Milk yield and composition of crossbred and indigenous Boran cows fed hay supplemented with various levels of energy

Meseret Tsegaye^1*, Adugna Tolera¹, Ajebu Nurfeta¹, Aemiro K Ashagrie² and Ermias Kebreab³

¹ Hawassa University, School of Animal and Range Sciences, Ethiopia
* kidlove99@gmail.com
² Ethiopian Institute of Agricultural Research, Addis Ababa, Ethiopia
³ Department of Animal Science, University of California, Davis 95616. USA

Abstract

The effect of supplementing various levels of energy on nutrient intake, milk yield, composition and body weight (BW) changes was evaluated. Twenty cross-bred (50 % Holstein Friesian × 50% indigenous Boran) dairy cows with an average BW of 440 ± 10.4 kg and milk yield of 8.07 ± 0.61 liter/day and twelve indigenous Boran cows with an average BW of 250 ± 1.71kg and milk yield of 2.21±0.42 liter/day were using in the experiment. The study was conducted for a total of 104 days; 14 days of adaptation to experimental feed and 90 days of data collection. The dietary treatments were: maintenance energy requirement (MER), 1.25 MER, 1.50 MER and 1.75 MER. The ME intake increased (p<0.05) with increasing levels of energy density in the diet for crossbred cows, the highest (p<0.05) being with 1.75 ME while the lowest (p<0.05) was for ME. Dry matter and intakes (except ME) were similar (p>0.05) among treatments for crossbred and Boran breeds. The average daily milk yield increased (p<0.05) with increasing levels of energy in the diet. Cross-bred cows fed on 1.75 MER and 1.50 MER diets produced 26% and 11% more milk compared with ME (maintenance energy diet), respectively. For Boran breeds the average daily milk yield for 1.5 ME and 1.75 ME was greater (p<0.05) compared with ME and 1.25 ME. Indigenous Boran cows produced 24% and 20% higher milk yields than those kept at lower energy diets (ME), respectively. The milk compositions were similar (p>0.05) among treatments for both breeds. There was weight loss for all treatments except 1.5 ME where there was weight gain but the highest (p<0.05) weight loss was for ME for crossbred and Boran cows. It can be concluded that diets containing greater amount of energy density increased milk production in both crossbred and indigenous dairy cows.

Keywords: dairy cows, indigenous, metabolizable energy, supplement, weigh change

Introduction

Ethiopia has a large livestock population that makes substantial contributions to the livelihoods of livestock keepers as well as the national economy. Over 97% of the total cattle population in the country are local breeds, and the remaining are crossbreds or exotic breeds which accounted for 2.30 and 0.31%, respectively (CSA 2021). Crossbred dairy cows are more productive than indigenous cows in the tropics (McDowell 1985). The production potential of the livestock sector has not been fully exploited in Ethiopia as the contributions achieved so far are below the potential of the animals (EIAR 2017). The low productivity level of the livestock sector in the country is due to feed shortage in terms of quantity and quality, the low genetic potential of animals, and the prevalence of animal diseases (FAO 2018). Furthermore, among these constraints, inadequate and low-quality feed resources are a limiting factor to the development of dairy production (Duguma et al 2011). The major problem in livestock feeding systems is the quality of most harvested and conserved feedstuffs because when fed alone they are unable to satisfy the maintenance needs of the livestock (Tolera 2008). In general, poor nutrition is a major inhibitor of the country's livestock sector development and is expressed in slow growth rate, low production, and reproduction performance; where poorly fed animals give a lower output of meat and milk (Tolera 2007).

