Growth performance and sorting characteristics of corn silage-alfalfa haylage diets with or without forage dilution offered to replacement Holstein dairy heifers

Abstract

Gravid heifers consuming high-quality forage diets are susceptible to excessive weight gains and overconditioning. One approach for controlling this problem is to dilute diets with low-energy forages, such as straw, that reduce the caloric density and dry matter intake (DMI) of that diet by heifers. These diluting agents are often sortable by dairy heifers, but previous visual evidence has suggested that eastern gamagrass haylage may be a nonsortable alternative. Our objectives were (1) to compare the growth performance of dairy heifers offered a high-quality forage diet (control) with diets containing 1 of 3 diluting agents [eastern gamagrass haylage (EGH), chopped wheat straw (WS), or chopped corn fodder (CF)]; and (2) evaluate sorting behaviors of heifers offered these forage diets. Holstein heifers (n=128) were stratified (32 heifers/block) on the basis of initial body weight (heavy, 560 ± 27.7 kg; medium-heavy, 481 ± 17.7 kg; medium-light, 441 ± 22.0 kg; and light, 399 ± 14.4 kg), and then assigned to 1 of 16 identical research pens (4 pens/block; 8 heifers/pen), where each of the 4 research diets were assigned to 1 pen within each block. Diets were offered in a 118-d feeding trial with heifers crowded to 133% of capacity at the feed bunk. Inclusion of low-energy forages was effective in reducing both diet energy density and DMI. Concentrations of physically effective fiber (pef) particles did not change during the 24-h period following feeding for either the control or EGH diets; however, this response for pef particles masked the competing (and cancelling) responses for individual large and medium particles, which heifers sorted with discrimination and preference, respectively. Sorting against pef particles was detected for WS, and much more severely for the CF diet. Sorting of forage particles by heifers could not be related to heifer performance. Compared with control (1.16 kg/d), average daily gains (ADG) were reduced by dilution in all cases, but were virtually identical between EGH (0.98 kg/d) and CF (0.97 kg/d), which exhibited no sorting and extensive sorting of pef, respectively. Furthermore, ADG for WS was approximately 0.2 kg/d less than EGH or CF, despite exhibiting sorting characteristics intermediate between EGH and CF. Diets diluted with low-energy forages were formulated to be isonitrogenous and isocaloric; within that context, WS was most effective in reducing DMI and maintaining ADG within typical recommendations for Holstein heifers.

Comparison of feeding diets diluted with sorghum-sudangrass silage or low-quality grass on nutrient intake and digestibility and growth performance of Holstein dairy heifers

“…Digestibilities of DM, OM, NDF, and apparent N were determined on a whole-pen basis as 100 − (fecal nutrient output/nutrient intake × 100). Similar procedures have been used to assess total-tract digestibility of diets within individual lactating cows (Lee and Hristov, 2013) and diets on a whole-pen basis for Holstein heifers (Coblentz et al, 2015). All calculations of nutrient digestibility were based on the DMI and orts collected during wk 5 and 10 for each pen.…”

“…Feed particles were separated into 4 fractions: large (>19 mm), medium (<19 and >8 mm), short (<8 and >4 mm), and fine (<4 mm; Heinrichs, 2013). Sorting factors were calculated as the proportion of each particle fraction in the feed bunk divided by the proportion in the original TMR diet (Coblentz et al, 2015) because it was impractical to weigh, mix, and sample the TMR remaining in the feed bunk, as is often done for individual animal feeding studies. Therefore, values equal to 1.0 indicate no sorting, whereas values >1.0 indicate that particles were less desirable and sorted against and values <1.0 indicate that particles were preferred by heifers.…”

“…Aydin et al (1999) and Miron et al (2007) also reported that cows consumed less DM when offered diets in which sorghum silage replaced corn silage. Use of higher fiber forages in several other studies has also led to reduced ad libitum intake and controlled growth (Greter et al, 2008;Coblentz et al, 2015;Su et al, 2017). These included the use of warm season perennials (eastern gamagrass), straw, corn stover, or alfalfa stemlage and demonstrate that various forages can be used for this purpose in dairy heifer diets.…”

“…In circumstances where producers have high-quality forages (typically for lactating cows) without a source of lowto moderate-energy forage, it can be difficult to balance rations without excess energy intake. Use of a significant proportion of corn silage or other high-quality forage with low NDF concentrations can cause issues with excess feed and energy intake and subsequent weight gain (Coblentz et al, 2015). Overconditioning before lactation can result in negative effects on mammary development and subsequent first-lactation performance as cows (Hoffman et al, 1996;Radcliff et al, 2000).…”

“…Overconditioning before lactation can result in negative effects on mammary development and subsequent first-lactation performance as cows (Hoffman et al, 1996;Radcliff et al, 2000). Several studies have evaluated the use of forages with low nutritive value (straw, corn stover, eastern gamagrass) to dilute the energy and increase fiber content, causing lower ad libitum intakes and daily gains in the ideal range of 0.8 to 1 kg/d (Coblentz et al, 2012(Coblentz et al, , 2015. However, no studies have evaluated sorghums as an option to dilute diet energy content.…”