Journal of the NACAA
ISSN 2158-9429
Volume 7, Issue 2 - December, 2014

Does Hay Sample Analysis Reveal Forage Management Practices by Producers?

INTRODUCTION

Abbreviations: LA, Louisiana, MS, Mississippi, N, nitrogen, NRC, National Resarch Council, CP, crude protein, TDN, total digestible nutrients, ADF, acid detergent fiber, NDF, neutral detergent fiber

Forage systems are the backbone of livestock production in the USA. The Gulf coast region potentially can produce forages year-round through overseeding cool season annual grasses and legumes into warm-season perennial grass pastures or double cropping of annual forage crops. Because of a long summer growing season and a relatively short winter, Louisiana forage production depends heavily on warm-season grasses and annual type cool-season grasses and legumes as winter season options. Among those grasses, Italian ryegrass has provided a forage option with high digestibility from December through March (Redfearn et al., 2002).  Statewide cultivar evaluations reported that four to five cuts of annual ryegrass during the growing season could produce near 4.5 tons/acre (Alison, et al., 2011).

There has been tremendous effort on the release of new forage cultivars and significant improvement in digestibility, protein, or tolerance to environmental stress and disease (Casler and Vogel, 1999). Since the release of ‘Coastal’ bermudagrass in 1943, numerous bermudagrass cultivars have been successfully released, targeting higher yield, higher feed value, or vigor (Undersander et al., 1988; Corriher and Redmon. 2009; Hancock et al., 2010). 

Besides improved genetic potential through breeding programs, research on production management practices designed to improve forage quality have been conducted with different N fertilizer sources or several different application rates.  Studies found a positive response of bermudagrass quality to applied N fertilizer (Johnson et al., 2001; Evers, 2002; Evers, 2008). Although responses to N fertilizer among the warm-season grasses differed, overall responses, especially N content in bermudagrass tissue, responded in a linear pattern (Johnson et al., 2001). In the case of ryegrass, control of cutting height and N fertilizer application improved digestibility of Italian ryegrass (Binnie et al., 1974). Fertilization affected protein and digestibility more than controlling cutting height.    

An effort attempting to interpret potential forage intake using CP and TDN values was made with warm-season grasses (Moore et al., 1999a; Moore et al., 1999b). Generally warm-season perennial grass quality is not adequate enough to meet the nutrient requirements of fast growing beef heifers (Bos taurus).  The NRC (1984) proposed CP and TDN requirements of 800 lb BW (body weight) heifer for 7 and 54%, respectively without gain. Moore et al. (1999a) demonstrated some associate effect of TDN and CP contents determining supplement effect on voluntary forage intake. The TDN:CP ratio of 7:1 was proposed as a bench mark for intake improvement potential by supplementation. Most warm-season grass hay contained barely enough CP and TDN to meet maintenance energy requirements.  Arthington and Brown (2005) compared CP concentration changes in bahiagrass (Paspalum notatum) and bermudagrass using 4 and 10 wk regrowth materials.  At the younger growth stage, the CP in bermudagrass was higher than that in bahiagrass (P<0.05), but this kind of difference decreased as the maturity advanced, demonstrating potential quality loss due to delayed harvest.  

This study was conducted to review a decade of producers’ sample analysis results and determine whether yearly trends in forage quality may be reflective of some past management practices and ultimately indicate future direction of forage management.       

Producers’ Sample Processing, Analysis, and Statistical Analysis

This review included CP and TDN in hay samples of bermudagrass, warm-season grass mixtures, Italian ryegrass, and cool-season grass mixture analyzed from 1999 to 2011.  The total number of hay samples included in this study varied by year, but ranged from 450 to 673. Because of two massive hurricane events in 2005, the 2004 and 2005 analysis data were only partially recoverable. Those dataset were not included in this study. 