Lack of information on the nutrient requirements of indigenous livestock breeds in Sub-Saharan Africa is one of the challenges limiting ration formulation principles and accuracy to improve animal productivity and enhance the performance of the sector (Thornton 2010). In most dairy farms in Ethiopia, ration formulation depends on National Research Council nutrient requirement standards (NRC 2001). The nutrient requirements of tropical animals are different from temperate breeds due to differences in genetic makeup, mature body size, growth rate, quality of feeds, climatic conditions and the efficiency of nutrient use (Paul et al 2004). Furthermore, during the early milking period dairy cows' dry matter (DM) intake (DMI) does not satisfy the increased nutrient demand, mainly because of a decrease in feed intake and appetite (Walsh et al 2011). As a result, dairy cows go into a state of negative energy balance and thus mobilize body reserves as a physiological mechanism to adapt to the energy deficiency from late gestation to early lactation (Van Knegsel et al 2007). Therefore, the objective of this study was to investigate the effect of feeding various levels of energy diets on milk yield, milk composition, and weight change of crossbred and indigenous Boran cows.

Materials and methods

Study area

The study was conducted at Holeta Agricultural Research Center dairy farm. Holeta Agricultural Research Centre is located 25 km west of Addis Ababa in the central highlands of Ethiopia at 38.5°E longitude and 9.8°N latitude and an elevation of 2,400 meters above sea level. The average annual rainfall is approximately 1,200 mm, the annual average temperature is 18°C, and the average monthly relative humidity is 60% (Demeke et al 2004).

Animal management

On average one month after calving, twenty 50% cross-bred (Holstein Friesian (HF) × indigenous Boran) dairy cows with an average body weight (BW) of 440 ± 10.41 kg and milk yield of 8.07 ± 0.61 liter/day and twelve indigenous Boran cows with an average BW of 250 ± 1.71kg and milk yield of 2.21±0.42 liter/day were used for the study. The cows were housed in individual pens. The feeding trial was conducted for a total of 104 days (14 days for adaptation to the experimental feeds and 90 days for data collection). All experimental cows were de-wormed for internal parasites with Albendazole tablets (2500 mg/cow). The experimental feeds were offered daily at 8:00 AM and 3:00 PM with ad libitum access to water. The feed refusals were collected, and milking was twice daily at 5:00 AM and 3:30 PM.

Feed preparation and treatments

The experimental feed ingredients were composed of native grass hay, cotton seed cake, wheat bran, cracked maize grain, and sugar cane molasses. The experimental design was a randomized complete block design with four treatments and five replications each for crossbred cows while indigenous Boran cows were blocked into three. The cows were blocked based on their initial BW. Twenty HF crossbred dairy cows and twelve indigenous Boran cows were assigned to the treatments in each block. The treatment diets were formulated based on NRC (2001) maintenance energy (ME) = 0.08 (BW) ^0.75. The dietary treatments were: ME requirement (MER); 1.25 MER; 1.50 MER; and 1.75 MER. The treatment diets were weighed and offered in a separate feeding trough twice a day (at 8:00 AM and 3:00 PM) throughout the study period.

Data collection

Feed offered and refusals were recorded daily throughout the experimental period. Feed intake was calculated as the difference between feed offered and refusal from each animal per day. Milk yield for indigenous Boran cows was calculated as the difference in calves’ weight before and after suckling twice a day at 5:00 AM and 10:00 PM. The crossbred dairy cows were milked by a milking machine twice a day at the same time as the indigenous Boran cows. The milk yield was recorded daily in the dairy milk database at the Holeta Agricultural Research Center dairy farm.

Analysis of feed and milk samples

Before commencing the study, experimental feed samples were analyzed for their chemical composition. The DM content was determined by overnight drying at 105 ^oC according to the methods of the Association of Official Analytical Chemists (AOAC 1990). The ash content was determined by igniting the sample in a muffles furnace at 550 ^oC for 3 hours (AOAC, 1990). Total nitrogen (N) content was determined using the Micro Kjeldahl method, and the crude protein (CP) was calculated as N×6.25. The acid detergent fiber (ADF) and neutral detergent fiber (NDF) were determined according to Van Soest and Robertson (1985). Milk samples were analyzed for total solids (TS), protein, fat, lactose and solids-non-fat (SNF) by a Milk Oscan Tester (LactoStar® Item No.3510; Funke Gerber; Berlin, Germany), using the methods described by AOAC (1990).

