Effect of post-weaning residual feed intake classification on grazed grass intake and performance in pregnant beef heifers

Abstract

K. 2015. Effect of post-weaning residual feed intake classification on grazed grass intake and performance in pregnant beef heifers. Can. J. Anim. Sci. 95: 369Á381. There is limited knowledge of how cattle tested for feed efficiency under drylot conditions perform when they graze on summer pasture. Residual feed intake adjusted for end of test backfat thickness (RFI fat ) was determined on 171 beef crossbred heifers under drylot conditions over 2 yr using an automated system. Upon completion of the test, the 10 lowest and 10 highest RFI fat ((0.5490.17 vs. 0.5890.15 kg DM d (1 ) heifers in 2012, and the 14 lowest and 14 highest RFI fat ( (0.4790.16 vs. 0.5390.19 kg DM d (1 ) heifers in 2013 were selected and placed on meadow bromegrass pasture to investigate the effect of RFI fat ranking on their grass intake and performance on the pasture. The pasture adaptation period (8 d in 2012 and 19 d in 2013) was followed by a pasture feed intake experiment during which heifers were dosed twice daily (0815 and 1415) with 500 g of C 32 -labeled feed pellet for 13 d (day 0 to 12) and fecal sampled twice daily (0815 and 1415) from day 8 to 12. Forage DM intake on pasture for each heifer was determined using the double alkane (C 31 /C 32 ) methodology. High and low RFI fat heifers were similar in body weight (BW), backfat and rump fat thickness, and average daily gain (ADG) during the grazing trial period, except backfat thickness at the end of test period. However, low RFI fat heifers consumed 5.3% less forage when expressed as kg DM d(1 (8.2090.08 vs. 8.6690.09, PB0.001) and 5.1% less when expressed as a percentage of body weight (1.8690.02 vs. 1.969 0.02% of BW, PB0.001) compared with high RFI fat heifers. RFI fat measured under drylot conditions in growing heifers was positively correlated to grazed RFI fat determined in pregnant heifers (r p 00.30, P 00.04). These results suggest that beef heifers classified as low RFI fat during the post-weaning drylot period had lower dry matter intake as heifers in their first pregnancy grazing tame pasture, with no negative impact on their body weight, back-fat thickness, and ADG compared with their high RFI fat herdmates.Key words: Beef heifer, residual feed intake, grazed forage intake, n-alkanes, productivity Manafiazar, G., Basarab, J. A., Baron, V. S., McKeown, L., Doce, R. R., Swift, M., Undi, M., Wittenberg, K. et Ominski, K. 2015. Les effets de la classification de la prise alimentaire re´siduelle apre`s le sevrage sur la consommation du foin brouteé t la performance chez les ge´nisses a`boeuf en gestation. Can. J. Anim. Sci. 95: 369Á381. Les connaissances sont limite´es sur la performance des vaches vis-a`-vis l'efficience alimentaire dans les parcs d'e´levage lorsqu'elles broutent en paˆturage d'e´te´. La prise alimentaire re´siduelle ajuste´e pour l'e´paisseur du gras dorsal a`la fin de l'e´tude (RFI fat ) a e´te´de´termine´e durant une pe´riode de deux ans sur 171 ge´nisses a`boeuf croise´es loge´es dans les parcs d'e´levage et nourries par syste`me automatise´. À ...

Invited review: Improving feed efficiency of beef cattle – the current state of the art and future challenges

“…Similarly, Morris et al (2014) reported no difference in herbage intake in grazing lactating beef heifers from highand low-RFI selection lines. In contrast, Manafiazar et al (2015) reported that heifers ranked as low-RFI in an outdoor drylot offered a barley silage-based diet had a lower intake of grazed herbage when subsequently measured as pregnant replacement heifers. Reasons for the discrepancies in DMI between the confined and grazing dietary phases in the majority of the aforementioned studies may be attributed to: (i) the re-ranking per se of animals for RFI over time (maturity); (ii) differences in diet type and thus, associated intake and digestion characteristics; (iii), changes in the physiological state of the animals and, finally, and perhaps most importantly (iv) the inherent difficulty in accurately quantifying herbage intake in grazing cattle (Lawrence et al, 2012).…”

Effect of divergence in phenotypic residual feed intake on methane emissions, ruminal fermentation, and apparent whole-tract digestibility of beef heifers across three contrasting diets1

“…Although RFI is repeatable across different stages of the production cycle when animals are offered the same diet (Kelly et al, 2010b), there is limited information on whether animals rank similarly for RFI, or, indeed, its component traits across diets differing in energy density and chemical composition. A recent study from Manafiazar et al (2015) showed that beef heifers ranked as low RFI under drylot conditions, when offered a barley silage and steam-rolled barley TMR, also consumed 5.3% less forage than high-RFI heifers in a follow-up experiment when meadow bromegrass pasture was offered. In contrast, Meyer et al (2008) observed no difference in grazed forage intake between beef cattle of known divergent RFI classification, although these authors did acknowledge that the methodology used to estimate pasture DMI may have been a limiting factor in that study.…”

Optimizing feed intake recording and feed efficiency estimation to increase the rate of genetic gain for feed efficiency in beef cattle

“…The dataset also had final backfat thickness, and diet ingredient composition and dry matter (DM; %) and metabolizable energy (ME; MJ kg −1 DM) content. Parts of these data were used previously in numerous publications (e.g., Basarab et al 2003Basarab et al , 2011Manafiazar et al 2015). The dataset consisted of 387 492 daily feed intakes from 2 066 bulls, 1 011 replacement heifers, and 2 078 feeder heifers, and steers making a total of 5 155 animals in 85 contemporary groups (CGs).…”

“…After this data editing, a total of 4842 animals (1917 bulls in 42 CG; 1972 feeders in 27 CG; and 953 replacement heifers in 16 CG) remained for analysis. Diet compositions and details of feed test procedures were previously described by Basarab et al (2003Basarab et al ( , 2011 and Manafiazar et al (2015). In short, each animal was tagged with a half-duplex radio frequency identification (RFID) tag, and daily individual feed intake data were recorded by the GrowSafe system (GrowSafe Systems Inc., Airdrie, AB, Canada).…”

“…These practice removed some of the animals resulting in 4672 animals in the analysis (1750 bulls, 960 replacement heifers, and 1962 feeders). The details of growth curve modeling and RFI fat calculation have been previously described by Basarab et al (2003Basarab et al ( , 2011 and Manafiazar et al (2015). In summary, daily feed intakes for each animal were averaged and converted to DMI using the DM% of the diet within CG.…”