Hay samples from producers were weighed and dried at 55 ^OC for 48-h to determine the DM concentrations. Dried samples were ground to 2-mm particle size using a Thomas Wiley mill (Model 4, Thomas Scientific, Swedesboro, NJ) and reground to 1-mm particle size with a cyclone tech mill.  Approximately 2-g of sub-sample was dried at 105^OC for 3 hr to calibrate dry matter content. Samples were scanned with near infrared spectroscopy (Model 6500, Perstorp Analytical, Helsingborg, Sweden) to determine ADF, NDF, CP, and TDN using a locally developed equation. Samples recognized as outliers through scanning were separated and re-analyzed using wet chemistry according to Van Soest and Robertson (1980). Briefly, a 0.5-g sample with 0.1 ml of alpha-amylase (Ankom Technology Inc. Macedon, NY) was added during refluxing. Crude protein was estimated as 6.25 times the percentage of N determined using a semimicro-Kjeldahl procedure of Bremner and Breitenbeck (1983). 

Proc Mixed of SAS (2002) was used to determine yearly trends of CP and TDN in hay samples of bermudagrass, warm-season grass mixture, Italian ryegrass, and cool-season grass mixture. Tests for the linear and quadratic model with year were conducted using Type I test.

RESULTS AND DISCUSSION

Yearly Hay Sample Proportion Change

From 1999 to 2006, hay analysis was preformed at no cost to Louisiana or Mississippi producers. After 2006, a fee of $10-15 per hay sample was charged to producers. The total numbers of hay samples tested were reduced dramatically since 2006 when fees were charged for hay testing (Fig. 1A).

Figure 1. Annual hay sample submittal numbers of bermudagrass, warm-season grass mix, Italian ryegrass, and cool-season grass (A) and hay sample proportion (B).

 

Bermudagrass hay samples consistently occupied more than 40% of a total of four major hay sample categories, followed by samples of warm-season grass mixtures (Fig.1B). For the cool-season annual grasses more ryegrass samples were submitted than the mixtures, but these samples only accounted for about 20% of the total number of samples submitted.   

CP Concentration in Hay Samples

The annual means of CP in bermudagrass samples were substantially higher than those in the warm-season grass mixture (Fig. 2A), which probably reflected differences in management inputs between monoculture perennial grasses pasture and mixtures of warm-season pasture grass pasture.

Figure 2. CP (crude protein) content in bermudagrass and warm-season grass mixture hay (A), and Italian ryegrass and cool-season grass hay (B) produced in Louisiana with annual U.S. urea fertilizer price (USDA, 2011).

 

Although the yearly decreasing CP trend difference was small, the liner decrease was significant (P<0.001) for both warm-season grass categories (Table 1).

 

Table 1. Annual mean of crude protein (CP) and total digestible nutrient (TDN) in Bermudagrass (Cynodon dactylon) and warm-season grass mixture produced in Louisiana and Mississippi.

	Bermudagrass		Warm-season grass mixture		Ryegrass		Cool-season grass
Component	CP	TDN	CP	TDN	CP	TDN	CP	TDN
Year	***	***	**	***	**	**	**	**
Linear	***	*	***	NSa	NS	NS	NS	NS
Quadratic	NS	NS	NS	NS	*	*	NS	***

^aNS, not significant at P = 0.05; *Significant at the 0.05 probability level;** Significant at the 0.01 probability level; ***Significant at the 0.001 probability level.

 

Beginning in 2002, N fertilizer price increased dramatically and remained high until 2011 (Fig. 2A and B). The lack of sensitiveness of CP concentration in hay samples in comparison to the soaring N fertilizer price may indicate that the impact of high inorganic N fertilizer price on hay quality may have been buffered by the enhanced utilization of alternative  lower-cost organic fertilizers such as  poultry litter.. As reported in Evers (2002) and Evers (2008), CP is one of the most sensitive nutrients in bermudagrass affected by the amounts of applied N through  poultry litter. The mean CP concentration in Italian ryegrass and cool-season grass mixtures ranged from 10 to 15% DM (Fig. 2B), which was higher than those in bermudagrass or warm-season grass mixture hay by 2 to 4 percentage units. The mean CP content of both cool-season grass categories varied over time, however no significant increases or decreases were detected.      