Statistical analysis

A two-way ANOVA test was conducted to analyze the significance of treatment diets at different energy levels. Data on DM intake, milk yield, milk composition, and average weight change was analyzed using the General Linear model (GLM) procedure of the statistical software (SPSS, version 25). Duncan's multiple range test was used for the comparison of mean differences between treatments. The model used for data analysis was:

Y_ij = μ + T_i + E_ij,

where Y = nutrient intake, milk yield, milk composition, or weight change;

μ = overall mean; T_i = treatment effect; E_ij = random error

Results

Chemical composition of the feeds used in the experiment

The chemical compositions of the feed samples are presented in Table.2. The DM content of native grass hay and wheat bran was higher, but sugar cane molasses had lower DM content than the other feed samples. The CP content was highest for cotton seed cake (CSC), and lowest for sugar cane molasses. Higher neutral detergent fiber (NDF), acid detergent fiber (ADF), and total ash were observed in native grass hay, and the lowest was in sugar cane molasses. The in-vitro organic matter digestibility (IVOMD) was higher for sugar cane molasses and lower for native grass hay.

Dry matter and nutrient intakes

The mean daily DM and different levels of ME intake of lactating crossbred and indigenous Boran dairy cows are presented in Table 3. The ME intake increased (p<0.05) with increasing levels of energy in the diet for crossbred cows, the highest (P<0.05) being with 1.75 ME while the lowest (p<0.05) was for ME. The intake of DM and nutrients were similar (p>0.05) among treatments for crossbred and Boran breeds.

Milk yield and composition

The milk yield and composition of crossbred and indigenous Boran cows were presented in Table 4. The average daily milk yield increased (p <0.05) with increasing levels of energy in the diet. Crossbred cows fed on 1.75MER diets and 1.50 MER produced 26 and 11% more milk compared with ME, respectively. For Boran breeds the average daily milk yield for 1.5 MER and 1.75 MER was greater (p<0.05) compared with 1.25 MER and 1.5 MER. Indigenous Boran dairy cows produced 20 and 24% higher milk yield for 1.5 MER and 1.75 MER, respectively than those kept at lower energy diets (ME).

Figure 1. Effects of different levels of ME diets on milk yield of cross bred dairy cows	Figure 2. Effects of different levels of ME diets on milk yield of Indigenous Boran cows

Body weight change

The body weight changes of cross-bred and indigenous cows are presented in Table 5. There was weight loss for all treatments except 1.5ME where there was weight gain but the highest (p<0.05) weight loss was for ME for crossbred and Boran cows.

Discussion

Nutrient intake of indigenous Boran and cross bred dairy cows

In this study, the supplementation of different levels of energy diets significantly affected the nutrient intake, milk yield and body weight changes of experimental indigenous Boran and crossbred dairy cows. The lowest DM intake observed for indigenous Boran cows fed the maintenance level of energy diet was in line with the findings of Gobena and Hunde (2020). The formulated concentrate treatment (1.5 ME and 1.75 ME) nutrient (energy and crude protein) intake increased by the inclusion levels of energy in feed. This was consistent with the findings of Steinshamn (2010) who showed that animals fed on diets with better energy and protein content could have better DM intake than animals fed on grass alone (Radia et al 2013). The variation in nutrient intake of cows in this study might be attributed to the differences in the supplemented energy and crude protein contents of the treatments that tended to have increased with levels of energy. The low nutrient intake recorded in cows supplemented with ME might be attributed to the higher neutral detergent fiber (NDF) content of natural grass hay and the lower proportion of energy and protein that in turn negatively associated with intake (Arelovich et al 2008). The increasing level of energy and protein intake have followed the same trend as for DM intake, i.e., greater intake was observed for cows on 1.5 ME and 1.75 ME, which might be related to the higher energy intake and crude protein content of the treatment diets.

