection for RFI at early ages does not affect the growth or body size of adult animals [ 21 ].…”

“…Data collected in that trial [ 19 ] were acquired using face masks. When gas exchanges were evaluated via respirometric chambers, no differences in O 2 uptake or CO 2 and heat production between low and high-efficiency calves were observed [ 17 ]. The discrepancy in these results may be related to the difference in feed intake between the low- and high-efficiency groups reported in the two studies: in the former, calves in the high-efficiency group consumed 320 g less milk + starter than low-efficiency calves, whereas the latter study reported that the difference in feed intake between the two groups was only 80 g and mainly driven by lower starter intake.…”

“…In pre-weaning dairy calves, it has been suggested that differences in feed utilization between RFI-divergent groups may be related to greater intestinal activity due to the large contribution of intestinal digestion [ 17 ]. In broad terms, nutrient digestibility is expected to be lower in the least efficient cattle because of the higher feed intake [ 30 ].…”

How Divergence for Feed Efficiency Traits Affects Body Measurements and Metabolites in Blood and Ruminal Parameters on Pre-Weaning Dairy Heifers

“…In the present study, glucose concentration was not different among RFI-divergent animals. A recent study with pre-weaning dairy heifers also did not observe differences in glucose or insulin between HE and LE RFI groups [ 18 ]. In addition, a study with growing Nellore cattle also did not observe differences in glucose concentration between RFI groups, but HE-RFI animals had a lower glucose:insulin ratio and higher insulin concentrations than LE-RFI animals [ 8 ].…”

Understanding the role of rumen epithelial host-microbe interactions in cattle feed efficiency

“…(2008) reported that low RFI (high feed efficiency) steers had higher total VFA ( P = 0.059; 96.74 vs. 55.35 mmol/L) and butyrate ( P < 0.001; 14.54 vs. 3.35 mmol/L) concentrations. However, such observations in differences of VFA concentration between low and high RFI groups were inconsistent among studies ( Hernandez-Sanabria et al, 2012 , Hernandez-Sanabria et al, 2010 ; Fitzsimons et al., 2014 ; McDonnell et al., 2016 ; Lage et al., 2020 ) which could be due to the lack of knowledge in ruminal VFA absorptions as well as the difference in diet, age and breed of animals as well as sample collection methods among studies. It is important to be aware that ruminal VFA concentration is the result of VFA production, absorption, washout, and interconversion rate of VFA ( Bedford et al., 2020 ).…”