TDN Concentration in Hay Samples

TDN in bermudagrass hay was consistently higher than that in warm-season grass mixture hay similar to findings shown in the annual CP trend. There was a sight linear decline (P<0.05) in TDN for bermudagrass over time, but not for the mixture .The yearly mean of TDN of bermudagrass and warm-season grass mixture average about 50 to 55% DM (Fig. 3A).

Figure 3. TDN (total digestible nutrient) content in bermudagrass and warm-season grass mixture hay (A),and  Italian ryegrass and cool-season grass hay (B) produced in Louisiana.

 

The yearly mean of TDN in Italian ryegrass and cool-season grass mixture also fluctuated as the TDN did with the warm-season grasses. The TDN in ryegrass or cool-season grass mixture was maintained higher than those in warm-season grass hays by up to 5% (Fig. 3B). The larger variation in TDN content across years for the cool-season grass likely indicated greater impacts of production and storage management on hay nutrient content in cool-season grass hay than in warm-season grass hay. 

TDN:CP Ratio of Hay Samples

 Because CP content of 7% and TDN of 54% were considered as minimum nutrient requirements for a full grown non-pregnant beef heifer (NRC, 1984), those nutrients’ contents were considered as a baseline in categorizing LPHT (low protein and high TDN) or HPLT (high protein and low TDN). Higher nutrients of hay samples of warm-season grass and cool-season grass were commonly categorized into low TDN hays (< 54) rather than low CP (< 7.0). Low TDN hay was more frequently found than low CP hay in tropical-type forages in Florida (Moore et al., 1999a). High fiber accumulation in tropical type forage and mature hay harvest were reasoned for this kind low hay quality. Although the proportion was different in cool-season grass hay, a higher number of hay samples with low TDN rather than low CP was also found in ryegrass and cool-season grass mixture. Producers may voluntarily delay hay harvest for higher  yield or involuntarily delay harvest in spring due to frequent rain; therefore quality would be easily sacrificed. Also, preservation of first growth ryegrass as hay in early spring is relatively more difficult than preservation of regrowth because of the longer curing time due to the denser swath of the first growth and lower temperature. 

The percentage of hays of TDN:CP ratio above 7 were  different across years(Fig. 4A).

Figure 4. Sample percentage of CP (crude protein) content is higher than 7 % and TDN (total digestible nutrient) content is higher than 54% in bermudagrass hay and warm-season grass mixture hay (A), and Italian ryegrass and cool-season grass hay (B) produced in Louisiana.

 

Except for the 2010 bermudagrass sample mean, the percentage of hay of higher than 7% CP and 54% TDN increased yearly for bermudagrass. Some of the CP decrease in bermudagrass may affect positively the TDN-CP ratio in hay samples. The number of warm-season mixture samples with a TDN:CP ratio about 7 decreased dramatically after 2003. This decrease may have been caused by delayed harvest or less intensive management. The higher cost of N fertilizers has also been a contributing factor. The TDN: CP ratio in hays of ryegrass and cool-season grass mixture fluctuated over time but no obvious trends were detected (Fig. 4B).     

CONCLUSION

The objective of analyzing this database containing a decade of forage test results from producers was to determine if these results might provide some insight into management practices used by producers.  One interesting finding was that the CP content of bermudagrass and warm-season grass mixture hays tended to decline over time, whereas the CP content of Italian ryegrass and cool-season grass mixture hays remained relatively constant.  Perhaps the rising cost of N fertilizer caused producers to either decrease the amount of N fertilizer applied to their warm-season grass hay crops or they may have delayed harvest to obtain  greater hay production. This database also clearly demonstrated that the cool-season hays had a greater TDN (about 5 percentage units) than did the warm-season grass hays. This finding reinforces the notion that cool-season forages, namely Italian ryegrass, are considered to be excellent options for forage production during the winter and spring months (Redfern et al., 2002).

ACKNOWLEDGEMENT

The authors thank Randy Walz, Jerry Simmons, Laura Zeringue, and Tara Doughty for their invaluable technical assistance and for maintaining the database. 

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