Milk yield and composition of indigenous Boran and cross bred dairy cows

Milk yield increased as the proportion of energy and protein in the treatment diets increased for T3 and T4 were considered optimum for milk production of the crossbred dairy cows producing an average of 8 L milk/day and indigenous Boran 2 Liter/day in Ethiopia. Supporting the current study result, crossbred dairy cows have significantly higher milk yields than non-supplemented cows (Mesfin and Kitaw 2010). The feed supplementation is attributed to the amount of energy and protein increasing the energy intake (Hills et al 2015). In the current study, a greater milk yield was observed for both indigenous and cross-bred dairy cows supplemented with greater energy and protein (1.5 MER and 1.75 MER) treatment diets (Tesfaye et al 2015). In agreement to this study, the milk production of dairy cows increased as the energy and protein intake of the dairy cow increased (Moallem et al 2000). Furthermore, the benefits of energy and protein supplementation on milk yield can be particularly to its increased energy density without necessarily any increase of glucose synthesis or amino acid supply compared to the control diet (Weiss and Pinos-Rodriguez 2009). However, other possible explanations for enhanced milk response to energy supplementation are probably related to the genetic merit of dairy cows; indigenous dairy cows are low milk producers (Tadesse and Dessie 2003). In the current study, the inclusion of 1 to 1.75×ME in the treatment diets resulted in similar milk composition. The lack of statistical difference in milk composition results was likely related to the variable responses across the four treatments. Further study, will be required to test the effect of supplementation of energy and protein levels on milk composition using more energy and crude protein in the treatment diets. In this study, the difference in milk yield can be attributed to changes in the somatotropic responses to the total nutrient and energy intakes from nutritional treatments in coordinating the mobilization of body mass as a physiological mechanism to adapt to the energy deficit while sustaining milk production (Bilungi 2017).

Body weight change of indigenous Boran and cross bred dairy cows

In this study, the supplementation of different levels of energy and protein diets has a significant difference in body weight loss in ME (-31 kg) for crossbred dairy cows. Supporting current results of the average body weight loss of 120 g/day for crossbred cows was reported by Getu (2006). The other observations found that at the early stage of lactation, body weight loss ranged between 20- 90 kg for lactating crossbred cows (Muinga et al (1992). The body weight loss of the study cows goes to a state of negative energy balance and thus mobilizes body reserves as a physiological mechanism to adapt to the energy deficiency (Van Knegsel et al 2007; McArt et al 2013). In the supporting study when a cow was fed on a low-energy diet the cow utilizes reserved body fat and lost body weight (SNV 2017). Furthermore, there was no weight loss in 1.25 ME for both groups (indigenous Boran and cross-bred) of dairy cows. The deviation of weight loss result in 1.25 ME from the other three experimental treatments was not understood. The crossbred dairy cows lost more body weight than indigenous Boran cows (ME, 1.5 ME, and 1.75 ME); which is in agreement with the idea of high genetic merit cows losing more live weight and partitioning more energy and nutrients towards the udder (Hills et al 2015) to sustain milk production than low genetic merit cows (Snijders et al 2001). The study result showed that differences in the level of energy and protein intake lead to variations in milk yield and body weight loss of the experimental dairy cows.

Conclusions

• The result showed that feed intake and milk production performance of crossbred and indigenous Boran cows were improved by increasing the energy and protein levels of the diet.
  
  
• In general, diets containing 1.5 and 1.75 × ME above NRC (2001) requirement increased milk yield by 11 and 26% for crossbred and by 20 and 24% for indigenous Boran dairy cows.

Acknowledgements

This research work was funded as a whole or part of the United States Agency for International Development (USAID) Bureau for Food Security under Agreement # AID-OAA-L-15-00003 as part of Feed the Future Innovation Lab for Livestock Systems and EQUIP. The authors acknowledge Southern Agricultural Research Institute, Holleta Agricultural Research Center, EIAR, Holeta research center and animal nutrition and dairy laboratory workers for their support during animal feeding and chemical analyses.

Disclaimer

This research work was funded as a whole or part of the United States Agency for International Development (USAID) Bureau for Food Security under Agreement # AID-OAA-L-15-00003 as part of Feed the Future Innovation Lab for Livestock Systems. Additional funding was received from Bill & Melinda Gates Foundation. Any opinions, findings, conclusions, or recommendations expressed here are those of the authors alone.

Conflict of interest

We certify that there is no conflict of interest with any financial, personal, or other relationships with other people or organizations related to the material discussed in this manuscript

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